A MANUAL OF ZOOLOGY








A
MANUAL OF ZOOLOGY
FOR THE USE OF STUDENTS
WITH A GENERAL INTRODUCTION ON THE
PRINCIPLES OF ZOOLOGY
BY
HENRY ALLEYNE NICHOLSON
M.D., D.Sc., M.A., PH.D. (GSTT.), F.RS.E., F.G.S.
PROFESSOR OF NATURAL HISTORY AND BOTANY IN UNIVERSITY COLLEGE, TORONTO;
FORMERLY LECTURER ON NATURAL HISTORY IN THE MEDICAL SCHOOL OF EDINDURGH;
VICE-PRESIDENT OF THE GEOLOGICAL SOCIETY OF EDINBURGH, ETC.
AUTHOR OF'ADVANCED TEXT-BOOK OF ZOOLOGY FOR THE USE OF SCHOOLS;''TEXT-BOOK OF GEOLOGY;'ESSAY ON THE GEOLOGY OF CUMBERLAND AND WESTMORELAND;''GiRAPTOLITES OF THE SKIDDAW SERIES,' ETC. ETC
SECOND EDITION
REVISED AND CONSIDERABLY ENLARGED
NE W YORIK:
D. APPLETON AND COMPANY,"
549 & 651 BROADWAY.
1876.








PREFACE TO SECOND EDITION.
THE call for a new issue of this work within little more
than six months after the appearance of the last, is a
very gratifying proof that, in spite of its defects, the
work supplies a recognised want, and that the Author
has to some extent succeeded in the objects aimed at.
With regard to the present edition, the Author need
only say that the entire work has been carefully revised,
and all the more striking discoveries of recent date have
been noticed, whilst some errors have been corrected.
Considerable additions have also been made, especially
in the department of Vertebrate Zoology. The Author,
however, would ask his readers to remember that the
compass of the work will not admit of the introduction
of many details, which must be sought for in other more
extensive treatises, and that only the more important
facts of Natural History should be looked for in a work
of such limited size.
Lastly, no change has been made in the plan of classification adopted in the former editions of this work, and
based essentially upon the views put forth by Professor
Huxley. It is true that this classification is a modern




vi                     PREFACE
one, and that it departs widely from older arrangements.
The Author, however, must seek his excuse for its adoption-if such be needed-in his firm belief that of all
classifications this approximates most nearly to a natural one, and that though subsequent researches may
compel its partial modification, its broad outlines will
long endure unaltered.
TORONTO, October 2, I871.
PREFACE TO FIRST EDITION OF PART I.
IN bringing out the present work, the Author has been mainly
guided by the recollection of his own difficulties as a student,
and by the belief that he is supplying a distinct want. Many
excellent and original works on Natural History are extant,
but they mostly labour under disadvantages which more or less
disqualify them as text-books for students. So vast, for instance, have been the additions to our Zoological knowledge
within the last few years, that no work on Natural History,
except the most recent ones, represents adequately the present
state of the Science. Under this inevitable disqualification all
the older Manuals labour. Other works, again, of the most
profound research, are unsuitable for ordinary students from
their bulk, cost, and, more than all, from their very profundity.
The Author's aim, therefore, has simply been to present to
the ordinary student those leading facts in Natural History, the
knowledge of which is essential, but which lie scattered through
the pages of other larger and more costly works, inaccessible
to those who merely desire to learn the outlines of the Science.
In carrying out this object, it is unnecessary for the Author to
remark that he does not lay any claim to originality. He
trusts, however, that he has succeeded in laying before his




PREFACE.                     vii
readers, not a mere mass of undigested facts, but something
like an orderly and systematic review of the main points required to be known by the student. The Author is conscious
of many imperfections in his plan, and also in the execution of
his plan. The subject, however, is so extensive, and so constantly changing, that he can reasonably claim some indulgence,
if the brief leisure-time of a busy life has not enabled him in
every respect to keep abreast of the latest discoveries. Such
defects as there may be, are, it is hoped, of such a nature as
not to diminish the value of the work for ordinary students.
Amongst the sources upon which the Author has mainly
drawn, it is, perhaps, invidious to mention one more than
another.  He feels, however, bound to acknowledge with
gratitude the very great assistance which he has derived from
the various works of Professor Huxley.
EDINBURGH, November 2, 1869.
PREFACE TO FIRST COMPLETE EDITION.
IN issuing the first part of the present work in a second edition,
and in bringing out the second part, the Author has little to
add to what he has already said.
The chief point upon which it may be desirable to say a few
words is, as to the object aimed at in the Introductory portion
of the work. The Introduction is intended to exhibit to the
student, in as brief a form as possible, the leading principles
of Zoological Science. These principles are of the highest
importance, and no adequate knowledge of Zoology can be
attained without their full comprehension. At the same time,
the principles in question depend, in many cases, upon data
which are only evolved during the systematic study of the subject. For this reason, it is not to be expected that the student




Viii                  PREFACE.
should find himself fully able to comprehend the Introductory
portion of the work, whilst still standing at the threshold of
the subject. Whilst the student, therefore, will do well to
glance over the Introduction before commencing the study
of the systematic portion of the work, he must be prepared to
find many points which he can only fully grasp after he has
attained a knowledge of the leading modifications of structure
exhibited in the Animal Kingdom. The Author has only to
add that the first part of the work (on the Invertebrate Animals) has been carefully revised, and, as far as possible,
brought up to the present level of the Science; whilst the
illustrations, with very few exceptions, have been drawn upon
the wood by himself
EDINBURGH, December x, 187o.




CONTENT S.
PART I.-INVERTEBRATE ANIMALS.
GENERAL INTRODUCTION.
PA G
Definition of Biology and Zoology-Differences between organised
and unorganised bodies-Nature of life-Vital force-Differences between animals and plants-Morphology and physiology
-Differences between different animals-Specialisation of functions-Morphological type-Von Baer's law of developmentHomology, analogy, and homomorphism-Correlation of growth
-Classification-Definition of species-Impossibility of a linear
classification-Reproduction-Sexual reproduction - Non-sexual
reproduction-Gemmation and fission-Reproduction by internal
gemmation-Alternation of generations-Parthenogenesis-Development, transformation, and metamorphosis - Spontaneous
generation-Origin of species-Distribution, geographical and
geological,........                         I-43
CHAPTER I.
General characters of the Protozoa-Classification of the ProtozoaGregarinidae-Psorospermi,...                 44-48
CHAPTER II.
General characters of the Rhizopoda-Monera-Amcebea,..  48-52
CHAPTER  III.
Foraminifera-Classification of the Foraminifera-Bathybius-Coccoliths, Coccospheres —Affinities of the Foraminifera-Distribution
of Foraminifera in space-Distribution of Foraminifera in time, 53-6o
CHAPTER IV.
Radiolaria-Acanthometrae-Polycystina-Thalassicollida,  -  61-63
CHAPTER V.
Sponges-Nature of Sponges-Classification of Spongida-Distribu.
tion of Sponges in space and in time-Affinities of Sponges,   63-70




X                         CONTENTS.
CHAPTER VI.
Infusoriaw-Order Ciliata- Suctoria- Flagellata-Noctiluca - Phosphorescence of the Sea,.70-77
CHAPTER VII.
General characters of the Coelenterata-Divisions of the Coelenterata
-Hydrozoa —General terminology of the Hydrozoa,..  78-82
CHAPTER  VIII.
Divisions of the Hydrozoa-Sub-class Hydroida-Order HydridaOrder Corynida-Reproduction of Hydroida-Sertularida-Campanularida,..... 83-93
CHAPTER IX.
Siphonophora or Oceanic Hydrozoa-Calycophoride —Divisions of
Calycophoridoe-Physophoridae-Divisions of Physophoridoe, 93-100oo
CHAPTER X.
Discophora-Structure of Medusidae-Value of Medusidae as an order
of Hydrozoa,.... Ioo-Io3
CHAPTER XI.
Lucernarida-Steganophthalmate Medusae-Lucernariadae-Pelagidae
-Rhizostomidae - Reproduction in Rhizostomidme -- Sub-class
Graptolitide —Definition of the Sub-class-Structure of Graptolites,..                      I4- 12
CHAPTER XII.
Distribution of Hydrozoa in space-Distribution of Hydrozoa in time
-Oldhamia-Corynida-Sertularida-Graptolites,.. I2-I14
CHAPTER  XIII.
General characters of the Actinozoa-Zoantharia MalacodermataActinidae-Ilyanthidae-Zoanthidce- Zoantharia SclerobasicaSclerobasic and Sclerodermic Corals-Antipathide —Hyalonemadae - Zoantharia  Sclerodermata  Gemmation and fission
amongst Corals,.11.  4-I25
CHAPTER XIV.
Alcyonaria-Alcyonidce -Tubiporidoe - Pennatulide - GorgonidaeRed Coral,...25-128
CHAPTER XV.
Rugosa-Distinctions between the Coralla of the different Orders of
Actinozoa,.28-130




CONTENTS.                           xi
CHAPTER XVI.
Ctenophora-General characters-Anatomy of Pleurobrachia-Divisions of Ctenophora,...               130-I34
CHAPTER XVII.
Distribution of Actinozoa in space-Coral Reefs, their structure, and
mode of origin-Distribution of Actinozoa in time-Tabular view
of the divisions of the Zoantharia Sclerodermata and Rugosa, I34-140
CHAPTER XVIII.
Annuloida-General characters of the Annuloida —General characters
of the Echinodermata-Development of the EcllinodermataDivisions of Echinodermata,...... 14-144
CHAPTER XIX.
Echinoidea-General characters-Anatomy of Echinus-Divisions of
Echinoidea,.                    I44-I 50
CHAPTER XX.
Asteroidea and Ophiuroidea-General characters of the AsteroideaDivisions of the Asteroidea-General characters of the Ophiuroidea-Families of the Ophiuroidea,.. 50-155
CHAPTER XXI.
Crinoidea, Cystoidea, and Blastoidea-General characters of Crinoidea-Of Cystoidea-Of Blastoidea,.                     I55.i60
CHAPTER XXII.
Holothuroidea-General characters-Families of Holothuroidea, 160-162
CHAPTER XXIII.
Distribution of Echinodermata in space-Distribution of Echinodermata in time-Crinoidea-Blastoidea-Cystoidea-AsteroideaOphiuroidea-Echinoidea-Holothuroidea,... 162- 65
CHAPTER XXIV.
Scolecida-General characters of the class Scolecida-EntozoaPlatyelmia-Teniada -Structure and development of the Tapeworm-Hydatids,.                                      i65-171
CHAPTER XXV.
Trematoda and Turbellaria-General characters of the TrematodaGeneral characters of the Turbellaria-Planarida-Nemer.
tida,...                                         I 71-175




xii                        CONTENTS.
CHAPTER XXVI.
Nematelmia — Acanthocephala - Gordiacea - Nematoda - Parasitic
Nematoids-Free Nematoids,..                    75-179
CHAPTER XXVII.
Rotifera-General characters of the Rotifera-Affinities of the Rotifera,.a.  179-I84
CHAPTER XXVIII.
Annulosa-General characters of the Annulosa-General characters
of the Anarthropoda-Class Gephyrea-General characters of the
class Annelida,..                  185-189
CHAPTER XXIX.
Divisions of the Annelida- Hirudinea -Oligochaeta-TubicolaErrantia-Distribution of the Annelida in time-Tabular view
of the Annelida-Class Chaetognatha,..         I89-99
CHAPTER XXX.
Arthropoda-General characters-Divisions of Arthropoda,. x99-200
CHAPTER XXXI.
Crustacea-Characters of the class Crustacea-General morphology of
Crustacea-Divisions of Crustacea,.                     200-208
CHAPTER XXXII.
Epizoa-Ichthyophthira- Rhizocephala-Cirripedia-Characters of
Cirripedia-Development-Reproduction-Divisions,.. 208-215
CHAPTER XXXIII.
Entomostraca - Lophyropoda - Ostracoda - Copepod a - Branchiopoda - Cladocera - Phyllopoda - Trilobita - Merostomata -
Xiphosura-Eurypterida,..... 2I5-223
CHAPTER XXXIV.
Malacostraca-Edriophthalmata - Loemodipoda - Amphipoda - Isopoda-Podophthalmata - Stomapoda - Decapoda - MacruraAnomura-Brachyura,.                                    223-232
CHAPTER XXXV.
Distribution of the Crustacea in space-Distribution of the Crustacca
in time,. 233-234
CHAPTER XXXVI.
Seneral characters and divisions of the Arachnida,... 235-238




CONTENTS.                          Xiii
CHAPTER XXXVII,
Divisions of the Arachnida-Podosomata-Acarina-Adelarthrosomata-Pedipalpi-Araneida,.                            238-244
CHAPTER XXXVIII.
Myriapoda-General characters of the class-Chilopoda-Chilognatha-Pauropoda-Distribution of Myriapoda in time,. 245-248
CHAPTER XXXIX.
General characters of the Insecta-Metamorphoses of Insects-Sexes
of Insects,.. 248-257
CHAPTER XL.
Divisions of the Insecta - Anoplura - Mallophaga - ThysanuraHemiptera-Orthoptera — Neuroptera-Aphaniptera-DipteraLepidoptera-Hymenoptera-Strepsiptera-Coleoptera,. 257-273
CHAPTER XLI.
General characters of the Mollusca-Digestive system-Circulatory
system.-Respiratory system-Nervous system-ReproductionShell,...274-278
CHAPTER XLII.
Molluscoida-Polyzoa-Distinctions between the Polyzoa and IHydrozoa-Polypide of the Polyzoa-Anatomy of the PolyzoaReproduction and development-Divisions of the Polyzoa,. 279-287
CHAPTER XLIII.
Tunicata- General characters-Development-Types of-Homologies
-Divisions,, 287-292
CHAPTER XLIV.
Brachiopoda - General characters - Shell-Arms —Atrial systemDivisions,.. 292-297
CHAPTER XLV.
Distribution of Molluscoida in space-Distribution of Molluscoida in
time,.,,.           297-299
CHAPTER XLVI.
General characters and divisions of the Mollusca Proper-Lamellibranchiata-General characters and anatomy-Divisions-Families of the Lamellibranchiata,.....    300-308
CHAPTER XLVII.
Encephala-Gasteropoda- General characters-Development-Shell
Cf Gasteropoda,.                                     308-312




xiv                       CONTENTS.
CHAPTER  XLVIII.
Divisions of the Gasteropoda-Prosobranchiata-OpisthobranchiataHeteropoda-Pulmonate Gasteropoda-Families of the Gasteropoda,..                                           313-319
CHAPTER XLIX.
Pteropoda-General characters-Divisions-Families,. 320-321
CHAPTER L.
Cephalopoda-General characters-Arms-Respiratory organs-Reproductive process-Shell-Divisions,..          322-327
CHAPTER LI.
Dibranchiate Cephalopods-General characters-Octopoda-Argonautidae-Octopodidae-Decapoda-Teuthidae-Sepiadse-Spirulidae-Belemnitidae-Tetrabranchiate Cephalopods-Structure of
the Pearly Nautilus-Shell of the Tetrabranchiata-NautilidaeAmmonitidoe-Families of the Cephalopoda,.. 327-335
CHAPTER LII.
Distribution of the Mollusca Proper in time,. 336-338
Tabular view of the chief subdivisions of the Invertebrata,.. 339-342
PART II. -VERTEBRATE ANIMALS.
CHAPTER LIII.
General characters of the Vertebrata-Osseous system-Digestive system - Blood - Circulation - Respiration - Nervous system -
Organs of sense-Reproduction-Divisions,.. 345-36i
CHAPTER LIV.
General characters of Fishes-Integumentary system-Osseous system
- Fins - Respiration - Circulation - Digestive system - Swimbladder-Nervous system-Olfactory organs-Reproduction, 362-375
CHAPTER LV.
Pharyngobranchii-Marsipobranchii,..  376-381
CHAPTER LVI.
Teleostei - Sub-orders - Malacopteri —Anacanthini-AcanthopteriPlectognathi-Lophobranchii,...... 38-388




CONTENTS.                           xv
CHAPTER LVII.
Ganoidei-Sub-orders- Lepidoganoidei —Placoganoidei,. 388-394
CHAPTER  LVIII.
Elasmobranchii and Dipnoi-Sub-orders of Elasmobranchii-Holocephali-Plagiostomi-Dipnoi,..          394-402
CHAPTER LIX.
Distribution of Fishes in time,....... 402-405
CHAPTER LX.
General characters of the Amphibia,..... 406408
CHAPTER LXI.
Orders of Amphibia-Ophiomorpha-Urodela-Anoura- Development of Frog-Families of Anoura-Labyrinthodontia-Distribution of Amphibia in time,...408-418
CHAPTER LXII.
General characters of Reptilia-Endoskeleton-Exoskeleton-Digestive system-Circulatory system-Respiratory system,.. 419-423
CHAPTER LXIII.
Divisions of Reptilia-Chelonia —General characters of Chelonian
Reptiles-Distribution of Chelonia in time-Ophidia -General
characters of Snakes - Sub-orders - Distribution of Ophidia in
time,..                      423-435
CHAPTER LXIV.
Lacertilia-Families of Lacertilia-Distribution of Lacertilia in time
-Crocodilia-Sub-orders of Crocodilia-Distribution of Crocodilia in time,.                                      435-445
CHAPTER LXV.
Extinct orders of Reptiles —Ichthyopterygia- Sauropterygia-Anomodontia-Pterosauria-Dinosauria,.                    445-452
CHAPTER LXVI.
General characters of the class Aves-Feathers-Vertebral columnSkull-Pectoral arch and fore-limb-Pelvic arch and hind-limb
-Digestive system- Respiratory system —Circulatory systemReproductive organs-Nervous system and organs of Sense,. 453-472
CHAPTER LXVII.
General divisions of the class Aves-Characters and families of the
order Natatores-Characters and families of Grallatores,. 472-484




xvi                       CONTENTS.
CHAPTER LXVIII.
Characters of Cursores-Characters and sections of Rasores-Gallinacei-Columbacei,.484-492
CHAPTER LXIX.
Characters and families of Scansores-Characters of Insessores-Conirostres-Dentirostres-Tenuirostres-FiSsirostres,.. 492-501
CHAPTER LXX.
Characters and Sections of Raptores-Characters of Saururae,. 501-505
CHAPTER LXXI.
Distribution of Aves in time,...505-508
CHAPTER LXXII.
General characters of the Mammalia-Skeleton-Pectoral arch and
fore-limb-Pelvic arch and hind-limb-Teeth-Dental formulaDigestive system-Circulatory system-Respiratory system-Reproductive system-Mammary glands-Nervous system-Integumentary appendages,                                   509-521
CHAPTER  LXXIII.
Classification of the Mammalia - Synopsis of the Mammmalian
orders,..522-526
CHAPTER LXXIV.
Characters of Monotremata   Characters and divisions of Marsupialia,... 527-536
CHAPTER LXXV.
Characters and families of Edentata,.. 537-542
CHAPTER LXXVI.
Characters of Sirenia-Characters and families of Cetacea,.. 542-551
CHAPTER LXXVII.
General characters of Ungulata-Perissodactyla —Artiodactyla-Ruminantia- Structuie of the stomach in Ruminants-Dentition of
Ruminants-Sections of Ruminants,.                    551-568
CHAPTER LXXVIII.
Characters of Hyracoidea-Characters of Proboscidea,. 568-572
CHAPTER LXXIX.
Characters of Carnivora-Pinnigrada-Plantigrada-Digitigrada, 573-586




CONTENTS.                           XVii
CHAPTER LXXX.
Characters of Rodentia-Families of Rodentia,.... 586-592
CHAPTER LXXXI.
Characters of Cheiroptera-Sections of Cheiroptera,... 592-595
CHAPTER LXXXII.
Characters of Insectivora - Families of Insectivora - Galeopithecid e........                                           595-598
CHAPTER LXXXIII.
Characters of Quadrumana-Sections of Quadrumana-StrepsirhinaPlatyrlhina-Catarhina,. 598-606
CHAPTER LXXIV.
Characters of Bimana,..606-607
CHAPTER LXXXV.
Distribution of Mammalia in time-Geographical succession of organic forms-Tabular view of the chief sub-divisions of the Vertebrata,.... 607-620
GLOSSARY,......                                          62I-65I
INDir,.......652-673




xviii
LIST OF ILLUSTRATIONS.
Fir.                       PAGE    FIG.                         PAGES
I. Gregarina of the Earth-         30. Diagram of Actinia,.  I5
worm,....  47    3I. Actinia rosea and Arach2. Morphology of Rhizopoda,  49          nactis albida,. 117
3. Actinophrys sol,.      52    32. Morphology of Corals,.  20
4. Morphology of Foramini-         33. Sclerodermic and Sclerofera.                   54           fidsic Corals,. 121
5. Nummulites ievigatus,     60    34. Pennatula phosphorea,.  27
6. Acanthometrina and Poly-        35. Virgularia mirabiis,. 127
cystina,...  6I    36. Pleurobrachia pileus,. 13I
7. Morphology of Radiolaria,  63    37. Morphology of Ctenophora, 132
8. Diagram of Spongilla,    65    38. Structure of Coral-reefs,. 136
9. Morphology and reproduc-        39- Morphology of Echinoidea, I45
tion of Spongida,.     66    40. Cidaris papillata,.. I46
Io. Morphology of Infusoria,   7I    4I. Larva of Echinus.  Diaii. Vaginicola, Stentor, and              gram of Echinus,.. 148
Vorticella,..      75    42. Cribella oculata,.. I5'
T2. Morphology of Iydrozoa,   84    43. Ophiura  textrata nd
13- Morphology of Corynida,   86          Ophiocoma neglecta,. I54
14. Reproductive processes of       44. Rhizoclinus Lofotensis,. I56
Hydrozoa,.        -..87    45. Comatula rosacea, larva
I5. Medusiform gonophore of               and adult,..          57
Clytia,..        88    46. Echinospheerites aurantium, 159
I6. Tubularia indivisa,      89    47.  Thyonepapillosa,.     6I
I7. Sertularia pinnata  and         48. Morphology of T&aniada,  I69
Campanularia neglecta,  91    49. Trematoda,... I72
I8. Morphology of Oceanic           50. Morphology  of  TurbelHydrozoa,..          94          laria,                  174
9. Diphyes appendicuata,      96    5I Echinorhynchusgigas,  1. 76
20. Physalia utriculus  and         52. Anguillula aceti and DoryVelella vulgaris,..  99           laimus stagnalis,.. 177
2I. Morphology of ledusidne, ioI    53. Hydatina senta and Meli22. Group of naked-eyed Med-              certa ringens,. I8I
use,  1.0..            o02    54. Diagram  of an Annulose
23. Lucernaria auricula,.  o5         animal,..          85
24. Development of Lucer-           55. Syrinx nudus,..       86
narida,..    o7    56. Diagrammatic section of
25. Generative zooid of Chry-             an Annelide,.. 187
saora,.  o8    57- Medicinal Leech,.. I90
26. Generative zooid of Rhi-        58. Serpula  contortuplicata
zostorma,   9..    o             and Spirorbis communis, I93
27. Morphology  of Grapto-          59. Nereis,..      I96
lites,.... 12    6. Errant Annelides,..  97
28. Didymograpsus V-fractus,  113
29. Transverse section of an        6i. Diagram of the Somite of
Actinozobn and Hydro-               a Crustacean,.. 203
zo0ont....     II      62. Morphology of Lobster. 205




LIST OF ILLUSTRATIONS.                          xix
63. Larva and adult of Achthe-      II4. Cleodora pyramidata and
respercarum,.    209           Cuvieria columnella,    320
64. Locomotive young of Ba-         II5. Sepiola Atlantica,.      323
anus,. 2T2   ii6. Octopus carena,.        326
65. Morphology of Cirripedia, 2I3   II7. Paper Nautilus,.       328
66. Fresh-water Entomostraca, 216   iI8. Diagram of Belemnite,      329
67. Chirocephalus diaphanus,. 2I9   II9. Pearly Nautilus,. 331
68. Morphology of Trilobites,  220   120. Diagram of the Siphuncle
69. Limuluspolypheus,. 222             and Septa in the shells of
70. Pterygotus Anglicus,. 222          various Tetrabranchiate
71. Caprella phasma,.       224          Cephalapods,.        333
72. Talitrus locusta,. 225   121. Orthoceras explorator,. 334
73. Wood-lice,.    226   122. Shells of Secondary Ceph74. Homarus vulgars.. 229               alopods,..        338
75. Spider-crab (Maza),. 23I   I23. Transverse sections of the
76. Larva (Zoea) of Crab,. 232          body of an invertebrate
77- Morphology of Arachnida, 237           and a vertebrate animal, 346
78. Pycnogonum littorale, Te-       I24. Embryology of Vertebrata, 347
tranychus telarius, and        I25. LumbarVertebraofWhale,
Hydrachna globulus,. 240           and diagram of thoracic
79. Scorpion,..    242           vertebra,.. 350
80. Theridion riparium,. 243   126. Skeleton of the Beaver,    35I
8r. Centipede,..    245   127. Pectoral LimbofChimpan82. Millipede,..      247           zee,                     353
83. Diagram of Insect,.     249   128. Pelvic Limb of Chimpan84. Organs of the Mouth in                 zee,..             354
Insects,..   251    129. Diagram  of the digestive
85. Digestive system of Beetle, 252        system of a Mammal,. 355
86. Metamorphosis  of  the          130. Blood-corpuscles of VerteMagpie Moth,.        255          b-ata,.356
87 fiean Aphis,..       259    I3I. Diagram of the Circuiat' uI
88. Cockroach (Blatta),    ~ 259           of a Mammal,.        357
89. Migratory Locust,.      26r   I32. Scales of Fishes,.       362
go. Aphis Lion,..       26I   I33. Skeleton of the Common
9I. Termites,..       262           Perch,..        364
92. Tipula oleracea,.. 265    34. Skull of the Cod,           365
93. Pontia brassica&,.   266   135. Os hyoides and branchial
94. Cossus ligniperda,.     267           arches of the Perch,. 367
95. Tenthredo grossulariee,. 268   136. Pectoral Limbs of Fishes,  368
96. Myrmica rufa,.    269    I37. Outline ofPercagranulata, 370
97. Stylops Spencii,.    271   138. Homocercal and heterocer98. Melolontha vulgaris,. 271          cal Tails,..       370
99. Cetonia aurata and Cur-         139. Diagram of the Circulation
culio sulcatus,.     272           of a Fish,      ~. 372
Ioo. Diagram of a Mollusc,. 274   I40. Diagram of the Lancelet,  377
ioi. Morphology of Polyzoa,. 282   14I. Lamprey,..    379
102. Flustra  truncata,  Val-        I42. Heart of Teleostean and
keria, and Lophoopus cry-             Ganoid Fishes,.       383
stallinus,.. 283   I43. Gymnotus electricus,        384
103. Morphology of Tunicata,  288   I44. Rhombuspunctatus,.         386
Io4. Lingula anatina,.      293   145. Ostracion cornutus,.       387
105. Terebratula vitrea,.    294   146. Polypterus and Osteolepis,  391
io6. Anatomy of Mya arenaria, 302   I47. Cephalaspis Lyelii,.. 393
Io7. Shells of Lamellibranch-         148. Coccosteus and Pterichthys, 393
iata,.         304   I49. Head of Piked Dog-fish,. 395
Io8. Odontophore of the Whelk, 309    150. Carcharias and Chimeara,  396
iog. Ampullaria canaliculata,  3IO   I5I. Raia marginata,.        398
rIo. Holostomatous  and  Si-         152. Lepidosiren annectens,     400
phonostomatous Shells,  314    I53. Spines andTeeth of PaleoIIi. Doris yohnstoni,.     3I5           zoic Elasmobranchii,    404
12. Carinaria cymbium,. 315    I54. Hyla leucotcenia,.    407
II3. Limax Sowerbyi,.      3I6    I55. Siphonops annulatus,       409




XX                 LIST OF ILLUSTRATIONS.
I56. Proteui anguinus,.. 40   Ix98. Foot of Tawny Owl, and
157. Axolotl,.... 412            Head of White Owl,. 502
158. Triton cristatus,. 413   i99. Head of Vulture,.       503
159. Skeleton of the Frog,. 414   200. Archacopteryx macrura,    504
x6o. Development of the Frog,  4I5   20o. Fore-limbs of Horse and
x6z. Footprints ofa Labyrintho-            Deer,..514
dent,.                 4I7   202. Teeth of Chimpanzee,. 5I8
162. Skull of a Serpent,.. 421   203. Ornithorhynchusparadoxus, 528
I63. Diagram of the circulation     2o4. Pelvis of Kangaroo,. 530
in Reptiles,... 422   205. Koala or Kangaroo-bear,  532
164. Skeleton of Tortoise,. 425   206. Dentition of Thylacinus
i65. Hawk's-bill Turtle,.. 427         and Hypsiprymnus,  ~  533
i66. Eye of Serpent and Head        207. Myrmecobiusfasciatus,. 536
of Viper,..   430   208. Hand of three-toed Sloth,  538
167. Naja Haje,. 432   209. Chlamyphorus truncatus,. 540
i68. Head of Ringed Snake,          2I0. Dugong,...        543
of Viper, and of Blind-       2II. Skull of Right Whale,. 545
worm,.                434   212. Diagram of Baleen-plates
i69. Iguana,.... 436            of a Whale,..      547
17o. Blind-worm,..      438   2I3. Physeter macrocephalus,   549
17I. Common Skink,         ~ 439   2I4. Delphinus delphis,.     550
I72. Head of Chameleon,. 440   2I5. Feet of Ungulata,.      552
I73. Crocodilus vulgaris,. 443   2I6. Head of Two-horned Rhini74.'Skull of Crocodilus bipor-            oceros,.              554
catus,.444   2I7. Stomach of a Sheep,    ~ 559
175. Ichthyosaurus communis,   446   2i8. Skull of hornless Sheep,. 560
176. Plesiosaurus dolichodeirus, 448   2I9. Head of the Red-deer,. 563
177. Pterodactylus brevirostris,  449   220. Head of the Koodoo,. 566
178. Quill-feather,.. 455   22I. Skull of the Indian EleI79. Skull of Spur-winged Goose, 458       phant,.               570
i8o. Pectoral arch and fore-limb    222. Skull of Deinotherium,. 572
of Penguin,... 459   223. Feet of Carnivora,.. 574
i8i. Fore-limb of Jer-falcon,. 46I   224. Phoca granlandica,.. 575
182. Hind-limb of Loon,.. 463   225. Skull of the Walrus,. 576
183. Digestive System  of the       226. Skull of Jackal,.. 583
Common Fowl,.. 465   227. Skull of Lion,..   584
I84. Lung of Goose,.     467   228. Skull of Beaver,..587
185. Foot of Cormorant and          229. Common Hamster,. 590
Beak of Goose,. 475   230. Skeleton of Fox-bat,. 593
I86. jackass Penguin,.      476   23i. Head of Vampire-bat and
187. Leg of Curlew, Head of               Fox-bat,..       594
Snipe, and Beak of Avocet, 480   232. Skull of Hedgehog,.   596
i88. Crested Heron,. 482   233. European Mole,.. 596
i89. Foot of Ostrich,and Breast-    234. Green Monkey,.       599
bone of Emeu,.. 485   235. Skulls of Orang and EuroxI9. Apteryx Australis,.     487          pean adult,..      605
191. Foot of Fowl, and Head of      236. Jaw of Dromatherium,. 609
Guinea-fowl,.. 488   237- Jaws of Phascolotherium,
192. Rock-pigeon,... 490            Triconodon, Amphithe193. Foot of Woodpecker, and               rium, and Plagiaulax,  6Io
Head of Love-bird,. 493   238. Skull of Diprotodon,      6II
194. Purple-capped Lory,. 494   239. Skeleton of Megatherium,  6I2
x95. Feet and Heads of Inses-       240. Glyptodon clavipes,.    612
sores,                 496   241. Skeleton of Megaceros Hix96. Head.of Bullfinch,.. 498          bernicus,..   64
197. Foot of Peregrine Falcon,      242. Skeleton of Mastodon,    6I5
and Head of Buzzard,. 50I   243. Skeleton of Mammoth,. 6i6




PART I.
INVERTEBRATE ANIMALS








MANUAL OF ZOOI,OGY.
GENERAL INTRODUCTION.
I. DEFINITION OF BIOLOGY AND ZOOLOGY.
NATURAL HISTORY, strictly speaking, and as the term itself
implies, should be employed to designate the study of all
natural objects indiscriminately, whether these are organic
or inorganic, endowed with life, or exhibiting none of those
incessant vicissitudes which collectively constitute vitality.
So enormous, however, have been the conquests of science
within the'last century, that Natural History, using the term
in its old sense, has of necessity been divided into several
more or less nearly related branches.
In the first place, the study of natural objects admits of
an obvious separation into two primary sections, of which the
first deals with the phenomena presented by the inorganic
world, whilst the second is occupied with the investigation of
the nature and relations of all bodies which exhibit life. The
former department concerns the geologist and mineralogist,
and secondarily the naturalist proper as well; the latter department, treating as it does of living beings, is properly
designated by the term  Biology (from.ios, life, and X7yos, a
discourse). Biology, in turn, may be split up into the sciences
of Botany and Zoology, the former dealing with plants, the
latter with animals; and it is really Zoology alone which is
nowadays understood by the term Natural History.
In determining, therefore, the limits and scope of Biology,
we are brought at the very threshold of our inquiry to the
question, What are the differences between dead and living
bodies? or rather, in the first place, what are the characteristics of an organised as compared with an unorganised body? "
* The differences between dead or inorganic bodies on the one hand,
and living or organic bodies on the other, may be taken for all practical
purposes as the same as those between unorganised and organised bodies.
It is quite true that certain living beings (Foraminifera) cannot be said to




2               MANUAL OF ZOOLOGY.
2. DIFFERENCES BETWEEN DEAD AND LIVING BODIES.
In determining this somewhat difficult point, it will be best
to examine the differences between organised and unorganised
bodies seriatim, and to compare them together systematically
under the following heads:a. Chemical Composition.-Unorganised bodies are composed
of many elements, which may be either simple or combined;
but the combinations are mostly limited to a small number of
elements (forming binary and ternary compounds), and these
are united in low combining proportions. Thus, carbonate of
lime, or common limestone, is an excellent example of an inorganic body,* being a ternary compound composed of one
atom of the metal calcium, three of oxygen, and one of carbon.
Organised bodies, on the other hand, are composed of few
chemical elements, and these are almost always combined.
Furthermore, the combinations are always complex (ternary
and quaternary compounds), and the elements enter into union
in high combining proportions. Finally, the combinations are
invariably characterised by the presence of water, and are
prone to spontaneous decomposition. Thus, the great organic
compound, albumen, is composed of I44 atoms of carbon, IIo
of hydrogen, i8 of nitrogen, 2 atoms of sulphur, and 42 of
oxygen. Iron, however, exists in the blood, very probably in
its elemental condition; and copper has been detected in the
liver of certain Mammalia, and largely in the red colouringmatter of the feathers of certain birds.
b. Arrangement of Parts. —Unorganised bodies are composed
of an aggregation of homogeneous parts (when unmixed) which
bear no definite and fixed relations to one another.
Organised bodies are composed of heterogeneous parts, the
relations of which amongst themselves are more or less definite.
c. Form. —Unorganised bodies are either of no definite shape
-when they are said to be "amorphous"-or they are crystalline, in which case they are almost invariably bounded by
plane surfaces and straight lines. Organised bodies are always
more or less definite in shape, presenting convex and concave
surfaces, and being bounded by curved lines.
be " organised" in the proper sense of the term; still organisation is in
such a vast proportion of cases the concomitant of vitality, that the purpose here in view will be fully served by assuming that all living bodies
are organised, and all dead bodies are unorganised.
* In another sense limestone may be said to be organic-namely, when
it has been produced by the operations of living beings; but this does not
affect the above definition.




DEAD AND LIVING BODIES.                   3
d. Mode of lncrease~.-When unorganised bodies increase in
size, as crystals do, the increase is produced simply by what is
called "accretion;" that is to say, by the addition of fresh
particles from the outside.
Organised bodies increase by what is often called. the "intussusception" of matter; in other words, by the reception of
matter into their interior and its assimilation there. To this
process alone can the term "growth " be properly applied.
e. Cyclical Change.-Unorganised bodies exhibit no actions
that are not purely physical or chemical, and they show no
tendency to periodical vicissitudes. Organised bodies are preeminently distinguished by the tendency which they show to
pass through spontaneous and cyclical changes.
To sum up, all bodies which are composed of an aggregation of diverse but definitely related parts, which have a definite shape, bounded by curved lines and presenting concave
and convex surfaces, which increase in size by the intussusception of foreign particles, and which pass through certain
cyclical changes, are organised; and it is with the study of
bodies such as these that Biology is concerned.
In the foregoing- t has been assumed, for the sake of simplicity, that all living bodies exhibit organisation. It is to be
remembered, however, that there are living bodies (e.g., Foraminzfera) to which the term of " organised," as above defined,
cannot be applied.  Such bodies are living, but they are not
organised. In these cases the distinction from dead matter depends wholly upon the mode of growth, and upon the presence
of vital activity as shown by the occurrence of various periodic
changes.
The grand and fundamental characters by which living
bodies are distinguished from dead bodies are these:-I. Every
living body possesses the power of taking into its interior certain foreign materials, and converting these into the substances
required to build up fresh tissue or repair waste. By'this
power of " assimilation," as it is called, a living body grows.
2. Living bodies, as they are constantly assimilating fresh matter, are incessantly losing portions of their substance-or, in
other words, partial death is a constant accompaniment of life.
3. If our observation be continued for a sufficient length of
time, we find that every living body has the power of reproducing its like. That is to say, every-living body has, directly
or indirectly, the power of giving origin to minute germs which
are developed into the likeness of the parent. 4. The matter
of a living body is subject to the same physical and chemical
forces as those which affect dead matter; but it is further the
2




4                MANUAL OF ZOOLOGY.
seat of something in virtue of which the living body can override the physical laws which control all dead matter. The
living body is the seat of energy, and can overcome the primary law of the inertia of matter.  It has certain relations
with the outer world other than those of mere passivity.
However humble it may be, and even if it be permanently
rooted to one place, some part or other of every living body
possesses the power of spontaneous and independent movement-a power possessed by nothing that is dead.
3. NATURE OF LIFE.
We hlave next to determine-and the question is one of
great difficulty-what connection exists between organisation
and life. Is organisation, as we have defined it, essential to
the manifestation of life, or can vital phenomena be exhibited
by any body Which is devoid of an organised structure?  In
other words, is life the cause of organisation, or the result of it?
And first, what do we mean by life?
Life has been variously defined by different writers. Bichat
defines it as " tle sum total of the functions which resist death;"
Treviranus, as "the constant uniformity of phenomena with
diversity of external influences; " Duges, as " the special activity of organised bodies; " and Beclard, as " organisation in
action." All these definitions, however, are more or less objectionable, since the assumption underlies them all that life is
inseparably connected with organisation. In point of fact, no
rigid definition of life appears to be at present possible, and it
is best to regard it as being simply a tendency exhibited by
certain forms of matter, under certain conditions, to pass
through a series of changes in a more or less definite and
determinate sequence.
As regards the connection between life and organisation,
it appears that whilst all organised bodies exhibit this tendency to change, and are therefore alive, all living -beings are
not necessarily organised.  Many of the lowest forms of life
(such as the Foraminifera amongst the Protozoa) fail to fulfil
one of the most essential conditions of organisation, being devoid of definite parts or organs of any kind. Nevertheless, they
are capable of manifesting all the essential phenomena of life;
they are produced from bodies like themselves; they eat,
digest, and move, and exhibit distinct sensibility to many external impressions. Furthermore, many of these little masses
of structureless jelly possess the power of manufacturing for
themselves, of lime, or of the still more intractable flint,




NATURE OF LIFE.                         5
external shells of surpassing beauty and mathematical regu.
larity. In the face of these facts we are therefore compelled
to come to the conclusion that life is truly the cause and not
the consequence of organisation; or, in other words, that organisation is not an intrinsic and indispensable condition of
vital phenomena.
Such an intrinsic and indispensable condition is, however,
to be found in the presence of a uniform " physical basis," to
which has been applied the name of " protoplasm " (the "bioplasm " of Dr Beale). Without some such a material substratum, or medium upon which to work, no one vital phenomenon can be exhibited. The necessary forces may be there,
but in the absence of this necessary vehicle there can be no
outward and visible manifestation of their existence. Life,
therefore, as we know it, and as far as zewe know it, may be said
to be inseparably connected with protoplasm. In other words,
protoplasm bears to life the same relation that a conductor does
to the electric current. It is the sole medium through which
life can be brought into relation with the external world.  There
is, however, as yet, no reason to believe that protoplasmic matter holds any other or higher relation to life, or that vital
phenomena are in any way an inherent property of the matter
by which alone they are capable of being manifested.
As regards its nature, protoplasm, though capable of forming the most complex structures, does not necessarily exhibit
anything which can be looked upon as organisation, or differentiation into distinct parts; and its chemical composition
is the only constant which can be approximately stated. It
consists, namely, in all its forms, of the four elements, carbon,
hydrogen, oxygen, and nitrogen, united into a proximate
compound to which Mulder applied the name of " proteine,"
and which is very nearly identical with albumen or white-ofegg.  It further appears probable that all forms of protoplasm
can be made to contract by means of electricity, and "are
liable to undergo that peculiar coagulation at a temperature *of
4o~-50o  centigrade, which has been called' heat-stiffening'"
(Huxley).
If we admit, then, with Huxley-and the admission requires some qualifications- that " protoplasm, simple or
nucleated, is the formal basis of all life,' there, nevertheless,
* It has not yet been shown that the living matter which we designate.y the convenient term of " protoplasm" has universally and in all cases
a constant and undeviating chemical composition; and there is, indeed,
reason to believe that this is not the case. It is also certain that there are
other materials, the exact use of which we do not at present know, which




6                 MANUAL OF ZOOLOGY.
remain certain conditions equally indispensable to the external
manifestation of vital phenomena; though life itself, or the
power of exhibiting vital phenomena, may be preserved for a
longer or shorter period, even though these conditions be absent. These extrinsic conditions of vitality are, firstly, a certain temperature varying from near the freezing-point to I200
or I300; secondlay, the presence of water, which enters largely
into the composition of all living tissues; thirdly, the presence
of oxygen in a free state,-this, like water, appearing to be a
sine qua non of life, though certain fungi are stated to offer
an exception to this statement.O
The non-fulfilment of any of these conditions for any length
of time, as a rule, causes death, or the cessation of vitality; but,
as before remarked, life may sometimes remain' in a dormant
or "potential " condition for an apparently indefinite length of
time. An excellent illustration of this is afforded by the great
tenacity of life, even under unfavourable conditions, exhibited
by the ova of some animals and the seeds of many plants; but
a more striking example is to be found in the Rotifera, or Wheelanimalcules. These are minute, mostly microscopic creatures,
which inhabit almost all our ponds and streams. Diminutive
as they are, they are nevertheless, comparatively speaking, of
a very high grade of organisation.   They possess a mouth,
masticatory organs, a stomach, and alimentary canal, a distinct and well-developed nervous system, a differentiated reproductive apparatus, and even organs of vision. Repeated
experiments, however, have shown the remarkable fact, that,
with their aquatic habits and complex organisation, the'Rotifers are capable of submitting to an apparently indefinite deprivation of the necessary conditions of their existence, without thereby losing their vitality.  They may be dried and
reduced to dust, and may be kept in this state for a period of
many years; nevertheless, the addition of a little water will
at any time restore them to their pristine vigour and activity.
It follows, therefore, that an organism may be deprived of all
power of manifesting any of the phenomena which constitute
what we call life, without losing its hotd upon the vital forces
which belong to it.
If, in conclusion, it be asked whether the term " vital force"
is any longer permissible in the mouth of a scientific man,
the question must, I think, be answered in the affirmative.
are absolutely essential to the maintenance of life, probably even in its
humblest manifestations.
* Recent experiments, as ye unconfirmed, would go to prove that these
conditions of vitality are not of such essential importance.




NATURE OF LIFE.                     7
Formerly, no doubt, the progress of science was retarded and
its growth checked by a too exclusive reference of natural
phenomena to a so-called vital force.  Equally unquestionable
is the fact that the development of Biological science has progressed contemporaneously with the successive victories gained
by the physicists over the vitalists.  Still, no physicist has
hitherto succeeded in explaining any fundamental vital phenomenon upon purely physical and chemical principles. The
simplest vital phenomenon has in it something over and above
the merely chemical and physical forces which we can demonstrate in the laboratory. It is easy, for example, to say that
the action of the gastric juice is a chemical one, and doubtless the discovery of this fact was a great step in physiological
science. Nevertheless, in spite of the most searching investigations, it is certain that digestion presents phenomena
which are as yet inexplicable upon any chemical theory. This
is exemplified in its most striking form, when we look at a
simple organism like the Amoeba. This animalcule, which is
structurally little more than a mobile lump of jelly,- digests as
perfectly-as far as the result to  itself is concerned-as does
the most highly organised animal with the most complex
digestive apparatus. It takes food into its interior, it digests
it without the presence of a single organ for the purpose; and
still more, it possesses that inexplicable selective power by
which it. assimilates out of its food such constituents as it
needs, whilst it rejects the remainder. In the present state of
our knowledge, therefore, we must conclude that even in the
process of digestion as exhibited in the Amoeba there is something that is not merely physical or chemical. Similarly, any
organism when just dead consists of the same protoplasm as
before, in the same forms, and with the same arrangement;
but it has most unquestionably lost a something by which all its
properties and actions were modified, and some of them were
produced.  What that something is, we do not know, and
perhaps never shall know; and it is possible, though highly
improbable, that future discoveries may demonstrate that it
is merely a subtle modification of some physical force. In
the meanwhile, as all vital actions exhibit this mysterious
something, it would appear unphilosophical to ignore its existence altogether, and the term " vital force." may therefore be
retained with advantage.  In using this term, however, it
must not be forgotten that we are simply employing a convenient expression for an unknown quantity, for that residual
portion of every vital action which cannot at present be referred to the operation of any known physical force.




8               MANUAL OF ZOOLOGY.
4. DIFFERENCES BETWEEN ANIMALS AND PLANTS.
Wve have now arrived at some definite notion of the essential characters of living beings in general, and we have next to
consider what are the characteristics of the two great divisions
of the organic world. What are the characters which induce
us to place any given organism in either the vegetable or the
animal kingdom? What, in fact, are the differences between
animals and plants?
It is generally admitted that all bodies which exhibit vital
phenomena are capable of being referred to one of the two
great kingdoms of organic nature. At the same time it is
often extremely difficult in individual cases to come to any
decision as to the kingdom to which a given organism should
be referred, and in many cases the determination is purely
arbitrary. So strongly, in fact, has this difficulty been felt,
that some observers have established an intermediate kingdom,
a sort of no-man's-land, for the reception of those debatable
organisms which cannot be definitely and positively classed
either amongst vegetables or amongst animals. Thus, Dr
Ernst Hoeckel has proposed to form an intermediate kingdom,
which he calls the Regnum Protisticum, for the reception of all
doubtful organisms. Even such a cautious observer as Dr
Rolleston, whilst questioning the propriety of this step, is
forced to conclude that "there are organisms which at one
period of their life exhibit an aggregate of phenomena such as
to justify us in speaking of them as animals, whilst at another
they appear to be as distinctly vegetable."
In the case of the higher animals and plants there is no
difficulty; the former being at once distinguished by the
possession of a nervous system, of motor power which can be
voluntarily exercised, and of an internal cavity fitted for the
reception and digestion of solid food. The higher plants, on
the other hand, possess no nervous system or organs of sense,
are incapable of independent locomotion, and are not provided
with an internal digestive cavity, their food being wholly fluid
or gaseous. These distinctions, however, do not hold good as
regards the lower and less highly organised members of the
two kingdoms, many animals having no nervous system or internal digestive. cavity, whilst many plants possess the power
of locomotion; so that we are compelled to institute a closer
comparison in the case of these lower forms of life.
a. Fo-rm. —As regards external configuration, of all characters the most obvious, it must be admitted that no absolute
distinction can be laid down between plants and animals.




DIFFERENCES BETWEEN ANIMALS AND PLANTS. 9
Many of our ordinary zoophytes, such as the Hydroid Polypes,
the sea-shrubs and corals-as, indeed, the name zoophyte
implies —are so similar in external appearance to plants that
they were long described as such. Amongst the Molluscoida,
the common sea-mat (Flustra) is invariably regarded by seaside visitors as a sea-weed. Many of the Protozoa are equally
like some of the lower plants (Protophyta); and even at the
present day there are not wanting those who look upon the
sponges as belonging to the vegetable kingdom. On the other
hand, the embryonic forms,'or "zoospores," of certain undoubted plants (such as the Protococcus nivalis, Vaucheria,
&c.) are provided with ciliated processes with which they
swim about, thus coming so closely to resemble some of tlhe
Infusorian animalcules as to have been referred to that division of the Protozoa.
b. Interinal Structure.-Here, again, no line of demarcation
can be drawn between the animal and vegetable kingdoms.
In this respect all plants and animals are fundamentally
similar, being alike composed of molecular, cellular, and fibrous tissues.
c. Chemical Conmposition.-Plants, speaking generally, exhibit
a preponderance of ternary compounds of carbon, hydrogen,
and oxygen-such as starch, cellulose, and sugar-whilst
nitrogenised compounds enter more largely into the composition of animals. Still both kingdoms contain identical or
representative compounds, though there may be a difference
in the proportion of these to one another.  Moreover, the
most characteristic of all vegetable compounds, viz,, cellulose,
has been detected in the outer covering of the sea-squirts,
or Ascidian Molluscs; and the so-called "glycogen," which is
secreted by the liver of the Mammalia, is closely allied to, if
not absolutely identical with, the hydrated starch of plants. As
a general rule, however, it may be stated that the presence in
any organism of an external envelope of cellulose raises a strong
presumption of its vegetable nature.  In the face, however,
of the facts above stated, the presence of cellulose cannot be
looked upon as absolutely conclusive. Another highly characteristic vegetable compound is chloriophyll, the green colouringtmatter of plants..Any organism which exhibits chlorophyll
in any quantity, as a proper element of its tissues, is most
probably vegetable. As in the case of cellulose, however, the
presence of chlorophyll cannot be looked upon as a certain
test, since it occurs normally in certain undoubted animals
(e.g., Steilor-, amongst the rfilusoria, and the Hy),zha viridis,
or the green Fresh-water Polype, amongst the Cwrlczferala).




10             MANUAL OF ZOOLOGY.
d. Motor Power.-This, though broadly distinctive of animals, can by no means be said to be characteristic of them.
Thus, many animals in their mature condition are permanently
fixed, or attached to some foreign object; and the embryos of
many plants, together with not a few adult forms, are endowed
with locomotive power by means of those vibratile, hair-like
processes which are called "cilia," and are so characteristic
of many of the lower forms of animal life. Not only is this
the case, but large numbers of the lower plants, such as the
Diatoms and Desmids, exhibit throughout life an amount and
kind of locomotive power which does not admit of being rigidly
separated from the movements executed by animals, though the
closest researches have hitherto failed to show the mechanism
whereby these movements are brought about.
e. Vatzure of the Food.-Whilst all the preceding points have
failed to yield a means of invariably separating animals from
plants, a distinction which holds good almost without exception is to be found in the nature of the food taken respectively
by each, and in the results of the conversion of the same. The
unsatisfactory feature, however, in this distinction is this, that
even if it could be shown to be, theoretically, invariably true,
it would nevertheless be practically impossible to apply it to
the greater number of those minute organisms concerning
which alone there can be any dispute.
As a broad rule, all plants are endowed with the power of
converting inorganic into organic matter. Thefood of plants
consists of the inorganic compounds, carbonic acid, ammonia,
and water, along with small quantities of certain mineral salts.
From these, and from these only, plants are capable of elaborating the proteinaceous matter or protoplasm which constitutes the physical basis of life. Plants, therefore, take as food
very simple bodies, and manufacture them into much more
complex substances. In other words, by a process of deoxidation or unburning, rendered possible by the influence of sunlight only, plants convert the inorganic or stable elementsammonia, carbonic acid, water, and certain mineral salts-into
the organic or unstable elements of food. The whole problem
of nutrition may be narrowed to the question as to the modes
and laws by which these stable elements are raised by the vital
chemistry of the plant to the height of unstable compounds.
To this general statement, however, an exception must seemingly be made in favour of certain fungi, which require organised compounds for their nourishment.
On the other hand, no known animal possesses the power
of converting inorganic compounds into organic matter, but




DIFFERENCES BETWEEN ANIMALS AND PLANTS. I I
all, mediately or immediately, are dependent in this respect
upon plants. All animals, as far as is certainly known, require
ready-made proteinaceous matter for the maintenance of existence, and this they can only obtain in the first instance from
plants. Animals, in fact, differ from plants in requiring as food
complex organic bodies which they ultimately reduce to very
much simpler inorganic bodies. The nutrition of animals is
a process of oxidation or burning, and consists essentially in
the conversion of the energy of the food into vital work; this
conversion being effected by the passage of the food into living
tissue. Plants, therefore, are the great manufacturers in nature,
-animals are the great consumers.
Just, however, as this law does not invariably hold good for
plants, certain fungi being in this respect animals, so it is
not impossible that a limited exception to the universality ot
the law will be found in the case of animals also.. Thus, in
some recent investigations into the fauna of the sea at great
depths, a singular organism, of an extremely low type, but
occupying large areas of the sea-bottom, has been discovered,
to which Professor Huxley has given the name of Bathybius.
As vegetable life is extremely scanty, or is altogether wanting,
in these abysses of the ocean, it has been conjectured that
this organism is possibly endowed with the power-otherwise
exclusively found in plants-of elaborating organic compounds
out of inorganic materials, and in this way supplying food for
the higher animals which surround it.  The water of the
ocean, however, at these enormous depths, is richly charged
with organic matter in solution, and this conjecture is thereby
rendered doubtful.
Be this as it may, there remain to be noticed two distinctions, broadly though not universally applicable, which are
due to the nature of the food required respectively by animals
and plants. In the first place, the food of all plants consists
partly of gaseous matter and partly of matter held in solution.
They require, therefore, no special aperture for its admission,
and no internal cavity for its reception. The food of almost
all animals consists of solid particles, and they are therefore
usually provided with a mouth and a distinct digestive cavity.
Some animals, however, such as the tape-worm and the Gregarinee, live entirely by the imbibition of organic fluids through
the general surface of the body, and many have neither a distinct mouth nor stomach.
Secondly, plants decompose carbonic acid, retaining the
carbon and setting free the oxygen, certain fungi forming an
exception to this law. The reaction of plants upon the atmo.




12              MANUAL OF ZOOLOGY.
sphere is therefore characterised by the production of free
oxygen. Animals, on the other hand, absorb oxygen and emit
carbonic acid, so that their reaction upon the atmosphere is
the reverse of that of plants, and is characterised by the production of carbonic acid.
Finally, it is worthy of notice that it is in their lower and
not in their higher developments that the two kingdoms of
organic nature approach one another. No difficulty is experienced in separating the higher animals from the higher
plants, and for these universal laws can be laid down to which
there is no exception. It might, not unnaturally, have been
thought that the lowest classes of animals would exhibit most
affinity to the highest plants, and that thus a gradual passage
between the two kingdoms would be established. This is not
the case, however. The lower animals are not allied to the
higher plants, but to the lower; and it is in the very lowest members of the vegetable kingdom, or in the embryonic and immature forms of plants little higher in the scale, that we find such
a decided animal gift as the power of independent locomotion.
It is also in the less highly organised and less specialised forms
of plants that we find the only departures from the great laws
of vegetable life, the deviation being in the direction of the
laws of animal life.
5. MORPHOLOGY AND PHYSIOLOGY.
The next point which demands notice relates to the nazture
of the differences between one animal and another, and the
question is one of the highest importance. Every animalas every plant-may be regarded from two totally distinct,
and, indeed, often apparently opposite, points of view. From
the first point of view we have to look simply to the laws,
form, and arrangement of the structures of the organism; in
short, to its external shape and internal structure. This constitutes the science of morphology (iogqr, form, and X6'yo, discourse).  From' the second, we have to study the vital actions
performed by living beings and the finctions discharged by the
different parts of the organism.  This constitutes the science
of physiology.
A third department of zoology is concerned with the relations
of the organism to the external conditions under which it is
placed, constituting a division of the science to which the term
"distribution " is applied.
Morphology, again, not only treats of +e, structure of living
beings in their fully-developed condition (anatomy), but is




DIFFERENCES BETWEEN DIFFERENT ANIMALS.  13
also concerned with the changes through which every living
being has to pass before it assumes its mature or adult characters (embryology or development).  The term  " histology" is
further employed to designate that branch of morphology which
is specially occupied with the investigation of minute or microscopical tissues.
Physiology treats of all the functions exercised by living
bodies, or by the various definite parts or organs, of which
most animals are composed.  All these functions come under
three heads: —I. Functions of Nitrition, divisible into functions of absorption and metamorphosis, comprising those functions which are necessary for the growth and maintenance of
the organism.  2. Functions of Repiolvduction, whereby the perpetuation of the species is secured. 3. Functions of Correlation,
comprising all those functions (such as sensation and voluntary
motion) by which the external world is brought into relation
with the organism, and the organism in turn reacts upon the
external world.
Of these three, the functions of nutrition and reproduction
are often collectively called the functions of organic or vegetative life, as being common to animals and plants; while the
functions of correlation are called the animal functions, as
being more especially characteristic of, though not peculiar to,
animals.
6. DIFFERENCES BETWEEN DIFFERENT ANIMALS.
All the innumerable differences which subsist between different animals may be classed under two heads, corresponding
to the two aspects of every living being, morphological and
physiological.  One animal differs from another either morphologically, in the fundamental points of its structure; or phzysioogically, in the manner in which the vital functions of the
organism are discharged. These constitute the only modes in
which any one animal can differ from any other; and they may
be considered respectively under the qeads of Specialisation of
Function and Morphological type.
a. Specialisation of Function.-All animals alike, whatever
their structure may be, perform  the three great physiological
functions; that is to say, they all nourish themselves, reproduce their like, and hlave certain relations with the external
world.  They differ from one another physiologically in the
lmanner in which these functions are performed.  Indeed, it is
only in the functions of correlation that it is possible that there
should be any difference in the amount or perfection of the
function performed by the organism, since nutrition and repro



1r 4             MANUAL OF ZOOLOGY.
duction, as far as their results are concerned, are essentially the
same in all animals. In the manner, however, in which the
same results are brought about, great differences are observable
in different animals. The nutrition of such a simple organism
as the Amoeba is, indeed, performed perfectly, as far as the
result to the animal itself is concerned —as perfectly as in the
case of the highest animal —but it is performed with the simplest
possible apparatus. It may, in fact, be said to be performed
without any special apparatus, since any part of the surface of
the body may be extemporised into a mouth, and there is no
differentiated alimentary cavity. And not only is the nutritive
apparatus of the simplest character, but the function itself is
equally simple, and is entirely divested of those complexities
and separations into secondary functions which characterise
the process in the higher animals. It is the same, too, with
the functions of reproduction and correlation; but this point
will be more clearly brought out if we examine the method in
which one of the three primary functions is performed in two
or three examples. Nutrition, as the simplest of the functions,
will best answer the purpose.
In the simpler Protozoa, such as the Amoeba, the process of
nutrition consists essentially in the reception of food, its digestion within the body, the excretion of effete or indigestible
matter, and the distribution of the nutritive fluid through the
body. The first three portions of this process are effected without any special organs for the purpose, and for the last there is
simply a rudimentary contractile cavity. Respiration, if it can
be said to exist at all as a distinct function, is simply effected
by the general surface of the body.
In a Ccelenterate animal, such as a sea-anemone, the function of nutrition has not advanced much in complexity, but
the means for its performance are somewhat more specialised.
Permanent organs of prehension (tentacles) are present,. there
is a distinct mouth, and there is a persistent internal cavity for
the reception of the food; but this is not shut off from the
general cavity of the body, and there are no distinct circulatory
or respiratory organs.
In a Mollusc, such as the oyster, nutrition is a much more
complicated process. There is a distinct mouth, and an alimentary canal which is shut off from the general cavity of the
body, and is provided with a separate aperture for the excretion of effete and indigestible matters. Digestion is performed
by a distinct stomach with accessory glands; a special contractile cavity, or heart, is provided for the propulsion of the nutritive products of digestion through all parts of the organism,




DIFFERENCES BETWEEN DIFFERENT ANIMALS.  15
and the function of respiration is performed by complex organs
specially adapted for the purpose.
It is not necessary here to follow out this comparison
further. In still higher animals the function of nutrition
becomes still further broken up into secondary functions, for
the due performance of which special organs are provided, the
complexity of the organism thus necessarily increasing pari
tassu with the complexity of the function. This gradual subdivision and elaboration is carried out equally with the other
two physiological functions-viz., reproduction and correlation
-and it constitutes what is technically called the " specialisation of functions," though it has been more happily termed by
Milne-Edwards "the principle of the physiological division of
labour." It is needless, however, to remark that in the higher
animals it is the functions of correlation which become most
highly specialised-disproportionately so, indeed, when compared with the development of the nutritive and reproductive
functions.
b. Morphological Type. —The first point in which one
animal may differ from another is the degree to which the
principle of the physiological division of labour is carried.
The second point in which one animal may differ from another
is in its "morphological type;" that is to say, in the fundamental plan upon which it is constructed. By one not specially
acquainted with the subject it might be readily imagined that
each species or kind of animal was constructed upon a plan
peculiar to itself and not shared by any other. This, however, is far from being the case; and it is now universally
recognised that all the varied species of animals-however
-great the apparent amount of diversity amongst them-may be
arranged under no more than half-a-dozen primary morphological types or plans of structure. Upon one or other of
these five or six plans every known animal, whether living or
extinct, is constructed. It follows from the limited number of
primitive types or patterns, that great numbers of animals
must agree with one another in their morphological type. It
follows also that all so agreeing can differ from one another.only in the sole remaining element of the question-namely,
by the amount of specialisation of function which they exhibit.
Every animal, therefore, as Professor Huxley has well expressed
it, is the resultant of two tendencies, the one morphological,
the other physiological.
The six types or plans of structure, upon one or other of
which all known animals have been constructed,'are technically called "sub-kingdoms," and are known by- the names




i6              MANUAL OF ZOOLOGY.
Protozoa, Ccelenterata, Annuloida, Annulosa, Mollusca, and
Vertebrata. We have, then, to remember that every member
of each of these primary divisions of the animal kingdom
agrees with every other member of the same division in being
formed upon a certain definite plan or type of structure, and
differs from every other simply in the grade of its organisation,
or in other words, in the degree to which it exhibits specialisation of function.
VON BAER'S LAW OF DEVELOPMENT.-As the study of living
beings in their adult condition shows us that the differences
between those which are constructed upon the same morphological type depend upon the degree to which specialisation
of function is carried, so the study of development teaches
us that the changes undergone by any animal in passing from
the embryonic to the mature condition are due to the same
cause. All the members of any given sub-kingdom, when
examined in their earliest embryonic condition, are found to
present the same fundamental characters.  As development
proceeds, however, they diverge from one another with greater
or less rapidity, until the adults ultimately become more or
less different, the range of possible modification being apparently almost illimitable.  The differences are due to the
different degrees of specialisation of function necessary to
perfect the adult: and therefore, as Von Baer put it, the progress of development is from the general to the special.
It is upon a misconception of the true import of this law
that the theory arose, that every animal in its development
passed through a series of stages in which it resembles, in turn,
the different inferior members of the animal scale.  With
regard to man, standing at the top of the whole animal
kingdom, this theory has been expressed as follows:-" Human
organogenesis is a transitory comparative anatomy, as, in its
turn, comparative anatomy is a fixed and permanent state of
the organogenesis of man" (Serres).  Iin other words, the
embryo of a Vertebrate animal was believed to pass through a
series of changes corresponding respectively to the permanent
types of the lower sub-kingdoms-namely, the- Protozoa, Ccelenterata, Annuloida, Annulosa, and Mollusca-before finally'
assuming the true vertebrate characters.  Such, however, is
not truly the case. The ovum of every animal is from the
first impressed with the power of developing in one direction
only, and very early exhibits the fundamental characters proper
to its sub-kingdom, never presenting the structural peculiarities belonging to any other morphological type. Nevertheless, the differences which subsist between the menmbers of




HOMOLOGY, ANALOGY, AND HOMOMORPIISM.   17
each sub-kingdom in their adult condition are truly referable
to the degree to which development proceeds, the place of
each individual in his own sub-kingdom being regulated by the
stage at which development is arrested. Thus, many cases
are known in which the younger stages of a given animal
represent the permanent adult condition of an animal somewhat lower in the scale. To give a single example, the young
Gasteropod (amongst the Mollusca) transiently presents all the
essential characters which permanently distinguish the adult
Pteropod. The development of the Gasteropod, however, proceeds beyond this point, and the adult is much more highly
specialised than is the adult Pteropod.
7. HOMOLOGY, ANALOGY, AND HIOMOMORPHISM.
When organs in different animals agree with one another in
fundamental structure, they are said to be "homologous;"
when they perform the same functions they are said to be
" analogous." Thus the wing of a bird and the arm of a man
are constructed upon the same fundamental plan, and they
are therefore homologous organs. They are not analogous,
however, since they do not perform the same function, the
one being adapted for aerial locomotion, the other being an
organ of prehension. On the other hand, the wings of a bird
and the wings of an insect both serve for flight, and they are
therefore analogous, since they perform  the same function.
They are not homologous, however, as they are constructed
upon wholly dissimilar plans.  There are numerous cases,
however, in which organs correspond with one another' both
structurally and functionally, in which case they are both
homologous and analogous.
A form of homology is often seen in a single animal in which
there exists a succession of parts which are fundamentally
identical in structure, but are variously modified to fulfil different functions. Thus a Crustacean-such as the lobstermay be looked upon as being composed of a succession of
rings, each of which bears a pair of appendages, these appen
dages being constructed upon the same type, and being therefore homologous. They are, however, variously modified in
different regions of the body to enable them to fulfil special
functions, some being adapted for swimming, others for walking, others for prehension, others for mastication, and so on.
This succession of fundamentally similar parts in the same
animal constitutes what is- known as serial homology. When,
however, the successive parts are similar to one another, both




I8              MANUAL OF ZOOLOGY.
in structure and in function, the case becomes rather one of
what is called " vegetative " or " irrelative repetition." An excellent instance of this is seen in the common Millipede (Iulus).
Homomorphism.-Many examples occur, both among animals
and among plants, in which families widely removed from one
another as to their fundamental structure, nevertheless present a singular, and sometimes extremely close, resemblance
in their external characters. Thus the composite Hydroid
Polypes and the Polyzoa are singularly like one anotherso much so, that they have often been classed together;
whereas, in reality, they belong to different sub-kingdoms.
Many other cases of this resemblance of different animals
might be adduced, and in many cases these "representative
forms" appear to be able to fill each other's places in the
general economy of nature. This is so far true, at any rate,
that "homomorphous " forms are generally found in different
parts of the earth's surface. Thus, the place of the Cacti
of South America is taken by the Euphorbiae of Africa; or,
to take a zoological illustration, many of the different orders
of Mammalia are represented in the single order Marsupialia
in Australia, in which country this order has almost alone to
discharge the functions elsewhere performed by several orders.
Many homomorphous forms, however, live peacefully side by
side, and it is difficult to say whether in this case the resemblance between them is for the advantage or for the disadvantage of either. In other cases we find certain animals putting
on the external characters of certain other animals, to which
they may be closely related, or from which they may be widely
separated in zoological position. Such cases are said to be examples of "mimicry," and such animals are said to be " mimetic."   Excellent examples of this may be found amongst
certain Butterflies, or in the close resemblance of the clearwinged Moths to Bees and Hornets.  In all these cases it
appears that the mimetic species is protected from some enemy
by its outward similarity to the form which it mimics. Finally,
there are numerous cases in which animals mimic certain
natural objects, and thus greatly diminish their chances of
being detected by their natural foes. Excellent instances of
this are afforded by the insects known as Walking-leaves (Phyllium) and Walking- sticks (Phasmide), which respectively
present the most singular resemblance to leaves and dried
twigs.
8. CORRELATION OF GROWTH.
This term is employed by zoologists to express the empi.




CLASSIFICATION.                    19
rical law, that certain structures, not necessarily or usually
connected together by any visible link, invariably occur in
association with one another, and never occur apart,-so far,
at any rate, as human observation goes.
Thus, all animals which possess two condyles on the occipital bone, and possess non-nucleated red blood-corpuscles,
suckle their young. Why an animal with only one condyle
on its occipital bone should not suckle its young we do not
know, and perhaps we shall at some future time find mammary glands associated with a single occipital condyle. Again,
the feet are cleft in all animals which ruminate, but not in
any other. In other cases the correlation is even more apparently lawless, and is even amusing. Thus all, or almost all,
cats which are entirely white and have blue eyes, are at the
same time deaf. With regard to these and similar generalisations we must, however, bear in mind the following
three points:I. The various parts of the organisation of any animal are
so closely interconnected, and so mutually dependent upon
one another, both in their growth and development, that the
characters of each must be in some relation to the characters
of all the rest, whether this be obviously the case or not.
2. It is rarely possible to assign any reason for correlations
of structure, though they are certainly in no case accidental.
3. The law is a purely empirical one, and expresses nothing
more than the result of experience; so that structures which
we now only know as occurring in association, may ultimately
be found dissociated, and conjoined with other structures of a
different character.
9. CLASSIFICATION.
Classification is the arrangement of a number of diverse
objects into larger or smaller groups, according as they exhibit more or less likeness to one another. The excellence of
any given classification will depend upon the nature of the
points which are taken as determining the resemblance. Systems of classification, in which the groups are founded upon
mere external and superficial points of similarity, though
often useful in the earlier stages of science, are always found
in the long-run to be inaccurate. It is needless, in fact, to
point out that many living beings, the structure of which is
fundamentally different, may nevertheless present such an
amount of adaptive external resemblance to one another, that
they would be grouped together in any "artificial" classification.  Thus, to take a single example, the whale, by its




20              MANUAL OF ZOOLOGY.
external characters, would certainly be grouped amongst the
fishes, though widely removed from them in all the essential
points of its structure.  " Natural" systems of classification,
on the other hand, endeavour to arrange animals into divisions founded upon a due consideration of all the essential
and fundamental points of structure, wholly irrespective of
external similarity of form and habits. Philosophical classification depends upon a due appreciation of what constitute
the true points of difference and likeness amongst animals;
and we have already seen that these are morphological type
and specialisation of function.  Philosophical classification,
therefore, is a formal expression of the facts and laws of
Morphology and Physiology. It follows that the more fully
the programme of a philosophical and strictly natural classification can be carried out, the more completely does it afford
a condensed exposition of the fundamental construction of the
objects classified. Thus, if the whale were placed by an artificial grouping amongst the fishes, this would simply express
the facts that its habits are aquatic and its body fish-like.
When, on the contrary, we obtain a natural classification, and
we learn that the whale is placed amongst the Mammalia, we
then know at once that the young whale is born in a comparatively helpless condition, and that its mother is provided
with special mammary glands for its support; this expressing
a fundamental distinction from all fishes, and being associated
with other equally essential correlations of structure.
The entire animal kingdom is primarily divided into some
half-a-dozen great plans of structure, the divisions thus formed
being called " sub-kingdoms."  The sub-kingdoms are, in turn,
broken up into classes, classes into orders, orders into families,
families into genera, and genera into species. We shall examine
these successively, commencing with the consideration of a
species, since this is the zoological unit of which the larger
divisions are made up.
Species.-No term is more difficult to define than " species,"
and on no point are zoologists more divided than as to what
should be understood by this word. Naturalists, in fact, are
not yet agreed as to whether the term species expresses a real
and permanent distinction, or whether it is to be regarded
merely as a convenient, but not immutable, abstraction, the
employment of which is necessitated by the requirements of
classification.
By Buffon, " species" is defined as " a constant succession of
individuals* similar to and capable of reproducing each other."
* In using the term "ind(ividual," it must be borne in mind that thq




CLASSIFICATION.                    21
De Candolle defines species as an assemblage of all those
individuals which resemble each other more than they do
others, and are able to reproduce their like, doing so by the
generative process, and in such a manner that they may be
supposed by analogy to have all descended from a single being
or a single pair.
M. de Quatrefages defines species as " an assemblage of
individuals, more or less resembling one another, which are descended, or may be regarded as being descended, from a single
primitive pair by an uninterrupted succession of families."
Muller defines species as "a living form, represented by individual beings, which reappears in the product of generation
with certain invariable characters, and is constantly reproduced by the generative act of similar individuals."
According to Woodward, " all the specimens, or individuals,
which are so much alike that we may reasonably believe them
to have descended from a common stock, constitute a species."
From the above definitions it will be at once evident that
there are two leading ideas in the minds of zoologists when
they employ the term species; one of these being a certain
amount of resemblance between individuals, and the other
being the proof that the individuals so resembling each other
have descended from a single pair, or from pairs exactly similar to one another. The characters in which individuals must
resemble one another in order to entitle them to be grouped
in a separate species, according to Agassiz, " are only those
determining size, proportion, colour, habits, and relations to
surrounding circumstances and external objects."
On a closer examination, however, it will be found that
these two leading ideas in the definition of species-external
resemblance and community of descent-are both defective,
and liable to break down if rigidly applied. Thus, there are
in nature no assemblages of plants or animals, usually grouped
together into a single species, the individuals of which exactly
resemble one another in every point.  Every naturalist is
compelled to admit that. the individuals which compose any
so-called species, whether of plants or animals, differ from
one another to a greater or less extent, and in respects which
may be regarded as more or less important. The existence
of such individual differences is attested by the universal
employment of the terms "varieties" and "races."  Thus a
"variety" comprises all those individuals which possess some
"zoological individual" is meant; that is to say, the total result of the
development of a single ovum, as will be hereatter explained at greater
ength.




22                MANUAL OF ZOOLOGY.
distinctive peculiarity in common, but do not differ in other
respects from another set of individuals sufficiently to entitle
them to take rank as a separate species.  A  " race," again, is
simply a permanent or " perpetuated" variety. The question,
however, is this-How far may these differences amongst individuals obtain without necessitating their being placed in a
separate species?  In other words: How great is the amount
of individual difference which is to be considered as merely
" varietal," and at what exact point do these differences become
of " specific" value? To this question no answer can be given,
since it depends entirely upon the weight which different
naturalists would attach to any g;ven individual difference.*
Distinctions which appear to one observer as sufficiently great
to entitle the individuals possessing them  to be grouped as a
distinct species, by another are looked upon as simply of
varietal value; and, in the nature of the case, it seems impossible to lay down any definite rules. To such an extent do
individual differences sometimes exist in particular generatermed " protean " or " polymorphic " genera-that the determination of the different species and varieties becomes an
almost hopeless task.
Besides the individual differences which ordinarily occur
in all species, other cases occur in which a species consists
normally and regularly of two or even three distinct forms,
which cannot be said to be mere varieties, since no intermediate forms can be discovered.  When two such distinct
forms exist, the species is said to be " dimorphic," and when
three are present, it is called " trimorphic."  Thus, in dimorphic
plants a single species is composed of two distinct forms,
similar to one another in all respects except in their reproductive organs, the one form having a long pistil and short
stamens, the other a short pistil with long stamens. In trimorphic plants, the species is composed of three such distinct
forms, which'differ in like manner in the conformation of their
reproductive organs, though they are otherwise undistinguishable. —(Darwin.)  Similar cases are known in animals, but in
them the differences, though apparently connected with reproduction, are not confined to the reproductive organs. Thus
the females of certain butterflies normally appear under two or
three entirely different forms, not connected by any intermediate
links; and the same thing occurs in some of the Crustacea.
* As an example of this, it is sufficient to allude to the fact that hardly
any two botanists agree as to the number of species of Willows and Brambles in the British Isles. What one observer classes as mere varieties,
another regards as good and distinct species.




CLASSIFICATION.                    23
As regards, therefore, the first point in the definition of
species —namely, the.external reselnblance of assemblages of
individuals-we are forced to conclude that no two individuals
are exactly alike; and that the amount and kind of external
resemblance which constitutes a species is not a precise and
invariable quantity, but depends upon the value attached to
particular characters by any given observer.
The second point in the definition of species-namely, community of descent-is hardly in a more satisfactory condition,
since the descent of any given series of individuals from a
single pair, or-from pairs exactly similar to one another, is at
best but a probability, and is in no case capable of proof.  In
the case of the higher animals it can doubtless be shown that
certain assemblages of individuals possess amongst themselves
the power of fecundation and of producing fertile progeny,
and that this power does not extend to the fecundation of individuals belonging to another different assemblage. Amongst
the higher animals, " crosses " or "hybrids" can only be produced between closely-allied species, and when produced
they are sterile, and are not capable of reproducing their like.
In these cases, therefore, we may take this as a most satisfactory element in the definition of "species."  The sterility,
however, of hybrids is not universal, even amongst the higher
animals; and amongst plants no doubt can be entertained but
that the individuals of species universally admitted to be distinct are capable of mutual fertilisation; the hybrid progeny
thus produced being likewise fertile, and capable of reproducing similar individuals. That this fertility is often irregular,
and may be destroyed in a few generations, admits of explanation, and hardly alters the significance of these undoubted facts.
Upon the whole, then, it seems in the meanwhile safest to
adopt a definition of species which implies no theory, and
does not include the belief that the term necessarily expresses
a fixed and permanent quantity. Species, therefore, may be
defined as an assemblage of individuals which resemble each other
in their essential characters, are able, dilrectly or inZirectlly, to produce fertile individuals, and which do not (as far as human observation goes) giz'e rise to individuals which vary from  the
general type tlzrouah more t/han certain definit litmits.  The production of occasional monstrosities does not, of course, invalidate this definition.
Genus is a term applied to groups of species which possess
a community of essential details of structure. A genus may
include a single species only, in cases where the combination
of characters which make up the species are so peculiar that




24              MANUAL OF ZOOLOGY.
no other species exhibits similar structural characters; or, on
the other hand, it may contain many hundreds of species.
Families are groups of genera which agree in their general
characters. According to Agassiz, they are divisions founded
upon peculiarities of " form as determined by structure."
Orders are groups of families related to one another by
structural characters common to all.
Classes are larger divisions, comprising animals which are
formed upon the same fundamental plan of structure, but differ
in the method in which the plan is executed (Agassiz).
Sub-kingd,-oms are the primary divisions of the animal kingdom, which include all those animals which are formed upon
the same structural or morphological type, irrespective of the
degree to which specialisation of function may be carried.
Impossibility of a Linear Classication.-It has sometimes
been thought that the animal kingdom can be arranged in a
linear series, every member of the series being higher in point
of organisation than the one below it. As we have seen, however, the status of any given animal depends upon two conditions-one its morphological type, the other the degree to
which specialisation of function is carried. Now, if we take
two animals, one of which belongs to a lower morphological
type than the other, no degree of specialisation of function,
however great, will'place the former above the latter, as far as
its type of structure is concerned, though it may make the
former a more highly organised animal.  Every Vertebrate
animal, for example, belongs to a higher morphological type
than every Mollusc; but the higher ALolluscs, such as cuttlefishes, are much more highly organised, as far as their type is
concerned, than are the lowest Vertebrata. In a linear classification, therefore, the cuttle-fishes should be placed above the
lowest fishes-such as the lancelet-in spite of the fact that
the type upon which the latter are constructed is by far the
highest of the two.
It is obvious, therefore, that a linear classification is not
possible, since the higher members of each sub-kingdom are
more highly organised than the lower forms of the next subkingdom in the series, at the same time that they are constructed upon a lower morphological type.
I O. REPRODIUCTION.
Reproduction is the pirocess whereby new individuals are
generated and the perpetuation of. the species insured. The
methods in which this end may be attained exhibit a good




REPRODUCTION.                     25
deal of diversity, but they may be all considered under two
heads.
I. Sexual Reproduction. - This consists essentially in the
production of two distinct elements, a germ-cell or ovum, and
a sperm-cell or spermatozoid, by the contact of which the
ovum-now said to be "fecundated "-is enabled to develop
itself into a new individual.  As a rule, the germ-cell is produced by one individual (female) and the spermatic element
by another (male); in which case the sexes are said to be distinct, and the species is said to be "dioecious."  In other
cases the same individual has the power of producing both the
essential elements of reproduction; in which case the sexes
are said to be united, and the individual is said to be "hermaphrodite," " androgynous," or "moncecious."  In the case
of hermaphrodite animals, however, self-fecundation-contrary
to what might have been expected-rarely constitutes the reproductive process; and, as a rule, the reciprocal union of two
such individuals is necessary for the production of young.
Even amongst hermaphrodite plants, where self-fecundation
may, and certainly does, occur, provisions seem to exist by
which perpetual self-fertilisation is prevented, and the influence
of another individual secured at intervals.  Amongst the
higher animals sexual reproduction is the only process whereby
new individuals can be generated.
II. Non-sexual Replroduction. —Amongst the lower animals
fresh beings may be produced without the contact of an ovum
and a spermatozoid; that is to say, without any true generative
act. The processes by which this is effected vary in different.animals, and are all spoken of as forms of "asexual" or
"agamic" reproduction.  As we shall see, however, the true
"individual" is very rarely produced otherwise than sexually,
and most forms of agamic reproduction are really modifications of growth.
a. Gemnmatign and Fission.-Gemmation, or budding, consists in the production of a bud, or buds, generally from the
exterior, but sometimes from the interior, of the body of an
animal, which buds are developed into independent beings,
which may or may not remain permanently attached to the
parent organism.  Fission differs from  gemmation solely in
the fact that the new structures in the former case are produced by a division of the body of the original organism into
separate parts, which may remain in connection, or may undergo detachment.
The simplest form of gemmation, perhaps, is seen in the
power possessed by certain animals of reproducing parts of




26             MANUAL OF ZOOLOGY.
their bodies which they may have lost. Thus, the Crustacea
possess the power of reproducing a lost limb, by means of a
bud which is gradually developed till it assumes the form and
takes the place of the missing member.  In these cases, however, the process is not in any way generative, and the product of gemmation can in no sense be spoken of as a distinct
being (or zobid).
Another form of gemmation may be exemplified by what
takes place in the Foraminifera, one of the classes of the
Protozoa. The primitive form of a Foraminifer is simply a
little sphere of sarcode, which has the power of secreting from
its outer surface a calcareous envelope; and this condition
may be permanently retained (as in Lagena).  In other cases
a process of budding or gemnmation takes place, and the primitive mass of sarcode produces from itself, on one side, a
second mass exactly similar to the first, which does not detach
itself from its parent, but remains permanently connected with
it. This second mass repeats the process of gemmation as
before, and this goes on- all the segments remaining attached
to one another —until it body is produced, which consists of
a number of little spheres of sarcode in organic connection
with one another, and surrounded by a shell, often of the
most complicated description. In this case, however, the
buds produced by the primitive spherule are not only not
detached, but they can only remotely be regarded as independent beings. They are, in all respects, identical with.the primordial segment, and it is rather a case of " vegetative" repetition of similar parts.
Another form of gemmation is exhibited in such an organism as the common sea-mat (Flustra), which is a composite
organism composed of a multitude of similar beings, each of
which inhabits a little chamber, or cell; the whole forming a
structure not unlike a sea-weed in appearance. This colony is
produced by gemmation from a single primitive being (" polypide "), which throws out buds, each of which repeats the process, apparently almost indefinitely. All the buds remain in
contact and connected with one another, but each is, nevertheless, a distinct and independent being, capable of performing
all the functions of life. In this case, therefore, each one of
the innumerable buds becomes an independent being, similar
to, though not detached from, the organism which gave it
birth. This is an instance of what is called "' continuous gemmation."
In other cases-as in the common fresh-water polype or
Hydra-the buds which are thrown out by the primitive or



REPRODUCTION.                     27
ganism become developed into creatures exactly resembling
the parent, but, instead of remaining permanently attached,
and thus giving rise to a compound organism, they are detached to lead an entirely independent existence. This is a
simple instance of what is termed " discontinuous gemmation."
The method and results of fission may be regarded as essentially the same as in the case of gemmation. The products of
the division of the body of the primitive organism may either
remain undetached, when they will give rise to a composite
structure (as in many corals), or they may be thrown off and
live an independent existence (as in some of the Hydrozoa).
We are now in a position to understand what is meant,
strictly speaking, by the term "individual." In zoological language, an individuial is defined as " equal to the total result of
the development of a single ovum."  Amongst the higher animals
there is no difficulty about this, for each ovum gives rise to no
more than one single being, which is incapable of repeating itself in any other way than by the production of another ovum;
so that an individual is a single animal. It is most important, however, to comprehend that this is not necessarily or
always the case. In such an organism as the sea-mat, the
ovum gives rise to a primitive polypide, which repeats itself by
a process of continuous gemmation until an entire colony is
produced, each member of which is independent of its fellows,
and is capable of producing ova. In such a case, therefore,
the term "individual" nmu.t be applied to the entire colony,
since this is the result of the development of a single ovum.
The separate beings which compose the colony are technically
called " zo6ids." In like manner the Hydra, which produces
fresh and independent Hydrne by discontinuous gemmation, is
not an " individual," but is a zodid.  Here the zobids are not
permanently united to one another, and the "individual" Hydra
consists really of the primitive Hydra, plus all the detached
Hydrae to which it gave rise. In this case, therefore, the "individual" is composed of a number of disconnected and wholly
independent beings, all of which are the result of the development of a single ovum. It is to be remembered that both the
parent zobid and the " produced zo6ids " are capable of giving
rise to fresh Hvdrae by a true generative process. It must
also be borne in mind that this production of fresh zobids by a
process of gemmation is not so essentially different to the true
sexual process of reproduction as might at first sight appear,
since the ovum itself may be regarded merely as a highly specialised bud. In the Hydra, in fact, where the ovum is produced as an external process of the wall of the body, this like3




28             MANUAL OF ZOOI,OGY.
ness is extremely striking. The ovarian bud, however, differs
from the true gemmae or buds in its inability to develop itself
into an independent organism, unless previously brought into
contact with another special generative element. The only
exceptions to this statement are in the rare cases of true " parthenogenesis," to be subsequently alluded to.
b. Reproduction by Internal Gemnmation.-Before considering
the phenomena of " alternate generations," it will be as well to
glance for a moment at a peculiar form of gemmation exhibited by some of the Polyzoa, which is in some respects intermediate between ordinary discontinuous'gemmation and
alternation of generations. These organisms are nearly allied
to the sea-mat, already spoken of, and, like it, can reproduce
themselves by continuous gemnmation (forming colonies), by a
true sexual process, and rarely by fission. In addition to all
these methods they can reproduce themselves by the formation
of peculiar internal buds, which are called "statoblasts." These
buds are developed upon a peculiar cord, which crosses the
body-cavity, and is attached at one end to the fundus of the
stomach. When mature they drop off from this cord, and lie
loose in the cavity of the body, whence they are liberated on
the death of the parent organism. When thus liberated, the
statoblast, after a longer or shorter period, ruptures and gives
exit to a young Polyzobn, which has essentially the same
structure as the adult. It is, however, simple, and has to
undergo a process of continuous gemmation before it can
assume the compound form proper to the adult.
As regards the nature of these singular bodies, "the invariable absence of germinal vesicle and germinal spot, and
their never exhibiting the phenomena of yelk-cleavage, independently of the conclusive fact that true ova and ovary occur
elsewhere in the same individual, are quite decisive against
their being eggs. We must then look upon them as gemmtz
peculiarly encysted, and destined to remain for a period in a
quiescent or pupa-like state."-(Allman.)
c. Alternation of Generations.-In the case of the Hydra and
the sea-mat, which we have considered above, fresh zobids
are produced by a primordial organism by gemmation; the
beings thus produced (as well as the parent) being capable
not only of repeating the gemmiparous process, but also of
producing new individuals by a true generative act.  We
have now to consider a much more complex series of phenomena, in which the organism which is developed from the
primitive ovum produces by gemmation two sets of zobids, one
of which is destitute of sexual organs, and is capable of per



ALTERNATION OF GENERATIONS.                29
forming no other function than that of nutrition, whilst the
other is provided with reproductive organs, and is destined
for the perpetuation of the species. In the former case the
produced zobids all resembled each other, and the parent
organism which gave rise to them; in the latter case, the produced zo6ids are often utterly unlike each other and unlike the
parent, since their functions are entirely different.
The simplest form of the process is seen in certain of the
Hydroid Polypes, such as Sertularia.  The ovum of Sertularia is a free-swimming ciliated body, which, after a short
locomotive existence, attaches itself to some submarine object,
develops a mouth and tentacles, and commences to produce zobids like itself by a process of continuous gemmation.
These remain permanently attached to one another, with the
result that a compound organism is produced, consisting of a
number of zobids, or "polypites," organically connected together, but enjoying an independent existence. None of the
zodids, however, are provided with sexual organs; and though
there is theoretically no limit to the size which the colony may
reach by gemmation, its buds are not detached, and the
species would therefore die out, unless some special provision
were made for its preservation.  Besides these nutritive
zobids, however, other buds are produced which differ considerably.in appearance from the former, and which have the
power of generating the essential elements of reproduction.
These generative zodids derive their nourishment from the
materials collected by the nutritive zodids, but only live until
the ova are matured in their interior and liberated, when
they disappear. The ova thus produced become free-swimming ciliated bodies, such as the one with which the cycle
began.
In this case, therefore, the "individual" Sertularia consists of a series of nutritive zo6ids, collectively called the
"trophosome," and another series of reproductive zo6ids, collectively called the "gonosome," the entire series often remaining in organic connection.
In other forms nearly allied to Sertularia (such as Coryne)
the process advances a step further. In Coryne the genera-'ive buds, or zobids, do not produce the reproductive elements as long as they remain attached to the parent colony;
but they require a preliminary period of independent existence.  For this purpose they are specially organised, and
when sufficiently matured they are detached from the
stationary colony. The generative zobid now appears as an
entirely independent being, described as a species of jelly-fish




30              MANUAL OF ZOOLOGY.
(or Medusa) under the name of Sarsia. It consists of a bellshaped disc, by means of which it is enabled to swim freely;
from the centre of this disc depends a nutritive process, with
a mouth and digestive cavity, whereby the organism is able to
increase considerably in size. The substance of the disc is
penetrated by a complex system of canals, and from its margin
hangs a series of tentacular processes. After a period of independent locomotive existence, the Medusa attains its full
growth, when it develops ova and spermatozoa. By the contact of these embryos are produced; but these, instead of
resembling the jelly-fish by which they were immediately generated, proceed to develop themselves into the fixed Hydroid
colony by which the Medusa was originally produced.
Still more extraordinary phenomena have been discovered
in other Hydrozoa, as in many of the Lucernarida.  In
these the ovum gives rise (as in Sertularia) to a locomotive
ciliated body, which ultimately fixes itself, becomes trumpetshaped, and develops a mouth and tentacles at its expanded
extremity, when it is known as the "hydra-tuba," from its
resemblance to the fresh-water polype, or Hydra. The hydratuba has the power of multiplying itself by gemmation, and
it can produce large colonies in this way; but it does not
obtain the power of generating the essential elements of
reproduction. Under certain circumstances,'however, the
hydra-tuba enlarges, and, after a series of preliminary changes,
divides by transverse fission into a number of segments, each
of which becomes detached and swims away. These liberated
segments of the little hydra-tuba (it is about half an inch in
height) now live as entirely independent beings, which were
described, by naturalists as distinct animals, and were called
Ephyrze. They are provided with a swimming - bell, or
" umbrella," by means of which they propel themselves through
the water, and with a mouth and digestive cavity.  They
now lead an active life, feeding eagerly, and attaining in some
instances a perfectly astonishing size (the Medusoids of some
species are several feet in circumference).  After a while
they develop the essential elements of reproduction, and
after the fecundation and liberation of their ova they die.
The ova, however, are not developed into the free-swimming
and comparatively gigantic jelly-fish by which they were
immediately produced, but into the minute, fixed, sexless
hydra-tuba.
We thus see that a small, sexless zo6id, which is capable of
multiplying itself by gemmation, produces by fission several
independent locomotive beings, which are capable of nourish



PAR rHENOGENESIS.                 31
ing themselves and of performing all the functions of life. In
these are produced generative elements, which give rise by
their development to the little fixed creature with which the
series began.
To the group of phenomena of which the above are examples,
the name " alternation of generations " was applied by Steenstrup; but the name is not an appropriate one, since the
process is truly an alternation of generation with gemmation
or fission. The only generative act takes place in the reproductive zo6id, and the production of this from the nutritive
zo6id is a process of gemmation or fission, and not a process of generation. The "individual," in fact, in all these
cases, must be looked upon as a double being composed of two
factors, both of which lead more or less completely independent lives, the one being devoted to nutrition, the other to
reproduction.  The generative being, however, is in many
cases not at first able to mature the sexual elements, and is
therefore provided with the means necessary for its growth
and nourishment as an independent organism. It must also
be remembered that the nutritive half of the " individual " is
usually, and the generative half sometimes, compound-that is
to say, composed of a number of zo6ids produced by continuous gemmation; so that the zoological individual in these
cases becomes an extremely complex being.
These phenomena of so-called " alternation of generations,"
or "metagenesis," occur in their most striking form amongst
the Hydrozoa; but they occur also amongst many of the intestinal worms (Entozoa), and amongst some of the Tunicata
(Molluscoida).
d. Partzenogenesis. —"Parthenogenesis" is the term employed
to designate certain singular phenomena, resulting in the
production of new individuals by virgin females without the
intervention of a male. By Professor Owen, who first employed the term, parthenogenesis is applied also to the
processes of gemmation and fission, as exhibited. in sexless
beings or in virgin females; but it seems best to consider
these phenomena separately. Strictly, the term parthenogenesis
ought to be confined to the production of new individuals
from virgin females by means of ova, which are enabled to
develop themselves without the contact of the male element.
The difficulty in this definition is found in framing an exact
definition of an ovum, such as will distinguish it from an internal gemma or bud. No body, however, should be called
an "ovum" which does not exhibit a germinal vesicle and
germinal spot, and which does not exhibit the phenomenon




32             MANUAL OF ZOOLOGY.
known as segmentation of the yelk. Moreover, ova are almost
invariably produced by a special organ, or ovary.
As examples of parthenogenesis we may take what occurs in
plant-lice (Aphides) and in the honey-bee; but it will be seen
that in neither of these cases are the phenomena so-unequivocal, or so well ascertained, as to justify a positive assertion
that they are truly referable to parthenogenesis in the above
restricted sense of the term.
The Aphides, or plant-lice, which are so commonly found
parasitic upon plants, are seen towards the close of autumn to
consist of male and female individuals. By the sexual union
of these true ova are produced, which remain dormant through
the winter. At the approach of spring these ova are hatched;
but instead of giving birth to a number of males and females,
all the young are of one kind, variously regarded as neuters,
virgin females, or hermaphrodites. Whatever their true nature
may be, these individuals produce viviparously a brood of
young which resemble themselves; and this second generation,
in like manner, produces a third,-and so the process may be
repeated, for as many as ten or more generations, throughout
the summer. When the autumn comes on, however, the viviparous Aphides produce —in exactly the same manner-a final
brood; but this, instead of being composed entirely of similar
individuals, is made up of males and females. Sexual union
now takes place, and ova are produced and fecundated in the
ordinary manner.
The bodies from which the young of the viviparous Aphides
are produced are variously regarded as internal buds, as " pseudova" (i.e., as bodies intermediate between buds and ova), and
as true ova.
Without entering into details, it is obvious that there is only
one explanation of these phenomena which will justify us in
regarding the case of the viviparous Aphides as one of true
parthenogenesis, as above defined.  If, namely, the spring
broods are true females, and the bodies which they produce in
their interior are true ova, then the case is one of genuine parthenogenesis, for there are certainly no males. The case might
still be called one of parthenogenesis, even though the bodies
from which these broods are produced be regarded as internal
buds, or as " pseudova;" for a true ovum is essentially a bud.
If, however, Balbiani be right, and the viviparous Aphides are
really hermaphrodite, then, of course, the phenomena are of a
much less abnormal character.
In the second case of alleged parthenogenesis which we are
about to examine-namely, in the honey-bee-the phenomena




PARTHENOGENESIS.                   33
which have been described cannot be said to be wholly free
from doubt. A hive of bees consists of three classes of individuals-r. A " queen," or fertile female; 2. The "workers," which
form the bulk of the community, and are really undeveloped
or sterile females; and, 3. The " drones," or males, which are
only produced at certain times of the year. We have here
three distinct sets of beings, all of which proceed from a single
fertile individual, and the question arises, In what manner are
the differences between these produced? At a certain period
of the year the queen leaves the hive, accompanied by the
drones (or males), and takes what is known as her "nuptial
flight" through the air..In this flight she is impregnated by
the males, and it is immaterial whether this act occurs once in
the life of the queen, or several times, as asserted by some.
Be this as it may, the queen, in virtue of this single impregnation, is enabled to produce fresh individuals for a lengthened
period, the semen of the males being stored up in a receptacle
which communicates by a tube with the oviduct, from which it
can be shut off at will. The ova which are to produce workers
(undeveloped females) and queens (fertile females) are fertilised on their passage through the oviduct, the semen being
allowed to escape into the oviduct for this purpose. The subsequent development of these fecundated ova into workers or
queens depends entirely upon the form of the cell into which
the ovum is placed, and upon the nature of the food which is
supplied to the larva. So far there is no doubt as to the nature
of the phenomena which are observed. It is asserted, however, by Dzierzon and Siebold, that the males or drones lare
produced by the queen from ova which she does not allow to
come into contact with the semen as they pass through the
oviduct. This assertion is supported by the fact that if the
communication between the receptacle for the semen and the
oviduct be cut off, the queen will produce nothing but males.
Also, in crosses between the common honey-bee and the Ligurian bee, the queens and workers alone exhibit any intermediate
characters between the two forms, the drones presenting the unmixed characters of the queen by whom they were produced.
If these observations are to be accepted as established-and,
upon the whole, there can be no hesitation in accepting them
as in the main correct-then the drones are produced by a true
process of parthenogenesis; but some observers maintain that
the development of any given ovum into a drone is really due
-as in the case of the queens and workers-to the special circumstances under which the larva is brought up."
* In the case of Polistes Gallica, Von Siebold appears to have proved




34               MANUAL OF ZOOLOGY.
There are various other cases in which parthenogenesis is
said to occur, but the above will suffice to indicate the general
character of the phenomena in question.  The theories of parthenogenesis appear to be too complex to be introduced here;
and there is the less to regret in their omission, as naturalists
have not yet definitely adopted any one explanation of the
phenomena to the exclusion of the rest.
First Law of Quatrefages.-From the phenomena of asexual
reproduction in all its forms, M. de Quatrefages has deduced
the following generalisation:" The formation of new individuals may take place, in some
-nstances, by gemmation from, or division of, the parent-being;
but this process is an exhaustive one, and cannot be carried
out indefinitely. When, therefore, it is necessary to insure the
continuance of the species, the sexes must present themselves,
and the germ and sperm must be allowed to come in contact
with one another."
It should be added that the act of sexual reproduction,
though it insures the perpetuation of the species, is very destructive to the life of the individual. The formation of the
essential elements of reproduction appears to be one of the
highest physiological acts of which the organism is capable,
and it is attended with a corresponding strain upon the vital
energies.  In no case is this more strikingly exhibited than in
the majority of insects, which pass the greater portion of their
existence in a sexually immature condition, and die almost
immediately after they have become sexually perfect, and
have consummated the act whereby the perpetuation of the
species is secured.
II. DEVELOPMENT, TRANSFORMATION, AND METAMORPHOSIS.
Development is the general term applied to all those changes
which a germ undergoes before it assumes the characters of
the perfect individual; and the chief differences which are observed in the process as it occurs in different animals consists
simply in the extent to which these changes are external and
visible, or are more or less completely concealed from view.
For these differences the terms " transformation " and "metamorphosis " are employed; but they must be regarded as essen.
tially nothing more than variations of development.
beyond reasonable doubt that the males are produced by a process of parthenogenesis. Landois, however, asserts that the eggs of insects are of no
sex, that sex is only developed in the larva after its emergence from the
egg, and that in each individual larva the sex is determined wholly by the
nature of the food upon which it is brought up; abundant nourishment
producing females, and scanty diet giving rise to males.




DEVELOPMENT.                      35
Tr-ansformation is the term employed by Quatrefages to designate "the series of changes which every germ undergoes in
reaching the embryonic condition; those which we observe in
every creature still within the egg; those, finally, which the
species born in an imperfectly developed state present in the
course of their external life."
Metamorphosis is defined by the same author as including
the alterations which are "undergone after exclusion from the
egg, and which alter extensively the general form and mode of
life of the individual."
Though by no means faultless, these terms are sufficiently
convenient, if it be remembered that they are merely modifications of development, and express differences of degree and
not of kind.  An insect, such as a butterfly, is the best illustration of what is meant by these terms. All the changes
which are undergone by a butterfly in passing from the fecundated ovum to the condition of an imago, or perfect insect,
constitute its development. The egg which is laid by a butterfly undergoes a series of changes which eventuate in its giving birth to a caterpillar, these preliminary changes constituting its transformation.  The caterpillar grows rapidly, and
after several changes of skin becomes quiescent, when it is
known as a "chrysalis."  It remains for a longer or shorter
time in this quiescent and apparently dead condition, during
which period developmental changes are going on rapidly in
its interior. Finally, the chrysalis ruptures, and there escapes
from it the perfect winged insect. To these changes the term
metamorphosis is rightly applied.  These changes, however, do
not differ in kind from the changes undergone by a Mammal;
the difference being that in the case of a Mammal the ovum is
retained within the body of the parent, where it undergoes
the necessary developmental changes, so that at birth it has
little to do but grow, in order to be converted into the adult
animal.
From these considerations we arrive at the second law laid
down by Quatrefages:-" Those creatures whose ova-owing to
an insufficient supply of nutritious contents, and an incapacity
on the part of the mother to provide for their complete develQpment within her own substance-are rapidly hatched,
give birth to imperfect offspring, which, in proceeding to their
definitive characters, undergo several alterations in structure
and form, known as metamorphoses."
Retrograde Development. —Ordinarily speaking, the course
of development is an ascending one, and the adult is more
highly organised than the young; but there are cases in which




36               MANUAL OF ZOOLOGY.
there is an apparent reversal of this law, and the adult is to
all appearance a degraded form when compared with the
embryo.  This phenomenon is known as "retrograde" or
" recurrent " development; and well-marked instances are found
amongst the Cirripedia and Lernaee, both of which belong to
the Crustacea.
Thus, in the Cirripedes (acorn-shells, &c.) and in the
parasitic Lernoeae the embryo is free-swimming and provided
with organs of vision and sensation, being in most respects
similar to the permanent condition of certain other Crustacea,
such as the Copepods.  The adult, however, in both cases, is
degraded into a more or less completely sedentary animal,
more or less entirely deprived of organs of sense, and leading
an almost vegetative life. As a compensation, reproductive
organs are developed in the adult, and it is in this respect
superior to the locomotive, but sexless, larva.
12. SPONTANEOUS GENERATION.
Spontaneous or Equivocal generation is the term  applied
to the alleged production of living beings without the preexistence of germs of any kind, and therefore without the
pre-existence of parent organisms. The question is one which
has been long and closely disputed, and is far from being
settled; so that it will be sufficient to indicate the facts upon
which the theory rests.
If an animal or vegetable substance be soaked in hot or
cold water, so as to make an organic infusion, and if this infusion be exposed for a sufficient length of time to the air, the
following series of changes is usually observed:I. At the end of a longer or shorter time, there forms upon
the surface of the infusion a thin scum, or pellicle, which,
when examined microscopically, is found to consist of an incalculable number of extremely minute molecules.
2. In the next stage these molecules appear, many of them,
to have increased in size by endogenous division, till they form
short staff-shaped filaments, called " bacteria." These increase
in length by the same process until we get long filamentous
bodies produced, which are termed "vibriones.")   Both the
bacteria and the vibrios now exhibit a vibratile or serpentine
movement through the surrounding fluid.
3. After a varying period, the bacteria and vibrios become
* By some authorities it is believed that the bacteria are produced by the
fusion together of the primitive molecules in twos and threes; and that the
vibrios are produced out of the bacteria by the addition of fresh molecules
to the extremities of the latter, or by their uniting with one another.




SPONTANEOUS GENERATION.                37
motionless, and disintegrate so as to produce again a finely
molecular pellicle.
4. Little spherical bodies. now appear, each of which is
provided with a vibratile cilium with which it moves actively
through the infusion. (Monas lens.)
5. Varied forms of ciliated Infusoria-some which possess
a mouth and are otherwise highly organised-make their
appearance in the fluid.
The above is the general sequence of the phenomena which
have been observed, and the following are the two theories
which have been advanced to account for them:a. By the advocates of spontaneous generation, or "Heterogeny," it is affirmed that the Infusoria, which finally appear in
the infusion, are produced spontaneously out of the molecular
pellicle, the molecules of which are also of spontaneous origin,
and are not derived from any pre-existing germs.
b. By the " panspermists," or the opponents of spontaneous
generation, it is alleged, on the other hand, that the production of Bacteria, Vibrios, Monads, and Infusoria, in organic
infusions, is due simply to the fact that the atmosphere, and
probably the fluid itself, is charged with innumerable germstoo minute, perhaps, to be always detectable by the microscope
-which, obtaining access to the fluid, and finding there favour
able conditions, are developed into living beings.
A large number of elaborate experiments have been carried
out to prove that atmospheric air is absolutely necessary for
the production of these living beings, and that if the air be
properly purified by passage through destructive chemical
reagents, no such organisms will be produced, provided that
the infusion have been previously boiled. As the results of
all these experimental trials have hitherto proved more or less
contradictory, it is unnecessary to enter into the question
further, and it will be sufficient to indicate the following general
considerations:a. The primary molecules which appear in the fluid are extremely minute, and if they are developed from germs, these
may be so small as to elude any power of the microscope yet
known to us. As they subsequently become converted into
bacteria and vibrios, and as there can be little dispute as to
these being truly living organisms, we are obliged to believe
that they must have had some definite origin. It appears,
however, to be hardly philosophical to assume that they fornl
themselves out of the inorganic materials of the infusion; since
this implies the sudden appearance, or creation, of new force,
for which there seems to be no means of accounting.




38              MANUAL OF ZOOLOGY.
b. The nature of the vibrios and bacteria must be looked
upon as quite uncertain. To say the least of it, they are quite
as likely to be. plants as animals;. and the most probable hypothesis would place the former near the filamentous Confervae,
or would regard them as the mycelium of various species of
Moulds (PeniciZliumr).
c. What has been said above with regard to the origin of
the bacteria and vibrios applies equally to the origin of the
Monads, which appear in the infusion subsequently to the
death of the vibrios.
d. These Monads, as shown by recent researches, are probably to be looked upon as the embryonic, or larval, forms of
the higher Infusoria which succeed them.
e. Many of the Infusoria which finally appear are of a
comparatively high grade of organisation, being certainly the
highest of the Protozoa, and being placed by some competent
observers in' the neighbourhood of the Trematode Worms
(Annuloida). It is therefore very unlikely that these should
be generated spontaneously; since, if this ever occurs, it is
reasonable to suppose that the creatures thus produced will
be of the lowest possible organisation (such as the Gregarinidoe
or the Monera, for example), and will be far below the Infusoria
in point of structure.
f  The reproductive process in many of these same Infusoria
is perfectly well known, and it consists either in a true sexual
process, for which proper organs are provided (as in Paramcecium), or in a process of gemmation or fission. It is therefore improbable that they should be generated in the manner
maintained by the heterogenists, since this mode of reproduction would appear to be superfluous.
g. In the absence of any direct proof to the contrary, it is
safer to adopt an explanation of the observed phenomena
which does not have recourse to laws with which we are as
yet unacquainted. Thus, it is not at variance with any known
law to suppose that the primary molecules are the result ot
the development of germs which find in the inorganic infusion
*a suitable nidus; that these primary molecules and the vibrios
which they produce are referable to the Protophyta, and
should probably be placed near the filamentous Confervae;
that by the death of these vegetable organisms the fluid is
prepared for the reception and development of the germs of
the Protozoa, for which the former serve as jabulum; and
that many of the forms which are observed are the larval
stages of the higher Infusoria.*
* Recent researches, especially those of Dr Bastian, have established




ORIGIN  OF SPECIES.                      39
I3. ORIGIN OF SPECIES.
It is impossible here to do more than merely indicate in the
briefest manner the two fundamental ideas which are at the
bottom of all the various theories as to the origin of species.
The opinions of scientific men are still divided upon this subject; and it will be sufficient to give an outline of the two
leading theories, without adducing any of the reasoning upon
which they are based.
I. Doctrine of Special Creation. - On this doctrine of the
origin of species it is believed that species are immutable productions, each of which has been'specially created at some
point within the area in which we now find it, to meet the external conditions there prevailing, subsequently spreading from
this spot as far as the conditions of life were suitable for it.
II. Doctrine of Development.-On the other hand, it is believed that species are not permanent and immutable, but that
they "undergo modification, and that the existing forms of life
are the descendants by true generation of pre-existing forms."
-(Darwin.)
On Lamarck's theory of the development of species, the
means of modification were ascribed to the action of external
physical agencies, the inter-breeding of already existing forms,
and the effects of habit.
The doctrine of the development of species by variation and'
some new facts as to the possibility of Heterogeny, but they can by n'o
means be said to have settled the question, if only upon the ground that
they require confirmation by other experimentalists. The chief fact which
appears to have been established upon a tolerably firm basis is, that living
beings, vegetable or animal, may make their appearance in organic infusions which have been subjected to a temperature of considerably over
the boiling-point, even though the said infusions have been hermetically
sealed in a flask from which all atmospheric air has been previously withdrawn. The chief deduction which appears to flow from this-assuming
its correctness-is, that there are low organisms which can exist, for a
certain length of time at any rate, with an extremely small amount of air;
for it is to be remembered that the production of a theoretically perfect
vacuum is probably practically impossible. If it were conceded, in fact,
that a perfect vacuum had been formed in the experiments in question, the
sole result would be that we should have to alter all.our beliefs as to the
conditions under wlich life is a possibility.  The only tangible result of
these experiments, so far, is, that any.supposed " pre-existent germs " must
have been contained, if present at all, in the infinitesimal portion of air
which could not be expelled from the flasks experimented on; or, they
must have been able' to withstand without injury a temperature of over
212~. Neither of these hypotheses is wholly incredible; but the question
ought to be regarded as still sub judice, and there is grave doubt as to the
reliability and accuracy of the experiments above alluded to.




40              MANUAL OF ZOOLOGY.
natural selection -propounded by Darwin, and commonly
known as the Darwinian theory-is based upon the following
fundamental propositions:I. The progeny of all species of animals and plants exhibit
variations amongst themselves in all parts of their organisation; no two individuals being exactly alike. In other words,
in every species the individuals tend by variation to diverge
from the parent-type, in some particular or other.
2. These variations can be transmitted to future generations
under certain definite and discoverable laws of inheritance.
3. By artificial selection and breeding from individuals possessing any particular variation, man, in successive generations,
can produce a breed in which the variation is permanent; the
races thus produced being often as widely different as are
distinct species of wild animals.
4. The world in which all living beings are placed is one
not absolutely unchanging, but is liable to subject them to very
varying conditions.
5. All animals and plants give rise to more numerous young
than can by any possibility be preserved.
6. As these young are none of them exactly alike, a process
of "Natural Selection" will ensue, whereby those individuals
which possess any variation favourable to the peculiarities of
the life of the species will be preserved. Those individuals
which do not possess such a favourable variation will be placed
at a disadvantage in the " struggle for existence," and will tend
to be gradually exterminated.
7. Other conditions remaining the same, the individuals
which survive in the struggle for existence will transmit the
variations, to which their preservation is due, to future generations.
8. By a repetition of this process " varieties " are first established; these become permanent, and "races " are produced;
finally, in the lapse of time, the differences become sufficiently
great to constitute distinct species.
I4. DISTRIBUTION.
Under this head come all the facts which are concerned with
the external or objective relations of animals-that is to say,
their relations to the external conditions in' which they are
placed.
The geographical distribution of animals is concerned with
the determination of the areas within which every species of
animal is at the present day confined. Some species are found
almost everywhere, when they are said to be " cosmopolitan;"




DISTRIBUTION.                     41
but, as a rule, each species is confined to a limited and definite
area. Not only are species limited in their distribution, but it
is possible to divide the globe into a certain number of geographical regions or "zoological provinces," each of which is
characterised by the occurrence in it of certain associated forms
of animal life. It is to be remembered, however, that the
zoological provinces of the present day by no means correspond with those of former periods, and that they have only
existed as such since comparatively recent times.
The vertical or bathymetrical distribution of animals relates
to the limits of depth within which each marine species of
animals is confined. As a rule it is found that each species
has its own definite bathymetrical zone, and that its existence
is difficult or impossible at depths greater or less than those
comprised by that zone. Generalising on a large number of
facts, naturalists have been able to lay down and name certain
definite zones, each of which has its own special fauna.
The four following zones are those generally accepted:I. The Littoral zone, or the tract between tide-marks.
2. The Laminarian zone, from low water to 15 fathoms.
3. The Coralline zone, from I5 to 50 fathoms.
4. The deep-sea Coral zone, 50 to Ioo fathoms or more.
5. To these must now be certainly added a fifth zone, extending from Ioo fathoms to a depth of 2500 fathoms or more.
Recent researches, however, have rendered it certain that
after a certain depth, say Ioo fathoms, the bathymetrical distribution of animals is conditioned not by the depth, but by
the tenmperature of the water at the bottom of the sea. Similar
forms, namely, are always found inhabiting areas in which the
bottom-temperature is the same, wholly irrespective of the
dep.th of water in the particular locality in question. The
supply of food, also, and the nature of the habitat, are important
elements of the case. In the light, therefore, of these recent
facts, it would perhaps be advisable to adopt the views of Mr
Gwyn Jeffreys, and to consider that there are only two principal bathymetrical zones-namely, the littoral and the submarine.
In addition to the preceding forms of distribution, the
zoologist has to investigate the condition and nature of animal
life during past epochs in the history of the world
The laws of distribution in time, however, are, from  the
nature of the case, less perfectly known than are the laws of
lateral or vertical distribution, since these latter concern beings
which we are able to examine directly. The following are the
chief facts which it is necessary for the student to bear in mind:




42               MANUAL OF ZOOLOGY.
I. The rocks which compose the crust of the earth have
been formed at successive periods, and may be roughly divided into aqueous or sedimentary rocks, and igneous rocks.
2. The igneous rocks are produced by the agency of heat,
are mostly unstratified (i.e., are not deposited in distinct layers
or strata), and, with few exceptions, are destitute of any traces
of past life.
3. The sedimentary or aqueous rocks owe their origin to
the action of water, are stratzjfed (i.e., consist of separate layers
or strata), and mostly exhibit "fossils "-that is to say, the
remains or traces of animals or plants which were in existence
at the time when the rocks were deposited.
4. The series of aqueous rocks is capable of being divided
into a number of definite groups of strata, which are technically
called "formations."
5. Each of these definite rock-groups, or "formations," is
characterised by the occurrence of an assemblage of fossil remains more or less peculiar and confined to itself.
6. The majority of these fossil forms are " extinct "-that is
to say, they do not admit of being referred to any species at
present existing.
7. No fossil, however, is known, which cannot be referred
to one or other of the primary subdivisions of the Animal
Kingdom, which are represented at the present day.
8. When a species has once died out, it never reappears.
9. The older the formation, the greater is the divergence
between its fossils and the animals and plants now existing on
the globe.
Io. All the known formations are divided into three great
groups, termed respectively Palaeozoic or Primary, Mesozoic
or Secondary, and Kainozoic or Tertiary.
The Palaeozoic or Ancient-life period is the oldest, and is
characterised by the marked divergence of the life of the period
from all existing forms.
In the Mesozoic or Middle-life period, the general facies of
the fossils approaches more nearly to that of our existing fauna
and flora; but-with very few exceptions-the characteristic
fossils are all specifically distinct from all existing forms.
In the Kainozoic or New-life period, the approximation of
the fossil remains to existing living beings is still closer, and
some of the forms are now specifically identical with recent
species; the number of these increasing rapidly as we ascend
from the lowest Kainozoic deposit to the Recent period.
Subjoined is a table giving the more important subdivisions




DISTRIBUTION.                   43
of the three great geological periods, commencing with the
oldest rocks and ascending to the present day.
I. PALEOZOIC OR PRIMARY ROCKS.
I. Laurentian. (Lower and Upper.)
2. Cambrian. (Lower and Upper, with Huronian Rocks? )
3. Silurian. (Lower and Upper.)
4. Devonian, or Old Red Sandstone. (Lower, Middle, and
Upper.)
5. Carboniferous. (Mountain-limestone, Millstone Grit, and
Coal-measures.)
6. Permian. (= the lower portion of the New Red Sandstone.)
II. MEsozoic OR SECONDARY ROCKS.
7. Triassic Rocks.  (Bunter Sandstein, or Lower Trias;
Muschelkalk, or Middle Trias; Keuper, or Upper Trias.)
8. Jurassic Rocks.  (Lias, Inferior Oolite, Great Oolite,
Oxford Clay, Coral Rag, Kimmeridge Clay, Portland Stone,
Purbeck beds.)
9. Cretaceous Rocks. (Wealden, Lower Greensand, Gault,
Upper Greensand, White Chalk, Maestricht beds.)
III. KAINOZOIC OR TERTIARY ROCKS.
IO. Eocene. (Lower, Middle, and Upper.)
i i. Miocene. (Lower and Upper.)
I2. Pliocene. (Older Pliocene and Newer Pliocene.)
I3. Post-tertiary. (Post-pliocene and Recent.)




INVERTEBRATE ANIMALS.
PROTOZOA.
CHAPTER I.
I GENERAL CHARACTERS OF THE PROTOZOA.
2. CLASSIFICATION. 3. GREGARINIDA:.
I. General Characters.-The sub-kingdom Protozoa, as the
name implies, includes the most lowly organised members of
the animal kingdom. From this circumstance it is difficult, if
not impossible, to give an exhaustive definition, and the following is, perhaps, as exact as the present state of our knowledge will allow:The Protozoa may be defined as animals, generally of minute
size, composed of a nearly structureless elly-like substance (termed
"sarcode"), showing no convposition out of definite parts or segments, having no definite body-cavity, presenting no traces of a
nervous system, and having either no differentiated alimentary
apparatus, or but a very rudimentary one.
The Protozoa are almost exclusively aquatic in their habits,
and are mostly very minute, though they sometimes form
colonies of considerable size. They are composed of a more
or less. contractile, jelly-like substance, called "sarcode" or
"animal protoplasm," which is semi-fluid in cosatence, and
is composed of an albuminous base with oil-globules scattered
through it. Granules are generally developed in the sarcode,
and in many cases there is a definite internal solid particle,
termed the "nucleus."
In no Protozobn are any traces known of anything like the
nervous and vascular arrangements which are found in animals




PROTOZOA.                      45
of a higher grade. A nervous system is universally and entirely absent, and the sole circulatory apparatus consists in
certain clear spaces called "contractile vesicles," which are
found in some species, and which doubtfully perform the
functions of a heart. A distinct alimentary aperture is present
in the higher Protozoa, but in many there is none; and in all,
the digestive apparatus is of the simplest character. Organs
of generation, or at any rate differentiated portions of the
body which act as these, are sometimes present; but in many
cases true sexual reproduction has not hitherto been shown
to exist.
The " sarcode," which forms such a distinctive feature in all
the Protozoa, is a structureless albuminous substance, not possessing "permanent distinction or separation of parts," but
nevertheless displaying all " the essential properties and characters of vitality," being capable of assimilation and excretion,
of irritability, and of the power of contraction, so as to produce
movements, strictly analogous, in many cases, to the muscular
movements of the higher animals.  In some, too, the sarcode
possesses the power of producing an external case or envelope,
usually of carbonate of lime or flint, and often of a very complicated and mathematically regular structure.
The power of active locomotion is enjoyed by a great many
of the Protozoa;, but in some cases this is very limited, and
in other cases the animal is permanently fixed in its adult
condition. The apparatus of locomotion in the Protozoa is of
a very varied nature. In many cases, especially in the higher
forms, movements are effected by means of the little hair-like
processes which are known as "cilia," and which have the
power of lashing to and fro or vibrating with great rapidity.
In other cases the cilia are accompanied or replaced by one or
more long whip-like bristles, which act in the same fashion,
and are known as " flagella." The most characteristic organs
of locomotion amongst the lower Protozoa are known as
"pseudopodia," and consist simply of prolongations of the
sarcodic substance of the body, which can usually be emitted
from the greater portion of the general surface of the body,
and are capable of being again retracted, and of fusing completely with the body-substance.
2. Classifcation of the Protozoa. The sub-kingdom Protozoa
is divided into three classes-viz., the Gregarinide, the Rhizopoda, and the Infusoria.  In the Infusoria only is a mouth
present, and hence these are sometimes spoken of as the
"Stomatode" Protozoa, whilst the two former classes collectively constitute the "Astomata."




46               MANUAL OF ZOOLOGY.
The following is a tabular view of the divisions of the
Protozoa:Class I. GREGARINIDgE.
Class II. RHIIZOPODA.
Order i. Monera.,,  2. Amaebea.,,  3. Foraminifera.,,  4. Radiolaria.,,  5. Spongida.
Class III. INFUSORIA.
Order i. Suctoria.,, 2. Ciliata.,,3. Flagellata.
3. CLASS I. GREGARINIDE. —The Gregarinidz  may be defined
as parasitic Protozoa, which are destitute of a mouth, and do not
possess the power of emitting "pseudopodia.". They constitute
the lowest class of the Protozoa, and comprise certain microscopic animals which are parasitic in the alimentary canal of
both Invertebrate and Vertebrate animals. They have, however, a special liking for the intestines of certain insects, being
commonly found abundantly in the cockroach. As we shall
see hereafter, in all probability a great deal of the degraded
character of the Gregarinide is due to the fact that they are
internal parasites, and are therefore not dependent upon their
own exertions for food.
Nothing anatomically could be more simple than the structure of a Gregarina, since it is almost exactly that of the unimpregnated ovum (fig. I, a). An adult Gregarina, in fact,
may be said to be a single cell, consisting of an ill-defined
membranous envelope filled with a more or less granular sarcode with fatty particles, which contains in its interior a vesicular nucleus, this in turn enclosing a solid particle, or nucleolus.  In some the body exhibits an approach to a more
complex structure by the presence of internal septa; but it is
doubtful whether this appearance may not be due to the apposition and fusion of two separate individuals. A separate order,
however, has been founded upon individuals of this kind, under
the name of Dicystidea; the name Monocystidea being retained
for the ordinary forms. As regards the size of the Gregarinae,
they vary from about the size of the head of a small pin up
to as much as half an inch in length, when they assume the
aspect of small worms. The integument or cuticle with which




PROTOZOA: GREGARINIDYA.                   47
the protoplasmic body is enclosed may be quite smooth or
striated, or it may be furnished with bristles or spines, or even
in some cases with cilia. Sometimes one end of the body is
furnished with uncinate processes, very similar in appearance
to the hooked "head" of the common tape-worm  (Tenia
soliurz). Essentially, however, the structure of all appears to
be the same. No differentiated organs of any kind beyond
the nucleus and nucleolus exist, and both assimilation and excretion must be performed simply by the general surface of the
body. The body is, nevertheless, contractile, and slow movements can be effected, not, however, by pseudopodia.
In spite of their exceedingly simply structure, the following
very interesting reproductive phenomena have been observed,
Fig. I.-Gregarina of the earth-worm. a Adult Gregarina; b The same encysted;
c With the contents divided into pseudonavicellae; d Free pseudonavicellae;
e Free amcebiform contents of the pseudonavicellae. (After Lieberkiihn.)
sometimes in a single Gregarina without apparent cause,
sometimes as the result of the apposition and coalescence of
two individuals-the exact nature of the process being in
either case obscure.  The Gregarina-or it may be two individuals which have come into contact and adhered together
-assumes a globular form, becomes motionless, and develops
round itself a structureless envelope or cyst, when it is said
to be "encysted" (fig. I, b).  The central nucleus then disappears, apparently by dissolution, whereupon the granular
contents of the cyst break up into a number of little rounded
masses, which gradually elongate and become lanceolate, when
they are termed  "pseudonavicelle ". (or "pseudonaviculke ")
(fig. I, c). The next step in the process consists in the liberation of the pseudonavicelle, which escape by the rupture of
the enclosing cyst (fig. T, d). If they now find a congenial
habitat, they give origin to little albuminous or sarcodic
masses, which exhibit lively movements, and are endowed
with the power of throwing out and retracting little processes
of the body which closely resemble the " pseudopodia " of the




48              MANUAL OF ZOOLOGY.
Rhizopoda; so that the pseudonavicella in this condition is
very similar to an adult Amoeba (fig. i, e).  Finally, these
amcebiform bodies are developed into adult Gregarina. It
will be seen from the above that the formation of the pseudonavicellae out of the granular contents of the body, subsequent
to the disappearance of the nucleus, presents some analogy to
the segmentation of the impregnated ovum which follows upon
the dissolution of the germinal vesicle.
PSOROSPERMI). —There occur as parasites on and within
the bodies of fishes certain vesicular, usually caudate, bodies,
termed Psorospermiz, the exact nature of which is very problematical. According to Lieberkiihn they occasionally give
origin to amcebiform bodies, similar to those which are liberated from -the pseudonavicellse of GregarinidiE. In this case
they should probably be regarded as the embryonic forms of
some Gregarina. By Balbiani, however, they are looked upon
as properly belonging to the vegetable kingdom.
CHAPTER II.
RHIZOPODA.
GENERAL CHARACTERS OF THE RHIZOPODA.-The Rhizopoda
may be defined as Protozoa which are destitute of a mouth, are
simple or compound, and possess the pozwer of emitting " pseudopodia." They are mostly small, but some of the composite.
forms, such as the sponges, may attain a -very considerable
size.  Structurally, a typical Rhizopod —as an Ame4ba-is
composed of almost structureless sarcode, without any organs
appropriated to the function of digestion, and possessing the
power of throwing out processes of its substance so as to constitute adventitious limbs. These are termed " pseudopodia,"
or false feet, and are usually protrusible at will from different
parts of the body, into the substance of which they again
melt when they are retracted. They are merely filaments of
sarcode, sometimes very delicate and of considerable length,
at other times more like finger-shaped processes; and they
are somewhat analogous to the little processes which are occasionally thrown out by the white corpuscles of the blood and
by pus-cells. Indeed it has been remarked by Huxley that
an Amaeba is structurally "a mere colourless blood-corpuscle,
leading an independent life."




PROTOZOA: RHIZOPODA.                       49
The class Rhtzopoda is divided into five orders-viz., the
Mlonera, the Amabea, the Foraminifera, the Radio/aria, and
the Spongida, of which the last is occasionally considered as
a separate class.
ORDER I. MONERA.-This name has been proposed by
Haeckel for certain singular organisms which may provision
ally be regarded as the lowest group of the Rhizopoda. They
are very minute in size, and are distinguished by the fact that
the body is composed of structureless sarcode, capable of emitting thread-like prolongations or pseudopodia, but destitute of
either nucleus or contractile vesicle. The pseudopodia are in
the form of delicate filamentous processes of sarcode, which
interlace and anastomose with one another in every direction,
and which exhibit a circulation of minute molecules and granules in their interior, and along their edges. The body, when
at rest, is more or less nearly circular in form, but it is capable
of undergoing manifold changes of figure. No hard covering
or "test " is ever developed. Reproduction is mostly by fission, with or without precedent encystation and quiescence.'So far as is known, all the Mionera are marine, and their systematic position is still doubtful. From the absence of a nucleus
and contractile vesicle, and from the nature of the pseudopodia,
they would appear upon the whole to be most closely allied to
the -Foraminifera, from which they differ, chiefly if not entirely,
in the absence of a shell defending the soft sarcode of the
body.
Fig. 2.-Morphology of Rh.icpoda. a Amnzcba radiosa, showing the pseudopodia,
contractile vesicle, and nucleus; b Dizfugia, with the pseudopodia protruded from
the anterior end of the carapace; c Individual sponge-particles, or "sarcoids;" d
Ciliated sponge-particles of Granhtiz, showing the resemblance to flagellate Infusorians; c Mono-ciliated sarcoid of Sjoagilla. (After Carter.)
ORDER II. AMCEBEA.-This order comprises those Rhizopoda
which are, with one or two exceptions, naked, have usually short,
blunt, lobose pseudopodia, which do not anastomose with one
another, and contain a " nucleus," and one or more " contractile vesicles."
The Amoeba, or Proteus-animalcule, may be taken as the
type, and a description of it will be sufficient to indicate the




50              MANUAL OF ZOOLOGY.
leading points of interest in the order.  The Inmzba (fig. 2, a)
is a microscopic animalcule which inhabits fresh water, and is
composed of gelatinous sarcode, which admits of a separation
into two distinct layers: an outer transparent layer, termed
the " ectosarc;" and an inner, more fluid and mobile, molecular
layer, called the "endosarc."  The "ectosarc" is highly extensile and contractile, and is the layer of which the pseudopodia are mainly composed; whilst the "endosarc" contains
the only organs possessed by the animal-viz., the "nucleus"
and " contractile vesicle " or vesicles, along with certain fortuitous cavities termed " food-vacuoles."
It is believed by some that the ectosarc is surrounded by
a colourless and structureless investing membrane or cuticle;
but this is denied by others. Be this as it may, there is no
oral cavity, so far as has ever been certainly observed, and the
food is merely taken into the interior of the body by a process
of intussusception-any portion of the surface being chosen for
this purpose, and acting as an extemporaneous mouth. When
the particle of food has been received into the body, the aperture by which it was admitted again closes up, and the discharge of solid excreta is effected in an exactly similar manner.
In this case, however, the area of the general surface within
which an anus may be extemporised, appears to be more
restricted, and to comprise a portion only of the -body
(" villous region").
The "nucleus" is a solid granular body, one or more of
which is present within the endosarc of every Amanba, but
its function is not known with any certainty. The "contractile vesicles" are cavities within the endosarc, of which
ordinarily one only is present in the same individual, though
sometimes there are more. In structure it is a little cavity or
vesicle filled with a colourless fluid apparently derived from
the digestion, and exhibiting rhythmical movements of contraction (systole) and dilatation (diastole). In some cases radiating tubes are said to have been seen proceeding from the
vesicle at the moment of contraction. Regarded functionally,
the contractile vesicle must be looked upon as a circulatory
organ, and it offers therefore the most rudimentary form of a
vascular system with which we are as yet acquainted.
Besides these proper organs, the endosarc usually contains
clear spaces, which are called "vacuoles," or, more properly,
"food-vacuoles."  These spaces are of a merely temporary
character, and are simply produced by the presence of particles of food, usually with a little water taken into the body
along with the food.




PROTOZOAn RHIZOPODA.                  51
There are no traces of any organs of sense, or of a nervous
system, or, indeed, of any other organs in addition to those
already described.  Locomotion is effected, with moderate
activity, but in an irregular manner, by means of the blunt,
finger-shaped processes of sarcode, or pseudopodia, which
can be protruded at will from any part of the body, and can
be again retracted within it. The pseudopodia also serve as
prehensile organs; but they do not interlace and form a network, nor do they exhibit any circulation of granules derived
from the endosarc, as in many others of the Rhizopejda.
As regards the reproductive process in the Ameba, no differentiated sexual organs have hitherto been discovered, and
the true sexual form of the process is therefore unknown.
Fresh individuals, however, may be produced in three ways:Firstly, by simple fission, the animal dividing into two parts,
each of which becomes an independent organism. Secondly,
by the detachment of a single pseudopodium, which becomes
developed into a fresh Amnaba.  Thirdly, by the production of
little spherical masses of sarcode which may be derived from
the'nucleus by fission, or may be produced by a segmentation
of the endosarc, the animal having previously become torpid,
and the nucleus and contractile vesicle having disappeared.
These little masses, however produced, develop themselves
when liberated into ordinary Ampebee.  This last method of
reproduction is obviously very closely analogous to the production of " pseudonavicellae" in an encysted Gregarina.
It has been doubted, apparently with considerable reason,
whether the so-called Amzba are distinct species of animals, or
whether they are not rather transitory stages in the life-history
of other organisms. It is quite certain that several of the
Protozoa pass through an Amceboid stage, and it is also certain
that vegetable matter not uncommonly assumes similar characters (e.g., the mycelium of certain fungi). It is therefore
not impossible that the forms known to the microscopist as
Amwbee may be ultimately discovered not to be permanent
and distinct species; but the evidence on this head is still
defective.
The remaining members of the Amzmbea are constructed
more or less closely after the type of the Amauba itself. In the
nearly allied Daiffugia, the sarcode forming the body of the
animal is invested with a membranous envelope or " carapace,'
strengthened by grains of sand and other adventitious solid
particles, and having a single aperture at one extremity,
through which the pseudopodia are protruded (fig. 2, b). The
animal generally creeps about head-downwards, so to speak;
4




52               MANUAL OF ZOOLOGY.
that is to say, with the closed end of the carapace elevated
above the surface on which it is moving. In ArceZla there is a
discoid or basin-shaped carapace, secreted by the animal itself,
and likewise possessing but a single pseudopodial aperture,
placed in this case on the flat surface of the body.
In Pamphagus there is no carapace, but the pseudopodia
are nevertheless protrusible from one extremity only of the
body, the remainder of the surface appearing to be of too
resistant a consistence to allow of this. The common sunanimnalcule (Actinophrys sol) is another well-known Rhizopod
Fig. 3. —Actinoqhrys sol: showing the radiating pseudopodia.
One specimen has swallowed a Diatom.
which is usually placed in this order (fig. 3). It consists of
a spherical mass of sarcode, about 1-I300 of an inch in diameter, and usually covered with long, radiating, filamentous
pseudopodia, which are much less mobile than in the case of
the Amoeba. The division of the substance of the body into
ectosarc and endosarc is tolerably evident, and the latter
contains numerous granules and vacuoles. The pseudopodia
are derived from the ectosarc alone, the endosarc not passing
into them, and they exhibit a circulation of granules along their
edges, though this is not nearly so marked a feature as in the
case of the Foranzinifera. A nucleus and contractile vesicle
are also present. The long filamentous pseudopodia of Actinophrys make a decided approach to the Foraminifera, and for
this reason the sun-animalcule is sometimes placed with the
latter in a single order.
The Amaebea may be divided into two sub-orders: I. Amrebiina, including those forms which have the body naked; and
2. Arcellina, comprising those in which the body is protected
by a carapace.




PROTOZOA: FORAMINIFERA.                   53
CHAPTER  II.
FORA MINIFERA.
ORDER III. FORAMINIFERA. —The Eoraminifera may be
defined as Rhizojpoda in which the body is protected by a shell or
" test," usually composed of carbonate of lime; there is no distinct
separation of the sarcode of the body into ectosarc and endosarc,
and the nucleus and contractile vesicle are both absent.  The pseudopodia are long and filamentous, and interlace with one another
to form a network.
The Foraminifera are specially characterised by the possession of a " test " or external shell, which is usually composed
of carbonate of lime, but is'-6often composed of grains of sand
or other adventitious solid particles cemented together by
animal matter, or which, as in Gromia, may be simply chitinous. (If.Lieberkiihnia is to be regarded as a Foraminifer, the
possession of a test cannot be looked upon as essential, since
this animalcule is naked. The Monera, also, differ from the
present group mainly, if not altogether, by their naked and
unprotected bodies.) The test iB usually composed of an
aggregation of chambers or "loculi" (fig. 4, c), and its walls
are usually pierced by numerous pores or "foramina" through
which the pseudopodia are protruded; the place of these
being in some forms supplied by the large size of the terminal,
or " oral," aperture of the shell (fig. 4, b). The presence or
absence of foramina in the shell-walls is believed to constitute
a genuine structural distinction, and the Foraminifera may be
thereby divided into two great groups (Perforata and Imperforata).
As regards the soft parts of the Foraminifera, the body is
composed of extensile and contractile sarcode-usually reddish or yellowish in colour-which not only fills the interior of
the shell, but generally invests its outer surface also with a thin
film, from which the pseudopodia are emitted. The test, therefore, in this case, is not a true cuticular secretion, like that of
the Mollusca, but it is truly immersed within the sarcode of the
body. The sarcode is not differentiated into a distinct ectosarc
and endosarc, and is devoid of a nucleus and contractile
vesicle, and, indeed, of any organs or specialised parts of any
kind. From this uniformity in its composition there seems
some reason to conclude that the Foraminifera-in spite of the
complexity and mathematical regularity of many of their shells




54                 MANUAL OF ZOOLOGY.
-should be looked upon as the, lowest forms of the R/izojoda,
or even of the Protozoa.
The pseudopodia in all the Foramninifera (fig. 4, b, c) are filamentous and protrusible to a great length, and they possess the
singular property of uniting together in various directions so
as to form  a kind  of network, like an  "animated  spider's
web."  (Hence the name Reticulosa applied to the order by
Dr Carpenter.)   This property, however, is not peculiar to
members of this order, but is seen also in Actinophrys and in
the Thalassicollida, though to a less extent.  Further, throughout the entire network formed by the inosculating pseudoFig. 4. —Morphology of Foraminifera. a Lagena vulgaris, a monothalamous Foraminifer; b Miliola (after Schultze), showing the pseudopodia protruded from the
oral aperture of the shell; c Discorbina (after Schultze), showing the nautiloid
shell with the foramina in the shell-wall giving exit to pseudopodia; d Section of
Nodosaria (after Carpenter); e ANodosaria hispida; f Globigerina bulloides.
podia there is a constant circulation of granules in different
directions. This singular phenomenon is in many respects
analogous to the circulation of granules which is seen in
many vegetable cells, and it is believed by Dr Carpenter that
"the conditions of the two sets of phenomena are essentially
the same."
The shells of Foraminfera may be classed in three divisions,
termed  respectively  the  "porcellanous,"  the  "hyaline"  or
" vitreous," and the " arenaceous."  Tie porcellanous shell is
quite homogeneous in its composition, is opaque-white when
seen by reflected light, and is not perforated by pseudopodial




PROTOZOA: FORAMINIFERA.                  5 5
foramina. In these forms (e.g., Miiola, fig. 4, b) the pseudopodia are emitted solely from the mouth of the last-formed
segment of the shell. The vitreous shell is transparent and
glassy in texture, and its walls are perforated by numerous
pseudopodial apertures.  The arenaceous shell is, properly
speaking, not a true shell secreted by the animal, since it is
simply composed of particles of sand united together by some
unknown cement. Its walls may or may not be traversed by
pseudopodial foramina.
As regards the form of the shell, the Foraminifera may be
conveniently, though arbitrarily, divided into two sections:
the Monothalamia and the Polythalamia.  In the first of these
sections (fig. 4, a), comprising the so-called " simple " or "unilocular " Foraminiifera, the shell consists of a single chamber,
and the animal is, in fact, nothing more than a little mass or
sarcode enveloped in a calcareous covering. Lagena, with its
beautiful flask-shaped shell, may be taken as the type of this
division. Another well-known unilocular form is Enlosolenia,
which is like Lagena in shape, but has the tubular neck reversed,
so as to be inserted into the interior of the test.  In the
Polythzalamia, or "multilocular" Foraminifera, the shell is
composed of many chambers separated from one another by
divisional walls or "septa" (fig. 4, c, d, c), each of which is perforated by one or more openings, " septal apertures," by means
of which the sarcode occupying the different chambers is
united into a continuous and organic whole, the connecting
bands being called "stolons."  Complex as their structure
often is, the compound Foraminifera are, nevertheless, formed
by a process of continuous gemmation or budding from a
single "primordial segment" in every respect identical with
the permanent condition of a simple species.  They commence
their existence, therefore, as Mfonothalamia, and are converted
into Polythalamia merely by a process of " vegetative " or " irrelative repetition." As their development proceeds, the primitive
mass of sarcode, or "primordial segment," throws out fresh
segments in the form of buds according to a determinate law;
and it is upon the- direction in which these segments are
evolved that the ultimate form of the shell depends. The
more important variations in this respect are as follows:-If
the additional segments are added to the primordial chamber
in a linear series, so as to form a straight or slightly curved
line, we obtain respectively a Nodosaria (fig. 4, d, e) or a Dcntalina. When the new chambers are added in a spiral direction,
each being a little larger than the one which preceded it, and
the coils of the spiral lying in one plane, then we get the " nauti



56               MANUAL OF ZOOLOGY
loid" shell, so common amongst the Foraminifera (fig. 4, c).
This type of shell is so closely similar to the shape of the Pearly
Nautilus, that the older naturalists were long in the habit of
classing these forms along with the Cejhaloopoda, or Cuttlefish order. In the true nautiloid shell the convolutions of the
spiral lie in a single plane, as in Rotalina, and the shell is said
to be " equilateral." In other cases, however, the spiral passes
obliquely round a central axis, and the shell becomes conical
or turreted, when it is said to be " inequilateral " or " trochoid."
In other forms, such as Nummulites (fig. 5) and Orbitolites, the
structure of the shell, though regular, is much more complicated. Besides these symmetrical forms, there exist others in
which the arrangement of the segments is very irregular, as is
seen in Globigerina, Acervulina, &c. (fig. 4, f).
Besides the true pseudopodial foramina with which the walls
of the test in most of the Foraminifera are pierced, there exists
in some forms an additional system of complicated branching
and anastomosing tubes, which are distributed between the
laminge of the shell, and establish a communication between its
external and internal surfaces.
CLASSIFICATION OF FORAMINIFERA.-The classification of
the Foraminzfera has hitherto proved a matter of extreme difficulty, and probably none of the arrangements as yet proposed
can be considered as more than provisional.  The following is
the classification adopted by Dr Carpenter, who is one of the
greatest living authorities upon the group:ORDER RETICULOSA. (= FORAMINIFERA.) —Rhizotfods showing no differentiation, or a very imperfect one, into ectosare and
endosarc; no nucleus or contractile vesicle; tseudopodia filamentous, minutely subdivided, and inosculating freely to form  a network.
Section i. Imperforata.-Envelope membranous or calcareous, the walls not perforated by apertures for the pseudopodia, which are emitted solely from the single or multiple
aperture of the shell.
Families. i. Gromida.  Test membranous.
2. Miliolida.  Test porcellanous.
3. Lituolida. Test arenaceous.
Section 2. Perforata.-Envelope calcareous (hyaline or vitreous) or rarely arenaceous, its walls traversed by numerous
foramina for the emission of pseudopodia.
The following classifications by D'Orbigny and Schultze are
founded merely upon the form of the shell, and, as such, are




PROTOZOA: FORAMINIFERA.                       57
purely arbitrary. Of the two, Schultze's arrangement is probably the more satisfactory.
TABLE OF D'ORBIGNY'S ARRANGEMENT OF THE FORAMINIFERA.
Order I. Monoslega.-Body consisting of a single segment; the shell of
a single chamber.
Order 2. Stichostega.-Segments arranged in a single row, in a straight
or slightly curved line.
Order 3. Helicostega.-Segments arranged in a spiral, the shell forming a
number of convolutions. (The " nautiloid" Foraminifera.)
Order4. Entomostega.-Segments arranged on two alternating axes,
forming a spiral.
Order 5. Enallostega.-Segments arranged on two or three alternating
axes, not forming a spiral.
Order 6. Agathistega. -Chambers wound round an axis, each segment
embracing half the entire circumference.
TABLE OF SCHULTZE'S ARRANGEMENT OF THE FORAMINIFERA.
Section I. Helicoidea.-Segments arranged in a convolute series.
Section 2. Rhabdoidea.-Segments placed in a direct line.
Section 3. Soroidea.-Segments disposed in an irregular manner.
AFFINITIES OF FORAMINIFERA.-The Foraminifera   are related on the one hand to the Amebea, and on the other to the
Spongida.  From  the former the "unilocular". Foraminkfera
differ, both in the possession of an external envelope, and in
the much less highly differentiated characters of their sarcode;
but the points of resemblance are obvious, and in such forms
as Actinophrys and Lieberkiihnia we are presented with an apparent transition between the two orders. From the shelled
Ammaebea, such as Arcella, the Foraminzfera are broadly separated by the absence in the former of pseudopodial pores, and
are fundamentally distinguished by the different nature of the
sarcode-body.
To the Sponges the Foraminifera are related in various
ways, one of the most striking links being found in Carjenteria,
a singular attached form  of Foraminifer.  The shell, namely,
of Carpenteria is conical and calcareous, composed of an aggregation of chambers arranged in a spiral, and having its walls
perforated by numerous foramina of minute size. The interior
of the chambers, however, is filled with " a fleshy, sponge-like
body," strengthened by numerous spicula. Another curious
link between the Foramnizfera and the Sponges is the Squanuzina scop2ula of Carter, which is truly a Foraminzfer, though
originally referred to the latter. It consists of an arenaceous
test, forming a pedestal surmounted by an obversely conical
column.  Both pedestal and column are more or less perfectly
chambered, and are filled with semi-transparent yellowish sar



58              MANUAL OF ZOOLOGY.
code. At the summit of the column is a minute aperture surrounded by a brush of spicules, and the whole structure is fixed
by the pedestal to some solid object.
To the Polycystina, the Foraminifera are obviously and
closely allied. They agree in the nature of the sarcode-body,
in the filamentous, inosculating pseudopodia, and in the phenomenon of a pseudopodial circulation of granules. They
differ solely in the nature of the "test," which is calcareous or
arenaceous in the Foranzinifera, but is always siliceous in the
Polycystina.
BATHYBIUS, COCCOLITHS, AND COCCOSPHERES.-It may be
as well to notice here a singular organism which is certainly
referable to the Rhizeopoda, though its exact affinities are
doubtful. Certain minute oval or rounded bodies have long
been known as occurring attached to the surface of the shells
of Foramninifera, and they were originally described by Professor Huxley under the name of coccoliths. Subsequently it
was discovered by Dr Wallich that these singular bodies occur
not only in the free condition, but also attached to the external
surface of little spherical masses of sarcode to which he gave
the name of coccospheres. The coccospheres are enclosed in a
delicate envelope apparently of a calcareous nature, and are
studded at nearly regular intervals by the coccoliths. More
recently still, it has been discovered by Professor Huxley that
both the caccoliths and the coccospheres are embedded in masses
of protoplasmic or sarcodic substance, covering wide areas of
the sea-bottom, to which they bear the same relation that the
spicules of sponges or of Radio/aria do to the soft parts of
these animals. To this undefined and diffused protoplasm
with its contained coccoliths and coccoslpheres the name Batahybius
has been applied by Professor Huxley. Its exact position, as
already said, is doubtful; but it is believed by Dr Carpenter to
be a rudimentary form of the Foraminifera, and to be somewhat
allied to the ancient Eozoin. A curious point as regards the
coccoliths has recently been brought to light by Dr Giimbel, the
celebrated palkeontologist, who believes that he has succeeded
in demonstrating in them the existence of cellulose, or of some
substance closely allied to cellulose. He has also shown that
bodies similar to, if not. identical with, coccoliths, occur in formations as old as the Potsdam  Sandstone (Lower Silurian) of
North America.  More recently still, Mr Carter has shown that.occoliths occur in great numbers in the Laminarian zone, and
he asserts them to be solitary, unicellular, calcareous Algae.
He describes them under- the name of Afelobesia unicellularis
and MA. discus, according as they are oval or round; and he




PROTOZOA: FORAMINIFERA.                   59
believes that the coccospheres are most probably their "sporangia."  Upon this view the tern "coccoliths " would be restricted to the fossil forms.
DISTRIBUTION OF FORAMINIFERA IN SPACE.-The Foraminifera are mostly marine, and are found in almost all seas, though
more abundantly in those of the warmer parts of the globe.
It is concluded by Dr Carpenter that "the foraminiferous
fauna of our owns seas probably presents a greater range of
variety than existed at any preceding period; but there is no
indication of any tendency to elevation towards a higher type."
One of the most remarkable facts about their distribution at
the present day, is the existence of a deposit at great depths
in the Atlantic, but only in areas traversed by heated currents,
formed almost entirely of the shells of Foraminifera, and very
closely resembling chalk. It has further'been quite recently
established that there coexist with these Foraminifera various
animals of a higher grade, some of which closely resemble, or
are even specifically inseparable from, well-known Cretaceous
species. There is therefore some reason to conclude that the
bottom of the sea at great depths is peopled at the present day
by a fauna which is very closely allied to that of the Chalk.
Most living Foraminifera are very minute, but some of the
extinct forms attained a size of as much as three inches in
circumference (e.g., the Nummulite, fig. 5), and spheres of
Parkeria may attain a circumference of nearly four inches.
Some forms may be obtained adhering to the roots of tangle
at or near low-water mark, but they are mostly to be dredged
from tolerably deep water.  They have been found, in fact, in
great abundance in the deepest parts of the ocean which have
as yet been examined by the dredge —at a depth, namely, of
nearly three miles.
DISTRIBUTION OF FORAMINIFERA IN TIME. —Remains of
Foraminifera have been found in Palaeozoic, Mesozoic, and
Kainozoic formations.  In the oldest stratified rocks with
which we are acquainted-viz., the Laurentian rocks of Canada
-there occurs a singular body which has been described as the
remains of a gigantic -Foraminifer; under the name of Eozoiin
Canadense.  If truly organic, as is doubted by some, it is the
oldest fossil as yet discovered. It appears to have grown in
reef-like masses resembling the sessile patches of Polytrema*
* Polytrema is a little branched coral-like Foraminifer, composed of a
calcareous test forming a number of irregular chambers, which communicate
with one another by wide orifices, and are filled with colourless sarcode.
The walls of the chambers are also penetrated by an extensive system of
capillary canals.




60              MANUAL OF ZOOLOGY.
and Carpen/eria, to both of which, as well as to the extinct
Nummulites, it shows a decided affinity. In the Silurian rocks,
remains of Foraminifera, some of which are apparently identical with existing forms, have been detected in various places,
and it is not improbable that the large Silurian fossils known as
Receptaculites and Stromatojpora should really be referred to this
order. In the Carboniferous rocks of Russia whole beds are
composed of a species of Eusulina. In the Secondary rocks
Foraminifera occur in great abundance, the widely-spread formation known as the Chalk being crowded with these organisms. Chalk itself, in fact, is almost entirely composed of the
cases of Foraminifera, some of which are identical with species
now existing.
I                2                 3
Fig..-lNummnulifes laevigatus. Eocene.
In the Tertiary rocks the Foraminifera attain their maximum
of development, both as regards the size and the number of
the forms which characterise them. The period of the Middle
Eocene is especially distinguished by a very widely spread and
easily recognised rock known as the Nummulitic Limestone,
so called from the abundance in it of a large coin-shaped Foraminifer termed the Nummulite (fig. 5). The Nummulitic Limestone stretches from the west of Europe to the frontiers of
China; but in some cases, in place of Nummulites proper, it
contains the remains of a mimetic form  termed Orbiloides.
Upon the whole, Dr Carpenter concludes that "tthere is no
evidence of any fundamental modification or advance of the
foraminiferous type from the Palaeozoic period to the present
time."




PROTOZOA: RADIOLARIA.                    61
CHAPTER IV.
RADIOLARIA.
ORDER  IV. RADIOLARIA. - The  order Radiolaria was
founded by Muller to include the Polycystina, the Acanthometrina, and the Thalassicollida, to which Dr Carpenter adds
Actinoqphrys and its allies, chiefly on account of the form of the
pseudopodia. Here, however, the term will be employed to
designate the first three of these, and Acfinophrys will be
placed amongst the Amwbea, to which its alliance appears to be
more decided. Most of the Radiolaria are marine, but some
few forms of Thalassicollida have been described as occurring
in fresh water.
The order Radiolaria may be defined as comprising those
Rhizopods which possess a siliceous test or siliceous spicules, and
are provided with pseudopodia which stand out like radiatingfilaZnents, and occasionally run into one another.
I. FAMILY ACANTHOMETRINA.-mThe Acanthometrcz (fig. 6, a)
are all minute, and are found floating near the surface in the
open ocean, sometimes in great numbers. They consist of
sarcode-bodies which are supported by a framework of radiating siliceous spines, the extremities of which usually project
Qc0  o00
Fig. 6.-a AcanlTowmetra lanceolata; b Haliomarnac iexacanthzum, one of the
Polycystina, showing the radiating pseudopodia. (After Miller.)
considerably beyond the body. The substance of'the body
admits of division into an outer nlembranous layer, or " ectosarc," and an internal granular layer, or "endosarc." The
siliceous spines are hollow, being grooved at the base by a
gutter, which is continued further up the spine by a canal terminating at the apex of the spine by a distinct aperture.  The




62              MANUAL OF ZOOLOGY.
spines, in consequence of this structure, are able to serve for the
transmission of the pseudopodia, which gain the exterior by
running through the canals and escaping at their apices. Many
of the pseudopodia, however, do not occupy the canals of the
spines.
II. FAM. POLYCYSTINA.-The members of this family are
closely related to the Foraminifera, differing from them chiefly
in the fact that their shells are composed of flint instead of
carbonate of lime, as in most of the latter. They possess a
body of sarcode, which is enclosed in a foraminated siliceous
shell, which is often furnished with spine-like processes, and is
usually of great beauty (fig. 6, b). The sarcodic substance of
the body is olive-brown in colour, with yellow globules, and
often does not entirely fill the shell.  The pseudopodia are
emitted through the foramina in the test, and are long, ray-like
filaments, which display a slow movement of granules along
their borders.
The Polycystina are all microscopic, and are all inhabitants
of the sea, having a very wide distribution.  They are also
found abundantly in certain Tertiary deposits, being often erroneously described as Diatomacece.
III. FAM. THALASSICOLLIDA. —The 7thalasszcioida have been
defined as being Rhizoa5oda which are "provided with structureless
cysts containing cellular elements and sarcode, and surrounded
by a layer of sarcode, giving of0 pseudopodia, 7/hich commonly
stand out like rays, but may and do run into one another, and so
fore networks. -(Huxley.)
The T/alassicollida may be simple or composite, the latter
consisting essentially of aggregations of the former; whilst
these are fundamentally composed of a mass of granular protoplasm, containing a nucleus, but without a contractile vesicle,
" enclosed in a membranous capsule, which is in turn protected
by a more or less thick gelatinous exudation, whilst numerous
sarcoblasts occur scattered through the endosarc, and occasionally a few may be seen suspended within the external gelatinous stratum."-(Wallich.) The whole organism is supported
by more or less extensively developed skeletal structures. The
skeleton may be simple, consisting of a delicate fenestrated
shell; or may be compound, consisting of a number of spicular
masses.
The three best-known genera of the family are Sphcerozoiim,
Collosphaera, and Thalassicolla.  They are all marine, being
found floating passively at the surface of most seas; and they
vary in size from an inch in diameter downwards. Sphaerozoiim
consists essentially of a number of spherical sarcodce-bodies




PROTOZOA: SPONGIDA.                       63
{sometimes called "cellaeform bodies") with distinct nuclei,
surrounded by a zone of siliceous spicules, the whole being
embedded in a common gelatinous matrix. The centre of the
mass is vacuolated, sometimes to such an extent that it becomes a hollow sphere.
In Collosjphera, the spherical body-which is very like that
of the preceding form-is enclosed in a transparent siliceous
Fig. 7.-Morphology of Radiolaria. a Siliceous fenestrated test of Collos/1imera
Huxleyi; b Thalassicolla inorum, showing celleform bodies, compound groups
of spicules, and radiating pseudopodia.
envelope, which is perforated by numerous rounded apertures
or "fenestrae."  This form, therefore, approaches very closely
to the Polycyslina, especially to those in which the foramina
are so large that the test is reduced to a mere reticulate framework (fig. 7, a).
ihialassicolla differs little from  either of the above in fundamental structure, but it contains a number of compound
siliceous spicules embedded in its ectosarc (fig. 7, b).
CHAPTER V.
SPONGIDA.
ORDER V. SPONGIDA.-The true nature of sponges has long
been a matter of dispute, but they are now almost universally
referred to the animal kingdon, and placed either in or near
the Rhizopoda.  Some observers still maintain the vegetable
nature ot sponges, but this opinion has no real grounds for its
support, and is chiefly founded upon loose analogies, and upon
a certain similarity in outward form.
The SPongida may be defined as "sarcode-bondies, destitute af




64              MANUAL OF ZOOLOGY.
a mouth, and united into a composite mass, which is traversed by
canals opening on the surface, and is almost always supported
by a framework of horny fibres, or of siliceous or calcareous
spicula."-(Allman.)
From the above definition it will be seen that a sponge
is composed essentially of two elements —a soft, gelatinous,
investing "flesh," and an internal supporting framework or
"skeleton."
Taking an ordinary horny sponge as the type of the order,
we find it to be composed of a skeleton (fig. 9, d) of horny
reticulated fibres which interlace in every direction, and are
pierced by numerous apertures, the whole surrounded externally and internally by a gelatinous glairy substance, like whiteof-egg, the so-called "sponge-flesh."  The horny skeleton is
composed of a substance called "keratode," and is usually
strengthened by spicula of lime or flint, which also occur less
abundantly in the sponge-flesh. These must not, however, be
confounded with the skeleton of the true calcareous or siliceous
sponges in. which the keratode is wanting.  Of the apertures
which penetrate the substance of the sponge in every direction,
some are large crateriform openings, and are termed " oscules,"
or "exhalant apertures;" whilst others, which occur in much
greater numbers, are greatly smaller in size, and are termed
" pores," or " inhalant apertures."  Both the oscula and pores
can be closed at the will of the animal; but the oscula are
permanent apertures, whereas the pores are not constant, but
can be formed afresh whenever and wherever required. The
"sponge-flesh," which invests the entire skeleton, is found
upon a microscopical examination to be entirely composed of
an aggregation of rounded amcebiform bodies-the so-called
" sponge-particles" or "sarcoids" (fig. 2, c, d, e). Some of
these are ciliated; whilst others are capable of emitting pseudopodm  from all parts of their surface, and are provided with
nuclei, thus coming closely to resemble so many Amcebce. Regarding the skeleton as something superadded, we may, in fact,
look upon a sponge as being essentially nothing more than an
aggregation of Amaxbea, since each " sarcoid" is capable of
procuring and. assimilating food for itself in a manner strictly
analogous to what we have seen in the Amceba. This view
becomes still more easily comprehensible when we consider
the simplest condition in which a sponge occurs in nature (as
exemplified, for instance, in certain of the Calcispongice); the
condition, namely, in which the entire sponge consists of a
colony of amcebiform sarcoids, secreting a common skeleton,
but provided with only a single " osculum," and a greater or




PROTOZOA: SPONGIDA..65
less number of inhalant "pores." There are, in fact, many
who hold that the more complex sponges are merely produced
by the aggregation together of a number of these simpler
colonies.
In a living sponge a constant circulation of water is maintained by means of an aquiferous system (fig.;8), which is
b
a      c
Fig. 8.-Diagrammatic section of Spongilla (after Huxley). a a Superficial layer or
"dermal membrane;" b b Inhalant apertures or "pores;" c r Ciliated chambers; d An exhalant aperture or "osculum." The arrows indicate the direction
of the currents.
constituted by the oscula and pores-already alluded to-and
by a system of canals excavated in the substance of the
sponge, and uniting the two sets of apertures.  The water
passes in by the " pores" or inhalant apertures, and is conveyed by a series of canals-the "incurrent"' or "afferent"
canals-to  a second series of tubes-the  " excurrent"  or
" efferent" canals-by which it reaches the "oscula" and is
finally expelled from the body. These processes are regularly
performed, and their mechanism was long a subject of speculation. It is now known, however, that beneath the superficial layer or'' dermal membrane" of the sponge there exist
chambers lined with sponge-particles which are provided
with vibratile filaments or cilia (fig. 8, c, c).  The pores open
into these chambers, and from them proceed the incurrent
canals, each being dilated at its commencement into a sac,
which is also lined with ciliated  sponge-particles.   By the
vibratile action of these cilia, currents of water are caused to
set in by the pores; and as out-going currents proteed from
the oscula, a constant circulation of fresh water is maintained
through the entire  sponge.   In  this way each individual
sponge-particle is enabled to obtain nutriment: the process
being at the same time not improbably a rudimentary form of
respiration. The chambers or sacs lined with ciliated sarcoids




66                MANUAL OF, ZOOLOGY.
have been shown by Mr Carter to be the essential element in
the organisation of the fresh-water and marine sponges, and to
be the fundamental expression of the alimentary system.
The reproduction of sponges may be effected either
asexually or sexually, the following being a brief outline of
the phenomena which have been observed in the common
fresh-water sponge (Spongilla), in which the process has been
most accurately noticed.
C    I
Fig. 9 —a Gemmule of Sfongiila; h Hilum; b Diagrammatic section of the geinmule, showing the outer layer of amphidiscs and the inner mass of cells; c One
of the amphidiscs seen in profile; d Fragment of the skeleton of a horny sponge
(after Bowerbank). showing the interlacing horny fibres with spicqsla. All much
magnified.
In the first or asexual method of reproduction, which takes
place in the winter, the deeper portions of the sponge are
found to be filled with small seed-like rounded bodies, termed
"gemmules" or "spores," each of which possesses a small
aperture or "hilum " at one point (fig. 9, h).  Each gemmule
is composed of an outer coriaceous capsule surrounded by a
layer of peculiar asteroid spicula, resembling two toothed.wheels united by an axle, and termed "amphidiscs" (fig. 9, b,
c). These amphidiscs are embedded in sarcode, whilst their
inner surfaces rest upon the tesselated capsule already mentioned. In the interior of the capsule thus formed is a mass
of cells, of which the central ones contain numerous germs.
When the'spring comes, these masses of "ovi-bearing cells"
are discharged through the "hilum" of the gemmule into the
water, and are developed into new SpongillZ..Spongilla also appears to reproduce itself in a somewhat analogous manner by means of what are termed " swarm-spores."
These are small bodies, containing reproductive germs, and




PROTOZOA: SPONGIDA.                   67
provided with numerous cilia by which they move about actively,
becoming finally attached to some solid body, and developing
themselves into the adult sponge.
In the second or sexual method of reproduction, certain of
the sponge-particles or "sarcoids" separate themselves and
become nucleolo-nucleated, thus coming to resemble ova. At
the same time other sarcoids become motionless, and their
contents become molecular, and are finally converted into spermatozoa. By the rupture of these, and by the consequent
contact of the different elements, embryos are produced,
which are at first ciliated and move about freely, becoming
eventually stationary, and developing into new individuals.
CLASSIFICATION OF THE SPONGES.-The Spolngida have been
variously classed, and a good natural arrangement is still a
desideratum.  By Dr Bowerbank they are somewhat arbitrarily arranged in three orders-viz., the Keratosa, the Silicea,
and the Calcarea, of which the first is believed to hold the
lowest place. In the Keratosa the skeleton is composed of
interlacing horny fibres, usually strengthened by spicula either
of flint or lime.  In the Calcarea or Calcispongice the skeleton
is composed of carbonate of lime; whilst in the Siliceous
sponges it is composed either of spicules of silex, or " of solid,
laminated, and continuous siliceous fibre." By Professor AVyville Thomson the siliceous sponges are arranged in a separate
order under the name of the " vitreous sponges " ( Vitrea). The
nature of the skeleton thus varies considerably, whilst the spicules show almost indefinite modifications of shape, though
they are constant for any given species, in any given part of
its organisation. The sponge-flesh is much more uniform in
its nature and composition. It may be noticed, however, that
in Spongilla the sponge-particles are filled with green granules,
which are apparently identical in chemical composition with
the green colouring matter of plants (chlorophyll). In Grantia,
too, the sarcoids are furnished with long filamentous appendages or cilia (fig. 2, d). The siliceous sponges are mostly inhabitants of the deep sea, and many of them are remarkable
for their long and slender spicules of flint.  In Hyalonema, or
the glass-rope, long placed amongst the Zoophytes (Zoantharia
sclerobasica), there is a cup-shaped sponge-body, supported by a
rope of long twisted siliceous fibres, which are sunk in the mud
of the sea-bottom. In other "anchoring sponges," such as
Pheronema and Holtenia, the body is sessile or stemless, and is
moored to the mud by a beard of long delicate spicules. These
sponges, in their single, long, chimney-like osculum, show a
curious resemblance to the fossil Sizhonias of the greensand.




68              MANUAL OF ZOOLOGY.
Similar root-fibres of flint, traversing the mud in every direction, occur in the beautiful Venus' Flower-basket (Euplectella),
without any exception one of the most exquisite of all organic
structures known- to us.
DISTRIBUTION OF SPONGES IN SPAcE.-Sponges are almost
exclusively marine, the Spongille alone being inhabitants of
fresh water; and they are of almost universal occurrence. The
sponges of commerce are mostly obtained from the Grecian
Archipelago and the Bahama Islands. Recently the existence
of numerous siliceous sponges at great depths in the ocean has
been demonstrated by Drs Carpenter and Wyville Thomson.
They are associated with numerous Foraminifera and with
Crinoidea, the whole assemblage bearing a singularly close resemblance to the fauna of the Cretaceous epoch. The common marine sponges are mostly found attached to some solid
object between tide-marks or in deep water. The vitreous or
siliceous sponges appear to be exclusively inhabitants of the
deeper parts of the ocean.  One genus (Cliona) inhabits
branching cavities in shells, which the sponge excavates for
itself apparently by means of its siliceous spicula. Fossil
shells mined by a boring-sponge, allied to the recent Clionw,
are found from the Silurian rocks upwards.
DISTRIBUTION OF SPONGES IN TIME.-Remains of sponges
are known to occur in formations belonging to-the Palaeozoic,
Mesozoic, and Kainozoic epochs. The keratose or horny
sponges are obviously incapable of leaving any evidence of
their existence, otherwise than by the preservation of the
spicula with which the skeleton is furnished; and such are
occasionally found, though they are of rare occurrence. The
calcareous sponges are found from the Silurian rocks upwards,
attaining their maximum in the seas of the Secondary epoch,
the Chalk being especially characterised by their presence.
The most important group of fossil sponges is that known as
the Petrospongiadae, characterised by the possession of a stony
reticulate framework or skeleton, and by the absence of
spicula. The most important genera of this group are Sparsispongia (Devonian) and Ventriculites (Chalk).
Of the Palaeozoic sponges, Archceocyathus is found in the
Potsdam sandstone of North America (Upper Cambrian?);
Palceospongia and Acantlospongia are familiar Lower Silurian
forms; and Amphispongia and Favospongia occur along with
other forms in the Ludlow rocks.  In the Devonian rocks
sponges occur pretty frequently, Spa-rsispongia being the commonest genus. (The Devonian Steganodictyum is really the
cephalic buckler of a pteraspidean fish.) The most important




PROTOZOA: SPONGIDA.                  69
Mesozoic genera of sponges are Ventricuites and Siphonia;
and the order appears, upon the whole, to attain its maximum
in the Cretaceous epoch. There seems no reason to doubt
but that many of the chalk-flints owe their origin to sponges:
and in some sections of flint are found minute " spherical bodies
covered with radiating and multicuspid spines," which have
been termed Spjiniferites or Xanthidia, and are probably the
" gemmules" of sponges. (By some, however, these bodies are
regarded as being the "sporangia" of Desmidice, an order of
the Protophyta.) Many Cretaceous and Tertiary shells are
found to be mined by a species of boring-sponge, which is
nearly allied to the recent Cliona.
AFFINITIES OF SPONGES.-As already pointed out, the
sponges are allied both to the Amwbea and to the Foraminifera.
Indeed the individual " sarcoids" or sponge-particles can scarcely
be distinguished, when detached, from Ambeve. The sponges
show likewise a decided relationship to the Radiolaria; and
by Professor James-Clark they are believed to be nearly allied
to the "flagellate" Infusoria. This observer, in fact, states his
" conviction that the true ciliated Spongice are not Rhizopoda in
any sense whatever, nor even closely related to them, but are
genuine compound flagellate Protozoa.' To prove this view,
however, it should be shown that each sponge-particle possesses
at any rate a distinct mouth, with or without a rudimentary
alimentary canal. More recently Dr Ernst Haeckel and others
have endeavoured to show that the sponges are most nearly
allied to the Sea-anemones (Actinozoa); but this seems to have
arisen from a misconception as to the compound nature of
the former.  Three views, namely, may be held as to the
"individuality" of a sponge. Eirstly, it may be held that the
entire organism which we call a sponge is a single animal.
The microscope has rendered this view wholly untenable.
Secondly, it may be held that the entire sponge-mass is a single
"zoological individual," of which each sarcoid is a single
"zobid."  As each sponge-mass is certainly in most cases the
product of a single ovum, this is the most probable and reasonable view. Thirdly, it may be held that each sponge-mass
consists of a number of aggregated " individuals," each of which
is constituted by a single exhalant "osculum," together with
the greater or less number of inhalant "pores" thereto appertaining. Upon no other view than this does there appear to
be any relation of affinity between the sponges and the Colenterata; and even on this view the general affinities between the
two are not of a very striking nature. In some cases (such as
Euplectella amongst the Silicispongie, and Sycum and Ute amongst




70               MANUAL OF ZOOLOGY.
the Calcispongie) the adult sponge never consists of more than
a single osculum and the pores belonging to it, constituting what
Hweckel terms a single "person." Most sponges, however,
form a "stock," consisting of several such "persons" united
together.
CHAPTER VI.
I.F USORIA.
THE Infusoria of many writers comprise many of the lowest
forms of plants-such as the Diatoms —together with the.Rotifera, a class of minute animals now known to belong to the
Annuloida.  By modern writers, however, the term Infusoria
is used strictly to designate those Prolozoa which possess a
mouth and rudimentary digestive cavity. They are, for this
reason, often called collectively the "stomatode" Protozoa, in
contradistinction to the remaining members of the sub-kingdoml,
which are all "astomatous."  The so-called "suctorial" Izfusoria (Acinele), however, appear to have no definite oral aperture; and the same is the case with the parasitic Opalina,
though there is great doubt as to the propriety of placing this in
the Infusoria at all. The name Infusoria itself is derived from
the fact that the members of the class are often developed in
organic infusions.
The nzf/usoria, or Stoma/ode Protozoa, may be defined as Protozoa which are mostly provided with a mouth and rudimentary
digestive cavity, which do not possess the power of emiltting pseudopodia, but which are furnished with vibratile cilia, or with
contractile filaments.  J7ey are mostly microscopic in size, and
their bodies usually consist of three distinct layers.
The Infusoria may be divided into  three orders-viz.,
Suctoria, Ciliata, and Flagellata, of which the second comprises
the majority of the members of the class, and alone requires
much consideration.
I. ORDER CILIATA.-This order comprises those Infusoria
in which the outer laryer of the body is more or less abundantly
furnished with vibratile cilia, which serve either for locomotion
orfor the procuring offood.  Besides cilia, properly so called,
some of the ciliated Infusoria are provided with styles or jointed
bristles, which are movable, and subserve locomotion; whilst
others have little hooks or unciti, with which they can attach
themselves to foreign bodies. As types of the order, Paramx



PROTOZOA: INFUSORIA.                            7 I
cium and Vorticella may be selected, the former being free,
whilst the latter is permanently fixed in its adult condition.
Paramecium  (fig. Io, c) is a slipper-shaped animalcule, composed externally of a structureless transparent pellicle-the
" cuticle " —which is lined by a layer of firm and consistent sarcode, which is termed the "cortical layer," or the " parenchyma
WIILLIL L3 aIIIILU  dLIL   LVICILCL*  I9  Oo
Fig. so.-Morphology of Infusoria: a Efistylis, a stalked Infusorian; b A single
calyx of the same greatly magnified, showing the ciliated disc which protrudes at
will, and the ciliated internal cavity into which the particles of food are received.
In the substance of the body are the contractile vesicle and smaller food-vacuoles.
c Diagrammatic representation of Para;nocium, showing the funnel-shaped gullet,
the nucleus and nucleolus, food-vacuoles, and two contractile vesicles. d AsSidisca
lynceas; e Perateonma globulosa, a flagellate Infusorian.
of the body," this in turn passing into a central mass of softer
and more diffluent sarcode, known as the "chyme-mass," or
"abdominal cavity."  The "cuticle" is covered with vibratile
cilia, and is perforated by the aperture of the mouth. The
mouth leads into a funnel-shaped gullet, which is not continued
into any distinct digestive sac, but is lost ir the central "chymemass."  Within the "cortical layer" are the "hucleus" and
"nucleolus," and the "contractile vesicle" (or vesicles).  The
nucleus is usually a solid band or rod-shaped body, having a
small spherical particle applied to its exterior, or immersed in
its substance.  This latter is the so called "nucleolus," which
must be carefully distinguished from the nucleolus of a cell,
which occurs in the interior of the nucleus. The contractile
vesicles are clear spaces, which contract and dilate at intervals,
and occasionally exhibit radiating canals passing into the surrounding sarcode. Ordinarily one contractile vesicle is present,
or at most two, but in some cases there may be several. It
has also been maintained that the contractile vesicles communicate with the exterior of the body, but proofs are wanting
on this point.  Whether this should ultimately be established




72               MANUAL OF ZOOLOGY.
or not, there can be little doubt but that the vesicles are a rudimentary form of vascular apparatus. Others, however, hold,
with some probability, that the contractile vesicles are to be
regarded as excretory in function, and that they correspond
more with the water-vascular system of the Annuloida than
with the true blood-vascular system of higher animals. Certain
other spaces termed "vacuoles"' are generally visible in addition to the contractile vesicles. These, however, are probably
merely collections of water surrounding the particles of ingested
food, and performing with them a circulation in the abdominal
cavity, something like the circulation of granules which is seen
in certain vegetable cells. It was the appearance of these
"vacuoles "-which are certainly not permanent-organs-of any
kind-which induced Ehrenberg to term the Infusoria the " Polygastrica," upon the belief that they were so many stomachs.
Paramecium obtains its food by means of the currents of
water which are set up by the constantly-vibrating cilia. The
nutritive particles thus brought to the mouth pass into the
central abdominal cavity, along with the contents of which
they undergo the circulation above spoken of. Indigestible
and fbecal particles appear to be expelled by a distinct anal
aperture, which is situated near the mouth.
Reproduction in Paramcecium is-effected either non-sexually
by fission (i.e., by a simple division of its substance), or by a
true sexual process.  In this latter method two Paramwcia
come together, and adhere closely to one another by their ventral -urfaces.  The " nucleus," which is truly an ovary, enlarges,
and a number of ovules are formed in its interior. In like
manner, the " nucleolus " of each, which is really a testis or sper
marium, also enlarges, and develops in its interior a number
of fusiform or rod-like bodies, which are believed to be spermatozoa. The nucleolus of each then passes into the body of
the other, the act of transference being effected through the
mouth. Contact of the two reproductive elements then takes
place, and a number of germs are produced, which, after their
liberation from the body of the parent, are developed into adult
Param&acia.
Vorticella (fig. i i, c) is a beautiful flower-like Infusorian
which is commonly found in fresh water, adhering to the
stems of aquatic plants. It consists of a bell-shaped body or
"calyx," supported upon the extremity of a slender contractile
stem  or'"pedicle."  The other extremity of the pedicle is
fixed to some foreign body, and its power of contraction is due
to the presence in its interior of a spiral contractile fibre,
which is sometimes called the "stem-muscle."  The edge of




PROTOZOA: INFUSORIA.                  73
the l)ell or calyx is surrounded by a projecting rim or border,
called the "peristome," within which is a circular surface, the
"disc," forming the upper extremity of the so-called "rotatory
organ." The disc is surrounded by a fringe of vibratile cilia,
forming a spiral line which is prolonged into the commencement of the digestive canal. Near the edge of the disc is
situated the mouth, which conducts by its entrance or "vestibulum" into a fusiform canal or "pharynx," which terminates
abruptly in the abdominal cavity. The particles of food are
taken in at the mouth, descend through the short alimentary
canal, and enter the abdominal cavity, where they are subjected
to the general rotation of the "chyme-mass," being finally
excreted by ai anal aperture which is situated near the mouth.
As in Paramecium, the body in Vorticella is composed of an
outer " cuticle," a central " chyme-mass," and an: intermediate
"cortical layer," which contains a contractile vesicle and a
band-like nucleus.
Reproduction in Voricella may take place by fission, or by
gemmation, or by a process of encystation and endogenous
division. In the first of these modes the calyx becomes indented in a longitudinal direction-viz., from the pedicle to
the disc; and the groove thus formed becomes gradually deeper
until the calyx is finally divided into two halves supported
upon the same pedicle. On one of these cups a "posterior" circlet of cilia is then formed in addition to the
"anterior" circlet already existing (i. e., a fringe of cilia is
developed round that end of the calyx which is nearest the
attachment of the pedicle and furthest from the disc). The
cup (fig. I, d), thus furnished with a circlet of cilia at both
extremities, is then detached, and swims about freely. Finally,
the anterior circlet of cilia disappears, and this end of the
calyx puts forth a pedicle and becomes attached to some
foreign object. A new mouth is now formed within what
was before the posterior circlet of cilia; so that the position
and function of the two extremities of the calyx are thus
reversed.
In the second mode of reproduction-namely, that by gemmation-exactly the same phenomena take place, with this
single difference, that in this case the new individual is not
produced by a splitting into two of the adult calyx, but by
means of a bud thrown out from near its proximal extremity.
This bud is composed of a prolongation of the cuticular and
cortical layers of the adult with a caecal diverticulum of the
abdominal cavity or chyme-mass. It soon develops a posterior
circlet of cilia, the connection with the parent is rapidly con



74               MANUAL OF ZOOLOGY.
stricted until complete separation is effected, and then the
process differs in no respect from that described as occurring
in the fissiparous method of reproduction.
In the third mode of reproduction the VortictZla encysts
itself in a capsule, the cilia and pedicle disappear, and the
nucleus breaks up into a number of rounded germs which are
ultimately liberated by the rupture of the cyst, and, after a
short locomotive stage, develop themselves into fresh VorticellZe. How far this process may be truly sexual is not known,
and no form of unequivocal sexual reproduction has hitherto
been shown to occur in the case of Vorticella.
Epistylis is a not uncommon form of fixed Infusorian which
is nearly allied to Vorticella, and differs chiefly in the fact that
the pedicle is much branched, and is rigid and not contractile.
Eipistylis (fig. Io, a) usually occurs in the form of a greyishwhite nap on the stems of water-plants, or on the head of
the common water-beetle, the Dytiscus inarginalis. It consists
of a plant-like branching and re-branching frond, the stems of
which are quite transparent and faintly striated, but are not
contractile, though capable of movement from side to side.
Each branch of the entire colony terminates in an oval calyx,
articulated to the stem by a distinct joint, upon which it can
move from side to side. The calyces are oval or somewhat
campanulate, but have the power of altering their dimensions,
and especially of contracting so as to shorten their. anteroposterior diameter.  Each  calyx terminates  distally in  a
slightly-elevated annular aperture, the margins of which are
regularly toothed.  The calyx appears to be formed by a
hardening of the cuticle, and to form a distinct case, with a
double margin, enclosing the animal. The sarcode-body enclosed within this outer envelope is of a light-brown colour,
and full of minute granules, with larger food-vacuoles and a
well-marked contractile vesicle, which contracts and dilates
two or three times a minute.  The animal can retract itself
entirely within its cup, and can at will exsert a ciliated disc.
This disc (fig. io, b) is inversely conical, and acts as a kind of
plug, and it is provided with two tufts of long cilia, one on
each side. On one side of the protrusible disc is the oral
aperture, which is continued by a distinct and well-marked
gullet into a central ill-defined cavity. Both the entrance of
the gullet and the bottom of the central cavity are provided
with very long, actively-vibrating cilia, some of which are
almost setiform. The entire granular contents of the abdominal cavity undergo a constant though slow rotation.
Carchesiumi is another form which is like Episty/is in consist



PROTOZOA: INFUSORIA                       75
ing of a number of calyces supported upon a branched pedicle,
but differs from Efistylis and agrees with Vaoricella in the fact
that the pedicle is contractile.
Stentor, or the trumpet-animalcule (fig. i i, b), is another
common Infusorian which is closely related to  Vorticella.  It
Fig. IT.-a Vaginicola crystallina; b Sten/or Miileri; c Group of Vorlicellar.d Detached bud of Vorticella, showing the posterior circlet of cilia.
consists of a trumpet-shaped calyx, devoid of a pedicle, but
possessing the power of attaching and detaching itself at will.
When detached it swims by means of the anterior circlet of
cilia, just as the calyx of Vorticella will, if broken from its
stalk.   In  Vaginicola (fig. i i, a) the essential structure is
much the same as in Vorticella, but the body is protected
by a membranous or horny case (" carapace" or "lorica "),
within which the animal can retire.  In this beautiful Infusorian the carapace is certainly a cuticular secretion, but it
appears at the same time to be quite distinct from the true
cuticle itself.
Amongst the structures of the ]/fiisoria which require some
notice are the "pigment spot" and the "trichocysts." The
pigment spot is a brightly-coloured solid particle, generally
red, of very common occurrence in many Infusoria, but of
quite unknown function.  The "trichocysts" are vesicular
bodies, capable of emitting thread-like filaments, and greatly
resembling the urticating cells of many of the Celenterata.
They have been detected in.Bursaria, as well as in various
other members of this order; and they are very like certain
cells which are found in the integument of many Planarians.
II. ORDER SUCTORIA.-This order includes a series of Infusoria of a very anomalous nature.  In Acineta. which may
be taken as the type, the body is covered with a number
5




76                MANUAL OF ZOOLOGY.
of uidiating filamentous tubes, which are furnished at their
extremities with suctorial discs, and are capable both of exsertion and retraction. These retractile tubes both seize the prey
and serve as vehicles for the ingestion of food; hence the
term "polystome," or many-mouthed, has been proposed for
the order by Professor Greene.
III. ORDER FLAGELLATA.-This order comprises those I)fusoria which, like Peridinium, find their means of locomotion
in.long, flexible, lash-like filaments, termed "flagella;" cilia
occasionally being present as well. In some, as in Peranena
(fig. io, e), there is only a single one of these appendages; in
others, as in Anisonema, there are two flagella; whilst in Beteromastix and Pleuronenza we have forms apparently transitional
between the Ciliata and the Elagellata, since both cilia and
flagella are present in these genera. In all their other essential characters the flagellate Infusoria do not differ from the
more typical members of the class.  In one singular form
(Phalansterium intestinale), the organism  consists of numerous
zo6ids, each with a single flagellum and projecting membranous
collar, enveloped basally in slimy sarcode, so as to form a cylindrical colony.
NOCTILUCA.-Amongst the numerous organisms which contribute to the phosphorescence of the sea," one of the commonest is the animalcule known as Noctiluca, the true position
of which has not yet been determined. It is nearly spherical
in shape, having an indention, or "hilum," at one side, close
to which is fixed a long filament, probably used in locomotion.
The body consists of a "cuticle" and  "cortical layer," enclosing a central mass of sarcode. Near the filament there is
a minute oral aperture leading into a short digestive cavity.
A nucleus and vacuoles are also present. From the presence
of a mouth, and from its general structure, Aoctiluca should probably be looked upon as a flagellate ITnfusorian, but it is placed
by M. de Quatrefages amongst the Rhizopoda.
* The diffused luminosity of the sea is mainly due to the AVoctiluca
miliaris; but its partial luminosity is due to various phosphorescent animals, amongst which are the Physalia utriculus (the Portuguese man-of-war),
Medusa,, Tunicata, Annelides, &c. The cause of phosphorescence is variously
stated, being supposed very generally to be caused by a process of slow
combustion analogous to that which takes place in phosphorus when exposed to the atmosphere. Upon the whole, however, it appears that the
phenomenon is a vital process, consisting essentially in the conversion of
nervous force (or vital energy) into light; just as the same force can be
converted by certain fishes into electricity.  This transformation often
requires a special apparatus for its production, but it appears to be sometimes effected by the entire organism.




PR'OTOZOA: INFUSORIA.               77
AFFINITIES OF THE INFUSORIA.-Though generally placed
amongst the Protozoa, of which they form the highest division,
the position of the Infusoria cannot be looked upon as definitely settled. There is a growing opinion amongst competent
authorities that the Infusoria should be entirely removed from
the Protozoa, and that they should be placed amongst the Annuloida, having their nearest allies in the 5urbellarian Worms.
If this change be carried out, the Infusoria and Rotifera, which
older naturalists grouped together, and which modern observers have placed widely apart, will be again brought nearly
together. If the sponges also should be removed from the
Protozoa, as is maintained by some modern observers, then
the entire sub-kingdom of, the Protozoa would contain only
the Gregarinida, Amcebea, Foraminifera, and Radiolaria. At
present, however, there certainly do not appear to be sufficiently decisive grounds for such a step; and the affinities of
the Spongida are certainly more intimate with the typical
Rhizopods than with the Cxelenterata.




CELENTERA TA.
CHAPTER VII.
THE S UB-KZIVGDOM C=CLENTERA TA.
I. CHARACTERS OF THE SUB-KINGDOM.  2. DIVISIONS.
3. GENERAL CHARACTERS OF THE HYDROZOA. 4. EXPLANATION OF TECHNICAL TERMS.
THE sub-kingdom  Ctalenterata (Frey and Leuckhart) may be
considered as the modern representative of the Radiata of
Cuvier. From the Radiata, however, the Echinotdermata and
Scolecida have been removed to form the Annuloida, the entire
sub-kingdom of the Protozoa has been taken away, and the
Polyzoa have been relegated to their proper place amongst the
Miollusca.  Deducting these groups from  the old Radiata,
the residue, comprising most of the animals commonly known
as Polypes or Zoophytes, remains to constitute the modern
Cwlenterata.
The Cwlenterata may be defined as animals whose alimentary
canal communicates freely with the general cavity of the body
("somatic cavity ").  The substance of the body is made up of
two fundamental membranes —-an outer layer, called the " ectoderm," and an inner layer, or "endoderm."  There are no
distinct neural and hamnal regions, and in the great majority of
the members of the sub-kingdom there are no traces of a nervous
system. Peculiar urticating organs, or " thread-cells," are usually
present; and, generally speaking, a radiate condition of the organs
is perceptible, especially in the tentacles with which most are
provided. In all the Colenterata distinct reproductive organs have
been shown to exist.  By Professor Allman the Cxlenterata have
been defined as follows: —-" Animnals composed of numerous
merosomes (body-segments), which are disposed radially round
a longitudinal (antero-posterior) axis; frequently with a determinable antero-posterior and dorso-ventral plane (bilateral); a distinct body-cavity, which always communicates with
the outer world through the mouth."




CCELENTERATA: HYDROZOA.                79
The leading feature which distinguishes'the Cwcenlera/a,
and the one from which the name of the sub-kingdom is
derived, is the peculiar structure of the digestive system. In
the Protozoa, as we have seen, a mouth is only present in the
higher forms, and in no case is there any definite internal
cavity bounded by the walls of the body to which the name
of "body - cavity" or " somatic cavity" could be properly
applied. In animals higher than the Coeentera/a, on the other
hand, there is not only generally a permanent mouth, but the
walls of the body usually enclose a permanent chamber or
"'body-cavity." Further, in most cases, the mouth conducts
into an alimentary canal, which is always distinct from the
body-cavity, never opening into it, but usually passing through
it to open on the surface by another distinct aperture (the
anus). In most cases, therefore, the alimentary canal is a
tube which communicates with the outer world by two apertures-a mouth and anus-but which simply passes through
the body-cavity without in any way Communicating with it.
In the Cwlenterata there is an intermediate condition of parts.
There is a distinct and permanent mouth, and a distinct and
permanent body-cavity, but the mouth opens into, and communicates freely with, the body- cavity.  In some cases
(Hydrozoa) the mouth opens directly into the general bodycavity, which then serves as a digestive cavity as well (fig.
I2). In other cases there intervenes between the mouth and
the body-cavity a short alimentary tube, which communicates
externally with the outer world through the mouth, and opens
below by a wide aperture into the general cavity of the body
(A4ctinozoa, fig. 28). In no case is there a distinct intestinal
canal which runs through the body and opens on the surface
by a mouth at one end and an excretory aperture or anus at
the other.
With regard to the fundamental tissues of the Colentera/a,
there exist two primary membranes, of which one forms the
outer surface of the body, and is called the " ectoderm:"
whilst the other lines the alimentary canal, the general cavity
of the body, and the tubular tentacles, and is termed the
"endoderm."  These membranes correspond with the primitive serous and mucous layers of the germinal area, and become differentiated in opposite directions, the ectoderm growing from within outwards, the endoderm from without inwards.
Each consists of numerous nuclear bodies, or "endopiasts,"
embedded in a granular "intercellular substance" or "periplast;" and each may be rendered more or less complex by
vacuolation or fibrillation.




80               MANUAL OF ZOOLOGY.
In connection with the integument of the Cclenterala, the
organs termed "thread-cells" (" cnidxe," or "nematocysts ")
must be noticed.  These are peculiar cellular bodies, of
various shapes, which probably serve as weapons of offence
and defence, and which communicate to many members of
the sub-kingdom  (e.g., the Sea-blubbers) their well —known
power of stinging.  In the common Hydra the thread-cells
consist of "oval elastic sacs, containing a long coiled filament,
barbed at its base, and serrated along its edges. When fully
developed the sacs are tensely filled with fluid, and the
slightest touch is sufficient to cause the retroversion of the
filament, which then projects beyond the sac for a distance,
which is not uncommonly equal to many times the length of
the latter." — (Huxley.)  (Fig. i2, d.)  Many beautiful modifications of shape are known in the thread-cells of different
Ccelenterates, but their essential structure in all cases is much
the same as in the Hydra.  It is only in few cases, comparatively speaking, that the thread-cells have the power of piercing
and irritating the human skin; but even in the diminutive
Hydra it is probable that they exercise some benumbing and
deleterious influence on the living organisms which may be
captured as prey.  The Celenterata are divided into two
classes, termed respectively the Hydrozoa and the Actinozoa.
CLASS I. HYDROZOA.
The Hydrozoa are defined as Coelenterata in which the walls
of the digestive sac are not separated from that of the general
body-cavity, the two coinciding with one another; She reproductive organs are in the form of external processes of the body-wall.
(Fig. 12, a, b.)
It follows from the above, that, since there is but a single
internal cavity, the body of a Hydrozolin on transverse section
appears as a single tube, the walls of which are formed by
the limits of the combined digestive and somatic cavity.
The Hydrozoa are all aquatic, and the great majority are
marine.   The class includes both  simple and  composite
organisms, the most familiar examples being the common
Fresh-water Polype (Hydra), the Sea-firs (Sertularida), the
Jelly-fishes (Afedusce), and the Portuguese man-of-war (Phy* Thread-cells, though very commonly, if not universally, present in the
Ccelenterata, are nevertheless not peculiar to them. Similar organs have
been shown to exist in several of the Nudibranchiate Mollusca, as well as in
some Annelides (Spio seticornis). There likewise exist analogous organs
(trichocysts) in several of the Infuisol-ia, and in the Planarida.




C(ELENTERATA: HYDROZOA.                81
walia).  Owing to the great difficulty which is ordinarily
experienced by the student in mastering the details of this:lass of animals, it has been thought advisable to introduce
iere a short explanation of some of the technical terms which
ire in more general use in describing these organisms.
GENERAL TERMINOLOGY OF THE HYDROZOA.
Individual.-We have already seen (see Introduction) that
the term "individual," in its zoological sense, must be restricted to "the entire result of the development of a single
fertilised ovum," and that in this sense an individual may
either be simple, like an Amoeba, or may be composite, like a
Sponge, which is produced by an aggregation of amcebiform
particles. If all the parts composing an individual remain
mutually connected, its development is said to be "continuous; " but if any of these parts become separated as indepen(lent beings, the case becomes one of "discontinuous" development. We have seen, also, that however long zo6idal
multiplication may go on, there ultimately arrives in the history
of every individual a period at which sexual reproduction must
be called in to insure the perpetuation of the species throughout time.
Amohgst the Hydrozoa, the individual may be either simple
or compound, and the development may be either continuous
or discontinuous, the following terms being employed to denote the phenomena which occur.
Hydrosoma.-This is the term which is employed to designate the entire body of a Hydrozoin, whether it be simple, as
in the Hydra, or composite, as in a Sertularian.
Polypite.-The alimentary region of a Hydrozoiin is called
a "polypite;" the term "polype " being now restricted to the
same region in the Actinozoa.  In the simple Hydrozoa the
entire organism may be called a " polypite; " but the term is
more appropriately applied to the separate nutritive factors
which together make up a compound Hydrozodn.
Distal and ProximaZ. -These are terms applied to different
extremities of the hydrosoma. It is found that one extremity
grows more quickly than the other, and to this free-growing
end-at which the mouth is usually situated-the term " distal"
is applied. To the more slowly growing end of the hydrosoma
-which is at the same time usually the fixed end-the term
"proximal" is applied. These terms may be used either in
relation to a single polypite in the compound Hydrozoa, or to
the entire hydrosoma, whether simple or compound.




82              MANUAL OF ZOOLOGY.
Cwnosarc.-This is the term which is employed to designate
the common trunk, which unites the separate polypites of any
compound HydrozoMn into a single organic whole.
Polypary.-The term "polypary" or "polypidom" is applied to the horny or chitinous outer covering or envelope
with which many of the Hydrozoa are furnished. These terms
have also not uncommonly been applied to the very similar
structures produced by the much more highly organised Seamats and their allies (Polyzoa), but it is better to restrict their
use entirely to the Hydrozoa.
Zoiids.-In  continuous development the partially independent beings which are produced by gemmation or fission
by the primitive organism, to which they remain permanently
attached, are termed "zo6ids."
In discontinuous development, where certain portions of
the "individual" are separated as completely independent
beings, these detached portions are likewise termed " zodids;"
that which is first formed being distinguished as the "producing zo6id," whilst that which separates from it is known
as the "produced zo6id."  In a great number of ]ydrozoa
there exist two distinct sets of zo6ids, one of which is destined
for the nutrition of the colony, and has nothing to do with
generation, whilst the functions of the other, as far as the
colony is concerned, are wholly reproductive. For te whole
assemblage of the nutritive zodids of a Hydrozodn Professor Allman has proposed the term "trophosome," applying the term
" gonosome " to the entire assemblage of the reproductive zolilds.
In such Hydrozoa, therefore, as possess these two distinct sets
of zo6ids, the " individual," zoologically speaking, is composed
of a trophosome and a gonosome. It follows from this that
neither the trophosome nor the gonosome, however apparently
independent, and though endowed with intrinsic powers of
nutrition and locomotion, can be looked upon as an "individual," in the scientific sense of this term. As a rule, the
zo6ids of the trophosome are all like one another, or are
"homomorphic;" but there are some cases (as in Hydractinia, and in the nematophores of the Plumularidwa) in which
some of the zo6ids of the trophosome are unlike the others.
The zoijids of the gonosome, on the other hand, are normally
unlike, or are "heteromorphic," consisting of two or three
different sets of zo6ids, each with its special duty in the generative functions of the Hydroid Colony.




CCELENTERATA: HYDROZOA.                  83
CHAPTER VIII.
DIVISIONS OF THE HYDROZOA.
SUB-CLASS HYDROIDA.
THE Hydrozoa are divided into four sub-classes-viz., the Hydroida, the Siphonophora, the Lucernarida, and the Discophora.
SUB-CLASS I. HYDROIDA. —This sub-class comprises those
Hydrozoa which consist of an alimentary region or "polypite,"
which is provided with an adherent disc or " hydrorhiza," and
prehensile tentacles.
In some few cases the hydrosoma is composed of a single
polypite only, as in the Hydrida and in some of the Corynida;
but usually there are several polypites united together by
means of a common trunk or " ccenosarc," as in most of the
Corynida and in the orders Sertularida and Campanularida.
Further, in the great majority of cases the "hydrorhiza" is
permanently attached to some foreign object.
The Hydroida comprises four orders-viz., the H-ydrida, the
Corynida, the Sertularida, and the Canqpanularida.
ORDER I. HYDRIDA (Gymnochroa, Hincks).-This order
comprises those Hydrozoa whose " hydrosoma " consists of a
single locomotive polypite, with tentacles and "hydrorhiza," and
with reproductive organs which appear as simple external processes of the body-wall.  The hydr'rhiza is discoid, and no hard
cuticular layer is at any time dewveloped.
The order Ifydrida comprises a single genus only (Hydra),
including the various species of " Fresh-water Polypes,"' as
they are often called. The common Hydra (fig. i 2, c) is
found abundantly in this country, and consists of a tubular
cylindrical body, the "proximal" extremity of which is expanded into an adherent disc or foot-the " hydrorhiza "-by
means of which the animal can attach itself to some foreign
body. It possesses, however, the power of detaching the
hydrorhiza at will, and thus of changing its place. At the
opposite or "distal" extremity of the body is placed the
mouth, surrounded by a circlet of tentacles, which arise a
little distance below the margin of the oral aperture.  The
tentacles vary in number from five to twelve or more, and
they vary considerably in length in different species, being
much shorter than the body in the Hydra viridis, but being
extremely long and filamentous in Hydra fusca. They are
highly extensile and contractile, and serve as organs of pre



84                 MANUAL OF ZOOLOGY.
hension, being capable of retraction till they appear as nothing
more than so many warts or tubercles, and of being extended
to a length which is in some species many times longer than
the body itself.  (In the Hydra fusca the tentacles can be
protruded to a length of more than eight inches.) Each conbz ~   b
Fig. I2.-Morphology of Hydrozoa. a Diagrammatic section of [Hydra. The dark
line is the ectoderm, the fine line and clear space adjacent are the endoderm.
b Hydra viridis, showing a single ovum contained in the body-wall near the
proximal extremity, and two elevations containing spermatozoa near the bases of
the tentacles; c Hydra vulgaris, with an undetached bud; d Thread-cell of the
Hydra, greatly magnified.
sists of a prolongation of both ectoderm and endoderm, enclosing a diverticulum of the somatic cavity, and they are
abundantly furnished with thread-cells. The cylindrical hydrosoma is excavated into a single large cavity, lined by the endoderm, and communicating with the exterior by the mouth.
This-the " somatic cavity "-is the sole digestive cavity with
which the Hydra is provided, the indigestible portions of the
food being rejected by the mouth.
The Hydra possesses a most extraordinary power of resisting mutilation, and of multiplying artificially when mechanically divided.  Into however many pieces a Hydra may be
divided, each and all of these will be developed gradually into
a new and perfect polypite. The remarkable experiments of
Trembley upon this subject are well known, and have been
often repeated, but space will not permit further notice of
them here. Reproduction is effected in the Hydra both
asexually by gemmation, and sexually,-the. former process
being followed in summer, and the latter towards the commencement of winter, few individuals surviving this season.
In the first method the Hydra throws out one or more buds,
generally from near its proximal extremity. These buds at




C(ELENTERATA: ItYDROZOA.                85
first consist simply of a tubular prolongation of the ectoderm
and endoderm, enclosing a caecal diverticulum of the bodycavity; but a mouth and tentacles are soon developed, when
the new being is usually detached as a perfect independent
Hydra. The Hydroe thus produced throw out fresh buds,
often before they are detached from the parent organism, and
in this way reproduction is rapidly carried on.
In the second or sexual mode of reproduction, ova and
spermatozoa are produced in outward processes of the bodywall (fig. I2, b). The spermatozoa are developed in little
conical elevations, which are produced near the bases of the
tentacles, and the ova are enclosed in sacs of much greater
size, situated nearer the fixed or proximal extremity of the
animal. Ordinarily there is but one of these sacs containing
a single ovum, but sometimes there are two. When mature,
the ovum is expelled through the body-wall, and is fecundated
by the spermatozoa, which are simultaneously liberated. - The
embryo appears as a minute, free-swimming, ciliated body. The
serous and mucous layers of the blastoderm (germinal area)
correspond to the ectoderm and endoderm, and for the formation of the perfect Hydra nothing further seems wanting than
the modification of one end of the body into a hydrorhiza, and
the formation of a mouth and tentacles at the other.
ORDER II. CORYNIDA (= TUBULARIDA, the Athecata of
Hincks).-The order Corynida comprises those  fydrozoa
whose hydrosoma is filed by a hydrorhiza, and consists either of
a single polypite, or of several united by a ceenosarc, which usually
develops a firm outer layer or "2polypary."  No "hydrothece"
are present.  "/ The reproductive organs are in the form of gonophores, which vary much in structure, and arise from the sides of
-thepolypites, from the cacnosarc, orfrom gonoblastidia."-(Greene.)
The hydrosoma of the Corynida may consist of a single
polypite, as in Caryomorpha and. Vorticlava, or it may be composed of several united by a ccenosarc, as in Cordy/lo~pora
(fig. I3, a). The order is entirely confined to the sea, with
the single exception of Cordylophora, which inhabits fresh
water. In Tubularia and its allies the organism is protected
by a well-developed external chitinous envelope or "polypary;" but in the other genera belonging to the order the
polypary is either rudimentary or is entirely absent.  The
polypary of the Corynida, when present, is readily distinguished
from that of the Sertularida, by the fact that in the former it
extends only to the base of the polypites; whereas in the latter
it expands to form little cups for the reception of the polypites,
these cups being called "hydrothecte."




t86               MANUAL OF ZOOLOGY.
As regards the reproductive process in the Corynida, the
reproductive elements-are developed in distinct buds or sacs,
Fig. I3.-Morphology of Corynida. a Fragment of Cordylozqhora lacustris, slightly
enlarged; b Fragment of the same considerably enlarged, showing a polypite and
three gonophores in different stages of growth, the largest containing ova; c Portion
of Syncoryne Sarsii with medusiform zobiids budding from between the tentacles.
which are external processes of the body-wall, and have been
aptly termed "gonophores" by Professor Allman.   Strictly
speaking, Dr Allman understands by the term  "gonophore"
only the ultimate generative zo6id, that which immediately produces the generative elements. Great variations exist in the
form and development of these generative buds, and an examination of these leads us to some of the most singular phenomena in the entire animal kingdom.   In some species of
Hydractinia and Coryne, the generative buds or "gonophores"
exist in their simplest form-namely, as sacciform protuberances of the endoderm and ectoderm, enclosing a diverticulum
of the somatic cavity. In this form they are attached to the
" trophosome' by a short stalk, and they are termed " sporosacs" (fig. I4, a).  They are exactly like the buds which we
have already seen to exist in the Hydra, with this difference,
that they are not themselves developed into fresh polypites,
but are simply receptacles in which the essential elements of
generation-the ova and spermatozoa-are prepared, by the
union of which the young Corynid is produced.
In Cordylophora (fig. I3, b) a further advance in structure is
perceptible.  The gonophore now  consists of a closed sac,
from the roof of which depends a hollow process or peduncle
-the " manubrium"-which gives off a system of tubes which
run in the walls of the sac. For reasons which will be immediately evident, the gonophore in this case is said to have a
"disguised" medusoid structure (fig. 14, b).




CCELENTERATA: 1IYDROZOA.                      87
In certain Corynida, however, we meet with a still higher
form of structure, the gonophores being now said to be
" medusoid." In these cases the generative bud is primitively
a simple sac-such as the "sporosac "-but ultimately develops itself into a much more complicated structure.   The
gonophore (fig. I3, c) is now found to be composed of a bellshaped disc, termed the "gonocalyx," which is attached by its
base to the parent organism (the trophosome), and has its
cavity turned outwards.   From  the roof of the gonocalyx,
like the clapper of a bell, there depends a peduncle or
"manubrium," which contains a process of the somatic cavity.
The manubrium gives out at its fixed or proximal end four
prolongations of its cavity, in the form of radiating lateral
tubes, which run to the margin of the bell, where they communicate with one another by means of a single circular canal
which surrounds the mouth of the bell. This system of tubes
constitutes what is known as the system of the "gonocalycine
canals." The gonophore, thus constituted, may remain permanently attached to the parent organism, as in Tubularia
indivisa (fig. I4, c); but in other cases still further changes
ensue. In the higher forms of development (fig. I4, d) the
d             c            b             a
Fig. 14.-Reproductive processes of Hydrozoa. a Sporosac; b Disguised medusoid;
c Attached medusiform gonophore; d Free medusiform gonophore. The cross shading indicates the reproductive organs, ovaria or sperniaria. The part completely
black indicates the cavity of the manubrium and the gonocalycine canals.
manubrium acquires a mouth at its free or distal extremity,
and the gonocalyx becomes detached from the parent. The
gonophore is now free, and behaves in every respect as an
independent being. The gonocalyx is provided with marginal tentacles and with an inward prolongation from its
margin, which partially closes the mouth of the bell, and is
termed the "veil" or "velum."  By the contractions of the
gonocalyx, which now serves as a natatorial organ, the gonophore is propelled through the water. The manubrium, with
the shape, assumes the functions of a polypite, and its cavity
takes upon itself the office of a digestive sac. Growth is




88           - ~    MANUAL OF ZOOLOGY.
rapid, and the gonophore may attain a comparatively gigantic
size, being now absolutely identical with one of those organisms which are commonly called "jelly-fishes," and are technically known as Meditse (fig. I5)- In fact, as we shall afterwards see, most if not all of the gymznophthalmate fMedusie,
originally described as a distinct order of free-swimming Hydrozoa, are in truth merely the liberated generative buds, or' medusiform gonophores," of the permanently-rooted Hydroids.
Finally, the essential generative elements-the ova and spermatozoa-are developed in the walls of the manubrial sac,
between its endoderm and ectoderm, and embryos are produced. These embryos, however, instead of resembling the
organism which immediately gave them birth, develop themselves into the fixed Corynid from which the gonophore was
produced, thus completing the cycle.
As we have seen, the generative
_a...b buds of the Corynida may exist in
the following forms:-I. As " sporot'~~~.. ~ob~ oEg sacs," or simple closed sacs, conI0o    ~ *e,   sisting of ectoderm and endoderm,. ~ ~o~oe~ l 11  with  a central cavity in which
ova and spermatozoa are produced.
2. As "disguised medusoids," in
which there is a central manubrial
process and a rudimentary system
of gonocalycine canals; but the
gonocalyx remains closed.  3. As
complete medusoids, which have a
central manubrium, a complete system of gonocalycine canals, and an
open gonocalyx; but which never
become- detached.  4. As perfect
medusiform  gonophores (fig. 15),
which are detached, and lead an
independent existence for a time,
until the generative elements are
matured. In whichever of these
Fig. I5. — Free medusiform gono- forms the gonophore may be prephore of Clytia 1ohinstoni(after sent, the place of its origin from the
Hincks). a Centra' polypite or
manubrium;bb Radiating gastro- trophosome may vary in different
vascular canals; c Circular canal; species of the order.  i. They may
m Marginal bodies; t Tentacles..                 may
arise from the sides of the polypites,
as in Coryne and Stauridia; 2. They may be produced from the
ccenosarc, as in Cordylophora; 3. They may be produced upon
certain special processes, which are termed "gonoblastidia,"




C(ELENTERATA: HYDROZOA.                 89
as in Hydracdinia and Dicoryne. These gonoblastidia are
processes from the body-wall or ccenosarc, which closely resemble true polypites in form, but differ from them in being
usually devoid of a mouth, and in having shorter tentacles.
As regards the development of the Corynida, the embryo is
very generally, though not always, ciliated at first, and becomes developed into a hydra-form polypite, which fixes itself
to some foreign body, and then (if not belonging to one of the
simple forms) proceeds to produce by gemmation the composite adult. The development of the Corynida (as well as
that of the Sertularida and Iucernarida) obeys the general law,
that the new polypites are developed at, or near, the distal end
of the hydrosoma; so that the distal polypites are the youngest,
the reverse of this obtaining amongst the oceanic Hydrozoa.
The subject of the reproduction of the Corynida having
been treated at some length, so as to apply to the remaining
Hydroida, we shall now give a brief
description of the two leading types
of structure exhibited by the order.
Eudendrium, a genus of the Corynida, which is not uncommonly
found attached to submarine objects, usually  in  tolerably deep
water, may be taken as a good
example of the fixed and composite
division of the order.  The hydrosoma consists of numerous polypites,
united by a ccenosarc, which is more
or less branched, and is defended
by a horny tubular polypary.  The
polypites are borne at the ends of
the branches and branchlets, and
are not contained in "hydrothecae,"
the polypary ending abruptly at their
bases.  The polypites are non-retractile, of a reddish colour, and
provided with about twenty tentacles, arranged round the mouth in
a single row.  Tubularia (fig. I6) is
very similar to Ezudendrium, but the
hydrosoma is either undivided or is  Fig. x6.-Corynida. Fragment of
very slightly branched. The hydro-    TubuZaria iidiz'zsa, natural
soma consists of clustered horny
tubes, of a straw colour, and not unlike straws to look at; hence
the common name of pipe-coralline given to this zoophyte.




90               MANUAL OF ZOOLOGY.
Each tube is filled with a soft, semi-fluid, reddish coenosarc,
and gives exit at its distal extremity to a single polypite. The
polypites are bright red in colour, and are not retractile within
their tubes, the horny polypary extending only to their bases.
The polypites are somewhat conical in shape, the mouth being
placed at the apex of the cone, and they are furnished with
two sets of tentacles.  One set consists of numerous short
tentacles placed directly round the mouth; the other is composed of from thirty to forty tentacles of much greater length,
arising from the polypite about its middle or near the base.
Near the insertion of these tentacles the generative buds are
produced at proper seasons.
Coryomorpha nutans may be taken to represent those Coroynida in which there is no polypary and the hydrosoma is simple.
It is about four inches in length, and is fixed by filamentous
roots to the sand at the bottom  of the sea.  It consists of a
single whitish polypite, striped with pink, and terminating
upwards in a pear-shaped head, round the thickest part of
which is a circlet of from forty to fifty long white tentacles.
Above these comes a series of long branching gonoblastidia,
bearing gonophores, and succeeded by a second shorter set of
tentacles which surround the mouth. The gonophores become
ultimately detached as free-swimming medusoids.
ORDER III. SERTULARIDA (Thecaphora, Hincks).- This
order comprises those Hydrozoa " whose hydrosoma is fixed by
a hydrorhiza, and consists of several polypites, protected by hydrothecce, and connected by a coenosare, which is usually branched and
invested by a very firm outer layer. Reproductize organs in the
form of gonophores arising from the ewnosarc or from gonoblastidia."- (Greene. )
The Sertularida resemble the Corynida in becoming permanently fixed after their embryonic condition by a hydrorhiza,
which is developed from the proximal end of the ccenosarc;
but they differ in the fact that the polypites are invariably protected by "hydrothecoa," or little cup-like expansions of the
polypary (fig. I7, a, b); whilst the hydrosoma is in all cases
composed of more than a single polypite.  The ccenosarc
generally consists of a main stem-or "hydrocaulus"-with
many branches; and it is so plant-like in appearance that the
common Sertularians are almost always mistaken for sea-weeds
by visitors at the seaside.  It is invested by a strong corneous
or chitinous covering, often termed the "periderm."
The polypites are sessile or subsessile, hydra-form, and in all
essential respects identical with those of the Corynida, though
usually smaller. Each polypite consists of a soft, contractile.




CMELENTERATA: HYDROZOA.                        9!
and extensile body, which is furnished at its distal extremity
with a mouth and a circlet of prehensile tentacles, richly furnished with thread-cells. The tentacles have an indistinctly
alternate arrangement.   The mouth opens into a chamber
which occupies the whole length of the polypite, and is to be
regarded as the combined body-cavity and digestive sac. At
its lower end this chamber opens by a constricted aperture
into a tubular cavity which is everywhere excavated in the
substance of the ccenosarc (fig. i7, b). The nutrient particles
Fig. I7. —a Sertularia (Dzihasia) #innata, natural size; a' Fragment of the same
enlarged, carrying a male capsule (o), and showing the hydrothecae (h); b Fragment
of CamPanularia neglecla (after Hincks), showing the polypites contained in their
hydrotheca (h), and also the point at which the coenosarc communicates with the
stomach of the polypite (a).
obtained by each polypite thus serve for the support of the
whole colony, and are distributed throughout the entire
organism. The nutritive fluid prepared in the interior of each
polypite gains access through the above-mentioned aperture to
the cavity of the coenosarc, which by the combined exertions
of the whole assemblage of polypites thus becomes filled with
a granular nutritive liquid.   This coenosarcal fluid is in constant movement, circulating through all parts of the colony,
and thus maintaining its vitality, the cause of the movement
being probably due, in part, at any rate, to the existence of
vibrating cilia. The generative buds (gonophores or ovarian
vesicles) are usually supported upon gonoblastidia, and seldom,
if ever, become detached in the true Sertularids.  They are




92               MANUAL OF ZOOLOGY.
often developed in chitinolls receptacles known as "gonotheca" (fig. I7, o). The young Sertularian on escaping from
the ovum appears as a free-swimming ciliated body, which
soon loses its cilia, fixes itself, and develops a young coenosarc,
by gemmation from which the branching hydrosoma of the
perfect organism is produced.
In Plumularia and some of its allies there occur certain
peculiar organs, probably offensive, to which the name of
"nematophores" has been applied.  Each of these consists of
a process of the coenosarc, which is invested by the horny
polypary, with the exception of the distal extremity, which
remains uncovered, and contains many large thread-cells embedded in it.
ORDER IV. CAMPANULARIDA.-The members of this order
are closely allied to the Sertularida; so closely, indeed, that
they are very often united together into a single group.  The
chief difference consists in the fact that the hydrothecxe of the
Campanularida with their contained polypites are supported
upon conspicuous stalks, thus being terminal in position (fig.
I7, b),; whilst in the Sertularida they are sessile or subsessile,
and are placed laterally upon the branchlets. The gonophores
also in the Campanularida are usually detached as free-swimming medusoids, whereas they remain permanently attached
in the Sertularians. Each medusoid consists of a little transparent glassy bell, from the under surface of which there is
suspended a modified polypite, in the form of a " manubrium"
(fig. I5). The whole organism swims gaily. through the water,
propelled by the contractions of the bell or disc (gonocalyx);
and no one would now suspect that, it was in any way related
to the fixed plant-like zoophyte from which it was originally
budded off. The central polypite is furnished with a mouth at
its distal end, and the mouth opens into a digestive sac. From
the proximal end of this stomach proceed four radiating canals
which extend to the circumference of the disc, where they all
open into a single circular vessel surrounding the mouth of
the bell. From the margins of the disc hang also a number
of delicate extensile filaments or tentacles; and the circumference is still further adorned with a series of brightly-coloured
spots, which are probably organs of sense. The mouth of the
bell is partially closed by a delicate transparent membrane or
shelf, the so-called "veil." Thus constituted, these beautiful
little beings lead an independent and locomotive existence for
a longer or shorter period.  Ultimately, the essential elements
of reproduction are developed in special organs, situated in
the course of the radiating canals of the disc. The resulting




CCELENTERATA: HYDROZOA.                  93
embryos are ciliated and free-swimming, but ultimately fix
themselves, and develop into the plant-like colony; from which
fresh medusoids may be budded off. The ova in the medusiform gonophores are usually developed in the course of the
gonocalycine canals, and not between the ectoderm. and
endoderm of the manubrium, as is the case in the Corynida.
Examples of the order are Campanularia Laomedea, &c The
distinctions between the Sertularida and Campanularzda are
certainly insufficient to justify their being placed in separate
orders. If united together, it would probably be best to adopt
the name Thecaphora (Hincks) for the order, and to employ
the names Sertularida and Camipamularida for the sub-orders.
CHAPTER IX.
S I PH ON OP I O R A.
SUB-CLASS II. SIPHONOPHORA.- The members of this subclass constitute the so-called "Oceanic Hydrozoa.;" and are
rharacterised by the possession of a "free and oceanic hydrosora, consisting of several polypites united by a flexible, contractile, unbranched or szlihtly-branched ccenosarc, the proximal end
of which is usually furnished with'nectocalyces,' and is dilated
itoa a'somatocyst' or into a'pneumatophore.' "-(Greene.)
All the Siphonophora are unattached, and permanently free,
and all are composite. They are singularly delicate organisms,
mostly found at the surface of tropical seas, the Portuguese
man-of-war (Physalia) being the most familiar member of the
group.  The sub-class is divided into' two orders-viz., the
Calycrophoridae and the Physophoaride.
ORDER I. CALYCOPHORIDA. -This order includes those
Sithonoophora whose hydrosoma is free and oceanic, and is propelled by "nectocalyces" attached to its proximal end.  The hydrosoma consists of several polypites, united by an unbranched cwnosarc, which is hizhlyflexible and contractile, and never develops a
hard cuticular layer.  The proximal end of the hydrosoma is
modified into a peculiar cavity called the " somatocyst."  The reproductive organs are in the form of medusiform gonophores produced by buddingfrom the peduncles of the polypites.
In all the Calycophoridae the coenosarc is filiform, cylindrical,
unbranched, and highly contractile, this last property being due
to the presence of abundant muscular fibres. " The proximal




94                 MANUAL OF ZOOLOGY.
end of the ccenosarc dilates a little, and becomes ciliated internally, forming a small chamber" which communicates with
the nectocalycine canals. "At its upper end this chamber is
a little constricted, and so passes, by a more or less narrowed
channel, into a variously-shaped sac, whose walls are directly
continuous with its own, and which will henceforward be termed
the soma/ocyst (fig. i8, 3 b). The endoderm of this sac is ciliated, and it is generally so immensely vacuolated as almost to
X5 —.a                                             a\
a         c
~~~~~~~~~~~I  t~~~~~~~~~.
2                                      3
Fig. I8.-Morphology of the Oceanic Hydrozoa. I. Diagram of the proximal extremity of a.PhysopA/orid. a Pneumatocyst. 2. b/og-'/ia felctet/tr, one of the
CalycAoIhoriZde.  n Nectocalyces; p Polypites; I Tentacles.  3. Diagram of a
Calycophorid. a a' Proximal and distal nectocalyces; b Somatocyst; c Coenosarc;
d Hydrophyllium or bract; e Medusiform gonophore;f Polypite. The dark lines
in figs. x and 3 indicate the endoderm, the light line with the clear space indicates
the ectoderm. (After Huxley.)
obliterate the internal cavity, and give the organ the appearance
of a cellular mass."-(Huxley.)  The polypites in the Calycophoridze often show a well-marked division into three portions,
termed respectively the proximal, median, and distal divisions.
Of these, the " proximal" division is somewhat contracted, and
forms a species of peduncle, which often carries appendages.
The " median " portion is the widest, and may be termed the
"gastric division," as in it the process of digestion is carried
on. It is usually separated from the proximal division by a
valvular inflection of the endoderm, which is known as the
"pyloric valve."  The polypites have only one tentacle "developed near their basal or proximal ends, and provided with
lateral branches ending in saccular cavities," and furnished
with numerous thread-cells.  The proximal ends of the poly



CCELENTERATA: HYDROZOA.                95
pites usually bear certain overlapping plates, of a protective
nature, which are termed "hydrophyllia," or "bracts."  They
are composed of processes of both ectoderm and endoderm
(fig. I8, 3 d), and they always contain a diverticulum from the
somatic cavity, which is called a "phyllocyst."  The Calycophoridae always possess swimming-bells, or "nectocalyces," by
the contractions of which the hydrosoma is propelled through
the water (fig. I8, 2).  The nectocalyx in structure is very
similar to the "gonocalyx" of a medusiform gonophore, as
already described; but the former is devoid of the gastric or
genital sac-the "manubrium"-possessed by the latter. Each
nectocalyx consists of a bell-shaped cup, attached by its base
to the hydrosoma, and provided with a muscular lining in the
interior of its cavity, or " nectosac."  There is also always a
"'velum" or "veil," in the form of a membrane attached to
the mouth of the nectosac round its entire margin, and leaving
a central aperture. The peduncle by which the nectocalyx is
attached to the hydrosoma conveys a canal from -the somatic
cavity, which dilates into a ciliated chamber, and gives off at
least four radiating canals, which proceed to the circumference
of the bell, where they are united by a circular vessel; the
entire system constituting what is known as the system of the
"nectocalycine canals."  In the typical Calycophorida two
nectocalyces only are present, but in some genera there are
more. In Praya the two nectocalyces are so apposed to one
another that a sort of canal is' formed by the union of two
grooves, one of which exists on the- side of each nectocalyx.
This chamber, which is present in a more or less complete
form in all the genera, is termed the "hydrcecium," and the
ccenosarc can be retracted within it for protection.
The reproductive bodies in the Calycophorid&e are in the
form of medusiform gonophores, which are budded from the
peduncles of the polypites, becoming, in many instances, detached to lead an independent existence.  In some Calycophorid&e, as in Abyla, " each segment of the ccenosarc, provided
with a polypite, its tentacle, reproductive organ, and hydrophyllium, as it acquires a certain size, becomes detached, and
leads an independent life-the calyx of its reproductive organ
serving it as a propulsive apparatus. In this condition it may
acquire two or three times the dimensions it had when attached, and some of its parts may become wonderfully altered
in form."-(Huxley.)  To these detached reproductive portions of adult Calycophoridc the term  "Diphyozob3ids" has
been applied.
As regards the development of the Calyco/phoridce, "not




95                 MANUAL OF ZOOLOGY.
only the new polypites, but the new nectocalyces and reproductive organs, and even the branches of the tentacles, are
developed on the proximal side of the old
ones; so that the distal appendages are the
oldest." — (Huxley.)'  The process of development is therefore the reverse of what
obtains amongst the Hydroida.
JDiphyes (fig. I9), which may be. taken
as the type of the Calycophoridwe, consists
N,     \      \(}!#/of a delicate filiform  ccenosarc, provided
proximally with two large mitre-shaped nectocalyces (v, v'), of which one lies entirely
on the distal side of the other.  The pointed
apex of the distal nectocalyx is received into
a special cavity in the proximal nectocalyx.
The "hydrceciumr" (h) is formed partially
by this chamber in the nectocalyx, and partially by an arched groove prolonged upon
I y    the inner surface of the distal nectocalyx,
within which the ccenosarc moves freely up
and down, and can be entirely retracted if
s necessary.  The upper part of the ccenosarc,-a             dilates into a small ciliated cavity, from
which are given off two tubes, which proceed respectively to the distal and proximal
Fig.   -ach-nectocalyces, where they open into the cendoe. Dijhhyes alzendi- tral chamber from which the nectocalycine
culata(after Kolliker). canals take their rise.  The upper portion
v Proximal nectocalyx; z/, Distal necto- of this small ciliated cavity is prolonged
calyx; h Hydrcium;arrying proximally into the larger chamber of the
c Caenosarc, carrying
polypites each with its "' somatocyst."   The ccenosarc (c) bears
bract and tentacle.   polypites, each of which is protected by a
delicate glassy "hydrophyllium."
DIVISIONS OF THE CALYCOPIIORIDAg.-(AFTER HUXL.EY.)
Fam. I. D)izhydae.-Nectocalyces not more than two in number, and of
a polygonal shape. Hydrcecium of the proximal nectocalyx complete, or
closed posteriorly. Hydrophyllia well developed.
Fam. II. S.phwcoanectidwa.-Nectocalyces probably not more than two in
number; the proximal nectocalyx spheroidal, with a complete hydrcecium.
No hydrophyllia (?).
Earn. III. Prayidn.-Nectocalyces two in number; hydroecia incom.
plete and groove-like. Polypites protected by hydrophyllia.
Eam. IV. Hippopodide. -Nectocalyces numerous; hydrcecia incomplete.
Polypites not protected by hydrophyllia.
ORDER II. PHYSOPHORIDME. — This second order of the




CCELENTERATA: HYDROZOA.                  97
Oceanic Hydrozoa comprises those Siphonophora in which the
hydrosoma consists of several polypiles united by a flexible, contractile, unbranched or very slightly branched ccenosarc, the proximal extremity of which is modified into a "pneumatophore," and
is sometimes provided with " nectocalyces."  The polypites have
either a single basal tentacle, or the tentacles arise directly froom
the cewnosarc. "IHydrophy/l7ia" are commonly present.  The reproductive bodies are developed upon gonoblastidia.
The ccenosarc in the Physophoride, like that of the Calycophoridee, is perfectly flexible and contractile; but it is not
necessarily elongated, being sometimes spheroidal or discoidal.
The proximal end of the ccenosarc " expands into a variouslyshaped enlargement, whose walls consist of both ectoderm and
endoderm, and which encloses a wide cavity in free communication with that of the coenosarc, and, like it, full of the nutritive fluid. From the distal end, or apex, of this cavity depends
a' sac, variously shaped, but always with tough, strong, and
elastic walls, composed of a substance which is stated to be
similar to chitine in composition, and more or less completely
filled with air."-(Huxley.)  The large proximal dilatation of
the ccenosarc is termed the "pneumatophore," whilst the chitinous air-sac which it contains is termed the "pneumatocyst"
(fig. i8, I).  The pneumatocyst is held in position by the
reflection of the endoderm of the pneumatophore over it, and
it doubtless acts as a buoy or "float."  In the Portuguese
man-of-war (Physalia) the pneumatocyst communicates with
the exterior by means of an aperture in the ectoderm  of the
pneumatophore.  In Velella and Po rpita the pneumatocyst
communicates with the exterior by means of several openings
called " stigmata;" and from its distal surface depend numerous
slender processes, containing air, and known as "pneumatic
filaments."
The polypites of the Physopqhoridae resemble those of the
Calycophoridae in shape, but the tentacles have a much more
complicated structure, and are sometimes many inches in length,
as in Physalia. The " hydrophyllia " have essentially the same
structure as those of the former order. There occur also in
the Physophoridac certain peculiar bodies, termed " hydrocysts"
or " feelers " (" fihler" and " taster" of the Germans).  These
resemble immature polypites in shape, consisting of a prolongation of both ectoderm and endoderm, usually with a
tentacle, and containing a diverticulum of the somatic cavity,
the distal extremity being closed, and furnished with numerous
large thread-cells.  They are looked upon as " organs of pre



98              MANUAL OF ZOOLOGY.
hension and touch," and they are somewhat analogous to the
" nematophores " of some of the Sertularida.
As regards the reproductive organs, they are developed upon
special processes or "gonoblastidia," and they may remain
permanently attached, or they may be thrown off as freeswimming medusoids.  In many of the Physojlhorid&e the
male and female gonophores differ from one another in form
and size, and they are then termed respectively "androphores" and "gynophores."  As regards their development,
the Physophoridz obey the same general law as the Calycophoridce.
In Physophora the hydrosoma consists of a filiform ccenosarc,
which bears the polypites and their appendages, and dilates
proximally into a pneumatophore.   Below this point the
ccenosarc bears a double row of nectocalyces, which are
channelled on their inner faces to allow of their attachment
to the ccenosarc.  There are no hydrophyllia, but there is
a series of "hydrocysts" on the proximal side of the polypites.
Physalia, or the Portuguese man-of-war (fig. 20, a), is composed of a large, bladder-like, fusiform " float" or pneumatophore-sometimes from eight to nine inches in length-upon
the under surface of which are arranged a number of polypites,
together with highly contractile tentacles of great length, " hydrocysts," and reproductive organs. Physalia is of common
occurrence, floating at the surface of tropical seas; and fleets
of it are not uncommonly driven upon our own shores.
In Velella (fig. 20, b) the hydrosoma consists of a widelyexpanded pneumatophore of a rhomboidal shape, carrying
upon its upper surface a diagonal vertical crest.  Both the
horizontal disc and the vertical crest are composed of a soft
marginal "limb," and a central more consistent "firm part."
" To the distal surface of the firm part of the disc are attached
the several appendages, including, I. a single large polypite,
nearly central in position; 2. numerous small gonoblastidia,
which resemble polypites, and are termed "phyogemmaria;"
and, 3. the reproductive bodies to which these last give rise.
The tentacles are attached, quite independently of the polypites, in a single series along the line where the firm part and
limb of the disc unite. There are no hydrocysts, nectocalyces,
or hydrophyllia.          On all sides the limb is traversed
by an anastomosing system of canals, which are ciliated, and
communicate with the cavities of the phyogemmaria and large
central polypite."-(Greene.)  Velella is about two inches in
length by one and a half in height.  It is of a beautiful blue




C(ELENTERATA: HYDROZOA.                          99
colour and semi-transparent, and it floats at the surface of the
sea, with its vertical crest exposed to the wind as a sail
Fig. 20.-Physo hondk. a Portuguese man-of-war (Physalia uircuius), showing the
fusiform float and the polypites and tentacles (after Huxley); b Velella vuigaris
(after Gosse).
DIVISIONS OF THE PHYSOPHORIDE.-(AFTER HUXLEY.)
Faam. I. Apolemniad.-Hydrosoma with nectocalyces and hydrophyllia,
the latter united with the other organs into groups which are arranged at
considerable intervals along the ccenosarc. Ccenosarc filiform. Pneumatocyst small.
Famr. II. Stefihanomiada.-Hydrosoma with nectocalyces and hydrophyllia, the latter arranged with the other organs in a continuous series.
Ccenosarc filiform. Pneumatocyst small.
Farn. III. Physophoriadz.-Hydrosoma with nectocalyces, but without
hydrophyllia. Distal end of the filiform ccenosarc dilated. Pneumatocyst
small.
Fam. IV. Athorybidt. - Hydrosoma without nectocalyces, but with
hydrophyllia.  Pneumatocyst occupying almost the whole of the globular
ccenosarc.
Famr. V. Rhizohysiad. - Hydrosoma without either nectocalyces or
hydrophyllia. Coenosarc filiform. Pneumatocyst small.
6




100                MANUAL OF ZOOLOGY.
Fam. VI. Physaliada.-Pneumatocyst occupying almost the whole of
the thick and irregularly fusiform ccenosarc. No nectocalyces or hydrophyllia.
Fam. VII. Vdeellida. —Hydrosoma without nectocalyces or hydrophyllia; with short, simple, or branched submarginal tentacles.  A single
central principal polypite. Pneumatocyst flattened, divided into chambers
by numerous concentric partitions, and occupying almost the whole of the
discoidal ccenosarc.
CHAPTER X.
DISCOPHORA.
SUB-CLASS ITI. DISCOPHORA (Acalephce*' in part).-Since this
sub-class contains only a single order, that of the Meduside, a
single definition necessarily suffices for both.  The Medusidac
are defined as "Hydrozoa whose hydrosoma is free and oceanic,
consisting of a single nectocalyx, from the roof of which a single
polypite is suspended.  The nectocalyx is furnished with a system
of canals.  The reproductive organs are as processes either of the
sides of thepolypite or of the- nectocalycine canals."-(Greene.)
The Medusidee comprise most of the organisms commonly
known as Jelly-fishes or Sea-nettles, the last name being derived from the property which some of them possess of severely
stinging the hand, this power being due to the presence of
numerous thread-cells.   As employed by modern naturalists,
the order is very much restricted, and it is by no means improbable that it will ultimately be entirely done away with, very
many of its members having been shown to be really the free
generative buds of other Hydrozoa.  As used here, it corresponds to part of the Gymnophthalmate Medusce of Professor
E. Forbes, the Steganophthalmate Medusc  of the same author
being now placed in the sub-class Lucernarida.
The hydrosoma of one of the Discophora (=a Gymnophthalmate Medusa) is composed of a single gelatinous bell-shaped
* The old sub-class of the Acalepha  contained the Gyrnophthalrnate
Medusae (= the Discophora,) and the Steganophthalmate Medusce (= the
Lucernarida in part), the two being placed in a single order under the
name of Pumlmzoyrada.  The Acalephe also contained the Ctenophora and
the Calvcophoride and Physophoridae, of which the former constituted the
order  Ciliograda, whilst the two latter made up the order Physograda.
The Ctenophora, however, are now generally placed amongst the Actinozoa,
whilst the Calycophoridae and Physophoride constitute the Hydrozoal subclass Siphonophora.




CCELENTERATA: HYDROZOA.                   IOI
swimming organ, the " nectocalyx" or " disc," from the roof of
which a single polypite is suspended (fig. 2 ). The interior of
the nectocalyx is often called the "nectosac," and the term
" codonostoma" has been proposed to designate the open
bF                     a
Fig. 2I.-Morphology of Medusidae. a A Medusid (Thaumantias) seen in profile,
showing the central polypite, the radiating and circular gonocalycine canals, the
marginal vesicles and tentacles, and the reproductive organs; b The same viewed
from below. The dotted line indicates the margin of the velum.
mouth of the bell. The margin of the nectocalyx is produced
inwards to form a species of shelf, running round the margin
of the mouth of the bell, and termed the " veil" or velum,"
by the presence of which the nectocalyx is distinguished from
the somewhat similar "umbrella" of the Lucernarida.  The
endodermal lining of the central polypite or "manubrium"
(sometimes called the "proboscis") is prolonged into four
radiating canals, which run to the periphery of the nectocalyx,
where they are connected by a circular canal which runs round
its circumference, the whole constituting the system of the
"nectocalycine canals" (formerly called the "chylaqueous
canals ").  From the circumference of the nectocalyx depend
marginal tentacles, which are usually hollow processes, composed of both ectoderm and endoderm, and in immediate
connection with the canal system. Also round the circumference of the nectocalyx are disposed certain  "marginal
bodies," of which two kinds may be distinguished.  Of these
the first are termed "vesicles," and consist of rounded sacs
lined by epithelium, and containing one or more solid, motionless concretions-apparently of carbonate of lime-immersed
in a transparent fluid. The second class of marginal bodies,
variously termed " pigment-spots," "eye-specks," or "ocelli,"
consists of little aggregations of pigment enclosed in distinct
cavities. The "vesicles" are probably rudimentary organs of
hearing, and possibly the eye-specks are a rudimentary form of
visual apparatus.  The oral margin of the polypite may be




102              MANUAL OF ZOOLOGY.
simple, or it may be produced into lobes, which are most
frequently four in number. The essential elements of generation are produced in simple expansions either of the wall of
the manubrium or of the radiating nectocalycine canals.
13
Fig 22.-Group of naked-eyed MedusCe. A Sarsia genmmifera, with medusosds
arising from the sides of the central polypite (after Greene); B Modeeria formosa
(after Forbes); C Polyxenia A4 deri (after Gosse).
From the above description it will be evident that the
Medusa is in -all essential respects identical in structure with
the free-swimming generative bud or gonophore of many of
the fixed and oceanic Hydrozoa. Indeed, a great many forms
which were previously included in the Medusid&e have now
been proved to be really of this nature, and it may fairly be
doubted if this will not ultimately be found to apply to all.
As to the value, however, of the order Meduside, the present
state of our knowledge is well expressed by the following conclusions which have been drawn up by Professor Greene:"I. That several of the organisms formerly described as
Medusi'eo are the free gonophores of other orders of Hydro.zoa.
" 2. That the homology of these free gonophores with those
simple expansions of the body-wall which in Hydra and some
other genera are known to be reproductive organs by their
contents alone, is proved alike by the existence of numerous
transitional forms and by an appeal to the phenomena of their
development.




CCELENTERATA: HYDROZOA.                IO3'3. That many of the so-called Afedusida may, from analogy, be regarded as, ill like manner, medusiform gonophores.
" 4. But that there may exist, nevertheless, a group of
MJedusid forms which may give rise by true reproduction to
organisms directly resembling their parents, and therefore
worthy of being placed in a separate order under the name
Afedusidce."
The same authority concludes by remarking that to the
order as above defined "may be referred provisionally that
large assemblage of forms anatomically similar to true rAiedusidae, but whose development is unknown." Besides the large
group of forms thus temporarily admitted, all the Trachynemidie
and -Eginicde are stated by Gegenbauer to fulfil the conditions
of the above definition, and should, therefore, be looked upon
as true Meduside.
As to the development of these true Meduside, little is
known for certain. It appears, however, that in Trac/zynemra,.Eginopsis, and other genera, the embryo is directly developed
into a form resembling its parent, without passing through any
intermediate changes of form.  It is hardly necessary to remark that this is not the case with the embryos of a medusiform
gonophore, these being developed into the sexless HNdrozoin
by which the medusoid was produced.
In this connection, allusion may be made to the long-known
fact that certain medusiform gonophores are capable of producing independent forms directly resembling themselves, but
this is by a process of gemmation, and not by one of true reproduction.  Technically these are called "tritozobids," as
being derived from organisms which are themselves but the
generative zooids of another being. This singular phenomenon
has been observed in various medusiform gonophores (e.g.,
Sarsia gemmifera, fig. 22, A), the buds springing in different
species from the gonocalycine canals, from the tentacles, or
from the sides of the polypite or manubrium.
The "naked-eyed" Medusae, though mostly very diminutive
in point of size, are exceedingly elegant and attractive when
examined in a living condition, resembling little bells of transparent glass, adorned here and there with the most brilliant
colours. They occur in their proper localities and at proper
seasons in the most enormous numbers.  They are mostly
phosphorescent, or capable of giving out light at night, and
they appear to be one of the principal sources of the luminosity of the sea. It does not seem, however, that they phosphoresce, unless irritated or excited in some manner.




104             MANUAL OF ZOOLOGY.
CHAPTER XI.
LUCE RNAl RZIDl AND GRAPTOLITIDzE.
SUB-CLASS IV. LUCERNARIDA (AcalepheZ, in part).-The menibers of this sub-class may be defined as Hydrozoa " whose hydrosoma has its base developed into an' umbrella,' in the walls of
which the reproductive organs are produced. "-(Greene.)
A large number of forms included in the Lucernarida were
described by Edward Forbes under the name of Steganoplithalmate Medusc, being in many external characters closely similar
to the Afiduside. These "hidden-eyed" Medusce are familiar
to every one as " sea-blubbers" or "sea-jellies," and they
occur in great numbers round our coasts during the summer
months. The resemblance to the little jelly-fishes is especially
strong between the disc or "nectocalyx" of the true MirdusidrZ
and the "umbrella" of the Lucernarida, the latter being often
a bell-shaped swimming organ, with marginal tentacles, and
containing one or more polypites. These analogous structures
(figs. 22 and 25) are, however, distinguished as follows:I. The "umbrella" of the Lucernarida is never furnished with
a "velum," as is the nectocalyx of the Meduside.  2. The
radiating canals in the former are never less than eight in
number, and they send off numerous anastomosing branches,
which join to form an intricate network; whereas in the latter
they are rarely more than four in number, and though they
may subdivide, they do not anastomose. 3. In the place of
the separate and unprotected "vesicles" and "ocelli" of the
Miedusidce, the marginal bodies of the Lucernarida consist of
these bodies combined together into single organs, which are
termed "lithocysts," and which are protected externally by a
sort of hood.
The Lucernarida admit of being divided into three orders
-viz., the Lucernariadaw, the Pelagide, and the Rhizostomidee.
ORDER I. LUCERNARIADA. —This order includes those Lucernarida which have only a single polypile, are fixed by a proximal
hydrorhiza, and possess short tentacles on the margin of the. umbrella.  The reproductive elements "are developed in the primitive
hydrosoma without the intervention of free zoboids."-(Greene.)
In Lucernaria (fig. 23), which may be taken as the type of
the order, the body is campanulate or cup-shaped, and is
attached proximally at its smaller extremity by a hydrorhiza,
which, however, like that of the Hydra, is not permanently
fixed. When detached, the animal is able to swim with toler



CCELENTERATA: HYDROZOA.                  I05
able rapidity by means of the alternate contraction and expansion of the umbrella. Around the margin of the umbrella are
tufts of short tentacular processes, and in its centre is a po!ypite with a quadrangular, four-lobed
mouth.  "In transverse section the
polypite may be described as somewhat quadrilateral, with a sinuous outline, which expands at its four angles
to form  as many deep longitudinal
folds, within which the simple generative bands are lodged." - (Greene.)
Wide longitudinal canals are formed
by septa passing from the walls of the
polypite to the inner surface of the cup,
and a circular canal runs immediately
beneath the insertion of the tentacles.
The reproductive elements are produced within the body of Lucernaria
itself, without the intervention of any
generative zo6id.
ORDER II. PELAGIDrE.-This order
is defined as including  Lucernarida
which possess a single polypite only, and
an umbrella with marginal tentacles.
The reproductive elements "are developed
in a free umbrella, which either consti-  Fig 23.-Lucernariadae. Lututes the primitive hydrosoma, or is pro-    cernaria auricula attached
to apiece of sea-weed (after
duced byfission from an attached Lucer-   Johnston).
naroid."-(Greene.)
Two types, therefore, exist in the Pelagida. The one type
is represented by a fixed " trophosome," resembling Lucernaria,
but distinguished from it by the fact that the generative elements are not'developed in the primitive hydrosoma, but in a
free "gonosome," which is produced for the purpose. The
second type, represented by Pelagia itself, is permanently free,
thereby differing from Lucernaria, which it approaches, on the
other hand, in the fact that its generative elements are produced in its own umbrella without the intervention of free
generative zobids.  Pelagia, however, differs considerably in
structure from Lucernaria, and in all essential characters is not
anatomically separable from a Steganophthalmnate Medusid. The
process of reproduction as displayed in the first section of the
Pelagidna will be considered when treating of that of the Rhizostomida, there being no important difference between the
two, except as concerns the structure of the generative zo6ids.




io6             MANUAL OF ZOOLOGY.
ORDER III. RHIZOSTOMIDA:. -The members of this order
are defined as being Lucernarida, in which the reproductive
elements are developed in free zodids, produced by fission from  attached LLucernaroids. The umbrella of the generative zod~ids is
without marginal tentacles, and the polypites are " numerous,
modified, forming with the genitalia a dendrziform mass depending
from the umbrella." —(Greene.)
The following is a brief summary of the life-history of a
member of this extraordinary order (fig. 24), the illustration,
however, representing the development of Chrysaora, one of the
Pelagidce, in which the phenomena are essentially the same. The
embryo is a free-swimming, oblong, ciliated body, termed a
" planula " (a), of a very minute size, and composed of an outer
and inner layer enclosing a central cavity. The- planula soon
becomes pear-shaped, and a depression is formed at its larger
end. "Next, the narrower end attaches itself to some submarine body, whilst the depression at the opposite extremity,
becoming deeper and deeper, at length communicates with the
interior cavity. Thus, a mouth is formed, around which may
be seen four small protuberances, the rudiments of tentacula.
In the interspaces of these four new tentacles arise; others in
quick succession make their appearance, until a circlet of numerous filiform appendages, containing thread-cells, surrounds
the distal margin of the'Hydra-tuba' (b), as the young organism at this stage of its career has been termed by Sir J. G.
Dalyell. The mouth, in the mean time, from being a mere
quadrilateral orifice, grows and lengthens itself so as to constitute a true polypite, occupying the axis of the inverted umbrella
or disc, which supports the marginal tentacles.  The space
between the walls of the polypite and umbrella is divided into
longitudinal canals, whose relations to the rest of the organism,
and, indeed, the whole structure of Hydra-tuba, closely resemble what may be seen in LLucernaria."-(Greene, Manual
of Cowlenterata.)  The Hydra-tuba thus constitutes the fixed
" Lucernaroid," or the " trophosome " of one of the Rhizostomidce.  In height it is less than half an inch, but it possesses
the power of forming, by gemmation, large colonies, which may
remain in this condition for years, the organism itself being
incapable of producing the essential elements of generation.
Under certain circumstances, however, reproductive zo6ids are
produced by the following singular process. (fig. 24). The
Hydra-tuba becomes elongated, and becomes marked by a series of grooves or circular indentations, extending transversely
across the body from a little below the tentacles to a little above
the fixed extremity. At this stage the organism was described




CCELENTERATA: HYDROZOA.                      107
as new  by Sars, under the name "Scypf istoma" (c).   The
annulations or constrictions go on deepening, and become
lobed at their margin, till the Scyphistoma assumes the aspect
of a pile of saucers, arranged one upon another with their cond                      l
d        C
Fig. 24.-Development of Lucernarida (Chrysaora). a Ciiiated embryo or " planula;"
b Hydra-tuba; c Hydra-tuba undergoing fission, or "Scyphistoma;" dtThe fission
still further advanced, constituting the " Strobila;" e A form still further advanced,.n which a fresh circlet of tentacles has been developed near the base; f Freeswimming medusoid or "Ephyra," produced by fission from the hydra-tuba.
cave surfaces upwards.  This stage was described by Sars
under the name of " Strobila " (d). The tentacular fringe which
originally surrounded the margin of the Hydra-tuba now disappears, and -a new circlet is developed below the annulations,
at a point a little above the fixed extremity of the Strobila (e).
"The disc-like segments above the tentacles gradually fall off,
and, swimming freely by the contractions of the lobed margin
which each presents, they have been described by Eschscholtz
as true Medusidez   under the name of Epjhyrze" (f).  Each
Ephyra, however, soon shows its true nature by becoming
developed into a free-swimming reproductive body, usually of
large size, with umbrella, hooded lithocysts and tentacles,
constituting, in fact, a Steganophthalnzate Medusa.   The reproductive zo6id now swims freely by the contractions of its
umbrella, and it eats voraciously and increases largely in size.
The essential elements of generation are then developed in
special cavities in the umbrella, and the fertilised ova, when
liberated, appear as free-swimming, ciliated " planulae," which
fix themselves, become Hydra-tuba, and commence again the
cycle of phenomena which we have above described.
As regards the size of these reproductive zodids as compared
with the organism by which they are given off, it may be mentioned that the umbrella of Cyanea arctica has been found in




108              MANUAL OF ZOOLOGY.
one specimen to be seven feet in diameter, with tentacles more
than fifty feet in length, the fixed Lucernaroid from which it
was produced not being
more than half an inch in
height.
As regards the special
structure of these gigantic
reproductive bodies, considerable differences obtain
between the Rhizostomide
and that section of the
Pelagidce  in which  this
method of reproduction is
employed. In the Pdagidce,
namely, - the  generative
zobids possess a general,
though chiefly mimetic, resemblance both to the
genuine Discophora and to
the free-swimming medusiform  gonophores of so
many of the Hydrozoa, and
they have the following
structure.  Each (fig. 25)
Fig. 25.-Hidden-eyed Medusae. Generative consists of- a bell-shaped,
zooid of one of the Pelagidca (Ckhrysaora gelatinous disc, the   umhysoscella), after Gosse.      gelatinous ds, the   umbrella," from the roof of
which is suspended a large polypite, the lips of which are extended into lobed processes often of considerable length, " the
folds of which serve as temporary receptacles for the ova in
the earlier stages of their development."  The polypite —
manubrium  or proboscis-is hollowed into a digestive sac,
which communicates with a cavity in the roof of the umbrella,
from which arise a series of radiating canals, the so-called
"chylaqueous canals."  These canals, which are never less
than eight in number, branch freely and anastomose as they
pass towards the periphery of the umbrella, where the entire
series is connected by a circular marginal canal.  This, in
turn, sends tubular processes into the marginal tentacles, which
are often of great length.  Besides the tentacles, the margin of
the umbrella is furnished with a series of peculiar bodies,
termed "lithocysts," each of which is protected by a sort of
process or hood derived from the ectoderm, and consists
essentially of a combined " vesicle " and " pigment-spot," such
as have been described as occurring in the Medusidce.  These




CCELENTERATA: HYDROZOA.                      I09
marginal btodies likewise communicate with the chylaqueous
canals. The reproductive elements "are lodged in saccular
processes of the lower portion of the central cavity, immedia
Fig. 26.-Rhizostomidte. Generative zo6id of Rhizostorza (after Owen).  a Umbrella; bb " Stomatodendra," covered with clan;ate tentacles and minute polypites;
cc Anastomosing network of canals.
ately above the bases of the radiating canals, and, being
usually of some bright colour, form a conspicuous cross shining
through the thickness of the disc."-(Greene.)
In the Rhizostomida  the reproductive zo6ids (fig. 26) differ
from those we have just described as occurring in the first
section of the Pelagidce, in not possessing tentacles on the
margin of the umbrella, and in having the simple central
polypite replaced by a composite dendriform process, which
bears numerous polypites, projects far below the umbrella,
and is thus described by Professor Huxley:-" In the Rhizostomidzc (fig. 26) a complex, tree-like mass, whose branches, the'stomatodendra,' end in, and are covered by, minute polypites,
interspersed with clavate tentacula, is suspended from the middle
of the umbrella in a very singular way. The main trunks of the
dependent polypiferous tree, in fact, unite above into a thick,
flat, quadrate disc, the'syndendrium,' which is suspended by
four stout pillars, the'dendrostyles,' one springing from each




110             MANUAL OF ZOOLOGY.
angle, to four corresponding points on the under surface of the
umbrella, equidistant from its centre. Under the middle of the
umbrella, therefore, is a chamber, whose floor is formed by the
quadrate disc, whilst its roof is constituted by the under wall of
the central cavity of the umbrella, and its sides are open. The
reproductive elements are developed within radiating folded
diverticula of the roof of this genital cavity."
It appears, finally, that amongst the old Pulmograde Acalephae, or amongst what would commonly be called Jelly-fishes,
we have the following distinct sets of beings, which resemble
each other more or less closely in appearance, but differ in
their true nature:i. Free medusiform gonophores of various Corynida, Serlularida, Campanularida, and the Oceanic Hydrozoa.
2. True JIedusidee, entirely resembling the former in anatomical structure, but differing in the fact that their ova do
not give rise to a fixed zo6id, but to free-swimming organisms exactly like the parent hydrosoma (Trachynemide and,Eginide).
3. Hydrozoa, which are provided with an "umbrella" (with
all the peculiarities belonging to this structure), but which reproduce themselves without the intervention of free generative
zo6ids produced by fission (Pelagia).
4. The free generative zo6ids of most of the Pelagidze, with
an umbrella and a single polypite, the primitive hydrosoma
being fixed and sexless (Aurelia, Cyanea, &c.)
5. The free generative zodids of the Rhizoslomidze, with an
umbrella and a complex central tree bearing many polypites
(Rhizostoma, Cethea, &c.)
Of these five classes of organisms, Nos. I and 2 constitute
the Gymnophthalmate Medusae of Professor E. Forbes, whilst
Nos. 3, 4, and 5 are the Steganophthalmate Miedusce of the
same naturalist.
SUB-CLASS V. GRAPTOLITIDE. —The organisms included at
present under this head are all extinct, and they are in many
respects so dissimilar, and their structure is so far from being
entirely understood, that it is doubtful if any definition can
be framed which will include all the supposed members of the
family. The following definition, however, will include all the
most typical Graptolites:Hydrosoma compound, occasionally branched, consisting of
numerous polypites united by a ccenosarc; the latter being
enclosed in a strong tubular polypary, whilst the former were
protected by hydrothecae. In the great majority of Graptolites
the hydrosoma was certainly unattached; but in some aberrant




CCELENTERATA: IYDROZOA.                  III
forms-doubtfully belonging to the sub-class —there is reason
to believe that the hydrosoma was fixed. The polypites are
never separated from the coenosarc by any partition. In many
cases the hydrosoma was strengthened by a solid chitinous rod,
the "solid axis," somewhat analogous to the chitinous rod recently described by Professor Allman in the singular Polyzo6n,'Rhabdopaezura.
From the above definition, it will be seen that the nearest
living allies to the Graptolites are the Sertularians. In point
of fact, if we do not insist upon the presence of a " solid axis "
as part of the definition, the Graptolites differ from the Sertularians in no essential point, save that the hydrosoma is
always attached in the latter, and was certainly free in the
most typical examples of the former. Indeed, certain forms
at present placed among the Graptolites-such as Ptilograpsus
and Dendrograpsus-are so similar to some living Sertularians,
that it might be well to remove them altogether from the
Graptolitidac, and to regard them as extinct representatives of
the Sertularida.
As regards the value of the "solid axis" as an element in
defining Graptolites, we fear that much stress cannot be laid
upon its presence or absence. It is true that it is present
in all the most characteristic members of the sub-class, but
it seems to be certainly absent in.some-e.g., in Retiolites
Geinitzianus, and in all species of Rastrites-and there do
not seem to be sufficient grounds for excluding these from
the Graptolitid&e on this account alone.
Taking such a simple Graptolite as G. sagittarius (fig. 27, I)
as the type of the sub-class, the hydrosoma is found to consist
of the " solid axis," the " common canal," and the " cellules."
The entire polypary is corneous and flexible, and the solid
axis is a cylindrical fibrous rod, which gives support to the
entire organism, and is often prolonged beyond one or both
ends of the hydrosoma. The common canal is a tube which
encloses the ccenosarc, and gives origin to a series of cellules,
these being little cups corresponding to "hydrothecoe," and
enclosing the polypites. Not only are the essential details of
the structure-with the exception of the solid axis-strictly
comparable with that of a Sertularian, but there is a good
evidence, as shown by Hall and the author, that the reproductive process was also carried on in a manner similar to what
we have seen in the other Hydroida-namely, by generative
buds or gonophores.
No Graptolite, however, has hitherto been certainly proved
to have been fixed by a "hydrorhiza," and it is only in




112               MANUAL OF ZOOLOGY.
certain aberrant forms that there are any traces of a "hydrocaulus."
Besides the simple forms of
Graptolites with a row of cellules
c b    Z                 on one side (monoprionidian) (fig.
27, 2,) there  are others with a
row  of cellules on each side (diprionidian) (fig. 27, 3).  Many other
curious modifications are known;
but there is only another peculi~   arity which  is worthy of notice
zI     4   g    here.  This is the occurrence in
several genera  of a  basal corneous disc or cup, which is pro~2  ~     i bably the homologue of the "float"
or " pneumatophore" of the Physo3   phoridae. (For distribution of Graptolites see Distribution of Hydrozoa in Time.)
As regards their mode of ocFig. 27.-Morphology of Graptolites. currence, Graptolites are usually
I. Portion of Graptolites sagittar- found as glistening, pyritous imius enlarged; a Solid axis; b Common canal; c Cellules. 2. Mon- pressions, with a silvery lustre.  In
oprionidian Graptolite (G. argen- some cases, however, they are found
teus). 3. Diprionidian Graptolite      
(Dilografisusfiristis, variety with in relief.
long basal spines).
CHAPTER XII.
DISTRIBUTION OF THE HYDROZOA.
I. DISTRIBUTION OF HYDROZOA  IN  SPACE.-The genera of
Hydrozoa have a wide distribution, the mode of reproduction
amongst the fixed forms being such as to insure their extension
over considerable areas. The various species of Hydra are of
common occurrence in the fresh waters of Europe. Cordylophora, the sole remaining fresh-water genus, has not been
found to occur out of the north temperate zone. All the
other Hydrozoa, without a known exception, are marine in
their habits.  The fixed forms-viz., the Corynida, Sertularida,
and Campanularida-are represented more or less abundantly
in almost all seas, extending from the littoral zone to considerable depths.  The oceanic Hydrozoa, Calycophoridce and




SCELENTERATA: HYDROZOA.                 I I 3
PhysophoridZe, are chiefly characteristic of tropical seas; but
they are found also in the Mediterranean, and even in seas not
far from, or even within, the Arctic circle.
II. DISTRIBUTION OF HYDROZOA IN TIME.-With the exception of the impression of a Medusa said to have been observed
by Professor Agassiz in the fine-grained lithographic slate of
Solenhofen (Oolite), there are no fossil remains which would
be universally conceded to be of a flydrozoal nature. The
Oldhamia of the Cambrian rocks of Ireland has, indeed,
been regarded as belonging to the Hydrozoa; but it is believed
by Mr Salter to be really a plant.  It consists of a main
stem with numerous secondary branches, springing from the
axis in an umbellate manner, but exhibiting no traces of
hydrothecae.
The occurrence of Corynida in a fossil condition can hardly
be said to be free from doubt. Remains probably referable to
this order have been, however, recently discovered in the Palaeozoic Rocks. The oldest of these was described by the
author some years ago from the Lower Silurian rocks of Dumfriesshire under the name of Corynoides. More lately a form
called Paleocoryne has been described from the Carboniferous
rocks of Scotland.
The Sertularida and Campanularida are not certainly known
to occur in a fossil condition. The fossils called Dendrograpsus,
Callogralpsus, Pilograpsus, and Dictyonema, all at present placed
amongst the Graptolites, are, however, not improbably truly
referable to the Sertularida.
There can be little doubt but that the large and singular
family of the Graptolitid&e should really be looked upon as
extinct H-ydrozoa, though good authorities still place them
amongst the Polyzoa.. As regards their distribution two facts
are chiefly noticeable. In the first place, no Graptolite, except
the doubtful genus Dictyonema, has hitherto been found to occur above the Silurian rocks.
The Graptolites may therefore
be regarded as characteristic
fossils of the Silurian period.
Secondly, the diprionidian
Graptolites, or those with a    Fig. 28.-Didymogra -fras.
row of cellules on each side
(genera Diilograpsus, Climacograpsus, and Dicranograpsus),
have never yet been certainly shown to occur above the horizon of the Lower Silurian rocks. The common genus Didymograpsus (comprising the " twin " Graptolites, fig. 28) is still
more characteristic of the Lower Silurian period. In Didymo



I14              MANUAL OF ZOOLOGY.
grapsus the polypary consists of two lateral symmetrical
branches, with cellules on one side only, springing from a
central point or base, which is usually marked by a little spine
or " radicle."
CHAPTER XIII.
A C TINOZOA.
I. GENERAL CHARACTERS OF THE ACTINOZOA. 2. CHARACTERS OF THE ZOANTHARIA. 3. ZOANTHARIA MALACODERMATA.  4. ZOANTHARIA  SCLEROBASICA.  5. ZOANTHARIA SCLERODERMATA.
CLASS II. ACTINOZOA. —The Actinozoa are defined as CGl-.:nterata with a dziferentiated digestive sac opening below into the
somatic cavity, but separated from the body-walls by an intervening "perivisceral space," which is divided into a series of cozpartments by vertical partitions, or " mesenteries," to the faces of which
the reproductive organs are attached.
The Acinozaoa (fig. 30), therefore, differ fundamentally from
the Hydrozoa in this, that whereas in the latter the digestive
cavity is identical with the somatic cavity, in the former there
is a distinct digestive sac, which opens, indeed, into the
somatic cavity, but is, nevertheless, separated from it by an
intervening perivisceral space. As a result of this, the body of
a typical Actinozoin (fig. 29), exhibits on transverse section two
concentric tubes, one formed by the digestive sac, the other by
the parietes of the body; whereas the transverse section of a
Hydrozonz exhibits but a single tube, formed by the walls of
the combined digestive and somatic cavity.
Histologically, the tissues of the Actinozoa are essentially the
same as those of the Hydrozoa, consisting of the two fundamental layers, the "ectoderm " and the " endoderm."  In the
Actinozoa, however, there is a much greater tendency to a
differentiation of these into specialised structures, and in some
members of the class muscular fibres are well developed. The
ectoderm, especially, shows a tendency to break up into two
layers, which are differentiated in opposite directions from an
intermediate zone, and are termed by Huxley the "ecderon "
and "enderon," corresponding respectively to the epidermis
and derma of man. Cilia are often present, especially in the
interior of the somatic cavity, where they serve to promote a




CCELENTERATA: ACTINOZOA.                            I I
circulation of the digestive fluids contained therein. The sole
digestive apparatus in the Actinozoa consists of a tubular
stomach-sac, which communicates freely with the outer world
Bi'  b
Transverse section of an  c.  a Digestive sac;  Wall of the
Fig. 29.-A Transverse section of an Actinozoon. a Digestive sac; b Wall of the
body; m Mesenteries connecting the stomach with the body-walls, and dividing the
space between them into a number of vertical compartments. B Transverse section
of a Hydrozod)a, showing the single tube formed by the walls of the body.
by means of the mouth, and opens inferiorly directly into the
general body-cavity.  In  most, the "perivisceral space "'between the body-walls and the digestive sac is subdivided into
compartments by a series of vertical lamellae, which are called
the  "mesenteries"  (fig. 30, b).   Upon  the  faces  of these
Fig. 3o. —Morphology of Actinozoa. Diagrammatic vertical section of Actinia.
a Stomach-sac; b Mesentery; c Craspedum; d Tentacle.
are borne the reproductive organs in the form of band-like
ovaria or spermaria.
Thread-cells, often of very complicated structure, are almost
universally present, some of the C/enog5hora having been asserted
to be without them; and some of the Actinozoa are able to
sting very severely.




1I6            MANUAL OF ZOOLOGY.
A nervous system has not yet been proved to exist in any of
the Actinozoa, except in the Ctenaophora, and in none are there
any traces of a vascular system.
Distinct reproductive organs occur in all the Actinozoa, but
these are internal, and are never in the form of external processes as in the Hydrozoa.  Sexual reproduction occurs in all
the members of the class, but in many forms gemmation or
fission constitutes an equally common mode of increase.
Some Actinozoa, therefore, such as the common Sea-anemones,
are simple organisms; whilst others, such as the reef-building
corals, are composite, the act of genmmation or fission giving
rise to colonies composed of numerous zooids united by a
ccenosarc.  In these cases the separate zo6ids are termed
"polypes," the term  "polypite" being restricted to the Hydrozoa.  In the simple Actinozoa, however, the term "polype"
is employed to designate the entire organism. In other words,
the " actinosoma," or entire body of any ActinozooMn, may be
composed of a single " polype," or of several such, produced by
a process of continuous gemmation or fission, and united by a
common connecting structure, or coenosarc.
Most of the Actinozoa are permanently fixed; some, like
the Sea-anemones, possess a small amount of locomotive
power; and one order, the Ctenophora, is composed of highly
active, free-swimming organisms. Some of the Actinozoa are
unprovided with any hard structure or support, as in the Seaanemones and in all the Ctenophora; but a large number
secrete a calcareous or horny, or partially calcareous and partially horny, framework or skeleton, which is termed the " coral,"
or " corallum."
The Actinozoa are divided into four orders-viz., the Zodntharia, the Alcyonaria, the Rugosa, and the Ctenophora;
but the last is sometimes placed amongst the Hydrozoa, and it
has been recently proposed to remove the Rugosa also to the
same class.
ORDER I. ZOANTHARIA.-The Zoantharia or " Helianthoid
Polypes " are defined by the disposition of their soft parts in
multzples of five or six, and by the possession of simple, usually
numerous, tentacles.  There may be no corallum, or rarely a
" sclerobasic" one.  Usually there is a " sclerodermic " corallum,
in which the sepia in each corallite, like the mesenteries, are arranged in multijples offive or six.
The Zoantharia are divided into three sub-orders, the Zoantharia malacodermata, the Z. sclerobasica, and the Z. scierodermata; according as the corallum is entirely absent or very
rudimentary, is " sclerobasic," or is " sclerodermic."




CCELENTERATA: ACTINOZOA.                I 17
SUB-ORDER I. ZOANTHARIA MALACODERMATA.- -In this section of the Zoantharia there is either no corallum or a very ru —
dimentary one, in the form of a few scattered spicules. The
"actinosoma" is usually composed of but a single polype.
(The term " actinosoma " is a very convenient one to express
in the Actinozoa what " hydrosoma " expresses in the Hydrozoa,
namely, the entire organism, whether simple or compound.)
There are three families in this section, of which the Actinide will require a somewhat detailed examination, since they
may be taken as typical of the entire class of the Actinozoa.
FAMILY I. ACTINIDE. —The members of this family are
commonly known as Sea-anemones, and are distinguished by
having no evident corallum, by being rarely compound, and
by having the power of locomotion.
The body of a Sea-anemone (fig. 31, a) is a truncated cone,
or a short cylinder, termed the "column," and is of a soft,
leathery consistence. The two extremities of the column are
//P
a 
Fig. 3.-Morphology of Actinidae. a Actiozin rose; b A rachnactis albida.
(After Gosse.)
termed respectively the "base" and the "disc," the former
constituting the sucker, whereby the animal attaches itself at
will, whilst the mouth is situated in the centre of the latter.
In a few cases (Cerianthus and Peachia) the centre of the base
is perforated, but the object of this arrangement is unknown.
Between the mouth and the circumference of the disc is a flat
space, without appendages of any kind, termed the " peristomial
space." Round the circumference of the disc are placed
numerous tentacles, usually retractile, arranged in alternating
rows, and amounting to as many as 200 in number in the




I8             MANUAL OF ZOOLOGV.
common Actinia. The tentacles are tubular prolongations of
the ectoderm and endoderm, containing diverticula from the
somatic chambers, and sometimes having apertures at their
free extremities. The mouth leads directly into the stomach,
which is a wide membranous tube, opening by a large aperture into the general body-cavity below, and extending about
half-way between the mouth and the base. The wide space
between the stomach and column-wall is subdivided into
a number of compartments by radiating vertical lamellx,
termed the "primary mesenteries," arising on the one hand
from the inner surface of the body-wall, and attached on the
other to the external surface of the stomach. As the stomach
is considerably shorter that the column, it follows that the
inner edges of the primary mesenteries below the stomach are
free; and these free edges, curving at first outwards and then
downward and inwards, are ultimately attached to the centre
of the base. Besides the primary mesenteries, there are other
lamelle which also arise from the body-wall, but which do
not reach so far as the outer surface of the stomach, and are
called " secondary" and " tertiary" mesenteries, according to
their breadth. The reproductive organs are in the form of
reddish bands, which contain ova and spermatozoa, and are
situated on the faces of the mesenteries.  Most of the Actinize
are dicecious-that is to say, the same individual does not
develop both ova and spermatozoa. Along the free margins
of the mesenteries there also occur certain singular convoluted
cords, charged with thread-cells, and termed "craspeda," the
function of which is-not yet understood.  It is believed, however, that the apertures, termed "cinclides," in the columnwalls of some of the Actinidc, are for the emission of the
craspeda. No traces of a nervous system have as yet been
proved to exist in any Actinia.
The embryo of the Actinice is a free-swimming ciliated
body, at first rounded, but afterwards somewhat ovate.'The
rudimentary mouth is soon marked out by a depression at the
larger extremity; thread-cells appear as a layer in the ectoderm; a fold is prolonged inwards from the mouth to form
the digestive sac; and the primitive tentacles are at first either
five or six in number, but usually double themselves rapidly.
FAMILY II. ILYANTHIDAE.-In this family there;s no corallum,
and the polypes are single and free, with a rounded or tapering
base (fig. 3i, b). Ilyan/hus is in all essential respects identical with the ordinary Ac/iniz, but it is of a pointed or conical
shape, the base being much attenuated, though whether its
habit of life is free or not, is a matter of some uncertainty.




CCELENTERATA: ACTINOZOA.                 I 1 )
Arachnactis is certainly free, and, according to Professor E.
Forbes, it can not only swim like a jelly-fish, but " it can convert its posterior extremity into a suctorial disc, and fix itself to
bodies in the manner of an Actinia." It is by no means certain, however, that Arachnactis is a mature form, and there is
some reason to suppose that it is merely the young stage of
some at present unknown Actinozooin.
FAMILY III. ZOANTHIDE. —In the Zoanthicea there is a spicular corallum, and the polypes are attached by a fleshy or
coriaceous base or ccenosarc. In Zoanthus the separate polypes
closely resemble small Actiniwe, but they are united together
at their bases by a thin fleshy ccenosarc.
SUB-ORDER II. ZOANTHARIA SCLEROBASICA.-The members
of this sub-order are always composite, and always possess a
corallum, but this is " sclerobasic," and there are no spicular
tissue-secretions.
It appears advisable to explain here what is understood by
the terms "sclerobasic" and "sclerodermic," as applied to
corals.  The "corallum" is the term which is applied to the
hard structures deposited by the tissues of any Actinozolin,
many of which are so familiarly known as "corals."  Usually
the corallum is composed of carbonate of lime; but it may be
corneous, or partly corneous and partly calcareous. Whatever
their composition may be, all coralla may be divided into two
sections, termed respectively " sclerobasic" and "sclerodermic,"
which must be carefully distinguished from one another. The
"sclerobasic" corallum, of which the red coral of commerce
may be taken as the type, is in reality an exoskeleton, somewhat analogous to the shell of a Crustacean, being a true
tegumentary secretion. At the same time it is not a shell or
external envelope, but it forms an axis, upon which the entire
actinosoma is spread. The actinosoma, in fact, is inverted,
and the "sclerobasis" is secreted by the outer surface of the
ectoderm. The sclerobasic corallum is therefore truly "outside the bases of the polypes and their connecting ccenosarc,
which, at the same time, receive support from the hard axis
which they serve to conceal." —(Greene.) Upon this view, the
sclerobasis is termed "foot-secretion" by Mr Dana.  In other
words, the sclerobasic coral is a hard skeleton which belongs
solely to the cznosarc of the actinosoma, and which can therefobre be produced by a compound organism only.
The " sclerodermic" corallum, on the other hand, is secreted
within the bodies of the polypes, apparently by the inner layer
of the ectoderm-the "enderon" of Huxley-and it is therefore termed "tissue-secretion" by Mr Dana.  In the sclero



120               MANUAL OF ZOOLOGY.
dermic corallum  each polype has a complete skeleton of its
own, and the entire coral may consist of one such skeleton, or
of several such united by the calcareous matter of the ccenosarc.
b
Fig. 32.-Morphology of Corals a,Cup of Acerzrzderia ananas, showing calicular
gemmation, enlarged; b Diagram of Rugose Coral (Polycelia profunda), showing
the quadripartite arrangement of the septa; c Diagram of a recent coral, showing
the sextuple arrangement of the septa; dVertical section of Canmoqhylum f/exzuosum, showing tabulae.
A sclerodermic corallum, therefore, like tne animal which produces it, may be simple or composite, according as it is produced by a single polype or by several united by a ccenosarc.
It consists, therefore, of a single calcareous cup, or " corallite;"
or of several such united by a common calcareous bond or basis,
the "ccenenchyma."  Taking a single "corallite" (fig. 32, d)
as the type, we find that it shows its origin and nature plainly
in its form. It consists of a cylindrical or conical tube of carbonate of lime, the outer wall of which is called the "theca."
The upper part of the space included by the "theca" is vacant,
and it is termed the cup or "calice;" but the lower part is subdivided into a series of chambers, or "loculi," by a series of
radiating, vertical, calcareous plates, which are called the
"septa" (fig. 32, b).  The septa extend from the inner surface
of the theca towards its centre, where they usually unite to
form  an axial column, called the "columella."  Many of the
septa, however, do not reach the centre, but stop short at
some distance from the columella, often being broken up into
upright pillars, called "pali." The parts thus described as
essentially composing a corallite in a typical sclerodermic
corallum are related in the most obvious manner to the soft
structures of the animal by which they are secreted. Thus,
the "theca " clearly corresponds to the "column-wall," or thc
general wall of the body; the "columella," when present, cor



C(ELENTERATA: ACTINOZOA.                       121
responds to " that part of the enderon which forms the floor of
the somatic cavity below the digestive sac;" whilst the "septa"
correspond to the " mesenteries," and, like them, are called
" primary " and " secondary," according as they reach the columella or fall short of it. When there are several corallites, the
bond of union between them, the "ccenenchyma," is secreted by
the " ccenosarc," to which it corresponds. In many Actinozoa,
however, the sclerodermic corallum is not present in the typical
form above described, but simply in the form of calcareous
spicules or nodules scattered through the tissues of the animal.
There are, also, members of the class in which both a sclerodermic and a sclerobasic corallum are present, the latter constituting
the main skeleton, whilst the former is represented by scattered
spicules. The coral tissue itself is known as " sclerenchyma,"
and it varies considerably in texture, being sometimes extremely compact, and at other times very loosely put together.
From what has been said it will be seen that a sclerobasic
corallum can easily be distinguished from a sclerodermic by
inspection; the former (fig. 33, b) being usually more or less
Fig. 33.-Sclerodermic and Sclerobasic Corals. a Portion of branch of Dendr-oqjhyllia
nigrescens, a sclerodermic coral (after Dana); b Longitudinal section of Isis
hipiuris, a sclerobasic coral, exhibiting the external bark or ccenosarc, with its embedded polypes, supported by the internal axis or skeleton (after Jones).
smooth, and being invariably devoid of the cups or receptacles
for the separate polypes, which are always present in the latter
(fig. 33, a).  The more important variations of detail which
occur in both classes of corals will be noticed under the differ.




122             MANUAL OF ZOOLOGY.
ent families in which they occur. It only remains to add that
doubt has been thrown by eminent zoologists upon the validity of the general distinction between sclerobasic and sclerodermic corals, as above defined.
Returning now to the Zoant/zaria Sclerobasica, we find the
sub-order to contain the two families of the Antiz5athidac and
the Hyalonemada? (or Hyalochoetida).  Of these the Antzipathide
are chiefly noticeable because of their likeness to some of the
Gorgonide, from which, however, they are readily distinguished
by the fact that the number of their tentacles is a multiple of
six, whereas in the latter it is a multiple of four. Antipathzes
itself possesses a horny sclerobasic corallum, which may be
simple or branched, and is covered with numerous small
polypes, united together by a ccenosarc, and possessing six
tentacles each.
The second family, that of the Hyalonernadae, contains the
so-called "Glass-zoophytes," the true nature and position of
which has been a subject of much controversy. By Dr Gray
the Hyalonemadce are believed to be true Actinozoa, and he
defines them as follows:-" Social Zoanthoid polypes secreting
a central, siliceous, internal, axial coil for their support. The
upper half of the coil covered by a uniform cylindrical bark,
regularly studded with retractile polypes." The lower portion
of the siliceous rope-like axis, which looks exactly like a skein
of threads of glass, is sunk in the sand at the bottom of the
sea. The upper portion of the Hyalonema is often occupied
by a cup-shaped sponge, called Carteria, which Dr Gray
believes to be a parasitic growth.  By Professors LUven,
Perceval Wright, Wyville Thomson, and others, the sponge
Carteria is looked upon as the true artificer of the siliceous rope,
and the polypes are regarded as parasitic, and as referable to
Palythoa.  This last view, by which Hyalonemna would be
placed amongst the siliceous sponges, appears, upon the whole,
to be most probably the correct one. In this case there is no
Actinozoin, as far as is yet known, which possesses the power
of secreting a siliceous skeleton, in this respect presenting a
striking contrast to the Protozoa.
SUB-ORDER III. ZOANTHARIA SCLERODERMATA.-The mem —
bers of this sub-order include the great bulk of the coral-producing or "coralligenous" zoophytes of recent seas. They
are defined by the possession of a sclerodermic corallum, the
parts of which are arranged in multiples of five or six. The
actinosoma may be simple, consisting of a single polype, or it
may be composite, consisting of several polypes united by a
coenosarc.




CELENTERATA: ACTINOZOA.                123
The divisions of the sub-order are founded upon the nature
of the corallum, for the due comprehension of which it will
be necessary to consider some points in connection with these
structures somewhat more minutely. As already described, a
typical corallite consists of an outer wall or " theca," with a
cup or "calice" above, and divided below into numerous
chambers or " loculi " by vertical partitions or " septa." Often
the larger or "primary" septa coalesce centrally to form a
median calcareous rod or "columella." The chief additional
structures to be remarked are what are known as "tabulae,"
and'' dissepiments."  The " tabulae" (fig. 32, d) are transverse
plates or floors running at right angles to the axis of the corallite, and dividing the theca into so many horizontal compartments or stories, each of which is vertically subdivided by the
septa, when these exist. As a rule, however, the septa. are
absent when there are tabulke, though the two structures coexist in many extinct corals. The "dissepiments" are incomplete transverse plates, which, "growing from the sides of the
septa, interfere, to a greater or less extent, with the perfect
continuity of the loculi." —(Greene.) -The septa, too, are often
furnished with styliform or spine-like processes growing from
their sides, which often meet so as to form "transverse props
extending across the loculi like the bars of a grate, and termed'synapticule."'
The Zoantharia Sclerodermafa are divided into the four
following groups, founded upon the characters of the corallum:I. Tabulata.-Septa rudimentary, or entirely absent; tabule well developed, and dividing the visceral chamber into a
series of stories.
2. Perforata. - Septa well developed; dissepiments rudimentary; no tabulae. Corallum composed of porous sclerenchyma.
3. A.porosa. -Septa well developed, lamellar; no tabule.
Corallum composed of compact, imperforate sclerenchyma.
4. Tubulosa. —Septa indicated by mere striae; thece pyriform, occasionally united by a basal ccenenchyma.
GEMMATION AND FISSION AMONGST CORALS. —As regards
the modes in which the composite corals are produced, the
following is a summary of Professor Greene's remarks upon
this subject. (See Celenterata, p. I85 et seq.) The produc.
tion of the composite Actinozoa is effected either by gemmation or by fission. In the former method three varieties have
been -distinguished, termed respectively "basal," "parietal,"
and "calicular" gemmation.




124              MANUAL OF ZOOLOGY.
In basal gemmation the mode of increase is by means of
a rudimentary coenosarc, which is put forth by the original
polype, and from which the young polype-buds are produced.
It "affords very different products according as the ccenosarc
remains soft, or deposits a ccenenchyma; appears under the
form of stolons, or of stouter connecting stems; or even
spreads out in several directions as a continuous horizontal
expansion;" in which last case the youngest polypes are, of
course, those nearest to the periphery of the mass.
The parietal mode of gemmation is the commonest, and it
gives rise chiefly to dendroid, or tree-like, corals.  In this
method the buds are produced from the sides of the original
polype, and they often repeat the process indefinitely.
Calicular gemmation is not known to occur in any recent
coral, but it was a common mode of increase amongst extinct
forms. In this method " the primitive polype sends up from
its oral disc two or more similar buds; these, in their turn,
produce other young polypes, and thus the process is repeated
until an inverted pyramidal mass of considerable size is producedall the parts of which rest upon the narrow base of the
first budding polype (fig. 32, a). Fission in the Actinozoa differs
from gemmation chiefly in the fact, that the polypes produced
fissiparously resemble one another in organisation, and often
in.size, as soon as they become distinct. In gemmation, on
the other hand, the polype-bud consists primarily of a mere
process of ectoderm and endoderm, enclosing a caecal process
of the somatic cavity, and a mouth and other structures are at
first wanting. Amongst the coralligenous Actinozoa fission is
usually effected by "oral cleavage," the divisional groove commencing at the oral disc, and deepening to a certain extent,
the proximal extremity always remaining undivided.  More
rarely, fission "is effected by the separation of small portions
from the attached base of the primitive organism, whose form
and structure they subsequently, by gradual development, tend
to assume."
"The coral-structures which result from a repetition of the
fissiparous process are of two principal kinds, according as
they tend most to increase in a vertical or in a horizontal
direction. In the first of these cases the corallum is cewspitose,
or tufted, convex onI its distal aspect, and resolvable into a
succession of short diverging pairs of branches, each resulting
from the division of a single corallite." In the second case
the coral becomes lamellar. " Here the secondary corallites
are united throughout their whole height, and disposed- in a
linear series, the entire mass presenting one continuous theca."




C(ELENTERATA: ALCYONARIA.                125
Both these forms of corallum " are liable to become massive by
the union of several rows or tufts of corallites throughout the
whole or a portion of their height. An illustration of this is
afforded by the large gyrate corallum of Meandrina, over the
surface of whose spheroidal mass the calicine region of the
combined corallites winds in so complex a manner as at once,
to suggest that resemblance to the convolutions of the brain
which its popular name of, Brain-stone Coral has been devised
to indicate."
CHAPTER XIV.
ALCYONARIA.
ORDER II. ALCYONARIA. —The second great division of living
Actinozoa is that of the Alcyonaria, defined by the possession
of polypes awit eight pinnately-fringed tentacles, the mesenteries
and somatic chambers being also some multiple of four. -She corallum, when present, is usually sclerobasic, or spicular; if "Lthecr"
are present, as is rarely the case, there are no sep/a.
The Alcyonaria or "Asteroid Polypes" differ numerically
from the Zoantharia in having their soft parts arranged in
multiples offour, instead offive or six, as in the latter. Their
tentacles, too, are pinnate, and are not simply rounded.
Numerically the Alcyonaria agree with the extinct order
Rugosa, but the latter invariably possess a well-developed
sclerodermic corallum, the thece of which exhibit either septa
or tabule, or both combined.
With the exception of the single genus Raimeia, the Aldyonaria are all composite, their polypes being connected together
by a common ccenosarc, " through which permeate prolongations of the somatic cavity of each, forming a sort of canal
system, whose several parts freely communicate," and permit
of a free circulation of nutrient fluids. As a rule, the entire
colony forms a lobate or branched mass. Anatomically the
polypes of the Alcyonaria do not differ in any essential particular from those of the Zoantharia; the numerical distinction being the one by which they are chiefly separated from
one another.  The Alcyonaria are divided into four fanmilies,
viz., the Alcyonide, the Tubijporidc, the Pennatulida, and the
Gorgonid&e.
FAMILY I. ALCYONIDn. —This family is characterised by the
possession of a fixed actinosoma, which is provided with a




126              MANUAL OF ZOOLOGY.
sclerodermic corallum in the form of calcareous spicula embedded in the tissues. The spicules are mostly fusiform in
shape, and are generally present both in the polypes themselves and in the connecting ccenosarc; but there is no central
solid axis.
Alcyonium may be taken as the type of the family, and it
is well known to fishermen under the name of "Dead-men's
fingers." It forms spongy-looking, orange-coloured crusts or
lobate masses, which are attached to submarine objects, and
are covered with little stellate apertures, through which the
delicate polypes can be protruded and retracted at will. The
polypes communicate with one another by an anastomosing
system of aquiferous tubes, and the corallum is in the form of
cruciform, calcareous spicula scattered through its substance.
In the allied Sarcodictyon the actinosoma is creeping and linear.
FAMILY II. TUBIPORIDE.-In the 2Tubiporidw, or "organpipe corals," of which T. musica is a familiar example, there is
a well-developed sclerodermic corallum, with thecae, but without septa. The corallum is composed of a number of brightred, tubular, cylindrical thecae, which are united together
externally by horizontal plates or floors, which are termed
"epithecae," and represent external tabulae.  The polypes are
usually bright green in colour, and possess eight tentacles
each.
FAMILY III. PENNATULID.-. The Pennatulidz, or " Seapens," are defined by their free habit, and by the possession
of a sclerobasic, rod-like corallum, sometimes associated with
sclerodermic spicules.
Pennatula (fig. 34), or the " Cock's-comb," consists of a free
ccenosarc, the upper end of which is fringed on both sides
with feather-like lateral pinne, which bear the polypes; whilst
its proximal end is smooth and fleshy, and is probably sunk in
the mud of the sea-bottom.  This latter portion of the ccenosarc is likewise strengthened by a long, slender, styliform
sclerobasis, resembling a rod in shape, whilst spicula occur
also in the tentacles and ectoderm.  The general colour of
Pennatula is a deep reddish purple, the proximal extremity of
the ccenosarc being orange-yellow. Our British species (Pennatula phosphorea) varies from two to four inches in length,
and is found on muddy bottoms in tolerably deep water. Its
specific name is derived from the fact that it phosphoresces
brilliantly when irritated.
In Virgularia (fig. 35), which, like Pennatula, occurs not
uncommonly in British seas, the actinosoma is much longer
and more slender than in the preceding, and the polype-bear



C(ELENTERATA: ALCYONARIA.                      I27
ing fringes are short. The polypes have eight tentacles. The
sclerobasis is in the form of a long calcareous rod, like a knitting-needle, and part of it is usually naked. No spicula are
found in the tissues of Virgularia.  In the nearly-allied Pazo
naria the polype-mass is quadrangular in shape.
a
Fig. 35. - Pennatulidie.
Virgularia mirabizis.
a A portion of the
stem in the living condition, enlarged; b
Fig. 34.-Pefnnatula #hosltkorea          Portion of the stem in
(after Johnston).                  its dead condition.
FAMILY IV. GORGONIDlE. -  In the Gorgonidce, or "Seashrubs," there is an arborescent ccenosarc permanently rooted
and provided with a grooved, or sulcate, branched sclerobasis,
which is sometimes associated with true tissue- secretions,
termed " dermo-sclerites."
The sclerobasis of the Gorgonida varies a good deal in its
composition. In some it is corneous, and these have often
been confounded with the Antipiathidee, amongst the Zoantharia.
The distinction, however, between them is easy, when it is
remembered that the polypes in the Gorgonidaz have tentacles
in multiples offour, whilst in the Antipathidae they are in sixes.
The sclerobasis, too, in the former is always marked by grooves,
whereas in the latter it is always either smooth or spinulous




128             MANUAL OF ZOOLOGY.
In Isis (fig. 33, 3) and  fopsea the sclerobasis consists of alternate calcareous and horny segments, branches being developed
in the former from the calcareous, and in the latter from the
horny segments.
In Coraliium rubrum, the "red coral" of commerce, the
sclerobasis is unarticulate, or unjointed, and is entirely calcareous. It is the most familiar member of the family, and is
largely imported for ornamental purposes. Red coral consists
of a branched densely calcareous sclerobasis, which is finely
grooved upon its surface, and is of a bright-red colour. The
corallum  is invested by a coenosarc, also of a red colour,
which is studded by the apertures for the polypes, which are
white, and possess eight pinnately - fringed tentacles.  The
entire coenosarc is channelled out by a number of anastomosing canals, which communicate with the somatic cavities of the
polypes, and are said to be in direct communication with the
external medium by means of numerous perforations in their
walls. The entire canal system is filled with a nutrient fluid,
containing corpuscles, and known as the "milk."
CHAPTER XV.
RUGOSA.
ORDER III. RUGOSA.-The members of this order are entirely
extinct, and, with the exception of Holocystis eleans from the
Lower Cretaceous rocks, and a few more modern forms, are
not known to occur in deposits younger than the Palxeozoic
epoch. With the soft parts of the Rugosa we are, of course,
entirely unacquainted, and the definition of the order must
therefore be founded upon the characters of the corallum.
The corallum in the Rugosa is highly developed, sclerodermic,
with true thecm, and often presenting both septa and tabulke
combined. The septa are in multiples of four (fig. 32, b),
unlike the recent sclerodermic coralla, in which they are in
multiples of five or six. There is, further, no true ccenenchyma.  Some of the Rugosa are simple; but others are composite, increasing either by parietal or by calicular gemmation.
Recently it has been shown that some very abnormal Rugose
corals were provided with a lid or operculum, closing the
mouth of the calice. In the genus Calceola, formerly referred
to the Brachiopoda, and very abundant in certain parts of the




CCELENTERATA: ACTINOZOA.               I29
Devonian System, the operculum consisted of a single valve or
piece.  In Gonioy5zy/lum four valves were present, and in
Cystiikhyllum Jrismatzicum there were four or more valves in
the operculum. It is worthy of notice that some recent corals
(species of Prirnnoa, Paramuricea, and others) exhibit also a
more or less complete operculum. According to Professor
Agassiz, the Rugosa and the Tabulate division of the Zoantharia
ought not to be considered as belonging to the Adctinozoa,
but should be placed amongst the Hydrozoa.  This radical
change, however, cannot be accepted without the production
of very conclusive evidence in its favour. A strong argument against referring the Rugose and Tabulate Corals, as
proposed by Agassiz, to the Hydrozoa, is their possession in
most cases of well-developed septa, implying, of course, the
existence in the living animal of mesenteries, structures which
are wholly wanting in the Hydrozoa.
DISTINCTIONS BETWEEN THE CORALLA OF THE ORDERS OF
AcTINozoA.-Having now considered all the orders of the
Actinozoa in which coralla are developed, it may be as well
briefly to review their more striking differences.
In the first place, a sclerobasic corallum may be distinguished by inspection from a sclerodermic corallum by the fact
that the latter, unless composed simply of spicules, presents
the cups or "thecae," in which the polypes were contained;
the surface of the former being invariably destitute of these
receptacles.
A sclerobasic corallum is found in the families Antziathidte
and Hyalonemnadae(?) amongst the Zoantharia, and in the families
Pennatulidae and Gorgonidce amongst the Alcyonaria; the following being the differences between them.:I. Antizpathidce.-Sclerobasis spinulous or smooth; tentacles
and soft parts in multiples of six.
2. Hyalonemade (?). —Sclerobasis siliceous, composed of
numerous threads; tentacles in multiples of five.
3. Pennatulidce.-Sclerobasis sulcate, free; soft parts in multiples of four.
4. Gorgonidce. — Sclerobasis sulcate, attached proximally;
soft parts in multiples of four.
Sclerodermic coralla fall under two heads, according as they
are simply composed of scattered spicules, or are provided with
true thecce.
I. Spicular coralla occur in the Zoantharia Mfalacodermnafa
(occasionally), and in the Alcyonide; and no differences can
be stated between the coralla themselves. The animals, however, differ entirely, the soft parts of the former being in mul



I30             MANUAL OF ZOOLOGY.
tiples of five or six, those of the latter being in multiples of
four.
II. A thecal sclerodermic corallum occurs in three distinct
sections of Aclinozoa:- I. In the Zoantharia Sclerodermata.
2. In.he Tubiporide, amongst the Alcyonaria; and, 3. In
the Rugosa; and the following are the distinctions between
them:I. Zoantharia Sclerodermata.-Septa in multiples of five or
six, sometimes absent; tabulae often present.
2. Tubiporide. —Septa absent; thecam united externally, by
distinct, horizontal " epithecae."
3. Rugosa.-Septa in multiples of four; tabula usually present.
CHAPTER XVI.
CTENOPHORA.
ORDER IV. CTENOPHORA.-The Ctenophora comprise " transparent, oceanic, gelatinous Actinozoa, swimming by means of'c/enophores,' or parallel rows of cilia disposed in comb-like
plates. No corallum."-(Greene.)
The members of this order are all free-swimming organisms,
and they are. placed by many amongst the Hydrozoa, from
which, however, they appear to be clearly separated by the
possession of a differentiated digestive sac, as well as by their
analogies with the Actinozoa, and their generally superior
degree of organisation.
Pleurobrachia (Cydhipe) (fig. 36) may be taken as the type
of the order, the structure of all being similar to this in essential points. Pleurobrachia possesses a transparent, colourless,
gelatinous, melon-shaped body, or "actinosoma," in which the
two poles of the sphere are termed respectively the " oral" and
"apical," and the rest of the body constitutes the "interpolar
region."  At the oral pole is the transverse mouth, bounded
by lateral, slightly protuberant margins.  "Eight meridional
bands, or'ctenophores' bearing -the comb - like fringes, or
characteristic organs of locomotion, traverse at definite intervals the interpolar region, which they divide into an equal
number of lune-like lobes, termed the "actinomeres"; but
this division of the body does not extend into the immediate
vicinity of the poles, before reaching which the ctenophores
gradually diminish in diameter. each terminating in a point."



CCELENTERATA: ACTINOZOA.                I3 I
(Greene.) The normal number of the ctenophores appears to
be eight, and each consists of a band of surface elevated transversely into a number of ridges, to each of which a fringe of
cilia is attached, so as to form a comb-like plate. The cilia in
the middle of these transverse ridges are the longest, and they
gradually diminish in length towards the sides, so that the
form of each comb is somewhat crescentic. Besides the comblike groups of vibratile cilia, Pleurobrachia is provided with
two very long and flexible tentacular processes, which are
fringed on one side with smaller cirrhi.  These filamentous
processes arise each from a sac, situated on one of the lateral
actinomeres, within which they can be completely and instantaneously retracted at the will of the animal.
Fi,g. 36.-Ctenophora. Pleuzrobrachziiapileus.
The mouth of Pleurobrachia (fig. 37, a) opens into a fusiform digestive sac, or stomach (b), the lower part of which is
provided with brown cells, supposed to discharge the functions
of a liver.  The stomach opens below into a shorter and wider
cavity (c), termed the " funnel," from which two canals diverge
in the direction of the vertical axis of the organism, to open
at the " apical pole." These canals are known as the "' apical
canals" (e), and their apertures as the "apical pores." From
the funnel two other pairs of canals are given off. Of these,
one pair-known as the " paragastric canals "-turns upwards,
one running parallel to the digestive sac on each side (d), and
" terminating coecally before quite reaching the oral extremity."
The second pair of canals (i)-the so-called " radial canals"branch off from the funnel laterally, each dividing into two,




132                MANUAL OF ZOOLOGY.
and then again into two, as they proceed towards the periphery of the body.   Thus, the two "primary" radial canals
produce four "secondary" canals (k), and these, in turn, give
rise to eight " tertiary" radial canals (1), which finally terminate by opening "at right angles into an equal number of
longitudinal vessels, the' ctenophoral canals' (f), whose course
coincides with that of the eight locomotive bands.   These
canals end caecally both at their oral and apical extremities."(Greene.) The whole of this complex canal-system is lined by
a ciliated endoderm, and a constant circulation of the included
nutrient fluids is thus maintained.
Immediately within the apical pole is situated a small cyst
or vesicle, supposed to be an organ of sense, and termed the
k                    b
e  h          e
Fig. 37.-Morphology of Ctenophora. i. Diagrammatic transverse section of Plearobrachia. b Digestive cavity; i i Primary radial canals; k k,,Secondary radial
canals; / 1 Tertiary radial canals; g Tentacle.
2. Longitudinal section ofPleurobrachia. a Mouth; b Digestive cavity; e Funnel; d d Paragastric canals; e e Apical canals; fCtenophoral canal; g Tentacle;
h Ctenocyst. (After Greene.)
" ctenocyst" (h).  In structure the " ctenocyst" consists of a
spherical vesicle, lined with a ciliated epithelium, and filled
with a clear- fluid, which contains mineral particles, probably
of carbonate of lime. Resting upon the ctenocyst is a small
ganglionic mass, giving origin to a number of delicate filaments, and generally admitted to be a rudimentary form of
nervous system.   The reproductive organs of Pleurobrachia
are in the form of folds, containing either ova or spermatozoa,
and situated beneath the endodermal lining of the ctenophoral
canals, one on each side.
The embryo Pleurobrachia is at first rudely cylindrical in
form, a belt of cilia passing round the middle of its body.
This soon breaks up into two lateral groups, which eventually
disappear altogether, "the ctenophores, at first very broad and




CCELENTERATA: ACTINOZOX.                 133
few in number, at an early period taking on the performance
of their special function."-(Greene.)
As regards the homologies between Acdinia and Pleurobrachia,
the following may be quoted from Professor Greene: —
"If now a comparison be made between this nutrient
system" (the canal-system  of the Ctenzophora) "and that of
Actinia, the digestive sacs of the two organisms are clearly
seen to correspond in form, in relative size, and mode of
communication with the somatic cavity.  The funnel and
apical canals of Pleurobrachia, though more distinctly marked
out, are the homologues of those parts of the general cavity,
which in Actinia are central in position, and underlie the free
end of the digestive sac. So also the paragastric and radial
canals may be likened to those lateral portions of the somatic
cavity of Aclinia which are not included between the mesenteries.  Lastly, the ctenophoral canals of Pleurobrachia and the
somatic chambers of Actinia appear to be truly homologous, the
chief difference between the two forms being, that while in the
latter the body-chambers are wide and separated by very thin
partitions, they are in Pleurobrachia reduced to the condition
of tubes; the mesenteries which intervene becoming very
thick and gelatinous, so as to constitute, indeed, the principal
bulk of the body."  The " apical" canals, again, by which the
digestive sac communicates inferiorly with the external medium,
may be compared with the perforation which is found in some
of the Actinide (Ccrianlthus and Peachia) traversing the axis of
the base or foot.
The remaining members of the Ctlenophora conform in most
essential respects with Pleurobrachia, the most important differences being found in the canal-system. For purposes of
comparison this system may be divided into four portions as
follows:-I. The "axial system," consisting of the mouth,
stomach, funnel, and apical canals. 2. The "paraxial system,"
comprising the paragastric canals. 3. The "radial system,"
comprising the primary, secondary, and tertiary radial canals.
4. The " ctenophoral system," consisting of the tubes which run
underneath the locomotive bands.
In Beroe, which is in other respects very similar to Pleurobrachia, the axial system of canals is the same as we have seen
in the latter. The paraxial system, however, consists of zooo
pairs of paragastric canals, which, instead of terminating
cmecally, open into a circular canal which surrounds the mouth.
The ctenophoral canals, likewise, open into the oral vessel,
instead of terminating coecally as in Pleurobrachia. Lastly,
the radial system is not developed, the ctenophoral canals




134               MANUAL OF ZOOLOGY.
simply curving round towards their apical extremities, and
opening into the funnel directly.
Amongst the Beroidce the mouth extends entirely across the
oral extremity of the body; hence they have been termed
Eurystomata, the term  Stenostonzata being applied collectively
to all the other C/enophora.
The Beroidez further, differ from  Plezirobrachia in being
destitute of the long tentacular appendages so characteristic
of the latter.
In Cestum, or " Venus's Girdle," "elongation takes place to
an extraordinary extent, at right angles to the direction of the
digestive track, a flat, ribbon-shaped body, three or four feet in
length, being the result."
DIVISIONS OF THE CTENOPHORA.-The following arrangement of the Ctenophora has been adopted by Gegenbaur (see
Greene):Order CTENOPHORA.
Sub-order I. Stenosto7nata.
Family I. CALLYMMIDAM.
Body furnished with a pair of antero-posterior oral lobes, and other
smaller lateral appendages.  Tentacles various, turned towards the
mouth.
Family II. CESTIDAI.
Body ribbon-shaped, extended in a lateral direction,,without oral
lobes. Tentacles two in number, antero-posterior, turned towards the
mouth.
Family III. CALLIANIRIDIE.
Body produced into a pair of wing-like lateral lobes, bearing the ctenophores. Tentacles two in number, lateral, turned from the mouth.
Family IV. PLEUROBRACHIADAE.
Body oval or spheroidal, without oral lobes.  Tentacles two in
number, lateral, turned from the mouth.
Sub-order II. Eurystomata.
Family V. BEROIDE.
Body oval, elongated, without oral lobes. Tentacles absent.
CHAPTER XVII.
DISTRIBUTION OF A CTINOZOA.
I. DISTRIBUTION OF ACTINOZOA IN SPACE.  2. CORAL REEFS.
3. DISTRIBUTION OF ACTINOZOA IN TIME. 4. APPENDIX.
DISTRIBUTION OF ACTINOZOA IN SPACE.-The Zoantharia malacodermata appear to have an almost cosmopolitan range, sea



C(E LENTERATA: ACTiNOZOA.               135
anemones being found on almost every coast; some of the
tropical forms attaining a very large size.  The Ctenophora,
too, have an almost world-wide distribution, occurring in all
seas from the equator to within the arctic circle. In habit all
the Ctenophora are pelagic, being found, like the oceanic Hydrozoa, swimming near the surface far from land. Pennatulid&e
and Gorgonidce are found in the seas of the temperate zone,
but the latter attain their maximum within the tropics. The
Red Coral of commerce (Corallium rubrum) is derived from
the Mediterranean.
The so-called "reef-building" Corals have their distribution
conditioned by the mean winter temperature of the sea, a temperature of not less than 66~ being necessary for their existence.
The seas, therefore, which possess the necessary temperature
may be said to be all comprised within a distance of about
i800 miles of the equator on each side. Within these limits,
however, apparently owing to the influence of Arctic currents,
no coral-reefs are found on the western coasts of America and
Africa. They are found chiefly on the east coast of Africa,
the shores of Madagascar, the Red Sea and Persian Gulf,
throughout the Indian Ocean and the whole of Polynesia, and
around the West Indian Islands and the coast of Florida.
All known Actinozoa are marine, no member of the class
having hitherto been found in fresh water.
CORAL-REEFS.-A " coral-reef" is a mass of coral, sometimes
many hundred miles in length, and it may be two thousand
feet or more in thickness, produced by the combined growth
of different species of coralligenous Actinozoa. As before said,
a mean winter temperature of not less than 66~ is necessary
for their existence, and, therefore, nothing worthy of the name
of a "coral-reef" is to be found in seas so far removed from
the equator as to possess a lower winter temperature than
the above.  The headquarters of the reef-building Corals
may be said to be around the islands and continents of the
Pacific Ocean. According to Darwin, coral-reefs may be
divided into three principal forms-viz., Fringing-reefs, Barrierreefs; and Atolls, distinguished by the following characters:I. Fringing-reefs (fig. 38, i).-These are reefs, seldom of
great size, which may either surround islands, or skirt the
shores of continents. These shore-reefs have no channel of
any great depth intervening between them and the land, and
the soundings on their seaward margin indicate that they repose
upon a gently-sloping surface.
2. Barrier-reefs (fig. 38, 2).-These, like the preceding, may
either encircle islands, or may skirt continents. They are dis.




136                MANUAL OF ZOOLOGY.
tinguished from fringing-reefs by the fact that they occur usually
at a much, greater distance from land, that there intervenes a
channel of deep water between them and the shore, and that
soundings taken close to their seaward margin indicate enormous depths. If the barrier-reef surround an island, it is sometimes called an " encircling barrier-reef," and it constitutes with
its island what is called a "lagoon-island."
As an example of this class of reefs may be taken the great
barrier-reef on the N.E. coast of Australia, the structure of
which is on a perfectly colossal scale. This reef runs, with a
few breaches in its continuity, for a distance of more than a
a     b   d                        a1          a
C                        C
b             d      b      a
a                           --
b               d          b      a
3
Fig. 38.-Structure of coral-rtces. ~ iFrinoir -reef; 2 Barrier-reef; 3 Atoll. a Sea
level; b Coral-reef; c Prril:itlvt lani; d Portion of sea within the reef, forming a
channel or lagoon.
thousand miles, its average distance from  the shore being between twenty and thirty miles, and the depth of the inner
channel being from ten to sixty fathoms, whilst the sea outside
is "profoundly deep " (in some places over  800oo feet).
3. Atoals (fig. 38, 3).-These are nearly circular reefs of
coral, en-closing a central expanse of water or lagoon.  They
seldom form complete rings, the reef being usually breached
by one or more openings, which are always situated on the leeward side, or on that side which is most completely sheltered
from the prevailing winds. In their structure they are identical with "encircling barrier-reefs," and differ from these only




CCELENTERATA: ACTINOZOA.               137
in the fact that the lagoon which they enclose does not contain
an island in its centre.
If a coral-reef be observed-say a portion of an encircling
barrier-reef —the following are the general phenomena which
may be noticed.  The general shape of the reef is triangular,
presenting a steep and abrupt wall on the seaward side, and
having a long and gentle slope towards the land. The outer
margin of the reef is exposed to the beating of a tremendous
surf, whilst the soundings taken just outside the line of breakers always indicate great depths. The longer inner slope is
washed by the calm waters of the inner lagoon or channel.
The reef is only very partially composed of living corals, which
are found to occupy a mere strip, or zone, along the seaward
margin of the reef, whilst all above this, as well as all below, is
constituted by dead coral, or " coral-rock."
As to the method in which such a reef is produced, the following facts have been established:
A. The coral-producing polypes cannot exist at levels higher
than extreme low water, exposure to the sun, even for a short
period, proving rapidly fatal. It follows from this that no coralreef can be raised above the level of the sea by the efforts of
its builders. The agency whereby reefs are raised above the
surface of the sea, is the denuding power of the breakers which
constantly fall upon their outer margins. These detach large
masses of dead coral, and heap them up in particular places,
until an island is gradually produced. The fragments thus
accumulated are compacted together by the finer detritus of
the reef, and are cemented together by the percolation of water
holding carbonate of lime in solution. In this way the upper
surface of the reef, along a line of greater'or less breadth, is
more or less completely raised above the level of high water.
It is obvious, however, that the reef might be entirely destroyed by a continuation of this process-the sea being quite
competent to undo what it had done-unless some counteracting force were brought into play. This counteracting force is
found in the vital activity of the living corals which form the
seaward margin of the reef, and which, by their growth, prevent
the sea from always destroying the masses of sediment which
it may have thrown up.
B. The coral-producing polypes cannot exist at depths exceeding some 15 to 30 fathoms. It follows from this that no
coral-reef can be commenced upon a sea-bottom deeper than
about 30 fathoms. The question now arises-In what way
have reefs been produced, which, as we have seen, rise out of
depths of 300 fathoms or more? This question has been an



138             MANUAL OF ZOOLOGY.
swered by Darwin, who showed that the production of barrierreefs and atolls was really to be ascribed to a gradual subsidence of the foundations upon which they rest. Thus, if a
fringing-reef which surrounds an island is supposed gradually
to sink beneath the sea, the upward growth of the corals will
neutralise the downward movement of the land, so far, at any
rate, that the reef will appear to be stationary, whilst it is
really growing upwards. The island, however, as subsidence
goes on, will gradually diminish in size, and a channel will be
formed between it and the reef. If the depression should be
still continued, the island will be reduced to a mere peak in
the centre of a lagoon; and the reef, from a "fringing-reef,"
will have become converted into an " encircling barrier-reef."
As the growth of the reef is chiefly vertical, the continued depression will, of course, have produced deep water all round
the reef.  If the subsidence be continued still further, the central peak will disappear altogether, and the reef will become a
more or less complete ring surrounding a central expanse of
water; thus becoming converted into an "atoll."  The production, therefore, of encircling barrier-reefs and atolls is thus
seen to be due to a process of subsidence of the sea-bottom.
The existence, however, of fringing-reefs is only possible when
the land is either slowly rising, or is stationary; and as a matter of fact, fringing-reefs are often found to be conjoined with
upraised strata of post-tertiary age. Atolls and encircling barrier-reefs, on the other hand, are not found in the vicinity of
active volcanoes-regions where geology teaches us that the
land is either stationary or is undergoing slow upheaval.
C. Different portions of a coral reef are occupied by different kinds of corals: According to Agassiz, the basement of a
coral-reef is formed by a zone of massive Astrzans. These cannot flourish at depths of less than six fathoms of water, and
consequently when the surface of the reef has reached this
level, the Astrwans cease to grow. Their place is now taken
by Meandrinas (Brain-corals) and Porites; but these, too, cannot extend above a certain level. Finally, the summit- of the
reef is formed by an aggregation of less massive corals, such as
7adreporidez, AMilleporidw, and GorgonidZe.
DISTRIBUTION OF ACTINOZOA IN TIME.-With the single exception of the Mollusca, no division of the animal kingdom
contributes such important and numerous indications of its
past existence as the Actinozoa.
In the Palaeozoic Rocks the majority of corals belong to
the division Rugosa, these seeming to have filled the place now
taken by the sclerodermic Zoantharia.  The order Rugosa is




CCELENTERATA: ACTINOZOA.                     I39
entirely Palkeozoic, with the single exception of the genus Holocystis which is represented in the Secondary Rocks by a single
species (viz., H. elegans, from  the lower Greensand) and a few
Tertiary forms.  In the lower Paleozoic Rocks the Rugosa
are especially abundant; but in the Permian formation the
order is represented by the single genus Polycalia.
The Zoan/haria Sclerodermata, though attaining their maximum at the present day, nevertheless are well represented
in past time, beginning in the Silurian period. One subdivision of this group, the Thbulosa, is entirely confined to the
Paleozoic Rocks, and another, the Zabulata, is chiefly Paleozoic.  The Perforata and Aporosa, on the other hand, are more
abundant in the Mesozoic and Kainozoic Epochs.
The Zoantharia Sclerobasica are hardly known as fossils, but
the Miocene deposits of Piedmont (Middle Tertiary) have
yielded a species of Amntipathes.
The Zoantharia Malacodermata, from the soft nature of their
bodies, are obviously incapable of leaving any traces of their
existence; though we are by no means therefore justified in
asserting that they did not exist in past geological epochs.
The Alcyonaria are very doubtfully represented in rocks
older than the Chalk; the Lower Silurian fossil called Protovirgularia being more probably referable to the Hydrozoa.
One of the Pennatuidxe (viz., Graphkularia) has been found in
the London Clay (Eocene), and the same formation has likewise yielded two species of Gorgonida (.Miopsea and Websteria).
The genus Corallium has likewise been found in deposits of
Miocene age.
The Ctenophora, being entirely destitute of any hard structures,
are not known at all as occurring in the fossil condition.
APPENDIX GIVING A TABULAR VIEW OF THE DIVISIONS OF TlIE
ZOANTHARIA SCLERODERMATA AND RUGOSA (AFTER
MILNE-EDWARDS AND JULES HAIME).
A. The Zoantharia Scierodermata are defined by the possession of a
sclerodermic corallum, the parts of which are arranged in multiples of five
or six. Septa generally well developed, but not combined, as a rule; with
tabulke.
The following chief divisions of the Zoantharia Sclerodermala are, with
few alterations, those adopted by the above-mentioned authorities:I. TABULATA.-Septa rudimentary or absent; tabula well developed,
dividing the visceral chamber into a series of stories.
I. Thecidae.-Corallum massive; a dense spurious ccenenchyma formed
by the lateral union of the septa; tabulae numerous.
2. Favositide.-Septa and corallites distinct; little or no true coenenchyma.




140                MANUAL OF ZOOLOGY.
3. Seriatoporidc. —Corallum arborescent; sclerenchyma abundant and
compact; tabule few.
4. Mi/lleporidee.-Corallum massive or foliaceous; septa not numerous;
sclerenchyma tabular or cellular.
1I. PERFOPATA.-Septa well developed; no tabul;e  dissepiments rudimentary; sclerenchyma porous.
5. Eupsammido.-Coralllum simple or composite; septa well developed
and lamellar; columella spongiose.
6. Poritid&. —Corallum composed of spongy, reticulated sclerenchyma.
Septa never lamellar, but consisting wholly of a more or less definite
series of trabecule; no tabule.
7. Madreporidae.-Corallum usually composite; ccenenchyma abundant
and spongy; thecoe porous, not distinct from the ccenenchyma;
septa distinct, but slightly perforate.
III. APOROSA.-Septa well developed, completely lamellar, and primitively
consisting of six elements; no tabule; sclerenchyma imperforate.
8. Fungidz. —Corallum simple or compound; thecme ill developed, and
somewhat porous; no dissepiments or tabula; synapticule numerous.
9. Astrzidte.-Corallum simple or compound; no proper ccneinchyma;
numerous dissepiments; no synapticukl.  Corallites well defined,
and separated from one another by perfect walls.
io. Oculinide.-Corallum composite; ccenenchyma abundant and compact; dissepiments few in number.  Walls of the corallites without
perforations, not distinct from the ccenenchyma.
I I. Turbinolidce. — Corallum usually simple; no coenenchyma; septa well
developed; no dissepiments, nor synapticulxe.
IV. TUBULOSA.- Septa indicated by mere strike; thecae pyriform; corallites
sometimes connected by a creeping basal coenenchyma.
12. Aulaopori&e.-This being the only family in the Tubulosa, its characters are necessarily the same as those of the division itself.
B. ORDER RUGOSA.-Characterised by the possession of a sclerodermic
corallum, usually with septa and tabulhe combined, the former being in
multiples of four.  The corallites are always distinct, and are never united
together by a ccenenchyma. The septa are usually incomplete, but are
never porous, and never bear synapticule.  The order is divided into the
following four families:Family I. Staurida&.
Corallum simple or composite; septa incomplete, united by lamellar
dissepiments; four large primary septa, forming a cross.
Family 2. Cyathaxonidz&e.
Corallum simple; septa complete; no dissepiments or tabula; without four primary septa.
Family 3. CyathophAyllidae.
Corallum simple or composite; septa incomplete; tabulke generally
present.
Family 4. CystijphyZlidae.
Corallum simple, composed chiefly of a vesicular mass, with but
slight traces of septa.




A VN UL O IDA.
CHAPTER XVIII.
I. GENERAL CHARACTERS OF THE ANNULOIDA. 2. GENERAL
CHARACTERS OF TIlE ECHINODERMATA.
SUB-KINGDOM III. ANNULOIDA ( = Echinozoa, Allman).-This
sub-kingdom was proposed by Professor Huxley for the reception of the two groups of the Echinodermata and the Scolecida,
of which the former belonged to the old sub-kingdom Radiata,
whilst the latter was formerly classed with the Annulosa. The
same sections have been grouped by Professor Allman together,
under the name Echinozoa; the Ro/zfera, however, being excluded from this division and classed with the Annulzosa. By
others again, the Annuloida are looked upon as a section of the
Annulosa, and not as a distinct sub-kingdom.  Provisionally,
however, it seems best to regard the Annuloida as one of the
primary divisions of the animal kingdom, it being impossible,
in the meanwhile, to frame a definition common to it and to
the Annulosa. The name Vermes has sometimes been employed to designate the sub-kingdom Annuloida, certain classes
being sometimes removed elsewhere, or certain others being
added.  In its most modem  signification, the term  Vermes
may be held as synonymous with Annuloida, minus the Echino~dermata and plus the whole of the Anarthropodous division of
the Annulosa.
The Annuloida are distinguished by the presence of a distinct
nervous system, and the possession of an alimentary canal which is
entirely Jhut offfrom the general cavity of the body. A peculiar
system of canals, usually communicating with the exterior, and
termed the" water-vascular" or " aquiferous " system, is present
in all; and a true vascular apparatus is sometimes present. Iiz
none is the body of the adult coipnosed of definite segments, or
provided with  " bilaterally disposed successive pairs of appendages."
The union of the Echinodermata with the Scolecida in a single
sub-kingdom, as proposed by Huxley, must be regarded as a




142             MANUAL OF ZOOLOGY.
purely provisional arrangement. Many other classifications
have been proposed, each with some obvious advantages and
some disadvantages. Perhaps the most natural arrangement
would be to establish a separate sub-kingdom for the Echinodermata, and to group the Sco/ecida with the Anartlhropoda under
the name of Vermes. In the confessedly imperfect state of our
knowledge, however, it will be as well to retain for the present
the sub-kingdom Annuloida.
The Annuloida are divided into two great classes, the Echinodermzata and the Scolecida.
CLASS I.- ECHINODERMATA.
The members of this class are known commonly as Seaurchins, Star-fishes, Brittle-stars, Feather-stars, Sea-cucumbers,
&c., and the following are their leading characteristics. They
are all animals which, in the adult condition, show a more or
less distinctly radiate condition of their parts, especially of those
around the mouth; whilst in their embryonic stages they are
more or less distinctly bilaterally symmetrical. Whilst radial
symmetry in the great majority of cases preponderates in the
adult Echinoderm, there are, nevertheless, many instances in
which the fully-grown animal shows distinct traces of bilateral
symmetry. The external- envelope of the body (" perisome ")
is either composed of numerous calcareous plates, articulated
together, or of a coriaceous integument, in which calcareous
granules and spicules are usually developed.  In all adult
Echinoderms there is a system of tubes, termed the "ambulacral system," which generally subserves locomotion, and
usually communicates with the exterior. This water-vascular
system surrounds the commencement of the alimentary canal,
and in almost all cases gives off secondary vessels in a radiating
manner. An alimentary canal is always present, and is completely shut off from the body-cavity. In many, if not in all,
both neural and haemal systems are developed. The nervous
system in all the adult Echinoderms is a ring-like gangliated
cord, which surrounds the oesophagus and sends branches
parallel to the radiating ambulacral canals.
The special features of the structure of the Echinodermata
will be noticed under each order, but it will be as well to give
here an abstract of Professor Huxley's description of the process of development in the members of the class. In the great
majority, if not in all, of the Echinodermata the impregnated
ovum is developed into a free-swimming, ciliated, ovoid embryo.
Soon the cilia become restricted to one, two, or more bands,




ANNULOIDA: ECHINODERMATA.                 I43
which are generally disposed transversely to the long axis of
the body, and are in all cases bilaterally symmetrical. The
parts of the body which support the cilia are usually developed
into protuberances, or processes, which are symmetrically disposed upon the two sides of the body. "The larvae of Asteridea
and Holothurideat are devoid of any continuous skeleton, but
those of Ophiuritdea and Echinidea possess a very remarkable,
bilaterally symmetrical, continuous, calcareous skeleton, which
extends into and supports the processes of the body." In this
stage the larva form of the two orders last mentioned was
described by Muller as a distinct animal under the name of
Pluteus, from its resemblance to a painter's easel.  (See fig.
4I, I.)
An alimentary canal soon appears in the larva, forming a
curve with an open angle towards the ventral surface of the
organism. The parts of the alimentary canal consist of a mouth,
gullet, globular stomach, and short intestine, with a distinct
anal aperture; the whole being "disposed in a longitudinal
and vertical plane, dividing the larval body into two symmetrical halves.'" Besides the digestive canal, no other organs
have hitherto been discovered in these larvae. In the further
process of development, "an involution of the integument
takes place upon one side of the dorsal region of the body,
so as to give rise to a caecal tube, which gradually elongates
inwards, and eventually reaches a mass of formative matter,
or blastema, aggregated upon one side of the stomach.
Within this, the end of the tube becomes converted into a
circular vessel, from which trunks pass off, radially, through
the enlarging blastema.  The latter, gradually expanding,
gives rise, in the Echinidea, the Asteridea. the Opfhiuridea, and
the Crinoidea, to the body-wall of the adult; the larval body
and skeleton (when the latter exists), with more or less of the
primitive intestine, being either cast off as a whole, or disappearing, or becoming incorporated with the secondary
development, while a new mouth is developed in the centre of
the ring formed by the circular vessel. The vessels which
radiate from the latter give off diverticula to communicate
with the cavities of numerous processes of the body-the socalled feet-which are the chief locomotive organs of the
adult.  The radiating and circular vessels, with all their
appendages, constitute what is known as the'ambulacral
system'; and in Asterids and Echinids this remarkable system
of vessels remains in communication with the exterior of the
body by canals, connected with perforated portions of the
external skeleton - the so7called'mrradreporic canals' and




144             MANUAL OF ZOOLOGY.'tubercles.' In Op/ilurids the persistence of any such communication of the ambulacral system with the exterior is
doubtful, and still more so in Crinoids. In Ho/otZurids no
such communication obtains; the madreporic canals and their
tubercles depending freely from the circular canal into the
perivisceral cavity."
By Professor Wyville Thomson the larva of the Ec/inodermata is termed the " pseud-embryo," since it leads a perfectly
independent existence, and the true Ec/inioderm  is usually
developed out of a portion only of its substance. The great
peculiarity, therefore, in the development of the Echzinodernzata
is found in the possession by the larva of provisional organs,
which may be either absorbed or cast off, but which are not
converted into the corresponding structures of the adult. Thus
the Plu/eus of an Echinoid possesses a mouth and alimentary
canal which are not converted into, and in no way correspond
with, the mouth and alimentary canal of the adult.
The Echinodermata are divided into seven orders —viz., the
Crinoidea, Cystoidea, Blastoidea, Ophiuroidea, Asteroidea, Echinoidea, and Hoiothuroidea. Of these, the first is almost extinct
and the two next are entirely so; they are really the lowest
orders; but their structure will be better understood if the
higher orders are considered first.
CHAPTER. XIX.
ECHINOIDEA.
ORDER ECHINOIDEA.-The members of this order-commonly
known as Sea-urchins-are characterised by the possession of
a subglobose, discoidal, or depressed body, encased in a "test "
or shell, which is composed of numerous, immovably connected,
calcareous plates. The intestine is convoluted, and there is
a distinct anus. The mouth is usually armed with calcareous
teeth, and is always situated on the inferior surface of the body,
but the position of the anal aperture varies.  The larva is
pluteiform, and has a skeleton.
The " test " of the Echinoidea is composed of numerous calcareous plates, firmly united to one another by their edges,
and bearing different names according to their position and
function. In one or two exceptional cases, though the essential structure of the shell is the same as in the ordinary forms,




ANNULOIDA: ECHINODERMATA.                         145
the plates of the test are so thin, and are so united together,
that the entire test becomes flexible and soft. In all recent
members of the order the test is composed of twenty rows of
these plates, arranged in ten  alternating  zones, which  pass
from the one pole of the animal to the other, each zone being
composed of two similar rows. Five of these double rows are
composed of large plates, which are not perforated by any
apertures (fig. 39); the zones formed by these imperforate
plates being termed the " inter-ambulacral areas." The other
five double rows of plates alternate regularly with the former,
and are termed the "ambulacral areas," or "poriferous zones."
b:f
C                              4
e
Fig. 39.-Morphology of Echinoidea. x. Portion of the test of Galerites hemist5heris
enlarged, showing an inter-ambulaoral area (a), and an ambulacral area (b). 2
Galentes hemisjhericus viewed from above. a Inter-ambulacra; b Ambulacra. 3.
Genital and ocular disc of Hemicidarns intermedia enlarged. c Ocular plate; d
Genital plate; e Anal aperture; f Madreporiform tubercle. 4. Spine of the same.
(After Forbes.) The tubercles are mostly omitted on figs. 2 and 3 for the sake of
clearness.
Each of these zones is composed of two rows of small plates,
which are perforated by minute apertures for the emission of
the "ambulacral tubes," or "tube-feet."  Growth of the test is
carried on by additions made to the edge of each individual
plate, by means of an organised membrane which passes be.
tween the sutures, where the plates come into contact with one
another. The plates of the test are studded with large tubercles, which are more numerous on the inter-ambulacral areas
than on the ambulacral, and are wanting on all the plates
which do not belong to either area.   These tubercles carry
spines (fig. 4o), used defensively and in locomotion, which are
articulated to their apices by means of a sort of "universal"




146             MANUAL OF ZOOLOGY.
or " ball-and-socket" joint.  Occasionally a small ligamentous
band passes between the head of the tubercle and the centre
of the concave articular surface of the spine, thus closely resembling the " round ligament" of the hip-joint of man. Besides the main rows of plates just described, forming the socalled " corona," other calcareous pieces go to make up the
test of an Echinus. The mouth is surrounded by a coriaceous
peristomial membrane, which contains a series of small calcareous pieces, known as the "oral plates"; whilst a corresponding series of "anal plates" is found in the membrane
surrounding the opposite termination of the alimentary canal.
Surrounding the aperture of the anus at the summit of the test
is the "apical disc," composed of the so-called genital and
Fig. 4o.-Cidaris aiaUi/[ala. (After Gosse.)
ocular plates (fig. 39, 3). The "genital plates" are five large
plates of a pentagonal form, oach of which is perforated by the
duct of an ovary or testis. One of the genital plates is larger
than the others, and supports a spongy tubercle, perforated by
many minute apertures, like the rose of a watering-pot, and
termed the "madreporiform  tubercle."  The genital plates
occupy the summits of the interambulacral areas.  Wedged
in between the genital plates, and occupying the summits of
the ambulacral areas, are five smaller, heart-shaped, or pentagonal plates, known as the "ocular plates," each being perforated by a pore for the reception of an " ocellus " or " eye."
Besides the spines, which are sometimes of a very great
length, the test often bears curious little appendages, called
"pedicellarife," and often supposed to be parasitic. Each of




ANNULOIDA: ECIIINODERMATA.                147
these consists of a stem, bearing two or three blades or claws,
which snap together and close upon foreign objects, like the
beak of a bird. Their action appears to be independent of
the will of the animal, and their true function is not known;
but they may be regarded as peculiarly modified spines.
Locomotion in the Ec/zizoidea is effected by means of a
singular system of contractile and retractile tubes, which constitute the "ambulacral tubes," or "tube-feet," and are connected with the "ambulacral system " of aquiferous canals (fig.
4I). From the perforated "madreporiform  tubercle" on the
largest of the genital plates, there proceeds a membranous
canal, known as the " stone," or "sand canal," whereby water is
conveyed from the exterior to a circular tube, surrounding the
oesophagus, and constituting the centre of the water-vascular
or ambulacral system.  The function of the madreporiform
tubercle appears to be that of permitting the ingress of water
from the exterior, but of excluding any solid particles, which
might be injurious. The "circular canal," surrounding the
gullet, is situated between the nervous and blood-vascular
rings, and gives off five branches-the "radiating canals "which proceed radially along the "ambulacral areas" in the
interior of the shell. In this course they give off numerous
short lateral tubes-the  "tube-feet "-which pass through
the " ambulacral pores" to gain the exterior of the test,
and terminate in suctorial discs. Besides the radiating ambulacral canals, there are connected with the circular canal
certain vesicles of unknown function, known as the " Polian
vesicles " (ampuilce Polianac). The ambulacral tubes, or tubefeet, can be protruded at the will of the animal through the
pores which perforate the ambulacral areas, and can be
again retracted. By means of these locomotion is effected,
the tube-feet being capable of protrusion to a length greater
than that of the longest spines of the body. The mechanism
by which the tube-feet are protruded and retracted is as follows:-Each tube-foot, shortly after its origin, gives rise to a
secondary lateral branch, which terminates in a vesicle.  These
vesicles or "ampullae" are provided with circular muscular
fibres, by the contraction of which their contained fluid is forced
into the tube-feet, which are thus protruded. Retraction of the
ambulacral tubes is effected by proper muscular fibres of their
own, which expel again the fluid which has been forced into
them by the vesicles. According to Owen, the terminal sucker
ii: each tube-foot of the Echizus is " supported by a circle
of five, or sometimes four, reticulate calcareous plates, which
intercept a central foramen, and by a single, delicate, reticu8




148                  MANUAL OF ZOOLOGY.
lated, perforate plate on the proximal side of the preceding
group. The centre of the suctorial disc is perforated by an
aperture conducting to the interior of the ambulacral tubefoot." This perforation of the suctorial discs of the ambulacra,
though affirmed by Valentin, is denied by Muller; and it is
difficult to believe that it would not impair the functions of
the feet in the act of protrusion.
The digestive system of the Echinus consists of a mouth,
armed with five long, calcareous, rod-like teeth, which perforate five triangular pyramids, the whole forming a singular
structure, known as "Aristotle's Lantern." The mouth conducts by a pharynx and a tortuous oesophagus to a stomach,
11k
Fig. 4I.-Morphology of Echinoidea. I. Echinid larva. a Mouth; b Stomach; c
Intestine; s Skeleton.
2. Diagram of Echinus. The spines and the ambulacra are represented over a
small portion of the test; the vascular system is cross-shaded; the nervous system
is represented by the black line. a Antis; b Stomach; c Mouth; d andf Vascular
rings round the alimentary canal; e Heart; g Test; h Nervous ring round the
gullet; i Ambulacral ring or " circular canal" round the gullet; kk Polian vesicles;
I Sand canal; nm mn Radiating ambulacral canal; n Secondary ambulacral vesicles;
o Ambulacral tubes, or "tube-feet"; pj Spines; r Madreporiform tubercle.
opening into a convoluted intestine, which winds round the
interior of the shell, and terminates in a distinct anus. The
mouth is always situated at the base of the test, and may be
central, sub-central, or altogether excentric in position. The
anus varies considerably in its position, being usually situated
within the apical disc, and surrounded by the genital and
ocular plates, when the test is said to be " regular." Sometimes, however, the anal aperture is without the apical disc,
and is removed to some distance from  the genital plates, when
the test is said to be "irregular." The convolutions of the
alimentary canal are attached to the interior of the test by a
delicate mesentery; the surface of which, as well as that of the




ANNULOIDA: ECHINODERMATA.                149
lining-membrane of the shell, is richly ciliated, and subserves
the purposes of respiration.
The proper blood-vascular system (fig. 41, 2) consists of a:
central, fusiform, contractile vesicle, or heart. This gives off
one vessel, which forms a ring round the intestine near the
anus, and another which passes downwards, and forms a circle
round the gullet, above the "circular canal" of the ambulacral
system. From the anal vessel proceed five arterial branches,
which run along the ambulacral spaces, and return their blood
by five branches, which run alongside of them in an opposite
direction. This blood-vascular system has been thought to be
homologous with the pseudohmmal system of the Annelida,
rather than with the true circulatory system of higher animals.
By Huxley, however, the pseudohaemal vessels of the Annelides are looked upon as homologous with the water-vascular
system  of the Scolecida, to which the water-vascular or ambulacral system of the Echinoderms is unquestionably comparable.  The hamal system, therefore, of the Echinoderms
must be regarded as something not represented amongst the
Annelides.
The nervous system consists of a ganglionated circular cord,
which surrounds the gullet below, or superficial to, the "circular
canal" of the ambulacral system, and which sends five branches
along the ambulacral spaces, in company with the radiating
ambulacral canals.
There is no distinct respiratory organ, but the function of
aeration of the blood appears to be performed partly by the
vascular lining of the test and the mesentery, and partly by the
secondary ambulacral vesicles. The perivisceral cavity is filled
with sea-water, but the mode in which this is admitted, or
renovated, is not known with certainty. According to Tiedemann, the water gains access to the interior by means of short,
branched processes, which are attached to the extremities of
the inter-ambulacral areas round the mouth; but others deny
that these are perforated by any apertures. These processes
are apparently nothing more than greatly-developed tube-feet,
and they are probably homologous with the crown of feathery
tentacles surrounding the mouth in the Holothurians; though
this is perhaps represented by some very large tube-feet placed
just round the mouth.
The sexes are distinct in all the Echinoidea, and the reproductive organs are in the form of five membranous sacs,
which occupy the inter-ambulacral areas, and open on the
exterior by means of the apertures in the genital plates. In
the "irregular" Echinoids (such as the "heart-urchins ") there




150               MANUAL OF ZOOLOGY.
are only four genital glands, and, therefore, only four genital
plates in the apical disc.
The Echzinoidea may be divided into the following principal
families:SYNOPSIS OF THE FAMILIES OF ECHINOIDEA (AFTER POMEL).
SUB-ORDER I. ECHINIDA. —Test composed of no more than twenty rows
of plates.
a. SsJatiformes.-Mouth excentric, in front; anus behind; anterior ambulacrum obliterated; form obovate. (The so-called "Spantangoid" Sea-urchins.)
I. Ananchvtida. —With simple ambulacra.
2. Spantangida..-With petaloid ambulacra.
b. LZarpadiformes.-Mouth central, or nearly so; toothed or toothless;
anus more or less posterior, but often mounting high enough to
enter into the genital disc; ambulacra similar.
3. Echinonzeida.-Toothless; ambulacra simple.
4. Cassidulida. —Toothless; ambulacra petaloid.
5. Clypeastrida.-Toothed; ambulacra petaloid.
6. Echinocozida. —Toothed; ambulacra simple.
c. Globiformes.-Mouth central; anus opposite the mouth, surrounded
by the genital plates.
7. Cidairida.-Ambulacra prolonged on the buccal membrane and
destitute of buccal branchiae.
8. Echinidev.-Ambulacra not prolonged on the buccal membrane,
but provided with buccal branchire.
SUB-ORDER II. PERISCHOECHINIIT)E OR TESSELATA.-Corona of the test,
consisting of more than twenty rows of plates. (The Palkozoic Seaurchins, Archaeocidaris and Palwchinus.)
CHAPTER XX.
ASTEROIDEA AtND OPHIUROIDEA.
ORDER ASTEROIDEA (Stellerida).-This order comprises the
ordinary star-fishes, and is defined by the following characters:
-The body (fig. 42) is star-shaped or pentagonal, and consists
of a central body or " disc," surrounded by five or more lobes,
or "arms," which radiate from  the body, are hollow, and contain prolongations of the viscera.  The body is not enclosed
in an immovable box, as in the Echinoidea, but the integument
("perisome ") is coriaceous, and is strengthened by irregular
calcareous plates, or studded by calcareous spines. No dental
apparatus is present. The mouth is inferior, and central in
position; the anus either absent or dorsal.   The ambulacral
tube-feet are protruded from grooves on the under surface of




ANNULOIDA: ECHINODERMATA.                 I  I
the rays. The larva is vermiform, and has no pseudembryonic
skeleton.
The skeleton of the Asteroidea is composed of a vast number
of small calcareous plates, or ossicula, united together by the
coriaceous perisome, so as to form a species of chain-armour.
Besides these, the integument is abundantly supplied with
spines, tubercles, and "pedicellariae."  Lastly, the radiating
ambulacral vessels run underneath a species of internal skeleton, occupying the axis of each arm, and composed of a great
number of bilateral " vertebral ossicles" or calcareous plates,
which are movably articulated to one another, and are provided
with special muscles by which they can be brought together or
(Irawn apart.  The upper surface of a star-fish corresponds to
Fig. 42.-Cribella oculala. (After Forbes.)
the combined inter-ambulacral areas of an Echinus, and exhibits the aperture of the anus (when present), and the "madreporiform tubercle," which is situated near the angle between
two rays. The inferior or ventral surface corresponds to the
ambulacral areas of an Echiznus, and exhibits the mouth and
ambulacral grooves.
The mouth is central in position, and is not provided with
teeth; it leads, by a short gullet, into a large stomach, from
which a pair of sacculated diverticula are prolonged into each
ray. A distinct intestine and anus may, or may not, be present; but the anus is sometimes wanting (in the genera, Astr-opecten, Ctenodiscus, and Luidia).
The ambulacral system is essentially the same as in the
Echinoidea, and is connected with the exterior by means of the




152             MANUAL OF ZOOLOGY.
"madreporiform  tubercle," or "nucleus," two, three, or more
of these being occasionally present. The ambulacral tube-feet
are arranged in two or four rows, along grooves in the under
surface of the arms.
The blood-vascular system consists, as in the Ec/hinus, of
two circular vessels, one round the intestine, and one round
the gullet, with a dilated tube, or heart, intervening between
them. There are no distinct respiratory organs, but the surfaces of the viscera are abundantly supplied with cilia, and
doubtless subserve respiration; the sea-water being freely admitted into the general body-cavity by means of numerous
contractile ciliated tubes, which project from the dorsal surface
of the body, and are perforated at their free extremities
(Owen).
The nervous system consists of a gangliated cord, surrounding the mouth, and sending filaments to each of the rays. At
the extremity of each ray is a pigment-spot, corresponding to
one of the ocelli of an Echinus, and, like it, supposed to:- be a
rudimentary organ of vision. The eyes are often surrounded
by circles of movable spines, called " eyelids."
The generative organs are in the form of ramified tubes,
arranged in pairs in each ray, and emitting their products
either into the surrounding medium, by means of efferent ducts
which open round the mouth, or into the general body-cavity,
by dehiscence, the external medium in this latter case being
ultimately reached through the respiratory tubes. In their
development, the Asteroidea show the same general phenomena
as are characteristic of the class; but the larvae are not provided with any continuous endoskeleton. In some Asteroids
the larval forms have been described under the name of Bipzinnarice, and in these, as in the Phdteus of the Echinoids, a large
portion of the larva is cast off as useless. In Bzpinlaria asterigera (Sars) the digestive cavity is a simple sac which sends
no prolongations into the rays, and the mouth is inter-radial,
instead of being placed in the centre of the ambulacral system.
The mouth of the adult is at this stage closed by the soft external skin of the larva.
The general shape of the body varies a good deal in different
members of the order.  In the common star-fish (Uraster rubents) the disc is small, and is furnished with long, finger-like
rays, usually fiye in number. In the Cribelate (fig. 42) the
general shape of the body is very much the same. In the
Solasters the disc is large and well marked, and the rays are
from twelve to fifteen in number, and are narrow and short
(about half the length of the diameter of the body).  In the




ANNULOIDA: ECHINODERMATA.                    I53
Goniasters the body is in the form of a pentagonal disc, flattened
on both sides; the true "disc" and rays being only visible on
the under surface of the body.  In none of the true star-fishes,
however, are the arms ever sharply separated from the disc, as
in the Ojhiuroidea, but they are always an immediate continuation of it.
The order Asteroidea has been divided by Dr Gray as follows:
ORDER ASTEROIDEA.
Section a. Ambulacra with four rows offset.
Family I. Asteriade. Dorsal wart simple.
Section b. Amublacra with two rows offeet.
Family 2. Astropectinide. Back flattish, netted with numerous tubercles, crowned with radiating spines at the tip, called " paxillke. "
Family 3. Pentacerotide. Body supported by roundish or elongated
pieces, covered with a smooth or granular skin, pierced with minute
pores between the tubercles.
Family 4. Asterinidcz. Body discoidal or pyramidal; sharp-edged;
skeleton formed of flattish, imbricate plates; dorsal wart single,
rarely double.
ORDER OPHIUROIDEA.-This order comprises the small but
familiar group of the " Brittle-stars" and " Sand-stars," often
considered as belonging to the Asteroidea, to which they are
nearly allied.  The body in the Ophiuroidea (fig. 43) is discoidal, and is covered with granules, spines, or scales, but
pedicellarime are wanting.  From the body-which contains all
the viscera-proceed long slender arms, which may be simple
or branched, but which do not contain any prolongations from
the stomach, nor have their under surface excavated into ambulacral grooves. The arms, in fact, are not simple prolongations of the body, as in the Asteroidea, but are special appendages, superadded for locomotive and prehensile purposes.
Each arm is enclosed byfour rows of calcareous plates, one on
the dorsal surface, one on the ventral surface, and two lateral.
In the centre of each arm is a chain of quadrate ossicles, forming a central axis, and between this axis and the row of ventral
plates is placed the ambulacral vessel.  Each ossicle of the
central chain is composed of two symmetrical halves, but these
are immovably articulated together, and are not movable upon
one another, as in the Asteroidea.  The mouth is situated in
the centre of the inferior surface of the body, is provided with
a masticatory apparatus, and is surrounded by tentacles. It
opens directly into a sac-like ciliated stomach, which is not
continued into an intestine, the mouth serving as an anal aperture.  The stomach is destitute of lateral diverticula.  The
reproductive' organs are situated near the bases of the arms,




154               MANUAL OF ZOOLOGY.
and open by orifices on the ventral surface of the body or in
the interbrachial areas.
It is very questionable whether the ambulacral system in the
adult Ophiuroidea communicates with the exterior; its place
as a locomotive apparatus being taken by the arms.  The
radial vessels of the ambulacral system  are not provided with
secondary vesicles or " ampullae," as they are in the Echinoidea
and Asteroidea, and the lateral " feet" which they give off have
no terminal suckers.  The madreporiform  tubercle is either
Fig. 43.-Ophiuroidea. a OpAihira tex/tzrala, the common Sand-star;
b 01thioconza neglects, the grey Brittle-star (after Forbes).
placed on the inferior surface of the body or is partially concealed by one of the plates surrounding the mouth.
The larva of the 0)phizuroidea is pluteiform, and is furnished
with a continuous endoskeleton; and in some, as in Ophiolepis squanmala, the echinoderm-body appears within the larva,
when the latter has attained but a very imperfect degree of
development.
In Euryale the body is in the form of a sub-globose disc
with five obtuse angles, and the arms are prehensile.  In As



ANNIJLOIDA: ECHINODERMATA.                 155
terophyton, the Medusa-head star, the arms are divided from
the base, first dichotomously, and then into many branches.
In 0.phiura, the sand-star, the arms serve for reptation (creeping), and are undivided, often exceeding the diameter of the
disc many times in length.
The order Qphiuroidea may be divided into two families, as
follows:Family I. Opjhiuridea.
Genital fissures two or four in number. Arms five, always simple.
SFamily 2. Asteroqphydiae.
Genital fissures ten in number. Arms five, simple or branched.
CHAPTER XXI.
~CRINOIDEA, CYSTOIDEA, AND BLASTOIDEA.
ORDER CRINOIDEA.-The members of this order are Ec/zinodermata, in which the body isfixed, during the whole or a portion
of the existence of the animal, to the sea-bottom by means of at
longer or shorter, jointed, and flexible stalk. The body is distinct, composed of articulated calcareous plates, bursiform,
or cup-shaped, and provided with solid arms, which are primarily from five to ten in number, are independent of the
visceral cavity, and are grooved on their upper surfaces for the
ambulacra.  (The position of the body being reversed, the
upper surface is ventral; whilst the dorsal surface is inferior,
and gives origin to the pedicle.)  The tubular processes,
however, which are given off from the radiating ambulacral
canals of the Crinoideea, unlike those of the _Echinoidea and
Asteroidea, are not used in locomotion, but have probably a
respiratory function. The mouth is central, and looks upwards,
an anal aperture being sometimes present, sometimes absent.'The ovaries are situated beneath the skin in the grooves on the
ventral surfaces of the arms or pinnules, as are also the ambulacral or respiratory tubes.  The arms are furnished with numerous lateral branches or "pinnule."  The embryo is "free
and ciliated, and develops within itself a second larval form,
which becomes fixed by a peduncle."-(Huxley.)
Of those Crinoidea which are permanently fixed to the seabottom by a jointed pedicle, there exist but a few living
forms, of which the best known is the Pentacrinus CaputAfeduse.  In this type of the rcrinoidea-largely represented




156               MANUAL OF ZOOLOGY.
in past geological epochs-the body is composed of a series of
calcareous plates, united together so as to form a cup or
"calyx," the bottom of which is continued into a " column," or
pedicle, composed of a series
of calcareous joints or articulations, whereby the animal
is fixed to some foreign body.
The upper part of the calyx
is roofed over by a series of
calcareous plates, and is perforated by the apertures of
the mouth and anus, the latter being sometimes absent.
In  the recent species  the
mouth is central, and there
is a distinct anus at one
side.   The margin of the
calyx gives origin to the arms,
which are grooved on their
upper (or ventral) surfaces for
the ambulacra.  In the living Crinoids the ambulacral
grooves are continued along
the upper surface of the calyx to the mouth.   In the
Palaeozoic Crinoids there is
only a single opening on the
upper surface of the calyx,
which is sometimes central
and sometimes lateral, and
which serves both as a mouth
and anus. In many cases
this aperture is level with the
surface of the calyx, but in
many species it is placed at
the summit of a long proFig. 44.-Crilloidea: Rhizocriuzs LofJ/en- jecting tube, which is termed
sis, a living Crinoid (after Wyville'lhom- the "proboscis."  The amson), four times the natural size. a Stem.
b Calyx. c c Arms.             bulacral grooves in the Palaeozoic Cryinoids are found on
the ventral surfaces of the arms, as in the living species; but
instead of being continued over the surface of the body to
the mouth, they stop short at the bases of the arms, where they
gain access to the interior of the calyx by a series of special
apertures.-(Billings.)




ANNULOIDA: ECHINODERMATA.                    157
More recently a stalked Crinoid has been discovered in the
Atlantic and North Sea, and has been described under the
name of Rhzizocrinus Lofotensis (fig. 44).  The chief interest of
this form is the fact that it belongs to a group of the Crinoidea
hitherto believed to be exclusively confined to the Mesozoic
Rocks-viz., the Ajpiocrinidc  or " Pear-encrinites."  In fact,
Rhizocrinus is very closely allied to the Cretaceous genus
BouzgoUeticrinus, and it may even be doubted if it is generically
separable from it. The late remarkable researches into the life
of the deeper parts of the ocean have brought to light several
Fig. 45.-Crinoidea. Comatu/a rosacea, the Feather-star; a Free adult;
b Fixed young. (After Forbes.)
new Crinoids, which will doubtless, when fully investigated,
still further fill up the interval between the living and extinct
Crinoiden.
In the second type of the Crinoidea-represented in our seas
by the Comatz/a (fig. 45), or Feather-star-the animal is not
permanently fixed, but is only attached by a stalk when young
(fig. 45, b), in which condition it was described as a distinct
species, under the name of Pentacrinus Eurojpus. In its adult
condition, however, the Comatula is free, and consists of a pentagonal disc, which gives origin to ten slender arms, which are




158              MANUAL OF ZOOLOGY.
fringed with many marginal pinnulxe or "cirri."  The mouth
and anus are on the ventral surface of the disc, which in this
case is again the inferior surface, since the animal creeps
about by means of its pinnated arms. The arms, in fact, of
Comatula appear to be purely locomotive in function, and to be
never employed as prehensile organs. The animal lives upon
very minute organisms, drawn into the mouth by the action of
the cilia lining the alimentary canal. The dorsal cirri, however,
are employed to moor the animal temporarily to solid objects.
The mouth is central in position, and the anus, which in some
species forms a tubular projection, is situated on one side.
Both the arms and the lateral pinnulxe are grooved on their
ventral surfaces for the ambulacral vessels; and the pinnules
also serve for the support' of the reproductive organs.  It is
extremely doubtful if the ambulacral system, in the adult, has
any communication with the exterior. The function, in fact,
of the water-vascular system appears to be wholly respiratory,
locomotion being entirely effected by means of the arms. The
alimentary canal is confined entirely to the disc, and the
stomach sends no diverticula along the arms as it does in the
Asteroidea.  The larva or pseudembryo of Comatula rosacea is
a small ovate organism, with four transverse ciliated bands, a
key-hole-sjhaped mouth, and a small vent and rudimentary intestine, the whole showing no traces of radiation. The young
Crinoid is produced within the pseudembryo, and develops a
fresh mouth, anus, and stomach for itself; the first being
originally oro-anal in function, and being placed in the centre
of the ambulacral system.
Several species of Comatllat are known, and the genus appears to be cosmopolitan in its distribution.  The genus
Ophzicrinus has been formed for species said to possess no
more than five undivided arms.
ORDER CYSToIDEA (Cystidea).-The members of this order
are all extinct,  and are entirely confined to the Palmozoic
period. The body (fig. 46) was more or less spherical, and
was protected by an external skeleton, composed of numerous
polygonal calcareous plates, accurately fitted together, and
enclosing all the viscera of the animal.  The body was in
most cases permanently attached to the sea-bottom by means
of a jointed calcareous "column," or pedicle, but this was
much shorter than in the majority of Crinoids.  Upon the
* Recently Professor Loven has described a singular Australian Echinoderm as being most closely allied to, if not truly referable to, the order
Cjystoidea. He has named this curious form H.yrponomne Sarsi, and believes
it to be nearly related to the Cystidean genus Aq/elacrinites.




ANNULOIDA: ECIIINODERMATA.                159
upper surface of the body were two, sometimes three apertures, the functions of which have been a matter of considerable
controversy. One of these is lateral in position, is defended
by a series of small valvular plates, and is
believed by some to be the mouth, whilst
lby others it is asserted to have been an
ovarian aperture.  The view advocated by
Mr Billings, that this aperture was the
mouth, appears from every point of view
to be most probably correct; or rather it
was oro-anal, as was also the proboscis of
the Palmocrinoids. The second opening
is central in position, and is believed by
Mr Billings to be the "ambulacral orifice,"
as it is always in the centre of the arms
when these are present.  The third aperture is only occasionally present, and Fig,46-Cystidea' Ecitfunction  ofannosthawrziesazuratoiu m,
doubtless discharged the functions of an   a Cystidean from the
Bala Limestone (Lower
anus.                                    Silurian).
In some Cysloidea there were no arms,
properly speaking, but only small pinnulke.  In a second section true arms were present, but these were bent backwards,
and were immovably soldered down to the body.  In one
single species (Comarocystites Puncatzus, Billings) the development has gone further, the arms being free, and provided with
lateral pinnulae, as in the true Crinoids.
Many Cystideans are likewise provided with a system of
pores, or fissures, penetrating the plates of the body, and usually arranged in definite groups. These groups are termed
"pectinated rhombs," but their exact function is doubtful.
By Mr Billings, however, they are believed, and apparently
with good reason, to have admitted water to the body-cavity,
and to have thereby subserved a respiratory function.
ORDER BLASTOIDEA.-The members of this order, like those
of the preceding, are all extinct, and are entirely confined to
the Paleozoic period. The body was fixed to the bottom of
the sea by means of a short jointed pedicle; it was globular
or oval in shape, and composed of solid polygonal calcareous
plates, firmly united together, and arranged in five inter-ambulacral and as many ambulacral areas. (These ambulacral areas
are termed by M'Coy " pseud-ambulacra," upon the belief that
they were not pierced for tube-feet, but that they carried a
double row of little jointed tentacles or arms.) The ambulacral areas are petaloid in shape, having a deep furrow down the
centre, and striated transversely. They converge to the mouth,




I60             MANUAL OF ZOOLOGY.
which is superior and central in position, and is surrounded by
five ovarian apertures.  No arms are present.
The Blastoidea are known more familiarly under the name
of Pentremiles, and they occur most commonly in the Carboniferous Rocks.
CHAPTER XXII.
H O L O THUR OIDEA.
ORDER HOLOTHUROIDEA. — The members of this order are
commonly known by the name of "sea-cucumbers," "trepangs," or " bches-de-mer," and are the most highly organised
of all the Echinodcermata.  The body is elongated and vermiform, or rarely slug-shaped, and is not provided with a distinct
test, but is enclosed in a coriaceous skin, sometimes containing
scattered calcareous granules or spicules. The ambulacral tubefeet, when present, are usually disposed in five rows, which
divide the body into an equal number of longitudinal segments
or lobes.  The mouth is surrounded by a circlet of feathery
tentacles, containing prolongations from the central ring of the
water-vascular system; and an anus is situated at the opposite
extremity of the body. There is a long, convoluted intestine.
A special respiratory, or water-vascular, system is usually developed, in the form of a system of arborescent tubes, which
admit water from the exterior.  The larva is vermiform, and
has no skeleton (fig. 47). Ata certain period of their existence, the young Holothurians are barrel-shaped, with transverse rings of cilia.  They rotate rapidly on their long axis,
and have at this stage been described as a distinct genus
under the name of Auricularia.
In the [folothurice proper, locomotion is chiefly effected by
means of rows of ambulacral tube-feet, or by alternate extension and contraction of the worm-like body; but in the
Synaptidae there are no ambulacra, but only the central circular
canal of the ambulacral system, and the animal moves by
means of anchor-shaped spicula, which are scattered in the
integument. When developed, the ambulacral system consists
of a "circular canal," surrounding the mouth, bearing one or
more " Polian vesicles," and giving off branches to the tentacula; and of five "radiating canals" which run down the
interspaces between the great longitudinal muscles.  These
radiating canals give off the tube-feet and their secondary




ANNULOIDA: ECIItNODERMATA.                 161
vesicles, just as in the Ec/hinus. In the typical forms there
are five rows of tube-feet, but these may be scattered over the
whole body, or may be restricted to the ventral surface.
There is also a "sand-canal," which arises from  the circular
canal, and is terminated by a madreporiform tubercle; but
this, instead of opening on the exterior, hangs down freely in
the perivisceral cavity. The fluid, therefore, with which the
ambulacral system is filled, is derived from the perivisceral
cavity, and not from the exterior, as is usually the case.
The mouth in Holothuria is situated anteriorly, and is surrounded by a beautiful fringe of branched, retractile tentacles
(fig. 47), which arise from a ring of calcareous plates, and into
which are sent prolongations from the circum-oral ring of the
ambulacral system. The mouth opens into a pharynx, which
conducts to a stomach. The intestine is long and convoluted,
and opens into a terminal dilatation, termed the "cloaca,"
which serves both as an anus and as an aperture for the
Fig. 47.-IoloLthuroiid ca  Tlzyone actpal/sa. (After Forbes.)
admission of sea-water to the respiratory tubes.  From  the
cloaca arise two branched and arborescent tubes, the terminations of which are probably cxecal.  These run up towards
the anterior extremity of the body, and together constitute the
so-called "respiratory tree." They are highly contractile, and
they perform the function of respiratory organs, sea-water
being admitted to them from the cloaca. The nervous system
consists of a cord, surrounding the gullet, and giving off five
branches, which run alongside of the radiating anibulacral
canals. The generative organs are in the form of long, ramified, cecal tubes, which open externally by a common aperture, situated near the mouth. There is thus no trace of that
radial symmetry which is observed in the arrangement of the
reproductive organs in the other orders of the Echinodermata.
The vascular system consists of two main vessels-one dorsal,
and the other ventral-connected with a circum-cesophageal
ring.




162               MANUAL OF ZOOLOGY.
The skin in the Holo/turice is highly contractile, and the
body is provided with powerful longitudinal and circular
muscles, in compensation for the absence of any rigid integumentary skeleton. Many of the Sea-cucumbers, in fact, are
endowed with such high contractility that they can eject their
internal organs entirely, if injured or alarmed.
In Synapta there is no aml;ulacral system of tube-feet, nor
respiratory tree.  Locomotion is effected by means of little,
anchor-shaped, calcareous spicules, placed upon little papillae
of the integument. Respiration is effected in the abdominal
cavity, into which the water is admitted by five openings between the tentacles.
The order Holot/zuroitdea may be divided into the following
two families:Family I. Ziolot/Zu-ire.
Body free, cylindrical, with a coriaceous integument containing
scattered calcareous particles. An ambulacral system always, and a
respiratory tree usually, present.
Family II. Synantid&e.
Body free, covered with a coriaceous, sometimes soft, integument,
containing minute, anchor-shaped spicules, by means of which the
animal moves. The ambulacral system rudimentary, not giving rise
to tube-feet, and not connected with locomotion. A respiratory tree
sometimes present, sometimes absent.
CHAPTER XXIII.
DISTRIBUTION OF ECHINODERMzA TA IN SPA CE
ANVD TIME.
DISTRIBUTION OF ECHINODERMATA IN SPACE.-The Crizioidea
are represented by very few forms in recent seas, and these
have a very local distribution. The Comaculfe are the commonest, and species have been found in most seas.  The
Pentacrinus Caj5ut-Medusre is exclusively confined, as far as is
known, to the Caribbean Sea. Rhizocrinus Lofotensis has been
dredged on the coast of Norway, and a form believed to be
the same has been found in the Gulf of Mexico.
The Asteroidea, Op/ziuroidea, and Echinoidea are represented
in almost all seas, whether in tropical or temperate zones,
some occurring very far north.  The Holothuroidea have their
metropolis in the Pacific Ocean, occurring abundantly on the
coral-reefs of the Polynesian Archipelago. One species is col



ANNULOIDA: ECHINODERMATA.                      I63
lected in large numbers, and is exported to China, where it is
regarded as a great delicacy.
DISTRIBUTION  OF ECHINODERMATA  IN  TIME.-Numerous
remains of Echinodermata occur in most sedimentary rocks,
beginning with the base of the Lower Silurian Rocks, and extending up to the recent period. The two orders Cystoidea
and -Bastoidea, which are the most lowly organised of the
entire class, are exclusively Paleozoic; and the Crinoidea are
mostly referable to the same epoch. The more highly organised Asteroidea and Ophiuroidea commenced to be represented
in the Silurian period; but the Echinoidea, with a single exception, have no representative earlier than the Carboniferous
Rocks. The following exhibits the geological distribution of
the different orders of the Echinodermlata in somewhat greater
detail:
I. CRINOIDEA. — The Crinoidea attained their maximum  in
the Paleozoic period, from which time they have gradually
diminished down to the present day. As has already been
described, the Paleozoic Crinoidea differ in some important
particulars from those which succeeded them. The order is
well represented in the Silurian, Devonian, and Carboniferous
Rocks, but especially in the latter; many Carboniferous limestones (crinoidal limestones and entrochal marbles) being
almost entirely made tip of the columns and separate joints of
Crinoids. In the Secondary Rocks Crinoids are still abundant.  In the Trias the beautiful "Stone-lily" (Encrinus liZiiformris) is peculiar to its middle division (Muschelkalk). In
the Jurassic period occur many'species of A5iocrinus (Pearencrinite), Pentacrinus, and Extracrinus.   The Chalk also
abounds in Crinoids, amongst which is a remarkable unattached form (the Tortoise-encrinite or MAfrsuppi/es).
Of the non-pediculate Crinoidea, which are a decided advance upon the stalked forms, there are few traces; but
remains of Comalula have been discovered in the lithographic
slate of Solenhofen (Oolite) and in the Chalk.
2. BLASTOIDEA. —The Blastoidea, or Pentremites, are entirely
* As regards the calyx of the fossil Crinoiodea, the following terms are
employed to designate its different parts. The base of the cup, or calyx,
is termed the "pelvis," and it is made up of five, four, or sometimes three
plates, which are termed the "basals."  To the "basals " succeed two or
three rows of plates, which are termed respectively the " primary radials,"
"secondary radials," and "tertiary radials," according to their distance
from the basals. The axillary radials, which are the furthest removed,
give origin to the arms, and are occasionally called the "scapulae" (for
this reason), whilst the primary and secondary radials are called the
" costae. "




I64             MANUAL OF ZOOLOGY.
Palaeozoic, and attain their maximum in the Carboniferous
Rocks, some beds of which in America are known as the
Pentremite Limestone, from the abundance of these organisms.
They are, however, also found in the Silurian and Devonian
Rocks.
3. CYSTIDEA.-These, like the preceding, are entirely Paleozoic; but they are, as far as is yet known, exclusively confined
to the Upper Cambrian and Silurian Rocks, being especially
characteristic of the horizon of the Bala Limestone.  Forms
supposed to be Cystideans have been described from the Devonian Rocks, but their true nature is doubtful. The oldest
known Echinoderms are two extremely simple Cystideahs
(Trochocystites and Eocystites) which have been discovered in
the primordial zone of North America.
4. ASTEROIDEA.-These have a very long range in time, extending from the Lower Silurian period up to the present day.
In the Silurian Rocks the genera Paleaster, Stenaster, Paicodiscus, and Petraster are among the more important, the greater
number of forms being Upper Silurian.  The next period in
which star-fishes abound is the Oolitic (Mesozoic); the more
important genera being Uraster, Luidia, Astrojecten, P~umaster,
and Goniaster, some of which have survived to the present
day. Many star-fishes occur, also, in the Cretaceous Rocks,
the genera Oreaster, Goniodiscus, and Astrogonium being among
the more noticeable.  In the Tertiary Rocks few star-fishes
are known to occur, but Goniaster and Astropec/en are represented in the London Clay (Eocene).
5. OPHIUROIDEA.-The "brittle-stars " are represented in the
Silurian Rocks by the single genus Protaster.  In the Oolitic,
Cretaceous, and Tertiary Rocks several genera of Ophiuroidea
are known; some being extinct, whilst others (such as OphiodZerma, Ophioiepis, and Ophiocoma) still survive at the present
day.
6. ECHINOIDEA.-This order is represented in the Palkeozoic
Rocks by a single aberrant family; but it is numerously represented in the Mesozoic and Kainozoic periods.
For the Paleozoic Echinoidea the formation.of a separate
sub-order has been proposed by Professor M'Coy under the
name of Perischoechinidie, since they differ in some fundamental points from all the other known members of the
order. The test is composed of more than twenty rows of calcareous plates, divided into five ambulacral and five inter-ambulacral areas.  The five ambulacra are continuous from pole to
pole, and are surmounted dorsally by the ocular plates.  The
five inter-ambulacra are composed, each, of three, five, or




ANNULOIDA: SCOLECIDA.                 165
more rows of plates, and are surmounted dorsally by the ovarian plates.  The two genera Arcwehocidaris and Pahechinius
comprise all the known forms of the family, the former being
entirely confined to the Carboniferous Limestone, whilst the
latter occurs also in the Upper Silurians.
The Secondary and Tertiary Echzinoidea resemble those now
living in being composed of not more than twenty rows of
calcareous plates.  The Oolitic and Cretaceous Rocks are
especially rich in forms belonging to this order, many genera
being peculiar; but the number of forms is too great to permit
of any selection.
7. HOLOTHUROIDEA.-This order, comprising, as it does, softbodied animals, can hardly be said to be known as occurring
in the fossil condition. Some calcareous plates and spicules,
supposed to belong to a Holothurid, have, however, been described as occurring in the Secondary Rocks, and the shield
of Psolus has been found in Post-tertiary deposits in Bute.
CHAPTER XXIV.
SCOLECIDA.
CLASS II. SCOLECIDA.-This class was proposed by Professor
Huxley for the reception of the remaining members of the
Annuloida, comprising the Rolifera, the Turbellaria, the'remnatoda, the Teniada, the Nematoidea, the Acanthocephala, and the
Gordiacea.  Of these the Rotifera stand alone, whilst the Turbellaria, Tremaloda, and Taniada constitute the old division of
the P/alyehnia (Flat Worms), and the Nematoidea, Acawtheocephala, and Gordiacea make up the old NJemaltemia (Round
Worms or Thread-worms). For some purposes these old divisions are sufficiently convenient to be retained, though they
are of little scientific value. The term Entozoa has acquired
such a general currency that it is necessarily employed occasionally, but it has been used in such widely different senses
by different writers, that it would be almost better to discard
it altogether. It certainly cannot be used as synonymous with
Scolecida, many of these not being parasitic at all. It will,
therefore, be employed here, in a restricted sense, to designate
those orders of the Scolecida which are internal parasites,
comprising the So'emaloda, Tazniada, Nemaloidea (in part),
Acanthocephala, and Gordiacea. The Turbellaria and Rotifera,




i66             MANUAL OF ZOOLOGY.
with a section of the emnaloidea, lead a free existence, and are
not parasitic within other animals.
The ScolZeida are defined by the possession of a "watervascular system," consisting of a " remarkable set of vessels
which communicate with the exterior by one or more apertures situated upon the surface of the body, and branch out,
more or less extensively, into its substance."-(Huxley.) No
proper vascular apparatus is present, and the nervous system
(when present) "consists of one or two closely approximated
ganglia."  The habits and mode of life of the different members of the Scolecida are so different, that no other character,
save the above, can be predicated which would be common to
the entire class, and would not be shared by some other allied
division.
DIVISION I. PLATYELMIA.-This section includes those Scoiccida which possess a more or less flattened body, usually somewhat ovate in shape, and not exhibiting anything like distinct
segmentation. The division includes two parasitic orders —
the Tceniada and the Trematloda; and one non-parasitic order
— viz., the Turbellaria. A sub-order, however, of this last, the
Nemertidae, does not conform  to the above definition; but
their other characters are such as to forbid their separation.
ORDER I. TAINIADA (Cestoidea).-This order comprises the
internal parasites, called Tape-worms (Cestoid worms), and
the old order of the "Cystic worms" (Cystica); the latter
being now known to be merely immature forms of the Tapeworms.
In their mature condition, the f/eiada (see fig. 48) are
always found inhabiting the alimentary canal of some warmblooded vertebrate animal; and they are distinguished by
their great length, and by being composed of a number of
flattened joints or articulations. These joints are not, however, an example of true segmentation, nor do they really
constitute the Tape-worm; the true animal being found in
the small, rounded, anterior extremity, the so-called " head," or
" nurse," whilst the joints are simply hermaphrodite, generative
segments, which the " head " throws off by a process of gemmation. The " head " (fig. 48, 3), which constitutes the real Tapeworm, is a minute, rounded body, which is furnished with a
circlet of hooks or suckers, or both, whereby the parasite is
enabled to maintain its hold upon the mucous membrane of
the intestines of its host. No digestive organs of any kind are
present, not even a mouth; and the nutrition of the animal is
entirely effected by imbibition. The nervous system consists
of two small ganglia, which send filaments backwards; but




ANNULOIDA: SCOLECIDA.                  167
there is considerable obscurity on this point, and it has been
asserted that the nervous system is entirely wanting, or that
there is only a single ganglion. The "water-vascular system"
consists of a series of long vessels which run down each side of
the body, communicating with one another at each articulation by means of a transverse vessel, and opening in the last
joint into a contractile vesicle.  It thus appears that all the
joints are organically connected together. Whilst the " head "
constitutes the real animal, it, nevertheless, contains no reproductive organs, and these are developed in the joints or
segments (fig. 48, 4), which are produced from the head
posteriorly by budding. After the first joint, each new segment is intercalated between the head and the segment, or
segments, already formed; so that the joints nearest the head
are those latest formed, and those furthest from the head are
the most mature. Each segment, when mature, contains both
male and female organs of generation, and is, therefore,
sexually perfect. To such a single segment the term "proglottis " is applied, from its resemblance in shape to the tip of
the tongue. The ovary is a branched tube, which occupies
the greater part of the proglottis, and opens, along with the
efferent duct of the male organ, at a common papilla, which
is perforated by an aperture, termed the "generative pore."
The position of this pore varies, being placed in the centre of
one of the lateral margins of the proglottis in the common Tapeworm (Tcenia solium), but being situated upon the flat surface
of the segment in the rarer Bothrioceph/alus latus.  These two
elements-namely, the minute head, with its hooklets and
suckers, and the aggregate of the joints, or proglottidestogether compose what is commonly called a "Tape-worm,"
such as is found in the alimentary canal of man, and of many
animals. The length of this composite organism varies from
a few inches to several yards.
Singular as is the composition of the mature Tape-worm,
still more extraordinary are the phenomena observed in its
development, of which the following is a brief account:" Proglottides," or the sexually mature segments of a Tapeworm, are only produced within the alimentary canal of man,
or of some other warm-blooded vertebrate.  The development
of the ova which are contained in the proglottides, cannot,
however, be carried out in. this situation; hence the compara-tive harmlessness of this parasite, and hence the name of
"solitary worm," which is sometimes applied to it.  For the
production of an embryo, it is necessary that the ovum should
be swallowed by some animal other than the one inhabited by




i 68            MANUAL OF ZOOLOGY.
the mature Tape-worm. If this does not take place, the fecun
dated ovum is absolutely unable to develop itself. To secure
this, however, the dispersion of the ova is provided for by the
expulsion of the ripe proglottides from the bowel, all their
contained ova having been previously fertilised. After their
discharge from the body, the proglottides decompose, and the
ova are liberated (fig. 48, i), when they are found to be
covered by a capsule which protects them from all ordinary
mechanical, and even chemical, agencies, which might prove
injurious to them.  In this stage, the embryo is often so far
developed within the ovum that its head may be recognised
by its possession of three pairs of siliteous hooklets.  For
further development, it is now necessary tihat the ovum be
swallowed by some warm-blooded vertebrate, and should thus
gain access to its alimentary canal.  When this takes place,
the protective capsule or covering of the microscopically minute ovum is ruptured, either mechanically during mastication,
or chemically by the action of the gasnic juice; and the
embryo is thus liberated. The liberated embryo is now called
a "proscolex," and consists of a minute vesicle, which is provided with three pairs of siliceous spines, fitted for boring
through the tissues of its host. Armed with these, the pro
scolex perforates the wall of the stomach, and may either
penetrate some contiguous organ, or may gain access to some
blood-vessel, and be conveyed by the blood to some part of
the body, the liver being the one most likely.
Having by one of these methods reached a suitable restingplace, the proscolex now proceeds to surround itself with a
cyst, and to develop a vesicle, containing fluid, from its posterior extremity, when it is called a "scolex" (fig. 48, 2). In
some of the eenizMa(da the scolices are called " hydatids," and
it is these, also, which constituted the old order of the "Cystic
Worms."  When thus encysted within the tissues of an animal,
the "scolex " consists simply of a taenioid head, with a circlet
of hooklets and four " oscula" or suckers, united by a contracted neck to a vesicular body. It contains no reproductive
organs, or, indeed, organs of any -kind, and cannot attain any
further stage of development, unless it be swallowed and be
taken for the second time into the alimentary canal of a warmblooded vertebrate.  It may increase, and produce fresh
scolices, but this takes place simply by a process of gemmation. In some cases, however, a very partial and limited development does actually take place -in the scolex prior to this
change of abode, but this is an exceptional occurrence. In
these cases the "neck" of the scolex becomes partially seg



ANNULOIDA: SCOLECIDA.                         I69
mented, so that it comes to resemble an imperfectly developed
Tania, and is called  a  " strobila-embryo."   The series of
changes, however, whereby the scolex is converted into the
"strobila," or adult tape-worm, cannot be carried out unless
the scolex gain access to the alimentary canal of a warmblooded vertebrate.  In this case, the scolex attaches itself to
the mucous membrane of the intestinal tube by means of its
cephalic hooklets (when these are present) and suckers. The
caudal vesicle now drops off, and the scolex is thus converted
into the "head" of the tape-worm.   Gemmation then comFig. 48.-Morphology of Taeniada. x. Ovum containing the embryo in its leathery
case. 2. Cysticercus longico/lis. 3. "Head" of adult Tania solium enlarged, showing the hooklets and cephalic suckers. 4. A single generative joint, or proglottis, magnified, showing the dendritic ovary (o), the generative pore (a), and the water-vascular
canals (b). 5. A portion of a Tape-worm (strobila), showing the alternate arrangement of the generative pores.
mences from its posterior extremity, the first segments being
immature.   As the first-formed joints, however, are pushed
further from the head by the constant intercalation of fresh
articulations, they become sexually mature, thus constituting
the "proglottides" of the adult Tape-worm  with which the
cycle began. To the entire organism, with its " head" and its
mature and immature joints (" proglottides"), the term  "strobila" is now applied.
In the development, therefore, of the Tape-worm we have
to remember the following stages:I. Thie ozum, set free from a generative joint, or proglottis.




170             MANUAL OF ZOOLOGY.
2. The proscolex, or the minute embryo which is liberated
from the ovum, when this latter has been swallowed by any
warm-blooded vertebrate.
3. The scolex, or the more advanced, but still sexually imperfect, embryo, into which the piroscolex develops, when it has
encysted itself within the tissues of its host.  (Under this head
come the so-called " Cystic Worms.")
4. The strobila, or adult Tape-worm, into which the rcolex
develops itself, when received into the alimentary canal of a
warm-blooded vertebrate. The strobila is constituted by the
" head," and by a number of immature and mature generative
segments or joints, termed the " proglottides."
The subject will, perhaps, be more clearly understood by
following the development of one of the common Tape-worms
of man-viz., the Tenia soliumn.  Commencing with an individual who is already suffering from the presence of this parasite, one of the most distressing symptoms of the case is found
to be the escape of the joints of the animal from the bowel.
These joints are the ripe " proglottides," containing the fecundated ova. When the ova-which are microscopic in sizeare liberated by the decomposition. of the proglottis, they may
gain access to water, or be blown about by the wind. In
many ways, it is easy to understand how one of them may be
swallowed by a pig. When this occurs, a " proscolex" is liberated from the ovum, and bores its way through the walls of
the stomach, to become a " scolex." It now takes up its abode,
generally in the muscles, in which position it was originally
described as a cystic worm under the name of Cysticercus ce/lulosee, constituting what is commonly known as the " measles "
of the pig. In this state the scolex will continue for an indefinite period; but if a portion of " measly" pork be eaten by
a man, then the scolex will develop itself into a tape-worm.
The scolex fixes itself to the mucous membrane of the intestine, throws off its caudal vesicle, and commences to produce
"proglottides" instead, becoming, thus, the " strobila " of the
Tcfnia solium, with which we originally started. The other
common tape-worm of man-viz., the  cenia mediocanellata-is
derived ir an exactly similar manner from the "measles" of
the ox. The young, however, of another of the Tape-worms of
man (viz., the Bot/riocephalus latus) is said not to be " cystic."
In like manner, the tape-worm of the cat (Tielia crassicollis)
is the mature form of the cystic worm of the mouse (Cysticercus
fasciolaris); the tape-worm  of the fox (Tenia piszformis) is
derived from the cystic worms of hares and rabbits (Cysticercus
pisiformis); and the tape-worm of the dog (Taenia serrata) is




ANNULOIDA: SCOLECIDA.                 II
the developed form of the Cenurus cerebralis of the sheep, the
cystic worm which causes the "staggers " in the latter animal.
Besides tape-worms, however, man is liable to be affected
with " scolices," which are the larvae of the tape-worms of other
animals. Thus, what are professionally called "hydatids" in
the human subject, are really the scolices of the tape-worm of
the dog. The disease is indicated by the presence of the socalled "hydatid-tumour," which consists of a strong membranous cyst-the " hydatid " proper-situated in some solid organ,
most commonly the liver, and filled with a watery fluid. To
the interior of the cyst are attached numerous minute scolices,
many others also floating freely in the contained fluid. These
"Echinococci," as they are called, do not differ in structure
from other scolices, consisting of a. head, provided with four
suckers and a circlet of recurved hooklets, a vesicular body,
and an intermediate contracted portion or neck. The Echinococci multiply within the hydatid cyst by gemmation, but
they develop no reproductive organs. If, however, an Echinococcus should gain access to the alimentary canal of a dog,
it then becomes the tape-worm peculiar to that animal —the
Teenzia echinococcus.
CHAPTER XXV.
TREMA TODA AND TURBELLARIA.
ORDER TREMATODA.-ThiS order includes a group of animals,
which, like the preceding, are parasitic, and are commonly
known as " suctorial worms," or " Flukes."  They inhabit various situations in different animals —mostly in birds and fishes
-and they are usually flattened or roundish in shape. The
body is provided with one or more suctorial pores for adhesion.
An intestinal canal, with one exception, is always present, but
this is simply hollowed out of the substance of the body, and
does not lie in a free space, or "perivisceral cavity." The
intestinal canal is often much branched, and possesses but a
single external opening, which serves alike as an oral and an
anal aperture, and is usually placed at the bottom of an anterior suctorial disc. The sexes are united in the same individual. A "water-vascular system" is always present, and is
sometimes "divided into two portions, one with contractile and
non-ciliated walls, the other with non-contractile and ciliated
walls."-(Huxley.)
9




172               MANUAL OF ZOOLOGY.
The Trematode IWorms are all hermaphrodite, and they pass
through, a' series of changes in their development somewhat
analogous to those observed in the Ttaniada.  This subject,
however, is still involved in great obscurity, and it is too complicated to admit of description in this'place:. The larvae are
often tailed, but never possess cephalic hooklets, and are never
" cystic."
From  the absence of a perivisceral cavity, the Trematoda
were formed by Cuvier into a separate division of Entozoa, under the name of Vers Intestinaux parenchymnateux, along with
the Teniada and Acant/hocep/ala, in which no alimentary canal
is present. By Owen, for the same reason, they are included
in a distinct class, under the name of Sterelmintha.
The Distoma hepaticum  (fig. 49) may be taken as the type of
the Tremantoda.  It is the common " Liver-fluke " of the sheep,
a                   a
b, e               e
2
Fig. 49.-Trematoda. I. Distomra hepaticum, the " Liver-fluke," showing the branched
alimentary canal. 2. Anterior extremity of Distonza lanceolatum. a Anterior
sucker; b Posterior sucker; c Generative pore; d CEsophagus; e Alimentary canal.
(After Owen.)
and inhabits the gall-bladder or biliary ducts, giving rise to the
disease known as the "rot." In form it is ovate, and flattened
on its two sides, and it presents two suctorial discs, the anterior of which is perforated by the aperture of the mouth, whilst
the posterior is impervious.  Between the suckers is the
" genital pore," at which the efferent ducts of the reproductive
organs open  on the exterior.  A  branched water-vascular
system is present, and opens posteriorly by a small aperture.
The alimentary canal bifurcates shortly behind the mouth, the
two divisions thus produced giving off numerous lateral diverticula, and terminating posteriorly in blind extremities. The
nervous system consists of a ring round the gullet, giving off
filaments both forwards and backwards. The larvae of Distoila
are tailed or "cercariform," arid are found in the interior of
fresh-water snails.




ANNULOIDA: SCOLECIDA.                  173
In Distoma lanceolatum (fig. 49, 2) the intestine has not the
ramose, complex character of that of D. heJ5aticum. On the
other hand, the alimentary canal, after its bifurcation, is continued on each side of the body to the posterior extremity
without giving off any branches on the way, and it terminates
simply in blind extremities.
Di2p/ostoinum, in its essential characters, does not differ
much from Disfoana; but it is found living gregariously in the
vitreous humour and lens of the eyes of certain fresh-water
fishes, such as the common Perch.
Other members of the order infest the intestines of birds and
Batrachians, the gills of fishes, or the paunch of Ruminants.
ORDER TURBELLARIA.- The members of this order are
almost all aquatic, and are all non-parasitic; thus differing
entirely from the animals which compose the two preceding
orders. Their external surface is always and permanently ciliated, and they never possess either suctorial discs or a circlet
of cephalic hooklets.  A "water-vascular system" is always
present, opening externally by one or more apertures, or appearing to be entirely closed in the adult (Nem-ertida).  As in
the Trematoda, the alimentary canal is imbedded in the parenchyma of the body, and, except in the Nenzerti.Ia, there is
no "perivisceral cavity."  The intestine is either straight or
branched, and a distinct anal aperture may, or may not, be
present. The nervous system consists of ganglia situated in
the fore-part of the body, united to one another by transverse
cords, and sending filaments backwards.
The Turbellaria are divided into two sections, termed respectively the Planarida and the Nemertida.
SUB-ORDER I. PLANARIDA.-The Planarians (fig. 50) are
mostly ovoid or elliptical in shape, flattened, and soft-bodied.
They are for the most part aquatic in their habits, occurring
in fresh water, or on the sea-shore, but occasionally found in
moist earth. The integument is abundantly provided with
vibratile cilia, which subserve locomotion, and it also contains
numerous cells which have been compared to the "cnidae," or
nettle cells, of the Ceientera/a. There is always a considerable
portion of the body situated in front of the mouth, constituting
the so-called " pre-oral region," or " prostomium "; and this is
often modified into a singular protrusible and retractile organ,
called the " proboscis," the exact use of which is not known.
The mouth opens into a muscular pharynx, which is often evertible; and the intestine may be either straight or branched,
but always terminates cecally behind, and is never provided
with an anal aperture.  The " water-vascular system " commu



174               MANUAL OF ZOOLOGY.
nicates with the exterior by two or more contractile apertures.
The nervous system consists of two ganglia, situated in front
of the mouth, united by a commissure, and giving off filaments
in various directions.   Pigment-spots, or rudimentary eyes,
from  two to sixteen in number, are often present, and are always placed in the prae-oral region of the body. The male and
female organs are united in the same individual, and the process of reproduction may be either sexual, by means of true
ova, or non-sexual, by internal gemmation or transverse fission.
X %o  
1             2            3          4
gn
Fig. 5o.-Morphology of Turbellaria.. Planaria torva (Muller); on Mouth; g
Nerve-ganglion; e Eyes; ov Ovary; t Testis; gn Genitat opening. 2. Planaria
lacten, showing the branched (dendroccel) intestine. 3. Microscopic larva of Alaurina, a marine Turbellarian.  4. Pilidium, the "pseudembryo" of a Nemertid;
a The alimentary canal; b Rudiment of the Nemertid.
The Planarianzs have been divided into two sections, as
follows:Section A. RHABDOCCELA.-Intestine straight, not branched.
Body elongated, rounded, or oval.
Section B. DENDROCCELA.-Intestine branched or arborescent.
Body flat and broad.
SUB-ORDER II. NEV.ERTIDA.-The Nemertida, or "Ribbonworms," agree in most essential respects with the Planarida.
They are distinguished, however, by their elongated, vermiform shape, by the presence of a distinct anus, by the possession of a distinct perivisceral cavity, by the absence of an
external aperture to the water-vascular system of the adult,
and by the fact that the sexes, with one or two exceptions, are
distinct.  The Nernerlida further differ from  the other P/atyelimia in possessing a pseudohaemal system in addition to, and
distinct from, the water-vascular system.
Reproduction takes place by the formation of true ova, by
internal gemmation, or by transverse fission.  In Neniertes,
however, the egg gives rise to a larva, from which the adult is




ANN ULOIDA: SCOLECIDA.               175
developed in a manner closely analogous to that described as
characteristic of the Echinodermala. The larval form of NVenierles was described by Johannes Muller, under the name of
Pilidium (fig. 50, 4). It is "a small hemet-shaped larva, with
a long flagellum attached like a plumelto the summit of the
helmet, the edges and side-lobes of which are richly ciliated.
A simple alimentary canal opens upon the under surface of
the *body between the lobes.  In this condition the larva
swims about freely; but, after a while, a mass of formative
matter appears on one side of the alimentary canal, and, elongating gradually, takes on a worm-like figure. Eventually it
grows round the alimentary canal, and, appropriating it, detaches itself from the Pi/idium as a Nemertid-provided with
the characteristic proboscis, and the other organs of that grouF
of Turbellaria."-(Huxley.)
CHAPTER XXVI.
VEMA TELMIA.
I. ACANTHOCEPHALA.  2. GORDIACEA. 3. NEMATODA.
DIVISION II. NEMATELMIA.-This section may be considered
as comprising those Scolecids in which the body has an elongated and cylindrical shape.  Strictly speaking, it should
include the Nemertida, but the division is not founded upon
anatomical characters, and is employed here simply for convenience. Most of the Nema/elmia possess an annulated integument; but there is no true segmentation, and there are
rarely any locomotive appendages attached to the body. The
majority are unisexual, and parasitic during the whole or
a part of their existence.  Three orders are comprised in
this division-viz., the Acanthocephala, the Gordiacea, and the
emanatoda.
ORDER I. ACANTHOCEPHALA.-The Acanthocephala are entirely parasitic, vermiform in shape, and devoid of any mouth
or alimentary canal. They are provided with a kind of snout
or proboscis armed with recurved hooks, which is continued
backwards into a bandlike structure (ligamenfzum suspensorium),
to which the reproductive organs are attached. " Immediately
beneath the integument lies a series of reticulated canals containing a clear fluid, and it is difficult to see with what these




i76              MANUAL OF ZOOLOGY.
can correspond if not with some modification of the watervascular system." —(Huxley.) This system of water-vasculaI
canals, however, does not communicate, so far as is known,
in any way with the exterior.  At the base of the proboscis
is placed a single nervous ganglion, which gives off radiating
filaments in all directions.
Besides the presence of a water-vascular system and the
absence of any alimentary canal, another point of affinity
between the Acanthzocephala and the Tcniada has recently
been established by the discovery that the adult worm is
developed within a hooked embryo, from which it is secondarily produced.
The "Thorn-headed worms" include some of the most
formidable parasites with which we are acquainted.  The,Ec/ziizo-/ahyic/zus (fig. 51) is found in the intestinal canal of
many vertebrate animals, especially of birds and fishes.
ORDER II. GORDIACEA.-The Gordiacca,
or " Hair-worms," are thread-like parasites,
which in the earlier stages of their existence
inhabit the bodies of various insects, chiefly
of beetles and grasshoppers. They possess
a mouth and alimentary canal, but they are
not provided with a distinct anal aperture.
In Gordius itself the gullet is said to open
directly into the body-cavity; but it is more
probable that this is an error, and that
there is a complete intestine opening posteriorly into a cloaca.  The sexes are distinct, and they leave the bodies of the in-'~   & >    sects which they infest in order to breed;
subsequently depositing their ova in long
chains, either in water or in some moist
phalla - a Echinor-  situation.  At the time of its migration the
hyeckus,igas, nat.  mouth of the adult Gordius appears to be
size; a' The head of
the same magnified.  obliterated, and the anterior portion of the
alimentary canal becomes atrophied.
In form the Gordiacea are singularly like hairs, and they
often attain a length many times greater than that of the inscct
which harbours them.
ORDER III. NEMATODA (or Nematoidea).-The Nerzatoda"Thread-worms" or "Round-worms "- are of an elongated
and cylindrical shape; and are often, though by no means
always, parasitic in the interior of other animals.  They possess
a distinct mouth and an alimentary canal which is freely suspended in an abdominal cavity, and terminates posteriorly in a




ANNULOIDA: SCOLECIDA.                  I77
distinct anus. They also possess a system of canals, in some
cases contractile, which open externally near the anterior part
of the body, on the ventral surface, or by lateral pores, and are
probably homologous with the water-vascular system of the
zceniada and  irematoda.  The sexes are distinct, and the
males are usually less frequently met with,- and of smaller
size, than the females. - The nervous system is mostly well
developed, and is in the form of a ganglionic ring, surrounding the cesophagus, and sending filaments backwards.
As before said, most of the ANenatoda are internal parasites,
inhabiting the alimentary canal, the pulmonary tubes, or the
areolar tissue, in man and in many other vertebrate animals;
but a large section of the order are of a permanently free habit
of existence.
The most familiar examples of the
parasitic Xematoda are the Ascaris
lumbricoides, the little Oxyuris, the
Trichina, and the Guinea-worm.
The Ascaris lumbricoides, or common Round-worm, inhabits the intestine of man, often attaining a length T
of several inches. The ova are probably expelled with the faeces, and
the embryo is developed within the
ovum  prior to its.rupture.  When
fully formed, the embryo is about
one-hundredth of an inch in length,
and its development is not exactly
known, though it appears to be directly transferred from river or pond
water to the alimentary canal of some
vertebrate animal.
The   Oxyuris  vermicularis,  or
"Small Thread-worm," is a gregarious worm, which  inhabits the
rectum, especially of children.  It
is the smallest of the intestinal
worms of man, its average length
not being more than a quarter of   A                B
an inch, but the females are much
bigger than the males.              Fig. 52.-Nematoda. AAngu.
The Trichina sfiralis is a singular   stagais. Magnified.
Nematoid, which gives rise to a painful and very generally fatal train of symptoms, somewhat resembling rheumatic fever, and known as Trichiniasis. The




I78             MANUAL OF ZOOLOGY.
Trichiza is known in two different conditions, sexually immature or mature. In its sexually immature condition it inhabits
the muscles, usually of the pig, in vast numbers, each worm
being coiled up in a little capsule or cyst. In this condition
the worm is incapable of further development, and may remain, apparently for an indefinite period, without change,
and without seeming to produce any injurious results to the
animal affected. If, however, a portion of trichinatous muscle
be eaten by a warm-blooded vertebrate, and so introduced into
the alimentary canal, an immediate development of young
Trichine is. the result. The immature worms escape from
their enveloping cysts, grow larger, develop sexual organs,
and give birth to numerous progeny, which they produce
viviparously.  The young lrichinZa  thus produced perforate
the walls of the alimentary canal, and, after working their
way amongst the muscles, become encysted.  If the animal
in which these changes go on has sufficient vitality to bear
up under the severe symptoms which are produced by the
migration of the Trichzine, he is now safe; since they cannot become sexually mature, or develop themselves further,
until again transferred to the alimentary canal of some other
animal.
The Guinea-worm (Dracunculus or filaria medinensis) is
a Nematode worm, which inhabits, during one stage of its
existence, the cellular tissue of the human body, generally
attacking the legs, and often attaining a length of several feet.
All known specimens of this parasite are impregnated females,
containing a large number of young. The worm remains imbedded in the body, in a more or less quiescent condition, for
a year or more, at the end of which time it seeks the surface,
in order to get rid of its young.  No external aperture to the
genital organs has hitherto been proved to exist, and it seems
possible that the young are produced within the body of the
parent by a process of internal gemmation. The young Eilaria
consists of a vermiform body, terminating in a hair-like tail;
and when set free from the parent, its further development
probably takes place in water, when it is believed to be converted into one of the "Tank-worms" so common in India. In
this condition it is possible, as some believe, that sexual organs
are developed, and that the females are impregnated. The
worm is believed to gain access to the body of bathers, when
still extremely minute. According to Dr Bastian, however, it
appears probable that the Guinea-worm " is a parasite only
accidentally, and that it and its parents were originally free
Nematoids."




ANNULOIDA: ROTIFERA.                 I79
The second section of the NematodaE comprises worms, which
are not at any time parasitic, but which are permanently free.
These "free Nematoids" (fig. 52) constitute the family of the
Anguilluzide, of which about two hundred species have been
already described, mostly inhabiting fresh water or the shores
of the sea. They resemble the parasitic Nematoids in all the
essential features of their anatomy, but they differ in often
possessing pigment-spots, or rudimentary eyes, in being mostly
provided with a terminal sucker, and in bringing forth comparatively few ova at a time; the dangers to which the young
are exposed being much less than in the parasitic forms.
Amongst the more familiar Nematoids are the Vinegar Eel
(Annguillula aceti, fig. 52, A) and the Zylenchus (or Vibrio)
tritici, which produces a sort of excrescence or gall upon
the ear of wheat, causing the disease known to farmers as
the " Purples," or " Ear Cockle."
The parasitic and free Nematoids are connected together by
an Ascaris (A. nzrovenosa), which in succeeding generations is
alternately free and parasitic.  This Ascaris has long been
known as inhabiting the lungs of the frog, but it has been
shown by Mecznikow that "the young of this animal become
real, free Nematoids; for, after passing from  the intestine of
the frog into damp earth or mud, they grow rapidly, and
actually develop in the course of a few days, whilst still in this
external medium, into sexually mature animals. Young, differing somewhat in external characters from their parents, are
soon produced by them, and these attain merely a certain
stage of development whilst in the moist earth, arriving at
sexual maturity only after they have become parasites, and are
ensconced in the lung of the frog."-(Bastian.) This extraordinary history is rendered still more remarkable, if it should
be proved that the young of the parasitic forms of this Ascaris
are produced by a process of parthenogenesis; and this seems
to be highly probable, since none of the individuals which are
found as parasites are males, but are universally females.
CHAPTER XXVII.
RO TIFERA.
SUB-CLASS ROTIFERA (Rotatoria).-The Rotifera, or " Wheelanimalcules," constitute a very natural group, the exact position




I80              MANUAL OF ZOOLOGY.
of which has been a good deal disputed, and is still doubtful.
They are looked upon here as a distinct division of the Scolecida, following Huxley; but they are very frequently placed
with the Anne/ida amongst the lower division of the Annulosa
(Anarthropoda).
The Rotifera are Annuloida of a minute size, never parasitic,
inhabiting water, and usually provided with an anterior ciliated
disc, capable of inversion and eversion.  In the females there is
a distinct mouth, intestinal canal, and anus.  A nervous system
is also present, consisting of ganglia, situated near the anterior
extremity of the body, and sendingfilaments backwards. A watervascular system is also present.
Most of the Roltfera are entirely invisible to the naked
eye, and they are all extremely minute, none of them attaining a greater length than I-36th of an inch. Nevertheless,
as remarked by Mr Gosse, "so elegant are their outlines,
so brilliantly translucent their texture, so complex and yet so
patent their organisation, so curious their locomotive wheels, so
unique their apparatus for mastication, so gracefil, so vigorous,
so fleet, and so marked with apparent intelligence their movements, so various their forms and types of structure," that they
form one of the most interesting departments of zoological and
microscopical study. They are all aquatic in their habits, and
in the great majority of cases are free-swimming animals, some,
however, being permanently fixed, as is the case with Stephanoceros, Melicerta (fig. 53, B), and Eloscularia.  They are usually
simple, but are occasionally composite, forming colonies, as in
MAfgalotrocha.  As a rule, the male and female Rolifera differ
greatly from one another, the males being smaller than the
females, destitute of any masticatory or digestive apparatus,
and more or less closely resembling the young form of the
species. The most characteristic organ in the great majority
of the Rotifera is the so-called "wheel-organ," or "trochal
disc," which is always situated at the cephalic or distal end
of the body, and consists of a retractile dis'c surrounded by a
circlet of cilia, which, when in action, vibrate so rapidly as to
produce the illusory impression that the entire disc is rotating.
The disc, which carries the cilia, is capable of eversion and
inversion, and may be circular, reniform, bilobed, four-lobed,
or divided into several lobes. It serves the purpose of locomotion in the free-swimming forms, acting somewhat like the
propeller of a screw-steamer, and in all it serves to produce
currents in the water, which convey the food to the mouth.
In Chetonotus, and one or two other forms, there is no true
wheel-organ, capable of protrusion and retraction, but the cilia




ANNULOIDA: ROTIFERA.                         181
are variously disposed over the surface of the body. The
C/htonoti or Hairy-backed Animalcules have no jaws, and have
the ventral surface of the body clothed with cilia. They have
usually been placed in.the  Turbellaria, but there seem  to be
good reasons for regarding them as an aberrant group of Rotatoria.
The proximal extremity of the body in the free forms terminates in a caudal process, or" foot," sometimes telescopic,
which ends in a suctorial disc, or in a pair of diverging "toes,"
which act as a pair of forceps (fig. 53, A).
AFig. 53.-Rotifera. A Diagrammatic representation of lfydat.'nt setta (generalised
from Pritchard). a Depression in the ciliated disc leading to the digestive canal; b
Mouth; c Pharyngeal bulb or mastax, with the masticatory apparatus; d Stomach;
e Cloaca; fContractile bladder; gg Respiratory or water-vascular tubes; h Nerveganglion giving filament to ciliated pit (k); o Ovary. B Melicerta ringens. (After
Gosse.)
The mouth usually opens into a pharynx, or "buccal funnel,"
which is generally provided with a muscular coat, constituting
the " mastax " or " pharyngeal bulb," and which generally contains a very complicated masticatory apparatus." The parts
of this apparatus are horny, and are believed by Mr Gosse
to be homologous with the parts of the  mouth in Insects.
In the females of almost all known species of Rotifera the
intestinal canal is a more or less simple tube, extending
The lower jaws, or " incus," consist of a fixed portion, the " fulcrum,"
to which are attached two movable blades-the " rami." The upper jaws,
or "mallei," consist each of a handle, or "manubrium," to which is hinged
a toothed blade, or " uncus."




I82              MANUAL OF ZOOLOGY.
through a well-developed perivisceral cavity, and terminating-posteriorly in a dilatation, or "cloaca," which forms the
common outlet for the digestive, generative, and water-vascular
systems.
In both sexes there is a well-developed water-vascular system, usually consisting of the following parts:-In the hinder
part of the body, close to the cloaca, and opening into it, is a
sac or vesicle, which is termed the " contractile bladder," and
exhibits rhythmical contractions and dilatations. From the
contractile bladder proceed two tubes —" the respiratory tubes 
-which pass forwards along the sides of the body, and terminate anteriorly in a manner not quite ascertained. Attached
to the sides of the respiratory tubes, in all the larger Rolzfera,
is a series of ovate or pyriform vesicles, each of which is furnished internally with a single central cilium, which is fixed to
the free end of the vesicle. It is asserted, however, that these
ciliated vesicles communicate internally with the perivisceral
cavity with its contained corpusculated fluid. The exact function of this water-vascular system is not known, but it is most
probably respiratory and excretory. Dr Leydig believes that
water enters the perivisceral cavity by endosmose, where it
mingles with the absorbed products of digestion, to form the
so-called "chylaqueous fluid"; and that the effete fluid is
excreted by the respiratory tubes, and ultimately discharged
into the cloaca by the contractile bladder. Taking this view
of the subject, Mr Gosse believes that " the respiratory tubes
represent the kidneys, and that the bladder is a true urinary
bladder "; and consequently that "the respiratory and urinary
functions are in the closest relation with one another." This
observer, further, finds a decided analogy between the above
system in the Rdtifera and the long and tortuous renal tubes
of the Insecta, to which class he believes the Rotifera to be
most nearly allied. No central organ of the circulation or
heart and no organs of respiration are present, but the perivisceral cavity is filled with a corpusculated fluid.
The nervous system  of the Rolzfera constitutes a bilobate
cerebral mass, "which for its proportionate volume may compare with the brain of the highest vertebrates." It is placed
anteriorly, and usually on the dorsal aspect of the body, and
the eye  in the shape of a red pigment spot or spotsis invariably situated like a wart upon it.  Other senseorgans, probably tactile, are often present in the form of
two knobs surmounted by tufts or bristles, placed at the back
of the head.  The ovaries constitute conspicuous organs in
the female Rotlfera, but in summer the young Rotifers appeal




ANNULOIDA: ROTIFERA.                  I83
to be produced by the females without having access to the
males.
The muscular system of the Rotifera is well developed, consisting of bands which produce the various movements of the
body and foot, whilst others act upon the various viscera, and
others effect the movements of the jaws.
The typical group of the Rotifera is that of the Notommatina
(Hydatinea of Ehrenberg). In this group the animals are all
permanently free, and are never combined into colonies, while
the integument is flexible, and the body is never encased in a
tube.
Stephanoceros and Floscularia, on the other hand, are fixed,
and are enclosed in a gelatinous tube which is secreted by the
animal. Melicerta (fig. 53, B) inhabits a tubular case, which
the animal forms for itself by means of a special organ for the
purpose; whilst Polyartlra and Triarthra are protected by a
stiff shell, or " lorica."
In  iriarthra there are twelve ensiform fins, jointed to the
body by distinct shelly tubercles, and moved by powerful
muscles. These natatory organs are considered by Mr Gosse
to be homologous with the articulated limbs of the Artlropodla.
In Asplanchnia, whilst the masticatory organs, gullet, and
stomach are well developed, there is no intestine, the stomach
"hanging like a globe in the centre of the body-cavity," but not
communicating with the body-cavity.
AFFINITIES OF ROTIFERA.-In their external appearance the
Rotifera approximate closely to the Infusoria, but the organisation of the former presents a very striking advance when compared with that of the latter. Thus, in the Infisoria there is
no differentiated body-cavity, bounded by distinct walls, and
the alimentary canal is imperfect, the digestive sac simply
opening inferiorly into the diffluent sarcode of the centre of
the body. Further, there are no traces of a nervous system,
and the contractile vesicles, if looked upon as representing the
water-vascular system, are a very rudimentary form  of this
apparatus.  In the Rotifera, on the other hand, the alimentary
canal forms a complete tube, having an oral and an anal aperture, and not communicating with the surrounding perivisceral
cavity; and there is a well-developed nervous system, and a
highly complex water-vascular system. A real affinity is found
to subsist, however, between the Rotzfera and the Planarida;
both possessing external cilia, a nervous system, and a welldeveloped water-vascular apparatus, the characters of which are
not dissimilar in the two groups. In the Plan4rida, how



184            MANUAL OF ZOOLOGY.
ever, the sexes are united in the same individual, and there is
no anal aperture; whereas in the Ro/ifera the sexes are distinct, and there is a distinct anus. To the true Arthropoda, as
already pointed out, the Rotifera shows some points of affinity,
but these are hardly sufficiently numerous or decided to warrant the removal of the group from the Annuloida to the
Annulosa.




A 2VN UL O SA.
CHAPTER XXVIII.
A NNULZ OSA.!. GENERAL  CHARACTERS  OF ANNULOSA.   2. GENERAL
CHARACTERS OF ANARTHROPODA. 3. CLASS GEPHYREA.
4. GENERAL CHARACTERS OF THE CLASS ANNELIDA.
SUB-KINGDOM ANNULOSA.-The members of this sub-kingdom
are distinguished by the possession of a body which is conmposed
of numerous segments, or "somites," arranged along a longitudinal
axis. A nervous system is always present, and consists of a double
chain of ganglia, running along the ventral surface of the body,
and traversed anteriorly by the esophagus (fig. 54).  The limbs
(when present) are turned towards the neural aspect of the body.
The sub-kingdom Annulosa may be divided into two primary
divisions, according as the body is provided with articulated
appendages, or not; these divisions being termed respectively
b
Fig. 54.-Diagram of an Annulose Animal. a Blood-vascular or hemal system;
b Digestive system; c Neural system.
the Arthropoda and Anarthropoda.  The first of these comprises Crustaceans, Spiders, Scorpions, Centipedes, and Insects;
whilst the latter includes the Spoon-worms, Leeches, Earthworms, Tube-worms, and Sand-worms.
DIVISION I. ANARTHROPODA.-In this division of the Annulosa the locomotive &ppendages are never distinctly jointed or articulated to the body. In this division are included three classes,
viz.:-the Gephyrea, the Annelida, and the Chaetognatha.
CLASS I. GEPHYREA (= Sizjunculoidea).-This class includes
certain worm-like animals in which the body is sometimes ob



i86             MANUAL OF ZOOLOGY.
viously annulated, sometimes not; but there are no ambulacral
tubes nor foot-tubercles, though there are sometimes bristles
concerned in locomotion. The nervous system consists of an
cesophageal nerve-collar and a cord placed along the ventral
surface of the body.
The Sipunciu/us and its allies (fig. 55) make up this class,
and from their affinity to the worm-like Holothurians they have
often been placed amongst the Echinodermata.  They are not,
however, provided with an ambulacral system, the integument
is not capable of secreting calcareous matter, and there are no
traces of any radiate arrangement of the nervous system.
The Sipunculus is a worm which is found burrowing in the
sand of the coasts of most of our European seas, or which inhabits the cast-away shells of dead univalve Molluscs. The
different species differ much in length, varying from half an
inch to a foot or more. The body is cylindrical, covered by a
delicate cuticle, beneath which is a thick, muscular, and highly
Fig. 55. —Gephyrea. XSyrznx nudus. (After Forbes.)
contractile coat.  The anterior portion of the body forms a
retractile trunk or proboscis, at the extremity of which is the
mouth surrounded by a circlet of simple tentacles. The alimentary canal is proportionately of great length, and is much
convoluted.  Upon reaching the posterior extremity of the
body it is reflected forwards, and it terminates in a distinct
anus, which is placed anteriorly near the junction of the body
with the proboscis. The sexes are distinct in all the Gcjhyrea,
and the young pass through a metamorphosis.
In Echiurus, which is found on the coasts of the North Sea,
the body is provided posteriorly with zones of horny bristles;
and in the Sternaspis of the Adriatic similar zones of bristles
are found anteriorly as well as posteriorly.  In the Echiurii&e,
also, there are branched tubes connected with the termination
of the intestine, which are doubtless homologous with the
" respiratory tree" of the Holothurians.  In Bonellia there is a
proboscis formed by a folded fleshy plate, susceptible of great




ANNULOSA: ANNELIDA.                         s7
elongation, and forked at its extremity.  The vent is at the
opposite end of the body, and the intestine is very long, and
folded several times.
The British species of the class are grouped by Professor E.
Forbes as follows:Farm. I. Sizpunculacea, having a retractile proboscis, at the
base of which the anus is placed, and round the extremity of
which is seen a circlet of tentacles.
arnm. II. Priapulacea, having a retractile proboscis but no
tentacula, and having the anus placed at the extremity of a
long, filiform, caudal appendage.
aram. III. Thalassemacea, having a proboscis to which a long
fleshy appendage is attached. There are no oral tentacula, and
the anus is placed at the posterior extremity of the body.
CLASS II. ANNELIDA (= Annulata).-The Annelida are distinguished from the preceding by the possession of distinct
external segmentation; the nervous system is composed of a
ventral, double, gangliated cord, with an cesophageal collar
and prse-cesophageal ganglion.
This class comprises elongated, worm-like animals, in which
the integument is always soft, and the body is more or less
distinctly segmented, each segment usually corresponding with
a single pair of ganglia in the ventral cord. All the segments
are similar to one another except those at the anterior and
posterior extremities of the body. Each segment may also be
provided with a pair of lateral appendages, but these are never
articulated to the body, and are never so modified in the region
of the head as to be converted into masticatory organs.
In the higher Annelida each segment (fig. 56) consists of two
Fig. 56.-Diagrammatic transverse section of an Annelide. d Dorsal arc; v Ventra
arc; n Branchize; a Notopodium or dorsal oar; b Neuropodium or ventral oar, both
carrying setae and a jointed cirrhus.
arches, termed, from their position, respectively the "dorsal
arc " and the "ventral arc"; and each bears two lateral pro



188             MANUAL OF ZOOLOGY.
cesses, or "foot-tubercles" (parapodia), one on each side.
Each "foot-tubercle" is double, being composed of an upper
process, called the "notopodium," or "dorsal oar," and a lower
process, termed the "neuropodium," or "ventral oar." The
foot-tubercles, likewise, support bristles, or "setze," and a soft,
cylindrical appendage, which is termed the "cirrhus" (fig. 56).
The number of the segments varies much, being as many as
400 in Eunice gigantea; and, generally, there is not a distinct
head which is separable from the succeeding rings of the body.
When such a distinct head appears to be present, it is not comparable with the head of the Arthropoda, but is really a greatly
modified prxe-oral region, or "'prostomrium," as is shown by
the position of the mouth.
The digestive system of the Annelides consists of a mouth,
sometimes armed with horny jaws, a gullet, stomach, intestine,
and a distinct anus.  Except in the Hirudinea, the alimentary
canal is suspended in a capacious perivisceral space, divided
into compartments by more or less complete partitions. The
alimentary canal is, with one exception, not convoluted, and
extends straight from the mouth to the anus; but lateral diverticula are often present.
As regards the vascular system, " no Annelide ever possesses
a heart comparable to the heart of a Crustacean or Insect;
but a system of vessels, with more or less extensively contractile walls, containing a clear fluid, usually red or green in
colour, and in some cases only corpusculated, is very generally
developed, and sends prolongations into the respiratory organs,
when such exist."-(Huxley.)  This system has been termed
the "pseudo-haemal system," and its vessels are considered by
Professor Huxley as being " extreme modifications of organs
homologous with the water-vessels of the Scolecida "; since the
perivisceral cavity, with its contained corpusculated fluid (chylaqueous fluid), is believed by M. de Quatrefages to be the
true homologue of the vascular system of Crustacea and insects. The pseudo-haemal system, therefore, of the Annelides
is to be regarded as essentially respiratory in function. The
pseudo-haemal vessels are sometimes wanting, and in these
cases respiration appears to be effected by the cilia lining the
perivisceral cavity.
Respiration is effected by the general surface of the body,
by saccular involutions of the integument, or by distinct external gills, or branchie.
The nervous system consists of a double, ventral, gangliated
cord, which is traversed anteriorly by the oesophagus; the
"prae-cesophageal," or "cerebral," ganglia being connected by




ANNULOSA: ANNELIDA.                  I 89
lateral cords or commissureswith the "post-cesophageal"ganglia.
Pigment-spots, or " ocelli," are present in many, generally upon
the proboscis, sometimes in each segment, or on the branchiae,
or on the tail; and the head often supports two or more
feelers which differ from the "antennae " of Insects and Crustacea in not being jointed.
The sexes in the Annelida are sometimes distinct, and sometimes united in the same individual. The embryos are almost
universally ciliated, and even in the adult cilia are almost
always, if not always, present, in both of which respects this
class differs from the Arthrojooda.
The Annelida may be divided into two sections, characterised
by the presence or absence of external respiratory organs or
branchize.  The Abranchiate section comprises the Leeches
and the Earth-worms; whilst the Branchiate division includes
the Tube-worms (Tubicola) and the Sand-worms (Errantia).
The Annelida are also often divided into two sections, called
Ch/eophora and Discophora, according as locomotion is effected
by chitinous setoe (Earth-worms, Tube-worms, and Sand-worms)
or by suctorial discs (Leeches).
CHAPTER XXIX.
ORDERS OF A NNELIDA.
ORDER I. HIRUDINEA (Discophora or Suctoria).-This order
includes the Leeches, and is' characterised by the possession
of a locomotive and. adhesive sucker, posteriorly or at both
extremities, and.by the. absence of bristles and foot-tubercles.
The sexes are united in the same individual, and the young do
not pass through. any metamorphosis.
The.Leeches are. aquatic, vermiform animals, mostly inhabiting fresh water, though a few species are marine. Locomotion is effected either by swimming by means of a serpentine
bending of the body, or by means of one or two suctorial discs.
In those forms in which there is only a single sucker (posterior),
the head or anterior extremity of the body can be converted
into a suctorial disc. The body is ringed, as many as one
hundred annulations being present in the common Leech; but
it is not divided into distinct somites, and, with one exception,
there are no lateral appendages of any kind. The mouth is
sometimes edentulous, but it is usually armed with teeth. The




Igo90             MANUAL OF ZOOLOGY.
alimentary canal is short, and is united to the skin by means
of a spongy vascular tissue. The pseudo-haemal system consists principally of four great longitudinal trunks, connected by
lateral vessels, and devoid of any special dilatations." Respiration appears to be partly effected by means of a number ol
sacs, which are formed simply by an involution of the integument, and which open externally by minute apertures, termed
"stigmata."  In the common Leech there are about seventeen
of these vesicles on each side of the body, their openings being
placed on the abdominal surface. These saccular involutions
of the integument certainly secrete the mucus with which the
body of the animal is lubricated; and it is believed by some
that their function is solely excretory, and that they answer to
the kidneys of higher animals. In this case respiration must
be effected by the general surface of the body; but there is
no reason why the same organs should not perform both functions, since a close relationship subsists between the two.
These sacculi are generally known as
the "segmental organs," and in most
of the Hirudinea they are closed internally, and only open externally by the
j "stigmata."  In some of the flirudinea,
however, the "segmental organs" agree
with those of the great majority of the
Annelides in not only opening externally, but in also communicating internally with the perivisceral cavity. The
segmental organs of the Leeches differ
further from those of the other Annelida
in not being in any way connected with
the process of reproduction.
The nervous system consists of a
prxe-cesophageal ganglion, which gives
branches to a number of simple eyes,
or ocelli, which are placed on the head,
Fig. 57 —Hirudinea. a The and which is united by lateral cesophaMedicinal Leech (Sanguisu- geal cords to the ventral gangliated
ga oficinalis), natural size;
b Anterior extremity of the chain.
same magnified, showing the The sexes are united in the same
sucker and triradiate jaws;
c One of the jaws detached, individual, but the Leeches are nevershowing the semicircular
toothed margin.      theless incapable of self-fertilisation.
If Branchiobdella be regarded as a true Leech, then the absence of
gills is not universal in this order, for it possesses branchiae. It has two
suckers, and is parasitic on the Torpedo and on the gills of the Cray-fish.




ANNULOSA: ANNELIDA.                   I9I
Reproduction, also, is always effected by means of the sexes,
and never by fission or gemmation.
The common Horse-leech is only provided with a few blunt
teeth; but the Medicinal Leech (Sanguisugea oicinaZis, fig. 57)
has its mouth furnished with three crescentic jaws, the convex
surfaces of which are serrated with minute teeth. This species
is chiefly imported from Hungary, Bohemia, and Russia. In
Sanzguisuzai mendicinalis, also used in medicine, the abdomen
has numerous black spots.  In both species the oral and
caudal extremities are narrowed before dilating into the
suckers, and the body has from ninety to one hundred rings.
The marine Pontobdelle have the body tuberculated, and
attach themselves to the bodies of fishes, especially skates.
The anterior sucker is separated in these from the body by
a distinct constriction or neck.  In the little fresh-water
Clepsizj, the anterior sucker is wanting, and there is a proboscidiform mouth. They are found attached to the stems of
water-plants.
ORDER II. OLIGOCHETA (erricola).-The members of this
order, comprising the Earth-worms (Lumbricide) and the
Water-worms (Naiidida&), are distinguished by the fact that their
locomotive appendages are in the form of chitinous setae or
bristles, attached in rows to the sides and ventral surface of
the body. They are all hermaphrodite. The Oligochata are
divided into the two groups of the lierricole or Eartnworms,
and the Limicole or Mud-worms and Water-worms (Senuride
and Naididae).
In the common Earth-worm (Lumbricus) the body is cylindrical, attenuated at both extremities, and carrying in the adult
a thickened zone, which occupies from six to nine rings in
the anterior part of the'body, is connected with reproduction, and is termed the "clitellum," or "saddle."  Locomotion is effected by eight rows of short bristles or sete, four of
which are placed laterally and four on the ventral surface of
the body; these representing the foot-tubercles of the higher
Annelides. The mouth is edentulous, and opens into a short
cesophagus, which leads to a muscular crop, or " pro-ventriculus," succeeded by a second muscular dilatation, or gizzard.
The intestine is continued straight to the anus, and is constricted in its course by numerous transverse septa, springing
from  the walls of the perivisceral cavity.  The perivisceral
cavity (as in all the Oligochoeta) is lined by a cellular membrane, which is continuous with a yellow cellular layer covering
the intestine and large vessels, and which casts off its cells into
the perivisceral fluid. The pseudo-heemal system is well de



192             MANUAL OF ZOOLOGY.
veloped; and there exists, in even greater numbers, the same
series of lateral sacculi or " segmental organs" which we have
seen in the Leeches, and which have either a respiratory or a
renal function. In all the Oligoc/he/ta the segmental organs
communicate internally with the perivisceral cavity as well as
externally with the outer medium. A portion of the segmental
organs is ciliated, and in all cases the segmental organs of
certain of the segments have the special function of acting as
efferent ducts for the generative organs.
Of the little XNa'dide, the most familiar is the Tuzbife rivzulorum, which is of common occurrence in the mud of ponds
and streams. It is from half an inch to one inch and a half in
length, and of a bright-red colour. The pseudo-hoemal system
is provided with two contractile cavities or hearts; and there
is present the same system of lateral tubes, opening externally
by pores, as occurs in the Earth-worms.
The NVadidce are chiefly noticeable on account of the singular process of non-sexual reproduction which they present
before they attain sexual maturity. In this process the Nais
throws out a bud between two rings, at a point generally near
the middle of the body. Not only is this bud developed into
a fresh individual, but the two portions of the parent marked
out by the budding point likewise became developed into
separate individuals. The portion of the parent in front of the
bud develops a tail, whilst the portion behind the bud develops
a head. Prior to the detachment of the bud, other secondary
buds are formed from the same segment, each in front of the
one already produced; and in this way, before separation takes
place, a chain of organically connected individuals is produced,
all of which are nourished by the anterior portion of the primitive worm. Besides their non-sexual reproduction, the XNahlidie
possess generative organs when adult, and exhibit true sexual
reproduction. With the development of the generative organs,
a new segment is added to the body, and certain other modifications take place; so that the process of attaining sexual maturity is actually attended with a species of metamorphosis.
ORDER III. TUBICOLA ( Cephalobranchiata).-The Annelides
which are included in this order inhabit tubes, which may be
calcareous, and secreted by the animal itself, or may be composed of grains of sand or pieces of broken shell, cemented
together by a glutinous secretion from the body. The bodyrings are mostly provided with fasciculi of bristles set upon
lateral foot-tubercles or parapodia, by means of which the
animal is enabled to draw itself in and out of its tube. The
alimentary canal is loosely attached to the integument.  The




ANNULOSA: ANNELIDA.                     I92 
Tubicola are unisexual, and the young pass through a metamorphosis.
When the tube of a Tubicolar Annelide is a true calcareous
secretion from the body of the animal, it is, nevertheless,
readily distinguished from the shell of the Mollusca, by the fact
that there is no organic connection of any kind between the
animal and its tube.
The pseudo-hoemal system  has its usual arrangement, and
the contained fluid is usually red in colour, but is olive-green
in Sabel/a. The respiratory organs are in the form of filamentous branchize, attached to, or
near, the head, generally in two
lateral tufts, arranged in a funnelshaped or spiral form. Each filament is fringed with vibrating                   -
cilia, and the tufts are richly supplied with fluid from the pseudohaomal system. There is no spe-                           a
cial apparatus required to drive
the blood back  to the heart,
but this is effected by the contractile power of the gills themselves.  From  the position of  Fig. 58. —Tubicola. a Serfiul contortu/zicata, showing the branchia=
the branchiae upen, or near, the    and operculum; b Sflirorbis comhead, the  T2ibicola  are  often
known as the " cephalobranchiate" Annelides (fig. 58).
Reproduction in the Tzubicola is generally sexual, the sexes
being in different individuals; but spontaneous fission has also
been observed. As regards their development, the process has
been thus described, as it occurs in Terebella: —The embryo,
which is at first a free-swimming, ciliated body, "lengthens,
and the cilia, which were at first generally diffused, become
confined to a cincture behind the head, a transverse ventral
band near the tail, and a small circle round that part.  The
head is distinguished by two red eye-specks; new segments
are successively added, one behind the other, and always in
front of the anal one; but as yet the embryo is apodal. The
tubercles and setae are next developed in the same order, and
a free-swimming or " errant " Annelide ensues.  Finally, the
cilia of the buccal rings are lost, the young Terebella reposes,
and envelops itself in a mucous tube." —(Owen.)  As the
young tubicolar Annelide is thus free, or " errant," before it
becomes finally enveloped in a tube, it is generally'believed
that the Tibico/a should be looked upon as really higher than




194             MANUAL OF ZOOLOGY.
the next order of Annelida-viz. the Errantia.  It appears,
however, more probable that the stationary condition of the
adult  iubicola should rather be regarded as an instance of
" retrograde development."
The most familiar of the Tubicola is the Serpula (fig. 58, a),
the contorted and winding calcareous tubes of which must be
known to almost every one as occurring on shells or stones on
the sea-shore. One of the cephalic cirrhi in Serj5ula is much
developed, and carries at its extremity a conical plug, or operculum, whereby the mouth of the tube is closed, when the
animal is retracted within it.  The operculum of Serpula has a
more than ordinary interest in the fact that it is the only instance in the Annelida in which calcareous matter is deposited
within the integument. In Sjpirorbis (fig. 58, b) the shelly tube
is coiled into a flat spiral, one side of which is fixed to some
solid object. It is of extremely common occurrence on the
fronds of sea-weed and on other submarine objects.
Equally familiar with Serjpua is Terebella, the animal of
which is included in a tube composed of sand and fragments
of shell, cemented together by a glutinous secretion. In the
Sabellidce the tube is composed of granules of sand or mud. In
Pectinaria the tube is free, membranous, or papyraceous, and
in the form of a reversed cone of considerable length.
ORDER IV. ERRANTIA (Nereidea).-This order comprises
free Annelides,'* which possess setigerous foot-tubercles.  The
respiratory organs are generally in the form of tufts of external branchixe, arranged along the back or the sides of the
body.  They are unisexual, and the young pass through a
metamorphosis. This order includes most of the animals
which are commonly known as Sand-worms and Sea-worms,
together with the familiar Sea-mice.
The integument iS soft, and the body is very distinctly
divided into a great number of rings or segments, each of
which, in the typical forms, possesses the following structure.
The segment consists of two arches, a lower or " ventral arc,"
and an upper or " dorsal arc," with a " foot-tubercle" on each
side.  Each foot-tubercle consists of an upper process, or
" notopodium," and a lower process, or "neuropodium," each
of which carries a tuft of bristles, or " sete," and a species of
tentacle termed the "cirrhus " (fig.. 56).
The anterior extremity of the body is usually so modified
as to be distinctly recognisable as the head, and is provided
X Fritz Muller describes an errant Annelide belonging to the Amphinornidz
as living parasitically within the shell of the common Barnacle (Lepas),
showing that the members of this group may sometimes lose their free habit.




ANNULOSA: ANNELIDA.                  195
with eyes, and with two or more feelers, which are not jointed,
and are, therefore, not comparable with the antennae of Crustacea and Insects. The mouth is placed on the inferior surface of the head, and is often furnished with one or more pairs
of horny jaws, working laterally. The pharynx is muscular,
and forms a sort of proboscis, being provided with special
muscles, by means of which it can be everted and again retracted. In most there is no distinction between stomach and
intestine, and the epithelium of the alimentary canal, like that
of the preceding orders, is ciliated. The perivisceral cavity
is filled with a colourless corpusculated fluid-the " chylaqueous fluid " —which "performs one of the functions of an internal skeleton, acting as the fulcrum or base of resistance to the
cutaneous muscles, the power of voluntary motion being lost
when the fluid is let out."-(Owen.)
The pseudo-hwemal system is well developed, and consists
essentially of a long dorsal vessel, and a similar ventral one,
connected by transverse branches, and furnished at the bases
of the branchiae with pulsating dilatations.  The contained
fluid is mostly red, but is yellow in Aphrodite and Polynoe.
Respiration is carried on by means of a series of external
branchiae or gills, arranged in tufts upon the sides of the body
on its dorsal aspect, along the middle of the body only, or
along its entire length. From the position of the branchiae,
the members of this order are often spoken of as the "Dorsibranchiate-" (or more properly " Notobranchiate ") Annelides.
The "segmental organs," with few exceptions, communicate
with the perivisceral cavity internally, and in certain segments
they are always specialised to act as efferent ducts for the reproductive organs.
In the Sea-mouse (Aphrodite, fig. 60, B), the back is covered
with a double row of membranous imbricated plates, which
are called " elytra," or " squamae," and respiration is effected
by the periodical elevation and depression of these plates,
whereby water is alternately admitted into, and expelled from,
a space beneath them. This space is separated by a membrane
from the perivisceral cavity below, and contains the gills in the
form of small fleshy crests. The pharynx is thick and muscular,
and can be everted like a proboscis, and the intestine has a
number of lateral branched caeca.
The nervous system in the Errantia has its typical form,
consisting of a double gangliated ventral cord, two ganglia of
which are appropriated to each segment.  The prae-cesophageal, or cerebral, ganglia are of large size, and send filaments
to the ocelli and feelers.
10




I96              MANUAL OF ZOOLOGY.
The sexes in the Errantia are in different individuals, and
reproduction is usually sexual, though in some cases gemmation is known to occur. The process of gemmation is carried
on by a single segment, and so long as it continues, the budding individual remains sexually immature, though the young
thus produced develop generative organs.  Thus, there is in
these cases a kind of alternation of generations, or rather an
alternation of generation and gemmation; the oviparous individuals producing eggs from which the gemmiparous individuals are born; these, in their turn, but by a non-sexual process, producing the oviparous individuals.
The embryo usually appears, on its liberation from the ovum,
as a free-swimming, ciliated body, possessing a mouth, intestine,
and anus. The cilia are primarily diffused, but become aggregated so as to form a single median belt, or two bands, one
about each extremity. The head, with its feelers and eyeFig. 59.-" Errant " Annelide. Nereis, showing the " head " with its appendages,
and the setigerous parapodia.
specks, appears at one extremity, whilst the segments of the
body begin to be formed at the other. Each segment is developed in four parts, the two principal ones forming half-rings,
united by shorter side-pieces, from which the setigerous foottubercles are developed. The ciliated band or bands finally
disappears, and new rings are rapidly added by intercalation
between the head and the segments already formed.
Amongst the best known of the Errantia is the common
Lob-worm (Arenicola piscaorum, fig. 60, C), which is used by
fishermen for bait. The Lob-worm lives in deep canals which
it hollows out in the sand of the sea-shore, literally eating its
way as it proceeds, and passing the sand through the alimentary canal, so as to extract from it any nutriment which it may
contain. It possesses a large head, without eyes or jaws, and
with a short proboscis.  There are thirteen pairs of-branchixe,
placed on each side in the middle of the body.
In the Nereid&a, or "Sea-centipedes," the body is greatly




ANNULOSA: ANNELIDA.                    197
elongated, and consists of a great number of similar segments,
with rudimentary branchiwe. The head is distinct, and carries
eyes and feelers, whilst the mouth is furnished with a large
proboscis, and often with two horny jaws (fig. 59). In the
Eunicea the branchiae are usually well developed and of large
size, and the mouth is armed with seven, eight, or nine horny
jaws.  Eunice gigantea attains sometimes a length of over four
feet, and may consist of more than four hundred rings.
DISTRIBUTION OF ANNELIDA IN TIME. -Of the Anne/ida the
only orders which are known to have left any traces of their
existence in past time are the Tubicoia and the Errantia; of
which the former are known by their investing tubes, whilst
B
Fig. 6o.-Errant Annelides. A. Hairy-bait (NeMhthys); B. Sea-mouse (Aphrodite);
C. Lob-worm (A renicola). (After Gosse.)
the latter are only recognised by the tracks which they left
upon ancient sea-bottoms, or by their burrows in sand or mud.
These tracks and burrows of Annelides are found commonly in
rocks of almost all ages from the Cambrian period upwards.
Those tracks which have been caused simply by the passage
of the worm over the surface of the mud are termed by Mr
Salter Hezninthites, whilst the burrows are called Scolites (or
Scolithus).
Tubicolar Annelides are known to occur from the Silurian
Rocks upwards.  The well-known Silurian fossil, Tentaculites,
is generally believed to belong to this order, but it is referred
by M. Barrande to the Pteropoda (Moltusca).  Cornulites and




198                MANUAL OF ZOOLOGY.
7irachyderma, however, are undoubted Silurian Tubicola.  The
Microconchus carbonarius is a little spiral Tubicolar Annelide,
nearly allied to the Spirorbis (fig. 58, b) of our seas, which is
not uncommonly found in strata belonging to the Carboniferous period; and the genus Spirorbis itself is represented
even in the Silurian period.
TABULAR VIEW OF THE ANNELIDA.
Division A. ABRANCHIATA.-No external organs of respiration.
Order I. Hirudinea.-No bristles or foot-tubercles: locomotion by
means of a suctorial disc at one or both extremities. I11. Gen.
Hirudo, Clepsine, Pontobdella.
Order II. Oligocheta.-Locomotion by means of rows of stiff bristles,
or "setfe;" no foot-tubercles.  Ill. Gen. Lumbricus, Nais, Tubijex.
Division B. BRANCHIATA.-Respiratory organs in the form of external
lranchiae.
Order III. Tubicola.-Body protected by a calcareous or arenaceous
tube. Branchioe attached to, or near, the head (Cephalobranchiata).
Ill. Gen. Serpula, Terebella, Sabella.
Order IV. Errantia.-Animal free, with setigerous foot-tubercles.
Branchiae in tufts, attached on the sides of the body, in the middle
of dorsal region only, or along its entire length (Dorsibranchiata).
Ill. Gen. Arenicola (Lob-worm), Nereis (Sea-centipede), Aphrodite
(Sea-mouse).
CLASS III. CHAETOGNATHA (Huxley).-The remaining class
of the Anarthropoda has been recently constituted by Professor
Huxley under the name of Chatfogna/ha, for the reception of
the single genus Sagitta, which had been formerly placed
amongst the Annelida. By Professor Rolleston, however, the
Cheetognatha are placed  in the division Nematelmia of the
Annuloida, in the immediate neighbourhood of the Nematoidea.
The Sagitte are singular marine animals, transparent, and
elongated in form, and usually not more than an inch in
length. The following are the characters ascribed to the class
by Huxley:"The head is provided with several, usually six, sets of
strong, bilaterally symmetrical oral setze, two of which, long
and claw-like, lie at the sides of the mouth; while the other
four sets are short, and lie on that part of the snout which is
produced in front of the oral aperture. The posterior part of
the body is fringed on each side by a delicate striated fin-like
membrane, which seems to be an expansion of the cuticle.  In
some species the body is beset with fine setae. The intestine is
a simple, straight tube, extending from the mouth to the anus;
the latter opens on the ventral surface, just in front of the




ANNULOSA: CHAETOGNATHA.               199
hinder extremity. A single oval ganglion lies in the abdomen,
and sends, forwards and backwards, two pairs of lateral cords.
The lateral cords unite in front of and above the mouth into a
hexagonal ganglion. This gives off two branches which dilate
at their extremities into the spheroidal ganglia, on which the
darkly pigmented imperfect eyes rest. The ovaries, saccular
organs, lie on each side of the intestine and open on either side
of the vent; receptacula seminis are present. Behind the anus,
the cavity of the tapering caudal part of the body is partitioned
into two compartments; on the lateral parietes of these, cellular
masses are developed which become detached, and, floating
freely in the compartment, develop into spermatozoa. These
escape by spout-like lateral ducts, the dilated bases of which
perform the part of vesiculce seminales. The embryos are not
ciliated, and undergo no metamorphosis."-(See Introduction to
the Classification of Animals, p. 52.)
CHAPTER XXX.
ARTHROPODA.
DIVISION II. ARTHROPODA, OR ARTICULATA.-The remaining
members of the sub-kingdom Annulosa are distinguished by
the possession of jointed appendages, articulated to the body; and
they form the second primary division-often called by the
name Articulata. As this name, however, has been employed
in a wider sense than is understood by it here, it is, perhaps,
best to adopt the more modem term Arthropoda.
The members of this division, comprising the Crustacea
(Lobsters, Crabs, &c.), the Arachnida (Spiders and Scorpions),
the Myriapoda (Centipedes), and the Inserfa, are distinguished
as follows:The body (fig. 54) is composed of a series of segments,
arranged along a longitudinal axis; each segment, or " somite,"
occasionally, and some always, being provided with articulated
appendages. Both the segmented body and the articulated
limbs are more or less completely protected by a chitinous
exoskeleton, formed by a hardening of the cuticle.  The
appendages are hollow, and the muscles are prolonged into
their interior. The nervous system in all, at any rate in the
embryonic condition, consists of a double chain of ganglia,
placed along the ventral surface of the body, united by longi



200             MANUAL OF ZOOLOGY.
tudinal commissures, and traversed anteriorly by the cesophagus.
The haemal system, when differentiated, is placed dorsally, and
consists of a contractile cavity, or heart, provided with valvular
apertures, and communicating with a perivisceral cavity, containing corpusculated blood. Respiration is effected by the
general surface of the body, by gills, by pulmonary sacs, or by
tubular involutions of the integument, termed "tracheae." In
no member of the division are vibratile cilia known to be
developed.  According to Professor Huxley, an additional
constant character of the Arthropoda is to be found in the
structure of the head, which is typically composed of six segments, and never contains less than four.
The Arthropoda are divided into four great classes-viz., the
Crustacea, the Arachnida, the Myriapoda, and the Insecta;
which are roughly distinguished as follows:
I. CRUSTACEA. —Respiration by means ofgills, or by thegeneral
surface of the body.  Two pairs of antennae. Locomotive appendages more than eight in number, borne by the segments of the
thorax, and usually of the abdomen also.
2. ARACHNIDA. —Respiration bypulmonary vesicles, by trachece,
or by the general surface of the body. Head and thorax united
into a cephalothorax. Antennea (as such) absent. Legs eight.
Abdomen without articulated appendages.
3. MYRIAPODA.-Respiration by trachece; head distinct; remainder of the body composed of nearly similar somites.  One
pair of antennae. Legs numerous.
4. INSECTA. —Respiration by trachece.    ead, thorax, and
abdomen distinct.  One pair of antennae.  Three pairs of legs,
borne on the thorax. Abdomen destitute of limbs. Generally two
pairs of wings on the thorax.
CHAPTER XXXI.
CR US TA CEA.
CLASS I. CRUSTACEA.-The members of this class are commonly known as Crabs, Lobsters, Shrimps, King-crabs, Barnacles, Acorn-shells, &c. They are nearly allied to the succeeding order of the Arachnida (Spiders and Scorpions); but
may usually be distinguished by the possession of articulated
appendages upon the abdominal segments, by the possession
of two pairs of antennae, and by the presence of branchie.




ANNULOSA: CRUSTACEA.                 201
"In the Crustacea the body is distinguishable into a variable
number of'somites,' or definite segments, each of which may
be, and some of which always are, provided with a single pair
of articulated appendages.... In most Crustacea, and
probably in all, one or more pairs of appendages are so modified as to subserve manducation. A pair of ganglia is primitively developed in each somite, and the gullet passes between
two successive pairs of ganglia, as in the Annelida.
" No trace of a water-vascular system, nor of any vascular
system similar -to that of the Annelida, is to be found in any
Crustacean. All Cruslacea which possess definite respiratory
organs have branchime or outward processes of the wall of the
body, adapted for respiring air by means of water; the terrestrial Isopoda, some of which exhibit a curious rudimentary
representation of a tracheal system, forming no real exception
to this rule. When they are provided with a circulatory organ,
it is situated on the opposite side of the alimentary canal to
the principal chain of ganglia of the nervous system; and communicates by valvular apertures with the surrounding venous
sinus —the so-called'pericardium.' "-(Huxley.)
In addition to these characters, the body in the Crustacea
is always protected by a chitinous or sub-calcareous exoskeleton, or " crust," and the number of pairs of articulated limbs
is generally from five to seven. They all pass through a series
of metamorphoses before attaining their adult condition, and
every part that is found in an embryonic form, even though
only temporarily developed, may be represented in a permanent
condition in some member of a lower order.,
The classification of the Crustacea is extremely complicated,
and hardly any two writers adhere to the same arrangement.
The tabular view which follows embodies the arrangement
which appears to be most generally adopted, and the diagnostic
characters of each order will be briefly given, a more detailed
description being reserved for the more important divisions of
the class. Before proceeding further, however, it will be as well
to give a description of the morphology of a typical Crustacean,
selecting the Lobster as being as good an example as any.
The body of a typical Crustacean may be divided into three
regions-a /ead, a thorax, and an abdomen, each of which is
composed of a certain number of somites, though opinions differ
both as to the number of segments in each region, and as
to their number collectively. By the majority of writers the
body is looked upon as being typically composed of twenty-one
segments, of which seven belong, to the head, seven to the
thorax, and seven to the abdomen. In many Crustacea, how



202              MANUAL OF ZOOLOGY.
ever, the segments of the head and thorax are welded together
into a single mass, called the " cephalothorax;" in which case
the body shows only two distinct divisions, of which the cephalothorax claims fourteen segments, whilst the remaining seven
are allotted to the abdomen. By Professor Huxley, on the
other hand, the terminal joint of the abdomen, termed the
"telson," is regarded as an appendage, and not as a somite.
Upon this view, the body of a typical Crustacean will consist
of twenty segments only. Professor Huxley,'further, differs
from the above-mentioned view in the allotment of the somites,
and he divides the body into six cephalic, eight thoracic, and
six abdominal somites.1 Fritz Miiller and Claus deny that the
eyes are limbs, or that there is an ocular segment. The telson,
on the other hand, is regarded by the former as a true somite,
chiefly because the intestine usually opens in this piece.
Whilst the normal number of segments in the body of any
Crustacean may thus be regarded as being twenty-one, or
twenty, there occur cases in which this number is exceeded,
and others in which the number of somites is apparently less.
In these latter cases, however, the apparent diminution in the
number of segments is really due to some having been fused
together, as is shown by the number of appendages, since each
pair of appendages indicates a separate somite. In other cases,
however, in which the number of somites is really less than the
normal, this is due to an arrest of development. According to
Milne-Edwards:"In the embryo these segments are formed in succession
from before backwards, so that, when their evolution is checked,
the later, rather than the earlier, rings are those which are
wanting; and, in fact, it is generally easy to see in those specimens of full-grown Crustaceous animals whose bodies present
fewer than twenty-one segments, that the anomaly depends on
the absence of a certain number of the most posterior rings of
the body." According to Dana, however, the abortion of
segments, with their appendages, almost always takes place at
the posterior end of the cephalothorax.
In no single example can a general view be obtained of the
different segments and their appendages in the Crustacea.
"Indeed, the only segment that may be said:to be persistent,
is that which supports the mandibles, for the eyes may be
* In reality the five hindmost segments of the eight somites here allotted
to the thorax, should alone be regarded as constituting the abdomen proper,
-that is, the region corresponding to the " abdomen " of insects and Arachnida. The six somites allotted above to the abdomen belong to what is
strictly called the "ipost-abdomen" of the Crustacea.




ANN ULOSA: CRUSTACEA.                     203
wanting, and the antenne, though less liable to changes than
the remaining appendages, are nevertheless subject to very
extraordinary modifications, and have to perform functions
equally various.  Being essentially and typically organs of
touch, hearing, and perhaps of smell, in the highest Decapods,
they become converted into burrowing organs in the Scyllaridae,
organs of prehension in the Merostomata, claspers for the male
in the Cyclaopoidea, and organs of attachment in the Cirripedia.
Not to multiply instances, we have presented to us in the
Crustacea.probably the best zoological illustration of a class,
constructed on a common type, retaining its general characteristics, but capable of endless modification of its parts, so as
to suit the extreme requirements of every separate species."(H. Woodward.)
Taking the common Lobster (fig. 74) as a good and readily
obtainable type of the Crustacea, the body is at once seen to
be composed of two parts, familiarly called the " head" and
the " tail," the latter being jointed and flexible.  The so-called
"head" is really composed of both the head, properly so
called, and the thorax, which have coalesced so as to form
a single mass, technically called the "cephalothorax." The
so-called "tail," on the other hand, is truly the "abdomen."
The various appendages of the animal are arranged along the
lower surface of the body, and consist of the feelers, jaws,
claws, legs, &c. The entire body, with the articulated appendages, is enclosed in a strong chitinous "shell," or exoskeleton, and the cephalothorax is covered by a great cephalic
shield or plate, which is termed the "carapace."
Each segment of the body may                  
be regarded as essentially composed
of a convex upper plate, termed the
"tergum," which is closed below by D 
a flatter plate, called the "sternum,"  
the line where the two unite being                      f
produced downwards and outwards,                s   s
into a plate, which is called the   Vig. 6I.-Theoretical figure illustrating the composition of the
pleuron," or "pleura" (fig. 62, 2).    tegumentary skeleton of the
Crustacea (after Milne - Ed -
Strictly speaking, the composition of the   aTergds). DDorsal p arc; e 
Tergal pieces; e e Epimeral
typical somite is considerably more complex,    pieces; V Ventral arc; s s
each of the primary arcs of the somite being    Sternal pieces; ff Episternal
really composed of four pieces. The ter-   pieces;fi Ai Insertion of the
gal arc is composed of two central pieces,
one on each side of the middle line of the body, united together, and constituting the "tergum" proper. The superior arc is completed by two
lateral pieces, one on each side of the tergum, which are termed the
"epimera."  In like manner the ventral or sternal arc is composed of




204               MANUAL OF ZOOLOGY.
a central plate, composed of two pieces united together in the middle line,
and constituting the "sternum" proper; the arc being completed by two
lateral pieces, termed the " episterna." These plates are usually more or
less completely anchylosed together, and the true structure of the somite
in these cases is often shown by what are called "apodemata." These
are septa which proceed inwards from the internal surface of the somite,
penetrating more or less deeply between the various organs enclosed by
the ring, and always proceeding from the line of junction of the different
pieces of the segment (fig. 6 ).
It must be borne in mind that though the so-called "head"
-that is to say, the " cephalothorax "-of the Lobster is produced by an amalgamation of the various somites of the head
and thorax, this is not the case with the great shield which
covers this portion of the body. This shield-the so-called
"cephalic buckler," or " carapace."-is not produced by the
union of the tergal arcs of the various cephalic and thoracic
segments, as would at first sight appear to be the case. On
the contrary, the "carapace" in the higher Crusacea is produced by an enormous development of the tergal pieces, or of
the "epimera" of one or two of the cephalic segments: the
tergal arcs of the remaining somites being overlapped by the
carapace and remaining undeveloped.
Examining the somites from behind forwards (for simplicity's sake), the last segment comes to be first described. This
is the so-called "telson," which forms the last articulation of
the abdomen, and never bears any appendages.  For this
reason, many authorities do not regard it as a somite, properly
speaking, but simply as an azygos appendage-that is to say,
as an appendage without a fellow. In the next segment (the
last but one, or the last, of the abdomen, according to the view
which is taken of the " telson "), there is a pair of natatory appendages, called " swimmerets."  Each swimmeret (fig. 62, 2)
consists of a basal joint, which articulates with the sternum,
and is called the "protopodite" or propodite, and of two
diverging joints, which are attached to the former; the outer
of these being called the "exopodite," and the inner the " endopodite."  In this particular segment, the exopodite and
endopodite are greatly expanded, so as to form powerful paddles, and the exopodite is divided into two by a transverse
joint. In the succeeding somites of the abdomen-with tlte
exception of the first, in which there is some modificationthe appendages are in the form of swimmerets, essentially the
same as those attached to the penultimate segment, and differing only in the fact, that the exopodite and endopodite are
much narrower, and the former is undivided (fig. 62, 2).  The




ANNULOSA: CRUSTACEA.                              205
last thoracic somite-immediately in front of the abdomencarries a pair of the walking or ambulatory legs, each consisting of a short basal piece, or " propodite," and of a long jointed
"endopodite," the  "exopodite"  not being developed.  The
b
cab
aa
Fig. 62.-Morphology of Lobster.  I. Lobster with all the appendages, except the
terminal swimmerets, removed, and the abdominal somites separated from one
another. ca Carapace; t Telson.  2. The third abdominal somite separated.  t
Tergum; s Sternum; f Pleuron; a Protopodite; b Exopodite; c Endopodite.  3.
One of the last pair of foot-jaws or maxillipedes. e Epipodite; g Gill; the other
letters as before.
next thoracic segment carries another pair of ambulatory limbs,
quite similar to the last, except for the fact that the protopodite bears a process which serves to keep the gills apart, and




206             MANUAL OF ZOOLOGY.
is termed the " epipodite." The succeeding segment supports
a pair of limbs similar to the last in all respects, except that
its extremities, instead of being simply pointed, are converted
into nipping claws, or "chelae."  The next segment of the
thorax carries a pair of chelate limbs, just like the preceding,
and the next is furnished with appendages, which are essentially the same in structure, but are much larger, constituting
the great claws. The next two segments of the thorax, and
the segment in front of these (by some looked upon as belonging to the head, by others as referable to the thorax), bear
each a pair of modified limbs, which are termed " maxillipedes,"
or "foot-jaws."  These are simply limbs with the ordinary
structure of protopodite, exopodite, endopodite, and epipodite,
but modified to serve as instruments of mastication, the hindmost pair being less altered than the two anterior pairs (fig. 62,
3). The next two somites carry appendages, which are in the
form of jaws, and are termed respectively the first and second
pairs of " maxillae." Each consists of the parts aforementioned,
but the epipodite of the first pair of maxillae is rudimentary,
whilst that of the second pair is large, and is shaped like a
spoon. It is termed the " scaphognathite," and its function is
to cause a current of water to traverse the gill-chamber by constantly baling water out of it.  The next segment carries the
biting jaws, or " mandibles;" each of which consists of a large
protopodite, and a small endopodite, which is termed the
"palp," whilst the exopodite is undeveloped.  The aperture
of the mouth is situated between the bases of the mandibles,
bounded behind by a forked process, called the " labium," or
"metastoma," and in front by a single plate, called the "labrum" (upper lip).'The next segment bears the long antennae,
or feelers (fig. 74, ga), each consisting of a short protopodite,
and a long, jointed, and segmented endopodite, with a very
rudimentary exopodite. In front of the great antennae are the
next pair of appendages, termed the "antennules," or smaller
antennae (fig. 74, a), each composed of a protopodite, and a
segmented endopodite and exopodite, which are nearly of equal
size. Finally, attached to the first segment of the head are the
eyes, each of which is borne upon an eye-stalk formed by the
protopodite. The gill-chamber is formed by a great prolongation downwards of the pleura of the thoracic segments, and
the gills are attached to the bases of the legs.
As regards the digestive system of the Crustacea, the alimentary canal is, with few exceptions, continued straight from
the mouth to the aperture of the anus. There are no salivary
glands, but a large and well-developed liver is usually present.




ANNULOSA: CRUSTACEA.                     207
A heart is generally, but not always, present. In most of the
lower forms it is a long vasiform tube, very like the "dorsal
vessel" of Insects.  The exact course of the circulation has
been differently stated by different writers, but the following
appear to be the facts of the case: In some of the lower forms
(e.g., Copepoda) there are no arterial vessels, and the venous
blood returned from the body is collected into a venous sinus
-the so-called " pericardium," which surrounds the heart and
opens into it by valvular apertures. In the higher forms, the
heart gives off a number of arteries by which the blood is
driven to all parts of the body and to the gills. The arteries
do not terminate in a system of capillary vessels, but in a
series of irregular lacunxe occupying all the interstices between
the different organs of the body. From this interstitial lacunar
system arise the venous trunks, which are generally dilated
into more or less extensive sinuses. Whether the whole of
the venous blood is submitted to the action of the gills, or
whether the blood sent to the gills is derived mainly from the
heart, is a matter of question; but the former is the more
probable view.  Be this as it may, the blood is invariably
returned to a large venous sinus which surrounds the heart,
and opens into it by a number of valvular apertures.  It
follows from this description, that the heart of the Crustacea
is mainly, if not altogether, a systemic heart, being concerned
chiefly, if not entirely, in driving the aerated blood to all parts
of the body.
Distinct respiratory and circulatory organs may be altogether
wanting; but, as a rule, distinct branchiae are present.  The
exact form and structure of the gills differ in different cases,
but their leading modifications will be alluded to in treating of
the different orders.
TABULAR VIEW OF THE DIVISIONS OF THE CRUSTACEA.
Sub-class I. EPIZOA (Haustellata).
Order i. Ichthyop/hthira.,, 2. Rhizocephala.
Sub-class 11. CIRRIPEDIA.
( Balanidae.
Order 3. Thoracica.      Verrucida.
Lepadide.,,  4. Abdominalia.,, 5. Apoda.




208             MANUAL OF ZOOLOGY.
Sub-class III. ENTOMOSTRACA.
Order 6. Osraod.         Leon Lsryroa.,,  7. Copepoda.            n, Lophyropoda.
7. Copeoda.,,  8. Cladocera.
9. Phzyllopoda.     Legion, Branchiopoda.,, Io. Trilobita.
i I. Merostomafa.
Sub-class IV. MALACOSTRACA.
Division A. EDRIOPHTHALMATA.
Order 12. Lcemnodinpoda.,,    I3- Jsopoda.
14. Amphipoda.
Division B. PODOPHTHALMATA.
Order 15. Stomapoda.,,  I6. Decapoda.
Tribe a. Macrura.,, b. Anomura.,, c. Brachyura.
CHAPTER XXXII.
EPIZOA  AND  CIRRIPEDIA.
SUB-CLASS I. EPIZOA (Haustellata).-The members of this subclass of the Crustacea are in the adult state parasitic upon the
bodies of fishes, and are usually deformed; but in the young
condition they are locomotive, and are furnished with antennae
and eyes. The mouth is suctorial, and the limbs are terminated
by suckers, hooks, or bristles.  There are no differentiated
respiratory organs, but respiration is performed by the surface
of the body. The males are rudimentary, and are much smaller
than the females, which are useally furnished with external
ovisacs. The Epizoa are closely allied to the Copepoda, and
may, indeed, be regarded as parasitic Copepods, having the
mouth modified so as to form a suctorial tube or beak, resulting from the elongation of the labrum and labium. Within
this are almost always two stylets or lancet-shaped mandibles,
used in piercing. The feet are often deformed by age, or




ANNULOSA: CRUSTACEA.                  209
wanting, but are primitively natatory. Not only does their developmental history bear out this view, but cases are known
(in some Lern(ea) in which the males do not undergo retrograde
metamorphosis, but remain permanently in the condition of
free Copepods.
This division includes the single order Ichthyoph/lhira, the
characters of which are therefore the same as those of the subclass, comprising various parasites upon fishes belonging to the
genera Lerncea, Achtheres, Peniculus, &c.
ORDER I. ICHTHYOPHTHIRA.-The members of this order
are attached in the adult condition to the skin, eyes, or gills of
fishes, and when mature possess an elongated body, having a
more or less distinct head, and in the females usually a pair of
long, cylindrical ovisacs, depending from the extremity of the
abdomen. Some adhere by a suctorial mouth, or by cephalic
processes (Cephaluna); others are attached by a suctorial disc,
developed at the extremities of the last pair of thoracic limbs,
which are united together (Brachiuna)); whilst in others (Onchuna) attachment is effected by hooks at the free extremities of
the first pair of thoracic limbs.-(Owen.)
The males are usually not attached, but adhere to the females, of which, from their much smaller size, they appear to
be mere parasites.  The chief anatomical peculiarities of the
female are the following: —The head is provided usually with a
pair of jointed antennae, and the body is divided into a cephalothorax and abdomen. The alimentary canal consists of a
mouth, gullet, and intestine, terminating posteriorly in a distinct
anus. The nervous system consists of a double ventral cord.
The embryo (fig. 63, a) is free-swimming, and is provided
with visual organs and locomotive appendages. The two
Fig. 63.-Ichthyophthira. a Free-swimming larva of Achtheresfiercarum, in its first
stage; b Adult male of the same. Enlarged. (After Owen.)
sexes are now alike, and the conversion of the active embryo,
or larva, into the swollen and deformed adult, must be regarded
as an instance of "retrograde metamorphosis." In Achtheres




210              MAN UAL OF ZOOLOGY.
percarum (fig. 63), the primitive form of the young is a " Nauplius;"~ but a wholly different larva, resembling the Cyclops in
shape, but with fewer limbs and somites, is prepared within the
Nauplius-skin, and is liberated by the rupture of the same.
ORDER  II. RHIZOCEPHALA.-The name Rhizocephala has
been proposed for another group of Crustacea, which are fixed,
parasitic, and greatly deformed when adult; but which are locomotive when young, and which are most nearly allied to the
Cirripedia. The larvae are " Naupliiform," with an ovate unsegmented body, an unpaired median eye, and a dorsal shield or
carapace. The abdomen terminates in a movable caudal fork,
and there is neither mouth nor alimentary canal. In their
second stage (as so-called "pupae"), the young of the RRhizocephala are enclosed in a bivalve shell, the foremost pair of
limbs constitute peculiar organs of adhesion (" prehensile antennae" of Darwin), the two following pairs of limbs are cast off,
and six pairs of powerful biramose natatory feet are formed on
the abdomen.  There is still no mouth.  The "pupae" now
attach themselves to the abdomen of Crabs, Porcellance, and
Hermit-crabs; they remain astomatous; "they lose all their
limbs completely, and appear as sausage-like, sack-shaped, or
discoidal excrescences of their host, filled with ova; from the
point of attachment closed tubes, ramified like roots, sink into
the interior of the host, twisting round its intestine, or becoming diffused amongst the sac-like tubes of its liver. The only
manifestations of life which persist in these non plus ultras in
the series of retrogressively metamorphosed Crustacea are
powerful contractions of the roots, and an alternate expansion
and contraction of the body, in consequence of which water
flows into the brood-cavity, and is again expelled through a
wide orifice."-(Fritz Muller.)  The branched roots of the
Rhizocephala appear to be the homologues of the "cementducts" of the Cirritpedia, and to be, therefore, really the
antennae.
SUB-CLASS II. CIRRIPEDIA.-This sub-class includes, amongst
others, the common Acorn-shells and the Barnacles or Goosemussels. All the Cirripedia are distinguished by the fact, that
in the adult condition they are permanently fixed to some
solid object by the anterior extremity of the greatly metamorphosed head; the first three cephalic segments being much
developed, and enclosing the rest of the body. The larva is
* The name of "Nauplius" was given by 0. F. Muiler to the unsegmented ovate larva of the lower Crustacea, with a median frontal eye, but
without a true carapace; and this name may be conveniently employed to
designate all the larval forms which agree in these characters.




ANNULOSA: CRUSTACEA.                      211
free and locomotive, and the subsequent attachment, and conversion into the fixed adult, is effected by means of a peculiar
secretion, or cement, which is discharged through the antennae
of the larva, and is produced by a special cement-gland, which
is really a portion of the ovary.  In the Cirripedia, therefore,
the head of the adult is permanently fixed to some solid object,
and the visceral cavity is protected by an articulated calcareous
shell, or by a coriaceous envelope. The posterior extremity
of the animal is free, and can be protruded at will through the
orifice of the shell. This extremity consists of the abdomen,
and of six pairs of forked, ciliated limbs, which are attached to
the thorax, and serve to provide the animal with food. The
two more important types of the Cirrizpedia are the Acornshells (Balanidc) and the Barnacles (Lepadid&). In the former
the animal is sessile, the larval antennae, through which the
cement exudes, being imbedded in the centre of the membranous or calcareous "basis" of the shell.  In the latter the
animal is stalked, and consists of a "peduncle " and a " capitulum." The peduncle consists of the anterior extremity of
the body, with the larval antennae usually cemented to some
foreign body. The capitulum is supported upon the peduncle,
and consists of a case composed of several calcareous plates,
united by a membrane, enclosing the remainder of the animal.
Before giving a more detailed description of this singular
and important sub-class, the following definition, as given by
Owen, may be advantageously appended:" Body, chitinous, or chitino-testaceous, sub-articulated, mostly symmetrical, with aborted antennae and eyes. Mouth, prominent, composed of a
labrum, palpi, two mandibles, and two pairs of maxillae. Thorax, attached
to the sternal internal surface of the carapace, with six pairs of multiarticulate, biramous, setigerous limbs.  Abdomen, rudimentary.  Vascular
system diffused; white blood. Branchiae, when present, attached to the
inferior lateral part of the surface. Most are hermaphrodite; a few have
minute, rudimentary, male individuals, parasitically attached to the females.
Penis, proboscidiform, multiarticulate, attached to the hinder end of the
abdomen. No oviducts. Metamorphosis and metagenesis, resulting in a
permanent parasitic attachment of the fully-developed female or hermaphrodite individual."
As regards the development of the Cirripedia, the larva is at
first a "Nauplius," with an unsegmented pyriform  body, a
median eye, and a dorsal shield or buckler. The abdomen is
produced beneath the anus into a long forked caudal appenage, and there is a long spine over the anus. A mouth, intestine, and vent are present. After several moults the young
Nauplii become "pupae" (fig. 64).   The dorsal shield is
folded so as to form a bivalve shell; the anterior limbs (anten



212              MANUAL OF ZOOLOGY.
nae) are transformed into prehensile organs; the two following
pairs of limbs are cast off; and six pairs of strong, biramose,
natatory feet are developed upon the abdomen. A pair of
composite eyes are present, but there is no mouth. Finally, the
pupa fix themselves by the prehensile antennae to rocks, driftwood, ships, Sponges, Cetaceans, Turtles, Crustaceans, or even
C            - a
Fig. 64.-Locomotive "pupa" of Balanus. a Eye; b caudal bristles;
c Setigerous limbs.
Jelly-fish. The prehensile antennae are glued down permanently by the secretion of a peculiar cement-gland. The carapace becomes, as a rule, the seat of definite calcifications, by
which it is converted into a multivalve calcareous " test; " the
mouth is developed, and the six pairs of natatory feet are converted into long jointed " cirri," by which food is conveyed to
the mouth. " The' cement-ducts' can be traced as far as the
third or'disc-segment' of the antennae.  There the cement
seems to transude and fasten down the disc; soon both antennae are surrounded by a common border of cement, which
gradually increases in extent after the metamorphosis. In the
Lepas fascicularis the cement is poured forth in sufficient
quantities to form, itself, the substance to which the peduncle
of the adult barnacle adheres, and for a cluster of which barnacles it constitutes a central vesicular fioat."-(Owen.) The
cement-gland, as shown by Darwin, is " part of, and continuous with, the branching ovaria," and the' cement-ducts open
through the prehensile antennae.
The form of the adult, as already said, differs considerably,
but the two most important types are those presented respectively by the Sessile and by the Pedunculated Cirrizedia.
In the common Acorn-shells (Balani, fig. 65, a) the anterior
portion of the head is not elongated, but is fixed to the centre
of a basal, membranous, or shelly plate, termed the " basis,"
which adheres by its external surface to some solid body.
Above the basis rises a more or less limpet-shaped, or conical,
shell, which is open at the top, but is capable of being completely closed by a pyramidal lid, or " operculum."  Both the




ANNULOSA: CRUSTACEA.                     213
shell itself and the operculum are composed of calcareous
plates usually differing from one another in shape, and distinguished by special names. Within the shell the animal is
fixed, head downwards. The thoracic segments, six in number, bear six pairs of limbs, each of which consists of a jointed
protopodite and a much segmented exopodite and endopodite, both of which are ciliated, and constitute the so-called
"cirri," from which the name of the sub-class is derived.
These twenty-four cirri-the "glass hand " of the Balanusare in incessant action, being protruded from the opening of
the shell, and again retracted within it, constantly producing
currents of water, and thus bringing food to the animal. There
are-no specialised respiratory organs in the family of the Balanid&. Balani sometimes attain a very considerable size, and
Balanuspsittacus is largely eaten on the coast of Chili.
In the Barnacles (LepadidEc, fig. 65, b) the anterior extremity of the animal'is enormously elongated, forming with
a
Fig. 65.-Morphology of Cirripedia. a Sessile Cirripede or Balanoid, Balanus sulcatus.
b Pedunculate Cirripede or Lepadoid, Le.as anatifera.
the prehensile antennae, the cement-ducts, and their' exudation, a long stalk or peduncle, whereby the animal is attached
to some solid object. At its free extremity the peduncle bears
the " capitulum," which corresponds to the shell of the Balanoids, and is composed of various calcareous plates, united
together by a membrane, moved upon one another by appropriate muscles, and protecting in their interior the body of the
animal with its appendages. The thorax and limbs resemble
those of the Balanus; but "slender appendages, which from
their position and connections are homologous with the
branchiae of the higher Crustacea, are attached to, or near to,
the bases of a greater or less number of the thoracic feet, and
extend in an opposite direction outside the visceral sac."(Owen.)
All the Balanidax are hermaphrodite, and this is also the




214               MANUAL OF ZOOLOGY.
case with most of the LeZpadi&e, but some  extraordinary
exceptions occur in this latter order.  Thus, in some species
of Scalpellum the individual forming the ordinary shell is
female, and each female has two males lodged in transverse
depressions within the shell.  These males "are very singular
bodies; they are sac-formed, with four bead-like, rudimental
valves at their upper ends; they have a conspicuous internal
eye; they are absolutely destitute of a mouth, or stomach, or
anus; the cirri are rudimental and furnished with straight
spines, serving apparently to protect the entrance of the sac;
the whole animal is attached like the ordinary Cirripede, first
by the prehensile antennae, and afterwards by the cementing
substance. The whole animal may be said to consist of one
great sperm-receptacle, charged with spermatozoa; as soon as
these are discharged, the animal dies."
"A  far more singular fact remains to be told; Scalpel/lum
vulgare is, like ordinary Cirripedes, hermaphrodite, but the
male organs are somewhat less developed than is usual; and,
as if in compensation, several shortlived males are almost
invariably attached to the occludent margin of both scuta....
I have called these beings comtlpemental males, to signify that
they are complemental to an hermaphrodite, and that they do
not pair like ordinary males with simple females." —(Darwin.)
DIVISIONS OF CIRRIPEDIA.-(AFTER DARWIN.)
ORDER I. THORACICA.
Carapace, either a capitulum on a pedicle, or an operculated shell with
a basis. Body, formed of six thoracic segments, generally furnished with
six pairs of limbs; abdomen rudimentary, but often bearing caudal appendages. Mouth, with labrum not capable of independent movements.
Larva, firstly one-eyed, with three pairs of legs; lastly two-eyed, with six
pairs of Pegs.
Fam. I. Balanid&c.
Sessile, without a peduncle; scuta and terga (forming the operculum) provided with depressor muscles; the rest of the valves
immovably united together.
Fam. 2. Verrucide.
Sessile.  Shell asymmetrical, with scuta and terga, which are
movable, but not furnished with a depressor muscle.
Fam. 3. Lepadida.
Pedunculated. Peduncle flexible, provided with muscles. Scuta
and terga, when present, not furnished with a depressor muscle.
Other valves, when present, not united into a single immovable
case.
ORDER II. ABDOMINALIA.
Carapace flask-shaped; body Iormed of one cephalic, seven thoracic,
and three abdominal segments, the latter bearing three pairs of cirri, but
the thoracic segments being without limbs.  Mouth, with the labrum
greatly produced. and caDable of independent movements. Larva, firstly




ANNULOSA: CRUSTACEA.                  215
egg-shaped, without external limbs, or an eye; lastly binocular, without
thoracic limbs, but with abdominal appendages.
Genus. Cryptophtialus.
ORDER' III. APODA.
Caragpace, reduced to two separate threads, serving for attachment.
Body consisting of one cephalic, seven thoracic, and three abdominal segments, all destitute of cirri. Mouth suctorial.
Genus. Proteolepas.
CHAPTER  XXXIII.
SUB-CLASS ENTOMOSTRA CA.
SUB-CLASS III. ENTOMOSTRACA.- The term  Entomostraca
has been variously employed, and few authorities include
exactly the same groups of the Crustacea under this name.
By most the division is simply defined as including all those
Crustacea in which the segments of the thorax and abdomen,
taken together, are more or fewer than fourteen in numberthe parasitic Epizoa and the Cirripedia being excluded.  By
Professor Rupert Jones the following definition of the Entomosiraca has been given:"Animal aquatic, covered with a shell, or carapace, of a
horny consistency, formed of one or more pieces, in some
genera resembling a cuirass or buckler, and in others a bivalve
shell, which completely or in great part envelops the body
and limbs of the animal. In other genera the animal is invested
with a multivalve carapace, like jointed plate-armour; the
branchiae are attached either to the feet or to the organs of
mastication; the limbs are jointed, and more or less setiferous.
The animals, for the most part, undergo a regular moulting
or change of shell, as they grow; in some cases this amounts
to a species of transformation."
The Entomostraca are divided into two great divisions, or
"legions," the Lophyropoda and the Branchiopoda, with which
the order AMerostomata may be conveniently considered.
DIviSION A. LOPHYROPODA. —The members of this division
possess few branchiae, and these are attached to the appendages of the mouth. The feet are few in number, and mainly
subserve locomotion; the carapace is in the form either of a
shield protecting the cephalothorax, or of a bivalve shell
enclosing the entire body. The mouth is not suctorial, but is
furnished with organs of mastication.




216              MANUAL OF ZOOLOGY.
This division comprises the  two orders Ostracoda and
Copepoda.
ORDER I. OSTRACODA.-Small Crustaceans having the entire
body enclosed in a shell or carapace, which is composed of two
valves united along the back by a membrane. The branchiie
are attached to the posterior jaws, and there are only two or
three pairs of feet, which subserve locomotion, but are not
adapted for swimming. A distinct heart is sometimes present
(Cypridina), but is more usually wanting (Cypris and Cyt/ere).
Little is known of the development of the Ostracoda, but the
young of Cypris are said to be "shell-bearing Nauplius forms"
(Claus), possessing only the three anterior pairs of limbs, but
protected by a bivalve shell. As in other Nauplii, the third
pair of limbs, though now locomotive, are ultimately transformed
into the mandibles. They pass through several stages, with
complete moults, before arriving at sexual maturity.  The
Cytherides, on the other hand, have at birth the two pairs of
antennae and two pairs of jaws, with three pairs of rudimentary
abdominal limbs.
The order includes the Cyprides (fig. 66, a), which are of
almost universal occurrence in fresh water.  The common
Fig. 66.-Fresh-water Entomostraca. a Cyiris tris-striata;.b DaitIznia
iuliex; c Cyclops quadricornis.
Cypris is completely protected from its enemies by a bivalve
carapace, which it can open and shut at will, and out of which
it can protrude its feet. Locomotion is mainly effected by
means of a pair of caudal appendages. The Cypris is extremely prolific, and a single impregnation appears to last the
female for its entire lifetime. It appears, also, that the young
females, produced in this way, are capable for some generations
of producing fresh individuals without the influence of a male
(parthenogenesis).




ANNULOSA: CRUSTACEA.                 2I7
ORDER II. COPEPODA.-Small Crustaceans, having the head
and thorax covered by a carapace, and furnished with five
pairs of natatory feet. Usually there are two caudal locomotive appendages. A distinct heart is sometimes absent (as in
the Cyclopide), but is sometimes present. Both marine and
fresh-water Copepods are known.
The larvae of the Copepods are Naupliiform, with unpaired
eyes, three pairs of limbs (the future antennae and mandibles),
and two terminal setae. Next the maxillam are produced, and
then three other pairs of limbs (the foot-jaws and the two front
pairs of natatory feet). At the next moult, the larva assumes
the Cyclops form, but has at first much fewer limbs and somites.
In the Cyclops (fig. 66, c), which is one of the commonest of
the "Water-fleas," the cephalothorax is protected superiorly by
a carapace, and the abdominal somites are conspicuous. In
front of the head is situated a single large eye, behind which
are the great antennae and the antennules. The feet are five
pairs in number, each consisting of a protopodite and a segmented exopodite and endopodite, usually furnished with hairs
and.forming an efficient swimming apparatus. The young
pass through a metamorphosis, and are not capable of reproducing the species until after the third moult or change of
skin. The female Cyclops carries externally two ovisacs, in
which the ova remain till they are hatched. A single congress
with the male is apparently sufficient to fertilise the female
for life.
The Copepoda, or Oar-footed Crustaceans, are all of small
size, and are of common occurrence in fresh water in all parts
of Europe.  By good authorities the Ichthyophthira are regarded as merely Copepoda peculiarly modified to suit a life of
parasitism.
DIVISION B. BRANCHIOPODA.-The Crustaceans included in
this division have many branchiae, and these are attached
to the legs, which are often numerous, and are formed for
swimming. In other cases the legs themselves are flattened
out so as to form branchiae. The body is either naked, or is
protected by a carapace, which may enclose either the entire
body, or the head and thorax only. The mouth is provided
with organs of mastication.
The Branchiopoda comprise the Cladocera, the P2hyllopoda,
and probably the lrDilobita, though this order departs in many
respects from the above definition. The Merostomala may
be considered along with these, though these, too, are in many
respects peculiar.
ORDER I. CLADOCERA. -The members of this order are




218              MANUAL OF ZOOLOGY.
small Crustaceans, which have a distinct head, and have the
whole of the remainder of the body enclosed within a bivalve
carapace, similar to that of the Ostracoda. The feet are few
in number (usually four, five, or six pairs), and are mostly
respiratory, carrying the branchiae.  Two pairs of antennae are
present, the larger pair being of large size, branched, and
acting as natatory organs. The Cladocera quit the egg with the
full number of limbs proper to the adult.
In the Daphnia pulex (fig. 66, b), or'branched-horned
Water-flea," which occurs commonly in our ponds, the, body
is enclosed in a bivalve shell, which is not furnished with a
hinge posteriorly, and which opens anteriorly for the protrusion
of the feet. The head is distinct, not enclosed in the carapace, and carrying a single eye. The mouth is situated on the
under surface of the head, and is provided with two mandibles
and a pair of maxillae. The gills are in the form of plates,
attached to the five pairs of thoracic legs. The males are
very few in number, compared with the females, and a single
congress is all that is required to fertilise the female for life.
Not only is this the case, but the young females produced from
the original fecundated female appear to be able to bring forth
young without having access to a male. In this way the influence of a single fecundation appears to be transmitted through
several generations. Two kinds of eggs occur in Dajphnia.
In the first of these, or " summer eggs," the ova (from ten to
fifty in number) are deposited in an open space between the
valves, and are retained there till the young are ready to be
hatched. In the second of these, or "winter eggs," the ova
(generally two in number) are placed in a peculiar receptacle,
which is formed on the back of the carapace, and is called the
" ephippium" or saddle. After a time the ephippium is cast
off, and floats about till spring, when its contained eggs are
hatched by the warmer temperature of the water.
ORDER II. PHYLLOPODA.-Crustacea, mostly of small size,
the carapace protecting the head and thorax, or the body
entirely naked. Feet numerous, never less than eight pairs,
mostly foliaceous or leaf-like, branchial in function. The eyes
sometimes confluent, sometimes distinct and sub-pedunculate.
There are two horny mandibles without palps, and the first pair
of feet are oar-like, with setiform terminal appendages. The
remaining feet are branchial, and adapted for swimming. The
Phyllopods undergo a metamorphosis, the youngest forms being
"Nauplii."  In Neialia, however, which is the only marine
Phyllopod, "Zoea-stages " are superadded as well.
The Phyflopoda are chiefly interesting from their affinity to




ANNULOSA: CRUSTACEA.                  219
the extinct Trilobites. In the typical genera Limnadia and
Apjus the body is protected by a carapace, which is bivalve
in the former and shield-like in the latter.  In Limnadia the
carapace covers the greater part of the body, and opens along
the ventral margin. There are from i8 to 30 pairs of membranaceous and respiratory feet.  In Apus the carapace is
Fig. 67.-Phyllopoda. Fairy Shrimp (Chirocejhzalus diaqhanus)-after Baird.
clypeiform and covers a portion of the abdomen; and there
are sixty pair of feet, of which all but the first pair are
foliaceous. Aptus is gregarious, fresh-water in habit, and often
found in great numbers in pools and ditches in Europe. The
different species of Branckhipus have the body unprotected by
any carapace, and are found in ponds and swamps in various
parts of the world. The various "Brine-shrimps" (Artemia)
are found inhabiting the brine-pans in salt-works, or occur in
salt-lakes in both hemispheres, being especially abundant in
Great Salt Lake in Utah.
ORDER III. TRILOB1TA.-This order is entirely extinct, none
of its members having survived the close of the Palaeozoic
period.  It is probable that the Trilobites should be placed
near the Phyllopoda; but their exact position is uncertain, as,
with one exception, no traces of any appendages of any kind,
except the labrum, have hitherto been discovered in any Trilobite.
The body of a Trilobite (fig. 68) was covered with a "crust,"
or exoskeleton, which shows more or less markedly a division
into three longitudinal lobes, from the presence of which the
name of the order is derived.  The shell is composed of a
cephalic shield, a certain number of free and movable thoracic
rings, and a caudal shield, or "pygidium," the rings of which
are more or less completely anchylosed. On the under surface
of the body nothing has hitherto been discovered, except the
" hypostome," or " labrum," which was a plate placed in front
of the mouth.  No traces of ambulatory or natatory limbs, of
branchiae, or of antennae, have ever been discovered.  The
eyes, when present, are compound, and usually sessile, but
11




220                MANUAL OF ZOOLOGY.
are sometimes supported upon projecting processes   It has
generally been supposed that the body of the Trilobite occupied
the medium lobe of the crust, commencing with the " glabella "
in front, and terminating with the " pygidium " behind, whilst
the axial lobes protected a series of delicate respiratory feet;
but this view is doubted by many authorities, and the question
is one which we have at present no means of deciding. Quite
recently, however, a specimen of a Trilobite has been discovered
in which it is said that the bases of the legs were distinctly
recognisable.  The specimen in question was an Asaphus;
but the great number and excellent preservation of Trilobites,
as a general rule, render it highly probable that in most cases
the limbs were destitute of a chitinous exoskeleton, and were
therefore incapable of being preserved in a fossil state. According to Spence Bate, "the young of the Trilobites are of
the Nauplius form."
X               e
Fig. 68.-Morphology of Trilobites.. A   Seg k  2. Diagram of the
Fig. 68. —Morphology of Trilobites. i. Ansgelina Sedgwicki'i; 2. Diagram of the
cephalic shield of a Trilobite (after Salter). a Glabella; bb Free cheeks, bearing
the eyes (o o); c c Fixed cheek, including the eye-lobe (d); e e Facial suture.
The cephalic shield of a typical Trilobite is more or less completely
semicircular (fig. 68, 2), and is composed of a central and of two lateral
pieces, of which the two latter may, or may not, be united together in
front of the former.
The median portion is usually elevated above the remainder of the
cephalic shield, and is called the "glabella;" it protected the region of
the stomach, and is usually divided into from three to four lobes by lateral
grooves. At each side of the glabella, and continuous with it, is a small
semicircular area, called the "fixed cheek." The glabella, with the " fixed
cheeks " is separated from the lateral portions of the cephalic shieldtermed the "movable " or "free cheeks "-by a peculiar suture or line
of division, which is known as the " facial suture," and is quite unknown
amongst recent Crustacea, except for a faint indication in the Limnudl, and
more or less doubtful traces in certain other forms. The movable cheeks
bear the eyes, which are generally crescentic or reniform in shape, are
rarely pedunculated, and consist of an aggregation of facets covered by a
thin cornea.  The facial sutures may join one another in front of the




ANNULOSA: CRUSTACEA.                       221
glabella-in which case the free cheeks will form a single piece-or they
may cut the anterior margin of the shield separately-in which case the
free cheeks will be discontinuous. The posterior angles of the free cheeks
are often produced into long spines.
Behind the cephalic shield comes the thorax, composed of a variable
number of segments, which are not soldered together, but are capable of
free motion upon one another, so as to allow the animal to roll itself up
after the manner of a wood-louse, or hedgehog.  The thorax is usually
strongly trilobed, and each thorax-ring shows the same trilobation, being
compo;ed of a central, more or less strongly convex, portion, called the
"axis," and of two flatter side-lobes, called the " pleurma."
The "pygidium, " or " tail," is usually trilobed also, and, like the thorax,
consists of a median axis and of a marginal limb, the composition of the
whole out of anchylosed segments being shown by the existence of axial
and pleural grooves.
ORDER IV. MEROSTOMATA.-The members of this order
are Crustacea, often. of gigantic size, in which the mouth is
furnished with mandibles and maxillae, the terminations of
which become walking or swimming feet, and organs of prehension.
This order comprises the recent King Crabs, and the extinct
Ptlerygoti and Eurypteri.
SUB-ORDER I. XIPHOSURA.-" Crustacea having the anterior
segments welded together to formn a broad convex buckler,
upon the dorsal surface of which are placed the compound
eyes and ocelli; the former sub-centrally, the latter in the
centre in front. The mouth is furnished with a small labrum,
a rudimentary metastoma and six pairs of appendages.  Posterior segments of the body more or less free, and bearing
upon their ventral surfaces a series of broad lamellar appendages; the telson, or terminal segment, ensiform."-(Henry
Woodward.)
The Xiphosura include no other recent forms than the
Limuli (King Crabs, or Horse-shoe Crabs) (fig. 69).  They
are distinguished by the possession of six pairs of chelate limbs,
placed round the mouth, having their bases spinous and officiating
asjazes.  Six other pairs of foliaceous appendages are attached
to the abdomen, and the last five of these carry branchive.
The body, which is often of great size, when viewed from above
exhibits a division into three portions: —(i) An anterior semicircular shield, which carries two compound and two simple
eyes; (2) a posterior, irregularly hexagonal shield, which covers
the abdomen; and (3) a long, sword-like telson, articulated to
the dorsal buckler, and giving the name to the sub-order.
The chief features, therefore, which characterise the Zimnulus
are as follows: —. The possession of six pairs of appendages
which are placed round the mouth, have their bases spinous,




222                     MANUAL OF ZOOLOGY.
act as jaws, and have their free extremities developed into
claws; 2. The possession of six abdominal pairs of appendages,
expanded for swimming, and carrying the gills; 3. The possession of a semicircular buckler, covering the cephalothorax, and
carrying the eyes upon its upper surface; 4. The possession of
a second buckler, or "operculum," covering the abdomen;
c                        g
Fig. 69.-Xiphosura.   Limulus folyfihe-    Fig. 7o.-Eurypterida. PtergotfLs,Inmus, viewed from below. c The cephalic     glicus, restored (after H. Woodward).
shield carrying the sessile eyes upon its  c c Chelate antenna-; o o Eyes, situated
upper surface; o " Operculum," cover-     at the anterior margin of the carapace;
ing the reproductive organs; b Branchial   m m The mandibles, the first and seplates; a First pair of antennae (anten-   cond maxillae; n n The maxillipedes;
nules) ending in chela-. Below these is    the basal margins of these are serrated,
the aperture of the mouth surrounded       and are drawn as if seen through the
by the spiny bases of the remaining five   metastoma or post-oral plate, which
pairs of appendages, which are regarded    serves as a lower lip. Immediately beby Woodward as being respectively,from     hind this is seen the operculum or thobefore backwards, the great antennae, the  iacic plate which covers the two antemandibles, the first maxillae, the second  rior thoracic somites.  Behind this are
maxillae, and a pair ofmaxillipedes. A11   five thoracic and five abdominal somites,
have their extremities chelate.            and lastly there is the telson (t).
5. The presence of a long, sword-shaped telson, or tail-spine,
articulated to the dorsal shield.
The larval Limrulus does not possess the ensiform  post-anal
spine of the adult, and is further stated to show a decided resemblance to the Trilobites.




ANNULOSA: CRUSTACEA.                 223
The King-crabs are found in the Indian and Japanese Seas,
on the coasts of North America, and in the Antilles. They
sometimes attain a large size, and both the eggs and the flesh
are eaten by the Malays.
SUB-ORDER 2. EURYPTERIDA.-" Crustacea with numerous,
free, thoracico-abdominal segments, the first and second (?) of
which bear one or more broad ]amellar appendages upon their
ventral surface, the remaining segments being devoid of appendages; anterior rings united into a carapace, bearing a pair of
larval eyes (ocelli) near the centre, and a pair of large, marginal, or sub-central eyes; the mouth furnished with a broad
post-oral plate, or metastoma, and five pairs of movable appendages, the posterior of which form great swimming-feet; the
telson, or terminal segment, extremely variable in form; the
integument characteristically sculptured."-(Henry Woodward.)
The Eurypterida are all extinct, and are entirely confined to
the Palaeozoic period. Many of them attained to a comparatively gigantic size; Plerygotus AnzZicus (fig. 70) being supposed to have reached a length of probably six feet.  In their
characters they present many larval features; resembling the
larvae of the Decapoda especially in the fact that all the free
somites of the abdomen (except the two anterior ones) were
totally devoid of appendages.
CHAPTER XXXIV.
MALA COSTRA CA.
SUB-CLASS IV. MALACOSTRACA.  The Crustacea of this subclass are distinguished by the possession of a generally definite
number of body-segments; seven somites going to make up
the thorax, and an equal number entering into the composition of the abdomen (counting, that is, the telson as a somite).
The Malacostraca are divided into two primary divisions,
termed respectively the Edriophthahnata and the Podophthal.mata according as the eyes are sessile, or are supported upon
eye-stalks.
DIVISION A. EDRIOPHTHALMATA.-This division comprises
those Malacostraca in which the eyes are sessile, and the body
is mostly not protected by a carapace. It comprises the three
orders, Laemodizpoda, Isopoda, and Amphipoda. The eyes are
generally compound, but sometimes simple, and are placed on




224             MANUAL OF ZOOLOGY.
the sides of the head.  The head is almost always distinct
from the body, and the mandibles are often furnished with a
palp.  Typically there are seven pairs of feet in the adult,
hence this division is called Tetradecapoda by Agassiz.  In
certain Isopods (Tanais) alone is there a carapace.
ORDER I. LIFMODIPODA.-The Lermodipoda are small Crustaceans, which are distinguished amongst the Edrioph/Zaimafa
by the rudimentary condition of the abdomen.  The first
thoracic segment is amalgamated with the head, and the limbs
of this segment appear to be inserted beneath the head, or, as
it were, beneath the throat (fig. 7 1); hence the name given to
the order. The respiratory organs are in the form of two or
three pairs of membranous vesicles attached to the segments
of the thorax, or to the
bases of the legs.  The
last pair of feet are either
inserted at the end of the
last somite, or are followed
by not more than one or
Fig. 7I.-Lemodipoda. Cad rella ihasma.  two small segments. There
are four setaceous antennae,
and the mandibles are without palps.  The body is generally linear, of eight or nine joints, but is sometimes oval.
The feet are hooked.  The Lamodipoda are all marine, and
one section of the order comprises parasitic Crustaceans, of
which the Whale-louse (Cyamus Ce/i) is the most familiar.
The entire order is now generally regarded as being merely
a section of the Anhztipoda.
ORDER II. AMPHIPODA.-The members of this order resemble those of the preceding in the nature of the respiratory
organs, which consist of membranous vesicles attached to the
bases of the thoracic limbs. The first thoracic segment, however, is distinct from the head, and the abdomen is well
developed, and is composed of seven segments.  There are
seven pairs of thoracic limbs, directed partly forwards, and
partly backwards, the name of the order being derived from
this circumstance. As in the Lemodipoda, the heart has the
form of a long tube extending through the six segments following the head, and having the blood admitted to its interior by
three pairs of valvular fissures. The three posterior pairs of
abdominal limbs are bent backwards, and form, with the telson, a natatory or saltatorial tail.  The young Amphipod
acquires its full number of segments and limbs before its
liberation from the egg; and as a rule the young undergo
little or no metamorphosis in reaching maturity.




ANNULOSA: CRUSTACEA.                  225
All the Amjhipodaa are small, the "Sand-hopper" (Talitrus
iocusta, fig. 72) and the " fresh-water Shrimp" (Gammarus julex)
being two of the commonest forms. The Sand-hoppers and
Gammari swim on their side when in the water, and the former
leap with great activity on land.
Fig. 72.-Amphipoda. The Sand-hopper, Talitrus locusta, enlarged.
ORDER III. ISOPoDA.-In this order the head is always distinct from the segment bearing the first pair of feet. The
respiratory organs are not thoracic, as in the two preceding
orders, but are attached to the inferior surface of the abdomen,
and consist of branchiae, which in the terrestrial species are
protected by plates which fold over them. The thorax is composed of seven segments, bearing seven pairs of limbs, which,
in the females, have marginal plates attached to their bases,
and serving to protect the ova. The number of segments in
the abdomen varies, but is never more than seven. The eyes
are two in number, formed of a collection of simple eyes, or
sometimes truly compound. The heart is sometimes an elongated tube, with three pairs of fissures (as in the AmOhipzoda),
sometimes short or spherical, removed towards the abdomen,
and with more or fewer fissures than the above. The young
Isopod is developed within a larval membrane, destitute of appendages. After a time this membrane bursts, and liberates
the young, which resembles the adult in most respects, but
possesses only six instead of seven pairs of limbs.  Of the
members of this order, many are aquatic in their habits, and
are often parasitic, but others are terrestrial.
By Milne-Edwards the Isopoda are divided into three sections, termed respectively, from their habits, the Natatorial,
Sedentary, and Cursorial Isopods.  In the INatatorial Isopoda
the extremity of the abdomen and the last pair of abdominal




226             MANUAL OF ZOOLOGY.
legs are expanded so as to form a swimming-tail. Some of
this section are parasitic upon various fishes (Cymothoa), whilst
others are found in the sea (Sphafroma).  In the Sedentary
Isopoda the animals are all parasitic, with short, incurved,
hooked feet.  This section
includes the single family of
the Bopyridle, all the species
of which live parasitically,  either in the gill-chambers,
~,0, ~    or attached to'the ventral,2 ki, Add    surface, of certain of the
1(,                      Decapod Crustacea, such as
-",  o ~_.the Shrimps (Crangones) and
the Palcemones.
" "      ) "V'The Curso-rial, or runt ning, Isopods mostly live
upon  the land, and  are
therefore destitute of swimming-feet. The most familiar examples of this section
are the common Wood-lice
(Oniscus).  Here, also, belongs the little Limnoria
terebrans, so well known for
Fig. 73. —Isopoda. Wood-lice (Oniscus).  the destruction which it produces by boring into the
wood-work of piers and other structures placed in the sea.
Other well-known Isopods are the Water-slaters (Asellus) of
fresh waters, the Rock-slaters (Ligia) of almost all coasts, the
Box-slaters (Idothea), the Shield-slaters (Cassidina), and the
Cheliferous Slaters (Tanais).  These last are remarkable as
being the only Isopods in which there is a carapace. The
lateral parts of the carapace are highly vascular, and respiration is effected by these, and not by the abdominal feet.
Many Isopods undergo an extensive metamorphosis.  "In
some Fish-lice (Cymothoa) the young are lively swimmers, and
the adults are stiff, heavy, stupid fellows, whose short clinging
feet are capable of little movement."  In the Bopyridce the
adult females are usually blind, the antennae are rudimentary,
and the abdominal appendages from natatory become respiratory organs. The males, on the other hand, are dwarfed, and
sometimes lose all the abdominal appendages, and all traces of
segmentation; until we get forms which, like Cryptoniscus p/anarioides, "would be regarded as a Flat-worm rather than an
Isopod, if its eggs and young did not betray its Crustacean
nature."-(Fritz Muiller).




ANNULOSA: CRUSTACEA.                227
DIVISION B. PODOPHTHALMATA.-The members of this division have compound eyes supported upon movable stalks or
peduncles, and the body is always protected by a cephalothoracic carapace. Most of the Po:dophthalma pass through Zoeastages in their development.  It comprises the two orders
Stomaapofda and Decapoda, of which the latter includes all the
highest and most familiar examples of the class Crustacea.
ORDER I. STOMAPODA. —In this order there are generally
from six to eight pairs of legs, and the branchiae, when present,
are not enclosed in a cavity beneath the thorax, but are either
suspended beneath the abdomen, or, more rarely, are attached
to the thoracic legs. The shell, also, is thin, and often membranous. From all the preceding orders the Stomapoda are, of
course, distinguished by the possession of pedunculate eyes.
The development of the Stomapoda would appear to be by
means of " Zoeae."
All the Stomapods are marine, and the Locust Shrimp
(Sfuilla mantis) may be taken as a good example of the order.
In this Crustacean the carapace is small, and the posterior
half of the thorax is unprotected. Several of the anterior appendages are developed into powerfully prehensile and hooked
feet. The branchix are attached to the first five pairs of abdominal feet. The three posterior thoracic and the abdominal
appendages are in the form of " swimmerets," and the tail is
expanded into a powerful fin.  Besides the Locust Shrimps,
the order includes the Glass Shrimps (E-icht/zys) and their
allies, and the Opossum Shrimps (Miysis).
ORDER II. DECAPODA.-The members of this order are the
most highly organised of all the Crustacea, as well as being
those which are most familiarly known, the Lobsters, Crabs,
Shrimps, &c., being comprised under this head. For the most
part they are aquatic in their habits, and they are usually protected by strong, resisting shells.  There is always a complicated set of "gnathites," or appendages modified for masticatory *purposes, surrounding the mouth.  The ambulatory
feet are made up of five pairs of legs (hence the name of the
order), the first pair —and often some other pairs behind this
-being " chelate," or having their extremities developed into
nipping-claws.  The branchiae are pyramidal, and are contained in cavities at the sides of the thorax. The carapace is
large, covering the head and thorax, and the anterior part of
the abdomen. The heart of the Dccapoda is in the form of a
more or less quadrate sac, fiurnished with three pairs of valvular
openings. As regards the development of the Decapods enormous differences obtain, even amongst forms very closely
allied to one another.




228               MANUAL OF ZOOLOGY.
The Decapoda are divided into three tribes, termed respectively the Afacrura, Anomura, and Brachlyura, and characterised by the nature of the abdomen.
TRIBE A. MACRURA.-The " long-tailed" Decapods included
in this tribe are distinguished by the possession of a well-developed abdomen, often longer than the cephalothorax, the
posterior extremity of which forms a powerful natatory organ
or caudal fin. As regards the development of the Macrura,
most appear at first in the form of " Zoete;  but there is little
metamorphosis in the common Lobster, and there is said to be
none in the Cray-fish (Astacus fluviatizis) and in one of the
Land -crabs (Gecarcinus).  Fritz Muller, again, has shown
that the primitive form of one of the Shrimps (Pcneius) is that
of a "nauplius."  This section comprises the lobster, Crayfish, Shrimp, Prawn, &c., of which the Lobster may be taken as
the type.
In the Lobster (fig. 74) the somites of the head and thorax
are amalgamated into a single mass, the "cephalothorax,"
covered by a carapace or shield, which is developed from " the
lateral or epimeral elements of the fourth cephalic ring, which
meet along the back, and give way preparatory to the moult.
The tergal elements of the thoracic rings are not developed in
either Crabs or Lobsters; when these rings are exposed by
lifting up the cephalothoracic shield, the epimeral parts alone
are seen, converging obliquely towards one another, but not
joined at their apices."-(Owen.)
The first segment of the head bears the compound eyes,
which are supported upon long and movable eye-stalks or
peduncles. Behind these come two pairs of jointed tactile
organs, the larger called the " great antennae" (fig. 74 ga), the
smaller the " antennules" (a). The mouth is situated on the
under surface of the front of the head, and is provided from
before backwards with an upper lip (" labrum"), two " mandibles," two pairs of "maxillae," three pairs of "maxillipedes"
* The young Decapod, in most cases, leaves the egg in a larval form so
different to the adult that it was originally described as a distinct animal
under the name of Zoea.  In this stage (fig. 76) the thoracic segments
with the five pairs of legs proper to the adult are either wanting or are
quite rudimentary.  The abdomen and tail are without appendages, anal
the lat.er is composed of a single piece. The foot-jaws are in the form (f
natatory forked feet, and the mandible has no palp. Lastly, there are r o
branchire, and respiration is carried on by the lateral parts of the carapace.
The " Zoea " is separated from the "nauplius" by having a segmented
body, large paired eyes (sometimes with a median eye), and a carapace.
The form proper to the adult is not attained until after several moults,
constituting a genuine metamorphosis, though one which is effected by very
gradual stages.




ANNULOSA: CRUSTACE-A.                            229
or "foot-jaws," and a bifid lower lip, or "metastoma."    The
five remaining segments of the thorax carry the five pairs of
ambulatory legs, of which the first (fig. 74, I) constitute the
great claws, or "chelae;" the next two pairs (2 and 3) are also
a!
Fig. 74.-Macrura.  Common Lobster (1-omarus vulgarins).. First pair of legs,
constituting the great chelae or nipping-claws; 2. Second pair of legs, also chelate;
3. Third pair of legs, also chelate; 4 and 5. Last two pairs of ambulatory legs, with
simply pointed extremities; a Antennules; ga Great antennae; ca Carapace.
chelate, though much smaller; and  the last two pairs are terminated by simply pointed extremities. The segments of the
abdomen carry each a pair of' natatory limbs, or " swimmerets,"
the last pair being greatly expanded, and constituting, with the




230             MANUAL OF ZOOLOGY.
"telson," a powerful caudal fin. Most posteriorly of all is the
post-anal plate, or " telson," which may be looked upon either
as an azygos appendage, or as a terminal segment which has
no lateral appendages.
The mouth leads by a short oesophagus into a globose
stomach, in the cardiac portion of which is a calcareous apparatus for triturating the food, which is commonly called the
"lady in the lobster."  The intestine is continued backwards
from the stomach without convolutions, and the anal aperture
is situated just in front of the telson. There is also a welldeveloped liver, consisting of two lobes which open by separate
ducts into the intestine.
The heart is situated dorsally, and consists of a single polygonal contractile sac, which opens by valvular apertures into
a surrounding venous sinus, inappropriately called the " pericardium." The heart is filled with oxygenated blood derived
from the gills, and propels the aerated blood through every
part of the body. The gills (fig. 62, 3, g) are pyramidal bodies
attached to the bases of the legs, and protected by the sides of
the carapace. They consist each of a central stem supporting
numerous laminae, and they are richly supplied with blood, but
are not ciliated. The water which occupies the gill-chambers
is renovated partly by the movements of the legs, and partly
by the expanded epipodite of the second pair of maxillae,
which constantly spoons out the water from the front of the
branchial chamber, and thus causes an entry of fresh water by
the posterior aperture of the cavity.
The nervous system is of the normal "homogangliate" type,
consisting of a longitudinal series of ganglia of different sizes,
united by commissural cords, and placed along the ventral surface of the body. The organs of sense consist of the two compound eyes, the two pairs of antennae, and two auditory sacs.
The sexes are invariably distinct, and the generative products are conveyed to the exterior by efferent ducts, which
open at the base of one of the pairs of thoracic legs. The
ovum is "meroblastic," a portion only of the vitellus undergoing segmentation. The neural side of the body-that is to
say, the ventral surface-appears on- the surface of the ovum,
so that the embryo is built up from below, and the umbilicus
is situated posteriorly.
TRIBE B. ANOMURA.-The'Decapods which belong to this
tribe are distinguished by the condition of the abdomen, which
is neither so well developed as in the AMacrura, nor so rudimentary as in Crabs. Further, the abdomen does not terminate posteriorly in a caudal fin, as in the Lobster.'The




ANNULOSA: CRUSTACEA.                 23I
development in the Anomura appears invariably to take place
through Zoea-forms.
The most familiar of the Anomura are the Hermit-crabs
(Paguridce).  In the common Hermit-crab (Paurus Bernhardus) the abdomen is quite soft, and is merely enclosed in a
membrane, so that the animal is compelled to protect itself by
adopting the empty shell of some Mollusc, such as the common
Whelk, which it changes at will, when too small. The Hermit
is provided with a terminal caudal sucker, and with two or
three pairs of rudimentary feet developed upon the abdomen,
by means of which he retains his position within his borrowed
dwelling. The abdominal appendages, however, are mostly
unsymmetrical. The carapace is not strong, but the claws are
Fig. 75.-Brachyura. The Spiny Spider-Crab (laiea squinado).
Nell developed, one being always larger than the other. Other
forms of the Anomura are the Sponge-crabs (Dromia), the
Crab-lobsters (Porcelanae), and the Tree-crabs (Birgus).
TRIBE C. BRACHYURA.-The "short-tailed" Decapods, or
Crabs, are distinguished from the two preceding tribes by the




232             MANUAL OF ZOOLOGY.
rudimentary condition of the. abdomen, which is very short,
and is tucked up beneath the cephalothorax, the latter being
disproportionately large.  The extremity of the abdomen is
not provided with any appendage, and it is merely employed
by the female to carry the ova. The Crabs (fig. 75) are mostly
furnished with ambulatory limbs, and are rarely formed for
swimming, most of them being littoral in their habits, and some
even living inland.
In all the essential points of their anatomy the Crabs do not
differ from the Lobster and the other Macrura; but they are
decidedly higher in their organisation. This is especially seen
in the disposition of the nervous system, the ventral ganglia
in the Crab being concentrated into a single large ganglion,
from which nervous filaments are sent to all parts of the body.
In the Land-crabs (Gecarciizls) respiration is by branchie,
but there is almost always an aperture behind the carapace for
the admission of air.  They are distributed over the warm
countries of the Old and New Worlds, as well as Australia.
They are essentially terrestrial in
their habits, and migrate in large
bodies to the sea, in order to lay
their eggs.  Besides the true Gecarcini, members of' other very different
families live more or less constantly
on dry land, and have air admitted
directly into the branchial chamber.
Amongst these are the Calling-crabs
(Gelasinmus), the Frog-crabs (Ranina), and the Sand-crabs (Ocypoda).
Reproduction in the Crabs is the
same as in the Macrura, but the
Fig. 76.-Larva (Zoea) of Crab larva is exceedingly unlike the adult,
(Pirimnela denticulata), magni- and approximates closely to the type
fled-after Kinahan.
of the Macrura, another proof that
the Brachyura stand higher in the Crustacean scale.  The
larval Crab was originally described as a distinct animal, under
the name of Zoea (fig. 76), presenting in this condition a long
and well-developed abdomen. It is only after several succes-'sive moults that the young Crab assumes its characteristic
Brachyurous form, and acquires by gradual changes the features
which distinguish the adult. The Zoee of the Crabs are usually
distinguished by the possession of long spines developed from
the carapace. When first liberated from the egg, the Zoea is
enveloped in a larval skin or membrane, which is shed in a
few hours.




ANNULOSA: CRUSTACEA.                  233
CHAPTER XXXV.
DISTRIBUTION  OF THE CRUSTACEA.
DISTRIBUTION OF CRUSTACEA IN SPACE.-The following general principles have been laid down by Milne-Edwards with
regard to the geographical distribution of the Crustacea:i. The different forms and modes of organisation of the
Crustacea are more varied and numerous in proportion as we
pass from the polar regions towards the equator.
2. The number of different species is not only greater, but
the number of types is greater in warm regions as compared
with cold.
3. The higher Crustacea are either entirely wanting or are
sparingly represented in the colder regions of the globe, but
increase rapidly in relative numbers as the equator is approached.
4. The size attained by the Crustacea is greater on the average in warm regions than in colder climates.
5. The special points of structure which are characteristic
of the different groups of Crustacea are more strongly manifested in the warmer regions of the globe.
6. There exists a decided relation between the temperature
of any given region and the character of its Crustacean fauna;
similar generic forms being usually found occupying regions of
the same climatal character.
DISTRIBUTION OF CRUSTACEA IN TIME. —The class Cyrustacca
is largely represented in past time, ranging from the Cambrian
Rocks up to the present day. The oldest families of the Crulstacea are the Trilobita and the Eurypterida, both of which are
exclusively Palaeozoic, and died out at the close of the Carboniferous epoch. It is worthy of notice how larval are the
characters of these ancient groups when compared with their
modern successors. Of the remaining orders the Ciirripedia,
Os/racoda, and Phyllojoda are the three which are most largely
represented.
I. Cirripedia.-The Cirripedes are hardly known as Palxozoic fossils, but valves of a singular member of this order (Tur-ilepas) have been found in the Silurian Rocks of Scotland.
With this exception, the Cirripedes are entirely confined in
past time to the Secondary and Tertiary epochs. The Balanitde are the most common, commencing, as far as is yet
known, in the Eocene period, and attaining their maximum in
recent seas. The [Vei;zucidce commence in the Chalk, and the




234             MANUAL OF ZOOLOGY.
Lepadidce begin still lower, in the Jurassic Rocks, and attain
their maximum of development in the Cretaceous epoch.
2. Ostracoda. -Small Ostracode Crustacea are extremely
abundant as fossils in many formations, and extend from the
Lower Silurian period up to the present day.
3. P/hy'lopoda. —Remains of Crustaceans supposed to belong
to this order are fcund in the Paleozoic Rocks. Hymenocaris
is found in the Upper Cambrian, Caryocaris in the Lower
Silurian, Ceratiocaris in the Upper Silurian, and Di/hyrocaris
in the Carboniferous Limestone. All these forms, with other
similar ones, are believed to be most closely allied to the recent
Apus and NVebalia.
4. Trilobita.-The Trilobites are exclusively Palaeozoic fossils. In the Upper Cambrian Rocks-the so-called "primordial zone "-there occurs a singular group of Trilobites-the
so-called primordial Trilobites-distinguished by the possession of many larval characters.  In the Lower and Upper
Silurian Rocks the Trilobites attain their maximum of development.  They are still well represented in the Devonian
Rocks; but they die out completely before the close of the
Carboniferous epoch, being represented in the Mountain Limestone by three genera only (Phillijpsia, Brachymetopus, and
Griffithides).
5. Eurypterida.-These, like the last, are entirely Paleozoic,
attaining their maximum in the Upper Silurian and Devonian
formations, and dying out in the Carboniferous Rocks. Pterygotus, Eurypterus, and Slimnonia are the most characteristic genera.
6. Xiphosura.-The genus Limulus commenced, as far as is
yet known, in the Permian period, and has survived up to the
present day. Its first appearance, therefore, was just at the
close of the Paleozoic epoch. The two remaining genera,
which constitute with Limulus this sub-order (viz., Bdlinurus
and Prestuwichia), are Palaeozoic, and are not known to occur
out of the Carboniferous Rocks.
7. Isopoida.-The earliest known Isopod is the Prosoponiscus
of the Permian Rocks.
8. Stomapoda. —This order is doubtfully represented in the
Carboniferous Rocks.
9. Decapoda.-The Decapods, with the exception of a single
doubtful form from the Carboniferous Rocks, are not known to
have existed at all during the Palaeozoic period; but they are
well represented, in all their three tribes, in the Secondary and
Tertiary epochs, attaining their maximum at the present day.
The London Clay (Eocene) is especially rich in the remains
of Macrura and Brachyura.




ANNULOSA: ARACHNIDA.                 235
CHAPTER XXXVI.
ARA CHNIDA.
CLASS II. ARACHNIDA.-The Arachznida-including the Spiders, Scorpions, Mites, &c.-possess almost all the essential
characters of the Crustacea, to which they are very closely
allied. Thus, the body is divided into a variable number of
somites, some of which are always provided with articulated
appendages. A pair of ganglia is primitively developed in
each somite, and the neural system is placed ventrally. The
heart, when present, is always situated on the opposite side of
the alimentary canal to the chain of ganglia. The respiratory
organs, however, whenever these are differentiated, are never
in the form of branchie as in the Crustacea, but are in the form
either of pulmonary vesicles or sacs, or of ramified tubes,
formed by an involution of the integument, and fitted for
breathing air directly. Further, there are never "more than
four pairs of locomotive limbs, and the somites of the abdomen,
even when these are well developed, are never provided with
limbs;" the reverse being the case amongst the Crus/acea.
Lastly, "in the higher Arachnida, as in the higher Crustacra,
the body is composed of twenty somites, six of which are allotted to the head; but, in the former class, one of the two
normal pairs of antennae is never developed, and the eyes are
always sessile; while, in the higher Crustacea, the eyes are
mounted upon movable peduncles, and both pairs of antennae
are developed." —(Huxley.)
The head in the Arachnida is always amalgamated with the
thorax, to form a "cephalothorax;" the integument is usually
chitinous, and the locomotive limbs are mostly similar in form
to those of insects, and are usually terminated by two hooks.
In many of the Arachnida the integument remains soft over
the entire body; in others, as in the majority of Spiders, the
abdomen remains soft and flexible, whilst the cephalothorax is
more.or less hard and chitinous; in the Scorpions, again, the
integument over the whole body forms a strong chitinous shell.
The typical somite of the Arachnida is constituted upon
exactly the same plan as that of the Crustacea, consisting
essentially of a dorsal and ventral arc; the former composed
of a central piece, or " tergum," and of two lateral pieces, or
"epimera;" whilst the latter is made up of a median "sternum" and of two lateral " episterna."
As regards the composition of the cephalothorax of Spiders,




236             MANUAL OF ZOOLOGY.
"the tergal elements of the coalesced segments are wanting,
and the back of the thorax is protected by the elongation, convergence, and central confluence of the epimeral pieces; the
sternal elements have coalesced into the broad plate in the
centre of the origins of the ambulatory legs, from which it is
separated by the episternal elements.....  The non-development of the tergal elements explains the absence of wings."
-(Owen.)
The mouth is situated, in all the Arachnida, in the anterior
segment of the body, and is surrounded by suctorial or masticatory appendages.  In the higher Arac/nida, the mouth is
provided from before backwards with the following appendages
(fig. 77, 4). i. A pair of "mandibles," used for prehension.
2. A pair of " maxillae," each of which is provided with a long
jointed appendage, the "maxillary palp."  3. A lower lip, or
"labium."  In the Scorpion, an upper lip, or "labrum," is
also present.
In the Spiders (fig. 77, 4) each mandible terminates in a sharp
movable hook, which possesses an aperture at its' extremity
communicating by a canal with a gland, which is placed in the
preceding joint of the mandible, and secretes a poisonous
fluid.  The maxillary palps in the Spiders are long, jointed
appendages; terminated in the females by pointed claws, but
frequently swollen, and carrying a special sexual apparatus in
the males.
In the Scorpions (fig. 77, 1) the mandibles are short, and
terminate in strong pincers, or "chelicerae."  The maxillary
palpi are also greatly developed, and constitute powerful
grasping-claws, or "chelae." In the genus Galeodes, the mandibles, like those of the Scorpion, constitute "chelicerae,"
though comparatively much larger and longer; but the maxillary palps are not developed into "chelae."
With regard to antennae, these organs, as such, do not exist
in the Arachnida.  It is generally believed, however, that the
mandibles of the Arachnida are truly homologues, not of the
parts which bear the same name in the other Arthropoda, but
of the antennae. The antennae, therefore, of the Spiders, are
converted into prehensile and offensive weapons; whilst in the
Scorpions, as in the King-crabs, they are developed into nipping-claws, or chelae.
In the lower Arachnida, the organs of the mouth, though
essentially the same as in the higher forms, are enveloped in a
sheath, formed by the labium and maxillae, whilst the mandibles are often joined together so as to constitute a species of
lancet.




ANNULOSA: ARACHNIDA.                             237
The mouth opens into  a pharynx, which is of remarkably
small calibre in the true spiders, all of which live simply on
the juices of their prey.  The intestinal canal is usually short
3
Fig. 77.-Morphology of Arachnida. i. Organs of the mouth in the Scorpion, on
one side; 7t Mandibles (antennae) converted into chela:, and called the chelicera:;
pi Maxillary palpi greatly developed, and forming strong chelae. 2. Telson of the
Scorpion. 3. One of the abdominal segments of the Scorpion, showing the "stigmata," or apertures of the pulmonary sacs. 4. Tegenaria domzestica, the common
Spider (male), viewed from below; s Spinnerets; nz Mandibles with their perforated
hooks-below the mandibles are the maxillae, and between the bases of these is the
labium; p The maxillary palpi with their enlarged tumid extremities.
and straight, no convolutions intervening between the mouth
and the aperture of the anus. Often, however, lateral caeca
are appended to the alimentary tube. Salivary glands are also
present, as well as ramified tubes, supposed to perform the
functions of a kidney, and to correspond to the " Malpighian
vessels" of Insects.
The circulation in the Arachnida is maintained by a dorsal
heart, which is situated above the alimentary canal. Usually
the heart is greatly elongated, and resembles the " dorsal
vessel" of the Insec/a.  In the lower Arachnida, however, there
is no central organ of the circulation, and there are no differentiated  blood-vessels.   All the Arachnida  breathe  the  air
directly, and the respiratory function is performed by the
general surface of the body (as in the lowest members of the
class), or by ramified air-tubes, termed "tracheae," or by distinct pulmonary chambers of sacs; or, lastly, by a combination
of tracheae and pulmonary vesicles.  The " tracheae " consist of
ramified or fasciculated tubes, opening upon the surface of the




238             MANUAL OF ZOOLOGY.
body by distinct apertures, called "stigmata."   The walls
of the tube are generally prevented from collapsing by means
of a chitinous fibre or filament, which is coiled up into a spiral,
and is situated beneath their epithelial lining. The pulmonary
sacs are simple involutions of the integument, abundantly supplied with blood; the vascular surface thus formed being increased in area by the development of a number of close-set
membranous lamellae, or vascular plates, which project into
the interior of the cavity. Like the tracheae, the pulmonary
sacs communicate with the exterior by minute apertures, or
"stigmata" (fig. 77, 3).
The nervous system is of the normal articulate type, but is
often much concentrated. In the Spiders there is a cephalic
or " cerebral " ganglion, a large thoracic ganglion, and irl some
instances a small abdominal ganglion. In some of the lower
forms the articulate type of nervous system is lost, and there is
merely a ganglionic mass which is traversed by the gullet. In
none of the Arachnida are compound eyes present, and in none
are the eyes supported upon foot-stalks. The organs of vision,
when present, are in the form of from two to eight simple eyes,
or " ocelli."
In all the Arachnida, -with the exception of the Tardigrtada,
the sexes are distinct.  The great majority of the Arachnida
are oviparous, and in most cases the larvae' are like the adult in
all except in size.  In some cases, however (Acarina), the
larvae have only six legs, and do not attain the proper four
pairs of legs until after some moults.
The Arachnida may be divided into two great sections or
sub-classes-viz., the Trachearia, in which respiration is effected
by the general surface of the body, or by tracheae, and there
are never more than four ocelli; and the Pulmonaria, in which
respiration is effected by pulmonary sacs, either alone. or combined with tracheae, and there are six or more eyes.
CHAPTER XXXVII.
DIVISIONS OF THE ARACHNIDA.
DIVISION A. TRACHEARIA.-Respiiration cufaneous, or by trac/eae.
Eyes never more than four in number.
The Trachearia comprise three orders-viz., the Podosozmata,
the Acari-ina or Afonomerosolata, and-the Adelarth/iosomata.




ANNULOSA: ARACHNIDA.                 239
ORDER I. PODOSOMATA (Pantopoda).-The members of this
order, sometimes called " Sea-spiders," have been placed alternately amongst the Arachnida and the Crustacea, their true
position being rendered doubtful by the fact that, though
marine in their habits, they possess no differentiated respiratory organs. They possess, however, no more than four pairs
of legs, and would therefore appear to be properly referable
to the Arachnida.  The commoner forms of the Podosomata
(such as Xymphon and Pycnogonum) may be found on the seacoast at low water, crawling about amongst marine plants or
hiding beneath stones. Some species of the latter genus are
asserted to be parasitic upon fishes and other marine animals,
but the common British species (P. littorale) is free when
adult, and does not appear to be parasitic at any stage of its
existence (fig. 78, a). The legs consist of four pairs, sometimes greatly exceeding the body in length, and sometimes
containing cxecal prolongations of the digestive cavity for a
portion of their length. The mouth is provided with a pair of
"chelicerae," or chelate mandibles, and with two well-developed
maxillary palpi, behind which in the female are a pair of false
legs which carry the ova. The abdomen is rudimentary.
Though there are no respiratory organs, there is a distinct
heart. The sexes are in different individuals.
ORDER II. ACARINA or MONOMEROSOMATA.-The members
of this order possess an unsegmented abdomen which is fused
with the cephalothorax into a single mass. Respiration is
effected by tracheae. Most of the Acarina are parasitic, and
the most familiar are the Mites and Ticks.
Family I. Linguatulina or Pentastonmida.-The members of
this family are singular vermiform animals, found as parasites
in the frontal sinuses and lungs of some Vertebrates. In their
adult condition they possess no external organs except two
pairs of hooks, representing limbs, placed near the mouth.
They thus closely approximate to the TrCeiada, beside which
they have been generally placed. In the young condition,
however, they possess four articulated legs, and even in the
adult state the characters of the nervous system are higher
than those of the Scolecida.  There are no differentiated organs
of respiration, and there are no circulatory organs, but the
sexes are distinct.
Family 2. Macrobiotide (YTardigrada or Arctisca). — The
"Sloth " or "Bear animalcules," which compose this family,
are microscopic animals, very much like Rotzfers, found in
damp moss and in the gutters of houses. The nervous system
consists of four ganglia, and there is a suctorial mouth, with




240              MANUAL OF ZOOLOGY.
rudimentary jaws or stilets. The abdomen is undeveloped,
and there are four pairs of rudimentary legs. They exhibit
no traces of either circulatory or respiratory organs, and the
sexes are united in the same individual.
Family 3. Acarida. —This family includes the Mites, Ticks,
and Water-mites, some of which are parasitic, whilst others
are free, and some are even aquatic in their habits. The mouth
is formed for suction. There is no definite line of demarcation
between the unsegmented abdomen and the cephalothorax.
In the true Acari (fig. 78, b), of which the Cheese-mite may
be taken as an example, there are four pairs of legs, adapted
for walking, and the mouth is provided with distinct mandibles.
Besides the Cheese-mite (A. domesticus), another well known
species is the Acarus destructor, which feeds upon various zoological specimens, and is very annoying to the naturalist. In
the Sarcoptes scabiei-the cause of the skin-disease known as
the "itch "-the two anterior pairs of legs are provided with
suckers, and the two posterior are terminated by bristles; the
mouth, also, is furnished with bristles.  In the Ticks (Ixodes)
the mouth is provided with a beak, or "rostrum," which enables them to pierce the skin, and retain their hold firmly. In
the fIydrachnidce (fig. 78, c), or Water-mites, the head is furC
Fig. 78. —Arachnmda. a Pycnogonurn li/torale; b Tetranychus telarius, one of the
" Sociable " mites; c Hydrachna globulus, one of the " Water-mites."
nished with two or four ocelli, and there are four pairs of hairy
natatory legs. They are parasitic, during at least a portion cf
their existence, upon Water-beetles and other aquatic insects.
They pass through a metamorphosis, the larva being hexapod,
or having only three pairs of legs.  The Garden-mites (Trombidide) and Spider-mites (Ganasidre) live upon plants; the
Wood-mites (Oribatidce) and Harvest-ticks (Leptidce) are to be
found amongst moss and herbage, or creeping upon trees or
stones; whilst the true Ticks (Ixodiidw) attach themselves para



ANNULOSA: ARACHNIDA.                  241
sitically by means of their suctorial mouth to the bodies of
various Mammals, such as sheep, oxen, dogs, &c. Several
Mites (Thalassarachna, Pontarachna, &c.) have been found to
inhabit salt water, and several species of Trombididee live habitually between tide-marks.
Another member of the Acarina is the curious little Demodex
folliculorum, which is found in the sebaceous follicles of man,
especially in the neighbourhood of the nose.  It is probable
that very few, if any, individuals are exempt from this harmless parasite.
ORDER III. ADELARTHROSOMATA. -- The members of this
order, comprising the Harvest-spiders, the Book-scorpions, &c.,
are distinguished from the preceding by the possession of an
abdomen, which is more or less distinctly segmented, but
generally exhibits no line of separation from the cephalothorax,
the two regions being of equal breadth and conjoined together.
The mouth is furnished with masticatory appendages, and
respiration is-effected by tracheae, which open on the lower
surface of the body by two or four stigmata.
Family I. Phalangide. -The well known " Harvest-spiders"
belong to this family.  They are characterised by the great
length of the legs, and by the filiform maxillary palpi, terminated by simple hooks.
_Family 2. Pseudoscorpionidea. ( Che/feridce). - The " Bookscorpion" (Cheizfer) is a common little animal in old books.
It is distinguished by the fact that the maxillary palpi are of
large size, and are converted into nipping-claws or chelxe, thus
giving the animal the appearance of a Scorpion in miniature.
Family 3. Soipugitei.-In this family the abdomen is not
only very distinctly segmented, but is also clearly separated
from the abdomen. The mandibles in Galeodes, which is the
type of the group, are chelate, but the maxillary palpi constitute long feet.
DIVISION B. PULMONARIA.-Respiration by pulmonary' sacs
alone, or by pulmonary sacs cozboined waith trachese. Eycs six
or more in number. Abdomen usuaily distinct from the ceprhalothorax.
This division comprises the higher Arachnida, such as the
Scorpions, and the majority of what are commonly known as
Spiders; the former constituting the order of the Pedijalpai,
the latter that of the Araneida or Dimerosomata.
ORDER I. PEDIPALPI.-In this order are the true Scorpions,
together with certain other animals which are in some respects
intermediate between the Scorpions and the true Spiders.
The members of this order are distinguished by the fact that




242             MANUAL OF ZOOLOGY.
the abdomen- in all is distinctly segmented, but is not separated
from the cephalothorax by a well-marked constriction. They
agree in this character with the Adelarthrosomata; hence the
two are sometimes united into a single order (Arthrogastra),
but they are separated by the nature of the respiratory organs,
the latter breathing by tracheae, and not by pulmonary sacs.
Family I. Scorp5ionide.-The Scorpions are amongst the best
known of the Arachnida, as well as being amongst the largest.
They are distinguished by their long, distinctly segmented abdomen, terminating in a hooked claw (figs. 77, 79). This claw,
which is really a modified "telson," is the chief offensive weapon
of the Scorpion, and is perforated at its point by the duct of a
poison-gland which is situated at its base. The abdomen is
composed of twelve somites, but there is no evident line of demarcation between this region and the cephalothorax. The
thoracic segments carry four pairs of ambulatory feet. There
are six, eight, or twelve simple eyes. The maxillary palpi are
Fig. 79. —Scorpion (reduced).
greatly developed, and constitute strong nipping - claws, or
"chelk" (figs. 77, 79). The mandibles (antennae) also form
claws, or "chelicerae." The respiratory organs are in the
form of pulmonary sazs, four on each side, opening upon the
under surface of the abdomen by as many stigmata, each of
which is surrounded by a raised margin, or "peritrema" (fig.
77, 3).
The Scorpions are mostly inhabitants of warm regions, and
their sting, though much exaggerated, is of a very' severe
nature. They live under stones or in dark crevices, and run
swiftly, carrying the tail curved over the back. They feed on
Insects, which they hold in the chelate palpi and sting to
death.
Family 2. Thelypjhonide.-The members of this family in




ANNULOSA: ARACHNIDA.                  243
external appearance closely resemble the true Spiders, from
which they are separated by the possession of a segmented
abdomen, and long spinose palpi, and by the absence of spinnerets. They are distinguished from the Scorpionid&e by the
amalgamation of the head and thorax into a single mass, which
is clearly separated from the abdomen by a slight constriction,
as well as by the fact that the maxillary palpi terminate in
movable claws instead of chelke. Further, the extremity of
the abdomen is not furnished with a terminal hook, or "sting."
ORDER II. ARANEIDA or SPHAROGASTRA.-This order includes the true Spiders, which are characterised by the amalgamation of the cephalic and thoracic segments into a single
mass, and by the generally soft, unsegmented abdomen, attached
to the cephalothorax by a constricted portion, or peduncle.
Respiration is effected by pulmonary sacs usually in combination with tracheae. (Hence the name Pulmotrachearia, sometimes applied to the order.) The number of the pulmonary
sacs is smaller in the true Spiders than in the Scorpions, being
either two or four, opening by as many stigmata upon the
under surface of the abdomen.
The head bears from six to eight simple eyes; the mandibles are simply hooked, and are perforated by the duct of
a gland which secretes a poisonous fluid; and the maxillary
palpi are never chelate.
Spiders (fig. 80) are all predaceous animals, and many of
them possess the power of constructing webs for the capture
Fig. 80.-Araneida. Theridion rziariunz (female).
of their prey or for lining their abodes. For the production
of the web, Spiders are furnished with special glands, situated
at the extremity of the abdomen.  The secretion of these
glands is a viscid fluid, which hardens rapidly on exposure to
air, and which is cast into its proper, thread-like shape, by
12




244             MANUAL OF ZOOLOGY.
being passed through what are called the " spinnerets." These
are little conical or cylindrical organs, four or six in number,
situated below the extremity of the abdomen.  The excretory
ducts of the glands open into the spinnerets, each of which
has its apex perforated by a great number of minute tubes,
through which the secretion of the glands has to pass before
reaching the air.  Many spiders, however, do not construct
any web, unless it be for their own habitations, but hunt their
prey for themselves.
As regards the reproductive process in the Spiders, it appears
certain that the act of copulation, so to speak, is performed by
the males by means of the maxillary palpi, the extremities of
which are specially modified for this purpose. The testes are
abdominal, but the semen appears to be stored up in the
enlarged extremities of the maxillary palps, which thus perform the part of the vesiculae seminales. " The most careful
observations, repeated by the most attentive and experienced
entomologists, have led to the conviction that the ova are
fertilised by the alternate introduction into the vulva of the
appendages of the two palpi of the male.  Treviranus's supposition that these acts are merely preliminary stimuli, has
received no confirmation, and is rejected by Duge's, Westwood,
and Blackwall; and with good reason, as the detection of the
spermatozoa in the palpal vesicles has shown... Duge's
offers the very probable suggestion that the male himself may
apply the dilated cavities of the palpi to the abdominal aperture (of the testes), and receive from the vasa deferentia the
fertilising fluid, preparatory to the union.... Certain it
is that an explanation of this singular condition of the male
apparatus, in which the intromittent organ is transferred to the
remote and outstretched palp, is afforded by the insatiable
proneness to slay and devour in the females of these most
predaceous of articulated animals."-(Owen.)
The Spiders are oviparous, and the young pass through no
metamorphosis; but they cast their skins, or moult, repeatedly,
before they attain the size of the adult.
DISTRIBUTION OF ARACHNIDA IN TIME.-The Arachnida
are only very rarely found in a fossil condition. As far as is
yet known, both the Scorpions and the true Spiders appear to
have their commencement in the Carboniferous epoch, the
former being represented by the celebrated Cyclop/thalnusl
senior from the Coal-measures of Bohemia. Spiders are also
known to occur in the Jurassic Rocks (Solenhofen Slates) and
in the Tertiary period.




ANNULOSA: MYRIAPODA.                   245
CHAPTER XXXVIII.
Mf lYRIAPODA.
CLASS III. MYRIAPODA.-The Myriaipoda are defined as articulate animals in which the head is distinct, and the remainder
of the body is divided into nearly similar segments, the thorax
exhibiting no clear line of demarcation from  the abdomen.  There
is one pair of antennae, and the number of the legs is always more
than eight pairs.  Respiration is by trachea.
In this class-comprising the Centipedes (fig. 8I) and the
Millipedes-the integument is chitinous, the body is divided
into a number of somites provided with articulated appendages,
and the nervous and circulatory organs are
constructed upon a plan similar to what we
have seen in Crustacea and Arachnida.  The
head is invariably distinct, and there is no
marked line of demarcation between the segments of the thorax and those of the abdomen.
The body, except in Pauroapzs, always consists
of more than twenty somites, and those which
correspond to the abdomen in the Arachnida
and Insecta are always provided with locomotive limbs.  "The head consists of at least
five, and probably of six, coalescent and modified somites; and some of the anterior segments of the body are, in many genera, coalescent, and have their appendages specially
modified to subserve prehension."-(Huxley.)
Pauropus has only nine pairs of legs; but with
this exception, eleven pairs of legs is the smallest number known in the order.
The respiratory organs, with one exception,
agree with those of the Insecta and of many of',A
the Arachnida in being " trachee" —that is to      1!
say, tubes, which open upon the surface of the,
body by minute apertures, or " stigmata," and     i
the walls of which are strengthened by a spirallycoiled filament of chitine.  The trachea may      -
or may not anastomose with one another as  "(Scolojendra).
they do in Insects.
The somites, with the exception of the head and the last
abdominal segment, are usually undistinguishable from one
another, and each bears a single pair of limbs. In some cases,




246             MANUAL OF ZOOLOGY.
however, each segment appears to be provided with two pairs
of appendages (fig. 82). This is really due to the coalescence
of the somites in pairs, each apparent segment being in reality
composed of two amalgamated somites.  This is shown, not
only by the bigeminal limbs, but also by the arrangement of
the stigmata, which in the normal forms occur on every alternate ring only, whereas in these aberrant forms they are found
upon every ring.
The head always bears a pair of jointed antennae, resembling
those of many Insects, and behind the antennae there is generally a variable number of simple sessile eyes. In one species
(Scutigera) compound facetted eyes are present; and in Pauroptus the antennae are bifid, and carry many-jointed appendages,
thus differing wholly from the antennae of Insects, and presenting a decided approximation to the Crustacea.
The young in some cases, on escaping from the egg, possess
nearly all the characters of the parents, except that the number
of somites, and consequently of limbs, is always less, and increases at every change of skin (" moult" or " ecdysis ").  In
most cases, there is a species of metamorphosis, the embryo
being at first either devoid of locomotive appendages, or possessed of no more than three pairs of legs, thus resembling the
true hexapod Insects. It is believed, however, that the legs of
these hexapod larvae do not correspond homologically with the
three pairs of legs proper to adult Insects.  In these cases the
number of legs proper to the adult is not obtained until after
several moults, the entire process being stated to occupy in
some species as much as two years, before maturity is reached.
The zMyriapoda are divided into three orders-viz., the Chilopoda, the Chizlognazha, and the Pauropoda.
ORDER I. CHILOPODA. -This order comprises the wellknown carnivorous Centipedes and their allies, and is characterised by the number of legs being rarely indefinitely great
(usually from I5 to 20 pairs), by the composition of the antennae out of not less than I4 joints (14 to 40 or more), and
by the structure of the masticating organs.  These consist of
a pair of mandibles with small palpi, a labium, and two pairs
of " maxillipedes," or foot-jaws, of which the second is hooked,
and is perforated for the discharge of a poisonous fluid. There
is not more than one pair of legs to each somite, and the last
two limbs are often directed backwards in the axis of the body,
so as to form a kind of tail.  The body in all the Chilopoda is
flattened, and the generative organs open at the posterior end
of the body.
Scolpfendfra (fig. 8i), Lithobius, and Geophilus Are common




ANN ULOSA: MYRIAPODA.                247
European genera of this order.  The ordinary Centipedes of
this country are perfectly harmless, but those of tropical regions sometimes attain a length of a foot, or more, and these
are capable of inflicting very severe, and even dangerous, bites.
ORDER II. CHILOGNATHA.-This order comprises the vegetable-eating Millipedes (Iulid&e) and the Gallyworms (Polydesmus). The order is characterised by the great number of legs,
-each segment, except the six or seven anterior ones, bearing
two pairs; by the composition of the antennae out of six or
seven joints; and by the structure of the masticating organs,
which consist of a pair of mandibles without palps, covered by
a lower lip, composed of the confluent maxillae. The generative apertures are placed in the anterior portion of the body.
Fig. 82. —Millipede (Izulus).
In the common Millipede (Iulus) the body is composed of
from forty to fifty segments, each of which bears two pairs of
minute, thread-like legs. The Auli of this country are of small
size, but an American species attains a length of more than
half a foot.
ORDER III. PAUROPODA.-In this order is only an extraordinary little Myriapod, described by Sir John Lubbock
under the name of Pauropus. The body is only one-twentieth
of an inch in length, and consists of ten somites, furnished with
scattered setve. There are only nine pairs of legs, of which
one pair is carried by the 3d segment, whilst the 4th, 5th, 6th,
and 7th segments carry each two pairs of legs, and may therefore be regarded as really double.  The head is composed of
two segments, and is not provided with jaw-feet. The antenna
are five-jointed, bifid, with three long multi-articulate appendages.  The body is white and colourless, and there are no
tracheae, so that respiration must be effected entirely by the
skin.  Pauropus is found amongst decaying leaves in damp
situations, and species have been described both from Britain
and America. It is separated from the Chidlopoeda by its small
number of legs, the absence of foot-jaws, and the composition
of the antennae out of no more than five joints.
DISTRIBUTION OF MYRIAPODA IN TIME. — About twenty
species of Myriapoda are known as fossils, the oldest example
of the order having been found in the Carboniferous epoch.




248             MANUAL OF ZOOLOGY.
Front rocks of this age several species of ChilognathQus Myriapods have been discovered.  They belong to the genera
Xylobius and Archiulus, and have been placed in a special
family under the name of Archiulidte. The occurrence of
air-breathing articulate animals (both Arachnida and Myriapoda) in the Carboniferous period is noticeable, as being contemporaneous with the earliest known terrestrial Molluscs.
CHAPTER XXXIX.
INSECTA.
GENERAL CHARACTERS OF THE INSECTA.
CLASS IV. INSECTA.-The Inzsecta are defined as articulate
animals in which the head, thorax, and abdomen are distinct;
there are three pairs of legs borne on the thorax; the abdomen
is destitute of legs; a single pair of antennae is present; mostly,
there are two pairs of wings on the thorax.  Respiration is
effected by trachece.
In the Insecta the body is divided into a variable number of
definite segments, or somites, some of which are furnished
with jointed appendages, and the nervous and circulatory
systems are constructed upon essentially the same plan as in
the Crustacea, Arachnida, and Afyriapoda. The head, thorax,
and abdomen are distinct (fig. 83), and the total number of
somites in the body never exceeds twenty.  "Of these, five
certainly, and six probably, constitute the head, which possesses a pair of antennae, a pair of mandibles, and two pairs of
maxille, the hinder pair of which are coalescent, and form the'labium.' Three, or perhaps, in some cases, more, somites
unite and become specially modified to form the thorax, to
which the three pairs of locomotive limbs, characteristic of
perfect Insects, are attached. Two additional pairs of locomotive organs, the wings, are developed, in most insects,
from the tergal walls of the second and third thoracic somites.
No locomotive limbs are ever developed from the abdomen of
the adult insect, but the ventral portions of the abdominal
somites, from the eighth backwards, are often metamorphosed
into apparatuses ancillary to the generative function."(Huxley.)
The integument of the Insecta, in the mature condition, is




ANNULOSA: INSECTA.                       249
more or less hardened by the deposition of chitine, and usually
forms a resisting exoskeleton, to which the muscles are attached.
The'segments of the head are amalgamated into a single piece,
which bears a pair of jointed feelers or antennae, a pair of eyes,
usually compound, and the appendages of the mouth. The
segments of the thorax are also amalgamated into a single
piece; but this, nevertheless, admits of separation into its constituent three somites (fig. 83).  These are termed  respectively, from  before backwards, the " prothorax," " mesothorax,"
and "metathorax," and each bears a pair of jointed legs.  In
the great majority of Insects, the dorsal arches of the mesothorax and metathorax give
origin each to a pair of
wings.
Each leg consists of from
six to nine joints.  The
first of these, which is attached to the sternal sur-  c
face of the thorax, is called
the "coxa," and is succeeded by a short joint.
termed the "trochanter.'        i         /               
The trochanter is followed            I /
by a joint, often of large              /    
size, called the "fenmur,"
and this has articulated             I
to it the "tairsus," which
may be composed of from
two to five joints.
The wings of Insects
are membranous "flattened vesicles, sustained by
slender but firm  hollow
tubes, called'nervures,'  Fig. 83.-Diagram of Insect. a Head, carrying
along which branches of   the eyes and anten..e; b Prothorax, ca-rryinlg
the first pair of legs; c Mesothorax, carrying
the trachea  and channels   the second pair of legs and first pair of wings; d
-  Metathorax, with the third pair of legs and the
of the circulation are con-   second pair of wings; e Abdemen, without limbs,
tinued." -  (Owen.)  Ac-   but having terminal appendages subservient to
cording to Newport, the
wings of Insects are "expanded portions of the common integument of the sides of the meso- and meta-thorax, occasioned
by the enlargement and extension of numerous tracheae and
the accompanying passages for the circulatory fluids, and their
motions are intimately connected with the function of respiration."  In the Coleoptera (Beetles) the anterior pair of wings




250             MANUAL OF ZOOLOGY.
become hardened by the deposition of chitine, so as to form
two protective cases for the hinder membranous wings. In
this condition the anterior wings are known as the " elytra," or
"wing-cases."  In some of the ]Hmizftera this change only
affects the inner portions of the anterior wings, the apices of
which remain membranous, and to these the term "hemelytra"
is applied. In the Di)ztera the posterior pair of wings are
rudimentary, and are converted into two capitate filaments,
called "halteres," or "balancers."  In the Strepsiltera the
anterior pair of wings are rudimentary, and are converted into
twisted filaments.
The primitive number of somites in the abdomen of insects
is said to be eleven (Orthoptera), but nine is the number ordinarily present; and though these are distinct in most larvae, it is
seldom that more than seven or eight are recognisable in the
adult. The abdominal someites are usually more or less freely
movable upon one another, and never carry locomotive limbs.
The extremity of the abdomen is, however, not' infrequently
furnished with appendages, which are connected with the
generative function, and not infrequently serve as offensive
and defensive weapons. Of this nature are the ovipositors of
Ichneumons and other Insects, and the sting of Bees and
Wasps. In the Earwig (Forficula) these caudal appendages
form a pair of forceps; whilst in many Insects they are in the
form of bristles, by which powerful leaps can be effected, as is
seen in the Springtails (Poedzrce).  In some insects (as the
Mole-cricket and Cockroach), the 9th or Ioth abdominal segment carries jointed antenniform appendages, which, though
perhaps partially or even primarily generative in function, are
certainly organs of sense, being connected with smell or
hearing.
The organs about the mouth in Insects are collectively
termed the " trophi," or "instrumenta cibaria." Two principal
types require consideration-namely, the masticatory and the
suctorial-both types being sometimes modified, and occasionally combined.
In the Masticatory Insects, such as the Beetles (fig. 84, I),
the trophi consist of the following parts, from before backwards:(I.) An upper lip, or "'labrum," attached below the
front of the head.  (2.) A pair of biting-jaws, or "mandibles."
(3.) A pair of chewing-jaws, or "maxillae," provided with one
or more pairs of "maxillary palps," or sensory and tactile
filaments.  (4.) A lower lip, or "labium," composed of a
second coalescent pair of maxillae, and also bearing a pair of
palpi, the "labial palps."  The primitive form of the labium,




ANNULOSA: INSECTA.                        251
that, namely, of a second pair of maxillae, is more or less perfectly retained by the Orthojptera and some of the Neuroptera.
The lower or basal portion of the labium is called the " menturnm " or chin, whilst the upper portion is more flexible, and is
termed the "ligula."  The upper portion of the ligula is often
developed into a kind of tongue, which is very distinct in some
Insects, and is termed the "lingua."
0                         b
r  3           2
3                                   1
Fig. 84.-Organs of the mouth in Insects. I. Trophi of a masticating Insect (Beetle):
a Labrum or upper lip; b Mandibles; c Maxillae with their palpi; d Labium or
lower lip with its palpi. 2. Mouth of a Butterfly: o Eye;f Base of antennae; g
Labial palp; h Spiral trunk or "antlia." 3. Mouth of a Hemipterous Insect (Neepa
cinerea): I Labium: m Maxillae; n Mandibles.
In the typical suctorial mouth, as seen in the Butterflies
(fig. 84, 2), the following is the arrangement of parts:-The
labrum  and the mandibles are now  quite rudimentary; the
first pair of maxillae is greatly elongated, each maxilla forming
a half-tube.   These maxilla  adhere together by their inner
surfaces, and thus form a spiral "trunk," or "antlia" (inappropriately called. the " proboscis "), by which the juices of flowers
are sucked up.  Each maxilla, besides the half-tube on one
side, contains also a tube in its interior; consequently on a
transverse section the trunk is found really to consist of three
canals, one in the anterior of each maxilla, and the third formed
between them by their apposition. To the base of the trunk
are attached the maxillary- palpi, which are extremely small.
Behind the trunk is a small labium, composed of the united
second pair of maxilke.  The " labial palpi" are greatly developed, and form two hairy cushions, between which the trunk
is coiled up when not in use.
In the Bee there exists an intermediate condition of parts,
the mouth being fitted partly for biting and partly for suction.
The labrum and mandibles are well developed, and retain their




252               MANUAL OF ZOOLOGY.
usual form.  The maxillae and the labium  are greatly elongated; the former being apposed to the lengthened tongue in
such a manner as to form a tubular trunk, which cannot be
rolled up, as in the Butterflies, but is capable of efficient suction. The labial palpi are also greatly elongated.
In the H-em iptera, the " trophi " consist of four lancet-shaped
needles, which are the modified mandibles and maxillae, enclosed in a tubular sheath formed by the elongated labium
(fig. 84, 3). Lastly, in the Diptera-as in the common Housefly-there is an elongated labium, which is channelled on its
upper surface for the reception of the mandibles and maxille,
these being modified into bristles or lancets.
The mouth in the Masticating Insects leads by a pharynx
and cesophagus into a membranous, usually folded, stomach
-the " crop," or "ingluvies "-from which the food is transmitted to a second muscular
stomach, called the "gizzard"
(fig. 85).  The gizzard is adapted for crushing the food, often
v                  having plates or teeth of chitine
developed in its walls, and is
succeeded by the true digestive,d             cavity, called the "chylific sto-........'~' rmach" (ventriculus chylo7poietiCu1s).   From  this an intestine
of variable length proceeds, its
edf~ 1}  >   Vi          terminal portion, or rectum,
opening into a dilatation which
is common to the ducts of the
generative organs, and is termed
the "cloaca."  The oesophagus
is furnished with salivary glands
of varying size and complexity,
and is provided in some of the
Suctorial Insects with a dilatation called the "sucking stomach."   Behind the pyloric
aperture of the stomach, with
very few exceptions, are a variFig. 85.-Digestive system of a Beetle  able number of c cal, convo(CarbGis aurantus). a (Esophagus  b able number of cmcal, convo
Crop; c Gizzard; dChylific stomach; luted tubes (fig. 85, e), which
e Malpihgian tubes: f Intestine;  g
Cloaca; A Supposed renal vessels.    open into the intestine, and are
called the " Malpighian tubes."
These are often looked upon as representing the liver, but
are by some believed to have a renal function.  If the Malpig



ANNULOSA: INSECTA.                    253
hian vessels truly perform the functions of a liver-as their
position would appear to prove —then the kidneys will be
represented by a series of cmecal tubes which are- only occasionally present, and which open into the rectum, close to the
cloaca. There are no absorbent vessels, and the products of
digestion simply transude through the walls of the alimentary
canal into the sinuses or irregular cavities which exist between
the abdominal organs. The apparatus of digestion does not
differ essentially from the above in any of the Insects; but the
alimentary canal is, generally speaking, considerably lengthened
in the herbivorous species.
There is no definite and regular course of the circulation in
the Insects. The propulsive organ of the circulation is a long
contractile cavity, situated in the back and termed the " dorsal
vessel." This is composed of a number of sacs (ordinarily
eight), opening into one another by valvular apertures, which
allow of a current in one direction only-viz., towards the head.
The blood is collected from the irregular venous sinuses which
are formed by the lacunxe and interstices between the tissues,
and enters the dorsal vessel from behind; it is then driven
forwards, and is expelled at the anterior extremity of the body.
Respiration is effected by means of "' trachea," or branched
tubes, which commence at the surface of the body by lateral
apertures called " stigmata," or " spiracles," and ramify through
every part of the animal. In structure the tracheae are membranous, but their walls are strengthened by a chitinous filament, which is rolled up into a continuous spiral coil.  In
the aquatic larvae of many insects, and in one adult insect,
branches of the tracheae are sent to temporary outgrowths
which are termed "tracheal gills," and in which the blood is
oxygenated. In all, however, except the single insect above
mentioned, these temporary external appendages fall off when
maturity is attained. The wings, also, whilst acting as locomotive organs, doubtless subserve respiration, the nervures
being hollow tubes enclosing tracheae.
The nervous system in Insects, though often concentrated
into special masses, consists essentially of a chain of ganglia,
placed ventrally, and united together by a series of double
cords or commissures.  The cephalic or "prae-cesophageal'
ganglia are of large size, and distribute filaments to the eyes
and antenna.  The post-oesophageal ganglia are united to the
preceding by cords which form a collar round the gullet, and
they supply the nerves to the mouth, whilst the next three
ganglia furnish the nerves to the legs and wings.  In larvae,
thirteen pairs of ganglia, one to each segment, can be recog



254             MANUAL OF ZOOLOGY.
nised. In the imago, however, of the Coleoptera, several of
these primitive ganglia have coalesced, so that this number is
considerably reduced.
The organs of sense are the eyes and antennae. The eyes
in Insects are usually "compound," and are composed of a
number of hexagonal lenses, united together, and each supplied
with a separate nervous filament. Besides these, simple eyes
— " ocelli," or "stemmata" - are often present, or, in rare
cases, may be the sole organs of vision. In structure these
resemble the single elements of the compound eyes. In a few
cases the eyes are placed at the extremities of stalks or peduncles, but in no case are these peduncles movably articulated
to the head, as is the case in the Podophthalmous Crustaceans.
The antennae are movable, jointed filaments, attached usually
close to the eyes, and varying much in shape in different Insects. They doubtless discharge the functions of tactile organs,
but are probably the organ of other more recondite senses in
addition.
The sexes in Insects are in different individuals, and most
are oviparous.  Generally speaking, the young insect is very
different in external characters from the adult, -and it requires
to pass through a series of changes, which constitute the " metamorphosis," before attaining maturity. In some Insects, however, there appears to be no metamorphosis, and in some the
changes which take place are not so striking or so complete as
in others. By the absence of metamorphosis, or by the degree
of its completeness when present, Insects are divided into
sections, called respectively Amefabola, He-nimetabola, and
Holometabola, which, though not, perhaps, of a very high scientific value, are nevertheless very convenient in practice.
Section I. Amelabolic Insects.-These pass through no metamorphosis, and also, in the mature condition, are destitute of
wings. The young of these insects (Aptera) on escaping from
the ovum resemble their parents in all respects except in size;
and though they may change their skins frequently, they undergo
no alteration before reaching the perfect condition, except that
they grow larger.
Section 2. Hemimetabolic Insects.-In the insects belonging
to this section there is a metamorphosis consisting of three
stages. The young on escaping from the ovum is termed the
"larva;" when it reaches its second stage it is called the
"pupa," or " nymph;" and in its third stage, as a perfect
insect, it is called the "imago."  In the He-emiretabola, the
"larva," though of course much smaller than the adult, or
"imago," differs from it in little else except in the absence of




ANN ULOSA: INSECTA.                   255
wings. It is active and locomotive, and is generally very like
the adult in external appearance.  The "pupa," again, is a
little larger than the larva, but really differs from it in nothing
else than in the fact that the rudiments of wings have now
appeared, in the form of lobes enclosed in cases. The " pupa "
is still active and locomotive, and the term " nymph " is usually
applied to it. The pupa is converted into the perfect insect,
or "imago," by the liberation of the wings, no other change
being requisite for this purpose.  From the comparatively small
amount of difference between these three stages, and from the
active condition of the pupa, this kind of metamorphosis is
said to be "incomplete."
In some members of this section however — such as the
Dragon-flies-the larva and pupa are aquatic, whereas the
imago leads an aerial life. In these cases there is necessarily
a considerable difference between the larva and the adult; but
the larva and pupa are closely alike, and the latter is active.
Section 3. flolometabolic Insects. -These — comprising the
Butterflies, Moths, Beetles, &c.-pass through three stages
which differ greatly from one
another in  appearance, the
metamorphosis, therefore, being said to be "complete."
In these insects (fig. 86) the
"larva" is vermiform, seg-                d 
mented, and usually provided
with locomotive feet, which
do not correspond with those
of the adult, though these
latter are usually present as
well (fig. 86). In some cases
the larva is destitute of legs,
or is "apodal."  The larva is
also provided with masticatory organs, and usually eats
voraciously.  In this stage of
the metamorphosis the larvae
constitute what are usually
called  " caterpillars "  and
"grubs."   Having remained
in this condition for a longer  Fig. 86.-Metamorphosis of the Magpieor shorter length of time, and   moth (Phalcnagrossultzriata).
having undergone repeated changes of skin, or " moults," necessitated by its rapid growth, the larva passes into the second
stage, and becomes a "pupa."  The insect is now perfectly




2 56            MANUAL OF ZOOLOGY.
quiescent, unless touched or otherwise irritated; is incapable of
changing its place; and is often attached to some foreign object.
This constitutes what-in the case of the Lepitlotera —is generally known as the "chrysalis," or "aurelia" (fig. 93). The
body of the pupa is usually covered by a chitinous pellicle,
which closely invests the animal. In some cases (e g., in many
I)ipterous insects) no traces can be detected in the pupa of the
future insect; but in the Lepidoptera the thorax and abdomen
are distinctly recognisable in the pupae; whilst in others (e.g.,
Hymenoptera) the parts of the pupa are merely covered by a
membrane and are quite distinct. In some cases the pupa is
further protected within the dried skin of the larva; and in
other cases the larva-immediately before entering upon the
pupa-stage —spins, by means of special organs for the purpose,
a protective case, which surrounds the chrysalis, and is termed
the " cocoon."
Having remained for a variable time in the quiescent pupastage, and having undergone the necessary development, the
insect now frees itself from the envelope which obscured it,
and appears as the perfect adult, or "imago," characterised by
the possession of wings.
SEXES OF INSECTS.-The great majority of Insects, as is the
case with most of the higher animals, consist of male and
female individuals; but there occur some striking exceptions
to this rule, as seen in the Social Insects.  In those organised
communities which are formed by Bees, Ants, and Termites,
by far the greater number of the individuals which compose
the colony are either undeveloped females, or are of no fully
developed sex.  This is the case with the workers amongst
Bees, and the workers and soldiers amongst Ants and Termites.
And these sterile individuals, or "neuters," as they are commonly called, are not necessarily all alike in structure and
external appearance. Amongst the Bees all the neuters resemble one another; but amongst Ants and Termites they are
often divided into " castes," which have different functions to
perform in the general polity, and differ from one another
greatly in their characters.
In all the above-mentioned insects the males are relieved
from the performance of any of the duties of life except that
of propagating the species; and the females-which are generally solitary in each community-fulfil no other function save
that of laying eggs. All the other duties which are necessary
for the existence of the community are performed by the
workers, or neuters.
The organs of the two sexes are in no case united in the




ANNULOSA: INSECTA.                 257
same individual, or, in other words, there are no hermaphrodite insects.  (In some very abnormal cases amongst Bees
hermaphrodite individuals have been observed.) As has been
noticed, however, before, asexual reproduction is by no means
unknown amongst the Insecta, and the attendant phenomena
are often of extreme interest.-(See Introduction.)
The great majority of insects, during their adult condition,
are terrestrial or aerial in their habits, but in many cases, even
of these, the larvae are aquatic. Many other insects live habitually during all stages of their existence in fresh water. A few
insects inhabit salt water (either the sea itself or inland salt
waters) during the whole or a portion of their existence. (This
is the case with two or three Beetles of the families lv-ydrothilide and Dytiscidce, some Hemipterous Insects, and the larvae
of various DI>ptera.) Lastly, many insects live parasitically
upon the bodies of Birds or Mammals, or upon other Insects.
CHAPTER XL.
DIVISIONS OF INSECTA.
THE class Insecta includes such an enormous number of species,
genera, and families, that it would be impossible to treat of
these satisfactorily otherwise than in a treatise especially devoted to Entomology.  Here it will be sufficient to give
simply the differential characters of the different orders, drawing attention occasionally to any of the more important points
in connection with any given family.
As already said, the Insecta are divided into three divisions,
termed Ametabola, Henminetaboabo, and Holometabola, according
as they attain the adult condition without passing through a
metamorphosis, or have an incomplete or complete metamorphosis. The Insects which come under the first head (viz.
Ametabola) are not furnished with wings in the adult condition,
and the three orders which compose this section are commonly grouped together under the name Aptera. By some,
however, this division is entirely rejected, and the three orders
in question are placed amongst the Henemimetabola, or even
grouped with the Myriapoda.
SUB-CLASS I. AMETABOLA.-Young not passing through a
metamorphosis, and differingfro n the adult in size only. Imago
destitute of wings; eyes simple, sometimes wanting.




258              MANUAL OF ZOOLOGY.
ORDER I. ANOPLURA.-Minute Aptera, in which the mouth
is formed for suction; and there are two simple eyes, or
none.
This order comprises insects which are commonly parasitic
upon man and other animals, and are known as Lice (Pediculi).
The common Louse is furnished with a simple eye, or ocellus,
on each side of a distinctly differentiated head, the under surface of which bears a suctorial mouth. There is little distinction between the thorax and abdomen, but the segments of
the former carry three pairs of legs. The legs are short, with
short claws or with two opposing hooks, affording a very firm
hold. The body is flattened and nearly transparent, composed
of eleven or twelve distinct segments, and showing the stigmata very plainly. The young pass through no metamorphosis,
and their multiplication is extremely rapid. Most, if not all,
Mammals are infested by Lice, each having generally its own
peculiar species, and sometimes having two or three. Three
species are said to belong to Man-viz., Pediculus hzumanus,
P. capitis, and P. pubis.
ORDER II. MALLOPHAGA. - Minute Aptera, in which the
mouth is formed for biting, and is furnished with mandibles
and maxillae.
The members of this order are commonly known as " Birdlice," being parasitic, sometimes upon Mammals, but mostly
upon Birds. They strongly resemble the Pediculi, but the
mouth is formed for biting, to suit their mode of life-since
they do not live upon the juices of their hosts, but upon the
more delicate tegumentary appendages.
ORDER III. THYSANURA.-Aptlerous insects, usually with a
masticatory mouth, and having the extremity of the abdomen
furnished with locomotive appendages.
The most familiar members of this order are the Podurae, or
"Spring-tails," which are characterised by the possession of a
forked caudal appendage, by the extension of which considerable leaps can be effected.  In the nearly allied Lepismae, locomotion is assisted by caudal bristles. In both, the body is
covered with hairs or scales, the structure of the latter being
often very beautiful.
SUB-CLASS II. HEMIMETABOLA.-Metamorphosis incomplete;
the larva diferingfrom the imago chiefly in the absence of wings,
and in size; pupa usually active, or, if quiescent, capable of movement. i
* The'occidae, amongst the Hemiptelera, undergo a complete metamorphosis. In certain of the Hemriptera and Orthoptera the adult is apterous,
and in these cases there cannot be said to be any metamorphosis, since




ANNULOSA: INSECTA,                      259
ORDER IV. HEMIPTERA.-Mouth suctorial, beak-shaped,
consisting of a jointed rostrum, composed of the elongated
Fig. 87.-Hemiptera. Bean Aphis (Alhisfabe), winged male and wingless female.
labium, which forms a jointed, tubular sheath for the bristleshaped styliform  mandibles and maxillae.  Eyes compound,
usually with ocelli as well. Two
pairs of wings in most; sometimes
wanting.
The Henziptera live upon the juices
of plants or animals, which they are
enabled to obtain by means of the
suctorial rostrum. Amongst the more
familiar examples of this order are
the Plant-lice (Aphides, fig. 87), the
Field-bug (Pentaltoma), the Boat-fly
(Notonecta), the Cochineal Insects
(Cocci), and the Cicadas. The order
is divided into the following two
sub-orders:Sub-order a. Homoptera. —The
anterior pair of wings of the
same   texture  throughout
(membranous); the  mouth
turned backwards, so  that
the beak springs from  the
back of the head. The wings
fold over one another when
the insect is at rest.   The
three segments of the thorax
are united in a mass, and the
pro-thorax is generally shorter Fig. 88. —Orthoptera  The cob
thanthe meso-thorax. Ther mon Cockroach (Blatta orientathan the meso-thorax. There   Us) male andfemale.
the larvae differ from the adult only in size, in having fewer joints to the
antennae, and in having a smaller number of facets in each of the compound eyes.




260             MANUAL OF ZOOLOGY.
are ocelli between the compound eyes, and the antennae
are small and composed of few joints. The females
have an ovipositor of three toothed blades.  In this
section are the Aphides, the Scale Insects (CoccidaR),
the Cicadas, the Lantern-flies (Fuzrora), &c.
Sub-order b. Heteroptera. — Anterior wings membranous
near their apices, but chitinous towards the base
(hemelytra); the rostrum springing from the front of
the head. The inner margins of the wings are straight
or contiguous. The antenna: are moderate in size, and
composed of a few large joints. The pro-thorax is the
largest segment of the thorax. They are divided into
the two groups of the Hydrocorisce (Water-bugs) and
Geo.orisce (Land-bugs), according as they are aquatic or
mainly terrestrial in their habits.
ORDER V. ORTHOPTERA.-Mouth masticatory; wings four,
sometimes wanting; tne anterior pair mostly smaller than the
posterior, semi-coriaceous or leathery, usually with numerous
nervures, the interspaces between which are filled with many
transverse reticulations; sometimes overlapping horizontally
(Cockroach), sometimes meeting like the roof of a house
(Grasshoppers).  Posterior. wings usually having their front
portion of a different texture from their hinder portion, this
latter being almost always more transparent, and when not in
use, folded longitudinally like a fan. Posterior wings mostly
wanting in the females of the Blaftid&e.  Antennae usually
filiform. Metamorphosis semi-incomplete (sometimes, however, the adult is apterous, when it becomes almost impossible
to distinguish the larva, pupa, and imago).
This order includes the Crickets (Achetina), Grasshoppers
(Gryllina), Locusts (Locustina), Cockroaches (B/attina, fig. 88),
&c. Some of them are formed for running (cursorial), all the
legs being nearly equal in size; whilst in others the first pair
of legs are greatly developed, and form powerful raptorial
organs, as in the Mantis. In others, again, as in the Grasshoppers and Crickets, the hindmost pair of legs are greatly
elongated, so as to give a considerable power of' leaping to
them. All the Orthoptera are extremely voracious, and the
ravages caused by locusts in hot countries are well known to
all. The most destructive of the Locusts is the Migratory
Locust (Acrydium migratorium, fig. 89) of Africa and Southern
Asia. This formidable species is celebrated for the destruction which it causes in certain seasons in the countries in
which it occurs, a destruction against which human art has
hitherto proved wholly powerless. Vast hordes of this species




ANNULOSA: INSECTA.                      26i
descend suddenly upon a district, and in a few hours destroy
all crops, and devour the leaves of all the trees, migrating as
suddenly as they came, so soon as the ground is utterly bare.
j- 
Fig. 89.-Migratory Locust (Acryiumz mzigratorirzum).
ORDER  VI. NEUROPTERA. —Mouth usually masticatory;
wings four in number, all membranous, generally nearly equal
in size, traversed by numerous delicate nervures, having a
longitudinal and transverse
direction, and giving them a
reticulated, lace-like aspect.
Metamorphosis generally incomplete, rarely complete.
The larva active, hexapod,
rarely with pro-legs.
This order includes the
Dragon- flies   (Libelduide),
Caddis- flies  (Phryganeidce)
May-flies (Ephemeridce),* the
Ant- lion  (AMyrmedeo), Termites, &c.  The last of these
-namely, the Termites or
White Ants-are social, and
live in communities, and their
habits are so singular that a Fig. 9o. -Neuroptera. Aphis-lion (Hemerobiidre), imago, larva, and eggs.
short description of them will
not be out of place here. They are mostly inhabitants of hot
countries, where they are commonly known as " White Ants;"
but it must be borne in mind that they have nothing to do
with the insects commonly called Ants, which belong, indeed,
to a different order (Hymenoptera).  The following account is
* By some the Dragon-flies (Libelulidae), the May-flies (Epherneride),
and the Termites (Termitid&e), are placed in the Orthopfera, under the
common name of Pseudo-neuroptera; whilst the Caddis-flies (Phryganeidae)
form a separate order under the name of Ti-ichoptera.




262              MANUAL OF ZOOLOGY.
taken from Mr Bates's work on the Amazons, where there is
an excellent description of the habits of these remarkable
insects.
Termites are small, soft-bodied insects, which live in large
communities, as do the true Ants. They differ, however, from
the Ants in the fact that the workers are individuals of no
fully developed sex, whereas amongst the latter they are undeveloped females.  Further, the neuters of the Termites are
always composed of two distinct classes or "castes"- the
workers and the soldiers. Lastly, the Ants undergo a quiescent
pupa-stage; whereas the young Termites, on their emergence
from the egg, do not differ from the adult in any respect except
in size.
Fig. gI.-Termites (Termes bell'cosuts); a King, before the wings are cast off; b Queen,
with the abdomen distended with eggs; c Worker; d Soldier.
Each species of Termites consists of several distinct orders
or castes, which live together, and constitute populous, organised communities.   They inhabit structures known  as
" Termitaria," consisting of mounds or hillocks, some of which
are " five feet high, and are formed of particles of earth worked
into a material as hard as stone." The Termitarium has no
external aperture for ingress or egress, as far as can be seen,
the entrance being placed.at some distance, and connected
with the central building by means of covered ways and
galleries.  Each Termitarium  is composed of "a vast number of chambers and irregular intercommunicating galleries,
built up with particles of earth or vegetable matter, cemented
together with the saliva of the insects." Many of "the very
large hillocks are the work of many distinct species, each of




ANNULOSA: INSECTA.                 263
which uses materials differently compacted, and keeps to its
own portion of the tumulus."
A family of Termites consists of a king and queen, of the
workers, and of the soldiers. The royal couple are the parents
of the colony, and "are always kept together, closely guarded
by a detachment of workers, in a large chamber in the very
heart of the hive, surrounded by much stronger walls than the
other cells. They are both wingless, and immensely larger
than the workers and soldiers.  The queen, when in her
chamber, is always found in a gravid condition, her abdomen
enormously distended with eggs, which, as fast as they come
forth, are conveyed by a relay of workers in their mouths
from the royal chamber to the minor cells dispersed through
the hive."
At the beginning of the rainy season a number of 7winged
males and females are produced, which, when they arrive at
maturity, leave the hive, and fly abroad. They then shed their
wings (a special provision for this existing in a natural seam
running across the root of the wing and dividing the nervures);
they pair, and then become the kings and queens of future
colonies.
The workers and the soldiers are distinct from the moment
of their emergence from the egg, and they do not acquire
their special characteristics in consequence of any difference
of food or treatment. Both are wingless, and they differ solely
in the armature of the head. The duties of the workers are to
" build, make covered roads, nurse the young brood from the
egg upwards, take care of the king and queen, who are the
progenitors of the whole colony, and secure the exit of the
males and females when they acquire wings and fly out to
pair and disseminate the race." The duties of the soldiers are
to defend the community from all attacks which may be made
upon its peace, for which purpose the mandibles are greatly
developed.
It may well be admitted, that in such organised communities
as those of the Termites, we have the highest development of
Insect-life yet known to us. The principle of the division of
labour is carried out to its fullest extent-much further, indeed,
than is possible amongst human beings,-since the perfection
of the greater number of the individuals which compose the
community-as organisms-is sacrificed in order to secure the
fulfilment of the duties which are necessary for the existence
and welfare of the whole. Even the task of perpetuating the
species, and of giving origin to fresh colonies, is entirely left
to one class of the community, the defence and protection of




264             MANUAL OF ZOOLOGY.
which is the special object and care of the remainder. No
higher development could well be imagined amongst creatures
devoid of the higher psychical endowments; and it is worthy
of note that at least three distinct and independent families of
Insects have attained to this stage-namely, the Termites, the
Bees, and the true Ants.
SUB-CLASS III. HOLOMETABOLA. -Metamoryphosis complete;
the larva, pzupa, and imago diffiring greatly from one another in external appearance.  The larva vermiform, and the pozqa quiescent.
ORDER VII. APHANIPTERA. -Wings rudimentary, in the
form of plates, situated on the meso-thorax and meta-thorax.
Mouth suctorial. Metamorphosis complete.
This order comprises the Fleas (Pulicidie), most of which
are parasitic upon different animals. The larva of the common
Flea is an apodal grub, which in about twelve days spins a
cocoon for itself, and becomes a quiescent pupa, from which
the imago emerges in about a fortnight more. Besides the
common Flea (Pulex irritans), another well-known and considerably more troublesome member of this order is the Chigoe
(Pulexpenetrans) of the West Indies and South America.
ORDER VIII. DIPTERA.-The anterior pair of wings alone
developed; the posterior pair of wings rudimentary, represented. by a pair of clubbed filaments, called "halteres," or "balancers" (fig. 92).  In a few the wings are
altogether wanting.  Mouth suctorial.  The metamorphosis
is complete, the larvae being generally destitute of feet; but
in some cases (e.g., the gnats) the pupae are aquatic and are
actively locomotive.  In most cases, however, the pupae are
quiescent.
The proboscis in the Diptera consists of a tubular labium,
enclosing the other parts of the mouth, and is placed on the
under surface of the head.  Ocelli are present in addition to
the compound eyes. The wings are generally horizontal and
transparent, the nervures not very numerous, and for the most
part longitudinally disposed.  The antennae are generally
small and three-jointed, sometimes many-jointed (Tzuidae),
or feathery (Culicidee).  The larva is soft and fleshy, with a
soft indistinct head, usually apodal, never with thoracic legs,
and rarely with pro-legs..The larval skin mostly forms a
hardened case for the pupa, but the larvae sometimes cast
their skin when becoming pupae, or even spin cocoons.  In
some the eggs are hatched within the body of the mother, so
that the insect appears first in the larval state; and in Pupip2ara
not only is this the case, but the larvae continue to reside with.
in the mother until they become pupae.




ANNULOSA: INSECTA.                   265
The DiPtera constitute one of the largest of the orders of
the Insecta; the House-flies and Flesh-flies (Mfusca), Gnats
(Culex), Forest-flies (Hzippobosca), Crane-flies (i2pjulidgz), and
Gad-flies (Tabanide), constituting good examples.
Fig. 92.-Diptera. Crane-fly (Tifiula oleraca).
ORDER IX. LEPIDOPTERA.-Mouth suctorial, consisting of
a spiral trunk or " antlia," composed of the greatly-elongated
maxillae, and protected, when not in use, by the cushion-shaped
hairy labial palpi. Maxillae forming two sub-cylindrical tubes,
united together by inosculating hooks, and constituting an intermediate tube by their junction. Maxillary palpi minute;
labrum and mandibles rudimentary. Head, thorax, and abdomen more or less covered with hair. Wings, four in number, covered with modified hairs or scales; wanting in the
females of a few species. Nervures not very numerous, mostly
longitudinal. Antenne almost always distinct, and composed
of numerous minute joints.
This well-known and most beautiful of all the orders of
Insects comprises the Butterflies (fig. 93) and the Moths (fig.
94); the former being diurnal in their habits, the latter mostly
crepuscular or nocturnal.
The larvae of Lepidopfera (fig. 94), commonly called "cater.
pillars," are vermiform in shape, normally composed of thirteen
segments, the anterior portion forming a distinct horny head,




266              MANUAL OF ZOOLOGY.
with antennae, jaws, and usually simple eyes. The mouth of
the caterpillar, unlike that of the perfect insect, is formed for
mastication. The labium also is provided with a tubular organ
-the "spinneret"-which communicates with two internal
glands, the functions of which are to furnish the silk, whereby
the animal constructs its ordinary abode or spins its cocoon.
The three segments behind the head correspond with the prothorax, meso-thorax, and meta-thorax of the perfect insect, and
each carries a pair of jointed walking-legs.  Besides these
thoracic legs, there is a variable number, (generally ten) of soft
fleshy legs, which are borne by the segments of the abdomen,
and are known as "pro-legs." Each is usually furnished with
a crown of small horny hooks, and they are never attached to
the 4th, 5th, Ioth, and i Ith abdominal segments.
Fig. 93.-Large White Cabbage Butterfly (Pontia brassica). a Larva or caterpillar;
b Pupa or chrysalis; c Imago or perfect insect.
In the Diurnal Lepidojptera, or Butterflies proper (fig. 93),
the antennae are knobbed; the wings are usually held erect
when the insect is. in a state of repose; the larvae have six
thoracic legs, and ten pro-legs; and the pupae are always
naked, attached by the posterior extremity or head downwards,
and usually angular.
In the Crepuscular -Lejidoptera, including those forms which
are active during the twilight, the antennae are fusiform, or
grow gradually thicker from the base to the apex; the wings
are horizontal or little inclined when the insect is at rest; the
posterior wings have their front margins furnished with a rigid




ANNULOSA: INSECTA.                 267
spine ("retinaculum") which is received into a hook on the
under surface of the anterior wings; and the pupae are never
angular.
Fig. 94. —Goat-moth (Cossus liznipei-da) and Caterpillar.
The Nocturnal Lejidoptera have the antennae setaceous, or
diminishing gradually from the base to the apex, often serrated
or pectinated (fig. 94); the wings in repose are horizontal or
deflexed, and the hind-wings are furnished with a "retinaculum,"
as in the preceding section; the pupae are mostly smooth,
sometimes spiny, and often enclosed in a cocoon.
ORDER X. HYMENOPTERA. —Wings four, membranous, with
few nervures; sometimes absent.   Mouth always provided
with biting-jaws, or mandibles; the maxillae and labium often
converted into a suctorial organ.  Females having the extremity of the abdomen mostly furnished with an ovipositor
(terebra or aculeus), consisting chiefly of three elongated processes, of which two serve as a sheath for the third.  Besides
the compound eyes, there are usually three ocelli placed on
the top of the head. The antennae are generally filiform or
setaceous. The metamorphosis is complete, but the various
parts of the pupa are visible through the delicate enclosing
13




268              MANUAL OF ZOOLOGY.
membrane. The larvae are sometimes provided with feet, and
live on vegetable food (as in the Tenthredinide, fig. 95); but
they are mostly footless, without a distinct head, and fed by
the adult.
The Hymenoplera form a very extensive order, comprising
the Bees, Wasps, Ants, Ichneumons, Saw-flies (fig. 95), &c.
KY
Fig. 95.-Gooseberry Saw-fly (Tenthredo grossularie), larva, pupa, and imago.
The ovipositor, which is very generally present in the females
of this order, is sometimes a boring organ (terebra), or in other
cases a " sting" (aculeus).
Amongst the Hymenoptera we find social communities, in
many respects resembling those of the Termites, of which a
description has already been given.  The societies of Bees
and Ants are well known, and merit a short description.
The social Bees, of which the common Honey-bee (Apis
melifica) is so familiar an example, form organised communities,
consisting of three classes of individuals-the males, females,
and neuters.  As a rule, each community consists of a single
female-" the queen"-and of the nduters, or " workers."  The
impregnation of the female is effected by the production of
males, or "drones," during the summer. After impregnation




ANNULOSA: INSECTA.                  269
has been effected, the drones, as being then useless, are destroyed by the workers. The eggs produced by the fecundated
queen are mostly intended to give origin to neuters, to which
end they are placed in the ordinary cells. The ova which are
to give origin to females-the "queens" of future coloniesare placed in cells of a peculiar construction, and the larvae
are fed by the workers with a special food.  The ova which
are to produce males are likewise placed in cells, which are
slightly larger than those allotted to the workers.  It is asserted, however, that this is not the sole or true cause of the
production of the males; but that the ova which are intended
to produce drones are not fertilised by the female with the
semen which she has stored up in her spermatheca, and are
therefore produced by a process of Parthenogenesis. That
the males are produced parthenogenetically in some, at any
rate, of the Hymenoptera, appears to have been placed beyond
a reasonable doubt by the researches by Von Siebold.-(See
Introduction.)
In the Humble-bees (BombiZe), and in the Wasps (Vespidce),
we have societies essentially the same as in the Honey-bee.
In a large community of Wasps, or " vespiary," there may be
several hundred females, of which few survive the winter, and
live to found fresh colonies next spring. The number of males
is about equal to that of the females, but, unlike the drones of
the Bees, the males work actively and defend the nest. As
amongst the Bees, solitary species are not uncommon.
The Ants (Formicire) likewise form communities, consisting
of males, females, and neuters (fig. 96).  The males and
Fig. 96. —ed Aalt (, Tyrmzica rntz). a Winged male; b Wingless neuter.
MIuch magnified.
females, as we have seen in the case of the Termites, are
winged, and are produced in great numbers at a particular
period of the year.  They then quit the nest and pair, after




270             MANUAL OF ZOOLOGY.
which the males die. The females then lose their wings and
fall to the ground, when they become thle queens of fresh
societies. In some Ants, as in the Termites, the neuters are
divided into two classes-the workers and the soldiers-of
which the former perform all the duties necessary for the preservation of the society except defending the nest, this being
left to the soldiers. In other cases, as many as three distinct
orders or "castes" of neuters may be present in the same
nest.
Amongst the more singular of the habits and instincts of
Ants two may be mentioned-the instinct of making slaves,
and that of milking, so to speak, the little Plant-lice (Aphides).
As regards the first of these, it is found that certain Ants possess the extraordinary instinct of capturing the pupae of other
species of Ants, and bringing them up as slaves. The relations between the master and the slaves vary a good deal in
different species.  In the case of Formica rufescens, for instance,
the masters are entirely dependent upon their slaves; the
males and females do nothing except reproducing the species,
and the neuters perform no other labour except that of capturing fresh slaves.  The masters are in this case unable even to
feed themselves, and their existence is maintained entirely by
the devotion of the slaves.  In Formica sanguinea, on the
other hand, the number of slaves is much less, and both
masters and slaves occupy themselves in performing most of
the duties necessary for the community. The masters, however, go alone when on slave-making expeditions; and in case
of a migration, the masters carry the slaves in their mouths.
A second singular fact in the history of Ants is found in the
relations which subsist between them and the Aphides, or
Plant-lice.  The Aphides secrete, or rather excrete, a peculiar
viscid and sweet liquid, by means of a gland which is situated
towards the extremity of the abdomen, and communicates with
the exterior by two tubular filaments. Ants are extremely fond
of this excretion, and it is a well-established fact that the
Aphides allow themselves to be milked, as it were, by the Ants.
For this purpose the Ant touches and caresses the abdomen
of the Aphis with its antennae, whereupon the latter voluntarily
exudes a drop of the coveted fluid. Ordinarily the Ants seek
the Aphides upon plants; but it is asserted that in some cases
they keep Aphides, much in the same way as human beings
keep cows-though this is probably partly imaginary.
ORDER XI. STREPSIPTERA.-Females without wings or feet,
parasitic.  Males possessing the posterior pair of wings, which
are large, membranous, and folded longitudinally like a fan.




ANNULOSA: INSECTA.                     27 
The anterior pair of wings rudimentary, represented by a pair
of singular twisted organs. Jaws abortive.
The Strepsiptera con'stitute a small order, which includse
certain parasites of minute
size, found on Bees and
other Hymenoptera.   The
female is a soft vermiform
grub, without feet, but with
a horny head, which it protrudes from  between the
abdominal segments of its
host. The larvae are active,
and possess six feet; whilst
the  males  (fig. 97) are
winged, and fly about with
winged, andflyaboutwi  Fig. 97.-Strepsiptera. Stylos Sjencii,
OrDea   activity. COLgreatly magnified (after Westwood).
ORDER XII. COLEOPTERA.-Mouth masticatory, furnished with an upper lip or
labrum, two mandibles, two maxilla, with maxillary palpi
(generally four-jointed), and a movable lower lip or labium,
with two jointed labial palpi.  The four wings are usually
present, and the anterior pair are not adapted for flight, but
are hardened by chitine, so as to form protective cases (elytra)
for the posterior wings (fig. 98).  The inner margins of the
Fig. 98.-Coleoptera. Common Cockchafer (.elolontha vulgarzs).
elytra are generally straight, and when in contact they form a
longitudinal suture.  The posterior wings are membranous,
and when not in use, are folded transversely beneath the
elytra. (Amongst deviations from this state of parts may be
mentioned the occasional absence or rudimentary condition
of the hinder wings, the soldering together of the elytra, the




272              MANUAL OF ZOOLOGY.
soft and yielding condition of the elytra, or th'e absence of
both elytra and wings).  The eyes are always compound,
generally circular, oval, or reniform, but sometimes completely
divided. The antennae are extremely variable in form, generally of eleven joints, sometimes of fewer, rarely of twelve.
The thorax is composed of a pro-meso- and meta-thorax, but
when the elytra are closed, only the pro-thorax and a little
plate (" scutellumn") belonging to the meso-thorax are visible.
The tarsus is generally composed of five joints, sometimes
fewer, never more, and its last joint is usually furnished with
two hooked claws.
Fig. 99.-a Rose-chafer (Cetonia aurata) and larva; b Vine-weevil
(Curczlio szucatus).
The larvae of Coleoptera are generally composed of thirteen
segments, including the head. The body is generally soft and
fleshy, the head horny, and the mouth adapted for mastication.
The antennae are small, usually of three or four joints, with
ocelli at their base. They have three pairs of legs attached to
the thorax, and sometimes anal pro-legs or fleshy tubercles.
The pupa is sometimes enclosed in a cocoon, and the parts
of the perfect insect are always distinctly recognisable in the
pupa.
The order Coleoptera includes all those insects commonly
known as "Beetles," and comprises an enormous number of
genera and species. They are remarkable, as a general rule,
for their hard polished integument, their glittering, often metallic colours, and their voracious habits. They are grouped
by Latreille in the following four sections:



ANNULOSA: INSECTA.                      273
i. Pentamera.-Tarsus five-jointed.
2. -ieteromnera.-Tarsus of two anterior pairs of legs fivejointed, of the posterior pair four-jointed.
3. 7elramera.-Tarsus four-jointed.
4. Trimera. —Tarsus three-jointed.
DISTRIBUTION OF INSECTA IN TIME.-The earliest known
insects have been discovered in the Devonian Rocks of
America, and consist of the remains of Nezroptera.o    Others,
as might have been anticipated, have been found in the Coalmeasures. In the Secondary Rocks remains of insects have
been found abundantly in certain beds of the Oolitic and Liassic
formations. In some Tertiary strata Lepidoptera and other insects have been found in a good state of preservation. Amber,
which is a fossil resin, has long been known to contain many
insects in its interior (in certain specimens); and all of these
appear to belong to extinct species, though amber, geologically
speaking, is not an ancient product.
* The Devonian ANeuroapera of North America are most closely allied to
the Ephemeride; but one form is in many respects transitional between
the orders Orthaoptera and Neurofptera. Insects belonging to the Neuroatera (viz., Miamia and Hemerislia), to the Orthoptera (Blattina), and to the
Iemiptera (Eugereon), have also been described from the Carboniferous
Rocks of North America.




M OL L USCA.
CHAPTER XLI.
SUB-KINGDOM MOLL U SCA.
SUB-KINGDOM MOLLUSCA.-The Mollusca may be defined as including soft-bodied animals, which are usually provided with an
exoskeleton. The intestinal canal is bounded by its own proper
walls, and is completely shut off from the perivisceral cavity.
The alimentary canal is situated between the hbemal system,
which lies dorsally, and the neural system, which is situated
towards the ventral aspect of the body. The nervous system
(fig. Ioo) in its highest development consists of three
principal ganglia, which are
reduced to one in the lower
forms.  Usually there is a
a.            at _distinct propulsive  organ
by which the circulation is
carried on, but this is ocf        n'             casionally absent. Distinct
respiratory organs may or
Fig. oo.-Diagram of a Mollusc. a Alimen-  pres    ents   Re
tary canal; h Heart; f Foot; n Cerebral   ay not be present.  Reganglion; n' Pedal ganglion; i" Parieto-  production is sexual, though
splanchnic ganglion.            gemmation  is also occasionally superadded. The higher Mollusca are all simple animals, but many of the lower forms are capable of forming
colonies by continuous gemmation.
The digestive system in all the Mollusca consists of a mouth,
gullet, stomach, intestine, and anus-though in some of the
Brachiofoda; and in a few other forms, the intestine ends
cxecally. In some the mouth is surrounded by ciliated tentacles (Polyzoa, fig. 102); in others it is furnished with two
ciliated arms (Brachivpo5oda, fig. I05); in the bivalves (Lame/libranchiata) it is mostly furnished with four membranous pro
cesses or palpi (fig. Io6); in others it is provided with a com.
plicated apparatus of teeth (Gasteropoda, fig. Io8, and Ptero




MOLLUSCA: GENERAL CHARACTERS.                  275
poda); and, lastly, the Cephalopoda have, in addition, horny or
calcareous mandibles, forming a kind of beak. Well-developed
salivary glands are usually present; the liver in the higher
forms is of large size, and pours its secretion either into the
stomach or into the commencement of the intestine; and a
renal organ has been detected in most of the Mollusca proper.
There is no distinct absorbent system, but the products of
digestion pass by exosmose into the general abdominal cavity,
and thence into the larger veins, which are sometimes pierced
by numerous round holes for this purpose.
The blood is colourless, or nearly so. In the Polyzoa the
circulation is carried on by ciliary action, and there is no distinct propulsive organ, or definite course of the circulating
fluid. In the lunicata the heart is a simple tube, open at both
ends, and the course of the circulation is periodically reversed.
In the Brachiopoda the course of the circulation is not definitely ascertained, and it is doubtful if a true heart is present
in all.  In the higher Mfollusca a distinct heart is always
present, and consists of an auricle which receives the aerated
blood from the breathing-organ, and a muscular ventricle
which propels it through the systemic vessels. That a system
of capillaries in many cases intervenes between the arteries
and veins, appears from recent researches to be probable.
In all cases the heart of the Mollusca is systemic, distributing
the aerated blood to the body, and in no case is it respiratory,
propelling the non-aerated blood to the breathing-organ.
In the Polyzoa there is no differentiated respiratory organ,
and the function of respiration is discharged mainly by the
oral crown of ciliated tentacles.  In the Tunicala respiration
is effected by means of the pharyngeal or branchial sac; and
in the Brachiopovda by the oral arms, and possibly, to some
extent, by an "atrial" or "water-vascular " system, furnished
with contractile dilatations.  In the higher Mol/uisca a distinct
breathing-organ is always present, a portion of the mantle being
specialised for this purpose.. In the LameZeibyranchiata, and
the branchiate Gasteroopoda, the breathing-organs are in the
form of lamellar and pectinate gills; and the same is the case
with the Cepha/lopoda.  In the pulmonate Gasteropoda, in
which respiration is aerial, a pulmonary sac or air-chamber is
produced by the folding of a portion of the mantle, over the
interior of which the pulmonary vessels are distributed.  The
chamber thus formed communicates with the exterior by a
round aperture which can be opened or closed at will; and the
renovation of the effete air within the sac appears to be effected
mainly or entirely by simple diffusion.




276             MANUAL OF ZOOLOGY.
The nervous system varies considerably in its development.
In the Polyzoa, ]zunicata, and Brach/iopoda —which collectively
constitute the AMolluscoida-the nervous system consists.of a
single ganglion, or of a principal pair with accessory ganglia,
placed between the oral and anal apertures, or on the ventral
surface of the body.  The true Molluscan type (fig. Ioo), however, of nervous system is constituted by the presence of three
pairs of ganglia, connected with one another by commissures,
but distributed in a characteristically scattered manner (heterogangliate type).  One of these ganglia is situated above the
cesophagus, and is called the "supra-cesophageal" or "cerebral"
ganglion.  A second is placed below the csophagus; and is
termed the "infra-cesophageal" or "pedal" ganglion (from its
supplying the nerves to the "foot"). The third pair is the
mlost persistent, and is termed the "branchial" or "parietosplanchnic" ganglion.
Organs of sight exist in some of the lower, and in the majority of the higher, Mollusca.  In the Cephalopoda, and in some
of the Gasteropoda (e.g. Strombidce), the eyes are of a very high
type of organisation.  In the Lamenellibranchiata the adults are
either destitute of organs of vision, or possess numerous simple
eyes (" ocelli ") placed along the margins of the mantle-lobes.
Similar ocelli are also found in some of the Tunicata, placed
between the oral tentacles.  Organs of hearing exist in the
more highly organised AMfoiusca, especially in the Gasteroyoda
and Ccrhalopoda, and supposed olfactory organs occur in some
of the latter.
Reproduction amongst the A'follusca is almost invariably
sexual, but it is by continuous gemmation that the colonies of
the Polyzoa, and the social and compounid 5Tnicala, are produced, and the " statoblasts " of the former offer a good example of non-sexual reproduction. The sexes are usually distinct, but are in many cases united in the same individual. In
many forms the ova are arranged in rows, so as to form a strap
or ribbon-shaped structure, termed the "nidarnental ribbon."
As implied by their scientific name, the Moilusca are mostly
soft-bodied animals; but their popular name of "Shell-fish"
expresses the fact, that the presence of a shell, protecting the
soft body, is likewise a very characteristic feature in the subkingdom. At the same time, a shell is not universally present,
and many of the Mollusca are either permanently naked, or
possess nothing that would be ordinarily looked upon as a
shell. When there is either no shell at all, or merely a rudimentary shell enclosed. in the mantle, the Mollusc is said to be
"naked."  The shell of the "testaceous" Aifollusca is very




MOLLUSCA: GENERAL CHARACTERS.               277
closely related to the respiratory organs; "indeed it may be
regarded as apnezumoskceeton, being essentially a calcified portion of the mantle, of which the'breathing-organ is at most a
specialised part.... In its most reduced form the shell
is only a hollow cone or plate, protecting the breathing-organ
and heart, as in Zinmax, Testacella, and Carinaria. Its peculiar
features always relate to the condition of the breathing-organ,
and in Terebratula and Pelonaia it becomes identified with the
gill.  In the Nudibranchs the vascular mantle performs, wholly
or in part, the respiratory office. In the Ceph/zalopods the shell
becomes complicated by the addition of a distinct, internal,
chambered portion (phragmacone), which is properly a visceral
skeleton."-(Woodward.)  In a great many of the Molluscaz
proper the shell consists of but a single piece, and they are
called " univalves."  In many others the shell consists of two
separate plates or "valves," and these are called "bivalves."
In others, again, as in the Chilon, the shell consists of more
than two pieces, and is said to be "multivalve." Most, however, of the multivalve shells of older writers are in reality
referable to the Cirripedia.
All the testaceous Afollusca (except the Argonaut), and
most of the " naked " forms, acquire a rudimentary shell before
their liberation from the ovum. In the latter this rudimentary
shell is cast off as the embryo grows, but in the former it becomes the "nucleus" of the adult shell.  In the bivalves the
embryonic shell or "nucleus" is situated at the beak or
" umbo " of each valve, and is often very unlike the remainder
of the shell.
In composition the shell of the Mollusca consists of carbonate of lime-usually having the atomic arrangement of calcite
-with a small proportion of animal matter.  In the Photadide, however, the calcareous matter exists in the allotropic
condition of arragonite, which is very much harder than calcite.
As regards their texture, three principal varieties of shells may
be distinguished-viz., the "porcellanous," the "nacreous,"
and the "fibrous." In the "nacreous" or pearly shells, as seen
in "mother-of-pearl," the shell has a peculiar lustre, due to
the minute undulations of the edges of alternate layers of carbonate of lime and membrane.  The "fibrous" shells are
composed of successive layers of prismatic cells. The "porcellanous " shell has a more complicated structure, and is composed of three layers or strata, each of which is made up of
very numerous plates, "like cards placed on edge." The direction in which these vertical plates are placed, is sometimes
transverse in the central layer, and lengthwise in the two




278             MANUAL OF ZOOLOGY.
others; or longitudinal in the middle, and transverse in the
outer and inner strata.
All living shells have an outer layer of animal matter, which
is known as the "epidermis," or "periostracum."   This is
sometimes of extreme tenuity, but is sometimes very thick, the
latter being especially the case with those shells which are
found in fresh water.
In many of the spiral univalves, as the animal grows it
withdraws itself from the upper portion of the shell, often partitioning off the space thus left vacant. In many instances
the portion thus abandoned falls off, and the shell becomes
" truncated," or " decollated;" this being the normal condition
in fully-grown examples of some shells.
In the great majority of univalves the shell is coiled into
a spiral, the direction of which is right-handed, but in some
cases the spiral is left-handed, and the shell is said to be "reversed," or "sinistral."  The reversed shell may occur as the
normal condition of the species, or it may occur simply as a
variety of a form which is normally right-handed, or " dextral."
The sub-kingdom MofZusca is divided into two great divisions, termed respectively the Molluscoida, and the Mollusca
proper.  In the former of these the nervous system consists of
a single ganglion or principal pair of ganglia, and there is
either no circulatory organ or an imperfect heart.  In the
latter the nervous system consists of three principal pairs of
ganglia, and there is a well-developed heart, consisting of at
least two chambers.




MOLL USCOIDA.
CHAPTER XLII.
POL YZOA.
DIVISION A. MOLLUSCOIDA. — Nervous system consisting of a
single gavnglion, or of a princizpalpair with accessory ganglia; no
distinct organ of the circulation, or an imperfect heart.
This division includes three classes-viz., the Polyzoa, the
Tunicata, and the Brachiopoda.
CLASS I. POLYZOA (Bryozoa). —The members of this class
are defined as follows:-" Alimentary canal suspended in a
double-walled sac, from which it may be partially protruded
by a process of evagination, and into which it may be again
retracted by invagination.  Mouth surrounded by a circle or
crescent of hollow, ciliated tentacles; animals always forming
composite colonies."-(Allman.)
All the Polyzoa live in an associated form in colonies or
"polyzoaria," which are sometimes foliaceous (fig. I02, I), sometimes branched and plant-like, sometimes encrusting, and very
rarely are free. Each "polyzoarium" consists of an assemblage of distinct but similar zoiids arising by continuous gemmation from a single primordial individual. The colonies thus
produced are in very many respects closely similar to those of
many of the Hydroid Polypes, with which, indeed, the Polyzoa
were for a long time classed. The "polyzoarium," however,
of a Polyzodn differs from the polypidom of a composite Hydroid in the general fact that the separate cells of the former
do not communicate with one another otherwise than by the
continuity of the external integument; whereas the zobids of
the latter are united by an organic connecting medium, or' ccenosarc," from which they take their origin.  On this
point Mr Busk observes:"It has been before said that the Polyzoa are always associated into compound growths, made up of a congeries of individuals, which, though distinct, yet retain some degree of




280             MANUAL OF ZOOLOGY.
intercommunication, comparable in kind perhaps, though not
in degree, to what obtains in many of the compound Ascidians. That this community exists is proved by the otherwise
inexplicable circumstance that the polyzoaria in many instances
present elements common to the whole growth, and not belonging specially to any individual. The chief bond of connection would appear to reside partly in the continuity of the
external integument, and partly also, in all probability, in a
slow interchange of the vital fluid with which the cavities of
the cells are charged."
In one sub-order of the Polyzoa (Ctenosomdafa), the polyzoarium consists of a series of cells arising from a common tube,
but this exception does not affect the value of the above
general distinction between the Polyzoa and the Hjydroida.
A second point of difference is found in the invariably corneous (or chitinous) texture of the polypidoms of the Hydroida,
whereas those of the Polyzoa may be corneous or fleshy, b)ut
are in the majority of instances more or less highly charged with
carbonate of lime.
The homomorphism, however, which subsists between the
Polyzoa and the Hydroida is shown most decisively not to be
a true affinity, when the structure of the individual zo6ids is
examined. The polypite of a Hydroid Zoophyte, as we have
already seen, possesses no alimentary canal distinct from the
general cavity of the body; there are no traces of a nervous
system, and the reproductive organs are in the form of external processes of the body-wall. In the zodid of all the Poiyzoa
(fig. ioI, 2), on the other hand, there is a distinct alimentary
canal, completely shut off from the somatic cavity; a nervous
system is present, and the reproductive organs are contained
within the body.
The following are the more important differences in the terminology employed to designate the various parts of the compound growths of the Polyzoa and the Hydrozoa.  In the
Hydroida the entire colony is called the "hydrosoma," and its
investing layer, when present, is called the " polypary," or
"polypidom;" whilst the individuals composing the hydrosoma
are called the the " polypites," and the cups in which these are
in some cases contained are called " hydrothecae." In the
Polyzoa the entire colony- or its entire dermal system-is
called the " polyzoarium" or "coenoecium; " the separate
zo/ids are called " polypides;" and the little chambers in which
each is contained are called the "cells."'
It will be seen, therefore, that the term polypite is restricted
to the zobid of a compound HydrozoMiz, or to the entire hydro



MOLLUSCOIDA: POLYZOA.                   281
soma of a simple member of the class.  The term polype is
applied to a simple Actizozodnz, or to the zoiids of a compound
actinosoma.  Lastly, the term polypide is exclusively employed
to designate the zo6id of one of the Polyzoa.
The construction of a typical polypide of a Polyzodnz is thus
described by Professor Allman (fig. 10, 2):"Let us imagine an alimentary canal, consisting of cesophagus, stomach, and intestine, to be furnished at its origin
with long ciliated tentacula, and to have a single nervous ganglion placed upon one side of the oesophagus. Let us now
suppose this canal to be bent back upon itself towards the
side of the ganglion, so as to approximate the termination to
the origin. Let us further imagine the digestive tube thus
constituted to be suspended in a fluid contained in a membranous sac with two openings, one for the mouth and the
other for the vent, the tentacula alone being external to the
sac. Let us still further suppose the alimentary tube, by means
of a system of muscles, to admit of being retracted or protruded according to the will of the animal; the retraction
being accompanied by an invagination of the sac, so as partially or entirely to include the oral tentacles within it; and if
to these characters we add the presence of true sexual organs
in the form of ovary and testis, occupying some portion of the
interior of the sac, and the negative character of the absence
of all vestige of a heart, we shall have, perhaps, as correct
an idea-apart from all considerations of homology or derivation from an archetype-as can be conveyed of the essential
structure of a Polyzol~z in its simplest and most generalised
condition.
"To give, however, more actuality to our ideal Polyzothn,
we may bear in mind that the immediately investing sac has
the power, in almost every case, of secreting from its external
surface a secondary investment of very various constitution
in the different groups; and we may, moreover, conceive of
the entire animal with its digestive tube, tentacula, ganglion,
muscles, generative organs, circumambient fluid, and investing
sacs, repeating itself by gemmation, and thus producing one
or more precisely similar systems, holding a definite position
relatively to one another, while all continue organically united,
and we shall then have the actual condition presented by the
Polyzoa in their fully-developed state."
The vast majority of the Polyzoa are fixed, but this is not
universally the case. Thus the singular fresh-water Cristatella
is free and locomotive, creeping about by means of a flattened
discoid base, not unlike the foot of the Gasterojodca.




282               MANUAL OF ZOOLOGY.
The two fundamental structures of the "coencecium" of a
Polyzon —viz., the immediately investing sac, and its secon.
dary investment, are sometimes termed the "endoderm" and
2
e'
Fig. Ios.-Morphology of Polyzoa. I. Portion of the coencecium of Flustra truncatr,
magnified. 2. Diagram of a Polyzobn (after Allman): a Region of the mouth
surrourided by tentacles; b Alimentary canal; c Anus; d Nervous ganglion; c
Investing sac (ectocyst); fTestis; f' Ovary; gRetractor muscle. 3. Bird's-head
process, or " avicularium," of a Polyzobn.
"' ectoderm;" but as these terms are employed in describing the
Hydrozoa, it is better to make use of the terms " endocyst"
and " ectocyst," proposed by Dr Allman.
The "ectocyst," or external investment of the ccencecium,
is usually a brown, pergamentaceous, probably chitinous, but
often highly calcareous, membrane; and it is by the ectocyst
that the "cells" are formed.  In  Cristatella, alone of the
Polyzoa, there is no ectocyst, and in Lophopus (fig. 102, 3) the
ectocyst is gelatinous in its consistence. In many cases the
ectocyst is provided with singular appendages, supposed to be
weapons of offence and defence, termed "avicularia" (fig. ioi,
3) and "vibracula." The avicularia, or "bird's-head processes,"
differ a good deal in shape, but consist essentially of "a
movable mandible and a cup furnished with a horny beak,
with which the point of the mandible is capable of being
brought into apposition."-(Busk.)   In shape the avicularia
often closely resemble the head of a bird, and they are in many
respects comparable with the " pedicellarie " of the Echinodermata.1  In the "vibracula," the place of the mandible of the
* There is great reason, however, as shown by Huxley, to regard the




MOLLUSCOIDA: POLYZOA.                         283
avicularium is taken by a bristle, or seta, which is capable of
extensive movement.
The endocyst is always soft, contractile, and membranous.
It lines the interior of the cells formed by the ectocyst, and is
reflected backwards at the mouth of the cell, so as to be invaginated, or inverted into itself; and it finally terminates by
being attached to the base of the circlet of tentacles. This
invagination of the endocyst is more or less permanently present in all the fresh-water Polyzoa. A portion of the inner
surface of the endocyst, if not the whole, is furnished with
vibratile cilia.
a-.
d.
dJ
Fig. I02. —I. Fragment of Flusht- rncatz-, one of the Sea-mats, natural size. 2. A
single polypide of VIalkeria, magnified, showing the orbicular crown of tentacles
3. A polypide of Lophopus crystallinus, a fresh-water Polyzobn, highly magnified,
showing the horse-shoe-shaped crown of tentacles: a Tentacular crown; b Gullet;
c Stomach; d Intestine; e Anus; g Gizzard; k Endocyst;, / Ectocyst; fFuniculus.
The mouth of each polypide is surrounded by a crown of
tubular, non-retractile tentacles, which have their sides ciliated,
and are arranged sometimes in a circle and sometimes in a
crescent.  In the fresh-water Polyzoa the tentacles are united
towards their bases by a funnel-shaped membrane, known as
the "calyx." The tentacles are borne upon a kind of disc, or
avicularia, not as mere appendages or organs of any kind, but as peculiarlymodified' zobids, having many singular points of affinity with the Brachiopoda. The avicularia, like the 1pedicellarice of the Echinodermata, continue
their movements long after the death of the animal.




284             MANUAL OF ZOOLOGY.
stage, which is termed by Professor Allman the "lophophlore."
In the majority of Polyzoa-including -almost all the marine
species-the lophophore is circular (fig. T02, 2); but in most of
the fresh-water forms it has its neural side extended into two
long arms, so that the entire lophophore becomes crescentic
or "horse-shoe-shaped" (fig. I02, 3); hence this section is
sometimes collectively termed the " Hippocrepian" Polyzoa.
In all the Polyzoa in which this crescentic condition of the
lophophore exists, there is also a singular valve-like organ
which arches over the mouth, and is termed the "epistome."
The only marine forms in which the lophophore is bilateral
are Pedicedlina and Rhabdofpleura; the only fresh-water species
in which the lophophore is orbicular are Pa/udiceZla and
Urnatedia.
The mouth conducts by an cesophagus into a dilated stomach.
In some cases a pharynx may be present, and in others there
is in front of the stomach a muscular proventriculus, or gizzard. From the stomach proceeds the intestine, which shortly
turns forward to open by a distinct anus close to the mouth.
As the nervous ganglion is situated on that side of the mouth
towards which the intestine turns in order to reach its termination, the intestine is said to have a "neural flexure," and this
relation is constant throughout the entire class.
Respiration in the Polyzoa appears to be carried on by the
ciliated tentacles, and by the "perigastric space," which is
filled with a clear fluid, containing-solid particles in suspension. A kind of circulation is kept up in this "perigastric
fluid" by means of the cilia lining the inner surface of the
endocyst. Beyond this there is nothing that could be called
a circulation, and there are no distinct circulatory organs of
any kind.
The nervous system in all the Polyzoa consists of a single
small ganglion (fig. IoI, 2), placed upon one side of the cesophagus, between it and the anal aperture. Besides the single
ganglion which belongs to each polypide, there is also in many,
if not in all, of the Polyzoa, a "colonial nervous system;" that
is to say, there is a well-developed nervous system, which
unites together the various zodids composing the colony, and
brings them into relation with one another. It is probably in
virtue of this system that the avicularia are enabled to continue their movements, and retain their irritability after the
death of the polypides.
The muscular system is well developed, and consists of
various muscular bands, with special functions attaching to
each. The most important fasciculi are the retractor muscles




MOLLUSCOIDA: POLYZOA.                 285
(fig. Ior, 2, g), which retract the upper portion of the polypide
within the cell. These muscles arise from the inner surface of
the endocyst near the bottom of the cell, and are inserted into
the upper part of the cesophagus.  The polypide, when retracted, is again exserted, chiefly by the action of the " parietal
muscles," which are in the form of circular bundles running
transversely round the cell.
As far as is known, all the Polyzoa are hermaphrodite, each
polypide containing an ovary and testis (fig. IoI, 2).  The
ovary is situated near the summit of the cell, and is attached
to the inner surface of the endocyst. The testis is situated at
the bottom of the cell, and a curious cylindrical appendage,
called the "funiculus," usually passes from it to the fundus of
the stomach. There are no efferent ducts to the reproductive
organs; and the products of generation-i.e., the spermatozoa
and ova — are discharged into the perigastric space, where
fecundation takes place; but it is not certainly known how
the impregnated ova escape into the external medium.
As already mentioned, continuous gemmation occurs in all
the Polyzoa, the fresh zo6ids thus produced remaining attached
to the organism from which they were budded forth, and thus
giving rise to a compound growth.
A form of discontinuous gemmation, however, occurs in
many of the Polyzoa, in which certain singular bodies, called
"statoblasts," are developed in the interior of the polypide.
The statoblasts are found in certain seasons lying loose in the
perigastric cavity.  In form "they may be generally described
as lenticular bodies, varying, according to the species, from an
orbicular to an elongated-oval figure, and enclosed in a horny
shell, which consists of two concavo-convex' discs united by
their margins, where they are further strengthened by a ring
which runs round the entire margin, and is of different structure from the discs.... When the statoblasts are placed
under circumstances favouring their development, they open
by the separation from o'ne another of the two faces, and
there then escapes from them a young Pol~zooi, already in an
advanced stage of development, and in all essential respects
resembling the adult individual in whose cell the statoblasts
were produced."-(Allman.)  The statoblasts are formed as
buds upon the "funiculus"-the cord already alluded to as
extending from the testis to the stomach-upon which they
may usually be seen in different stages of'growth. They do
not appear to be set free from the perigastric space prior to
the death of the adult, and when liberated they are enabled
to float near the surface of the water, in consequence of the




286               MANUAL OF ZOOLOGY.
cells of the marginal ring, or'annulus," being spongy and
filled with air.  They must be looked upon as "germma  pecu
liarly encysted, and destined to remain for a period in a quiescent or pupa-like state."-(Allman.)
As regards the development of the Polyzoa, the embryo
upon its emergence from the ovum presents itself as a ciliated,
free-swimming, sac-like body, from which the polypide is subsequently produced by a process of gemmation. In the singular -Rhabdopleura the primitive bud is enclosed between two
fleshy lobes or valve-like plates, attached along their dorsal
margin, and giving exit in front to the rudimentary lophophore.
As the development proceeds, these plates cease to keep pace
in their growth with the rest of the bud; till ultimately they
appear as a peculiar shield-like organ on the h~amal side of the
lophophore. These lobes have been compared by Dr Allman
with the mantle-lobes of the Lame/dibranchziala.
DIVISIONS OF THE POLYZOA.-The Polyzoa are divided into
two divisions or orders-the Phzy/acto/zvmata (fig. Io2, 3), distinguished by the possession of a bilateral horse-shoe-shaped
lophophore, and of an " epistome" arching over the mouth;
and the Gymnoacemata (fig. I02, 2), in which the lophophore is
orbicular, and there is no epistome.
TABLE OF THE DIVISIONS OF THE POLYZOA.
ORDER I. PHYLACTOLEMATA.
Lophophore bilateral; mouth with an epistome.
Sub-order I. Lophopea (fresh-water).
Arms of lophophore free or obsolete; consistence horny, sub-calcareous.
Sub-order 2. Pedicellinea (marine).
Arms of lophophore united at their extremities; consistence soft,
fleshy.
Sub-order 3. Rhabdopleurea (marine).
Ccencecium branched, adherent, membranous, with a solid chitinous rod on its adherent side, to which the polypites are attached
by their,funiculi. Lophophore completely hippocrepian, with a
peculiar shield-like body on its hoemal side. No epistome (?)
ORDER II. GYMNOLEMATA.
Lophophore orbicular, or nearly so; no epistome.
Sub-order 4. Paludicellea (fresh-water).
Polypide completely retractile; evagination of tentacular sheath
imperfect; consistence horny or sub-calcareous.
Sub-order 5. Cheilostonzata (marine).
Polypide completely retractile; evagination perfect; orifice of cell
sub-terminal, of less diameter than the cell, and usually closed with
a movable li:p or shutter, sometimes by a contractile sphincter; cells
not tubular; consistence calcareous, horny, or fleshy.




MOLLUSCOIDA: TUNICATA.                     287
Sub-order 6. Cyclostomata (marine).
Cell tubular; orifice terminal, of the same diameter as the cell,
without any movable apparatus for its closure; consistence calcareous.
Sub-order 7. Ctenostomata (marine).
Orifice of the cell terminal, furnished with a usually setose fringe
for its closure; cells distinct, arising from a common tube; consisttence horny or carnose.
CHAPTER XLIII
TUNICA TA.
CLASS II. TUNICATA (Ascidioida).-The members of this class
of the Molluscoida are defined as follows:-" Alimentary canal
suspended in a double-walled sac, but not capable of protrusion and retraction; mouth opening into the bottom of a respiratory sac, whose walls are more or less completely lined by
a network of blood-vessels."-(Allman.)   Animal simple or
composite. An imperfect heart in the form of a simple tube
open at both ends.
The Tunicaries are all marine, and are protected by a leathery, elastic integument, which takes the place of a shell.  In
appearance a solitary Ascidian (fig. 103) may be compared to
a double-necked jar with two prominent apertures situated
close to one another at the free extremity of the animal, one
of these being the mouth, whilst the other serves as an excretory aperture. The covering of an Ascidian is composed of
two layers. Of these the outer is called the " external tunic,"
or " test," and is distinguished by its coriaceous or cartilaginous
consistence.  It is also reynarkable for containing a substance
which gives the same chemical reactions as cellulose, and is
probably identical with this characteristic vegetable product.
The test is lined by a second coat, which is termed the " second
tunic," or "mantle," and which is mainly composed of longitudinal and circular muscular fibres. By means of these the
animal is endowed with great contractility, and has the power
of ejecting water from its branchial aperture with considerable
force.  The mantle lines the test, but is only slightly and
loosely attached to it, especially near the apertures.  The
mouth is generally surrounded by a circlet of small, non-ciliated,
non-retractile tentacles, and opens into a large chamber (fig.
103, 1, c), which usually occupies the greater part of the cavity




288                MANUAL OF ZOOLOGY.
of the mantle, and has its walls perforated by numerous apertures.  This is known variously as the' pharynx," the " respiratory sac,"' or the " branchial sac."   (It must be remembered
that the aperture here spoken of as the mouth can only be
looked upon in this light provided that the respiratory sac is
looked upon as the pharynx. By Professor Allman, whose
definition is given at the head of this chapter, this view is not
accepted, and consequently the internal or inferior opening of
the respiratory sac is regarded as the true mouth.) Inferiorly
the respiratory sac leads by a second aperture into an cesophagus, which opens into a capacious stomach.   From  the
If2
Fig..-Morphology of.. Diagram of a
Fig. I03.- Iorphology ofTl'unicata. I. Diagram of a Tunicary(after Allman): a Ora
aperture; b Atrial aperture; c Pharyngeal or branchial sac, with its rows of ciliated
apertures, d Alimentary canal, with its htemal flexure; e Anus; f Atrium; g Nervous ganglion. 2. Cyntthtiapahillosa, a simple Ascidian (after Woodward).
stomach an intestine is continued, generally with few flexures,
to the anal aperture, which does not communicate directly
with the exterior, but opens into the bottom of a second chamber, which is called the "cloaca" (fig. 103, I,f).  Superiorly
the cloaca communicates with the external medium, by means
of the second aperture in the test. The first bend of the
intestine is such that, if continued, it would bring the anus on
the opposite side of the mouth to that on which the nervous
ganglion is situated. The intestine, therefore, is said to have
a "henmal flexure;" whereas the flexure in the case of the
Polyzoa is "neural."  The intestine, however, in the Tunicata
does not preserve this primary hxemal flexure, but is again
bent to the neural side of the body, the nervous ganglion coming




MOLLUSCOIDA: TUNICATA.                289
finally to be situated between the mouth and the rectum. As
just stated, the anus is not in direct communication with the
exterior, but opens into a large cavity, called the "cloaca," or
"atrial chamber," which, in turn, opens externally by tlhe
second aperture of the animal. This cloaca is a large sac lined
by a membrane which "is reflected like a serous sac on the
viscera, and constitutes the'third tunic,' or'peritoneum."'
From the cloaca "it is reflected over both sides of the pharynx"
(respiratory sac), "extending towards its dorsal part very
nearly as far as that structure which has been termed the'endostyle.' It then passes from the sides of the pharynx to the
body-walls, on which the right and left lamelle become continuous, so as to form the lining of the chamber into which the
second aperture leads, or the'atrial chamber.' Posteriorly,
or at the opposite end of the atrial chamber to its aperture, its
lining membrane (the'atrial tunic') is reflected to a greater
or less extent over the intestine and circulatory organs.
Where the atrial tunic is reflected over the sides of the pharynx,
the two enter into a more or less complete union, and the surfaces of contact become perforated by larger or smaller, more
or less numerous, apertures.  Thus the cavity of the pharynx
acquires a free communication with that of the atrium; and
as the margins of the pharyngo-atrial apertures are fringed with
cilia working towards the interior of the body, a current is
produced, which sets in at the oral aperture and out by the
atrial opening, and may be readily observed in a living
Ascidian."-(Huxley.)
As regards some points in the above description, Professor
Allman does not agree with Huxley, but believes, on the other
hand, "that the walls of the atrium simply surround the
branchial sac, without being reflected on its sides, and that the
branchial sac is therefore properly Rith/in  the cavity of the
atrium."
In structure, the pharyngeal or "branchial" sac is composed
of a series of longitudinal and transverse bars, which cross
each other at right angles, and thus give rise to a series of
quadrangular meshes, the margins of which are fringed with
vibratile cilia. These bars are hollow, and are really vessels
which open on each side" into two main longitudinal sinuses,
the so-called " branchial " or "thoiracic" sinuses-one of which
is placed along the heemal side of the pharynx, whilst the
other runs along its neural aspect. The function of the entire
perforated pharynx is clearly respiratory.
The Tunicata possess a distinct heart, consisting of a simple
muscular tube, which is open at both ends, and is not provided




290             MANUAL OF ZOOLOGY.
with valves. In consequence of this, the circulation in the
mffajority of Tunicaries is periodically reversed, the blood
being propelled in one direction for a certain number of contractions, and being then driven for a like period in an opposite direction; "so that the two ends of the heart are alternately arterial and venous."
The nervous system consists of a single ganglion placed on
one side of the oral aperture, between it and the anus, in all
known Tunicala, except in the aberrant form Aplpendicuzaria.
The only organs of sense are pigment-spots, or ocelli, placed
between the oral tentacles, and an auditory capsule, sometimes
containing an otolith. These organs, however, do not appear
to be constantly present.
With the exception of Doliolum and A1ppendicuiaria, all the
Tunicafa are hermaphrodite.  The reprqductive organs are
situated in the fold of the intestine, and their efferent duct
opens into the atrium.  The embryo Tunicate is at first generally free, and is mostly shaped like the tadpole of a frog,
swimming by means of a long caudal appendage.  In one
species (Molgula tubulosa) the larval form is destitute of a tail,
inactive, and amreboid, and it almost immediately attaches
itself by means of little outward processes which it develops.
Lastly, in several. instances the larval caudal appendage has
been shown to'exhibit' a cylindrical rod-like body, which has
been paralleled with the chorda dorsalis of Vertebrates.
Amongst the Salpians a species of alternation of generations
has been observed. A solitary Salpian produces long chains
of embryos, which remain organically connected throughout
their entiie life.  Each individual of these associated specimens produces solitary young, which are often very unlike their
parents, and these again give rise to the aggregated forms.
The Thinicata are often spoken of as exhibiting three main
types of structure, which give origin to as many sections,
known respectively as the solitary, the social, and the coimpound
forms. In the " solitary" Tunicaries, the individuals, however
produced, remain entirely distinct, or, if not so primitively,
they become so.  In the "social" Ascidians the organism
consists of a number of zo6ids, produced by gemmation and
permanently connected together by a vascular canal, or " stolon,"
composed of a prolongation of the common tunic, through
which the blood circulates. Finally, in the " compound" forms,
the zo/ids become aggregated into a common mass, their tests
being fused together, but there being no internal union. The
Botrylli, which are familiar examples of the compound Tunicates, form semi-transparent masses, oftefn of brilliant colours,




MOLLUSCOIDA: TUNICATA.                     291
attached to various submarine objects, and consisting of
numerous zodids arranged in star-shaped groups. They are
almost always "very small, soft, irritable, and contractile,
changing their form with the slightest movement."-(Stark.)
HOMOLOGIES OF THE TUNICATA.-The general resemblance
between a solitary Ascidian and a single polypide of a Polyzoi'ni
is extremely obvious; each consisting of a double-walled sac.
containing a freely suspended alimentary canal, with a distinct
mouth and anus, and a nervous ganglion placed between the
two.  The chief feature in the Tunicata, as to the exact nature
of which there is much difference of opinion, is the branchial
or respiratory sac. By Professor Allman this is believed to be
truly homologous with the'tentacular crown of the Polyzoa,
and the oral tentacles of the Tunicaries are believed to be
something superadded, and not represented at all in the Polyzoa. By Professor Huxley, on the other hand, the branchial
sac is looked upon as an enormously developed pharynx, and
the oral tentacles are regarded as a rudimentary representative
of the tentacular crown of the Polyzoa.   Probably the most
correct view of the homologies of the  Gaznica/a is taken by
Rolleston, who regards the "branchial sac" as the homologue
of the gills of the ordinary Bivalve Molluscs (LameZlibranchiata),
whilst the oral and atrial apertures are looked upon as corresponding to the respiratory apertures of these same animals.
DIVISIONS OF THE TUNICATA.-By Professor Huxley the
following arrangement of the Tunicaries is adopted:CLASS TUNICATA.
Order I. Ascidia Branchialia.
Branchial sac occupying the whole, or nearly the whole, length of
the body; intestine lying on one side of it.  (Ascidiadz, Botryllus,
~-c. )
Order II. Ascidia Atbdominalia.
Alimentary canal completely behind the branchial sac, which is
comparatively small. (Claveizina, Doaiolum, &-c.)
Order III. Ascidia Larvalia.
Permanent larval form. (A.pezendicularia.)
The following subdivisions are those adopted by Mr Woodward:
CLASS TUNICATA.
Fart. I. Ascidiade (Simple Ascidians).
Animal simple, fixed, solitary, or gregarious; oviparous; sexes
united; branchial sac simple; or disposed in (8-I8) deep and regular
folds.
Fam. II. Clavellinidae (Social Ascidians).
Animal compound, fixed; individuals connected by creeping tubular
prolongations of the common tunic through which the blood circulates
14




292               MANUAL OF ZOOLOGY.
(or by a common gelatinous base). Reproduction effected by ova, or
by gemmation from the common tube; the new individuals remaining
attached to the parent, or becoming completely free.
Fam. III. Botryllide (Compound Ascidians).
Anrimals compound, fixed, their tests fused, forming a common mass
in which they are imbedded in one or more groups. Individuals not
connected by any internal union; oviparous and gemmiparous.
Fam. IV. Pyr/osomid.s
Animal compoand, free and oceanic.
Farn. V. Salpida.
Animals free and oceanic; alternately solitary and aggregated.
CHAPTER XLIV.
BRA CHIOPODA.
CLASS III. —BRACHIOPODA (PaZlliobranciata).-The members
of this class are defined by the possession of a body protected
by a bivalve shell, which is lined by an expansion of the integument, or "mantle."   The mouth is furnished with two
long cirriferous arms. The nervous system consists of a single
ganglion, placed in the re-entering angle between the gullet
and the rectum, so that the intestine has a " neural flexure."
The Brac/ioapoda are essentially very similar in structure to
the Polyzoa, from which they are distinguished by the fact that
they are never composite, and by the possession of a bivalve,
calcareous, or sub-calcareous shell. They are commonly known
as "Lamp-shells," and are all inhabitants of the sea. All the
living forms are fixed to some solid object in their adult condition; but there is good reason to believe that many of the
fossil forms were unattached and free in their fully-grown condition. From the presence of a bivalve shell, the Brachiopods
have often been placed near the true bivalve Mollusca (the
Lamellibranchiala);. but their organisation is very much inferior,
and there are also sufficient differences in the shell to justify
their separation.
The two valves of the shell of any Brachiojod are articulated
together by an apparatus of teeth and sockets, or are kept in
apposition by muscular action alone. One of the valves is
always slightly, sometimes greatly, larger than the other, so
that the shell is said to be "inequivalve." As regards the
contained animal, the position of the valves is anterior and
posterior, so that they are therefore termed respectively the
"ventral" and  "dorsal" valves.  In the ordinary bivalve




MOLLUSCOIDA: BRACIIOPODA.                293
MAfollusca (Lamellibranchiata), on the other hand, the two valves
of the shell are usually of the same size (equivalve), and they
are situated upon the sides of the animal; so that, instead of
being dorsal and ventral, they are now termed "right" and
" left" valves. The ventral valve in the shell of the Brachiopoda is usually the largest, and usually possesses a prominent
curved beak. The beak is sometimes perforated by a "foramen," or terminal aperture, through which there is transmitted
a muscular peduncle, whereby the shell is
attached to some foreign object.  In some
cases, however (as in Lingula, fig. I04), the
peduncle simply passes between the apices of
the valves, and there is no foramen; whilst in
others (as in Crania) the shell is merely attached by the substance of the ventral valve.
The dorsal or smaller valve is always free, and
is never perforated by a foramen.
In intimate structure, the shell of most of
the Brac/ziopoda consists "of flattened prisms,
of considerable length, arranged parallel to
one another with great regularity, and at a
very acute angle-usually only about Io~ or
I2~ —with the surfaces of the shell."-(Carpenter.) In most cases, also, the shell is perforated by a series of minute canals, which pass
from one surface of the shell to the other, in
a more or less vertical direction, usually widening as they approach the external' surface.
These canals give the shell a "punctated"
structure, and in the living animal they contain caecal tubuli, or prolongations, from the
mantle, which are considered by Huxley as Fig;. o4. —Zg'uahoi
analogous to the vascular processes by which  the mtlscular pedin many Ascidians the muscular tunic, or'h;uncle by which the
in many Ascidians the muscular tunic, or  shell is attached.
"mantle," is attached to the outer tunic, or
" test." In some of the Braczhiopoda (as in the Rhynchonellid&e )
the shell is "impunctate," or is devoid of this singular canal
system.
The inner surface of the valves of the shell is lined by expansions of the integument which secrete the shell, and are
called the "lobes" of the "pallium," or "mantle." The digestive organs and muscles occupy a small space near the beak
of the shell, which is partitioned off by a membranous septum,
which is perforated by the aperture of the mouth. The remainder of the cavity of the shell is.almost filled by two long




294             MANUAL OF ZOOLOGY.
oral processes, which are termed the " arms," and from which
the name of the class has been derived (fig. I05, i). These
organs are lateral prolongations of the margins of the mouth,
usually of great length, closely coiled up, and fringed on one
side with lateral processes, or "cirri." In many Brachiopods
the arms are supported upon a more or less complicated internal calcareous framework or skeleton, which is sometimes called
the "carriage-spring apparatus."
Zrt         z        ~2
Fig. io5.-Brachiopoda (Terebratfua vitrea). I. Show ing the ciliated "arms;"
2. Showing the shell with its loop. (After Woodward.)
The mouth conducts by an cesophagus into a distinct
stomach, surrounded by a well-developed granular liver. The
intestine has a "a neural flexure," and " either ends blindly in
the middle line, or else terminates in a distinct anus between
the pallial lobes."-(Huxley.)
Within the pallial lobes there is a remarkable system  of
more or less branched tubes, anastomosing with one another,
and ending in caecal extremities. This, which has been termed
by Huxley the "atrial system," communicates with the perivisceral cavity by means of two or four organs which are called
"pseudo-hearts," and which were at one time supposed to be
true hearts.  " Each pseudo-heart is divided irno a narrow,
elongated, external portion (the so-called'ventricle'), which
communicates, as Dr Hancock has proved, by a small apical
aperture, with the pallial cavity; and a broad, funnel-shaped,
inner division (the so-called'auricle') communicating, on the
one hand, by a constricted neck, with the so-called'ventricle;'
and, on the other, by a wide, patent mouth, with a chamber
which occupies most of the cavity of the body proper, and
sends more or less branched diverticula into the pallial lobes."
-(Huxley.)  This system of the atrial canals has been looked
upon as a rudimentary respiratory apparatus; but its function
is more probably to act as an excretory organ, and also to
convey away the reproductive elements, the organs for which
are developed in various parts of its walls.  By Woodward




MOLLUSCOIDA: BRACHIOPODA.               295
the pseudo-hearts are regarded as oviducts, and it is stated
that they have been found to contain mature ova, so that
there can be little doubt but that this view of their nature is
the correct one. By Rolleston the pseudo-hearts are looked
upon as corresponding with the so-called " organ of Bojanus"
of the Lamellibranlchiata.
The function of respiration is probably performed, mainly,
if not entirely, by the cirriferous oral arms, as it appears chiefly
to be iby the homologous tentacular crown of the Polyzoa. A
true vascular system and a distinct heart are present in some,
at any rate, of the Brdchiopoda, but this subject is still involved
in considerable obscurity.  In Zerebratula the heart is in the
form of a unilocular, pyriform vesicle, placed bn the dorsal
surface of the stomach.
The nervous system consists of a principal ganglion of no
great size, placed in the re-entering angle between the gullet
and the rectum. In those Brachiopods in which the valves of
the shell are united by a hinge, the nervous system attains a
greater development, and consists of a gangliated cesophageal
collar.
The sexes are said to be ordinarily distinct, but in some
cases they appear to be united in the same individual.  The
development of the Brachiopjoda is still shrouded in considerable obscurity, but in some cases the young have been observed to move frorvf place to place, either by protruding their
ciliated arms, or by means of spines developed in the ventral
lobe of the mantle.
The Brachiopoda may be divided into two groups, called
respectively the Articulata and Inarticulata.  In the former
the valves of the shell are united along a hinge-line, the lobes
of the mantle are not completely free, and the intestine ends
caecally. In this group are the recent Terebratulidc and Rhynchonellidie. In the Inarticulata the valves of the shell are not
united along a hinge-line, the mantle-lobes are completely free,
and the intestine terminates in a distinct anus. In this group
are the Craniadee, Discinid-e, and Linguzidc3.
AFFINITIES OF THE BRACHIOPODA.-There can be no question as to the close relationships subsisting between the Brachiopoda and Polyzoa, and until recently most naturalists held that
both these groups had strongly-marked affinities with the Lamellibranchiata.  This view is still held by the generality of
naturalists; but recently Mr Edward Morse has brought forward
evidence to show that the Brachiopoda and Polyzoa are most
nearly related to the Tubicolar Annelides; and this opinion
had been previously advanced as regards the latter group by




296                MANUAL OF ZOOLOGY.
Leuckhart.  Amongst the more striking facts adduced in support of this view may be mentioned the assertion- that the long
and worm-like peduncle of Lingula pyramidata is normally
encased in a sand-tube resembling that of a Tubicolous Annelide. The peduncle of this form is also contractile and hollow,
admitting the blood into its interior, and the blood is stated to
be red.  In the meanwhile, however, the affinities between the
Brachiopoda and Polyzoa, on the one hand, and the Tunicata
on the other, are too strong to allow of our unhesitating acceptance of this sweeping change.
CLASSIFICATION OF THE BRACHIOPODA (AFTER DAVIDSON).
CLASS BRACHIOPODA.
Fant. I. Tereb;ratzlidar.
Shell minutely punctate; ventral valve with a prominent beak perforated by a foramen for the emission of a muscular peduncle, whereby
the animal is fixed to some solid object.  Foramen partially surrounded
by a deltidium of one or two pieces.  Oral appendages entirely or
partially supported by calcified processes, usually in the form of a loop,
and always fixed to the dorsal valve.
Genera.-Teirebratula (with Terebratulina, and Waldheirnia), Terebratella, Stringocephalus, a&c.
Fant. II. Thzecididae.
Shell fixed to the sea-bottom by the beak of the larger or ventral
valve; structure punctated. Oral processes united in the form of a
bridge over the visceral cavity; cirrated arms folded upon themselves,
and supported by a calcareous loop.
Genus.- Thecidium.
Fam. IIIL Shiriferidae.
Animal free, or rarely attached by a muscular peduncle.  Shell
punctated or unpunctated.   Arms largely developed, and entirely
supported by a thin, shelly, spirally rolled lantella.
Genera. —Spirife;, Spihtfetrina, CyrtIia, At/iyris, &'c.
Faum. IV. Koninckidae.
Animal unknown.  Shell free; valves unarticulated (?). Oral arms
supported by two lamelle, spirally coiled.
Genus. —Konzizckia.
Fant. V. Rhynchonellidar.
Animal free, or attached by a muscular peduncle issuing from an
aperture situated under the extremity of the beak of the ventral valve.
Arms spirally rolled, flexible, and supported only at their origin by a
pair of short, curved, shelly processes.  Shell-structure fibrous and
impunctate.
Generaz.-Rhynczonella, I'enltamerus, Porlambonites, &cr
Faro. VI. Stroh5hontenidbe.
Animal unknown;n;  some probably free, others attached, during the
whole or a portion of their existence, by a muscular peduncle.  No
calcified supports for the arms.  Shell with a straight hinge-line, and
a low triangular area in each valve.  Shell-structure fibrous and
punctated.
Genera.-Ortzis, Orl/:isina, St;-rophonzela, and Lep/aena.




MOLLUSCOIDA: DISTRIBUTION.                       297
Farm. VII. Productida.
Animal unknown. Shell entirely free, or attached to marine bottoms
by the substance of the beak; valves either regularly articulated, or
kept in place by muscular action. No calcified support for the oral
appendages.
Genera. —Producta, Chonetes, Strophalosia, Aulosteges.
Fam. VIII. Craninad.
Animal fixed to submarine objects by the substance of the shell of
the ventral valve.  Arms fleshy and spirally coiled; no hinge or
articulating processes; upper or dorsal valve patelliform (i.e. limpetshaped).
Genus.-Crania.
Fam. IX. Discinidae.
Animal attached by means of a muscular peduncle passing through
the ventral or lower valve by means of a slit in its hinder portion, or
a circular foramen excavated in its substance. Arms fleshy, valves
unarticulated.
Genera.-Discina, Trematis, Silphonotrela, Acrotrela.
Faim. X. Linulid&e.*
Animal fixed by a muscular peduncle passing out between the beaks
of the valves; arms fleshy, unsupported by calcified processes. Shell
unarticulated, sub-equivalve, texture horny.
Genera. —inzzula, Obolus.
CHAPTER XLV.
DISTRIBUTIONl OF MIOLLUSCOIDA.
DISTrRIUTION OF MOLLUSCOIDA IN SPACE.-The Polyzoa, like
all the Molluscoida, are exclusively aquatic in their habits, but,
unlike the remaining two classes, they are not exclusively confined to the sea. The marine Polyzoa are of almost universal
occurrence in all seas.  The fresh-water Polyzoa, however, not
only differ materially from their marine brethren in structure,
but appear to have a much more limited range, being, as far as
is yet known, confined to the north temperate zone. Britain
can claim the great majority of the described species of freshwater Polyzoa, but this is probably due to the more careful
scrutiny to which this country has been subjected.
The Tunicata are cosmopolitan in their distribution, and are
found in all seas, the Mediterranean appearing to be especially
rich in members of this class. Four genera are pelagic in their
habits, and several are found in the Arctic regions.
* Another.amily was formerly constituted for the reception of the singular Devoni-n fossils known as Calceole.  It has been shown, however,
that these are probably operculate Corals.




298             MANUAL OF ZOOLOGY.
The Brachioypoda, though of very partial occurrence, have a
wide range in space, being found both in tropical seas and in
the Arctic Ocean. Their bathymetrical range is also very wide,
extending from the littoral zone almost to the greatest depths
at which animal life has hitherto been detected.
DISTRIBUTION OF MOLLUSCOIDA IN TIME.-The Polyzoa
have left abundant traces of their past existence in the stratified
series, commencing in the Lower Silurian Rocks and extending
up to the present day. The Oldhamnia of the Cambrian Rocks
of Ireland, and the Grap/oliles, have been supposed to belong
to the Pol,zoa; but the former is very possibly a plant, and the
latter should be referred to the Hydrozoa. Of undoubted Polyzoa, the marine orders of the Cheilostomala and Cyclostomata
are alone known with certainty to be represented. Several
Palaeozoic genera-such as Fenestella (the Lace-coral), Pti/odictya, Ptilo5pora, &c.-are exclusively confined to this epoch,
and do not extend into the Secondary Rocks. Amongst the
Mesozoic formations, the Chalk is especially rich in Polyzoa,
over two hundred species having been already described from
this horizon alone. In the Tertiary period, the Coralline Crag
(Pleiocene) is equally conspicuous for the great number of the
members of this class.
The Tunicatn, from the nature of their bodies, are not knowp
to occur in a fossil condition.
The Bracziopoda are found from the Cambrian Rocks up to
the present day, and present us with an example of a group
which appears to be slowly dying out. Nearly two thousand
extinct species have been described, and the class appears to
have attained its maximum in the Silurian epoch, which is,
for this reason, sometimes called the "Age of Brachiopods."
Numerous genera and species are found also in both the
Devonian and Carboniferous formations.  In the Secondary
Rocks Brachiopoda are still abundant, though less so than in
the Palaeozoic period.  In the Tertiary epoch a still further
diminution takes place, and at the present day we are not
acquainted with a hundred living forms. Of the families of
Brachiopoda, the ProductidCe, Strophomenidei, and Spiriferidce
are the more important extinct types. Of the genera, the most
persistent is the genus Lingula, which commences in the Cambrian Rocks, and has maintained its place up to the present
day, though.it appears to be gradually dying out.
According to Woodward:-" The hingeless genera attained
their maximum in the Paleozoic age, and only three now survive (Lingula, Discina, Crania)-the representatives of as many
distinct families. Of the genera with articulated valves, those




MOLLUSCOIDA: vISTRIBUTION.              299
provided with spiral arms appeared first, and attained their
maximum while the TeirebratuAidce were still few in number.
The subdivision with calcareous spires disappeared with the
Liassic period, whereas the genus Rhynchonella still exists.
Lastly, the typical group, Terebratudide, attained its maximum
in the Chalk period, and is scarcely yet on the decline."




MOLL USCA PROPER.
CHAPTER XLVI.
LA MELLIBRA NCHIA TA.
DIVISION II. MOLLUSCA PROPER.-This division includes those
members of the sub-kingdom Mollusca in which the nervous
system consists of three principal pairs of ganglia; and there is
always a well-developed heart, which is never composedS of fewer
than two chambers.
The Mollusca proper may be roughly divided into two great
sections, respectively termed the Acephala and the Encephala
(or Cephalophora), characterised by the absence or presence of
a distinctly differentiated head. The headless; or Acephalous,
Molluscs correspond to the class Lamellibranchiata; also distinguished, at first sight, by the possession of a bivalve shell.
The Encephalous Molluscs are more highly organised, and are
divided into three classes-viz., the Gasteropoda, the Eteropoda,
and the Cephalopoda.  The shell in these three classes is of
very various nature, but they all possess a singular and complicated series of lingual teeth; hence they are grouped together by Professor Huxley under the nanle of Odontophora.
CLASS I. LAMELLIBRANCHIATA, or CONCH1FERA. -  The
members of this class are characterised by the absence of a
distinctly differentiated head, and by having the body more or
less completely protected in a bivalve shell. There are two
lamellar gills on each side of the body, the intestine has a
neural flexure, and there is no odontophore.
The Lameellibranchiata are commonly known as the bivalve
shell-fish, such as Mussels, Cockles, Oysters, Scallops, &c.,
and they are all either marine or inhabitants of fresh water.
Though they agree with the Brachiopoda in possessing a
shell which is composed of two pieces or valves, there are,
nevertheless, many points in which the shell of a Lamellibranch is distinguishable from that of a Brachiopod, irrespective of the great difference in the structure of the animal in




MOLLUSCA: LAMELLIBRANCHIATA.                30I
each.  The shell in the Brachiopoda, as we have seen, is rarely
or never quite equivalve, and always has its two sides equally
developed (equilateral); whilst the valves are placed anteroposteriorly as regards the animal, one in front and one behind,
so that they are " dorsal " and " ventral."  In the Lamellibranchiata, on the other hand, the two valves are usually of nearly
equal size (equivalve), and are more developed on one side
than on the other (inequilateral); whilst their position as regard.s the animal is always lateral, so that they are properly
termed "right" and "left" valves, instead of "ventral" and
" dorsal."
The following are the chief points to be noticed in connection with the shell of any Lamellibranch: Each valve of the
shell may be regarded as essentially a hollow cone, the apex of
which is turned more or less to one side; so that more of thei
shell is situated on one side of the apex than on the other.
The apex of the valve is called the "umbo," or "beak," and
is always turned towards the mouth of the animal. Consequently, the side of the shell towards which the umbones are
turned is the "anterior " side, and it is usually the shortest half
of the shell.  The longer half of the shell, from which the
umbones turn away, is called the "posterior" side, but in some
cases this is equal to, or even shorter than, the anterior side.
The side of the shell where the beaks are situated, and where
the valves are united to one another, is called the "dorsal"
side; and the opposite margin, along which the shell opens, is
called the "ventral" side, or "base."  The length of the shell
is measured from its anterior to its posterior margin, and its
breadth from the dorsal margin to the base.
At the dorsal margin the valves are united to one another,
for & shorter or longer distance, along a line which is called
the "hinge-line." The union is effected in most shells by
means of a series of parts which interlock with one another
(the "teeth "), but these are sometimes absent, when the shell
is said to be "edentulous." Posterior to the umbones, in most
bivalves, is another structure passing between the valves, which
is called the " ligament," and which is usually composed of two
parts, either distinct or combined with one another. These
two parts are known as the "external ligament" (or the ligament proper) and the "cartilage," and they constitute the
agency whereby the shell is opened, but one or other of them
may be absent.  The ligament proper is outside the shell, and
consists of a band of horny fibres, passing from one valve to
the other just behilnd the beaks, in such a manner that it is put
uzpon the stretch when the shell is closed.  The cartilage, or




302                MANUAL OF ZOOLOGY.
internal ligament, is lodged between the hinge-lines of the two
valves, generally in one or more "pits," or in special processes
of the shell.  It consists of
elastic fibres placed  perpendicularly between the surfaces
by which it is contained, so
-o,.,s      that they are necessarily shortened  and  compressed  when
the valves are shut.  To open
the shell, therefore, it is simply
necessary for the animal to
relax  the muscles which  are
provided for the closure of the
valves, whereupon the elastic
force of the ligament and cartilage is sufficient of itself to
Vi Aopen the shell.
The  body in  the Lame/lia              l/oI~j Ad branchiata is always enclosed
in an expansion of the dorsal
H)1     }           r  J PilAnm integument, which constitutes
the  " mantle," or "pallium,"
whereby the shell is secreted.
The lobes of the mantle are
right and left, and not anterior
and posterior as are the mantlelobes of the Brachiopoda.  Tow ards  its circumference  the
mantle is more or less com-,....-~                   pletely  united  to  the  shell,
leaving  in  its interior, when
~__V_~.          the soft parts are removed, a
By_ \    H i  more or less distinctly impres-,2'      "        "of /   sed line, which is called the',z,          "pallial line," or "impression"
(fig. 1o7).
Fig. io6.-Anatomy of a bivalve Mollusc    There is no distinctly diffe(Mya arenzaria). The left valve and rentiated head in any of the
mantle-lobe and half the siphons are removed. s s Respiratory siphons, the Lamellibranchiala,  and   the
arrows indicating the direction of the   is simply placed a
currents; a a' Adductor muscles; b                placed       e
Gills; h Heart; o Mouth, surrounded by anterior extremity of the body.
(p) labial palpi; * Foot; v Anus; mn Cut
edge of the mantle. (After Woodward.)  It is furnished with membranous processes or " palpi" (usually four in number), but there is no dental apparatus. The
mouth opens into a gullet, which conducts to a distinct




MOLLUSCA: LAMELLIBRANCHIATA.                  303
stomach. On the right side of the stomach, and opening into
it, is, in many cases, a blind sac containing a peculiar transparent glassy body, which is known as the " crystalline stylet,"
but the functions of which are absolutely unknown.  The
intestine has its first flexure neural, perforates the wall of the
heart, and terminates posteriorly in a distinct anus, which is
always placed near the respiratory aperture. The liver is large
and well developed, but there are no salivary glands.
There is always a distinct heart, composed either of an
auricle and ventricle, or of two auricles and a ventricle. The
ventricle propels the blood into the arteries, by which it is distributed through the body. From the arteries it passes into
the veins, and is conducted to the gills, where it is aerated,
and is finally returned to the auricles.
The respiratory organs in all the  amnellibrcanz hiata consist
of two lamelliform gills, placed on each side of the body (fig.
io6, b). In some cases there is only one gill on each side of
the body, the external pair of branchixe being absent. The
gills are in the form of membranous plates, composed usually
of tubular rods, which support a network of capillary vessels,
and are covered with vibrating cilia, whereby a circulation of
the water is maintained over their surfaces. In some bivalves
the margins of the mantle are united to one another, so that a
closed branchial chamber is produced; and in the others the
arrangements for the admission of fresh and the expulsion of
effete water are equally perfect, though there is no such chamber. In those in which the mantle-lobes are united at their
margins, there are two orifices, one of which serves to admit
fresh water, whilst the effete water is expelled by the other.
The margins of these "inhalant" and "exhalant" apertures
are often drawn out and extended into long muscular tubes
or "siphons," which may be either free, or may be united to
one another along one side (fig. io6, ss), and which can usually
be partially or entirely retracted within the shell by means of
special muscles, called the " retractor-muscles of the siphons."
These siphons are more especially characteristic of those Lamellibranchs which spend their existence buried in the sand,
protruding their respiratory tubes in order to obtain water, and
with it such nutrient particles as the water may contain. The
presence or absence of retractile siphons can be readily determined merely by inspection of the dead shell.  In those
bivalves in which siphons are not present, or if present are not
retractile, the " pallial line " in the interior of the shell is unbroken in its curvature, and presents no indentation (fgzteg7ropaliiia).  In those, on the other hand, in which retractile




304               MANUAL OF ZOOLOGY.
siphons exist, the pallial line does not run in an unbroken
curve, but is deflected inwards posteriorly, so as to form an
indentation or bay, which is termed the "pallial sinus," or
"siphonal impression," and is caused by the insertion of the
retractor-muscle of the siphon. Those bivalves in which this
sinus exists form the section Silzzt-paZiaia (fig. 107, 2).
3
I' 2
3
2      a                  a
Fig. Io7.-Shells of Lamellibranchiata. T. C/yclas aMmnica, a dimyary shell with an
entire pallial line. 2. TacszpCdlcasira, a dilnyary shell with- an indented pallial line.
3. Pernua epiA/iztiun, a monomyary shell (after Woodward).  a Pallial line; b
Muscular impressions left by the adductors; c Siphonal impression.
The nervous system of the amnellibranchiata is composed of
the three normal ganglia-the cephalic, the pedal, and the
parieto-splanchnic or branchial.  The so-called "organ  of
Bojanus" of the bivalves is doubtless mainly concerned in
excretion, and in all probability represents the kidney. There
is one of these organs on each side of the body, each composed of two sacs separated from those of the opposite side
by a venous sinus. Or it may be looked upon as a double
organ composed of two bilaterally symmetrical halves. It is
situated just below the "pericardium," and communicates with
it and also with the mantle-cavity. Though undoubtedly performing the functions of a kidney, the organ of Bojanus is also
connected in some cases with reproduction, and it appears to
correspond to the " pseudo-hearts " of the Brachiojpoda.
The majority of the bivalves are dicecious, but in some the
sexes are united in the same individual.   The young are
hatched before they leave the parent, and are, when first liberated, ciliated and free-swimming.
The muscular system of the Lamellibranchs is well developed. Besides the muscular margin of the mantle, and the
muscles of the siphons (when these exist), there are also present other muscles, of which the most important are the muscles which close the shell and those which form  the "foot"
(fig. Io6, ). The "foot" is present in the majority of bivalves,
though it is not such a striking feature as in the Gasteropoda.




MOLLUSCA: LAMELLIBRANCHIATA.             305
It is essentially a muscular organ, developed upon the ventral
surface of the body, its retractor-muscles usually leaving distinct impressions or scars (the "pedal impressions") in the
interior of the shell.  In many the foot subserves locomotion,
but in the attached bivalves it is rudimentary, and iln others (as
in the Scallops) locomotion is effected by the alternate opening
and closure of the valves. In some-such as the ordinary
Mussel-the foot is subsidiary to a special gland, which secretes
the tuft of silky threads ("byssus") whereby the shell is attached to foreign objects.  This gland secretes a viscous
material, which the foot moulds into threads.
The valves of the shell are brought together by one or two
muscles, which are called the "adductor muscles "-those
bivalves with only one being called Mfonomyaria, whilst those
which possess two are termed Dimyaria.  In most there are
two adductor muscles (fig. io6, a a') passing between the inner
surfaces of the valves, one being placed anteriorly in front of
the mouth, the other posteriorly on the neural side of the intestine. In the monomyary bivalves the posterior adductor
is the one which remains, and the anterior adductor is absent.
The adductors leave distinct "muscular impressions" in the
interior of the shell, so that it is easy to determine whether
there has been one only in any given specimen, or whether
two were present.
The habits of the Lamnelibranchiafa are very various. Some,
such as the Oyster (Ostrea), and the Scallop (Pecten), habitually
lie on one side, the lower valve being the deepest, and the
foot being wanting, or rudimentary. Others, such as the Mussel
(Mrytilus) and the Pinna, are attached to some foreign object
by an apparatus of threads, which is called the "byssus," and
is secreted by a special gland. Others are fixed to some solid
body by the substance of one of the valves. Many, such as
the Myas, spend their existence sunk in the sand of the seashore or in the mud of estuaries.  Others, as the Phzolaies and
LithZdaomi, bore holes in rock or wood, in which they live.
Finally, many are permanently free and locomotive.
The Lamellibranchiata are divided into two sections, according as respiratory siphons are absent or present, as follows: —
SECTION A. ASIPHONIDA. - Animal without respiratory
siphons; mantle-lobes free; the pallial line simple and not
indented (Integro-pallialia).
This section comprises the families Ostreide, Avicui&de, Mytilidw;e Arcadce, Trigoniadie, and Unionide.
SECTION B. SIPHONIDA.-Animal with respiratory siphons;
mantle-lobes more or less united.




306                MANUAL OF ZOOLOGY.
Two subdivisions are comprised in this section.   In the
first the siphons are short, and the pallial line is simple (IntegropaZlialia); as is seen in the families Chamidce, Hzippuritidre,
Tridacnidae, Cardiadce, Lucinidee, Cycladidce, and Cyprinidae.
The second subdivision (Silnu-paliialia) is distinguished by
the possession of ong respiratory siphons, and a sinuated pallial
line, and it comprises the families Veneridce, MactridZ, Tellinidoe,
Solenide, JMyacidee, Anatinidae, GastrocheenidZe, and Pholadidce.
SYNOPSIS OF THE FAMILIES OF THE LAMELLIBRANCHIATA.
SECTION A. ASIPHONIDA.
arnz. I. Oshreidra. —Shell inequivalve, slightly inequilateral, free or
attached; hinge usually edentulous. Ligament internal. Lobes
of the mantle entirely separated; the foot small and byssiferous,
or wanting.   A single adductor.  Ill. Gen. Ostrea, Pctlen,
Spondylus, &c.
Falm. 2. Aviculidca.-Shell inequivalve, very oblique, attached by
a byssus; hinge nearly, or quite, edentulous. Mantle-lobes free;
anterior adductor small, leaving its impression within the umbo;
posterior adductor large and sub-central. Foot small. Ill. Gen.
Avicula, Inoce-ramus, Pinna.
Farn. 3. Afytilida.-Shell equivalve, umbones anterior, hinge edentulous; anterior muscular impression small, posterior large.
Shell attached by a byssus.  Mantle-lobes united between the
siphonal apertures. Foot cylindrical, grooved, and byssiferous.
Ill. Gen. Mytifus, Alodiola, Dreissena.
lFam. 4. Arcadae.-Shell equivalve; hinge long, with many comblike equal teeth.  Muscular impressions nearly equal.  Mantlelobes separated; foot large, bent, and deeply grooved. Ill. Gen.
Area, Pectunculus, Cucul/ca.
Ernm. 5. T7igoniadae.-Shell equivalve trigonal; hinge-teeth few,
diverging; umbones directed posteriorly.  Mantle open; foot
long and bent.  Ill. Gen. 7rigoonia, Axinus.
Fam. 6. Unionide.-Shell usually equivalve, with a large external
ligament.  Anterior hinge-teeth thick and striated; posterior
laminar, or wanting.  Mantle-lobes united between the siphonal
apertures.  Foot very large, compressed, byssiferous in the fry,
Il1. Gen. UnYio, Anzodion, MZillieria.
SECTION B. SIPHONIDA.
Subdivision I. Irntegro-pallialia.-Siphons short, pallial line simple.
Farn. 7. Chanzidcv..-Shell inequivalve, attached; hinge-teeth 2-I
(two in one valve and one in the other).  Addluctor impressions
large.  Mantle closed; pedal and siphonal orifices small and
nearly equal.  Foot very small.  Ill. Gen. Chazna, Dice-nas.
Eanm. 8. Iiipupsiti/Zkc. -" Shell inequivalve, unsymmetrical, thick,
attached by the ritit umbo; umlbones frequently camerated;
structure and sculpturing of valves dissimilar; ligament internal;
hinge-teeth 1-2; adductor impressions 2, large, those of the left
valve on prominent apophyses; pallial line simple, sub-marginal."
-(Woodward.) Ill. Gen. Hipszr-i/es, R'adioiles, Cap-ine/ll/a.




MOLLUSCA: LAMELLIBRANCHIATA.    307
Fam. 9. Tridecnidve.- Shell equivalve; ligament external; muscular
impressions blended, sub-central. Animal attached by a byssus,
or free. Mantle-lobes extensively united; pedal aperture large;
siphonal orifices surrounded by a thickened pallial border. Foot
finger-like and byssiferous. Ill. Gen. Tridacna.
Faen. Io. Cardiace. —Shell equivalve, heart-shaped, with radiating
ribs; cardinal teeth 2; lateral teeth I-I, in each valve. Mantle
open in front, siphons usually very short; foot large, sickleshaped.  Ill. Gen. Cardium, Hemnicardium, Conocardium.
Ezn. I I. Lzucinidte.-Shell orbicular, and free; hinge-teeth 1 or 2;
lateral teeth I-I, or obsolete. Mantle-lobes open below, with
one or two siphonal orifices behind; foot elongated, cylindrical,
or strap-shaped. Ill. Gen. Lucina, Di5plodonta, Kellia.
Enam. 12. CycladidwE. — Shell sub-orbicular, -closed; hinge with
cardinal and lateral teeth; ligament external. Mantle open in
front; I-2 siphons, more or less united.   Foot large, tongueshaped. Ill. Gen. Cyclas, Cyrena.
Fam. I3. CyprinidE.-Shell equivalve, closed; ligament external;
cardinal teeth I-3 in each valve, and usually a posterior tooth.
Mantle-lobes united behind by a curtain pierced with two siphonal
orifices. Foot thick, and tongue-shaped. Ill. Gen. Cyprina,
Astarte, Isocardia.
Subdivision II. Sinu-paleialia.-Respiratory siphons large; pallial
line sinuated.
Fam. 14. Veneridw.-Shell regular, sub-orbicular or oblong; ligament external; hinge with usually 3 diverging teeth in each valve.
Animal usually free and locomotive; mantle with a rather large
anterior opening; siphons unequal, more or less united. Foot
tongue-shaped, compressed, sometimes grooved and byssiferous.
111. Gen. Venus, Cythe-rea, Venerupis.
Faei. I5. Mactridae.-Shell equivalve, trigonal; hinge with two
diverging cardinal teeth, and usually with anterior and posterior
lateral teeth. Mantle more or less open in front; siphons united,
with fringed orifices; foot compressed.  Ill. Gen. Mactra,
Lutraria.
Eant. i6. Tellinide?.-Shell free, usually equivalve and closed;
cardinal teeth 2 at most, laterals I-I, sometimes wanting. Ligament on the shortest side of the shell, sometimes internal.
Mantle widely open in front. Siphons separate, long and slender;
foot tongue-shaped, compressed. Ill. Gen. Tellina, Psammnzobia,
Donax.
Feam. I7. Solenide-.-Shell elongated, gaping at both ends; ligament
external; hinge-teeth usually 2-3.  Siphons short and united
(in the long-shelled genera), or longer and partly separate (in the
genera with shorter shells). Foot very large and powerful. Gills
prolonged into the branchial siphon. Ill. Gen. Solen, Cultellus,
Solecurtus.
Fem. iS. Myacido.-Shell gaping posteriorly.  Mantle almost
entirely closed; siphons united, partly or wholly retractile. Foot
very small. Ill. Gen. Mya, Panop&ea, Glycimeris.
Fam. I9. Anatinid&.-Shell often inequivalve, with an external
ligament. Mantle-lobes more or less united; siphons long, more
or less united. Foot small.  Ill. Gen. Anatina, Pholadomrya,
Myochama.




308               MANUAL OF ZOOLOGY.
Fam. 20. Gastrochnid. —Shell equivalve, gaping, with thin eden.
tulous valves, sometimes cemented to a calcareous tube. Mantlemargins thick in front, united, with a small pedal aperture.
Siphons very long, united. Foot finger-shaped.  Ill. Gen. Gasroch/una, Saxicava, Aspergillum.
Famr. 21. Phoiadcida. —Shell gaping at both ends, without hinge or
ligament, often with accessory valves.  Animal club-shaped or
worm-like, with a short truncated foot. Mantle closed in front.
Siphons long, united to near their extremities. Ill. Gen. PioZlas,
Xylop haga, Teredo.
CHAPTER XLVII.
GA S TEROPODA.
DIVISION  ENCEPHALA, or CEPHALOPHORA. -  The remaining
three classes of the Mollusca proper all possess a distinctlydifferentiated head, and are all provided with a peculiar masticatory apparatus, which is known as the " odontophore." For
the first of these reasons they are often grouped together under
the name Encephala; and for the second reason they are
united by Huxley into a single great division, under the name
of Odontophora. Whichever name be adopted, the three classes
in question (viz., the Gastero}5oda, Pteroj5oda, and Cet/ialojoPda)
certainly show many points of affinity, and form a very natural
division of the Mollusca.  The Pteropoda, as being the lowest
class, should properly be treated of first, but it will conduce to
a clearer understanding of their characters if the Gaslte-opoda
are considered first.
CLASS II. GASTEROPODA.-The members of this class are
characterised by being never included in a bivalve shell; locomotion being effected by means of a broad, horizontally flattened, ventral disc-the "foot;" or by a vertically flattened,
ventral, fin-like organ. Flexure of intestine hbemal or neural.
This class includes all those Molluscous animals which are
commonly known as "univalves," such as the land-snails, seasnails, whelks, limpets, &c. The shell, however, is sometimes
composed of several pieces (multivalve), and in many there is
either no shell at all, or nothing that would be generally recognised as such. In none is there a bivalve shell.
In their habits the Gasteropods show many differences, some
being sedentary, but the great majority being free and locomotive.  In these latter, locomotion may be effected by the suc



MOLLUSCA: GASTEROPODA.                    309
cessive contractions and expansions of a muscular foot; but
some possess the power of swimming freely by means of a
modified fin-like foot.
In most of the Gasteroipoda the body is unsymmetrical, and is
coiled up spirally, " the respiratory organs of the left side being
usually atrophied." —(Woodward.)  The body is enclosed in a
" mantle," which is not divided into two lobes as in the Larzedlibranchziata, but is continuous round the body.  Locomotion
is effected by means of the " foot," which is usually a broad
muscular disc, developed upon the ventral surface of the body,
and not exhibiting any distinct division into parts. In the
Heteropoda, however, and in the Wing-shells (Strombid(e), the
foot exhibits a division into three portions-an anterior, the
" propodium;" a middle, the " mesopodium;" and a posterior
lobe, or " metapodium."
~In some, again, the upper and lateral surfaces of the foot
are expanded into muscular side-lobes, which are called " epipodia." In many cases the metapodium, or posterior portion
of the foot, secretes a calcareous, horny, or fibrous plate,
which is called the " operculum " (fig. Io9, o), and which serves
to close the orifice of the shell when the animal is retracted
within it.
The head in most of the Gasferojioda is very distinctly
marked out, and is provided with two tentacles and with two
eyes, which are often placed upon long stalks. Very often
there is an elongated retractile proboscis with ear-sacs, containing otoliths, at its base. The mouth is sometimes furnished with horny jaws, and is always
provided with a singular masticatory apparatus, called the "tongue" or "odontophore"
(fig. io8). " It consists essentially of a cartilaginous cushion, supporting, as on a pulley, an
elastic strap, which bears a long series of transversely-disposed teeth.  The ends of the strap
are connected with muscles attached to the
upper and lower surface of the hinder extremities of the cartilaginous cushions; and these
muscles, by their alternate contractions, cause Fig. o8. —Fragment
the toothed strap to work backwards and for-  of the lingual ribbon or odontowards over the end of the pulley formed by its  phore Of the conmanterior end. The strap consequently acts, after  mon Whelk (Buccinum undatuin),
the fashion of a chain-saw, upon any substance  magnified. (After
to which it is applied, and the resulting wear  Woodward.)
and tear of its anterior teeth are made good by the incessant
development of new teeth in the secreting sac in which the




310              MANUAL OF ZOOLOGY.
hinder end of the strap is lodged."-(Huxley.)  The teeth of
the odontophore (" lingual teeth ") are composed of silica, and
are usually arranged in a central (" rachidian") and two lateral
("pleural") rows.  The mouth leads by a gullet into a distinct
stomach, which is sometimes provided with calcareous plates
for the trituration of the food. The intestine is long, and its
first flexure is commonly " haemal," or towards that side of the
body on which the heart is situated; though in some the flexure
is " neural." Distinct salivary glands are usually present, and
the liver is well developed.
A distinct heart is usually present, composed of an auricle
and ventricle. In many Gasteropods it has been shown that
the blood-vessels form closed tubes, and that the arteries and
veins are connected by an intermediate system of capillaries,
instead of merely communicating through the interstices and
lacunas between the tissues.  It seems also certain that, in
general at any rate, there is no direct connection between the
blood-vessels and the outer medium, though,.in some cases,
such-a communication seems undoubtedly to exist. Respiration is very variously effected; one great division (Branchiogasterojoda) being constructed to breathe air by means of
water; whilst in another section (Pulmogasteropoda) the respiration is aerial. In the former division respiration may be
effected in three ways. Firstly, there may be no specialised
respiratory organ, the blood being simply exposed to the water
Fig. og9. -Anuzllaria canaliculata, one of the Apple-shells. o Operculum;
s Respiratory siphon.
in the thin walls of the mantle-cavity (as in some of the Heteropoda). Secondly, the respiratory organs may be in the form of
outward processes of the integument, exposed in tufts on the
back and sides of the animal (as in the Nudibranc/iata).
Thirdly, the respiratory organs are in the form of pectinated




MOLLUSCA: GASTEROPODA.                3 I I
or plume-like branchiae, contained in a more or less complete
branchial chamber formed by an inflection of the mantle. In
many members of this last section the water obtains access to
the gills by means of a tubular prolongation or folding of the
mantle, forming a " siphon," the effete water being expelled by
another posterior siphon similarly constructed. In the airbreathing Gasteropods, the breathing organ is in the form of
a pulmonary chamber, formed by an inflection of the mantle,
and having a distinct aperture for the admission of air.
The nervous system in the Gasteropoda has its normal composition of three principal pairs of ganglia, the supra-cesophageal or cerebral, the infra-cesophageal or pedal, and the parietosplanchnic; but there is a tendency to the aggregation of these
in the neighbourhood of the head. The organs of sense are
the two eyes, and auditory capsules placed at the bases of the
tentacles, the latter being tactile organs.
The sexes are mostly distinct, but in some they are united
in the same individual. The young, when first hatched, are
always provided with an embryonic shell, which in the adult
may become concealed in a fold of the mantle, or may be
entirely lost. In the branchiate Gasteropods the embryo is
protected by a small nautiloid shell, within which it can entirely retract itself; and it is enabled to swim freely by means
of two ciliated lobes arising from the sides of the head; thus,
in many respects, resembling the permanent adult condition of
the Pteropoda. In the branchiate Gasteriopoda, however, of
fresh waters, the young do not possess these ciliated buccal
lobes.
Shell of the Gasteropoda.-The shell of the Gasteropods is
composed either of a single piece (univalve), or of a n'umber
of plates succeeding one another from before backwards (multivalve). The univalve shell is to be regarded as essentially
a cone, the apex of which is more or less oblique. In the
simplest form of the shell the conical shape is retained without
any alteration, as is seen in the common Limpet (Paella).
In the great majority of cases, however, the cone is considerably elongated, so as to form a tube, which may retain this
shape (as in Dentaliium), but is usually coiled up into a spiral.
The "spiral univalve " (fig.  i o) may, in fact, be looked upon
as the typical form of the shell in the Gasteropoda. In some
cases the coils of the shell-termed technically the "whorls"
-are hardly in contact with one another (as in Vermzetus).
More commonly the whorls are in contact, and are so amalgamated that the inner side of each convolution is formed by the
pre-existing whorl.  In some cases the whorls of the shell




31I2            MANUAL OF ZOOLOGY.
are coiled round a central axis in the same plane, when the
shell is said to be "discoidal" (as in the common freshwater shell Planorbis).  In most cases, however, the whorls
are wound round an axis in an oblique manner, a true spiral
being formed, and the shell becoming "' turreted," "trochoid,"
"turbinated," &c. This last form is the one which may be
looked upon as most characteristic of the Gasteropods, the shell
being composed of a liumber of whorls passing obliquely round
a central axis or "'columella," having the embryonic shell or
"nucleus " at its apex, and having the mouth or "aperture?"
of the shell placed at the extremity of the last and largest of
the whorls, termed the "body-whorl." The lines or grooves
formed by the junction of the whorls are termed the " sutures,"
and the whorls above the body-whorl constitute the "spire" of
the shell. The axis of the shell (columella) round which the
whorls are coiled is usually solid, when the shell is said to be
"imperforate;" but it is sometimes hollow, when the shell is
said to be "perforated," and the aperture of the axis near the
mouth of the shell is called the "umbilicus." The margin of
the "aperture" of the shell is termed the " peristome," and is
composed of an outer and inner lip, of which the former is
often expanded or fringed with spines. When these expansions or fringes are periodically formed, the place of the mouth
of the shell at different stages of its growth is marked by
ridges or rows of spines, which cross the whorls, and are called
"varices."  In most of the phytophagous Gasteropods (Holostoma/a) the aperture of the shell (fig. IIO, a) is unbrokenly
round or "entire," but in the carnivorous forms (Siphonoslomata) it is notched, or produced into a canal (fig. IIo, b).
Often there are two of these canals, an anterior and a posterior,
but they do not necessarily indicate the nature of the food, as
their function is to protect the respiratory siphons.  The
animal withdraws into its shell by a retractor-muscle, which
passes into the foot, or is attached to the operculum; its scar
or impression being placed, in the spiral univalves, upon the
columella.
In the multivalve Gasteropods, the shell is composed of
eight transverse imbricated plates, which succeed one another
from before backwards, and are imbedded in the leathery or
fibrous border of the mantle, which may be plain, or may be
beset with bristles, spines, or scales.




MOLLUSCA: GASTEROPODA.                313
CHAPTER XLVIII.
DIVISIONS OF THE GASTEROPODA.
THE GasteropodaZ are divided into two primary sections or
sub-classes, according as the respiratory organs are adapted
for breathing air directly, or dissolved in water: termed
respectively the Pulmonifera or- Pulimogasteropoda, and the
Branc/hifera or Branchiogasteropoda.
SUB-CLASS A. BRANCHIFERA or BRANCHIOGASTEROPODA.In this sub-class respiration is aquatic, effected by the thin
walls of the mantle-cavity, by external branchial tufts, or by
pectinated or plume-like gills, contained in a more or less
complete branchial chamber. Flexure of intestine hanmal.
This sub-class comprises three orders - viz., the Prosobranchiata, the Opisthobranchiata, and the Nucleobranchia/a or
Heteropoda.
ORDER I. PROSOBRANCHIATA.-The members of this order
are defined as follows: —"Abdomnen well developed, and protected by a shell, into which the whole animal can usually
retire. Mantle forming a vaulted chamber over the back of
the head, in which are placed the excretory orifices, and in
which the branchix are almost always lodged. Branchic
pectinated or plume-like, situated (proson) in advance of
the heart.  Sexes distinct."-M.-Edwards.  (See Woodward's'Manual.')
The order Prosobranchiata includes all the most characteristic members of the Branchiate Gasteropods, and is divisible
into two sections, termed respectively Sohonostomata and
Holostomata, according as the aperture of the shell is notched
or produced into a canal, or is simply rounded and " entire."
The Szphonostomata, of which the common Whelk (BuccinIum undatum) may be taken as an example, are all marine,
and are mostly carnivorous in their habits. The following
families are comprised in this section:-Stl-ombide& (Wing-shells), AMfricide, Buccinidce (Whelks), Conide (Cones), Volu/idae, and Cypreidce (Cowries).
The Holostomata, of which the Common Periwinkle (Lillorina littorea) is a good example, are either spiral or limpetshaped, in some few instances tubular, or multivalve; the aperture of the shell being in most cases entire. They are mostly
plant-eaters, and they may be either marine or inhabitants of
fresh water. The following families are included in this section: —Nfaticide, Pyrandel/i /dce, Cerithiadre, A'Mcaniade, Turri



314               MANUAL OF ZOOLOGY.
tellidce, Littorinidat. (Periwinkles), PaludinidCE   (River-snails)
Aeritid&e, Turbinidae (Top-shells), Haliotidze (Ear-shells), Fissurellide (Key-hole Limpets), CalyptrceidE  (Bonnet Limpets),
Patellidee (Limpets), Dentalide (Tooth-shells), and Chitonide.
Fig. nxo.-Gasteropoda. a Holostomatous shell (Turritella communis);
b Siphonostomatous shell (Buccinum undatum).
ORDER II. OPISTHOBRANCHIATA.  This order is defined as
follows:
"Shell rudimentary, or wanting.  Branchiz arborescent or
fasciculated, not contained in a special cavity, but more or less
completely exposed on the back and sides, towards the rear
(opisthen) of the body.  Sexes united."-M.-Edwards.  (See
Woodward's'Manual.')
The Opisthobranchiala, or "Sea-slugs," may be divided into
two sections, the Tecdibranchiata and Nudibranchiata, according as the branchiwe are protected or are uncovered.
The first section, that of the Tectibranchiata, is distinguished
by the fact that the animal is usually provided with a shell,
both in the larval and adult state, and that the branchie areprotected.by the shell or by the mantle. Under this family
are included the families of the Tornatellidce, Bullidee (Bubble
shells), Apjlysiad&e (Sea-hares), Pleurobranchidee and Phyllidiadee.
In the second section, that of the Nudibranchiata (fig. I i i),
the animal is destitute of a shell, except in the embryo condition, and the branchiwe are always placed externally on the
back or sides of the body. This section comprises the families
Doridee (Sea-lemons), Tri/oniadtE, ]Eoaidte, P/Zhyilrloidce, and




MOLLUSCA: GASTEROPODA.                    315
Elysiad&.  Specimens of the Sea-slugs and Sea-lemons may at
any time be found creeping about on sea-weeds, or attached
to the under surface of stones at
low water.  The head is furnished
with tentacles, which appear to be
rather connected with the sense of
smell than to be used as tactile
organs; and behind the tentacles
are generally two eyes.  The ner- Fig. I-Ii -Nudibranchiata. Doris
Yohnstoni, one of the Sea-lemons.
vous system is extremely well developed, and would lead to the belief that the N2udibranchs
are amongst the highest of the Gastcrojpoda.  Locomotion is
effected, as in the true Slugs, by creeping about on the flattened foot.
ORDER III. NUCLEOBRANCHIATA OR HETEROPODA.-This
order is defined by the following characteristics:-Animal
provided with a shell, or not, free-swimming and pelagic;
locomotion effected by a fin-like tail, or by a fan-shaped, vertically flattened, ventral fin.
Fig. I 12.-Heteropoda. Carizaria cymbiuLm. f Proboscis; t Tentacles; b Branchiae;
s Shell; f Foot; d Disc. (After Woodward.)
The Heteropojda are pelagic in their habits, and are found
swimming at the surface of the sea.  They are to be regarded
as the most highly organised of all the Gasteropoda, at the
same time that they are not the most typical members of the
class.  Some of them can retire completely within their shells,
closing them with an operculum; but most have large bodies,
and the shell is either small or entirely wanting.  They swim
by means of a flattened ventral fin, or by an elongated tail,
and adhere at pleasure to sea-weed by a small sucker situated
on the side of the fin.  These organs are merely modifications
of the foot of the ordinary Gasteropods; the fin-like tail being
15




316              MANUAL OF ZOOLOGY.
the " metapodium" (as shown by its occasionally carrying an
operculum), the sucker being the " mesopodium," and the ventral fin being a modified "propodium." The " epipodia " are
apparently altogether wanting. Respiration is sometimes carried on by distinct branchiae, but in many cases these are
wanting, and the function is performed simply by the walls of
the pallial chamber.
The Heteropoda are divided into the two families Firolia&
and Atlantidce, the former characterised by having a small shell
covering the circulatory and respiratory organs, or by having
no shell at all; whilst in the latter there is a well-developed
shell, into which the animal can retire, and an operculum is
often present.
SUB-CLASS B. PULMONIFERA or PULMOGASTEROPODA.-In
this sub-class of the Gasteropoda respiration is aerial and is
carried on by an inflection of the mantle, forming a pulmonary
chamber, into which air is admitted by an external aperture.
The flexure of the intestine is neural, and the sexes are united
in the same individual.
Fig. 113.-Liznax Sowerbyi, one of the Slugs. (After Woodward.)
The Pulmonifera include the ordinary land-snails, slugs,
pond-snails, &c., and are usually provided with a well-developed
shell, though this may be rudimentary (as in the slugs), or
even wanting. Though formed to breathe air directly, many
of the members of this sub-class are capable of inhabiting
fresh water.  The common Pond-snails are good examples of
these last. The condition of the shell varies greatly. Some,
such as the common Land-snails, have a well-developed shell,
within which the  animal can withdraw  itself completely.
Others, such as the common Slugs (fig. 113) have a rudimentary shell, which is completely concealed within the mantle.
Others are entirely destitute of a shell. They are divided into
two sections as follows:Section I. Inoperculata.-Animal not provitded with an operculum to close the shell. In this section are included the families




MOLLUSCA: GASTEROPODA.                        317
HelicidcZ (Land-snails), Limacidae   (Slugs), Oncidiad'e, LiimnaeieT
(Pond-snails), and Auriculidae.
Section II. Operculata. —Shell closedt by an operculnm.  In this
section are included the families Cyclostomidc and Aciculidce.
SYNOPSIS OF THE FAMIIIES OF THE GASTEROPODA.
(AFTER WOODWARD.)
SECTION A. BRANCHIFERA.  Respiration aquatic, by the walls of the
mantle-cavity, or by branchiae.
ORDER I. PROSOBRANCHIATA. The branchive situated (p-oson) in advance of the heart.
Division a. Sizphonostomata.  Margin of tfe shell-aperture notched or
prodauced into a canal.
Fain. I. StrombidEe. Shell with an expanded lip, deeply notched
near the canal. Operculum claw-shaped. Foot narrow, adapted
for leaping. Ill. Gen. Strombus, Pteroceras.
Faim. 2. Muricidw. Shell with a straight anterior canal, the aperture
entire posteriorly. ~Foot broad. Ill. Gen. MIurex, Triton, Pyrula,
Fusus.
Fant. 3. Buccinidze.  Shell notched anteriorly, or with the canal
abruptly reflected, producing a kind of varix cn the front of the
shell.  Ill. Gen. Buccinzuol, Nassa, Purpura, Cassis, LBpla,
Oiv/a.
Fazln. 4. Confida.  Shell inversely conical, with a long narrow aperture, the outer lip notched at or near the suture.  Operculum
minute, lamellar.  Ill. Gen. Conus, Pleurotonza.
Fanm. 5. Volutid,. Shell turreted or convolute, the aperture notched
in front; the columella obliquely plaited.  No operculum.  Foot
very large; mantle often reflected over the shell. Ill. Gen. Volulta,
Mitra, Marg,,inella.
Fain. 6. Cyprzid&e.  Shell convolute, enamelled;  spire concealed,
aperture narrow, channelled at each end.  Outer lip thin in the
young shell, but thickened and inflected in the adult.  Foot
broad; mantle forming lobes which meet over the back of the
shell.  Ill. Gen. Cyprwa, Ovulum.
Division b. Holostomata.  Margin of the shell-aiperture "entire," rarely
notched or produced into a canal.
Fanm. I. Naticidre.  Shell globular, of few whorls, with a small spire,
outer lip acute, pillar often callous.  Foot very large; mantlelobes hiding more or less of the shell.  Gen. Azttica, Sizareltus.
Fain. 2. Pjramnidellidce.  Shell turreted, with a small aperture,
sometimes with one or more prominent plaits on the columella.
Operculum horny, imbricated. Ill. Gen. Pranridella, Cheinnitzia,
Eulima.
Fain. 3. Ctveithiad(e. Shell spiral, turreted; aperture channelled in
front, with a less distinct posterior canal. Lip generally expanded
in the adult.  Operculum horny and spiral. Ill. Gen. Cerithiztnm,
Potamzides, Apoorrhais.
Fant. 4. Melaniadce.  Shell spiral, turreted; aperture often channelled or notched in front; outer lip acute.  Optrculum horny
and spiral.  Ill. Gen. Melaniia, PalztdoNus.




318                  MANUAL OF ZOOLOGY.
Fam. 5. 7Zrritellidv.   Shell tubular, or spiral, often turreted;
upper part partitioned off; aperture simple. Operculum horny,
many-whorled. Foot very short. Branchial plume single. Ill.
Gen. Turritella, Vermetus, Scalaria.
Fam. 6. Littorinida.  Shell spiral, top-shaped, or depressed; aperture rounded and entire; operculum horny and pauci-spiral. Ill.
Gem. Littorina, Solariumn, Rissoa, Pizorus.
Faim. 7. Pahldinidae.  Shell conical or globular; aperture rounded
an I entire; operculum horny or shelly. Ill. Gen. Paludi/na,
Ampjullaria, Valvata.
Faen. 8. NeritiEe.  Shell thick, globular, with a very small spire;
aperture semi-lunate, its columellar side expanded; outer lip
acute.  Operculum shelly, sub-spiral.  Ill. Gen. Nerita, Pileolus,
Ner itidna.
Farn. 9. Tuzbinidx.  Shell turbinated (top-shaped), or pyramidal,
nacreous inside.  Operculum  horny and multi-spiral, or calcareous and pauci-spiral.  Ill. Gen. Turbo, Tliochus, DelJ/sinula,
Euomnphalus.
Fazr. Io. falioZtidw(.  Shell spiral, ear-shaped, or trochoid; aperture
large, nacreous. Outer lip notched or perforated. No operculum.
Mantle-margin with a posterior fold or siphon, occupying the slit
or perforation in the shell.  Metapodium rudimentary.  Ill. Gen.
Haliotis, Scissurella, Pleurotomzaria, Alurchzisonia, 2a,/haina.
Famrn. II. Fissurellidx. Shell conical, patelliform, with a notch in
the anterior margin, or a perforation at its apex, which is occupied
by an anal siphon. Muscular impression horse-shoe-shaped, open
in front.  Ill. Gen. Fissurella, Enmarginula, Parmophorus.
Fam. 12. Calyptraeidce.  Shell patelliform, with a more or less spiral
apex; interior simple, or divided by a shelly process to which the
adductor muscles are attached. Ill. Gen. Calyptrcea, Pileopsis.
Fam. 13. Patedlide.  Shell conical, with the apex turned forwards;
muscular impression horse-shoe-shaped, open in front. Foot as
large as the margin of the mantle. Respiratory organ in the form
of one or two branchial plumes, lodged in a cervical cavity; or of
a series of lamelle surrounding the animal between the body and
the mantle.  Ill. Gen. Patella, Acmea.
Famr. I4. Dentalidi. Shell tubular, symmetrical, curved, open at
both ends. Aperture circular. Foot pointed, with symmetrical
side-lobes.  Gen. Dentaliurn.*
Fam. 15. Chitonidce. Shell multivalve, composed of eight transverse
imbricated plates. Animal with broad creeping foot; branchitr
forming a series of lamellae between the foot and the mantle,
round the posterior part of the body. Ill. Gen. Ch/ziton, Cry5ptochiton.
ORDER TI. OPISTHOBRANCHIATA. Branchite placed towards the rear
(opisthen) of the body.
Section a. Tectibranchziata.  Bravnchia covered by the shell or mzantle;
a shell in most.  Sexes united.
Fain. I. Torsnatelhlide.  Shell external, spiral, or convoluted; aperture long and narrow; columella plaited.  Ill. Gen. Torn-ate/lz,
Cinulia.
* Denta/iurn is placed by Professor Huxley amongst the Ptersopoda, from
its rudimentary head, the neural flexure of the intestine, the nature of the
epipodia, and the characters of the larva.




MOLLUSCA: GASTEROPODA.                            319
JFam. 2. Bullidz. Shell convoluted, thin; spire small or concealed,
lip sharp. Animal more or less investing the shell. Ill. Gen.
Bulla, Cylichna, Philine.
Fam. 3. Aplysiadz.  Shell absent, or rudimentary and concealed
by the mantle.  Animal slug- like, with extensive side- lobes,
(epipodia), reflected over the back and shell.  Ill. Gen. Aplysia,
Dolabella.
Fanm. 4. Pleurobranchzide.  Shell patelliform, or concealed, rarely
wanting.  Mantle or shell covering the back of the animal.  Ill.
Gen. Pleurobranchus, Umbrella, Tylodina.
Eaim. 5. Pzhyllidiade.  Animal shell-less, covered by a mantle. Ill.
Gen. Phyllidia, Dziphyllidia.
Section b. Nudibranchiata. Animal destitute of a shell in the adult con.
dition.  Branchiw external, on the back or sides of the body.
Fam. 6. Doridc.  Ill. Gen. Doris.
Eam. 7. Tr-itoniadzc. Ill. Gen. Tr-itonia, Scyll a.
Fain. 8. zEolidc.  Ill. Gen. AEolis, Glaucus.
Eam. 9. Phyllirhoidce. Gen. Phyllirhoe.
Eam. Io. E'lysiadx.  Ill. Gen. Elysia, Acteonia.
ORDER III. NUCLEOBRANCHIATA or HETEROPODA. Shell present or
absent. Animal free-swimming and pelagic, with a fin-like tail,
or a flattened ventral fin.
Farn. I. Fi;-olidce.  Body large; branchire exposed on the back, or
covered b)y a small hyaline shell: locomotion by means of a ventral fin and a tail-fin.  Ill. Gen. Carinaria, Firola.
Eart. 2. AtzlantirAe.  Animal furnished with a well-developed shell
into which it can retire.  Branchiae contained in a dorsal mantlecavity.  Shell symmetrical, discoidal, sometimes with an operculum.  Ill. Gen. Atlanzt, BelleropAhon, Al/aclurea.
SECTION B. PULMONIFERA. Respiration aerial, by means of a pulmonary
chamber.
DIVISION I. INOPERCULATA.  Shell not provided with an operclurnt.
Fam. I. Helicidtr.  Shell external, capable of containing the whole
animal.  Ill. Gen. Helix, Bulimus, Clausilia, Pupa.
Enam. 2. Limacidte.  Shell rudimentary, usually internal or'partly
concealed by the mantle.  Ill. Gen. Limax, Parmacella, Testacella.
Farn. 3.  OncidiadeZ.  Shell wanting. Animal slug-like. Ill. Gen.
Oncidium, Vaginulus.
Eam. 4. Limtneidre.   Shell thin, horn-coloured, well developed.
Aperture simple, lip sharp.  Ill. Gen. Linnwa,  Physa, Azcyvlus,
Plano-obis.
Eanm. 5. Auriculide. Shell spiral, with a horny epidermis; aperture
elongated, denticulated.  Ill. Gen. Auricula, Conovulus.
DIVISION II. OPERCULATA.  Shell witlh an oJerculum.
Fan. 6. 6. CcloslomidxZ. Shell spiral, rarely elongated, often de.
pressed. Aperture nearly circular. Operculum  spiral. Ill. Gen.
Cyclostozma, C,cloahor-us, Pupina.
Am'. 7. Aciculidte.  <1. hll elongated, cylindrical; operculum  thlil,
and sub-spiral.  Gen. Acicula, Geomel/ania.




320              MANUAL OF ZOOLOGY.
CHAPTER XLIX.
PTEROPODA.
CLASS III. PTEROPODA.-The Pterojpoda are defined by being
free and pelaic, swimming by means of two wing-like appendages (epipodia), developed from each side of the anterior
extremity of the body. The flexure of the intestine is neural.
As to the position of the Pteropoda in the Molluscan scale,
they must be looked upon as inferior in organisation to any of
the Gasteropoda, of which class they are often regarded as the
lowest division. They permanently represent, in fact, the transient larval stage of the sea-snails.
Fig. 114. —Pteropoda. a Cleodora 5yramidala; b Cuvieria columnella.
(After Woodward.)
The Pteropods are all of small size, and are found swimming at the surface of the open ocean, often in enormous
numbers. Locomotion is effected by two wing-like fins, developed.from the sides of the head, and composed of the greatly
developed "epipodia."  The true "foot" is rudimentary and
rarely distinct, but the " metapodium" is sometimes provided
with an operculum. There is usually a symmetrical glassy
shell (fig. I 14), either consisting of a dorsal and ventral plate
united, or forming a spiral, but in some cases the body is
naked. The head is rudimentary, and bears the mouth, which
is occasionally tentaculate, and which is furnished with an
odontophore. There is a muscular stomach and a well-developed liver; and the flexure of the intestine is neural, so that
the anus is situated on the ventral surface of the body.
The heart consists of an auricle and ventricle. The respiratory organ is very rudimentary, and consists of a ciliated
surface, which is either entirely unprotected, or may be contained in a branchial chamber.
The ganglia of the nervous system " are concentrated into




MOLLUSCA: PTEROPODA.                      321
a mass below the cesophagus " (Woodward), and the eyes are
rudimentary.
The sexes are united in all the Pteropods, and the young
pass through a metamorphosis, having at first a bilobed ciliated
veil attached to the sides of the head.
The Pleropoda are divided into two orders, termed Thecosomata and Gyimnosornata; the former characterised by possessing an external shell and an indistinct head; the latter by
being devoid of a shell, and by having a distinct head, with
fins attached to the neck.
The Pteropoda, as already said, are found swimming near
the surface in the open ocean, and they are found in all seas
from the tropics to within the arctic circle, sometimes in such
numbers as to discolour the water for many miles. They are
nocturnal in their habits, and, minute as they are, they constitute in high latitudes one of the staple articles of diet of
the whale.  They themselves are, in turn, probably carnivorous, feeding upon small Crustaceans and other diminutive
animals. Though all the living forms are small, Geology leads
us to believe that there formerly existed comparatively gigantic
representatives of this class of the Mollusca.
SYNOPSIS OF TIlE FAMILIES OF THE PTEROPODA.
(AFTER WOODWARD.)
ORDER I. THIECOSONIATA.
Animal with an external shell; head indistinct; foot and tentacles rudimentary; mouth situated in a cavity formed by the union
of the locomotive organs. Respiratory organs contained within a
mantle-cavity.
Fainm. I. Hyaleidae.
Shell symmetrical, straight or curved, globular or needle-shaped.
Ill. Gen. Hyalea, Cleodora, 7zeca, Conularia.
Fam. 2. Limacinidar.
Shell minute, spiral, sometimes operculate. Ill. Gen. Lirnacina,
Spirialis.
ORDER II. GYMNOSOMATA.
Animal naked, without mantle or shell; head distinct; fins attached to the sides of the neck; gill indistinct.
iam. 3. CziidaZ.
Body fusiform, foot distinct, with a central and posterior lobe;
head with tentacles. I11. Gen. C7io, Pneumoderimon.




322             MANUAL O0  ZOCLOGY.
CHAPTER L.
CEPHA L OP OD.
CLASS IV. CEPHALOPODA.-The members of this class are
defined by the possession of eight or more arms placed in a
circle round the mouth; the body is enclosed in a muscular
mantle-sac, and there are two or four plume-like gills within
the mantle. There is an anterior tubular orifice (the "infundibulum" or "funnel "), through which the effete water of respiration is expelled. The flexure of the intestine is neural.
The Cepihalopoda, comprising the Cuttle-fishes, Squids,
Pearly Nautilus, &c., constitute the most highly organised of
the classes of the Molilusca. They are all marine and carnivorous, and are possessed of considerable locomotive powers. At
the bottom of the sea they can walk about, head downwards,
by means of the arms which surround the mouth, and which
are usually provided with numerous suckers or "acetabula."
They are also enabled to swim, partly by means of lateral
expansions of the integument or fins (not always present), and
partly by means of the forcible expulsion of water through the
tubular "funnel," the reaction of which causes the animal to
move in the opposite direction.
The majority of the living Cephalopods are naked, possessing only an internal skeleton, and this often a rudimentary one;
but the Argonaut (Paper Nautilus), and the Pearly Nautilus,
are protected with an external shell, though the nature of this
is extremely different in the two forms.
The integument in the Cuttle-fishes is provided iwith numerous little sacs, containing pigment-granules of different colours,
and termed "chromatophores."  By means of these many
species can change their colours rapidly, under irritation or
excitement.
The body in the Cepyhalopoda is symmetrical, and is enclosed
in an integument which may be regarded as a modification
of the mantle of the other Mo/llsca.  Ordinarily there is a
tolerably distinct separation of the body into an anterior
cephalic portion (prosoma), and a posterior portion, enveloped
in the mantle, and containing the viscera (zle/asonia).  The
head is very distinct, bearing a pair of large globular eyes, and
having the mouth in its centre.  The mouth is surrounded
by a circle of eight, ten, or more, long muscular processes, or
"arms" (fig. i I5), which are generally provided with rows of
suckers. Each sucker, or "acetabulum," consists of a cup



MOLLUSCA: CEPHALOPODA.                   323
shaped cavity, the muscular fibres of which converge to the
centre, where there is a little muscular eminence or papilla.
When the sucker is applied to
any surface, the contraction of the
radiating muscular fibres depresses
the papilla so as to produce a
vacuum below it, and in this way
each sucker acts most efficiently
as an adhesive organ.  In some
forms (Decapoda) the base of the
papilla, or piston, is surrounded
by a horny dentated ring, and in.
some others (as in OnQychzo/euthis)
the papillae are produced  into
long  claws.  In  the  Octopod                 il
Cuttle-fishes there are only eight
arms, and these are all nearly             i
alike.  In the Decapod Cuttlefishes there  are ten arms, but
two of these-called " tentacles"                   t   m1
-gare much  longer than  the                   i
others, and bear suckers only at
their extremities, which are enlarged and club-shaped.  In the
Pearly  Nautilus  the arms are   Fig. 115.- -ephalopoda. Sefi/ola
numerous, and  are devoid  of    Atlou//ca, one of the Cuttie-fishes
suckers.                            (after Woodward).
The arms are really produced by an extension of the margins of the "foot," or of the part corresponding to the foot of
the other MAfo7usca.  The "antero-lateral parts of each side of
the foot extend forwards beyond the head, uniting with it and
with one another; so that, at length, the mouth, from having
been situated, as usual, above the anterior margin of the foot,
comes to be placed in the midst of it. The two epipodia, on
the other hand, unite posteriorly above the foot, and where they
coalesce, give rise either to a folded muscular expansion, the
edges of which are simply in apposition, as in the Iautilus;
or to an elongated flexible tube, the apex of which projects
beyond the margin of the mantle, called the'funnel,' or'infundibulum,' as in the dibranchiate Cep/ha/opoda." —.
(Huxley.)
The mouth leads into a buccal cavity, containing two
powerful, horny, or partially calcareous mandibles, working
vertically like the beak of a bird; together with an "odontophore" or "tongue," the anterior part of which is sentient,




324              MANUAL OF ZOOLOGY.
whilst the remainder is covered with recurved spines. The
buccal cavity conducts by an cesophagus-into which salivary
glands usually pour their secretion-to a stomach, from which
an intestine is continued, with a neural flexure, to open on the
ventral surface of the animal at the base of the funnel. In
many cases there is also a special gland, called the "ink-bag,"
for the secretion of an inky fluid, which the animal discharges
into the water, so as to enable it to escape when. menaced or
pursued. The duct of the ink-bag opens at the base of the
funnel; but this apparatus is entirely wanting in the Tetrabranchiate Cephalopods, where, in consequence of the presence
of an external shell, this means of defence is not needed.
The respiratory organs are in the form of two or four plumelike gills, placed on the sides of the body in a branchial cavity
which opens anteriorly on the under surface of the body. At
the base of each gill, in the Cuttle-fishes, is a special contractile cavity, whereby the venous blood returned from the
body is driven through the branchiae. In addition to these
accessory organs-the so-called "branchial hearts "-there is
a true systemic heart, by which the aerated blood received
from the gills is propelled through the body. In the higher
Cephalopods a capillary system of vessels intervenes, in most
cases at any rate, between the arteries and the veins. The
admission of water to the branchiae is effected by the expansion
of the mantle so as to allow the entrance of the outer water into
the pallial chamber. The mantle then contracts, and the water
is forcibly expelled through the funnel, which is provided
with a valve permitting the egress of water, but preventing
its ingress.  By a repetition of this process, not only is respiration effected, but locomotion is simultaneously subserved;
the jets of water expelled from the funnel, by their reaction,
driving the animal in the opposite direction.
The nervous system is formed upon essentially the same
plan as in the other MlIol/sca, but it is more concentrated,
and the supra-oesophageal or cerebral ganglia are protected by
a cartilage, which is to be regarded as a rudimentary cranium.
This structure, therefore, presents us with the nearest alpproach which we have yet met with to the Vertebrate type of
organisation.
The sexes in all the CelphaZopoda are in different individuals,
and the reproductive process in the Dibranchiate section of
thle class (Cuttle-fishes) is attended with some very singular
phenomena.  In this order the ducts of the generative organs
open into the pallial chamber, and each individual, besides
the essential organs of reproduction (testis or ovary), gene



MOLLUSCA: CEPHALOPODA.                 325
rally possesses an accessory gland; that of the female secreting a viscid material which unites the eggs together, whilst
that of the male coats the spermatozoa, and aggregates them
into peculiar worm-like filaments, termed "spermatophores,"
or the "moving filaments of Needham." The spermatophore
is filled with spermatozoa, and possesses the power of expanding when moistened, rupturing, and expelling the contained spermatozoa with considerable force.  During the
congress of the sexes the male transfers the spermatophores to
the pallial chamber of the female, true intromission not being
possible. Further, in all the male Cuttle-fishes one of the
arms is specially modified to subserve reproduction; being
-n many cases so altered as to become useless as a locomotive
organ. The arm so affected, in the more striking forms, is
said to be "hectocotylised," and —like the metamorphosed
palpi of the male spiders-it serves to convey the seminal
fluid to the female. The mode in which this is effected varies
in different species. Thus, in the male Octdof s (the Poulpe)
the third right arm is primitively developed in a cyst, which
ultimately ruptures and liberates the metamorphosed arm,
which then appears to be of greater size than the corresponding arm  on the left side, and to terminate in an oval plate
(fig. i 6). To this terminal plate the spermatophore is probably transmitted, but the arm itself probably remains permanently attached to the animal. It is asserted, however, that
in the form figured below (Octopus careza) the hectocotylisec
arm is detached and deposited in the pallial chamber of the
female; being reproduced after each generative act. In 7remioctopus the third right arm of the male is "hectocotylised,"
and is converted into a vermiform  body, with two rows of
ventral suckers, and an oval appendage or sac behind, which
contains spermatozoa.  Besides the suckers, the anterior part
of the back is fringed with a number of so-called " branchial"
filaments.
In the A.gobnaut the male is not more than an inch in length,
is devoid of a shell, and has its third left arm hectocotylised.
This arm is developed in a cyst, which is ruptured by the
movements of the "hectocotylus," which then appears as a
small worm-like body, with a filiform appendage in front, with
two rows of alternating suckers, and a dorsal sac with numerous " chromatophores." The duct of the testis probably opens
into the base of the hectocotylus, which is ultimately detached,
and is deposited by the male within the pallial chamber of the
female. When first discovered in this position, it was described
as a parasitic worm under the name of " Hectocotylus;" sub



326               MANUAL OF ZOOLOGY.
sequently it was described as the entire male, and it is only
recently that its true nature has been fully ascertained.
Fig. zI6. —. Ocloqus carena (male), showing cyst in place of the third arm. 2. Ventral side of an individual, more developed, with the hectocotylus (a). (After
Woodward.)
The size/l of the Cephaoy5oda is sometimes external, sometimes internal. The internal skeleton is known as the " cuttlebone," " sepiostaire," or " pen " (g'adi/us), and may be either
corneous or calcareous.  In some cases it is rendered complex
by the addition of a chambered portion or "phragmacone,"
which is to be regarded as a visceral skeleton or " splanchnoskeleton."  In ~Spir/Za the phragmacone is the sole internal
skeleton, and is coiled into a spiral, the coils of which lie in
one plane, and are near one another, but not in contact.  It
thus resembles the shell of the Pearly Nautilus, but it is izlterizal,
and differs, therefore, entirely from  the external shell of the
latter.  The only living Cephalopods which are provided with
an external shell are the Paper Nautilus (Agonaurzta), and the
Pearly Nautilus (Nautiauis _povailfius); but not only is the struc



MOLLUSCA: CEPHALOPODA.                 327
ture of the animal different in each of these, but the nature of
the shell itself is entirely different. The shell of the Argonaut
(fig. II7) is involuted, but is not divided into chambers, and
it is secreted.by the webbed extremities of two of the dorsal
arms of the female.  The arms are bent backwards, so as to
allow the animal to live in the shell, but there is in reality no
organic connection between the shell and the body of the
animal. In fact, the shell of the Argonaut, being confined to
the female, and serving by its empty apex as a receptacle for
the ova, may be looked upon as a "nidamental shell," or as
it is secreted by a modified portion of the foot, it may more
properly be regarded as a " pedal shell." The shell of the
Pearly Nautilus (fig. i I9), on the other hand, is a true pallial
shell, and is secreted by the body of the animal, to which it is
organically connected. It is involuted, but it differs from the
shell of the Argonaut in being divided into a series of chambers
by shelly partitions or septa, which are pierced by a tube or
" siphuncle," the animal itself living in the last chamber only
of the shell.
The Cephaoapoda are divided into two extremely distinct and
well-marked orders, termed the Dibranchiala and the Tetrabranchiata.  The former is characterised by the possession of
two branchize only, and comprises the Cuttle-fishes, Squids,
and the Paper Nautilus.  The latter is distinguished by the
presence of four gills, and, though abundantly represented in
past time, has no other living representative than the Pearly
Nautilus alone.
CHAPTER LI.
DIVISIONS OF THE CEPHALOPODA.
ORDER I. DIBRANCHIATA. —The members of this order of the
Cep/alopoda are characterised as being swimming animals, almost invariably naked, with never more than eight or ten arms,
which are always provided with suckers.  There are two
branchioe, which are furnished with branchial hearts; an inksac is always present; the funnel is a complete tube, and the
shell is internal, or, if external, is not chambered.
The Cuttle-fishes are rapacious and active animals, swimming freely by means of the jet of water expelled from the
funnel.  The arms constitute powerful offensive weapons,




328               MANUAL OF ZOOLOGY.
being excessively tenacious in their hold, and being sometimes
provided with a sharp claw in the centre of each sucker. They
are mostly nocturnal oi crepuscular animals, and they sometimes attain to a great size. They may be divided into two
sections, Octopoda  and  Decapoda, according as they have
simply eight arms, or eight arms and two additional "tentacles."
SECTION  A. OCTOPODA.-The Cephalopods comprised in
this section are distinguished by the possession of not more
than eight arms, which are
providedwith sessile suckers. The shell is internal
and rudimentary; in one
instance only (the Argonaut) external. The body
is  short and bursiform,
and  ordinarily  without
fins.
This section comprises
the two families of the
Argonzautidce, and the Octopodidce.  In the former
of these there is only the
single  genus Ar4ro,a,o/.a
(the Paper Sailor, or the
Paper Nautilus), of which
the female and male differ
greatly fiom one another.
The female Argonaut (fig.
I I7) is protected by a thin
sillc-ch/lab bcrcd shell, in
Fig. 1T7. —Ar'onanto ar, the "Paper Nau- form sylmmetrical and intilus," female. Tl e.illimal is relpresc.ted ill voluted which is secreted
its shell, but the webbed dorsal arms are separated from the shell, which they ordinarily by the webbed extremiembrace.                         ties of the dorsal arms,
but is not attached in any way to the body of the animal. It
sits in its shell with the funnel turned toward the keel, and the
webbed arms applied to the shell. The male Argonaut is
much smaller than the female (about an inch in length), and is
not protected by any shell. The third left arm is developed
in a cyst, and ultimately becomes a "hectocotylus," and is
deposited by the male in the pallial chamber of the female.
In the Octpoadido (or Poulpes) there are eight arms, all
similar to one another, and united at the base by a web. There
is an internal rudimentary shell, represented by two short




MOLLUSCA: CEPIIALOPODA.                   229
styles encysted in the substance of the mantle.-(Owen.) The
body is seldom provided with lateral
fins. The third right arm of the male
is primarily developed in a cyst, and
ultimately becomes " hectocotylised."
SECTION B. DECAPODA.-The Cephalopods of this section have eight
arms and two additional "tentacles,"
which are much longer than the true
arms, are retractile, and have expanded club-shaped extremities (fig. II5)-               a
The suckers are pedunculated; the
body is always provided with lateral
fins, and the shell is always internal.
This section comprises the three
living families of the Teuthidea, Sepiade, and the SpirudiwdE, and the extinct
family of the Belemnitide.
The family of the Teut/hidvc comprises the Calamaries or Squids, characterised by the possession of an
elongated  body  with  lateral fins.
The shell is internal and horny, consisting of a median shaft and of two
lateral wings; it is termed the " gladius " or " pen," and in old specimens
several may be found lodged in the
mantle, one behind the other. In
the common Calamary (Iorigo) the
fourth left arm of the male is metamorphosed towards its extremity to
subserve reproduction.
In the family of the Sepiada? the
internal shell is calcareous ("cuttlebone" or "sepiostaire"), and is in
the form of a broad plate, having an
imperfectly chambered apex.   The  Fig. I8. —Diagram of Belembroad laminated plate is extremely   nite (after Professor Phillips).
light and spongy, and the chambered   r Horny pen or epro-ostracumo;"n i Chambered "phragapex is called the "mucro."  In the   macone in its cavity (a) or
living members of the family the body
is provided with long lateral fins, sometimes as long and as wide
as the body itself.
In the singular family of the Spirulid& the internal skeleton is
in the form of a nacreous, discoidal shell, the whorls of which




330             MANUAL OF ZOOLOGY.
are not in contact with one another, and which is divided into
a series of chambers by means of partitions or septa which are
pierced by a ventral tube or " siphuncle." The body is provided
with minute terminal fins, and the arms have six rows of small
suckers. The shell of the Spirula-commonly known as the
"post-horn "-is similar in structure to the shell of the Alaulilus, but it is lodged in the posterior part of the body of the
animal, and is therefore internai, whereas the shell of the
latter is external. It really corresponds to the " phragmacone"
of the Belemnite. Though the shell occurs in enormous numbers in certain localities. a s'ngle perfect specimen of the animal
is all that has been hitherto obtained.
In the extinct family of the Belenznitiid, our knowledge is
chiefly confined to the hard parts.  Certain specimens, however, have been discovered which show that the Bedcmzoitc had
essentially the structure of a Cuttle-fish, such as the recent
Sepia. The body was provided with lateral fins; the arms
were eight, furnished with horny hooks, with two " tentacles;"
and probably the mouth was provided with horny mandibles.
An ink-bag was present. The internal skeleton of a Belemnite (fig.  i8) consists of a chambered cone-the "phragmacone"-the septa of which are pierced with a marginal tube
or "siphuncle."  In the last chamber of the phragmacone is
contained the ink-bag, often in a well-preserved condition.
Anteriorly the phragmacone is continued into a horny lamina
or " pen" (the "pro-ostracum" of Huxley), and posteriorly it
is lodged in a conical sheath or "alveolus," which is excavated
in the substance of a nearly cylindrical, fibrous body, the
"guard" (fig. I 8, g), which projects backwards for a longer
or shorter distance, and is the part most usually found in a
fossil condition.
ORDER II. TETRABRANCHIATA.-The members of this order
of the Cephalopoda are characterised by being creeping animals,
protected by an external, many-chambered shell, the septa
between the chambers of which are perforated by a membranous or calcareous tube, termed the "siphuncle."  The arms
are numerous, and are devoid of suckers; the branchiae are
four in number, two on each side of the body; the funnel does
not form a complete tube; and there is no ink-bag.
Though abundantly represented by many and varied extinct
forms, the only living member of the Tetrabiranchiata is the
Pearly Nautilus,- which has been -long known by its beautiful
chambered shell, but the soft parts of which can hardly be said
to be known by more than one perfect specimen, which was
examined by Professor Owen.




MOLLUSCA: CEPHALOPODA.                    331
The soft structures in the Pearly Nautilus may be divided
into a posterior, soft, membranous mass (metasoma), containing the viscera, and an anterior muscular division, comprising
the head (_prosoma); the whole being contained in the outermost, capacious chamber (the body-chamber) of the shell, from
which the head can be protruded at will. The shell itself (fig.
i i 9) is involuted and many-chambered, the animal being contained successively in each chamber, and retiring from it as its
size becomes sufficiently great to necessitate the acquisition of
more room. Each chamber, as the animal retires from it, is
walled off by a curved, nacreous septum; the communication
between the chambers being still kept up by a membranous
Fig. 9zg.-Pearly Natltilus (NVauilizts fpoAiz/ius).  a Mantle; b Its dorsal fold;
c Hood; o Eye; t. Tentacles; f Funnel.
tube or siphuncle, which opens at one extremity into the pericardium, and is continued through the entire length of the
shell.  The position of the siphuncle is in the centre of each
septum.
Posteriorly the mantle of the Nautilus is very thin, but it is
much thicker in front, and forms a thick fold or collar surrounding the head and its appendages. From the sides of the
head spring a great number of muscular prehensile processes
or "arms," which are annulated, but are not provided with
cups or suckers.  In the centre of the head is the mouth, surrounded by a circular fleshy lip, external to which is a series
of labial processes. The mouth opens into a buccal cavity,




332             MANUAL OF ZOOLOGY.
armed with two horny mandibles, partially calcified towards
their extremities, and shaped like the beak of a parrot, except that the under mandible  is the longest.  There is
also a "tongue," which is fleshy and sentient in front, but is
armed with recurved teeth behind. The gullet opens into a
large crop, which in turn conducts to a gizzard, and the intestine terminates at the base of the funnel. On each side of the
crop is a well-developed liver.
The heart is contained in a large cavity, divided into several
chambers, and termed the " pericardium."-(Owen.)  The respiratory organs are in the form of four pyramidal branchie,
two on each side.
The chief masses of the nervous system are the cerebral and
infra-cesophageal ganglia, which are partially protected by a
cartilaginous plate, which is to be regarded as a rudimentary
cranium, and which sends out processes for the attachment of
muscles. The organs of sense are two large eyes, attached
by short stalks to the sides of the head, and two hollow
plicated subocular processes, believed to be olfactory in their
function.
The reproductive organs of the female consist of an ovary,
oviduct, and accessory nidamental gland.
There is no ink-bag, and the funnel does not form a complete tube, but consists of two muscular lobes, which are simply
in apposition. It is the organ by which swimming is effected,
the animal being propelled through the water by means of the
reaction produced by the successive jets emitted from the
funnel. The function of the chambers of the shell appears
to be that of reducing the specific gravity of the animal to near
that of the surrounding water, since they are most probably
filled with some gas secreted by the animal. The function of
the siphuncle is unknown, except in so far as it doubtless serves
to maintain the vitality of the shell.
SHELL OF THE TETRABRANCHIATA. -The shells of all the
Tetrabrancizialt agree in the following points:i. The shell is external.
2. The shell is divided into a series of chambers by plates
or " septa," the edges of which, where they appear on the shell,
are termed the "sutures."
3. The outermost chamber of the shell is the largest, and is
the one inhabited by the animal.
4. The various chambers of the shell are united by a tube,
termed the " siphuncle."
Agreeing in all these fundamental points of structure, two
very distinct types of shell may be distinguished as character



MOLLUSCA: CEPHALOPODA.                        333
istic of the two families Xautilid& and Ammonitidce, into which
the order Telrabranzcliata is divided.
In the family XaIutiiidce (fig. I20), the "septa" of the shell
are simple, curved, or slightly lobed; the "sutures" are more
or less completely plain; and  the "siphuncle" is central;
sub-central, or internal (i.e., on the concave side of the curved
shells).
In the family Ammonitiidae  (fig. 120), dn the other hand, the
septa are folded and complex; the sutures are angulated, zigzag, lobed, or foliaceous; and the siphuncle is external (i.e., on
the convex side of the curved shells).
g.o:b t  r X  d t e I
Fig. 120.-Diagram to illustrate the position of the siphuncle and the form of the septa
in various Tetrabranchiate Cephalopoda. The ipper row of figures represents
transverse sections of the shells, the lower row represents the edges of the septa.
a a A ineionile or Baculilte; b b Ceratite; c c Goniatite; dd C/ymelia/; e e Nautitls or Ort/zoceras.
In both these great types of shell, a series of representative
forms exists, resembling each other in the manner in which the
shell is folded or coiled, but differing in their fundamental
structure. All these different forms may be looked upon as
produced by the modification of a greatly elongated cone, the
structure of which may be in conformity with the type either
of the Nautilida  or of the Ammonitidce.  The following table
(after Woodward) exhibits the representative forms in the two
families:Vzautizlid.     Amm onilidee.
Shell straight..       Orthoceras.       Baculites.,,  bent on itself..   Ascoceras.   Ptychoceras.,, curved                   Cyrtoceras.       Toxoceras.,,  spiral.                Trochoceras.  Turrilites.,,  discoidal.              Gyroceras.       Crioceras.,,  discoidal and produced Lituites...  Ancyloceras.
involute....    Nautilus..  Ammonites.
After the Nautilus itself, the most important form  of the
NVanzuidit  is the Orthoceras (fig. 121).  In structure this was




334               MANUAL OF ZOOLOGY.
doubtless essentially identical with the Nautilus, but the shell,
instead of being coiled into a spiral lying in one plane, was extended in a straight, or nearly straight, line.  Orthoceratites of
more than six feet in length have been discovered, but in all,
the body-chamber, in which the animal was lodged, appears to
have been comparatively small. The siphuncle is usually very
complex in structure, and was calcareous throughout its entire
length.
2
Fig. i2x.-Orthoceras exfilora/or, Billings. I. Side view of a fragment, showving
the septa. 2. Transverse section of the same, showing (s) the siphuncle.
The structure of the shell in the Ammonitidce is exactly that
of the Pearly Nautilus, consisting of an outer porcellanous
and an inner nacreous layer. The body-chamber was rather
elongated than laterally expanded or dilated. The simplest
form of the Ammnonitide is the Baculife, in which the shell is
straight, like that of an Orthoceras, whilst the septa have the
characters of those of an Ammonite, and the siphuncle is external.  In the Thrrilite the structure of the shell is the same,
but it is coiled into a turreted spiral. In the Ammonite itself,
the shell is discoidal and involuted, corresponding (in form) to
the shell of the Nautilus; the body-chamber was of comparatively large size, and had its aperture closed, in some species
at any rate, by an operculum. The shell sometimes attained
a gigantic size, and several hundred species of the genus have
been described. In Crioceras the shell was a flat spiral, like
that of the Ammonites, but the whorls are not in contact. In
Toxoceras the shell is shaped like a bow.  In Ancyloceras the
shell is at first discoidal, with separate whorls, then produced
into a straight line, and finally bent forwards into a hook.
SYNOPSIS OF THE FAMILIES OF THE CEPHALOPODA.
CLASS CEPHALOPODA.
ORDER I. DIBRANCHIATA.
Animal with two branchiae; not more than eight or ten arms,
provided with suckers; an ink-bag; shell commonly internal and
rudimentary; rarely external, but not chambered.
SECTION A. OCTOPODA.
Arms eight, suckers sessile.




MOLLUSCA: CEPHALOPODA.                          335
Fam.- I. Argonautihd.
Female provided with a calcareous, external, m:nothalamous
shell, secreted by the webbed extremities of the dorsal arms.
Gen. Airgonaulta.
Fam. 2. Octoipotidre.
Shell internal, rudimentary, uncalcified.  No pallial fins in
most.  Ill. Gen. Octopus, Th-emoctopus, Eledtone, Pinnoctopus.
SECTION B. DECAPODA.
Arms eig-ht, with two clavate " tentacles;" suckers ledunculated.
Fear. 3.Teut/ids.
Shell an internal horny "pen" or "gladius." Fins mostly
terminal.  Ill. Gen. Loi'g-o, Onychoteuthis, Orlmastrsep/es.
Fam. 4. Belemnitidze.
Shell internal, composed of a conical chambered portion
("phragmacone") with a marginal siphuncle, sometimes produced into a horny plate or " pen," and lodged in a cylindrical
fibrous "guard."  Ill. Gen. Belemnites, Belemnitella, Belem-.niteuthis.
Frnm. 5. Sepiade.
Shell calcareous, consisting of a broad, laminar plate, terminating posteriorly in an imperfectly chambered apex (" phragmacone").  Ill. Gen. Sepia, Beloptera, Spzrulirostra.
Fam. 6. Spirulidae.
Shell internal, nacreous, chambered, discoidal; the whorls
separate; a ventral siphuncle. Gen. Spirula.
ORDER II. TETRABRANCHIATA.
Animal with four gills; arms more than ten, without suckers;
no ink-bag; shell external, chambered, and siphuncled.
Fam. I. Nautilid&.
Sutures of the shell simple; the siphuncle central, sub-central,
or near the concavity of the curved shells, simple.
Sub-family  aauitilidtv proper..
Body-chamber capacious; aperture simple; siphuncle
central or internal.  Ill. Gen. Nautilus, Lituites, T7ochaoceras.
Sub-family O.thoceratidce.
Shell straight, curved, or discoidal; body-chamber
small; aperture contracted; siphuncle complicated.  Ill.
Gen. Orthoceras, Phragimoceras, Cyrtoceras.
Fam. 2. AImmonitlide.
Shell discoidal, curved, spiral, or straight; body-chamber
elongated; aperture guarded by processes, or closed by an operculum; sutures angulated, lobed, or foliaceous; siphuncle external or dorsal (on the convex side of the curved shells). Ill.
Gen. Ammonites, Ceratites, Baculites, Turrilites, Scaphites, AncyloerSu.




336             MANUAL OF ZOOLOGY.
CHAPTER LII.
DISTRIBUTIONX  OF THE  zIOLLUSCA PROPER
IN  TIMIE.
REMAINS of the JMollusca proper are found in greater or less
abundance in almost all the stratified rocks from the commencement of the Silurian period up to the present day.
Speaking generally, the Tetrabranchiate Cep/halopoda are the
chief representatives of the Mol/usca in the Palaeozoic rocks,
the Lamedlibranchiata and the Dibranchiate Cephazoopoda in the
Mesozoic rocks, and the Gasteropoda in the Kainozoic period;
but all the primary classes are represented even in the Lower
Silurian rocks. The folllowing are the more noticeable facts
relating to the distribution of the various classes in past time.
lame//ibranchiata.-The Lamellibranchs are known to have
existed in the Lower Silurian period, and have steadily increased up to the present day, when the class appears to have
attained its maximum, both as regards numbers and as regards
variety of type.  The recent bivalves are also superior in
organisation to those which have preceded them. Upon the
whole the Asiphonate bivalves are more characteristically
Palaeozoic, whilst those in which the mantle-lobes are united,
and there are respiratory siphons, are chiefly found in the
Secondary and Tertiary epochs. One very singular and aberrant family-viz., the Jf1z2jpuritidce-is exclusively confined to
the Secondary rocks, and is, indeed, not known to occur beyond the limits of the Cretaceous formation. The Venerid&e,
which are perhaps the most highly organised of the families of
the Lame/libranczhiata, appear for the first time in the Oolitic
rocks, and, increasing in the Tertiary period, have culminated
in the Recent period.
Gasteropoda.-The Gasteropoda are represented in past time
from the Lower Silurian rocks up to the present day. Of the
Branchifera the -Hoostomata are more abundant in the Palaeozoic period, the Siphonostomata abounding more in the Secondary and Tertiary rocks, but not attaining their maximum
till the present day.  The place of the carnivorous Sipzonostomata in the Paleozoic seas appears to have been filled by
the Tetrabranchiate Cephalopods.  The branchiate Gasteropods of fresh water are chiefly represented as fossils by the
genera Pal/dinla, Valvata, and Ampjullaria.
The Heteroapot/a are likewise of very ancient origin, having
commenced their existence in the lowest Silurian deposits.




MOLLUSCA: DISTRIBUTION.                337
The genera Bellerophon, Porcellia, Cyrtolites, and MAfachirea, are
almost exclusively Palaeozoic; Belleroph/ila is found in the
Gault (Secondary), and Carizaria has been detected in the
Tertiaries.
The Pulmonate Gasteropoda, as was to be anticipated, are
not found abundantly as fossils, occurring chiefly in lacustrine
and estuarine deposits, in which the genera Limnea, Physa,
Ancylus, &c., are amongst those most commonly represented.
These, however, are entirely Mesozoic and Kainozoic. In the
Palaeozoic period the sole known representatives of the Pulmoz~f/era are the Pqupa vetusta and Zonites priscus of the Carboniferous rocks.
Pteropoda.-The Pteropods are not largely represented in
fossiliferous deposits, but they have a wide range in time, extending from the Lower Silurian rocks up to the present day.
The Theca and Conularia of the Palaeozoic period, if truly
Pteropods, are of comparatively gigantic size, and extend from
the Lower Silurian to the Carboniferous period. The Silurian
fossil, i/nlaculites, is asserted by M. Barrande to be a Pteropod, but it is usually looked upon as a tubicolous Annelide.
The recent genus Hyalea is represented in the Tertiary period
(Miocene).
Cephalopoda.-The Cephalopods are largely represented in
all the primary groups of stratified rocks from the Lower Silurian up to the present day.  Of the two orders of Cephalopoda,
the Tetrabranchiata is the oldest, attaining its maximum in the
Palaeozoic period, decreasing in the Mesozoic and Kainozoic
epochs, and being represented at the present day by the single
form Nautilus ponpilius.  Of the sections of this order, the
NautilidZe proper and the Orthoceralidae   are pre-eminently
Palaeozoic, and the Ammonitidel are not only pre-eminently
but are almost exclusively Secondary. Of the abundance of
the two former families in the Silurian seas some idea may be
obtained when it is mentioned that over a thousand species
have been described by M. Barrande from the Silurian basin
of Bohemia alone.   The Nautilidrv proper have gradually
decreased in numbers from the Palaeozoic through the Secondary and Tertiary periods to the present day. The Orlhoceratlidr
died out much sooner, being exclusively Paleozoic, with the
exception of the genera Orthoceras itself and Cyrtoceras, which
survived into the commencement of the Secondary period,
finally dying out in the Trias.
The second far!mlly of the /etrabranc-hiata-viz., the Ammonitide —is almost exclusively Secondary, being very largely
represented by numerous species of the genera Ammonites,




338               MANUAL OF ZOOLOGY.
Ceratites, Baculites, Tlrrilites, &c. The only Palaeozoic genera
are Goniatites and Bactdrites, of which the former is found from
the Upper Silurian to the Trias, whilst the latter is a DevoFig. 122.-Shells of Secondary Cephalopods. I A ncyloceras Matheronianus; 2 Scapihites equalis; 3 Crioceras Divalii; 4 Hamites attenuatus; 5 Tarrilites catenatus.
nian form. The genus Ceratites is characteristically Triassic,
but it is said to occur in the Devonian rocks. All the remaining genera are exclusively Secondary, the genera Baculites,
lfurriites, Hami/es, and Ptychoceras being confined to the Cretaceous period.
Of the Dibranchiate Cephalopoda the record is less perfect,
as they have few structures which are capable of preservation.
They attain their maximum, as fossils, shortly after their first
appearance in the Secondary rocks, where they are represented
by the large and important family of the Beleminidcie. Some
of the Teuthide and SepiadEe are found both in the Secondary
and in the Tertiary rocks, and two species of Argonaut have
been discovered in the later Tertiaries. No example of a
Dibranchiate Cephalopod is known from the Paleozoic deposits, and the order attains its maximum at the present day.




SUBDIVISIONS OF INVERTEBRATA.              339
TABULAR VIEW OF THE CHIEF SUBDIVISIONS
OF THE INVERTEBRATA.
SUB-KINGDOM I.-PROTOZOA.
CLASS I. GREGARINIDIE.
CLASS II. RHIZOPODA.
Order I. Monera.
2. Amcebea.
3. Foraminifera
4. Radiolaria.
5. Spongida.
CLASS III. INFUSORIA.
Order i. Suctoria.
2. Ciliata.
3. Flagellata.
SUB-KINGDOM II.-CCELENTERATA.
CLASS I. HYDROZOA.
Sub-class A. Hydroida.
Order i. Hydrida.
2. Corynida.
3. Sertularida.
4. Campanularida.
Sub-class B. Siphonaophora.
Order 5. Calycophoridae.
6. Physophoridae.
Sub-class C. Discophora.
Order 7. Medusidoe.
Sub-class D. Lucernarida.
Order 8. Lucernariadae.
9. Pelagidae.
Io. Rhizostomidae.
Sub-class E. Graptolitide.
CLASS II. ACTINOZOA.
Order r. Zoantharia.
Sub-order a. Z. Malacodermata.
b. Z. Sclerobasica.
c. Z. Sclerodermata.
Order 2. Alcyonaria.
Fam. a. Alcyonidae.
b. Tubiporidoe.
c. Pennatulidae.
d. Gorgonidx.
Order 3. Rugosa.
Order 4. Ctenophora.
16




340             MANUAL OF ZOOLOGY.
Sub-order a. Stenostomata.
b. Eurystomata.
SUB-KINGDOM III.-ANNULOIDA,
CLASS I. ECHINODERMATA.
Order i. Cystoidea.
2. Blastoidea.
3. Crinoidea.
4. Echinoidea.
5. Asteroidea.
6. Ophiuroidea.
7. Holothuroidea,
CLASS II. SCOLECIDA.
Division A. Platyelmia.
Order I. TLeniada.
2.'rrematoda.
3. Turbellaria.
Sub-order a. Planarida.
b. Nemertida.
Division B. NVematemnia.
Order 4. Acanthocephala.
5. Gordiacea.
6. Nematoda
Division C. Rotifera.
Order. Rotifera.
SUB-KINGDOM IV.-ANNULOSA.
DIVISION A. ANARTHROPODA.
CLASS I. GEPHYREA.
CLASS II. ANNELIDA.
Order I. Hirudinea ) Abranchiata
2. Oligochzeta  A
3. Tubicola    Branchiata.
4. Errantia
CLASS III. CHETOGNATHA.
DIVISION B. ARTHROPODA or ARTICULATA.
CLASS I. CRUSTACEA.
Sub-class I. E2pizoa.
Order I. Ichthyophthira.
2. Rhizocephala.
Sub-class II. Cirripedia.
Balanide.
Order 3. Thoracica.      Verrucid.
Lepadidae.
4. Abdominalia.
5. Apoda.




SUBDIVISIONS OF INVERTEBRATA.             341
Sub-class III. Entomostraca.
Order 6. Copepoda  J Legion Lophyropoda.
8. Cladocera  }
9. Phyllopoda  Legion Branchiopoda.
3o. Trilobita   )
I i. Merostomata.
Sub-order a. Xiphosura.
b. Eurypterida.
Sub-class IV. M2alacostraca.
Order I 2. Loemodipoda     Division A.
i3. isopoda
Amphisopoda       Edriophthalmata.
I5. Stomapoda        Division B
x 6. Decapoda      Podophthalmata.
Tribe a. Macrura.
b. Anomura.
c. Brachyura.
CLASS II. ARACHNIDA.
Division A. Trachearia.
Order I. Podosomata.
2. Acarina.
3. Adelarthrosomnata.
Division B. Pulmonaria.
Order 4. Pedipalpi.
5. Araneida.
CLASS III. MYRIAPODA.
Order I. Chilopoda.
2. Chilognatha.
3. Pauropoda.
CLASS IV. INSECTA.
Sub-class I. Ametabola.
Order i. Anoplura.
2. Mallophaga.
3. Thysanura.
Sub-class II. Hemnimetaboi,
Order 4. Hemiptera.
5. Orthoptera.
6. Neuroptera.
Sub-class III. Holometabola.
Order 7. Aphaniptera.
8. Diptera.




342              MANUAL OF ZOOLOGY,
9. Lepidoptera.
Io. Hymenoptera.
I I. Strepsiptera.
12. Coleoptera.
SUB-KINGDOM V.-MOLLUSCA.
DIVISION A. MOLLUSCOIDA.
Class I. Polyzoa.
Order I. Phylactoloemata.
2. Gymnolaemata.
Class II. iunicata.
Order I. Ascidia branchialia.
2. Ascidia abdominalia.
3. Ascidia larvalia.
Class III. Brachiopoda.
Order I. Articulata.
2. Inarticulata.
DIVISION B. MOLLUSCA PROPER.
Class IV. Lamellibranchiata.
Section a. Asiphonida.
b. Siphonida.
Class V. Gasteropada.
Sub-class I. Branchifera.
Order i. Prosobranchiata.
Section a. Siphonostomata.
b. Holostomata.
Order 2. Opisthobranchiata.
Section a. Tectibranchiata.
b. Nudibranchiata.
Order 3. Nucleobranchiata (Heteropoda)
Fam. a. Firolidoe.
b. Atlantide.
Sub-class II. Pulmonifera.
Section a. Inoperculata.
b. Operculata.
Class VI. Pteropoda.
Order I. Thecosomata.
2. Gymnosomata.
Class VII. Cephalopojda.
Order i. Tetrabranchiata.
2. Dibranchiata.




PART II.
VERTEBRATE ANIMALS








VERTEBRATE ANIMALS.
CHAPTER LTII.
GENERAL CHARACTERS AND DIVISIONS OF THE
VERTEBRATA.
THE five sub-kingdoms which we have previously considered —
viz., the Protozoa, Cawlenter, uta, Annuloida, Annulosa, and Mollusca- were grouped together by the French naturalist Lamarck
to form one great division, which he termed Invertebrata, the
remaining members of the animal kingdom constituting the
division Vertebrata. The division Vertebrata, though including only a single sub-kingdom, is so compact and well-marked
a division, and its distinctive characters are so numerous and
so important, that this mode of looking at the animal kingdom
is, at any rate, a very convenient one.
The sub-kingdom Vertebrata may be shortly defined as comprising animals in which the body is composed of a number of
definite segments, arranged along a longitudinal axis; tile nervous
system is in its mahinmasses dorsal, and the neural and haemal
rerions of the body are always completely shut off from one another by a partition; the limbs are never more than four in
number, and are always turned away from the neu;ral aspect of
the body; mostly there is the bony axis knowlcn as thle " spine" or
" vertebral column," and in all thle strzucture klnown as the " nolochord" is presentz-in the embryo, at any rate.  These characters distinguish the Verlebrata, as a whole, from the Invertcbrata; but it is necessary to define these broad differences
more minutely, and to consider others which are of little less
importance.
One of the most obvious, as it is one of the most fundamental, of the distinctive characters of Vertebrates, is to be
found in the shutting off of the main masses of the nervous




346               MANUAL OF ZOOLOGY.
system  from  the general cavity of the body.  In all linverfebrate animals, without exception, the body (fig. I23, A) may
be regarded as a single tube, enclosing all the viscera; and
consequently, in this case, the nervous system is contained
within the general cavity of the body, and is not in any way
shut off from the alimentary canal. The transverse section,
however, of a Vertebrate animal exhibits two tubes (fig. I 23, B),
one of which contains the great masses of the nervous system
-that is, the cerebro-spinal axis, or brain and spinal cord
-whilst the other contains the alimentary canal and the chief
circulatory organs, together with certain portions of the nervous system, known as the "ganglionic" or "sympathetic"
system. Leaving the cerebro-spinal centres out of sight for a
moment, we see that the larger or visceral tube of a Vertebrate
animal contains the digestive canal, the hlemal system, and a
A                               ~B bB
Fig.  -A, Transverse section of the body of one of the higher 
Fig. 123.-A, Transverse section of the body of one of the higher Inverlebrala; a
Body-wall; b Alimentary canal; c THemal system; n Nervous system. B, Transverse section of the body of a Vertebrate animal: a Body-wall; b Alimentary
canal; c Hxemal system; n Sympathetic system of nerves; i' Cerebro-spinal system
of nerves; ch Notochord.
gangliated nervous system. Now this is exactly what is contained in the visceral cavity of any of the higher Invertebrate
animals; and it follows from this, as pointed out by Von Baer,
that it is the sympathetic nervous system of Vertebrates which
is truly comparable to, and homologous with, the nervous system of Invertebrates. The cerebro-spinal nervous centres of
the Verlebra/a are to be regarded as something superadded,
and not represented at all amongst the Invertebrata.
The tube containing the cerebro-spinal centres is formed as
follows:-At an early period in the development of the embryo of any Vertebrate animal, the portion of the ovum  in
which development is going on-the "germinal area"- becomes elevated into two parallel ridges, one on each side of
the middle line,. enclosing between them a long groove, which
is known as the " primitive groove" (fig. I 24, A, B). The ridges
which bound the primitive groove are known as the " lamino




GENERAL CHARACTERS OF THE VERTEBRATA. 347
dorsales;" and they become more and more raised up, till they
ultimately meet in the middle line, and unite to form a tube,
within which the cerebro-spinal nervous centres are developed.
It follows from its mode of formation that the inner wall of the
tube formed by the primitive groove, which remains as the
septum between the cerebro-spinal canal and the body-cavity,
is nothing more than a portion of the primitive wall of the body
of the embryo. And there appears to be little doubt, as believed by Remak and Huxley, that the cerebro-spinal nervous
centres are " the result of a modification of that serous layer
of the germ, which is continuous elsewhere with the epidermis"
(Huxley).
C       tz
B 
""3                                    D
A
Fig. 124.-Embryology of Vertebrata. A, Portion of the germinal area of the ovum
of a Bitch, showing the primitive groove (after Bischoff). B, Profile view of the
same. C, Diagram representing the amnion and allantois: e Embryo; a Amnion; u Umbilical vesicle; b Allantois; f Pedicle of the allantois, afterwards the
urinary bladder. D, Head of an embryo, showing the visceral arches (v v).
Another remarkable peculiarity as regards the nervous system is found in the fact that in no Vertebrate animal does the
alimentary canal pierce the main masses of the nervous system,
but turns away to open on the opposite side of the body. In
most Invertebrates, on the other hand, in which there is a
well-developed nervous system, this is perforated by the gullet,
so that an cesophageal nerve-collar is formed, and some of the
nervous centres become prze-cesophageal, whilst others are
post-cesophageal.
Furthermore, the floor of the "primitive groove" in the
embryo of all Vertebrates has developed in it at an early
period the structure known as the " notochord" or " chorda
dorsalis" (fig. I23, B, ch). This structure, doubtfully present
mn any Invertebrate, is a semi-gelatinous or cartilaginous col



348              MANUAL OF ZOOLOGY.
lection of cells, forming a rod-like axis, which tapers at both
ends, and extends along the floor of the cerebro-spinal canal,
supporting the cerebro-spinal nervous centres. In some Vertebrates, such as the Lancelet (Amphioxus), the notochord is
persistent throughout life. In the majority of cases, however,
the notochord is replaced before maturity by the structure
known as the "vertebral column" or " backbone," from
which the sub-kingdom Vertebrata originally derived its name.
This is not the place for an anatomical description of the
spinal column, and it is sufficient to state here that it is essentially composed of a series of cartilaginous, or more or less
completely ossified, segments or ver/ebre, arranged so as to form
a longitudinal axis, which protects the great masses of the
nervous system. It is to be remembered, however, that all
Vertebrate animals do not possess a vertebral column. They
all possess a notochord; but this may be persistent, and in
many cases the development of the spinal column is extremely
imperfect.
Another embryonic structure which is characteristic of all
Vertebrates, is found in the so-called "visceral arches" and
" clefts" (fig. I24, D). The " visceral arches" are a series of parallel ridges running transversely to the axis of the body, situated at the sides of, and posterior to, the mouth. As develop-.
mnent proceeds, the intervals between these ridges become
grooved by depressions which gradually deepen, until they
become converted into a series of openings or " clefts," whereby a free communication is established between the upper part
of the alimentary canal (pharynx) and the external medium.
The limbs of Vertebrate animals are always articulated to
the body, and they are always turned away from the neural
aspect of the body. They mray be altogether wanting, or they
may be partially undeveloped; but there are never more than
two pairs, and they always have an internal skeleton for the
attachment of the muscles of the limb.
A specialised blood-vascular or " hmemal" system is present
in all the Vertebrata, and in all except one —the Al4p/hioxusthere is a contractile cavity or heart, which never consists of
less than two chambers provided with valvular apertures. In
all the Vertebrata the heart is essentially a respiralory heartthat is to say, it is concerned with driving the impure or venous
blood to the breathing-organs; and in its simplest form (fishes)
it is nothing more than this. In the higher Vertebrates, however, there is superadded to this a pair of cavities which are
concerned in driving the pure or arterial blood to the body.
In the case of the Mammals, these two circulations are often




GENERAL CtIARACTERS OF THE VERTEBRATA.  349
spoken of as the " lesser " or " pulmonary " circulation, and the
"greater " or " systemic" circulation.
In all Vertebrates there is that peculiar modification of the
venous system which is known as the " hepatic portal system."
That is to say, a portion of the blood which is sent to the alimentary canal, instead of returning to the heart by the ordinary
veins, is carried to the liver by a special vessel-the vena
porft —which ramifies through this organ after the manner of
an artery.
In all Vertebrates, also, is found the peculiar system of vessels known as the " lacteal system."  This is to be regarded
as an appendage of the venous system of blood-vessels, and
consists of a series of vessels which take up the products of
digestion from the alimentary canal, elaborate them, and finally
empty their contents into the veins.
Lastly, the masticatory organs of Vertebrates are modified
portions of the walls of the head, and never " hard productions
of the alimentary mucous membrane or modified limbs" (Huxley), as they are amongst the Invertebrata.
The above are the leading characters of the Vertebrala as a
whole; but before going on to consider the primary divisions
of the sub-kingdom, it may be as well to give a very brief and
general description of the anatomy of the higher and more
typical Vertebrates, commencing with their bony framework or
skeleton.
The skeleton of the Vertebrata may be regarded as consisting
essentially of the bones which go to form the head and trunk
on the one hand (sometimes called the " axial" skeleton), and
of those which form the supports for the limbs (" appendicular"
skeleton) on the other hand.  The bones of the head and
trunk may be looked upon as essentially composed of a series
of bony rings or segments, arranged longitudinally, one behind
the other. Anteriorly these segments are much expanded, and
likewise much modified, to form the bony case which encloses
the brain, and which is termed the craniii;; or skull. Behind
the head the segments enclose a much smaller cavity, which is
called the "neural" or spinal canal, as it encloses the spinal
cord; and they are arranged one behind the other, forming
the vertebral column.  The segments which form the vertebral
column are called "vertebrae," and they have the following
general structure:-Each vertebra (fig. 125, A) consists of a
central piece, which is the fundamental and essential element
of the vertebra, and is known as the " body" or " centrum" (c).
From the upper or posterior surface of the centrum spring two
bony arches (in ni), which are called the " neural arches " or




350                MANUAL OF ZOOLOGY.
"neurapophyses" because they form with the body a canalthe "neural canal"-mwhich encloses the spinal cord.   From
the point where the neural arches meet behind, there is usually
developed a longer or shorter spine, which is termed the " spinous process " or " neural spine" (s). From the neural arches
there are also developed in the typical vertebra two processes
(a a), which are known as the "articular" processes, or " zygapophyses." The vertebra are united to one another partly by
these, but to a greater extent by the bodies or " centra." From
the sides of the vertebral body, at the point of junction with
the neural arches, there proceed two lateral processes (d d),
which are known as the " transverse processes." (In the typical
ar          a
Fig. I25.-A, Lumbar vertebra of a Whale: c Body or centrum; 7n  Neural arches;
s Neural spine; a a Articular processes; dd Transverse processes. B, Diagram of a
thoracic vertebra: c Centrum; e n Neural arches enclosing theneural canal; s
Neural spine; rr Ribs, assisting in the formation of the haemal arch; 1z Costal cartilages; b Sternum, with haemal spine. (After Owen.)
vertebra the transverse processes consist each of two pieces, an
anterior piece or "parapophysis," and a posterior piece or
"diapophysis."   These elements form  the vertebra of the
human anatomist, but the "vertebra" of the transcendental
anatomist is completed by a second arch which is placed be-'
neath the body of the vertebra, and which is called the " hemal" arch, as it includes and protects the main organs of the
circulation. This second arch is often only recognisable with
great difficulty, as its parts are generally much modified, but a
good example may be obtained in the human chest, or in the
caudal vertebra of a bony fish.
The hvemal arch in the case of the human thorax (fig. I25,
B) is formed by the ribs (r r) and the costal cartilages (pAp);




GENERAL CHARACTERS OF THE VERTEBRATA.  351
and is completed in front by the breast-bone or sternum (b),
which in some cases-but not in man-develops a spine (the
hemal spine) which corresponds to the neural spine on the
opposite aspect of the vertebra.
It follows from the above, that the typical vertebra consists
of a central piece or body from which two arches are given off,
one of which protects the great masses of the nervous system,
and is therefore said to be "neural;" whilst the other protects the main organs of the circulation, and is therefore said
to be "hremal."  The correspondence of the typical bony
Fig. 126.-Skeleton of the Beaver (Casaorfiber), showing the different regions of the
vertebral column. c Cervical region;  b Lumbar region; s Sacrum;
Z Caudal region.
segment or vertebra with the doubly tubular structure of the
body in all Vertebrates is thus too obvious to require to be
specially pointed out.
As a general rule, the vertebral column is divisible into a
number of distinct regions, of which the following are recognisable in man and in the higher Vertebrala:-i. A series of
vertebrae which compose the neck, and constitute the "cervical
region" of the spine (fig. 1I26, c).  2. A number of vertebra
which usually carry well-developed ribs, and form  the "dorsal
region" (d).  3. A series of vertebra which form  the region
of the loins, or'"lumbar region" (b).  4. A greater or less
i~~Ep~0




352             MANUAL OF ZOOLOGY.
number of vertebrae which' constitute the "sacral region," and
are usually amalgamated or "anchylosed" together to form a
single bone, the "sacrum" (s).  5. The spinal column is
completed by a variable number of vertebrae which constitute
the "caudal" region, or tail (t).
As regards the skull of the Vertebrata, it has been thought
advisable not to enter into any general details here, partly
because the subject is one which can only be properly discussed in a work specially devoted to Human or Comparative
Anatomy, and partly because there is still much diversity of
opinion as to the exact composition of the skull. There is,
however, a very general concurrence of opinion that the skull
is composed of a number of separate segments, and this is a
point which it is important to remember. By Owen, and by
many other competent authorities, these cranial segments are
looked upon as being nothing more than so many vertebrce,
the neural canals of which are greatly expanded to enclose
the brain, whilst the huemal arches are very greatly modified to
serve different purposes. This view is not accepted by Huxley, but the general fact that the skull is composed of separate
segments appears to be universally admitted. The only portion
of the bony framework of the head which it is absolutely
essential to understand, is the lower jaw or " mandible." The
lower jaw is sometimes wanting, but when present, it consists
in all Vertebra/a of two halves or "rami," which are united to
one another in front, and articulate separately with the skull
behind. In many cases, each half, or "ramus," of the lower
jaw consists of several pieces united to one another by sutures;
but in the Mamnnalia each ramus consists of no more than a
single piece. The two rami are very variously connected with
one another, being sometimes only joined by ligaments and
muscles, sometimes united by cartilage or by bony suture, and
sometimes fused or anchylosed with one another, so as to leave
no evidence of their true composition. The mode by which
each ramus of the lower jaw articulates with the skull also
varies.  In the Afammalia the lower jaw articulates with a
cavity formed on what is known to human anatomists as the
temporal bone; but in Birds and Reptiles the lower jaw
articulates with the skull, not directly, but by the intervention
of a special bone, known as the " quadrate bone " or " os quadratun.
As regards the limbs of Vertebrates, whilst many differences
exist, which will be afterwards noticed, there is a general
agreement in the parts of which they are composed. As a
rule, each pair of limbs is joined to the trunk by means of a




GENERAL CHARACTERS OF THE VERTEBRATA. 353 
series of bones which also correspond to one another in general
structure.  The fore-limbs, often called the " pectoral" limbs,
are united with the trunk by means of a bony arch, which is
called the "pectoral" or "scapular" arch; whilst the hindlimbs are similarly connected with the trunk by means of the
"pelvic arch."  In giving a general description of the parts
which compose the limbs and their supporting arches, it will
be best to take the case of a Mammal, and the departures
from this type will then be readily recognised.
The pectoral or scapular arch consists usually of three
bones, the "scapula" or shoulder-blade, the "coracoid," and
the "clavicle" or collar-bone; but in
the great majority of the Mammals, the
coracoid is anchylosed with the scap-          t~ v
ula, of which it forms a mere process.                   C
The scapulaorshoulder-blade(fig. I 27,s)
is usually placed outside the ribs, and                 s
it forms, either alone or in conjunction
with the other bones of the shouldergirdle, the cavity with which the upper
arm  is articulated.   The  coracoid,
though rarely existing as a distinct bone
in the Mammals, plays a very important
part in other Vertebrates, as we shall
see hereafter.  The clavicles are often     -
wanting, or rudimentary, and they are
the least essential elements of the
scapular arch.  The fore-limb proper
consists, firstly, of a single bone which          d
forms the upper arm, and which is
known as the hunmerus (h).  This arti-,1 
culates above with the shoulder-girdle,
and is -followed below by the fore-arm, y    7
which consists of two bones, called the
radius and uzla.  ()f these the radius
is chiefly concerned with carrying the
hand.  The radius and ulna are fol-  Fig. 227. -Pectoral limb
lowed by the bones of the wrist, which    (arm) of Chimpanzee.
(After Owen.)  c Claviare usually composed of several bones,    clde; s Scapula or shouland constitute what is called the carpus    der-blade; I Hulnerus;
r Radius; u Ulna;
(d).  These support the bones of the    Bones of the wrist, or carpus; m Metacarpus;;
root of the  hand, which  vary  in    Phalanges of the fingers
number, but are always more or less
cylindrical in shape.  They constitute what is called the
mc/acar uis. The bones of the metacarpus carry the digits,




354               MANUAL OF ZOOLOGY.
which also vary in Pumber, but are composed each of from
two to three cylindrical bones, which are known as the
phalanges (p).
Homologous parts are, as a rule, readily recognisable in the
hind-limb.  The pelvic arch, by which the hind-limb is united
with the trunk, consists of three pieces-the
ilium, ischium,  and pubes-which are usually
anchylosed together, and form  conjointly what
is known as the iznnominate bone (fig. 128, i).
In most Mammals, the two innominate bones
unite in front by a ligamentous or cartilaginlous
union, and they constitute, with the sacrum, what
is known as the pelvis.  The hind-limb proper,r.....'~  consists of the following parts: —I. The thigh\~ t!1 bone orfenmur, corresponding with the humerus
in the fore-limb.  2. The bones of the shank,
corresponding with the radius and ulna of the
fore-limb, and known as the tibia and fibula..Of these, the tibia is mainly or altogether concerned in carrying the foot, and it is.thus........t   shown to correspond to the radius, whilst the
fibula corresponds to the ulna.  3. The' small
bones of the ankle, known as the tarsus, and...-..:;   varying in number in different cases.  4. A
variable number of cylindrical bones (normally
five), which are called the metatarsus, and which
correspond to the metacarpus.  5. Lastly, the
metatarsus carries the digits, which consist of
P   from two to three small bones or p/zhahlages, as
Fig. 128.- Pelvic in the fore-limb.
limb (hind - ee)limb The dizestive syslcm of Vertebrates will be
(after Owen) i spoken of at greater length hereafter; but a
Innominate bone;.fFemur,orthigh- brief sketch may be given here of the general
one; / Tibia; s phenomena of digestion.  All Vertebrate aniFibtla; rTarsus;.
roMetatarsus; f mals are provided with a mouth for the retohalanges  of the ception of food, and in the great majority of
cases the mouth is furnished with teeth, which
are used sometimes merely to hold the prey, but more commonly to cut and bruise the food, and thus render it capable
of digestion.   The food is also generally subjected in the
mouth to the action of "salivary" glands, the secretion of
which serves not only to moisten the food, and thus mechanically assist deglutition, but also to render soluble the
starchy elements of the food. The food is next swallowed, or,
in other words, is transferred from  the mouth to the stomach,




GENERAL CHARACTERS OF THE VERTEBRATA.  355
this being effected by a complicated arrangement of muscles,
whereby the food is forced down the gullet (eso/hiagus) to the
proper digestive cavity or stomach. In the stomach (fig. I29, s)
the food is subjected to two sets of actions; it is mechanically
triturated and ground down by the constant contractions of
the muscular walls of the stomach; and it is subjected to the
chemical action of a special fluid secreted by the stomach,
and called the "gastric juice." This fluid has the power of
reducing albuminoid substances to a soluble form, and by its
action the food is ultimately reduced to a thick acid fluid,
called the "chyme."   Leaving  the stomach by its lower
aperture (the pylorus), the chyme passes into the intestine,
the first portion of which is divided into several sections, but
is collectively known as the "small
intestine."  Here the chyme is sub-                 g
jected to the action of three other
digestive fluids; the bile, secreted
by a special organ, the liver; the
pancreatic juice, secreted by another\    s
gland, the pancreas; and the in/estinaljuice, secreted by certain glands
situated in the mucous membrane of 
the intestine itself. The result of the  
whole process is that the "chyme"'A 
is ultimately converted into a white,     si
alkaline, milky fluid, which is called
"chyle."  The indigestible portions
of the food pass from  the small intestine into a tube of larger dimen-                        lnlt
sions, called the "large intestine."
Such portions of the food as are
still soluble, and capable of being
employed  in  nutrition, are  here
taken up into the blood, the use-          r
less remainder being ultimately expelled by an anal aperture.  The
last portion of the large intestine is. 29.-iagran of te digestive.lFig. r29. —ljacrrall of the digestive
usually less convoluted than the rest,  system of a Mammal. g Gullet;
and is called the " rectum."          s Stomach; sin Small intestine;
im Large intestine; r Rectum,
The fluid and originally soluble  terminating in the aperturd of
portions of the food, and the chyle  the anus.
which is formed in the process of digestion, are taken into the
blood, the losses of which they serve to repair.  Part of the
nutritive materials of the food is taken up directly by the
blood-vessels, and is conveyed by the "vena portae" to th -




35j6             MANUAL, OF ZOOLOGY.
liver, whence it ultimately reaches the great veins which go to
the heart. The greater part, however, of the liquefied food,
constituting the chyle, is taken up, not by the blood-vessels,
but by a special set of tubes, which form a network in the
walls of the intestine, and are known as the "lacteals."  In
these vessels, and in certain glands which are developed upon
them, the chyle undergoes still further elaboration, and is made
more similar in composition to the blood itself. All the lacteal
vessels ultimately unite into one or more large vessels which
open into one of the veins, so that all the chyle is thus finally
added to the mass of the circulating blood.
The blood, thenl, or nutrient fluid from which the tissues are
built up, is formed in this way out of the materials which are
taken into the alimentary canal as food. In all the Vertebrata,
with the single exception of the Lancelet (Amnlhioxus), the
blood is of a red colour when viewed in mass. This is due to
e             a                              d c d
Fig. 130.-Blood-corpuscles of Vertebrata. a Red blood-discs of man; b Blooddiscs of Goose; c Crocodile; d Frog; e Skate.
the presence in it of an incredible number of microscopical
bodies, which are known as the "blood-corpuscles," the fluid
in which these float being itself colourless (fig. I30).
In all the Vertebrata the blood is distributed through the
body by means of a system of closed tubes, which constitute
the " blood-vessels; " and in all except the Lancelet, the means
of propulsion are derived from a contractile muscular cavity
or "heart," furnished with valvular apertures.  In the most
complete form of circulation, as seen in Birds and Mammals,
the -heart is essentially a. double organ, composed of two
halves, each of which consists of two cavities, an auricle and
a ventricle. The right side of the heart is wholly concerned
with the "lesser" or pulmonary circulation, whilst the left
side is concerned with driving the blood to all parts of the
body (systemic circulation). The modifications of the circulatory process will be noticed in speaking of the different classes of
Vertebrates, but a brief sketch may be given here of the circulation in its most complete form, as in a Mammal.  In such a
case, the venous or impure blood, which has circulated through
the body and has parted with its oxygen, is returned by the great




GENERAL CHARACTERS OF THE VERTEBRATA. 357
veins-to the right auricle. From the right auricle (fig. I3 i, a) the
blood passes by a valvular aperture into the right ventricle (z),
whence it is driven through the pulmonary artery to the lungs.
The right side of the heart is therefore wholly respiratory in its
function. Having been submitted to
the action of the lungs, and having
given off carbonic acid and taken up
oxygen, the blood now becomes arterial, and is returned by the pulmonary
veins to the left auricle (a').   From    P
the left auricle the aerated blood passes       a
through a valvular aperture' into the
left ventricle (v'), whence it is propelled to all parts of the body by Dt
means of a great systemic vessel, the
" aorta."  The left side of the heart is
therefore wholly occupied in carrying c-    v         v'
out the "greater" or systemic circulation.
The purification of the blood is carried out in all Vertebrates by means
of distinct respiratory organs, assisted
to a greater or less extent by the skin.
In the Fishes, and in the Amphibians
to some extent, the process of respiraFig. I3T.-Diagram of the cirtion is carried on by means of bran-   culation of a Mammal. The
c/hitC  or gills-that is, by organs adapted   venous system is marked
-9~~~ I                   ~~~~~black; the arterial system is
for breathing air dissolved  in water.  left white. a Right auricle;
Right ventricle; K PulmoThese are, therefore, often spoken of   aryartery, carryingyenohls
nary artery, carrying venous
as " Branchiate" Vertebrates; but the   blood to the lungs; pv Pulmonary veins carrying arterial
Amphibians always develop true lungs   blood from the lungs; a' Left
in the later stages of their existence.   auricle; 7' Left ventricle; b
Aorta, carrying arterial blood
In the Reptiles, Birds, and Mammals,  to the body; c Vena cava
carrying venoutis blood to the
branchiae are never developed, and the   heart.
respiration is always carried on by
means of true lungs-that is, by organs adapted for breathing
air directly. These are therefore often spoken of as the " Abranchiate" Vertebrates.
The waste substances of the body-of which the most important are water, carbonic acid, and urea-are got rid of by
the skin, lungs, and kidneys. Under ordinary circumstances,
the lungs are mainly occupied with the excretion of carbonic
acid and watery vapour.  The skin chiefly gets rid of superfluous moisture, but can also in many animals excrete carbonic




358             MANUAL OF ZOOLOGY.
acid as well. The kidneys are present in almost all Vertebrate
animals, and their function is mainly to excrete water, and the
nitrogenous substance known as urea.  In the majority of
cases the fluid excreted by the kidneys is conveyed to the
exterior by means of two tubes known as the ureters, which
empty themselves into a common receptacle, the urinary bladder. In some cases, however, the ureters open into the termination of the alimentary canal (rectum).
The nervous system of Vertebrate animals usually exhibits
a well-marked division into two parts-the cerebro-spinal system, and the sympathetic system. The cerebro-spinal system
of nerves constitutes the great mass of the nervous system of
Vertebrates, and usually exhibits a well-marked separation
into spinal cord (myelonr) and brain (encephalon). The proportion borne by the brain to the spinal cord differs much in different cases; and in the Lancelet a brain can hardly be said
to be present at all.  As already said, the brain and spinal
cord are always completely shut off from the visceral cavity,
and they are placed upon the dorsal surface of the body. The
nerves given off from the cerebro-spinal axis are symmetrically
disposed on the two sides of the body, and they are mainly
concerned with the functions of "animal" life-that is to say,
with sensation and locomotion. The sympathetic system of
nerves is unsymmetrically disposed to a greater or less extent,
and presides mainly over the functions of " organic " or " vegetative" life, being mainly concerned with regulating the functions of digestion and respiration, and the circulation of the
blood. In its most fully developed form it consists of a double
gangliated cord placed in the visceral cavity on the under surface of the spine, and of a series of nervous ganglia, united by
nervous cords, and scattered mainly over the great viscera of
the thorax and abdomen.
The organs of the senses are well developed in the Vertebrata,
and those appropriated to the senses of sigzt, he-iarig, smell,
and taste are protected within bony cavities of the head. The
perfection of the senses differs much in different cases, but they
are probably never wholly wanting in any Vertebrate animal.
Tlhere are cases in which vision must be of the most rudimentary character; but even in these cases it is probable that there
is a perception of light, even if there is no power of distinguishing objects. The only cases in which it would appear that
viion is really altogether absent, are those of animals placed
under the wholly abnormal condition of spending their existence in darkness (such as the Proteus angluinus of the caves of




DIVISIONS OF THE VERTEBRATA.              359
Illyria).  Smell, hearing, and taste are probably rarely, if ever,
altogether absent in Vertebrates; though in many cases their
organs are very rudimentary. Touch, or "tactile sensibility,"
is usually possessed to a greater or less degree by the entire
surface of the body; but the sense of touch is generally localised
in certain particular parts, such as the appendages of the mouth,
the lips, the tongue, or the digits.
In all Vertebrata without exception reproduction is carried
on by means of the sexes, and in all the sexes are in different
individuals. No Vertebrate animal possesses the power of reproducing itself by fission or gemmation; and in no case are
composite organisms or colonies produced. Most of the Vertebrates are oviparous, that is to say, the ova are expelled from
the body of the parent either before or very shortly after impregnation. In other cases, the eggs are retained within the
body of the parent until the young are hatched, and in these
cases the animals are said to be ovo-viviparous. In other cases,
again, not only is the egg hatched within the parent, but the
embryo is retained within the body of the mother until its development has been carried out to a greater or less extent; and
these animals are said to be viviparous.
DIVISIONS OF THE VERTEBRATA.-The sub-kingdom  Vertebrata is divided into the five great classes of the Fishes (Pisces),
Amphibians (Amnphibia), Reptiles (Reptilia), Birds (Aves), and
Mammals (Mammalia). So far there is perfect unanimity; but
when it is inquired into what larger sections the Vertebrata may
be divided, there is much difference of opinion. Here, the
divisions proposed by Professor Huxley will be adopted, but it
is necessary that those employed by other writers should be
mentioned and explained.
One of the commonest methods of -classifying the Verlebrata
is to divide them into the two primary sections of the Branchiala and Abranchiala. Of these, the Branchiate section includes the fishes and Amphibians, and is characterised by the
fact that the animal is always provided at some period of its
life with branchime or gills. The Abranchiate section includes
the Reptiles, Birds, and Mammals, and is characterised by the
fact that the animal is never provided at any time of its life
with gills. Additional characters of the Branchiate Vertebrates
are, that the embryo is not furnished with the structures known
as the amnion and allandois. Hence the Branchiate Vertebrates
are often spoken of as the Anamnzio/a and as the Anallantaidea.
In the Abranchiate Vertebrates, on the other hand, the embryo is always provided with an amnion and allantois, and




360                MANUAL OF ZOOLOGY.
hence this section is spoken of as the Amniota or as the A4lantoidea. *
By Professor Owen the Vertebrata are divided into the two
primary sections of the Hffmatocrya and the Hcematofterma, the
characters of the blood being taken as the distinctive character. The Heematocrya or Cold-blooded Vertebrates comprise the
Fishes, Amphibia, and Reptiles, and are characterised by their
cold blood and imperfect circulation. The Hcematothernma or
Warm-blooded Vertebrates comprise the Birds and the Mammals, and are characterised by their hot blood, four-chambered
heart, and complete separation of the pulmonary and systemic
circulations. The chief objection to this division lies in the
separation which is effected between the Reptiles and the
Birds, two classes which are certainly very nearly allied to one
another.
By Professor Huxley the Vertebralaa are divided into the following three primary sections:I. ICHTHYOPSIDA.-This section comprises the Fishes and
the Amphibians, and is characterised by the presence at some
period of life of gills or branchiae, the absence of an amnion,
the absence or rudimentary condition of the allantois, and the
possession of nucleated red blood-corpuscles.
II. SAUROPSIDA.-This section comprises the Birds and the
Reptiles, and is characterised by the constant absence of gills,
the possession of an amnion and allantois, the articulation of
the skull with the vertebral column by a single occipital condyle; the composition of each ramus of the lower jaw of several
pieces, and the articulation of the lower jaw with the skull by
the intervention of an " os quadratum;" and, lastly, the possession of nucleated red blood-corpuscles.
III. MAMMALIA.-This section includes the single class of
the Mammals, and agrees with the preceding in never possessing gills, and in having an amnion and allantois.  The Mam* The amnion (fig. I24) is a membranous sac, containing a fluidthe liquor amnii-and completely enveloping the embryo. It constitutes one of the so-called "fcetal membranes," and is thrown off at birth.
The allantois (fig. I24, C) is an embryonic structure, which is developed
out of the middle or " vascular" layer of the germinal membrane. It appears at first as a solid, pear-shaped, cellular mass, arising from the under
part of the body of'he embryo. In the process of development, the allantois increases largely in size, and becomes converted into a vesicle which
envelops the embryo in part or wholly. It is abundantly supplied with
blood, and is the organ whereby the blood of the fRetus is aerated. The
part of the allantois which is external to the body of the embryo is cast off
at birth; but the portion which is within the body is retained, and is con.
verted into the urinary bladder.




DIVISIONS OF THE VERTEBRATA.            36I
mafia, however, differ from the Sauropsida in the fact that the
skull articulates with the vertebral column by two occipital
condyles; each ramus of the lower jaw is simple, composed of
a single piece, and the lower jaw is united with the temporal
(squamosal) element of the skull, and is not articulated to a
quadrate bone.  There are special glands —the mammary
glands —for the nourishment of the young for a longer or
shorter period after birth, and the red blood-corpuscles are
non-nucleated.




DIVISION I. ICHTHYOPSIDA.
CHAPTEK LIV.
CLA SS I. PISCES.
THE first class of the Vertebrata is that of the Fishes (Pisces),
which may be broadly defined as including Vertebrate animals
which are provided with gills throughout the whole of life; the
heart, when present, consists (with one exception) of a single auricle
and a singlc ventricle; the blood is cold; the limbs, when present,
are in the form  of fins, or expansions of the integument; and
there is neither an amnion nor allantois in the embryo, unless the
latter is represented by the urinary bladder.
In form, Fishes are adapted for rapid locomotion in water,
the shape of the body being such as to give rise to the least
possible friction in swimming. To
this end also, as well as for purposes
of defence, the body is usually enveloped with a coating of scales
developed in the inferior or dermal
layer of the skin.  The more im_ |  b  n 5    portant modifications in the form
a                          of these dermal scales are as follows: I. Cycloid scales (fig. I32, a),
consisting of thin, flexible, horny.yl      jp \   Xlscales, circular or elliptical in shape,
and having a more or less completely smooth outline.  These are
the scales which are characteristic
C                       of most of the ordinary bony fishes.
II.  Clenoid  scales (fig. 132, b),
a Cycloid scale (Pike); b Ctenloodis. also consisting of thin horny plates,
scale (Perch); c Placoid scale but having their posterior margins
(Thornback); d Ganoid scales (Pa-fringed with  spines, or cut into
&loniscus).               fringed with spines, or cut into
comb-like projections. III. Ganoid
scales, composed of an inferior layer composed of bone, covered
by a superficial layer of hard polished enamel (the so-called




CHARACTERS OF FISHES.                  363
" ganoine "). These scales (fig. I32, d) are usually much larger
and thicker than the ordinary scales, and though they are often
articulated to one another by special processes, they only rarely
overlap.' IV. Slacoid scales, consisting of detached bony grains,
tubercles, or plates, of which the latter are not uncommonly
armed with spines (fig. 132, c).
In most fishes there is also to be observed a line of peculiar
scales, forming what is called the "lateral line." Each of the
scales in this line is perforated by a tube leading down to a
longitudinal canal which runs along the side of the body, and
is connected with cavities in the head.  The function of this
singular system has been ordinarily believed to be that of secreting the mucus with which the surface of the body is covered;
but it seems to be more probably sensory in function, and to
be connected with the sense of touch.
As regards. their true osseous system or endoskeleton, Fishes
vary very widely. In the Lancelet there can hardly be said to
be any skeleton, the spinal cord being simply supported by
the gelatinous notochord, which remains throughout life. In
others the skeleton remains permanently cartilaginous; in
others it is partially cartilaginous and partially ossified; and,
lastly, in most modern fishes it is entirely ossified, or converted
into bone.  Taking a bony fish (fig. I33) as in this respect a
typical example of the class, the following are the chief points
in the osteology of a fish which require notice:The vertebral column in a bony fish consists of vertebrae,
which are hollow at both ends, or biconcave, and are technically said to be "amphiccelous."  The cup-like margins of the
vertebral bodies are united by ligaments, and the cavities
formed between contiguous vertebrae are filled with the gelatinous remains of the notochord.  This elastic gelatinous substance acts as a kind of ball-and-socket joint between the bodies
of the vertebrae, thus giving the whole spine the extreme mobility which is requisite for animals living in a watery medium.
The ossification of the vertebrae is often much more imperfect
than the above, but in no case except that of the Bony Pike
(Lepidosteus) is ossification carried to a greater extent than
this. In this fish, however, the vertebral column is composed
of" opisthoccelous" vertebrae-that is, of vertebrae the bodies of
which are concave behind and convex in front. The entire
spinal column is divisible into not more than two distinct regions, an abdominal and a caudal region.  The abdominal vertebrae possess a superior or neural arch (through which passes
the spinal cord), a superior spinous process (neural spine), and
two transverse processes to which the ribs are usually attached.
17




364                MANUAL OF ZOOLOGY.
The caudal vertebrxe (fig. I33) have no marked transverse processes; but, in addition to the neural arches and spines, they
give off an inferior or lzemal arch below the body of the vertebra, and the haemal arches carry inferior spinous processes
(haelnal spines).
The ribs of a bony fish are attached to the transverse processes, or to the bodies of the abdominal vertebrae, in the form
of slender curved bones which articulate with no more than
one vertebra each, and that only at a single point. Unlike the
ribs of the higher Vertebrates, the ribs do not enclose a thoracic
cavity, but are simply embedded in the muscles which bound
the abdomen. Usually each rib gives off a spine-like bone,
d'
Fig. 133.-Skeleton of the common Perch (Percafluviatilis). fi One of the pectoral
fins; v One of the ventral fins; a Anal fin, supported upon interspinous bones (i); c
Caudal fin; d First dorsal fin; d' Second dorsal fin, both supported upon interspinous
bones; ii Interspinous bones; rRibs; s Spinous processes of vertebrae; h Haemal
processes of vertebrae.
which is directed backwards amongst the muscles. Inferiorly
the extremities of the ribs are free, or are rarely united to dermal ossifications in the middle line of the abdomen; but there
is never any breast-bone or sternum  properly so called.
The only remaining bones connected with the skeleton of
the trunk are the so-called int/erspinzois bones (fig. I33, ii).
These form a series of dagger-shaped bones plunged in the
middle line of the body between the great lateral muscles
which make up the greater part of the body of a fish. The
internal ends or points of the interspinous bones are attached
by ligament to the spinous  processes of the vertebrae; whilst
to their outer ends are articulated the "rays" of the so called
"median" fins, which will be hereafter described.  As a rule,
there is only one interspinous bone to each spinous process,
but in the Flat-fishes (Sole, Turbot, &c.) there are two.




CHARACTERS OF FISHES.                       365
Beside the fins which represent the limbs (pectoral and
ventral fins), fishes possess other fins placed in the middle line
of the body, and all of these alike are supported by bony spines
or "rays," which are of two kinds, termed respectively " spinous rays " and " soft rays."  The "spinous rays " are simple
bony spines, apparently composed of a single piece each, but
really consisting of two halves firmly united along the middle
line. The " soft rays " are composed of several slender spines
proceeding from a common base, and all divided transversely
into numerous short pieces. The soft rays occur in many fishes
in different fins, but they are invariably found in the caudal
fin or tail (fig. I33, c).  The rays of the median fins, whatever
7                                                   in\
Fig. I34.-Skull of Cod (Morrhuae vuzlgaris)-Cuvier. a Urohyal; b Basihyal; c
Ceratohyal; d Branchiostegal rays; f prxe-operculum; o Operculum proper; s Suboperculum; i Inter-operculum; mn Mandible; n Inter-maxillary bone.
their character may be, always articulate by a hinge-joint with
the heads of the interspinous bones.
The skull of the bony fishes is an extremely complicated
structure, and it is impossible to enter into its composition
here. The only portions of the skull which require special
mention are the bones which form the gill-cover or operculum,
and the hyoid bone with its appondages.  For reasons connected with the respiratory process in fishes, as will be after



366             MANUAL OF ZOOLOGY.
wards seen, there generally exists between the head and the
scapular arch a great cavity or gap on each side, within which
are contained the branchixe. The cavity thus formed opens
externally on each side of the neck by a single vertical fissure
or "gill-slit," closed by a broad flap, called the "gill-cover "
or "operculum," and by a membrane termed the "branchiostegal membrane."
The gill-cover (fig. I34, p, a, s, i) is composed of a chain of
broad flat bones, termed the opercular bones. Of these, the
innermost articulates with the skull (tympano-mandibular arch),
and is called the "prxe-operculum;" the next is a large bone
called the "operculum" proper; and the remaining two bones
called respectively the "sub-operculum" and "inter-operculum,"
form, with the operculum proper,'the edge of the gill-cover.
These various bones are united together by membrane, and
they form collectively a kind of movable door, by means of
which the branchial chamber can be alternately opened and
shut. Besides the gill-cover, however, the branchial chamber
is closed by a membrane called the "branchiostegal membrane," which is attached to the os hyoides.. The membrane
is supported and spread out by a number of slender curved
spines, which are attached to the lateral branches of the hyoid
bone, act very much as the ribs of an umbrella, and are known
as the "branchiostegal rays" (fig. 134, d).
The hyoid arch of fishes is attached to the temporal bones
of the skull by means of two slender styliform bones, which
correspond to the styloid processes of man, and are called the
" stylohyal " bones (fig. x35, f). The rest of the hyoid arch is
composed of a central portion and two lateral branches. Each
branch is composed of the following parts: —I. A triangular
bone attached above to the stylohyal, and termed the "epihyal
bone" (fig. I35, e); 2. A much longer bone, known as the
"ceratohyal" (d). The central portion of the hyoid arch is
made up of two small polyhedral bones-the "basihyais" (b).
From the basihyal there extends forwards in many fishes a
slender bone, which supports the tongue, and is termed the
"glossohyal" or "lingual" bone (a). There is also another
compressed bone, which extends backwards fromn the basihyals,
and which is known as the "urohyal bone" (c). This lastmentioned bone is of importance, as it often extends backwards to the point of union of the coracoid bones, and thus
forms the isthmus which separates the two branchial apertures.
From the outer margins of the epihyal and ceratohyal bones
on each side arise the slender curved "branchiostegal rays,"
which have been previously mentioned. There are usually




CHARACTERS OF FISHES.                     367
seven of these on each side. Above the urohyal, and attached
in front of the body of the os hyoides, is a chain of bones,
placed one behind the other, and termed by Owen the "basi.
branchial bones." Springing from these are four bony arches
-the  "branchial arches "-which proceed upwards to be connected superiorly by ligament with the under surface of the
skull.   The branchial arches-as will be subsequently described-carry the branchiae, and each is composed of two'~'<'
Fig. I35.-Os hyoides, branchiostegal rays, and scapular arch of the Perch (after
Cuvier). ss Supra-scapula; s Scapula, co Coracoid; cl Supposed representative of
the clavicle; a Glossohyal bone; b Basihyal; c Urohyal; d Ceratohyal; e Epihyal;
f Stylohyal; br Branchial arches; t Branchiostegal rays.
main pieces, termed respectively the "cerato-branchial" and
" epi-branchial" bones.  The second and third arches are connected with the skull by the intervention of two small bones,
often called the " superior pharyngeal bones," but termed by
Owen the "pharyngo-branchial" bones.
The liabs of fishes depart considerably from the typical form
exhibited in the higher Vertebrates.  One or both pairs of
limbs may be wanting, but when present the limbs are always




368                 MANUAL OF ZOOLOGY.
in the form of fins-that is, of expansions of the integument
strengthened by bony or cartilaginous fin-rays.  The anterior
limbs are known as the pectoral fins, and the posterior as the
ventral fins; and they are at once distinguished from the socalled "median" fins by being always symmetrically disposed
in pairs. Hence they are often spoken of as the paired fins.
The scapular arch (figs. I35, 136) supporting the pectoral
S — 
r~             A
fi
r,\ 
Fig. 36-Pectoral limbs of Fishes (after   co
Fig. 136.-Pectoral limbs of Fishes (after Owen). A, Cod (Marrhua vzelgaris); B,
Angler (Lophius). ss Supra-scapula; s Scapula; co Coracoid; r Radius; u Ulna;
cc Carpal bones; f Fin-rays, representing the metacarpus and phalanges of the
fingers.
limbs is usually joined to the skull (occipital bone), and consists of the following pieces on each side:-r. The suprascapula (ss); 2. The scapula (s), articulating with the former;
and, 3. The coracoid (co), attached above with the scapula, and
united below, by ligament or suture, with the coracoid of the
opposite side, thus completing the pectoral arch. Lastly, there




CHARACTERS OF FISHES.                    369
is often another bone, sometimes single, but oftener of two
pieces, attached to the upper end of the coracoid, and this is
believed to represent the collar-bone or clavicle."
The fore-limb possesses in a modified form  most of the
bones which are present in the higher Vertebrata.  The zhumerus, or bone of the upper arm, is usually wanting, or it is altogether rudimentary. A radius and ulna (fig. I36, r, u) are
usually present, and are followed by a variable number of
bones, which represent the carpus, and some of which sometimes articulate directly with the coracoid. The carpus is followed by the " rays" of the fin proper, these representing the
metacarpal bones and phalanges. The pectoral fins vary much
in size and in other characters.  In the Flying Gurnard (Dactylopterus), and the true Flying Fish (Exocetus), the pectorals
are enormously developed, and enable the fish to take extensive leaps out of the water.
The hind-limbs or " ventral fins " are wanting in many fishes,
and they are less developed and less fixed in position than are
the pectoral fins. In the ventral fins no representatives of the
tarsus, tibia and fibula,; or femur, are ever developed. The
rays of the ventral fins-representing the metatarsus and the
phalanges of the toes-unite directly with a pelvic arch, which
is composed of two sub-triangular bones, united in the middle
line and believed to represent the ischia. The imperfect pelvic
arch, thus constituted, is never united to the vertebral column
in any fish. In those fishes in which the ventral fins are
"abdominal" in position (i.e., placed near the hinder end of
the body) the pelvic arch is suspended freely amongst the
muscles.  In those in which the ventral fins are " thoracic" or
"jugular" (i.e., placed beneath the pectoral fins, or on the
sides of the neck), the pelvic arch is attached to the coracoid
bones of the scapular arch, and is therefore wholly removed
from its proper vei tebra.
In addition to the pectoral and ventral fins-the homologues
of the limbs-which may be wanting, fishes are furnished
with certain other expansions of the integument, which are
"median" in position, and must on no account be confounded
with the true " paired " fins. These median fins are variable
in number, and in some cases there is but a single fringe
running round the posterior extremity of the body.  In all
cases, however, the median fins are " azygous "-that is to say,
they occupy the middle line of the body, and are not sym* These are the views entertained by Owen as to the composition and
nature of the pectoral arch of fishes, but they are dissented fi-rom by Mr
Parker, one of the greatest living authorities on this subject.




370                MAN UAL OF ZOOLOGY.
metrically disposed in pairs. Most commonly, the median
fins consist of one or two expansions of the dorsal integument,
called the "dorsal fins" (fig. i37, d d'); one or two on the
ventral surface near the anus-the "anal fins" (fig. 137, a); and
d
Fig. 137.-Outline of a fish (Perca graniulata), showing the paired and unpaired fills.
P One of the pectoral fins; v One of the ventral fins; d First dorsal fin; d' Second
dorsal fin; a Anal fEn; c Caudal fin.
a broad fin at the extremity of the vertebral column, called the
"caudal fin" or tail (c).  In all cases, the rays which support
the median fins are articulated with the so-called interspinous
bones, which have been previously described. Though called
"median," from their position in
the middle line of the body, and
from their being unpaired, the
median fins of Fishes, as shown
by  Goodsir and Humphrey, are
truly to be regarded as formed by
the coalescence of two lateral elements in the mesial plane of the
body.
The caudal fin or tail of fishes
is always set vertically at the extremity of the spine, so as to work
from side to side, and it is the
chief organ of progression in the
fishes. In its vertical position, and
in the possession of fin-rays, it
Fig. I38. —Tails of different fishes. differs altogether from  the horia Homocercal tail (Sword - fish); zontal integumentary  expansion
which constitutes the tail of the
WMhales, Dolphins, and Sirenia (Dugong and Manatee). In
the form of the tail fishes exhibit two very distinct types of




CHARACTERS OF FISHES.                 371
structure, termed respectively the " homocercal" and " heterocercal" type of tail (fig. 138).  The homocercal tail is the one
which most commonly occurs in our modern fishes, and it is
characterised by the fact that the two lobes of the tail are
equal, and the vertebral column, instead of being prolonged
into the upper lobe of the tail, stops short at its base.  In
the heterocercal tail, on the other hand, the vertebral column
is prolonged into the upper lobe of the tail, so that the tail
becomes unequally lobed, its greater portion being placed
below the spine. Even where the vertebral column is not prolonged into the upper lobe, the tail may nevertheless become
heterocercal, in consequence of a great development of the
hxemal spines as compared with the neural spines of the
vertebrae.
The process of respiration in all fishes is essentially aquatic,
and is carried on by means of branchial plates or tufts developed upon the posterior visceral arches, which are persistent,
and do not disappear at the close of embryonic life, as they do
in other Vertebrates. In the Lancelet alone, respiration is
effected partly by branchial filaments placed round the commencement of the pharynx, and partly by the pharynx itself.
which is greatly enlarged, and has its walls perforated by a
series of transverse ciliated fissures.  The arrangement and
structure of the branchie differ a good deal in the different
orders of Fishes, and these modifications will be noticed subsequently.  In the meanwhile it will be sufficient to give a
brief description of the branchial apparatus in one of the bony
fishes. In such a fish, the branchime are connected with the
hyoid arch, and are situated in two special chambers, situated
one on each side of the neck. The branchiae are carried
upon the outer convex sides of what have been already described
as the "branchial arches;" that is to say, upon a series of bony
arches which are connected with the hyoid arch inferiorly, and
are united above with the base of the skull. The internal
concave sides of the branchial arches are usually furnished
with a series of processes, constituting a kind of fringe, the
function of whidh is to prevent foreign substances finding their
way amongst the branchioe, and thus interfering with the proper
action of the respiratory organs. The branchie, themselves,
usually have the form of a double series of cartilaginous leaflets
or laminme. The branchial laminae are flat, elongated, and
pointed in shape, and they are covered with a highly vascular
mucous membrane, in which the branchial capillaries ramify.
The blood circulates through the branchial lamini, and is here
subjected to the action of terated water, whereby it is oxygen



372                MANUAL OF ZOOLOGY.
ated. The water is constantly taken in at the mouth by a
movement analogous to swallowing, and it gains admission to
the branchial chambers by means of a series of clefts or slits,
the " branchial fissures," which are situated on both sides of the
pharynx.   Having passed over the gills, the deoxygenated
water makes its escape posteriorly by an aperture called the
"gill-slit " or " opercular aperture," one of which is situated on
each side of the neck. As we have seen before, the gill-slit is
closed in front by a chain of flat bones, collectively constituting the "gill-cover" or "operculum;" and the gill-covers
are finally completed by a variable number of bony spinesthe "-branchiostegal rays"-which articulate with the hyoid
arch, and support a membrane-the
"branchiostegal membrane."
The heart of Fishes is, properly
speaking, a branchial or respiratory
l x   heart.  It consists of two cavities,
1'  n     jI   b   an auricle and a ventricle (fig. I39,
a, v), and the course of the circulation
is as follows:  The venous blood deI    (  3 m  rived from the liver and from the body
generally is poured by the vena cava
— l           V' —I —-~'v  into the auricle (a), and from this it is
propelled into the ventricle (v). From
Z \;/ a  the ventricle arises a single aortic
arch (the right), and the base of this is
usually dilated into a cavity or sinus,
called the "bulbus arteriosus" (m).
The arterial bulb is sometimes covered
with a special coat of striated muscular
fibres, and is provided with several
transverse rows of valves.  In these
cases, the bulbus acts as a kind of
continuation of the ventricle, being
capable of rhythmical contractions.
The blood is driven by the ventricle
Fig. 139. —Diagram of the cir-  through the branchial artery (n) to
culation in a fish. a Auricle,  the  gills, through  which  it is disreceiving venous blood from  tributed  means of the brachia
the body; v Ventricle; m   tributed by means of the branchial
Bulbus arteriosus, at the base  vessels, the number of which varies
of the branchial artery; n 
Branchial artery, carrying the  (there. are three on each side in a few
venous blood to the gills (b' );  fishes, four in most of the'ony fishes,
c Aorta, carrying the arterialised blood to all parts of the  fibe in the Skates and Sharks, and six or
body.                    seven in the Lampreys).  The aerated
blood which has passed through the gills is not returned to the




CHARACTERS OF FISHES.                  373
heart, but is driven from the branchime through all parts of
the body; the propulsive force necessary for this being derived
chiefly from the heart, assisted by the contractions of the voluntary muscles. In some fishes (as in the Eel) the return of the
blood to the heart is assisted by a rhythmically contractile
dilatation of the caudal vein. The essential peculiarity, then,
of the circulation of fishes depends upon this-that the arterialised blood returned from the gills is propelled through the
systemic vessels of the body, without being sent back to the
heart.
The Lancelet (Amjhioxus), alone of all Fishes, has no
special heart, and the circulation is effected by contractile
dilatations developed upon several of the blood-vessels. In
the Mud-fish (Lepidosiren) the heart consists of two auricles
and a single ventricle. The blood-corpuscles of Fishes are
nucleated (fig. I30, e), and the blood is red in all except the
AmpZioxlUs.
As regards the dtigestive system of Fishes there is not much of
peculiar importance. The mouth is usually furnished with a
complicated series of teeth, which, in the Bony Fishes, are not
only developed upon the jaws proper, but are also situated
upon other bones which enter into the composition of the
buccal cavity (such as the palate, the pterygoids, vomer,
branchial arches, the glossohyal bone, &c.) The cesophagus
is usually short and capacious, and generally opens into a large
and well-marked stomach. The pyloric aperture of the stomach
is usually furnished with a valve, and behind it there is usually
a number (from one to sixty) of blind appendages, termed the
" pyloric cxeca." These are believed to represent the pancreas,
but there may be a recognisable pancreas either alone or in
addition to the pyloric cxeca. The intestinal canal is a longer
or shorter, more or less convoluted tube, the absorbing surface
of which, in certain fishes, is largely increased by a spiral
reduplicature of the mucous membrane, which winds like a
screw in close turns from the pylorus to the anus. The liver
is usually large, soft, and oily, and a gall-bladder is almost
universally present; but in the Anp/hioxus the liver is doubtfully represented by a hollow sac-like organ.
The kidneys of fishes are usually of great size, and form two
elongated organs, which are situated beneath the spine, and
extend along the whole length of the abdominal cavity.  The
ureters often dilate, and form a species of bladder, the doubtful
representative of the allantois.
Whilst the respiration of all fishes is truly aquatic, most of
them are, nevertheless, furnished with an organ which is




374              MANUAL OF ZOOLOGY.
doubtless the homologue of the lungs of the air-breathing
Vertebrates.  This-the "air" or "swim bladder"-is a sac
containing gas, situated beneath the alimentary tube, and
often communicating with the gullet by a duct. In the great
majority of fishes the functions of the air-bladder are certainly
hydrostatic-that is to say, it serves to maintain the necessary
accordance between the specific gravity of the fish and that of
the surrounding water. In the singular Mud-fishes, however,
it acts as a respiratory organ, and is therefore not only the
homologue, but also the analogue, of the lungs of the higher
Vertebrates. In most fishes the air-bladder is an elongated
sac with a single cavity, but in many cases it is variously subdivided by septa. In the Mud-fish the air-bladder is composed
of two sacs, completely separate from one another, and divided
into a number of cellular compartments. The duct leading in
many fishes from the air-bladder (ductus pneuimaticus) opens
into the cesophagus, and is the homologue of the wind-pipe
(trachea). The air contained in the swim-bladder is composed
mainly of nitrogen in most fresh-water fishes, but in the seafishes it is mainly made up of oxygen. The fishes which live
habitually at the bottom of the sea, such as the Flat-fishes,
possess no swim-bladder, and it is much reduced in size in
those which live principally at the surface.
The nervous system of fishes is of an inferior type of organisation, the brain being of small size, and consisting mainly of
ganglia devoted to the special senses. As regards the special
senses, there is one peculiarity which deserves special notice,
and this is the conformation of the nasal sacs. The cavity of
the nose is usually double, and is lined by an olfactory membrane, folded so as to form numerous plicae. Anteriorly, the
water is admitted into the nasal sacs by a single or double
nostril, usually by two apertures; but posteriorly the nasal
sacs are closed, and do not communicate with the pharynx
by any aperture. The only exceptions to this statement are
to be found in the Myxinoids and in the Lepidosiren. The
essential portion of the organ of hearing (labyrinth) is present
in almost all fishes, but in none is there any direct communication between the ear and the external medium. In some
cases, however, there is a communication between the ear and
the swim-bladder, thus foreshadowing the Eustachian tube in
man.
As regards their reproductive system, fishes are, for the most
part, truly oviparous, the ovaries being familiarly known as the
" roe."  The testes of the male are commonly called the " soft
roe " or " milt."  The products of the reproductive -organs are




CHARACTERS OF FISHES.             375
often set free into the peritoneal cavity, ultimately finding their
way to the external medium, either by means of an abdominal
pore (or pores), or by being taken up by the open mouths of
the "Fallopian tubes." In other cases the generative products are directly conveyed to the exterior by the proper ducts
of the reproductive organs.




DIVISIONS OF FISHES.
CHAPTER LV.
PHAZR YNGOBRA NCHII AND MA iRSIPOBRA NCIII.
THE class Pisces has been very variously subdivided by different writers; but the classification here adopted is the one
proposed by Professor Huxley, who divides the class into the
following six orders, in the subdivisions of which Professoi
Owen has been followed:-*
ORDER I. PHARYNGOBRANCHII (= Cirrostonzi, Owen; and
Leptocardia, Miiller).-This order includes but a single fish,
the anomalous Amp/hioxus lanceolatus, or Lancelet (fig. 140),
the organisation of which differs in almost all important points
from that of all the other members of the class. The order is
defined by the following characters, which, as will be seen, are
mostly negative:-No skull is present, nor lower jaw (mandible),
nor limbs.  The notochord is persistent; and there are no
vertebral centra nor arches. No distinct brain nor auditory
organs are present. In place of a distinct heart, pulsating dilatations are developed upon several of the great blood-vessels.
The blood is pale. The mouth is in the form of a longitudinal
fissure, surrounded by filaments or cirri. The walls of the
pharynx are perforated by numerous clefts or fissures, the
sides of which are ciliated, the whole exercising a respiratory
function.
The Lancelet is a singular little fish which is found burrowing in sandbanks, in various seas, but especially in the Mediterranean. The body is lanceolate in shape, and is provided
with a narrow membranous border, of the nature of a median
fin, which runs along the whole of the dorsal and part of the
* Cuvier divided the class Pisces into the great orders of the Czaondopterygii (or Cartilaginous Fishes), the Acanthopteiygii (or Fishes with spinous
rays in the paired fins), and Malacoptelygii (or Fishes with soft rays
in the paired fins).  Agassiz divides Fishes, from the character of the
scales, into the four orders, Cycloidei, Ctenoidei, Ganzoidei, and PYacoidci.
MiUller divides the Fishes into the five orders Ieptocardia (Lancelet), Cyclostomata (Lampreys and Hag-fishes), Teleostei (Bony Fishes), Ganbidei (Ganoid
Fishes), and Selachia (Sharks and Rays).




PHARYNGOBRAN CHII.                       377
ventral surface, and expands at the tail to form a lancet-shaped
caudal fin. No true paired fins, representing the anterior and
posterior limbs, are present.  The mouth is a longitudinal
fissure, situated at the front of the head, and destitute of
jaws. It is surrounded by a cartilaginous ring, composed of
many pieces, which give off prolongations, so as to form a
number of cartilaginous filaments or "cirri" on each side of
the mouth.   (Hence the name of Cirrostorni, proposed by
Professor Owen for the order.) The throat is provided on
each side with vascular lamellae, which are believed by Owen
to perform the function of free branchial filaments. The mouth
leads into a dilated chamber, which is believed to represent the
pharynx, and is termed the "pharyngeal" or "branchial sac."
It is an elongated chamber, the walls of which are strengthened
by numerous cartilaginous filaments, between which is a series
n               A~h
int
Fig. 140.-Diagram of the Lancelet (A lShAioxus). m Mouth, surrounded by cartilaginous cirri; fi Greatly-dilated pharynx, perforated by ciliated clefts; i Intestine,
terminating in anus (a); h Haemal system, with pulsating dilatations; chi Notochord;
n Spinial cord.
of transverse slits or clefts, the whole covered by a richly ciliated mucous membrane. This branchial dilatation has given
rise to the name BraUzc/iostorma, often applied to the Lancelet.
Posteriorly the branchial sac opens into an alimentary canal, to
which is appended a long and capacious sac or caecum, which
is believed to represent the liver. The intestinal tube terminates posteriorly by a distinct anus.  Respiration is effected
by the admission of water taken in by the mouth into the
branchial sac, having previously passed over the free branchial
filaments before mentioned. The water passes through the slits
in the branchial sac, and thus gains access to the abdominal
cavity, from which it escapes by means of an aperture with
contractile margins situated a little in front of the anus, and
called the "abdominal pore."  There is no distinct heart, and
the circulation is entirely effected by means of several rhythmically contractile dilatations which are developed upon several




378              MANUAL OF ZOOLOGY.
of the great blood-vessels. The blood itself is colourless.  No
kidneys have as yet been discovered, and there is no lymphatic
system. There is no skeleton properly so called. In place of
the vertebral column, and constituting the whole endoskeleton,
is, the semi-gelatinous cellular notochord, enclosed in a fibrous
sheath, and giving off fibrous arches above and below. The
notochord is, further, peculiar in this, that it is prolonged quite
to the anterior end of the body, whereas in all other Vertebrates
it stops short at the pituitary fossa. There is no cranium, and
the spinal cord does not expand anteriorly to form a distinct
cerebral mass. The brain, however, may be said to be represented, since the anterior portion of the nervous axis gives off
nerves to a pair of-rudimentary eyes, and another branch to a
ciliated pit, believed to represent an olfactory organ.  The
generative organs (ovaria and testes) are not furnished with
any efferent ducts (oviduct or vas deferens). The generative
products, therefore, must be admitted into the abdominal
cavity, and gain the external medium by the "abdominal
* pore."
ORDER II. MARSIPOBRANCHII (= Cyclostoma, Owen; and
Cyclostonata, Miiller). -  This order includes the Lampreys
(Petromyzonidace) and the Hag-fishes (Myxinidce), and is defined
by the following characters: —The body is cylindrical, wormlike, and destitute of limbs. The skull is cartilaginous, without cranial bones, and having no lower jaw (mandible). The
notochord is persistent, and there are either no vertebral centra,
or but the most rudimentary traces of them. The heart consists
of one auricle and one ventricle, but the branchial artery is not
furnished with a bulbus arteriosus. The gills are sac-like, and
are not ciliated.
The type of piscine organisation displayed in the Marsiyobravlchii is of a very low grade, as indicated chiefly by the
persistent notochord without vertebral centra, the absence of
any traces of limbs, the absence of a mandible, and the structure of the gills.
Both the Lampreys (fig. 14I, A) and the Hag-fishes are vermiform, eel-like fishes, which agree in possessing no paired
fins, to represent the limbs, but in having a median fin running
round the hinder extremity of the body.  The skeleton remains throughout life in a cartilaginous condition, the chorda
dorsalis is persistent, and the only traces of bodies of vertebre
are found in hardly perceptible rings of osseous mattei de
veloped in the sheath of the notochord. Tlie neural arches of
the vertebrae, enclosing the spinal cord, are only represented
by cartilaginous prolongations.  The mouth in the Hag-fish




MARSIPOBRANCHII.                         379
(A~yxine) is of a very remarkable character, and enables it to
lead a very peculiar mode of life. It is usually found, namely,
embedded in the interior of some other large fish, into which
d.Fig. r4I.-A, Lamprey (Petrontyzon), showing the suckirfg-mouth and the apertures
of the gill-sacs. B, Diagram to illustrate the structure 6f the gills in the Lamprey:
a Pharynx; b Tube leading from the pharynx into one of the gill-sacs; c One of the
gill-sacs, showing the lining membrane thrown into folds; d External opening of the
gill-sac. (In reality the gill-sacs do not open directly into the pharynx, but into a
comlmon respiratory tube, which is omitted for the sake of clearness.
it has succeeded in penetrating by means of its singular dental
apparatus. The mouth is sucker-like, destitute of jaws, but
provided with tactile filaments or cirri.  In the centre of the
palate is fixed a single, large, recurved fang, which is firmly
attached to the under surface of the cranium.   The sides of
this fang are strongly serrated, and it is by means of this that
the Hag-fish bores its way into its victim, having previously
attached itself by its stucker-like mouth. In the Lampreys the
mouth has also the form of a circular cup or sucker, and is
also destitute of jaws; but in addition to the palatine fang of
the Myxine, the margins of the lips bear a number of horny
processes, which are not really true teeth, but are hard structures developed in the labial mucous membrane. The tongue,
also, is armed with serrated teeth, and acts as a kind of piston;
so that the Lampreys are in this manner enabled to attach
themselves firmly to solid objects.
A very remarkable peculiarity in the Hag-fishes, and one
very necessary to remember, is foufid in the structure of the
nasal sacs. In all fishes, namely, except these and the Mudfishes (iLepidosiren), the nasal sacs are closed behind, and do
not open posteriorly into the throat. In the Myxinoids, however, such a communication exists, and the nasal sac-for
there is only one-is placed in communication with the cavity
of the mouth by means of a canal which perforates the palate.
In front the nasal cavity communicates with the external medium by a second tube, which opens on the top of the head
by a single aperture, which is often called the "spiracle," and




380              MANUAL OF ZOOLOGY.
which is in reality an unpaired nostril. In the Lampreys, on
the other hand, the single nasal sac has the same structure as
in the typical fishes-that is to say, it is closed behind, and
does not communicate in any way with the cavity of the mouth.
Another very remarkable point in the Hag-fishes and Lampreys is to be found in the structure of the gills, from which
the name of the order is derived.  In the Lampreys, in place
of the single gill-slit, covered by a gill-cover, as seen in the
ordinary bony fishes, the side of the neck, when viewed externally, exhibits six or seven round holes placed far back in a
line on each side (fig. I41, A). In the Hag fishes the external
apertures of the gills are reduced to one on each side, placed
below the head; but the internal structure of the gills is the
same in both cases. In both the Lampreys and the Hag-fishes,
namely, the gills are in the form of sacs or pouches (fig. I41, B),
the mucous membrane of' which is thrown into folds or plaits
like the leaves of a book, over which the branchial vessels
ramify. Internally'the sacs communicate with the cavity of
the pharnyx, either directly or by the intervention of a common
respiratory tube. It follows from this, that the gill-pouches on
the two sides, with their included fixed branchial laminae, communicate freely with one another through the pharynx. The
object of this arrangement appears to be mainly that of obviating the necessity of admitting water to the gills through the
mouth, as is the case with the ordinary bony fishes. These
fishes are in the habit of fixing themselves to foreign objects
by means of the suctorial mouth; and when in this position, it
is, of course, impossible that they can obtain the necessary
water of respiration through the mouth.  As the branchial
pouches, however, on the two sides of the neck, communicate
freely with one another through the pharynx, water can readily
pass in and out. This, in the Lampreys, is further assisted
by a kind of elastic cartilaginous framework upon which the
respiratory apparatus is supported, and which acts somewhat
like the ribs of the higher Vertebrala.  Water can also be
admitted to the pharynx,'and thence to the branchial sacs, by
means of a tube which leads from the pharynx to an aperture
placed on the top of the head.
The Lampreys are, some of them, inhabitants of rivers; but
the great Sea-lamprey (Petroinyzon marinus) only quits the
salt water in order to spawn. The mouth in the Pctlromlyzonidce is a circular cartilaginous ring, formed by the amalgamation of the palatine and mandibular arches, and carrying
numerous teeth and small tubercles.  The tongue is armed
with a double series of small teeth, and acts like a piston,




TELEOSTEI.                     381
enabling the animal to attach itself to stones and rocks. There
is no air-bladder. The body is cylindrical, compressed towards
the tail, and destitute of scales.  The skeleton consists of a
series of cartilaginous rings without ribs.
In the Afyxiiziide the mouth is circular, membranous, with
eight cirrhi.  The palate carries a single fang, and the tongue
is armed with a double row of small teeth on each side. There
may be seven branchial apertures on each side (leplatrenna),
or the branchial pouches open into a common tube on each
side, and each of these terminates in a distinct aperture situated
under the heart on the lower surface of the body (Gastrobranchus).  The Hags pour out so much mucus through the
lateral line that they can surround themselves with jelly; hence
the name of the common species (Myxine glutiosa).  The
Glutinous Hag is a native of the North and British seas, and
is chiefly found in the interior of the Cod and Haddock (often
five or six individuals in one fish).
CHAPTER LVI.
TELEOSTEI.
ORDER III. TELEOSTEI.-This order includes the great majority of fishes in which there is a well-ossified endoskeleton,
and it corresponds very nearly with Cuvier's division of the
"osseous " fishes. The Teleostei are defined as follows:-The
skeleton is usually well ossified; the cranium is provided with
cranial bones; and a mandible is present; whilst the vertebral
column almost always consists of more or less completely ossi-fied vertebrae. The pectoral arch has a clavicle; and the two
pairs of limbs, when present, are in the form of fins supported
by rays. The gills are free, pectinated or tufted in shape; a
bony gill-cover and branchiostegal rays being always developed. - The branchial artery has its base developed into a bulbus arteriosus; but this is never rhythmically contractile, and
is separated from the ventricle by no more than a single row
of valves.
The order YTheoslei comprises almost all the common fishes;
and it will be unnecessary to dilate upon their structure, as
they were taken as the types of the class in giving a general
description of the Fishes. It may be as well, however, to recapitulate very briefly some of the leading characters of the order.




382             MANUAL OF ZOOLOGY.
I. The skeleton, instead of remaining throughout life more
or less completely cartilaginous, is now always more or less
thoroughly ossified. The notochord is not persistent, and the
vertebral column, though sometimes cartilaginous, consists of a
number of vertebrae. The bodies of the vertebrae are what is
called "amphiccelous "-that is to say, they are concave at
both ends. It follows from this, that between each pair of
vertebrae there is formed a doubly-conical cavity, and this is
filled with the cartilaginous or semi-gelatinous remains of the
notochord. By this means an extraordinary amount of flexibility is given to the entire vertebral column. In no fish except
the Bony Pike (which belongs to the order Ganoidei) is the
ossification of the vertebral centra carried further than this.
The skull is of an extremely complicated nature, being composed of a number of distinct cranial bones; and a mandible
or lower jaw is invariably present.
II. The anterior and posterior pairs of limbs are usually, but
not always, present, and when developed they are always in
the form of fins. The fins may be supported by " spinous " or
"soft" rays, of which the former are simple undivided spines
of bone, whilst the latter are divided transversely into a number of short transverse pieces, and also are broken up into a
number of longitudinal rays proceeding from a common
root.  (The Fishes with soft rays in their paired fins are
termed "Mazlacopterygi " —those with spinous rays, "Acanthopterygii.")
III. Besides the paired fins, representing the limbs, there is
a variable number of unpaired or azygous integumentary expansions, which are known as the "median fins." When fully
developed (fig. 137), they consist of one or two fins on the
back-the "dorsal" fins; one or two on the ventral surfacethe "anal" fins; and one clothing the posterior extremity of
the body —the "caudal" fin. The caudal fin is set vertically,
and not horizontally, as in the Whales and Dolphins, and in all
the bony fishes its form is " homocercal " —that is, it consists of
two equal lobes, and the vertebral column is not prolonged
into the superior lobe.  In all the median fins the fin-rays are
supported upon a series of dagger-shaped bones, which are
pllnged inf the flesh of the middle line of the body, and are
attached to the spinous processes of the vertebrae. These are
the so-called "interspinous" bones.
IV. The heart consists of two chambers, an auricle and a
ventricle, and the branchial artery is furnished with a bulbus
arteriosus. The arterial bulb, however, is not furnished with a
special coat of striated muscular fibres, is not rhythmically con



TELEOSTEI.                        383
tractile, and is separated from the ventricle by no more than a
single row of valves (fig. I42, A).
b                                      /
V..  UC —Fig. I42.-A, Heart of the Angler (Lophius fiscatorzus). B, Arterial bulb of Bony
Pike (LeySidosteus) cut open. C, Heart of the same, viewed externally; a Auricle;
v Ventricle; b Arterial bulb.
V. The respiratory organs consist of free, pectinated, or tufted
branchiae, situated in two branchial chambers, each of which
communicates internally with the pharynx by a series of clefts,
and opens externally on the side of the neck by a single aperture (or "gill-slit "), which is protected in front by a bony gillcover, and is also closed by a " branchiostegal membrane," supported upon " branchiostegal rays." The branchime are attached
to a series of bony branchial arches, which are connected inferiorly with the hyoid bone and superiorly with the skull; and
the water required in respiration is taken in at the mouth by a
process analogous to swallowing.
VI. The nasal sacs never communicate posteriorly with the
cavity of the pharynx.
The subdivisions of the osseous fishes are so numerous, and
they contain so many families, that it will be sufficient to run
over the more important sub-orders, and to mention the more
familiar examples of each.
SUB-ORDER A. MALACOPTERI, Owen (- P/ysostomata, Miiller).-This sub-order is defined by usually possessing a complete set of fins, supported by rays, all of which are " soft" or
many-jointed, with the occasional exception of the first rays in
the dorsal and pectoral fins. A swim-bladder is always present,
and always communicates with the oesophagus by means of a
duct, which is the homologue of the windpipe. The skin. is
rarely naked, and is mostly furnished with cycloid scales; but
in some cases ganoid plates are present.
This sub-order is one'of great importance, as comprising




384              MANUAL OF ZOOLOGY.
many well-known and useful fishes. It is divided into two
groups, according as ventral fins are present or not.  In the
first group-Apoda-there are no ventral fins; and the most
familiar examples are the common Eels of our own country.
The Eels (Muracnidev) have an elongated, almost cylindrical,
body, with the scales deeply sunk in the skin, and scarcely apparent. A swim-bladder is generally present, and the operculum
is small and mostly enveloped in the skin. More remarkable,
however, than the ordinary Eels is the Gymnotus electricius
or great Electric Eel. which inhabits the marshy waters
of those wonderful South American plains, the so-called
"Llanos."  This extraordinary fish (fig. 143) is from five to
Fig. I43. —Electric Eel (Gymwotlus electricus).
six feet in length, and the discharge of its electrical organs
is sufficiently powerful to kill even large animals.  The following striking account is given by Humboldt of the manner
in which the Gymnoti are captured by the Indians.:-" A
nlumber of horses and mules are driven into a swamp which is
closely surrounded by Indians, until the unusual disturbance
excites the daring fish to venture an attack.  Serpent-like,
they are seen swimming along the surface of the water, striving
cunningly to glide under the bellies of the horses. By the
force of their invisible blows numbers of the poor animals are
suddenly prostrated; others, snorting and panting, their manes
erect, their eyes wildly flashing terror, rush madly from the
raging storm; but the Indians, armed with long bamboo staves,
drive them back into the midst of the pool.
" By degrees the fury of this unequal contest begins to
slacken. Like clouds which have discharged their electricity,
the.wearied eels disperse. They require long rest and nourishing food, to repair the galvanic force which they have so
lavishly expended.  Their shocks gradually become weaker
and weaker. Terrified by the noise of the trampling horses,




TELEOSTEI.                    385
they timidly approach the banks of the morass, where they are
wounded by harpoons, and drawn on shore by non-conducting
pieces of dry wood.
" Such is the remarkable contest between horses and fish.
That which constitutes the invisible but living weapon of these
inhabitants of the water's-that which, awakened by the contact of moist and dissimilar particles, circulates through all the
organs of animals and plants —that which, flashing amid the
roar of thunder, illuminates the wide canopy of heaven-which
binds iron to iron, and directs the silent recurring course of
the magnetic needle-all, like the refracted lays of light, flow
from one common source, and all blend together into one
eternal all-pervading power."
The second group of the Malacopteri is that of the Abdomninalia, in which there are ventral fins, and these are.abdominal
in position. Space will not permit of more here than merely
mentioning that in this section are contained amongst others
the well-known and important groups of the Cluqpeidce (Herring
Tribe), the Pikes (Esocidct), the Carps, Barbels, Roach, Chub,
Minnow, &c. (CypriniZte), and the Salmonidam, comprising the
various species of Salmon and Trout. Also belonging to this
group are the Sheat-fishes (Silurida),-which are chiefly noticeable
because they are amongst the small number of living fishes possessed of structures of the same nature as the fossil spines known
as "ichthyodorulites."  The structure in question consists of
the first ray of the pectoral fins, which is largely developed, and
constitutes a formidable spine, which the animal can erect and
depress at pleasure.  Unlike the old "ichthyodorulites," however, the spines of the Siluride have their bases modified
for articulation with another bone, and they are not simply
hollow and implanted in the flesh. The " Siluroids" are also
remarkable for their resemblance to certain of the extinct
ganoid fishes (e.g., Pterichthys, Coccosteus, &c.), caused by the
fact that the head is protected with an exoskeleton of dermal
bones. The largest European species is the Silurus glanis of
the Swiss lakes, and of various European rivers. Another
remarkable member of this family is the Malapteerurus of the
Nile and west coast of Africa, which is endowed with electrical
powers.
SUB - ORDER B. ANACANTHINI. — This sub-order is distinguished by the fact that the fins are entirely supported by
" soft" rays, and never possess "spiny" rays; whilst the ventral fins are either wanting, or, if present, are placed under the
throat, beneath or in advance of the pectorals, and supported
by the pectoral arch. The swim-bladder may be wanting, but




386              MANUAL OF ZOOLOGY.
when present it does not communicate with the oesophagus by
a duct.
As in the preceding order, the Anacanthini are divided into
two groups, distinguished by the presence or absence of the
ventral fins. In the first of these groups (Aj5oda) are only a
few fishes, of which one of the most familiar examples is the
little Sand-eel (Ammnodytes lancea), which occurs on all our
coasts. In the second group (Sub-brachiata) in which ventral
fins exist, are the two important families of the Gadidxe and
Pleuronectide.  The Gadidle or Cod family, comprising the
Haddock, Whiting, Ling, and Cod itself, is of great value to
man, most of its members being largely consumed as food. In
the Pleuronectide or Flat-fishes are comprised the Sole, Plaice,
Turbot, Halibut, Brill, and others, in all of which there is a
very curious modification in the form of the body. The body,
namely, in all the Flat-fishes (fig. 144) is very much compressed
Fig. I44.-Pleuronectidae. Rhombuspunctatus. Natural size (after Gosse).
from side to side, and is bordered by long dorsal and anal fins.
The bones of the head are twisted in such a manner that the
two eyes are both brought to one side of the body, which is
sometimes the right side, sometimes the left. The fish usually
keeps this side uppermost, and is dark-coloured on this aspect;
whilst the opposite side, on which it rests, is white. From this
habit of the Flat-fishes of resting upon one flat surface, the
sides are often looked upon as the dorsal and ventral surfaces
of the body. This, however, is erroneous, as they are shown
by the position of the paired fins to be truly the lateral surfaces
of the body.  The mouth has its two sides unequal, the pectorals are rarely of the same size, the ventrals look like a continuation of the anal fin, and the branchiostegal rays are six in
number.




TELEOSTEI.                       387
SUB-ORDER C. ACANTHOPTERI.-This sub)-order is characterised by the fact that one or more of the first rays in the
fins are in the form of true, unjointed, inflexible, " spiny" rays.
The exoskeleton consists, as a rule, of ctenoid scales. The
ventral fins are generally beneath or in advance of the pectorals,
and the duct of the swim-bladder is invariably obliterated.
This sub-order comprises two families:a. The Pharyngoglnathi, in which the inferior pharyngeal
bones are anchylosed so as to form a single bone, which is
usually armed with teeth. The family is not of much importance, the only familiar fishes belonging to it being the " Wrasses"
(CycloZabridce).
b. The Acantlopteri veri, characterised by having always
spiny rays in the first dorsal fin, and usually in the first rays of
the other fins, whilst the inferior pharyngeal bones are never
anchylosed into a single mass. This family includes many
subordinate groups, and may be regarded as, on the whole,
the most typical division of the Teleostean fishes. It will not
be necessary, however, to do more than mention as amongst
the more important fishes contained in it, the Perch family
(Percidee), the Mullets (lfzigilide), the Mackerel family (Sconzberid&), the Gurnards (Scderogeni9de), the Gobies (GobiiZae), the
Blennies (Blenniirde), and the Anglers (Lophiidce).  The Percidze form by far the most important member of this group, and
are distinguished by having ctenoid scales, the operculum and
pra-operculum variously armed with spines, teeth on the vomer
and palate as well as on the jaws, and the branchiostegal rays
from five to seven in number.
SUB-ORDER D. PLECTOGNATHI.-This sub-order is chlaracterised by the fact that the maxillary and premaxillary bones
Fig. I45.-Ostraciontidae. Horned Trunk-fish (Ostracion cornzuhs).
are immovably connected on each side of the jaw. The endoskeleton is only partially ossified, and the vertebral column
often remains permanently cartilaginous. The exoskeleton is
18




388             MANUAL OF ZOOLOGY.
in the form of ganoid plates, scales, or spines. The ventral
fins are generally wanting, and the air-bladder is destitute of a
duct.
The most remarkable fishes of this section are the Trunkfishes (Ostraciontidze, fig. 145), in which the body is entirely
enclosed, with the exception of the tail, in an immovable case,
composed of large ganoid plates, firmly united to one another
at their edges.
Besides the Trunk-fishes, this section also includes the Filefishes (BaZisli&e) and the Globe-fishes (Gymnodontidce).
SUB-ORDER E. LOPHOBRANCHII.-This is a small and unimportant group, mainly characterised by the peculiar structure of
the gills, which are arranged in little tufts upon the branchial
arches, instead of the comb-like plates of the typical bony fishes.
The endoskeleton is only partially converted into bone, and the
exoskeleton, by way of compensation, consists of ganoid plates.
The swim-bladder is destitute of an air-duct.
The singular Sea-horses (zip5pocavzpidce), now kept in most of
our large aquaria, belong to this sub-order, but the only point
about them which requires notice is the curious fact that the
males in this family are provided with a sort of marsupial pouch,
into which the eggs are placed by the female, and to which the
young, when hatched, can retire if threatened by any danger.
This singular cavity is only found in the males, and is situated
at the base of the tail. More familiar than the Sea-horses are
the Pipe-fishes (Syngnathidze), of which one species occurs commonly on our shores.
CHAPTER LVIL.
GA NOIDEI.
ORDER IV. GANOIDEI.-The fourth order of fishes is the
large and important one of the Ganoid fishes, represented, it
is true, by few living forms, but having an enormous development in past geological epochs. For this reason the study of
the Ganoid fishes is one which claims considerable attention.
The order Ganoidei may be defined by the following characters:-The endoskeleton is only partially ossified, the vertebral column mostly remaining cartilaginous throughout life,
especially amongst the extinct forms of the Palaeozoic period,
in which the notochord is persistent. The skull is furnished




GANOIDEI.                       389
with distinct cranial bones, and the lower jaw is present. The
exoskeleton is in the form of ganoid scales, plates, or spines.
There are usually two pairs of limbs, in the form of fins, each
supported by fin-rays. The first rays of the fins are mostly in
the form of strong spines. The pectoral arch has a clavicle, and
the posterior limbs (ventral fins) are placed close to the anus.
The caudal fin is mostly unsymmetrical or " heterocercal." The
swim-bladder is always present, is often cellular, and is provided
with an air-duct. The intestine is often furnished with a spiral
valve. The gills and opercular apparatus are essentially the
same as in the Bony fishes.  The heart has one auricle and a
ventricle, and the base of the branchial artery is dilated into a
bulbus arteriosus, which is rhythmically contractile, is furnished
with a distinct coat of striated muscular fibres, and is provided
with several transverse rows of valves.
Of these characters, the ones which it is most important to
remember are the following:I. The endoskeleton is rarely thoroughly ossified, but varies a
good deal as to the extent to which ossification is carried. In
some forms, including most of the older members of the order,
the chorda dorsalis is persistent, no vertebral centra are developed, and the skull is cartilaginous, and is protected by
ganoid plates. Even in these forms, however, the peripheral
elements of the vertebrae are ossified.  In others, the bodies of
the vertebrae are marked out by osseous or semi-cartilaginous
rings, enclosing the primitive matter of the notochord. In
others, the vertebrae are like those of the Bony fishes-that is
to say, deeply biconcave or "amphiccelous." In one Ganoid,
however-the Bony Pike (Lepidosteus)-the vertebral column
consists of a series of "opisthoccelous" vertebrae,-that is to
say, vertebrae which are convex in front and concave behind.
This is the highest point of development reached in the spinal
column of any fish, and its structure is more Reptilian than
Piscine.
II. The exoskelelon consists in all Ganoid fishes of scales,
plates, or spines, which are said to possess ganioid characters.
The peculiarities of these scales are that they are composed of
two distinct layers-an inferior layer of bone and a superficial
covering of a kind of enamel, somewhat similar to the enamel
of the teeth, called "ganoine." In form the ganoid scales
most generally exhibit themselves as rhomboidal plates, placed
edge to edge, without overlapping, in oblique rows, the plates
of each row being often articulated to those of the next by distinct processes (fig. 132, d).  In other cases the ganoid structures are simply in the form of detached plates, tubercles, or




390              MANUAL OF ZOOLOGY.
spines; and in some cases their shape is even undistinguishable
from the horny scales of the typical Teleostean fishes. In all
cases, however, whatever their form may be, they have the distinctive ganoid structure, being composed of an inferior layer
of true bone and a superior layer of enamel. It is to be remembered, however, that these ganoid plates and scales are
not confined to the fishes of the order Ganoidei, but that they
occur in two sub-orders of the Bony fishes-namely, the Plectognathi and Lophobranchii-and in some others of the /eicostew
as well.
III. As to thefins, both pectorals and ventrals are usually present, and the ventrals are always placed far back in the neighbourhood of the anus, and are never situated in the immediate vicinity
of the pectorals. In some living and many extinct forms the finrays of the paired fins are arranged so as to form a fringe round
a central lobe (fig. I46). This structure characterises a division
of Ganoids called by Huxley, for this reason, Crossopte;ygidce, or
"fringe-finned."  The form of the caudal fin varies, the Ganoids
being in this respect intermediate between the Bony fishes, in
which the tail is "homocercal," and the Sharks and Rays, in
which there is a "heterocercal" caudal fin. In the majority
of Ganoids, then, the tail is unsymmetrical or "heterocercal,"
but it is sometimes equi-lobed or "homocercal."
IV. As to the structure of the respiratory organs, the Ganoid
fishes agree essentially with the Bony fishes. They all possess
free pectinated gills attached to branchial arches, and enclosed
in a branchial chamber, which is protected by an operculum,
and is closed by a branchiostegal membrane, usually supported
by branchiostegal rays.  Besides the ordinary branchia there
is frequently an additional gill, called the "opercular branchia,"
attached to the interior of each operculum, and below this
a false gill or "pseudo-branlchia,' which receives arterialised
blood only.
V. There is always a swim-bladder, which is often divided
by partitions into several cells, and is always connected with
the gullet by an air-duct, as in the Malacopterous division of
the Teleostean fishes.
VI. As to the structure of the heart, the Ganoids differ from
the Bony fishes, and agree with the Sharks and Rays in having
a rhythmically contractile bulbus arteriosus, which is furnished
with a special coat of striated muscular fibres, and is separated
from the ventricle by several rows of valves (fig. I42, B, C).
This is a decided advance in structure, as in this way the arterial bulb is enabled to act as a continuation of the ventricle.
VII. The intestine is often furnished with a spiral redupli



GANOIDE.                          391
cation of its mucous membrane, forming a spiral valve, such as
we shall afterwards see in the Sharks and Roys.
The order of the Ganoid fishes is divided by Owen into the
two divisions of the Iepidoganoidei and the P1acoganoidei. The
best-known living fishes belonging to the Lepidoganoids are the
Bony Pike and the Polypterus.  The Bony Pike (LepidZosteus)
inhabits the rivers and lakes of North America, and attains a
length of several feet. The body is entirely clothed with an
armour of ganoid scales, arranged in obliquely transverse rows.
The vertebral column is exceedingly well ossified, and is reptilian in its characters, the bodies of the vertebrae being " opisthoccelous." The jaws form a long narrow snout, armed with
a double series of teeth; and the tail is heterocercal.
d
d
B             c                             a
Fig. I46.-Ganoid Fishes. A, Polylterus; B, Osteolefiis (extinct), a One of the pectoral fins, showing the fin-rays arranged round a central lobe; b One of the ventral
fins; c Anal fin; d Dorsal fin; d' Second dorsal iin.
The Polypteri, of which several species are known, inhabit
the Nile, Senegal, and other African rivers, and are. remarkable
for the peculiar structure of the dorsal fin (fig. I46, A), which
is broken up into a number of separate portions, each composed
of a single spine in front, with a soft fin attached to it behind.
Two species of Polyptlres have recently been stated to possess
external branchiae when young, losing them when fully grown.
This observation, if confirmed, will bring the Ganoids into a
nearer relationship with the Mud-fishes (Lepimiosiren). Another
group of Lepidoganoids is formed by the Trout-like Amiae of
the fresh waters of the United States.
The section Placoganoidei i:ncludes the largest and best known




392             MANUAL OF ZOOLOGY.
of all the living Ganoid fishes-namely, the Sturgeons —and it
also contains some highly singular fossil forms. The sub-order
is defined by the fact that the skeleton is always imperfectly
ossified, and often retains the notochord, whilst the head and
more or less of the body are protected by large ganoid plates,
which in many cases are united together at their edges by
sutures. The tail is heterocercal.
The family Sturionidce comprises the various species of Sturgeon, which are found in the North, Black, and Caspian seas,
whence they ascend the great rivers for the purpose of spawning. Other allied forms are peculiar to the North American
continent (e.g., the Paddle-fish, Spatularia).  The vertebral
column in the Sturgeon remains permanently in an embryonic
condition. The notochord is persistent, and the vertebral
centra are wanting, but the neural arches of the vertebrae reach
the condition of cartilage.  The mouth is destitute of teeth,
and the head is covered with an armour of large ganoid plates
joined together at their edges by suture. Rows of detached
ganoid plates also occur on the body. The various species of
Sturgeon attain a great size, one-the Beluga-often measuring twelve or fifteen feet in length. They are commercially of
considerable importance, the swimming-bladder yielding most
of the isinglass of commerce, whilst the roe is largely employed
as a delicacy under the name of caviare.
Two or three fossil forms belonging to the SturionidZc  are all
that are at present known; and by far the greater number of
extinct Placoganoids belong to the family Ostracostei, established by Owen, and characterised by the fact that the head,
and generally the anterior part of the trunk as well, was encased
in a strong armour composed of numerous large ganoid plates,
immovably joined to one another.  The posterior cxtremity of
the body was more or less completely unprotected, and, whilst
the notochord was persistent, the peripheral elements of the
vertebrae-namely, the neural and huemal spines-were ossified.
The following are the more remarkable forms belonging to this
section:a. Pteric/zthys.-This is one of the most singular of fossil
fishes, and was first discovered in the Old Red Sandstone by
the late Hugh Miller.  The whole of the head and the anterior
part of the trunk were defended by a buckler of large ganoid
plates, those covering the trunk forming a back-plate and a
breast-plate, articulated together at the sides.
The rest of the body was covered with small ganoid scales
(fig. 148). A small dorsal fin, a pair of ventrals, a pair of pectorals, and a heterocercal tail-fin were present. The form of




GANOIDEI.                        393
the pectoral fins is the peculiar characteristic of the Pterichthys.
These were in the form of two long curved spines, something
like wings, covered by finely-tuberculated ganoid plates. From
their form, they cannot have been of much use in swimming;
but they probably, as suggested by Owen, enabled the fish to
shuffle along the sandy bottom of the sea, if left dry at low
water.
b. Pteraspis.-In most respects this genus was not unlike
Pleric/lhys, but it did not possess the peculiar pectoral fins of
the latter. One species of Pteraspis has been found in the
Upper Silurian Rocks (Ludlow), and is as yet one of the earliest
known indications of the appearance of the great sub-kingdom
Vertebrata upon the globe.
c. Cephalaspis (fig. 147).  This, again, is not unlike Pfer-ii —
thlys in many respects.  The cephalic buckler, howiv,-,., Ilas
Fig. I47.-Cepihalasfps Lyellii.
its posterior angles produced backwards, so as to give it the
shape of a " saddler's knife," whilst the pectoral limbs have not
the form of spines.
d. Coccosteus (fig. 148). — This is another characteristic
Fig. 148.-1. Coccosteus deciZielns; 2. Pterichthys Miller.
genus of the Old Red Sandstone. In this genus, as in the
preceding, there is a cephalic buckler, the plates of which ate




394              MANUAL OF ZOOLOGY.
covered with small hemispherical tubercles. The notochord
was persistent, but the neural and haemal spines, and the rays
of the dorsal and ventral fins, are well ossified. A large heterocercal tail-fin was doubtless present as well.
CHAPTER LVIII.
ELASMOBR1ANICHII ANVD DIPNOI.
ORDER V. ELASMOBRANCHII ( = Selaczin, Miuller; PlacaiLei,
Agassiz; Holocep/zali and Plagios/onzi, Owen).-This order includes the Sharks, Rays, and Chimr'erc, and corresponds with
the greater and most typical portion of the Choizdroptl)c:pidze or
Cartilaginous fishes of Cuvier.  The order is distinguished by
the following characters: —The skull and lower jaw are well
developed, but there are no cranial bones, and the skull consists of a single cartilaginous box, without any indication of
sutures. The vertebral column is sometimes composed of distinct vertebrxe, sometimes cartilaginous or sub-notochordal. The
exoskeleton is in the form of placoid granules, tubercles, or
spines. There are two pairs of fins, representing the limbs,
and supported by cartilaginous fin-rays; and the ventral fins
are placed far back near the anus.  The pectoral arch has no
clavicle. The heart consists of a single auricle and ventricle,
and the bulbus arteriosus is rhythmically contractile, is provided with a special coat of striated muscular fibres, and is
furnished with several transverse rows of valves.  The gills are
pouch-like.
In most of the above characters it will be seen at once that
the Elasmobranchii agree with the Ganoid fishes, especially as
regards the structure of the heart.  The following points of
difference, however, require more special notice:I. The exoskeleton is what is called by Agassiz "placoid."
It consists, namely, of no continuous covering of scales or
ganoid plates, but of more or less numerous detached grains,
tubercles, or spines, composed of bony matter, and scattered
here and there in the integument. In the case of the Rays,
these placoid ossifications often take a very singular shape,
consisting (fig. I32, c) of an osseous or cartilaginous disc, from
the upper surface of which springs a sharp recurved spine,
composed of dentine.
II. The gills are fixed and pouch-like, and differ very mate



ELASMOBRANCHII.                        395
rially from those of the Bony and Ganoid fishes.  In the case
of the Sharks and Rays, the structure of the gills is as follows:
-The branchial arches are fixed, and the branchial laminae
are not only attached by their bases to the branchial arches,
but are also fixed by the whole of one margin to a series of
partitions, which divide the branchial chamber into a number
of distinct pouches (fig. I49).  Each partition, therefore, carries a series of branchial laminae attached to each- side like
the leaves of a book.   By means of these septa a series of
branchial sacs or pouches are formed, each of which opens
internally into the pharynx by a separate slit, and communicates externally with the water by a separate aperture placed
on the side of the neck (fig. 149, B). The arrangement of the
gills being such, there is, of course, no gill-cover, and no branchiostegal membrane or rays.  In one section of the order,
however-viz., the  folocep/,a'i-z though the internal structure
of the gills is the same as the above, there is only a single
branchial aperture or gill-slit externally, and this is protected
by a rudimentary operculum and branchiostegal rays.
o     oN
o
i     zi s       s
Fig. 149 -A, Head of Piked Dog-fish (Shinax), showing the transverse mouth on
the under surface of the head, and the apertures of the gill-pouches. B, Diagram
of the structure of the gill-pouches: o o External apertures; i i Apertures leading
into the pharynx; s s Gill-sacs, containing the fixed gills.
III. Another character in the Elasmobranchii, shared, however, by many of the Ganoids, is the structure of the intestinal
canal. The intestine is extremely short; but, to compensate
for this, there is a peculiar folding of the mucous membrane,
constituting what is known as the " spiral valve." The mucous
membrane, namely, from the pylorus to the anal aperture, is
folded into a spiral reduplication, which winds in close coils
round the intestine, like the turns of a screw. By this means
the absorptive surface of the intestine is enormously increased,
and its shortness is thus compensated for.
The order Elasmobranchii is divided into two sub-ordersthe  froloch/zal4i, characterised by the mouth being terminal in
position, and there being only a single gill-slit; and the Plagiostomi, in -which the mouth is transverse, and placed on the




396'MANUAL OF ZOOLOGY.
under surface of the head (fig. I49, A), and there are several
branchial apertures on each side of the neck.
SUB-ORDER A. HOLOCEPHALI-This sub-order includes cer.
tain curious fishes, of which the only living forms are the
Chimaeridv.  The notochord  is persistent; but the neural
arches and transverse processes are cartilaginous.  The jaws
are bony, and are covered by broad plates representing the
teeth.  The exoskeleton consists of placoid granules.  The
first ray of the anterior dorsal fin is in the form of a powerful
defensive spine, like the "ichthyodorulites" of many fossil
fishes. The ventral fins are abdominal, and the tail is heterocercal. There is only a single external gill-aperture, covered
with a gill-cover and branchiostegal membrane; but only a
small portion of the borders of the branchial laminoe is free.
The mouth is placed at the extremity of the head.
The best-known living representative of the sub-order is the
Chiizeera imonsl/-osa (fig. i5o, B), commonly known as the
Fig. 50. —Plagiostomi and Holocephali. A, White Shark (Carcharias);
B, C/h/lazrra mzonstrosa. (After Gosse.)
"king of the Herrings."  In Chincera there is only one apparent gill-slit, but the gills really adhere to the integument by




ELASMOBRAN CIII.                   397
a large portion of their borders, and there are consequently
five holes communicating with the gill-slit.  A  rudimentary
operculum is present, covered by the skin.  In the closelyallied Callorhynchus from the South Seas, there is a large fleshy
appendage at the end of the snout. In the Secondary and
Tertiary Rocks, are found several fossil forms, constituting the
genera Edaph/tdus, Elasmodus, and Ischiodus.
SUB-ORDER B. PLAGIOSTOMI.- This sub-order is of considerably greater importance, as it includes the well-known Sharks
and Rays. The vertebral centra are usually more or less ossified, and even when quite cartilaginous, the centra are marked
out by distinct rings. The skull is in the form of a cartilaginous capsule, without distinct cranial bones. The mouth is
transverse, and is placed on the under surface of the head (fig.
149, A). The exoskeleton consists of placoid granules, tubercles, or spines. The branchial sacs open externally by as
many distinct apertures as there are sacs, and there is no operculum.  A pair of tubes proceed from the pharynx to open
on the upper surface of the head by two apertures, which are
termed " spiracles." By means of these water can be admitted
to the pharynx, and thence to the gills.
By Professor Owen the Plagiostomi are divided into three
sections, termed respectively the CestlrPzori, the Seacii, and
the Batidcs.
a. Cestraph/ori.-In this division there is a strong spine in
front of each dorsal fin, and the back teeth are obtuse. The
only living representative of this group is the Port Jackson
Shark (Cestracion PtiZippi), characterised by its pavement of
plate-like crushing teeth, adapted for comminuting small Molluscs and Crustaceans.  It is exclusively an inhabitant of the
Australian seas, and is remarkable for its close resemblance to
a large group of extinct forms, of which the best known are
the genera Hybodus and Acrodrzs from the Secondary Rocks.
b. Selachzii.-This group comprises the formidable Sharks
and Dog-fishes, and is characterised b)y the lateral position of
the branchiae on the side of the neck, and by the fact that the
pectoral fins have their ordinary form and position.  The Dogfishes are of common occurrence in British seas, but are of
little value.  Their egg-cases are frequently cast up on our
shores, and are familiarly known as " Mermaid's purses." The
true Sharks are not infrequently found in various European
seas, but they are mostly inhabitants of warmer waters. One
of the largest is the " White Shark" (Carcharias vulzg/aris),
which attains a length of over thirty feet (fig. I50, A). The
body in the Sharks (Syiualide) is not rhomboidal, but is elon



398              MANUAL OF ZOOLOGY.
gated; the nostrils are placed on the under side of the snout,
and the teeth are arranged in several rows, of which the outermost alone is employed, the inner ones serving to replace the
former when worn out.
c. Batides.-This group includes the Rays and Skates, and
is distinguished by the fact that the branchial apertures are
placed on the under surface of the body, forming two rows of
openings a little behind the
mouth. In the typical members of the group, the body
is flattened out so as to form
a kind of rhomboidal disc
(fig. 15 I), the greater part of
which is made up of the
enormously-developed pectoral fins.  Upon the upper.\. ij tsurface of the disc are the
eyes and spiracles; upon
the lower surface are the
nostrils, mouth, and branchial apertures.  The flattened bodies of the Rays,
however, must be carefully
distinguished from those of
the Flat -fishes (Pl/eLro-nectidre).  In the former, the
Fig. 1ix.-Batides. Raia marRiZnaa, dne of flat surfaces of the body are
the Skates. Reduced one -sixth. (After truly the dorsal and ventral
Gosse.)
surfaces.  In the latter, as
befoie remarked, the body is flattened, not from above downwards, but from side to side, and the head is so twisted that
both eyes are brought to one side of the body. The tail in
the Rays is long and slender, usually armed with spines, and
generally with two or three fins (the homologues of the dorsal
fins). The mouth is paved with flat teeth of a more or less
rhomboidal shape.
The typical members of the Batides are the Skates and
Rays, of which the common Thornback (Raia clavata) may
be taken as a familiar example. More remarkable than the
common Rays is the Electric Ray or Torpedo, which has the
power of discharging electrical shocks, if irritated. The identity
of the force produced in this way with the electricity of the
machine has been demonstrated by many careful experiments.
The Torpedo owes its remarkable powers to two special organs
-the- "electrical organs," which consist of two masses placed on




DIPNOI.                       399
each side of the head, and consisting each of numerous vertical
gelatinous columns, separated by membranous septa, and richly
furnished with nerves from the eighth pair; the whole arrangement presenting a singular resemblance to the cells of a.voltaic
battery. There is no doubt, however, but that the force which
is expended in the production of the electricity is only nerveforce. For every equivalent of electricity which is generated,
the fish loses an equivalent of nervous energy; and for this
reason, the production of the electric force is strictly limited by
the amount of nerve-force possessed by the animal.
Other well-known members of the family are the Sting-rays
(Trygon), the Eagle-rays (Mjliobatis), the Horned Rays (Cephalopjera), and the Beaked Rays (Rhinobatis).
In the Saw-fish (Prislis antiquorunm) the body has not the
typical flattened form of the Rays, and the snout is elongated
so as to form a long sword-like organ, the sides of which are
furnished with strong tooth-like spines. This constitutes a
powerful weapon, with which the Saw-fish attacks the largest
marine animals.
Before leaving the E2lasmobranchii, a few words may be said
as to their position in the class of fishes. From the cartilaginous nature of the endoskeleton, and the similarity between
the form of their gills and those of the Lampreys and Myxinoids, the E/asnmobrachZhii were long placed low down in the
scale of fishes, to which also the permanently heterocercal tail
conduced.  When we come, however, to take into consideration the sum of all their characters, there can be little hesitation in placing the order nearly at the summit of the entire
class. The nervous system, and especially the cerebral mass,
is very much more highly developed proportionately than is
the case with any other division of the fishes.  The organs of
sense are, comparatively speaking, of a very high grade of
organisation, the auditory organs being more than ordinarily
elaborate, the eyes being sometimes furnished with a third eyelid (memtbranla itic/itans), and the nasal sacs having a very comrn..
plex structure.  The structure of the hea.rt agrees with that of
the Ganoids, and is a decided advance upon the heart of the
more typical bony fishes.   Finally, the embryo, before its
exclusion from the egg, is furnished with external filamentous
branchife, this being a decided approximation to the Amphtibhi.
ORDER VI. DIPNOI (= Protopfei, Owen). -This order is
a very small one, and includes only the singular Mud-fishes
(Lepidosiren); but it is nevertheless of great importance as
exhibiting a distinct transition between the fishes and the A/mphibia.  So many, in fact, and so striking, are the points of




400              MANUAL OF ZOOLOGY.
resemblance between the two, that until recently the Lepidosirelz
(fig. 152) was always made to constitute the lowest class of
the Amp/aibia. The highest authorities, however, now concur in
placing it amongst the fishes, of which it constitutes the highest
order.  The order Diipwoi is defined by the following characters:-The body is fish-like in shape. There is a skull with
distinct cranial bones and a lower jaw, but the notochord is
persistent, and there are no vertebral centra, nor an occipital
condyle. The exoskeleton consists of small, horny, overlapping scales, having the "cycloid" character.  The pectoral
and ventral limbs are both present, but have the form of awlshaped, filiform, many-jointed organs, of which the former only
have a membranous fringe inferiorly. The ventral limbs are
attached close to the anus, and the pectoral arch has a clavicle;
but the scapular arch is attached to the occiput. The hinder
WV
Fig. 152.-Dipnoi. Lepidosiren annectens.
extremity of the body is fringed by a vertical median fin. The
heart has two auricles and one ventricle.  The respiratory
organs are twofold, consisting, on the one hand, of free filamentous gills contained in a branchial chamber, which opens
externally by a single vertical gill-slit; and, on the other hand,
of true lungs in the form of a double cellular air-bladder, communicating with the oesophagus by means of an air-duct or
trachea. The branchike are supported upon branchial arches,
but these are not connected with the hyoid bone; and in some
cases, at any rate, rudimentary externzal branchine   exist as well.
The nasal sacs open posteriorly into the throat.
If these characters.are examined a little more minutely, it is
easy to point to those in which the Lejidosiren approaches the
Fishes, and to those in which it resembles the Amphibians.
It resembles the Fishes in the shape of the body, and in the
possession of a covering of horny overlapping scales of the true
cycloid character; whilst the limbs are more like those of fishes
than of reptiles. The fin, also, which clothes the posterior
extremity of the body, is.of a decided fish-like character. The
most marked piscine feature, however, is the presence of free
branchime, attached to branchial arches, and Dlaced in a branchial




DIPNOI,                      40I
cavity, which opens internally into the pharynx by a number of
slits, and communicates externally with the outer world by
means of a single vertical gill-slit.
On the other hand, the Lepidosiren approximates to the
Amphibians in the following important points:-The heart
consists of three cavities, two auricles and a single ventricle.
True lungs are present, with a trachea and glottis, returning
their blood to the heart by a distinct pulmonary vein, and in
every respect discharging the functions of the lungs of the
higher Vertebrates.  It is true that the lungs of the Lepidosi-en
axe merely a modification of the swim-bladder of the other
fishes, but the significance of the change of function is not
affected by this.  Lastly, sometimes, at any rate, there are
rudimentary external branchiae placed on the side of the neck.
This feature, as will be seen shortly, is characteristic of all the
Amphibians, either permanently or in their immature state.
Upon the whole, then, whilst for the purposes of systematic
classification the Lepidosiren must be placed amongst the Fishes,
it is not to be forgotten that many of its characters are those
of a higher class, and that it may justly be looked upon as a
connecting link, or transitional form, between the two great
divisions of the Fishes and the Amphibians.
As regards their distribution and mode of life, two species
at least of ZeLpidosiren are known-the L. paaradoxa from the
Amazon, and the L. annectens from the Gambia.  They both
inhabit the waters of marshy tracts, and appear to be able in
the dry season to bury themselves in the mud, forming a kind
of chamber, in which they remain dormant till the return of the
rains. Recently there has been discovered in the rivers of
Queensland (Australia) a fish which has been described under
the name of Ceratodus (?) Fosteri, and which would appear to
be very closely related to the Lepidosiren. This singular fish is
from three to six feet long, and has the body covered with
large cycloid scales. The skeleton is notochordal, all the bones
remaining permanently cartilaginous. There is a well-developed
operculum, but-as in Lepio7siren-no branchiostegal rays.
The tail is homocercal, and the pectoral and ventral fins are
supported by a median, many-jointed, cartilaginous rod, with
numerous lateral branches on each side. The heart consists of
a single auricle and ventricle, with a "Ganoid" bulbus arteriosus. There are five branchial arches, of the Teleostean type,
but cartilaginous.  The swim-bladder is single, coilposed of
two symmetrical halves, cellular in structure, with a pneumatic
duct and glottis, as in Lepidosiren.  The intestine has a spiral
valve, and there are no pyloric ceca.




402             MANUAL OF ZOOLOGY.
Upon the whole, Dr Giinther concludes that the Dipnoi are
to be regarded as a simple sub-order of Ganoids, and that the
entire order Ganoidei may be united with the Elasmobranchii
into a single order, called Palalchtlzyes, characterised by having
a "heart with a contractile bulbus arteriosus, intestine with a
spiral valve, and optic nerves non-decussating."
CHAPTER LIX.
DISTRIBUTION OF FISHES IN TIME.
THE geological history of fishes presents some points of peculiar
interest. Of all the classes of the great sub-kingdom Verlebrata, the fishes are the lowest in point of organisation. It
might therefore have been reasonably expected that they would
present us with the first indications of vertebrate life upon the
globe; and such is indeed the case. After passing through the
enormous group of deposits known as the Laurentian, Huronian, Cambrian, and Lower Silurian formations-representing
an immense lapse of time, during which, so far as we yet know,
no vertebrate animal had been created, we find in the Upper
Silurian rocks the first traces of fish. The earliest of these, in
Britain, is found in the base of the Ludlow rocks (Lower Ludlow Shale), and belongs to the placoganoid genus Picraspis.
Also in the Ludlow rocks, but at the stun mmit of their upper
division, are found fin-spines and shagreen, pr-obably belonging
to Cestraciont fishes-that is to say, to fishes of as high a
grade of organisation as the Elasimoblanchlii. So abundant are
the remains of fishes in the next great geological epoch- namely,
the Devonian or Old Red Sandstone-that this period has
frequently been designated the "Age of Fishes."  Most of
the fishes of the Oll Red Sandstone belong to the order Ganoidci. In the Carboniferous and Permian rocks which close
the Pal ozoic period, most of the fishes are still Ganoid, but
the former contain the remains of many Plagiostomous fishes.
At the close of the Palaeozoic and the commencement of the
Mesozoic epoch, the Ganoid fishes begin to lose that predominant position which they before occupied, though they continue
to be represented through the whole of the Mesozoic and Kainozoic periods up to the present day. The Ganoids, therefore,
are an instance of a family which has endured through the
greater part of geological time, but which early attained its




DISTRIBUTION  OF FISHES IN TIME.            403
maximum, and has been slowly dying out ever since. Towards
the close of the Mesozoic period (in the Cretaceous period) the
great family of the Teleostean or Bony fishes is for the first time
known certainly to have made its appearance. The families
of the Miarsizobranch/ii, Pharyngobranchii, and Dipnoi, have
not left, so far as is known, any traces of their existence in
past time. Judging from analogy, however, it is highly probable that the two former of these must have had a vast antiquity, and it is not impossible that the so-called " Conodonts"
from the Lower Silurian rocks of Russia may yet be shown to
be the horny teeth of fishes allied to the Lampreys. At present, however, the weight of evidence is in favour of looking
upon these problematical little bodies as probably referable to
some of the 2zvertebrata.
Leaving these unrepresented orders out of consideration,
the following are the chief facts as to the geological distribution of the other great groups:I. Ganoidei.-As far as is yet known with certainty, the
oldest representatives of the fishes belong to this order. The
order is represented, namely, in the Upper Silurian rocks
by the remains of at least four genera.  In the Devonian
rocks, or Old Red Sandstone, the Ganoids attain their
maximum both in point of numbers and development. The
Placoganoid division of the order is represented by the
singular genera Pterichthys (fig. T48), Cephalaspis (fig. I47),
Pteraspis, and Coccosteus (fig. I48). The Lepidoganoid division
of the order is now also abundantly represented for the first
time, the genera Dipterus, Osteolepis (fig. I46), Glyptole is,
Ioloptychius, Dijplacanthus, and many others belonging to this
section.  As regards the further distribution of the Placoganoids, the section of the Ostracostei, characterised by the great
development of the cephalic buckler, appears to have died
out at the close of the Devonian period. The other section,
however-namely, that of the Sturionidce-is represented in
the Liassic period (Mesozoic) by the genus Chondrosteus, and
in the Eocene (Kainozoic) by a true Sturgeon, the Acipeozscr
toliapiczus.
The Lepidoganoids continue from the period of the Old Red
in great profusion, and they are represented by very many
genera in the Carboniferous and Permian rocks. In the earlier
portion of the Mesozoic period-i.e., in the Lias and Triasthey are still represented, but all the forms are as yet heterocercal. In the Oolitic rocks, for the first time, Lepidoganoids with
homocercal tails appear, and they continue to be represented
up to the present day.




404               MANUAL OF ZOOLOGY.
II. Elasmobranchii.-Like the Ganoidei, the great order of
the Sharks and Rays is one of vast antiquity. At the top of the
Upper Ludlow rocks, or at the close of the Upper Silurian
epoch, there have been discovered the remains of undoubted
Plagiostomous fishes, most nearly allied to the existing Port
Jackson Shark (Cestracion PiliZ~ppi).  These remains consist
chiefly of defensive spines, which formed the first rays in the
dorsal fins, and upon these the genus Onchus has been founded.
Besides these there have been found portions of skin or
"shagreen," with little placoid tubercles, like the skin of a
living shark. These have been referred to the genus Sphagodus.
They are the earliest-known remains of Plagiostomous fishes,
and with the exception of the few remains from the Lower
Ludlow rocks, they are the earliest known remains of fishes in
the stratified series. The discovery of these remains, at that
time the earliest known traces of Vertebrate life, is due to the
genius of Sir Roderick Murchison, the author of'Siluria.'
Most of the fossil Elasmobranchii belong to the division
Cestraphori of Owen, so called because they are provided with
the large fin-spines, which are known to geologists as "ichthyo.
2
Fig. I53.-I. Fin-spine of Pleuracanthus (one of the rays); 2. Gyracanthus; 3. Ctenacanthus; 4. Tooth of Petalodus; 5.;sanzmnowdus; 6. Ctenoitychius. All from the
Carboniferous Rocks.
dorulites." The two families of this division-the Cestracionts
and Hybodonts-are largely represented in past time, the
former chiefly in the Paleozoic period, the latter chiefly in the




DISTRIBUTION OF FISHES IN TIME.             405
Mesozoic rocks. Subjoined is an illustration of the "ichthyodorulites " and teeth of some of the Palaeozoic Cesfraphori.
The true Sharks are represented in the later Mesozoic deposits (Ag., by teeth of Notidanus in the Oolites); but they are
chiefly Tertiary.  The teeth of Odontaspis, Galeocerrdo, and
Ca-c/zarodon, are good examples from the Eocene of the Isle of
Sheppey. The true Rays are older than the true Sharks, the
Carboniferous fossil, Pleuracanthuts, being probably the spine of
a Ray (fig. I53). Numerous remains of Rays, chiefly in the
form of the pavement-like teeth, are known, both from the
Secondary and Tertiary rocks. The last division of the Elasmnobranchii-viz., that of the flolocephali, is poorly represented
in past time by the Mesozoic and Kainozoic Ischliodus, Easmodus, Ganodus, and Edaiphodus.
III. The Bony or Teleostean Fishes do not make their appearance sooner than the Cretaceous period-that is, towards
the close of the Mesozoic epoch. From this time on, however, Bony fishes with cycloid or ctenoid scales are the chief
representatives of the whole class, and the order appears to
have attained its maximum in our present seas.




DIVISION I. ICHTHYOPSIDA.
CHAPTER LX.
CLASS II. -AMPHIBIA.
THE class Amnphibia comprises the Frogs and Toads, the
Salamandroids, the Ccecilic, and the extinct Labyrinthodonts,
and may be briefly defined as follows: —As is the case with
the Fishes, the embryo is not furnished with an amnion, and
the urinary bladder is the only representative of the allantois.
As in Fishes, also, branchiwe or filaments adapted for breathing
air dissolved in water are always developed upon tle visceral
arches for a longer or shorter time.  On the other hand, the
Amphibians differ from the Fishes in the fact that true lun,,rs are
always present in the adult; the limbs are never converted into
fins; and when median fins are present, as is sometimes the case,
these are never furnished with fin-rays.  The limbs, when present, exhibit in their skeleton the same parts as do the limbs
of the higher Vertebrates.  The skull always articulates with
the vertebral column by means of two occipital condyles.  Th e
heart consists of twvo auricles and a single ventricle.'The nasal
sacs communicate posteriorly withZ the pharynx; and the rectum,
ureters, and ducts of the reproductive organs open into a commton
chamber or " cloaca."
The great and distinguishing character of the Anmphibia is
the fact that they undergo a medamorphosis after their exclusion
from the egg. They commence life as water-breathing larvae,
provided with gills or branchie; but in their adult state they
invariably possess lungs-the branchiao in the higher forms
disappearing when the lungs are developed-but being in other
cases permanently retained throughout life.
In the earliest embryonic condition the branchiae are external, placed on the side of the neck, and not situated in an
internal chamber as in Fishes.  In some cases the external
branchiae only are present, and they are, in any case, the gills
which rre retained in those forms in which the branchine are
permanent (Perennibranchiata).  In the tailed Amphibians




CHARACTERS OF AMPHIBIA.                    407
(UroZela), and in the Frogs and Toads (Anoura), two sets of
gills are developed-an external set, which is very soon lost,
and an internal set, which is retained for a longer or shorter
Fig. I54. —Anoura. Hylta leucohenia, one of the Tree-frogs (after Guinther).
period.  As maturity is approached, true lungs adapted for
breathing air are developed. The development, however, of
the lungs varies with the completeness with which aerial respiration has to be accomplished; being highest in those forms
which lose their gills when grown up (Cadzucibranchiala), and
lowest in those in which the branchixe are retained throughout
life (Perennibranchiata).
In accordance with the change from an aquatic or branchial
to a more or less completely aerial or pulmonary mode of
respiration, considerable changes are effected in the course
and distribution of.the blood-vessels. In the larval condition,
when the respiration is entirely effected by means of the gills,
the circulation is carried on very much as it is in Fishes.
The heart is composed of a single auricle and ventricle, and
the blood is propelled through a bulbus arteriosus and branchial artery to the gills.  The aerated blood is then collected
in the branchial veins, and instead of being returned to the
heart, is forthwith propelled to all parts of the body, the descending aorta being formed out of the branchial veins. At
this stage, therefore, the heart is a branchial one, and the single
contraction of the heart is sufficient to drive the blood through
both the branchlal and systemic circulations, just as we saw
was permanently the case with all the Fishes except the Lepi



408             MANUAL OF ZOOLOGY.
dosiren. The pulmonary arteries are at first very small, an l
take their origin from  the last pair of branchial arteries.
When the lungs, however, are developed, and the respiration
commences to be aerial, the pulmonary arteries increase proportionately in size, and more and more blood is gradually
diverted from the gills and carried to the lungs, so that the
branchiae suffer a proportionate diminution in size. In those
Amphibians in which branchixe are permanently retained (Perennibranchiata), this state of affairs remains throughout lifethat is to say, a portion of the venous blood is sent by the
pulmonary artery to the lungs, and a portion goes to the gills.
In those Amphibians, however, in which the adult breathes by
lungs alone (Caducibranchilata), further changes ensue.  In
these the pulmonary arteries increase so much in size that they
ultimately divert all the blood from the branchiae, and these organs, having fulfilled their temporary function, become atrophied
and disappear. The vessels which return the aerated blood from
the lungs (the pulmonary veins) increase in size proportionately
with their increased work, and ultimately come to open into
a second auricle formed at their point of union. The heart,
therefore, of the Amphibia in their adult state consists of tIelo
auricles and a common ventricle. The right auricle receives
the venous blood from the body, and the left receives the
arterial blood from their lungs, and both empty their contents
into the single ventricle. As in Reptiles, therefore, the ventricular cavity of the heart in adult Amphibians contains a mixed
fluid, partly venous and partly arterial, and from this both the
body and the lungs are supplied with blood.
As regards the digestive system of the An5hibia there is little
to say, except that the rectum, opens, as it does in Reptiles,
into a common chamber or "cloaca," into which are also discharged the secretions of the kidneys and generative organs.
A liver, gall-bladder, spleen, and pancreas are always present.
Singular pulsating cavities, belonging to the lymphatic system,
and known as "lymph-hearts," are also present in the higher
Amphibians.
CHAPTER  LXI.
ORDERS OF AMPHIBIA.
THE A4mphibia are usually divided by modern writers into four
orders, the old order Lepidota, comprising'the L-Aidosh'en,




ORDERS OF AMPHIBIA.                      409
being now placed at the head of the Fishes, under the name
of Dipnoi.  Whilst there is a general agreement as to the
number and characters of the Amphibian orders, the names
employed to designate them are very various, and it really
matters little which are adopted.
ORDER I. OPHIOMORPHA, Owen (= Gymnoplhiona, Huxley;
Apoda of older writers; Ophidobatrachia).-This is a small order,
including only certain snake-like, vermiform animals, which are
found in various tropical countries, burrowing in marshy ground,
something like gigantic earthworms. They form the family
Czeciliazdae (so called by Linnaus from  their supposed blindness), and are characterised by their snake-like form, and by
having the anus placed almost at the extremity of the body.
The skin is quite soft, but differs from that of the typical
Amphibians in mostly having small horny scales embedded in
it. Another fish-like character is that the vertebrai are amphiccelous or biconcave, and the cavities formed by their apposition are filled with the cartilaginous or gelatinous remains of
the notochord. The body is cylindrical and worm-like, and is
completely destitute of limbs. The skin is glandular, naked,
and viscous, thrown into numerous folds, and containing nuFig. 55. —Ophiomorpha. a Siljhzoanos annulatis, one of the Caecilians, much reduced
b TIead; c Mouth, shorving the tongue, teeth, and internal openings of the nostrils; d
Tail and cloacal aperture. (After Dumeril and Bibron.)
merous delicate, rounded, horny scales, which are dermal in
their character, and are wanting in SZihonops aninulaf us.  The
mandibular rami are short, and are united in front by a symphysis. The teeth are long, sharp, and generally recurved;




410              MANUAL OF ZOOLOGY.
and a row of palatine teeth forms a concentric series with the
maxillary teeth.  The tongue is fleshy, fixed to the concavity
of the lower jaw, and not protrusible (fig. I55). The ribs are
numerous, but there is no sternum. The adult possesses lungs,
one of which is smaller than the other, and the nose opens
behind into the mouth. The eyes are rudimentary, nearly
concealed beneath the skin, or altogether wanting.
The position of the Ccecilie was long doubtful; but their
Amphibian character was ultimately proved by the discovery
that whilst the adult breathes by lungs, the young possess
internal branchihe, communicating with the external world by
a branchial aperture on each side of the neck.  Only a few
species of Czecilia are known, and they are all inhabitants of
hot climates, such as South America, Java, Ceylon, and the
Guinea coast. They sometimes attain a length of several feet.
ORDER II. URODELA (=  Icht/yonwiOph/za, Owen; Sazurobatrachia).-This order is commonly spoken of collectively
as that of the "Tailed" Amphibians, from the fact that the
larval tail is always retained in the adult. The Urodeda are
characterised by having the skin naked, and destitute of any
exoskeleton.  The body is elongated posteriorly to form a
compressed or cylindrical tail, which is permanently retained
throughout life. The dorsal vertebrae are biconcave (amphicaelous), or concave behind and convex in front (ojist/hocelous),
and they have short ribs attached to the transverse processes.
The bones of the fore-arm (radius and ulna) on the one hand,
and those of the shank (tibia and fibula) on the other, are not
anchylosed to form single bones.
In one section of the order-formerly called Anmp/hizulc/asa
-the gills are retained throughout life, and the animal is therefore " perennitbranchiate."  In this section are the Protulas,
Siren, and _Menobranchus.  In the remaining members of the
order the gills disappear at maturity, and the animal is therefcre "caducibranchiate."  In this section are the land and
water salamanders.  One form, however -the Axolotl of
Mexico —appears to be sometimes caducibranchiate, though
generally perennibranchiate.  The genera Amp/hiuma and
AMenopoina, also, exhibit a partially intermediate state of parts;
for though they lose their branchiae when adult, they nevertheless retain the branchial apertures behind the head.
Of the perennibranchiate Urodela, one of the best known is
the singular Proteus (HIyjpochlt/ho) anuinzus (fig. 156), which is
only found inhabiting pools in certain caves in Illyria and
Dalmatia.  It is of a pale flesh-colour, or nearly white, with
three pairs of scarlet branchize on each side of the neck.  It




ORDERS OF AMPHIBIA.                       411
attains a length of about a foot, and has two pairs of weak
limbs, of which the anterior have three toes, and the posterior
only two. From its habitat, the power of vision must be quite
unnecessary, and, as a matter of fact, the eyes are altogether
rudimentary, and are covered by the skin.   Several varieties
of Proteus are known, and the one figured above has been
described as a distinct species (P. xanthostictus).  The bloodcorpuscles in Proteus are oval in shape, and are larger than
those of any other Vertebrate animal.
Fig. I56. -Head and fore-part of the body of Proteus anguinus, showing the
external branchiae and tridactylous fore-limb.
Of the Sirenidae, the most familiar are the Sirens and the
Axolotls.  The Siren, or Mud-eel, is found abundantly in the
rice-swamps of South Carolina, and attains a length of three
feet. The branchine are persistent, and the hinder pair of legs
wholly wanting. Two other species are known, but they are
likewise confined to North America.
The Mexican Axolotl (Siredonpisciforme, fig. I57) is a native
of the Mexican lakes, and attains a length of about a foot or
fourteen inches.  It possesses both pairs of limbs, the anterior
pair having four toes and the hinder pair five toes.  As ordinarily known in its native country, the Axolotl is certainly
perennibranchiate, and they breed in this condition freely.
There is no doubt, however, that individual specimens may
lose their gills, without thereby suffering any apparent change,
except it be one of colour. The Axolotl, therefore, is in the
singular position of being sometimes "caducibranchiate,"
whilst it is ordinarily "perennibranchiate." 1   Nearly allied
* Professor Marsh of New Haven has recently shown that the Siredon
lichenoides of the western States of America, when kept in confinement,
loses its gills, and dorsal and caudal fins, whilst it changes much in colour,
and undergoes various minor modifications in structure. Its habits, also,
become less aquatic, and it becomes apparently absolutely identical with
Amblysloma mavortiumr, a Salamandroid.  This discovery has thrown considerable doubt upon the value of the distinction between perennibranchiate
and caducibranchiate Amphibians, and has rendered it probable that all
the species of Siredon are merely larval Salamanders, as long ago suspected
by Cuvier. At the same time, the Axolotls certainly breed freely whilst in
possession of their branchice, and there is as yet no proof that they lose
their gills whilst in a state of nature.
19




412               MANUAL OF ZOOLOGY.
to the AxolotI is the Menobranchus of North America, in
which the branchie are persistent.  Amphiuma and Menopjoma,
as already remarked, differ from the forms just mentioned in
losing the gills when adult, but in retaining the external branchial apertures on the side of the neck.  The former is
exclusively North American, whilst the latter is represented
by different but nearly-related species in both North America
and Java.  Both possess the
normal two pairs of limbs. The
Javanese  species  (Menoopoma
maxima) has the gill-Slit closed
in the adult.  It is about three
feet long, and is the nearest
living relative of the extinct
Andrias.
In the second section of the
Urodela, comprising those forms
iln which the gills are caducous,
and both pairs of limbs are
always present, are the Watersalamanders or Tritons, and the
ILand- salamanders. The Tritons are the only examples of
the aquatic Salamanders which
occur in Britain, and every one,
probably, is acquainted with
the common Newt.
The Water- salamanders or
Newts  (fig. I59) are  distinguished  from  the  terrestrial
forms by being furnished with
a compressed fish-like tail, and
by  being  strictly  oviparous.
The larvae are tadpole -like,
with external branchie, which
they retain till about the third
month. The adult is destitute
of gills, and breathes by lungs
alone, but the larval tail is retained throughout the life of
Fig. 57. —The Axolotl (Siredonisciforme) the animal.   The tongue is
-after Tegetmeier. The ordinary form, small, free, and pointed bewith persistent branchiae.
hind, and there are two rows
of palatine teeth.  The fore-feet are four-toed, the hind-feet,
five-toed; and the males have a crest on the back and tail.




ORDERS OF AMPHIBIA.                  413
The development of the Newts is so like that of the Frogs
that it is unnecessary to dilate. further upon it here; but there
are these two points of difference to be noticed: —Istly, That
the embryonic tail is not cast off in the adult; and, 2dy, That
the fore-limbs are developed sooner than the hind-limbs-the
reverse of this being the case amongst the Anoura.
---
Fig. I58.-Great Water-newt (Triton cristatus) —after Bell.
The Land-salamanders form the genus Salamandra, and are
distinguished from their aquatic brethren by having a cylindrical instead of a compressed tail, and by bringing forth their
young alive, or by being ovo-viviparous, in which case the
larvae have sometimes shed their external branchiae prior to
birth. The head is thick, the tongue broad, and the palatine
teeth in two long series. The skin is warty, with many glands
secreting a watery fluid.  The best-known species is the S.
imaculosa of Southern Europe.  Another species (S. a/pina)
lives upon lofty mountains. The chief thing to remember
about the Land-salamanders, and, indeed, about all the Urodela, is their complete distinctness from the true Lizards (Lacerfi/ia). They are often completely lizard-like in form when adult,
but they always possess gills in the earlier stages of their existence, and this distinguishes them from all the Lacertilians.
ORDER III. ANOURA (= Batrachia, Huxley; Theriozmonpha,
Owen; Chelonobatrac/hia, &c.)-This order includes the Frogs
and Toads, and is perhaps best designated by the name of
Anoura, or "Tail-less'i Amphibians.  The name 7Batlachia,
employed by Huxley, is inexpedient, partly because it is used
by Owen to designate the entire class Amnphibia, and partly
because, in common language, it is usual to understand by a
"Batrachian" any of the higher Amphibians-such, for instance,
as a Labyrinthodont.
The Anoura, or Tail-less Amphibians, are characterised by
the following points:- The adult is destitute of both gills and
tail, both of which structures exist in the larva, whilst the two




414              MANUAL OF ZOOLOGY.
pairs of limbs are always present. The skin is soft, and there
are rarely any traces of an exoskeleton. The dorsal vertebrae
are "procoelous," or concave in front, and are furnished with
long transverse processes, which take the place of ribs, which
are only present in a rudimentary form. The radius and ulna
in the fore-limb, and the tibia and fibula in the hind-limb, are
anchylosed to form  single bones (fig. 159). The mouth is
sometimes edentulous, but the upper jaw has usually small
teeth, and the lower jaw sometimes. The hind-limbs usually
have the digits webbed for swimming, and are generally much
larger and longer than the fore-limbs.  The vertebral column
is short (of ten vettebrae in the Frogs, but only eight in Pipa).
The tongue is soft and fleshy, not supported by an os hyoides,
but fixed to the symphysis of the lower jaw in front. Pipa has
a sort of valve over the tympanum; HNya and Rana have the
tympanum shown externally; and Bufo has the tympanum
concealed.
Fig. 159. -Skeleton of the common Frog (Rana temporaria). d Dorsal Vertebrae,
with long transverse processes.
In the adult Anoura, respiration is purely aerial, and is carried on by means of lungs, which are, comparatively speaking,
well developed. As there are no movable ribs by which the
thoracic cavity can be expalnded, the process of respiration is
somewhat peculiar. The animal first closes its mouth, and
fills the whole buccal cavity with air taken in through the




ORDERS OF AMPHIBIA.                       415
nostrils. The posterior nares are then closed, and by the contraction of the muscles of the cheeks and pharynx the inspired
air is forcibly driven into the windpipe through the open glottis.
The process, in fact, is one of swallowing; and it is possible to
suffocate a frog simply by holding its mouth open, and thereby
preventing the performance of the above-mentioned actions.
There can be no doubt, also, that the skin in these animals
plays a very important part in the aeration of the blood, and
that the frogs especially can carry on their respiration cutaneously, without the assistance of the lungs, for a very lengthened
period. This undoubted fact, however, should not lead to any
credence being given to the often-repeated stories of the occurrence of frogs and toads in cavities in solid rock, no authen.
ticated instance of such a phenomenon being as yet known to
science.
Fig. 60o.-Development of the common Frog (Rana tenfioraria). a Tadpole, viewed
from above, showing the external branchiae (g); b Side view of a somewhat older
specimen, showing the fish-like tail; c Older specimen, in which the hind-legs have
appeared; d Specimen in which all the limbs.are present, but the tail has not been
wholly absorbed. (After Bell.).
The young or larvae of the Frogs and Toads are familiarly
known as "Tadpoles." The ova of the Frog are deposited in
masses in water, and the young form, upon exclusion from the
egg, presents itself as a "tailed" Amphibian, completely fishlike in form, with a broad rounded head, a sac-like abdomen,
and a compressed swimming-tail (fig. i6o, a). There are at
first two sets of gills, one external and the other internal. The
external branchiae (fig. I6o, a) have the form of filaments attached to the side of the neck, and they disappear very shortly
after birth. The internal branchiae are attached to cartilaginous
arches, which are connected with the hyoid bone, and they are




416             MANUAL OF ZOOLOGY.
contained in a gill-cavity, protected by a flap of integument,
which differs from the gill-cover of fishes in never developing
any opercular bones or branchiostegal rays. Within the branchial chamber thus formed the fore-limbs are budded forth, but
the hind-limbs are the first to appear, instead of the fore-limbs,
as is the case with the Urodela.  Even after the first appearance of the limbs, the tail is still retained as an instrument of
progression; but as the, limbs become fully developed, the
tail is gradually absorbed (fig. i6o, d), until in the adult it has
wholly disappeared.
The development of the Frog is thus a good illustration of
the general zoological-law that the transient embryonic stages
of the higher members of any division of the animal king'dom
are often represented by the permanent condition of the lower
members of the same division. Thus the transitory condition
of the young Frog in its earliest stage, when the branchiae are
external, is permanently represented by the adult perennibranchiate Urodela, such as the Proteus or the Siren. The
final stage, again, when the gills have disappeared and the limbs
have been developed, but the tail has not been wholly absorbed,
is represented by the caducibranchiate Urodela, such as the
common Newt.
The order Anoura comprises a considerable number of
forms, but may be divided into the three sections of the
Pipidce, Bufonidne, and Ranidw. In the Pipid&e, or Surinam
Toads, there are rarely teeth, and the mouth is destitute of a
tongue. A singular and hideous species (Pitza IAmericana) is
the best known, and it inhabits Brazil and Surinam. In this
curious Amphibian the eggs are placed by the rrale on the
back of the female, in the integument of which, in cell-like
cavities, the eggs are hatched and the young developed. InT
the aberrant form Dactylethra the upper jaw is furnished with
small teeth, and the three inner toes of the hind-feet are furnished with nails, as is the case with no other Amphibian.
except Salamandra unguicZuata amongst the Urodela.  This
curious form is found at the Cape of Good Hope and in Mozambique.
In the Toads, or Bzf;i&Ee, a tongue is present, but tile
jaws are not armed with teeth. The tongue agrees with that
of the Frogs in being fixed to thefront of the mouth, whilst it
is free behind, so that it can be protruded for some distance
from the mouth. The hind-limbs are not disproportionately
developed, whilst the toes are only imperfectly webbed, and
the toes of the fore-limb are free. The skin is warty and glandular. The common Toad (Bifo vulgaris) is an excellent




ORDERS OF AMPHIBIA.                 417
example of this family. The Natter-jack Toad is the only
other British species, but about fifty other forms are known, of
which many are American.
In the Ranide  the tongue has the same form as in the
Toads, but the upper jaw always carries teeth. The hindlimbs are much larger than the fore-limbs, and are fitted for
leaping, whilst the toes are webbed. The toes of the forelimbs are free. The common Frog (Rana temniporaria) is a
good example of the typical Ranide. Larger than the common
Frog is the Eatable Frog (Rana esculenta) of Europe, and larger
again than this is the Bull-frog (Rana pipiens) of North America. The Tree-frogs (Hyla) are adapted for a wholly different
mode of life, having the toes of all the feet furnished with terminal suckers, by the help of which they climb with ease.
They are mostly found in warm countries, especially in America, but one species (Hyla arborea) is European (fig. 154).
ORDER IV. LABYRINTHODONTIA. — The members of this,
the last order of the Amphibia, are entirely extinct. They
were Batrachians, probably most nearly allied to the Urodeda,
but all of large size, and some of gigantic dimensions, the skull
of one species (Labyrinthodon Jagaeri) being upwards of three
feet in length and two feet in breadth. The Labyrinthodonts
were first known to science simply by their footprints, which
were found in certain sandstones of the age of the Trias.
These footprints consisted of a series of alternate pairs of
hand-shaped impressions. the hinder print of each pair being
much larger than the one in front (fig. I6I).  So like were
these impressions toethe shape of the human hand that the
unknown animal which produced them was at once christened
Cheirotherium, or " Hand-beast." Further discoveries, however,
soon showed that the footprints of Cheirotherium had been
produced by different species of Batrachians, to which the
name of Labyrinthodonts was applied, in consequence of the
complex microscopic structure of the teeth.
Fig. r6r.-Footprints of a Labyrinthodont (Cheirokherium).
The Iabyrinthodonts were " salamandriform, with relatively
weak limbs and a long tail."-(Huxley.)  The vertebralscentra
and arches were ossified, and the bodies of the dorsal vertebrae




418             MANUAL OF ZOOLOGY.
are biconcave (amphiccelous). " In the thoracic region three
superficially-sculptured exoskeletal plates, one median and two
lateral, occupy the place of the interclavicle and clavicles.
Between these and the pelvis is a peculiar armour, formed of
rows of -oval dermal plates, which lie on each side of the
middle line of the abdomen, and are directed obliquely forwards and inwards to meet in that line."-(Huxley.)
The head was defended by an external covering or helmet
of hard and polished osseous plates, sculptured on their external surface, and often exhibiting peculiar, smooth, symmetrical
grooves-the so-called "mucous canals." The skull was articulated to the vertebral column by two occipital condyles.
The teeth are rendered complex by numerous foldings of their
parietes, giving rise to the "labyrinthine " pattern, from which
the name of the order is derived.
The Labyrinthodonts are known to occur from the Carboniferous to the Triassic or Liassic period inclusively; but they
are most characteristically and distinctively Triassic.
DISTRIBUTION OF AMPHIBIA IN TIME.-From a geological
point of view, by far the most important of the Anzphibia are
the Labyrinthodonlita, the distribution of which has just been
spoken of. The living orders of Amhkibia are of much more
modern date, being, as far as known, wholly Tertiary and
Post-tertiary. The Anoura are represented by both Toads
and Frogs in Miocene times, and they have survived to the
present day. The " Tailed" Amphibians are best known to
geologists by a singular fossil, which was described by its original discoverer as human, under the name of Hlomo dihuvii
test/is. The fossil in question is of Miocene age, and it is now
known to belong to a Salamander, nearly allied to the giantsalamander of Java (Menopoma). It is termed the Andrias
Scheuchzeri.




DIVISION II. SA UROPSIDA.
CHAPTER LXII.
CLASS III.-REPTILIA.
THE second great division of the Vertebrate sub-kingdom,
according to Huxley, is that of the Sauropsida, comprising the
true Reptiles and the Birds. It is, no doubt, at first sight an
almost incredible thing that there should be any near bond of
relationship between the Birds and the Reptiles, no two classes
of animals being more unlike one another in habits and external appearance.  It is, nevertheless, the fact that the Birds
are more nearly related to the Reptiles than to any other -class
of the Vertebra/a, and it will shortly be seen that many affinities and even transitional forms are known to exist between
these great sections. The Reptiles and Birds, then, may be
naturally included in a single primary section of Vertebrates,
which may be called Sauropsida after Huxley, and which is
defined by the possession of the following characters:-At no
period of existence are branchie, or water-breathing respiratory
organs, developed upon the visceral arches; the embryo is
furnished with a well-developed amnion and allantois; the red
corpuscles of the blood are nucleated (fig. I30, b, c); the skull
articulates with the vertebral column by means of a single
articulating surface or condyle; and each half or "ramus" of
the lower jaw is composed of several pieces, and articulates
with the skull, not directly, but by the intervention of a peculiar bone, called the " quadrate bone," or "os quadratum"
(fig. I62).
These being the common characters of Reptiles and Birds
by which they are collectively distinguished from other Vertebrates, it remains to inquire what are the characters by which
they are distinguished from one another. The following, then,
are the characters which separate the Reptiles from the Birds:
-The blood in Reptiles is cold-that is to say, slightly warmer
than the external medium —owing mainly to the fact that the
pulmonary and systemic circulations are always directly con



420              MANUAL OF ZOOLOGY.
nected together, either within the heart or in its immediate
neighbourhood, so that the body is supplied with a mixture of
venous and arterial blood, in place of pure arterial blood alone.
The terminations of the bronchi at the surface of the lung are
closed, and do not communicate with air-sacs, placed in different parts of the body. When the epidermis develops horny
structures, these are in the form of horny plates.or scales, and
never in the form of feathers. The fore-limbs are formed for
various purposes, including in some cases even flight, but they
are never constructed upon the type of the "wings " of Birds.
Lastly, with one or two doubtful exceptions, whilst the anklejoint is placed between the distal and proximal portions of the
tarsus, the tarsal and metatarsal bones of the hind-limb are
never anchylosed into a single bone.
These are the leading characters by which Reptiles are distinguished from Birds, but we must not forget the other distinctive peculiarities in which Reptiles agree with Birds, and
differ from other Vertebrates-namely, the presence of an
amnion and allantois in the embryo, the absence of branchixe
at all times of life, the possession of only one occipital condyle,
and the articulation of the complex lower jaw with the skull by
means of a quadrate bone.
It is now necessary to consider these characteristics of the
Reptiia a little more minutely. The class includes the Tortoises and Turtles, the Snakes, the Lizards, the Crocodiles, and
a number of extinct forms; and with the exception of the Tortoises and Turtles they are mostly of an elongated cylindrical
shape, provided posteriorly with a long tail. The limbs may
be altogether absent, as in the Snakes, or quite rudimentary,
as in some of the Lizards; but, as a general rule, both pairs of
limbs are present, sometimes in the form of ambulatory legs,
sometimes as swimming-paddles, and in some extinct forms
modified to subserve an aerial life.  The endoskeleton is
always well ossified, and is never cartilaginous or semi-cartilaginous, as in many fishes, and some Amphibians.  The skull
articulates with the atlas by a single condyle.  The lower jaw
is complex, each half or ramus being composed of from four to
six pieces, united to one another by sutures (fig. I62).  In the
Tortoises, however, these are anchylosed into a single piece,
and the two rami are also anchylosed. In most Reptiles, however, the two rami of the lower jaw are only loosely unitedin the Snakes by ligaments and muscles only, in the Lizards
by fibro-cartilage, and in the Crocodilia by a regular suture.
In all, the lower jaw articulates with the skull by a quadrate
bone (fig. I62, a); and as this often projects backwards, the




CHARACTERS OF REPTILIA.                   42I
opening of the mouth is often very extensive, and may even
extend beyond the base of the skull. Teeth are usually present, but are not sunk in separate sockets or alveoli, except in
&.
Fig. I62. —Skull of a Serpent (Pylhon). b Articular portion of the lower jaw;
a Quadrate bone; c Squamosal portion of the temporal bone.
the Crocodiles. In the Tortoises and Turtles alone there are
no teeth, and the jaws are simply sheathed in horn, constituting
a kind of beak like that of a bird.
Ribs are always present and always well developed, but they
differ much in form. It is not correct, however, to regard the
presence of ribs as separating the true Reptiles from the Amphibia, as is sometimes stated. Some of the most Lizard-like
of the Amphibians, such as the Siren, possess short but welldeveloped ribs, and rudiments of ribs are traceable in other
orders; whilst in the CGeciZice they are large and well developed.
As regards the exoskeleton, all Reptiles have horny epidermic scales, and they are divided into two great sections-called
respectively Squamata and Loricata-according as the integumentary skeleton consists simply of these scales, or there are
osseous plates developed in the derma as well. In the Tortoises, the epidermic plates unite with the bony exoskeleton
and with the true endoskeleton to form the case or box in
which the body of these animals is enclosed.
The digestive system of the Refti/ia possesses few characters
of any special importance, except that the rectum opens, as
in Amphibia, into a common cavity or "cloaca," which not
only receives the faeces, but also serves for the discharge of
the products of the urinary and generative organs.
The heart in the Reptiles consists of two completely separate
auricles, and a ventricular cavity, which is divided into two by
an incomplete partition. In the Crocodilia alone is the septum




422                MANUAL OF ZOOLOGY.
between the ventricles a perfect one, and even in these, as in
all other Reptiles, the heart consists functionally of no more
than three chambers. The ordinary course of the circulation,
where the ventricular septum  is imperfect, is as follows: —The
impure venous blood returned
from  the  body is, of course,
poured by the venae cavae into the
right auricle (fig. I63, q), and
thence into the ventricle.  The
pure  arterialised  and  aerated
blood that has passed through
the lungs, is, equally of course,
poured into the left auricle (a'),
and thence propelled  into  the
a-.'a} h   [ —'d  ventricle (v).  As the ventricular
cavity is single, and not divided
by a complete partition, it follows of necessity that there is a
mixture in the ventricle, resulting
"  II   v,7          in the production  of a mixed
fluid, consisting partly of venous
0 o    and  partly  of arterial blood.
This mixed fluid, then, occupies
the common ventricular cavity,
and by this it is driven both to
the lungs (through the pulmonary
artery), and to the body (through
Fig. 163.-Diagram of the circulation in the  systemic  aorta).   ConseReptiles. (The venous system is left quently, in  Reptiles, both  the
light, the arterial system is black, and  X
the vessels containing mixed blood are lungs and the various tissues and
cross-shaded.) a Right auricle, receiv- organs of the body are supplied
ing venous blood from the body; a'
Left auricle, receiving arterial blood with a mixture of arterial and
from the lungs; v Arterio-venous ven- venous blood, and not with untricle, containing mixed blood, which is   blood
driven by (i) the pulmonary artery to mixed blood -the  lungs with
the lungs, and by (o) the aorta to the
body.                        purely venous, and the body with
purely arterial blood-as is the
case with the higher Vertebrata. In the Crocodilia, as before
said, the partition between the ventricles is a complete one,
and consequently this mixture of the arterial and venous blood
cannot take place within the heart itself.  In- these Reptiles,
however, a direct communication exists between the pulmonary
artery and aorta (the right and left aorte) by the so-called
"foramen Panizzae," close to the point where these vessels
spring respectively from the right and left ventricle. In these
Reptiles, therefore, the same mixture of arterial blood with




DIVISIONS OF REPTILES.               423
venous takes place as in the lower Refpilia, though probably
not to so complete an extent. It is this peculiarity of the
circulation in all Reptiles which conditions their low temperature, slow respiration, and generally sluggish vital actions.
The lungs in all Reptiles, except the Crocodiles, are less
completely cellular than in the Birds and Mammals, and they
often attain a very great size. In no Reptile is the cavity of
the thorax shut off from that of the abdomen by a complete
muscular partition or " diaphragm;" though traces of this
structure are found in the Crocodiles. The lungs, therefore,
often extend along the whole length of the thoracico-abdominal
cavity. In no case are the lungs connected with air-receptacles
situated in different parts of the body; and not uncommonly
there is only a single active lung, the other being rudimentary
or completely atrophied (Ophidia).
Lastly, all reptiles are essentially oviparous, but in some
cases the eggs are retained within the body till the young are
ready to be excluded, and the animals are then ovo-viviparous.
The egg-shell is usually parchment-like, but sometimes contains
more or less calcareous matter.
CHAPTER LXIII.
DIVISIONS OF REPTILES.
CHELONIA AND OPHIDIA.
THE class Reptilia is divided into the following nine orders,
of which the first four are represented by living forms, whilst
the remaining five are extinct:I. Chelonia (Tortoises and Turtles).
2. Op/hidia (Snakes).
3. Lacer/ilia (Lizards).
4. Crocodilia (Crocodiles and Alligators).
5. Ich/It/yopterygia.
6. Saurofpterygia.
7. Anomnodontia.                Extinct.
8. Pterosauria.
9. Deinosauria.
ORDER I. CHELONIA. —The first order of living Reptiles is
that of the Chelonia, comprising the Tortoises and Turtles, and




424              MANUAL OF ZOOLOGY.
distinguished by the following characters:-There is all osseous
exoskeleton which is combined with the endoskeleton to form
a kind of bony case or box in which the body of the animal is
enclosed, and which is covered by a leathery skin, or, more
usually, by horny epidermic plates. The dorsal vertebra, with
the exception of the first, are immovably connected together,
and are devoid of transverse processes. The ribs are greatly
expanded (fig. I64, r), and are united to one another by
sutures, so that the walls of the thoracic cavity are immovable.
All the bones of the skull except the lower jaw and the hyoid
bone are immovably united together. There are no teeth, and
the jaws are encased in horn so as to form a kind of beak.
The tongue is thick and fleshy. The heart is three-chambered,
the ventricular septum being imperfect. There is a large urinary bladder, and the anal aperture is longitudinal or circular.
The lungs are voluminous, and respiration is by swallowing air,
as in the Frogs. All will pass prolonged periods without food,
and will live and move, even for months, after the removal of
the entire brain. —(Redi.)
Of these characters of the Chelonia, the most important and
distinctive are the nature of the jaws, and the structure of the
exoskeleton and skeleton.  As regards the first of these points,
the lower jaw in the adult appears to consist of a single piece,
its complex character being masked by anchylosis. The separate pieces which really compose each ramus of the jaw are
immovably anchylosed together, and the two rami are also
united in front by a true bony union.  There are also no
teeth, and the edges of the jaws are simply sheathed in horn,
constituting a sharp beak.  In the Che/ydida: and T'rionjzcidce,
however, the horny jaws are covered with soft skin, constituting
a kind of lips. As regards the second of these points, the bony
case in which the body of a Chelonian is enclosed consists
essentially of two pieces, a superior or dorsal piece, generally
convex, called the " carapace," and an inferior or ventral piece,
generally flat or concave, called the "plastron."  The carapace
and plastron are firmly united along their edges, but are so
excavated in front and behind as to leave apertures for the
head, tail, and fore and hind limbs. The limbs and tail can
almost always be withdrawn at will under the shelter of the
thoracico-abdominal case formed in this way by the carapace
and plastron, and the head is also generally retractile.
The carapace or dorsal shield is composed of the following
elements:
i. The spinous processes of the dorsal vertebrta, which are
much flattened out laterally and form a series of broad plates.




DIVISIONS  OF REPTILES.                     425
2. The ribs, which are also much flattened and expanded, and
constitute what are known as the "costal plates" (fig. I64, r).
They are generally eight in number on each side, and are
commonly united throughout the whole of their lateral margins
by sutures. In some cases, however, they leave marginal
apertures towards their extremities, and these openings dre
simply covered by a leathery skin or by horny plates. 3. The
margin of the carapace is completed by a series of bony plates,
which are called the "marginal plates."  These are variously
Fig. I6S —':eleton of Tortoise (Emsys Euroecnq), the plastron being removed. ca
Carmpace; r Ribs, greatly expanded, and united by their edges; s Scapular arch,
placed within the carapace, and carrying the fore-limbs; A Pelvic arch, also placed
within the carapace, and carrying the hind-limbs.
regarded as being dermal bones belonging to the exoskeleton,
or as being endoskeletal, and as representing the ossified
cartilages of the ribs (in this last case the marginal plates
would correspond with what are known as the " sternal ribs"
of Birds).
The " plastron" or ventral shield is composed of a number
of bony plates (nine in number), the nature of which is doubt



426              MANUAL OF ZOOLOGY.
ful.  By some, the plastron is still regarded as a greatly-developed breast-bone or sternum. By others, again, the Cheelonia
are regarded as being wholly without a sternum, and the
bones of the plastron are looked upon as exclusively integumentary ossifications.  Both the carapace and the plastron
are covered by a leathery skin, or more generally by a series
of horny plates (fig. I65), which roughly correspond with
the bony plates below, and which constitute in some species
the "tortoise-shell" of commerce.  These epiderimic plates,
however, must on no account be confounded with the true
bony box in which the animal is enclosed, and which is produced partly by the true endoskeleton and partly by dermal
integumentary ossifications.
The other points of importance as regards the endoskeleton
are these:
Firstly, The dorsal vertebrae are immovably joined together,
and have no transverse processes, the heads of the ribs uniting
directly with the bodies of the vertebrae.
Secondly, The scapular and pelvic arches, supporting the
fore and hind limbs respectively (fig. I64, s and p), are placed
-within the carapace, so that the scapular arch is thus inside the
ribs, instead of being outside, as it normally is. The scapular
arch consists of the shoulder-blade or scapula, and two other
bones, of which one corresponds with the acromion process of
human anatomy, and the other to the coracoid process, or to
the "coracoid bone" of the Birds.  The clavicles, as is also
the case with the Crocodilia, are absent.
The order Chelonia is conveniently divided into three se>tions, according as the limbs are natatory, amphibious, or terrestrial. In the first of these, the limbs are converted into
most efficient swimming-paddles, all the toes being united by a
common covering of integument. In this section are the wellknown Turtles ( Cheloniidc), all of which swim with great ease and
power, but are comparatively helpless upon the land (fig. I65).
The legs are of unequal length, and the carapace is much depressed and flattened. The best-known species are the "edible"
or Green Turtle (Chzelonza mydas), the Loggerhead Turtle
(Chelonia caouanna), the Hawk's-bill Turtle (C. irmbricata),
and the Leathery Turtle (Spiargis coriacea). The Green Turtle
is largely imported into this country as a delicacy, and occurs
abundantly in various parts of the Atlantic and Indian Oceans.
The Hawk's-bill Turtle is of even greater commercial importance, as the horny epidermic plates of the carapace constitute
the " tortoise-shell" so largely used for ornamental purposes.
The Leathery Turtle is remarkable in having the carapace




CHELONIA.                       427
covered with a leathery skin in place of the horny plates which
are found in other species.
In the second section of the Celzonia, in which the limbs are
adapted for an amphibious life, are the Mud-turtles or Soft
Tortoises (Trionycidce), and the Terrapins (Ernmydidc).  In the
Trionycidde the development of the carapace is imperfect, the
ribs being expanded and united to one another only near their
bases) and leaving apertures near their extremities.  The
entire carapace is covered by a smooth leathery skin, and the
horny jaws are furnished with fleshy lips.  All the Trionycide
inhabit fresh water and are carnivorous in their habits. Good
examples are found in the Soft-shelled Turtle (Trionyxferox),'Fig. i65 —Hawk's-bill Turtle (Ch'a im'bricata) —after Bell.Fig. 165.-Hawk's-bill Turtle (Cheionia imnbricafa)-after Bell.
and the large and fierce Snapping Turtle (Chelydra serpentita)
of the United States; but other species are found in Egypt
and in the East Indies. The Terrapins (Emys) have a horny
beak, and have the shield covered with epidermic plates. They
are inhabitants of fresh water, and are most of them natives of
America.
The third section of the Chelonia comprises only the Land
Tortoises (Testudinitde), in which the limbs are adapted for terrestrial progression, and the feet are furnished with short nails.
The carapace is strongly convex, and is covered by horny epidermic plates; the head, limbs, and tail can be completely retracted within the carapace. Though capable of swimming,
the Tortoises are really terrestrial animals, and are strictly




428             MANUAL OF ZOOLOGY.
vegetable-feeders. The most familiar species is the Tesfuwbo
Grceca, which is indigenous in Spain, Italy, and Greece.  A
much larger species is the Indian Tortoise (Testudo Indica),
which attains a length of over three feet.
DISTRIBUTION OF CHELONIA IN TIME.-The earliest-known
traces of Chelonians occur in the Permian rocks, in the lower
portion, that is, of the New Red Sandstone of older geologists.
These traces, however, are not wholly satisfactory, since they
consist solely of the footprints of the animal upon the ripplemarked surfaces of the sandstone. Of this nature is the Chelichnus Duncani, described by Sir William Jardine in his classical
work on the " Ichnology" of Annandale in Dumfriesshire. The
earliest unequivocal remains of Chelonians are in the Oolitic
rocks (the Clic/lzia _planiceps of the Portland Stone).  Fossil
C/eloniiide, Emar,/idce, and Trionycidze occur, also, fi-om the
Upper Oolites to the present day, the Eocene period being
peculiarly rich in their remains. In the Tertiary deposits of
India (Sivalik Hills) there occurs a gigantic fossil Tortoisethe Colossochelys Atlas-which is believed to have been eighteen
to twenty feet in length, and to have possibly survived to
within the human period.
ORDER II. OPHIDIA.-The second order of Reptiles is
that of the Ophidia, comprising the Snakes and Serpents, and
distinguished by the following characters:The body is always more or less elongated, cylindrical, and
worm-like, and whilst possessing a covering of horny scales, is
always unprovided with a bony exoskeleton. The dorsal vertebrae are concave in front (proccelous), with rudimentary transverse processes. There is never any sternum, nor pectoral
arch, nor fore-limbs, nor sacrum, and as a rule there are no
traces of hind-limbs. Rudimentary hind-limbs, however, are
occasionally present (e.g., in Python and Tortrix).  There are
always numerous ribs. The two halves or rami of the lower
jaw are composed of several pieces, and the rami are united
anteriorly by ligaments and muscles only, and not by cartilage
or suture. The lower jaw further articulates with the skull by
means of a quadrate bone (fig. I62, a), which is always more
or less movable, and is in turn united with the squamous portion of the temporal bone (" mastoid bone "), which is also
movable, and is not firmly united with the skull. The superior
maxillae are united with the prxemaxillx by ligaments and
muscles only, and the palatine arches are movable and armed
with pointed recurved teeth. Hooked conical teeth are always
present, but they are never lodged in distinct sockets or alveoli.
Functionally, they are capable of performing nothing more




OPHIDIA.                     429
than merely holding the prey fast, and the Snakes are provided
with no genuine masticatory apparatus. The heart has three
chantbers, two auricles and a ventricle, the latter imperfectly
divided into two cavities by an incomplete septum. The lungs
and other paired organs are mostly not bilaterally symmetrical,
one of each pair being either rudimentary or absent. There is
no urinary bladder, and the cloacal aperture is transverse.
Of these characters of the snakes, the most obvious and
striking are to be found in the nature of the organs. of locomotion. The front'limbs, with the scapular arch and sternum,
are invariably altogether absent; and the hind-limbs, if not
wholly wanting, are never represented by more than an imperfectly - developed series of bones concealed within the
muscles on each side of the anal aperture, and never exhibiting
any outward evidence of their existence beyond the occasional
presence of short horny claws or spurs (" calcaria "). In the
entire absence, then, or rudimentary condition of the limbs,
the Snakes progress by means of the ribs. These bones are
always extremely numerous (sometimes amounting to more
than three hundred pairs), and in the absence of a sternum,
they are, of course, extremely movable. Their free extremities,
in fact, are simply terminated by tapering cartilages, which are
attached by muscular connections to the abdominal scales or
"scuta" of the integument.  By means of this arrangement
the Serpents are enabled to progress rapidly, walking, so to
speak, upon the ends of their ribs; their movements being
much facilitated by the extreme mobility of the whole vertebral
column, conditioned by the cup-and-ball articulation of the
bodies of the vertebrae with one another.
The body in the Snakes is covered with numerous scales,
developed apparently in the lower layer of the epidermis, and
covered by a thin, translucent, superficial pellicle, which is periodically cast off and renewed. On the head and along the
abdomen these scales are larger than over the rest of the body,
and they constitute what are known as the " scuta" or shields.
The only other points in the anatomy of the Ofp/idia which
demand special attention are the structure of the tongue, teeth,
and eye.
The tongue in the Snakes is probably an organ more of
touch than of taste.  It consists of two muscular cylinders,
united towards their bases, but free towards their extremities.
The bifid organ, thus constituted, can be protruded and
retracted at will, being in constant vibration when protruded,
and being in great part concealed by a sheath when retracted.
As regards the eye of Serpents (fig. I66, A), the chief




430                MANUAL OF ZOOLOGY.
peculiarity lies in the manner in which it is protected externally. There are no eyelids, and hence the stony unwinking
Fig. 66. A, Diagram of the    Be
Fig. i66.-A, Diagram of the eye of a Serpent (after Cloquet): a Ball of the eye
covered by a conjunctival sac, into which the lachrymal secretion is discharged;
b Optic nerve; d Antocular membrane, formed by the epidermis; e e Ring of scales
surrounding the eye. B, Head of the common Viper (Pelias berus)-after Bellshowing the bifid tongue, and the poison fangs in the upper jaw.
stare of all snakes. In place of eyelids, the eye is surrounded
by a circle of scales (e e), to the circumference of which is
attached a layer of transparent epidermis, which covers.the
whole eye (d), and is termed the antocular membrane. This
is covered internally by a thin layer of the conjunctiva, which
is reflected forwards from the conjunctiva covering the ball of
the eye itself. In this way a cavity or chamber is formed
between the two layers of conjunctiva, and the lachrymal
secretion by which the eye is moistened is received into this.
The outer epidermic layer (antocular membrane) covering the
ball of the eye in front, is periodically shed with the rest of the
epidermis, the animal being rendered thereby blind for a few
days. The pupil of the eye is round in most Snakes, but forms
a vertical slit in the venomous Serpents and in the Boas.
As regards the dental and maxillary apparatus of the
Serpents, the following points require  notice:-Fir-s/fy, in
consequence of the articulation of the lower jaw with a
movable quadrate bone, which is often directed backwards,
in consequence of the quadrate bone being connected with a
movable squamosal bone, and in consequence of' the rami of
the jaw being united in front by ligaments and muscles only,
the mouth in the Snakes is capable of opening to an enormous
width, and the most astonishing feats in the way of swallowing
can be performed.  Secondly, this structure of the jaws accords
exactly with the structure of the teeth, both concurring to'
render the Snakes whclly incapable of anything like mastication, and at the same time capable of swallowing immense




OPHIDIA.                     431
morsels entire.  The teeth, namely, are simply fitted for
seizing and holding the prey, but not in any way for dividing
or chewing it. In the non-venomous and most typical Snakes,
the jaws and palatine bones carry continuous rows of solid
conical teeth, so that there are four rows above and two below;
and the superior maxillae are very long and are not movable.
Thirdly, in the Viperine Snakes the ordinary teeth are wanting
upon the superior maxillae, whilst these bones are themselves
very much shortened, and are capable of being raised and
depressed at will. In place of the ordinary teeth, each maxilla
carries a " poison-fang," in the form of a long, conical, curved
fang, which is concealed in a fold of the gum when not in use,
and has numerous germs or reserve-fangs behind it (fig. 1 66, B).
Each tooth is perforated by a tube, opening by a distinct aperture at the apex of the tooth, and conveying the duct of the
so-called poison-gland. (In reality the poison-duct of the fang
is formed'by an inflection of the tooth upon itself, and not by
its actual perforation.)  This is a gland, probably produced by
a modification of one of the buccal salivary glands, situated
behind and under the eye on each side, and secreting the fluid
which renders the bite of these snakes dangerous or fatal.
When the animal strikes its prey, the poison-fangs are erected,
and the poison is forced through the tube which perforates
each, partly by the contractions of the muscular walls of the
gland, and partly by the muscles of the jaws. In most poisonous snakes the superior maxillae carry no other teeth except
the poison-fangs and their rudimentary successors, but in some
cases there are a few teeth behind the fangs; whilst the palatine teeth are always present, as in the harmless species. In
some other venomous Snakes, again (e.g., Najfa and the HJydrophidce), the jaws and teeth agree in most characters with those
of the non-venomous Snakes, but the first maxillary teeth are
larger than the others, and form canaliculated fangs. Lastly,
in a few forms the terminal maxillary teeth are deeply canaliculated, but are not connected with the duct of any poisongland.
Fourthlly, in all the Serpents the teeth are anchylosed to the
jaw, and are never sunk into distinct sockets or alveoli.
A good classification of the Ophidia is still a desideratum,
and probably, in the meanwhile, the one proposed by Dr Gray
is the best. This eminent naturalist divides the Snakes into
the two sub-orders of the Vzierina and Colubrina, the former
having only two perforated poison-fangs on the superior
maxillae, whilst these bones in the latter carry solid teeth,
either with or without additional canaliculated fangs.




432              MANUAL OF ZOOLOGY.
The sub-order Vziperina comprises the common Vipers
(IVzperide), and the Rattlesnakes (Crotalid&e), the former being
mostly confined to the Old World, whilst the latter are wholly
American. The common Viper (Pelias berus), occurs abundantly in England and Scotland, and is capable of inflicting
Fig. 67. —The N2Vaa Haje, a venomous Colubrine Snake.
a severe and even dangerous bite, though it is doubtful if
fatal effects ever follow except in the case of children or subjects previously debilitated.  The Rattlesnakes are exclusively
natives of America, and they are highly poisonous. The extremity of the tail in the true Rattlesnake (Crotazls horridus)
is furnished with a series of horny epidermic cells of an undulated pyramidal shape, articulated one within the other, constituting an appendage which is known as the "rattle." Before
striking its prey, the Rattlesnake throws itself into a coil, and
shakes its rattle, as it does also when alarmed. The head of
the Viperine Snakes (figs. i66, i68) is broad, somewhat triangular in shape, broadest at its middle, and showing a very
distinct line of demarcation between the head and neck. The
head, also, is usually covered with small scales, rarely interspersed with larger plates or "scuta" (fig. I68).  Other wellknown members of this group are the Death Adder (Acanthopjhis
tortor) of Australia, the Horned Viper (Cerastes) of Africa, and




OPHIDIA.                     433
the Puff Adder (Clotho arietans) of the Cape of Good Hope
The Cozubrina include for the most part harmless snakes, but
together with these are some of the most deadly of all the
venomous snakes.  In accordance with this they are often
divided into the three sections of the Innocua, Suspecta, and
Venenosa. In the first of these sections (Innocua), the superior
maxillae are provided with solid teeth only, and there are no
fangs. In this section are the common Ringed Snake of Britain and the Boas and Pythons of warm climates. The common Ringed Snake (Coluber natrix) of Britain is a perfectly
harmless animal which is commonly found in damp situations,
and which lives mainly upon frogs. Closely allied to this is
the Black Snake (Bascanion constrictor), which attains a length
of from three to five feet, but is perfectly harmless, so far as
man is concerned. The Boidce or Boas and Pythons are the
largest of all living snakes, attaining.a length of certainly over
twenty feet.  Their bite is perfectly harmless, but they are
nevertheless highly dangerous and destructive animals, owing
to their great size and enormous muscular power. They seize
their prey and coil themselves round it in numerous folds, by
tightening which they gradually reduce their victim to the condition of a shapeless bolus, fit to be swallowed. In this way a
good-sized Python or Boa will certainly dispose of an animal
as large as a sheep or goat, and it is asserted that even human
beings may be devoured in this way by large individuals of the
family. The Boas and Pythons occur in both the Old and New
World, the Pythons, however, all belonging to the Old World;
and they are amongst the most formidable of all living Ophidians.
They possess rudimentary hind-limbs terminating in horny anal
spurs, which co-operate with the prehensile tail in enabling the
animal to suspend itself from trees. In all, also, the dental
apparatus is extremely powerful, giving a firm hold for the constriction of the prey.
In the section Suspecta, in which there are canaliculated
fangs placed far back on the superior maxillae, with smaller
solid teeth in front of them, are certain unimportant snakes,
partly aquatic and partly terrestrial in their habits, and all belonging to the Old World.
In the group Venenosa, in which there are canaliculated
fangs placed in front of the superior maxillae with smaller solid
teeth behind them, are some of the most deadly of all living
serpents. One of the best known of these is the Hooded
Snake, or Cobra di Capel/o (Naja triz5udians), which is commonly found in Hindostan, and is the snake usually carried
about by the Indian snake-charmers. It varies from two to




434               MANUAL OF ZOOLOGY.
six feet in length, and the neck can be extensively dilated,
covering the head like a hood. A nearly-allied species is the
laia Haje (fig. I67) of Egypt.  Also in this section are the
venomous Water-snakes (Hydro phidc), which have a compressed tail, and are adapted for an aquatic life. They mostly
frequent the mouths of rivers in droves, and they swim with
great grace and rapidity.
A very good general character by which the Colubrine snakes
may be distinguished from the Viperine snakes, is in the shape
and armature of the head.  In the Viperina, as before said,
the head (figs. i66, i68) is triangular, broadest behind, and
separated from the neck by a more or less marked diminution
in the diameter of this latter part.  The scales, too, which
cover the head are of small size. In the Colubrine snakes, on
the other hand, the head is not markedly triangular, and gradually tapers off into the neck, whilst the upper surface of the
A  Bl|[ C
A
Fig. i68. —A, Head of Colubrine Snake (Coluber natrix); B, Head of Viperine Sna
(Pezias berus); C, Head of Blind-worm (Angzuisfragilis), one of the serpentiform
Lizards. (After Bell.)
head is usually covered with large shield-like plates or " scuta"
(fig. I68, A).
DISTRIBUTION OF OPHIDIA IN TIME.-The Ophidia are not
known to occur in any Palaeozoic or Mesozoic deposit. The
earliest-known traces of any serpent are in the Lower Kaino
zoic Rocks, the oldest being the Palzophis toliaypicus of the
London Clay of Sheppey.  The nearly-allied Palczophis typhAus
of the Eocene beds of Bracklesham appears to have been a
Boa-constrictor-like snake of about twenty feet in length.
C ther species of Paiaeophis have been described from the Tertiary




LACERTILIA AND CROCODILIA.              435
Rocks of the United States, and the genus Dinophis has been
formed for the reception of another gigantic constricting Serpent from the same formation. In some of the later deposits
have been found the poison-fangs of a venomous snake. Upon
the whole, however, the snakes must be lodked upon as a comparatively modern group, and not as one of any great geological
antiquity.
CHAPTER LXIV.
LACERTILIA ANTD  CROCODILIA.
ORDER III. LACERTILIA. —The third order of Reptiles is that
of the Lacerti/ia, conlprising all those animals which are commonly known as Lizards, together with some serpentiform animals such as the Blind-worms. The Lacertilia are distinguished
by the following characters:As a general rule, there are two pairs of well-developed
limbs, but there may be only one pair, or all the limbs may be
absent.  A scapular arch is always present, whatever the condition of the limbs may be. An exoskeleton, in the form of
horny scales like those of the Snakes, is almost always present.
The vertebrae of the dorsal region are proccelous or concave in
front, rarely amphiccelous or concave at both ends. There is
a single transverse process at each side, and the heads of the
ribs are simple and undivided. There is either no sacrum, or
the sacral vertebrae do not exceed two in number. The teeth
are not lodged in distinct sockets.  The eyes are generally
furnished with movable eyelids, and are always so in the completely snake-like forms.  The heart consists of two auricles
and a ventricle, the latter partially divided by an incomplete
partition. There is a urinary bladder, and the aperture of the
cloaca is transverse.
As a general rule, the animals included under this order
have four well-developed legs (fig. I69), and would therefore
be popu'arly called " Lizards."  In some (Chirotes)' there are
no hind-feet; in some (]Pipes) the fore-limbs are wanting; and
others (Aiguis,  Pscudolus,  and Amp/hisboe a) are entirely destitute of limbs, thus coming closely to resemble the true Snakes
or Ophidians in external appearance.   These serpentiform
Lizards, however, can be distinguished from the true Snakes,
amongst other characters, by the structure of the jaws. In the
Snakes, as before said, the two rami of the lower jaw are loosely
20




436             MANUAL OF ZOOLOGY.
united in front by ligaments and muscles, and are attached
behind to a movable quadrate bone, which is in turn connected
with a movable squamosal, this giving an enormous width of
gape to these animals. In the Lizards, however, even in those
Fig. I69.-Iguana.
most like the Snakes, the halves of the lower jaw are firmly
united to one another in front; and though the quadrate bone
is usually more or less movable, the jaws can in no case be
separated to anything like the extent that characterises the
Op1hidia.
Another good and still more obvious character is to be found
in the structure 6f the protective coverings of the eye.  In the
Snakes, eyelids are wanting, and the eye is simply covered by
a layer of epidermis, constituting the so-called "antocular
membrane." In almost all the Lizards, on the other hand, including all the completely snake-like forms, there are movable
eyelids, and in few cases is there any structure comparable to
the antocular membrane of the true Snakes. Lastly, the typical Lizards all possess a sternum or breast-bone, but this is
wanting in some of the snake-like forms, so that it cannot be
appealed to as a character by which the Lacerlilia can be
separated from the Ophidia.
The whole order of the Lacertilia is very often united with
the next group of the Crocodilia, under the name of Sauria.
The term  " Saurian," however, is an exceedingly convenient
one to designate all the Reptiles which approach the typical
Lizards in external configuration, whatever their exact nature
may be; and from this point of view it is often very useful as
applied to many fossil forms, the structure of which is only
imperfectly known.  It is therefore perhaps best to employ
this term merely in a loose general sense.
The Lacertilia are often divided into the two great groups of
the Fissilinguia and Bireviiznguia, according as the tongue is




LACERTILIA AND CROCODILIA.               437
bifid and protrusi~ble like that of the Ophidians, or is thick and
fleshy, and only protrusible when the mouth is open.  These
distinctions, however, are not of any very great value, and no
good general arrangement of the order has hitherto' been proposed.  Here, therefore, it will be sufficient to treat very
shortly of the more important families of the Lacertilians.
The first family of any importance is that of the Chalcidce or
Chalcidian Lizards, comprising a number of snake-like animals
which have long occupied a debatable position. In their serpentiform cylindrical formn these animals closely resemble the
true Ophidia, and this likeness is still further increased by the
absence or rudimentary condition of the limbs. The scapular
arch and sternum, however, are present in a rudimentary form,
and one or both pairs of limbs may be present. Another
character separating the Chalcidve from the true Snakes is the
structure of the lower jaw, the rami of which are united in
front by a symphysis so as greatly to restrict the gape. The
Chalcidian Lizards are entirely covered with similar scales
arranged in rings or whorls; the trunk passes into the tail
without any definite line of demarcation, and there is generally
a lateral longitudinal fold or groove.  In Chalcides the body
is long and snake-like, but all the limbs are present, though
these are small, and have often but a single well-developed
toe each. It is represented in both the East Indies and South
America. In Chirotes, of Mexico, only the fore-limbs are present, and in the African genus Bijpes only the hind-limbs are
present. In the Anzmhisbenxe of South America the tail is
very short, and the vent is placed nearly at the end of the
body, whilst there are no limbs. In the Glass Snake (Ohisaurus) of the United States there are also no limbs.
The next great family is that of the Scincirie, including a
number of small Lacertilians, some of which are completely
snake-like, whilst others possess two limbs, and others again
have the normal two pairs of limbs in a well-developed conditio4. All possess movable eyelids, and in all the conformation of the lower jaw is Lacertilian, and not Ophidian.  All
the Scincoidean Lizards have the body covered by similar
scales overlapping one another like the scales of fishes, whilst
the head is protected by larger plates.  The tongue is free,
fleshy, and slightly notched.  Of the snake-like forms of
this group, none is more familiarly known than the Blindworm  or Slow-worm  (Azlgluis fiag~i/is, fig. I70), which is
found over almost the whole of Europe, in western Asia,
and northern Africa, and which is one of the most abundant of the British Reptiles.  The Blind-worm possesses no




438              MANUAL OF ZOOLOGY.
external appearance of limbs, though the scapular and pelvic
arches are present in a rudimentary condition. Its appearance
is completely serpentiform, and it is vulgarly regarded as a dangerous and venomous animal, but quite erroneously, as it is
even unable to pierce the human skin. It is a perfectly harmles3 animal, living upon worms, insects, and snails, and hyberFig. x7o.-The Blind-worm (Anguisfragilis)-after Bell.
nating during the winter.  It derives its specific name of fiag.
i/is from the fact that when alarmed it stiffens its muscles to
such an extent that the tail can be readily broken off, as if it
were brittle.
Numerous other small Lizards are referable to the Scincicia,
but it is only necessary to mention the Skinks themselves
(Scincus), in which both pairs of limbs are present in a welldeveloped state. The Skinks are found in almost all the
warmer parts of the Old World, and closely-allied forms (such
as the West Indian " Galliwasp") are found in the New World.
The common Skink (fig. I7 1) is a native of Arabia and Africa.
It attains a length of eight or nine inches, and was formerly
used in various diseases as a remedy.
The next family is that of the Lacer/idce, comprising the
typical Lizards, in which there are always four well-developed
limbs, each terminated by five free toes of unequal lengths.
The body is covered with scales, which assume the form of




LACERTILIA AND CROCODILIA.                439
shields or " scuta" over the abdomen and on the head. The
tail is rounded. The tongue is slender, bifid, and protrusible.
The only truly British Lizards are the Sand-lizard (Lacerta
Fig. I7T.-The common Skink (Scincus offlcinalZs).
agiiis), and the Viviparous Lizard (Zootoca zvi7.lipara); and the
commonest form upon the Continent is the graceful little Green
Lizard (Lacer/a viridis), which also occurs in Jersey.  The
Lizards of the Old World are represented in America by the
Ameivw, some of which attain a length of several feet.
Very closely allied to the true Lizards are the Varanida? or
Monitors, which indeed are chiefly separated by the comparatively trivial fact that the abdomen and head are covered with
ordinary scales, and not with large "scuta." The tongue is
protrusible and fleshy, like that of the Snakes. The teeth are
lodged in a common alveolar groove, which has no internal
border; and there are no palatal teeth. The tail has a double
row of carinated scales, and is cylindrical in the terrestrial
forms, and compressed in those whose habits are aquatic. The
Monitors are exclusively found in the Old World,. and are the
largest of all the recent Lacerti/ia; the Varainus Niloticus of
Egypt attaining a length of six feet, and the Varanus bivittatus
of Java attaining to as much as eight feet. The Safe-guards
(Salvaltr) are the Monitory Lizards of the New World, and are
also of large size.
The Gecko/tide form a large family of Lizards, comprising a
great numlber of species, occurring in almost all parts of the




440              MANUAL OF ZOOLOGY.
world. The tongue is wide, flat, scarcely notched at its free
extremity, and hardly at all protrusible. The eyes are large,
with extremely short lids, the pupil mostly linear, but sometimes circular.  The teeth are numerous, small, compressed,
and implanted on the inner edge of the jaw. The nails are
mostly hooked and retractile, and the toes are furnished below
with imbricated plates. The animal is capable of running on
the smoothest surfaces, or suspending itself back-downwards.
They feed on insects, and are found in abundance in the warmner
parts of both the Old and New Worlds.
The Iguanidee constitute another large family of Lizards,
also belonging partly to the Old and partly to the New World.
The tongue is thick, fleshy, notched at its extremity only, and
not protrusible. Mostly there is a dorsal crest, and a goitre or
throat-pouch. The body is covered with imbricated scales.
Only one species of the family is European, but the group is
represented by numerous species in N. and S. America, Asia,
Africa, and Australia.  They are often divided into "groundiguanas," in which the body is flat and depressed, and "treeiguanas," in which the body is compressed. The members of
the genus Iguana itself (fig. I69) are confined to the New
World, and are distinguished by having the throat furnished
Fig. I72.-Head of a Chameleon (C. Petersii)-after Gray.
with a pendulous dewlap or fold of skin, the edge of which is
toothed.  The back and tail, too, are furnished with an erect
crest of pointed scales. The Iguana attains a length of from
four to five feet, and though not of a very inviting appearance,
is highly esteemed as food.  The Basilisks (Basiliscus) have
the top of the head furnished with a membranous sac, which
can be distended with air at will. The Agamidee agree with
the Iguanas in most respects, but have two rows of teeth on
the hinder margin of the palate, and the tail is covered with




LACERTILIA AND CROCODILIA.              441
imbricated scales. Good examples are the Tapayaxin (Agama
orbicularis) of South America, and the hideous laoloch horridus
of Australia. Here also belongs the curious little Frill Lizard
(Chlamydosaurus) of Australia, which has the neck furnished
on each side with a membranous plaited frill, which can be
erected at will. More remarkable than the true Iguanas is the
little Flying Dragon (Draco volans) of the East Indies and
Indian Archipelago. In this singular little Lizard there is a
broad membranous expansion on each side, formed by a fold
of the integument, supported upon the anterior false ribs, which
run straight out from the spinal column. By means of these
lateral expansions of the skin, the Draco volans can take long
flying leaps from tree to tree, and can pursue the insects on
which it feeds; but the lateral membranes simply act as parachutes, and there is no power of true flight, properly so called.
The last family of the living Lizards which requires notice
is that of the Chamceleontidce, containing the familiar little
Chameleo Africanus, which occurs abundantly in the north of
Africa and in Egypt, and is so well known for its power of
changing its colour under irritation or excitement.  In this
genus the eye (fig. 172) is of large size, and is covered by a
single circular lid, formed by a coalescence of the two lids,
and perforated centrally by a small aperture, by which the
rays of light reach the pupil. The Chameleon is naturally a
sluggish animal, but it catches its food, consisting of insects,
by darting out its long, fleshy, and glutinous tongue-an operation which it effects with the most extraordinary rapidity.
The tail in the Chameleons is round and prehensile, the body
compressed, and the skin like shagreen. The toes are adapted
for the arboreal life and scansorial habits of the animal, being
so arranged as to form two equal and opposable sets. The
lungs are excessively voluminous. The Chameleons are exceedingly sluggish and slow in their movements, and are confined to the warmer parts of the Old World.
DISTRIBUTION OF LACERTILIA IN TiME.-The geological
range of the true Lacertilia is not by any means very great,
nor, with a single exception, are their remains of much importance. The earliest traces of Lizards in the stratified series are
found in the fresh-water strata of the Purbeck beds at the
summit of the Jurassic series.  Several small Lizards occur
here, and have been described under the names of JVatletes,
Macellodon, Saurillus, and Ec/zinodon. The most remarkable
fossil Lizard, however, is the Miosasaurus of the Chalk. This
gigantic reptile occurs at the very summit of the Cretaceous
series, in what is known as the Maestricht Chalk. The skull




442              MANUAL OF ZOOLOGY.
is no less than five feet long; and as the tail and limbs were
formed for swimming, there can be little doubt but that Mosasaurus-like the living Amblyrhynchus —was aquatic in its
habits, and frequented the sea-shore. Several other Reptiles,
either belonging to the genus Aiosasaurus, or nearly allied to
it, have been described from  the Cretaceous and Tertiary
rocks of North America.  Recent researches on these Mosasauroid Reptiles by Professor Marsh of New  Haven have
shown that they possessed fin-like paddles like those of the
Ichthyosaur and Plesiosaur.
ORDER IV. CROCODILIA.-The last and highest order of
the living Retilia is that of the Crocodilit, including the living
Crocodiles, Alligators, and Gavials, and characterised by the
following peculiarities:The body is covered with an outer epidermic exoskeleton
composed of horny scales, and an inner dermal exoskeleton
consisting of squared bony plates or scutes, which may be confined to the dorsal surface alone, or may exist on the ventral
surface as well, and which are disposed on the back of the
neck into groups of different form  and number in different
species. The bones of the skull and face are firmly united to
gether, and the two halves or rami of the lower jaw are united
in front by a suture. There is a single row of teeth, which are
implanted in distinct sockets, and hollowed at the base for the
germs of the new teeth, by which they are successively pushed
out and replaced during the life of the animal. The centra of
the dorsal vertebrae in all living Crocodilia are proccelous, or
concave in front, but in the extinct forms they may be either
amphiccelous (concave at both ends) or opisthoccelous (concave behind). The vertebral ends of the anterior trunk-ribs
are bifurcate. There are two sacral vertebrae.  The cervical
vertebrae have small ribs (hence the difficulty experienced by
the animal in turning quickly); and there are generally false
abdominal ribs produced by the ossification of the tendinous
intersections of the recti muscles. There are no clavicles.
The heart consists of four completely distinct and separate
cavities, two auricles, and two ventricles, the ventricular septum-as in no other Reptiles-being complete. The right and
left aorta, however-or, in other words, the pulmonary artery
and systemic aorta-are connected together close to their origin
by a small aperture (forame;  Panizzce), so that the two sides
of the heart communicate with one another. The aperture of
the cloaca is longitudinal, and not transverse, as in the Lizards.
All the four limbs are present, the anterior ones being pentadactylous, the posterior tetradactylous. All are oviparous.




LACERTILIA  AND  CROCODILIA.                443
The chief points by which the Crocodiles are distinguished
firom their near allies, the Lacertilians, are the possession of
a partial bony dermal exoskeleton in addition to the ordinary
epidermic covering of scales, the lodgment of the teeth in
Fig. I73. —Crocodilia. Head and fore-part of the body of the common Crocodile
(Crocodilus vulgaris).
distinct sockets, and the fact that the mixture of venous and
arterial blood, which is so characteristic of Reptiles, takes
place, not in the heart itself, but in its immediate neighbourhood, by a communication between the pulmonary artery and
aorta directly after their origin.
The only other points about the Crocodiles which require
special notice are that the eyes are protected by movable eyelids; the ear is covered by a movable ear-lid; the nasal cavities
open in front by a single nostril, and are shut off from the
cavity of the mouth, but open far back into the cavity of the
pharynx; and lastly, the tongue is large and fleshy, and is immovably attached to the bottom of the mouth. (Hence the
belief of the ancients that the Crocodile had no tongue.) The
tail is long and compressed, with two rows oi keeled plates,
which unite about its middle to form a single crest, which is
continued to its extremity. The feet are palmate or semipalmate, and only the three inner toes on each foot possess
claws. The eyes possess three distinct lids, and there are two
glands under the throat secreting a musky substance.
The Crocckizlia abound in tlhe fresh waters of hot countries,
and are the largest of all living Reptiles, not uncommonly attaining a length of twenty feet or upwards. They are divided
by Owen into three sub-orders, according to the shape of the
dorsal vertebrae, termed the Procwlia, Anp/hicwxia, and Opisthoczwia.
Sub-order I. Procewlia.-In this sub-order are all the livilng
members of the Crocodilia distinguished by having the bodies
of the dorsal vertebrae concave in front (procelous). Three
distinct types may be distinguished amongst the living Crocw



444               MANUAL OF ZOOLOGY.
dilia.  The Gavial is distinguished by its elongated snout, at
the extremity of which the nostril is- placed, and by the fact
that the teeth are pretty nearly equal in size and similar in
Fig. 174.-Skull of young Cr-ocodiZlts biporcatzus (after Van der Hdven).
form  in the two jaws.  In the true Crocodiles (fig. 174) the
fourth tooth in the lower jaw is larger than the others, and
forms a canine tooth, which is received into a notch excavated
in the side of the alveolar border of the upper jaw. so that it is
visible externally when the mouth is closed. In the Caimans
or Alligators the same tooth in the lower jaw forms a canine,
but it is reteived into a pit in the palatal surface of the upper
jaw, where it is entirely concealed when the mouth is shut.
The Crocodiles have the hind-legs bordered by a toothed
fringe, and the toes completely united by membrane. They
are essentially natives of fresh water, but sometimes frequent
the mouths of rivers.  They occur chiefly in Asia and Africa,
but species are found in some of the West Indian Islands.
The Alligators have the hind-legs simply rounded, and the feet
not completely webbed. They are essentially aquatic, and are
voracious animals, living upon fish or Mammals.  The bestknown species are the Alligator of the Southern United States
(A. Mlississippieozsis), the Caiman (A. paiO(1ebrosus) of Surinam
and Guiana, and the "Jacare" or Spectacled Alligator (A.
scl/erops) of Brazil.  The Gavial (Gavialis Galgcticus) is a
native of India, and is the smallest of the living Crocodiles,
attaining a length of about ten feet.
True procoelian Crocodiles occur for the first time in the
Greensand (Cretaceous series) of North America. In Europe,
however, the earliest remains of proccelian Crocodiles are from
the Lower Tertiary rocks (Eocene). It is a curious fact that
in the Eocene rocks of the south-west of England, there occur
fossil remains of all the three living types of the Crocodilianamely, the Gavials, true Crocodiles, and Alligators; though
at the present day these forms are all geographically restricted
in their range, and are never associated together.




EXTINCT ORDERS OF REPTILES.               445
Sub-ortder 2. Anmpticewlia. —The Amphiccelian Crocodiles,
with biconcave vertebrae, are entirely extinct. They have but
a limited geological range, extending only from the Lias to
the Chalk inclusive, and being therefore strictly Mesozoic.7"
The biconcave vertebrae show a decided approach to the
structure of the backbone in fishes; and as the rocks in which
they occur are marine, there can be little doubt but that these
Crocodiles were, in the majority of cases at any rate, marine.
The most important genera belonging to this order are Tel/cosaurus, Sleneosaurus, Daakosaurus, Makrospondyhzs, and Szzcsaurus, the last being from  the fresh-water deposits of the
Wealden (Cretaceous).
Sub-order 3. Opisthoceia.-This sub-order, like the last, is
entirely extinct, and is exclusively Mesozoic, all the known
examples bccurring in the Liassic, Oolitic, and Cretaceous
rocks.  The most important genera are Streptosipondlyus and
Cetiosaurus.  The Cetiosaurus longuzs of the Upper Oolites
(Portland Stone) must have been the largest of all known Crocodilia, the vertebrae of the tail measuring as much as seven
inches in length, and more than seven inches across.
CHAPTER LXV.
EXTINCT ORDERS OF REPTILES.
IT remains now to consider briefly the leading characters of
five wholly extinct orders of Reptiles, the peculiarities of which
are very extraordinary, and are such as are exhibited by no
living forms.
ORDER V. ICHTHYOPTERYGIA, Owen (- Ich/lyosauria, Huxley).-The gigantic Saurians forming this order were distinguished by the following characters:The body was fish-like, without any distinct neck, and probably covered with a smooth or wrinkled skin, no horny or
bony exoskeleton having been ever discovered. The vertebrae
were numerous, deeply biconcave or amphiccelous, and having
the neural arches united to the centra by a distinct suture.
The anterior trunk-ribs possess bifurcate heads. There is no
sacrum, and no sternal ribs or sternum, but clavicles were pre*If the so-called " Thecodont" Reptiles, such as Thecodontosaurus
and Belodon, belong to this sub-order, then the Amphiccelian Cvocodilis
date from the age of the Triassic rocks.




446              MANUAL OF ZOOLOGY.
sent as well as an interclavicle (episternum); and false ribs
were developed in the walls of the abdomen. The skull had
enormous orbits separated by a septum, and an elongated
snout. The eyeball was protected by a ring of bony plates in
the sclerotic. The teeth were not lodged in distinct sockets,
but in a common alveolar groove. The fore and hind limbs
were converted into swimming-paddles, the ordinary number
of digits (five) remaining recognisable, but the phalanges being
greatly increased in number, and marginal ossicles being added
as well. A vertical caudal fin was in all probability present.
The order Ic//tyoplferygia includes only the gigantic and
fish-like Icht/iosauri (fig. r75), all exclusively Mesozoic, and
abounding in the Lias, Oolites, and Chalk, but especially characteristic of the Lias.  If, however, the Eosaunzrls Acadsiensis
(Marsh) of the Coal-measures of Nova Scotia be -rightly referred to this order, then the Ich/tyojpteryg'ia date from the Carboniferous period.  There is no doubt whatever but that the
Ichtit/zosauri were essentially marine animals, and they have
been often included with the next order (Saulrojteryg-ia) in a
common group, under the name of Enzaliosazlria or Sea
lizards.
In the biconcave vertebra and probable presence of a vertical tail - fin, the Ichthyosauzmrzs approaches the true fishes.
There is, however, no doubt as to the fact that the animal was
strictly an air-breather, and its reptilian characters cannot be
questioned, at the same time that the conformation of the limbs
is decidedly Cetacean in many respects.  Much has been
gathered from various sources as to the habits of the Ic/ht,zyosaurus, and its history is one of great interest. From the researches of Buckland, Conybeare, and Owen, the following
facts appear to be pretty well established: —That the Ich/ztyosauri kept chiefly to open waters may be inferred from their
Fig. 175. —chktzyosaurus communis.
strong and well-developed swimming-apparatus.  That they
occasionally had recourse to the shore, and crawled upon the
beach, may. be safely inferred from the presence of a strong
and well-developed bony arch, supporting the fore-limbs, and
closely resembling in structure the scapular arch of the Orn;i



EXTINCT ORDERS OF REPTILES.               447
thorhynchius or Duck-mole of Australia.  That they lived in
stormy seas, or were in the habit of diving to considerable
depths, is shown by the presence of a ring of bony plates in the
sclerotic, protecting the eye from injury or pressure. That
they possessed extraordinary powers of vision, especially in the
dusk, is certain from the size of the pupil, and from the enormous width of the orbits.  That they were carnivorous and
predatory in the highest degree is shown by the wide mouth,
the long jaws, and the numerous, powerful, and pointed teeth.
This is proved, also, by an examination of their petrified droppings, which are known to geologists as "coprolites," and
which contain numerous fragments of the scales and bones of
the Ganoid fishes which inhabited the same seas.
ORDER VI. SAUROPTERYGIA, Owen. (= Plesiosauria, Huxley).-This order of extinct reptiles, of which the well-known
PIesiosaurus may be taken as the type, is characterised by the
following peculiarities:
The body, as far as is known, was naked, and not furnished
with any horny or bony exoskeleton.  The bodies of the vertebrae were either flat or only slightly cupped at each end, and
the neural arches were anchylosed with the centra, and did not
remain distinct during life.  The transverse processes of the
vertebrae were long, and the anterior trunk-ribs had simple, not
bifurcate, heads. No sternum or sternal ribs are known to have
existed, but there were false abdominal ribs.  The neck in
most was greatly elongated, and composed of numerous vertebrae. The sacrum was composed of two vertebrae. The orbits
were of large size, and there was a long snout, as in the Icht/lyosauri, but there was no circle of bony plates in the sclerotic.
The limbs agree with those of the Ichthyosauri in being in the
form of swimming-paddles (fig. 176), but differ in not possessing
any supernumerary marginal ossicles. A pectoral arch, formed
of two clavicles and an interclavicle (episternum) appears to
have been sometimes, if not always, present. The teeth were
simple, and were inserted into distinct sockets, and not lodged
in a common groove.
The most familiar and typical member of the Saz7Mgoiptery-iaz
is the Piesiosauruzs (fig. I76), a gigantic marine reptile, chiefly
characteristic of the Lias and Oolites. As regards the habits
of the Plesiosaurus, Dr Conybeare arrives at the following conclusions:-" That it was aquatic is evident from the form of
its paddles; that it was marine is almost equally so from the
remains with which it is universally associated; that it may
have occasionally visited the shore, the resemblance of its extremities to those of the Turtles may lead us to conjecture; its




448             MANUAL OF ZOOLOGY.
movements, however, must have been very awkward on land;
and its long neck must have impeded its progress through the
water, presenting a striking contrast to the organisation which
so admirably fits the Ichthyosaurus to cut through the waves."
Fig. I76.-Plesiosaurus dolichodeirus.
As its respiratory organs were such that it must of necessity
have required to obtain air frequently, we may conclude "that
it swam upon or near the surface, arching back its long neck
like a swan, and occasionally darting it down at the fish which
happened to float within its reach.  It may, perhaps, have
lurked in shoal water along the coast, concealed amongst the
sea-weed; and raising its nostrils to a level with the surface
from a considerable depth, may have found a secure retreat
from the assaults of powerful enemies; while the length and
flexibility of its neck may have compensated for the want of
strength in'its jaws, and its incapacity for swift motion through
the water."
The geological range of the Plesiosaurus is from the Lias to
the Chalk inclusive, and specimens have been found indicating
a length of from eighteen to twenty feet.
Of the other genera of the Sauropterygia, Simosaurus and
Nothosaurus are from the Trias, and are chiefly characteristic
of its middle division, the Muschelkalk.  Placodus is another
genus, also from the Muschelkalk, and is charactcrised by the
extraordinary form of the teeth, which resembled those of
many fishes in forming broad crushing plates, constituting a
kind of pavement.
ORDER VII. ANOMODONTIA, Owen (= Dicynodonlia, Huxley).-The leading characters of this order are to be found in
the structure of the jaws, which appear to have been sheathed
in horn, so as to constitute a kind of beak, very like that of
the Chelonians.  In the genera Rhynchosaurus and Oudenodon,
both jaws seem to have been altogether destitute of teeth; but
in Dicynodon there were two long tusks, growing from persistent
pulps, placed one on each side in the upper jaw. The pectoral
and pelvic arches were very strong, and the limbs were well
developed and fitted for walking, and not for swimming.
Dicynodon and Oudenodon are known only from strata of




EXTINCT ORDERS OF REPTILES.                449
supposed Triassic age in South Africa and India, but R/.ynchosaurus occurs in the Trias of Europe.
ORDER VIII. PTEROSAURIA.-This order includes a group
of extraordinary flying Reptiles, all belonging to the Mesozoic
epoch, and exhibiting in many respects a very extraordinary
combination of characters. The most familiar members of the
order are the so-called " Pterodactyles," and the following are
the characters of the order:No exoskeleton is known to have existed. The dorsal vertebrae are proccelous, and the anterior trunk-ribs are doubleheaded.  There is a broad sternum  with a median ridge or
keel, and ossified sternal ribs. The jaws were always armed
Fig. i77.-Pferodactylus brevirostris. Skeleton and restoration.
with teeth, and these were implanted in distinct sockets.  In
some forms (Raamnphorynchltus) there appear to have been no
teeth in the anterior portion of the jaws, and these parts seem
to have been sheathed in horn, so as to constitute a kind of
beak. A ring of bony plates occurs in the sclerotic coat of
the eye. The pectoral arch consists of a scapula and distinct
coracoid bone, articulating with the sternum as in Birds, but
no clavicles have hitherto been discovered.  The fore-limb
(fi g. I77) consists of a humerus, ulna and radius, carpus, and
hand of four fingers, of which the inner three are short and unguiculate, whilst the. outermost is }clawless and is enormously
elongated.  Between this immensely- lengthened finger, the
side of the body, and the comparatively small hind-limb, there
must have been supported an expanded flying-membrane or
" patagium," which the animal must have been able to employ
as a wing, much as the Bats of the present day. Lastly, most
of the bones were " pneumatic "-that is to say, were hollow
and filled with air.




450             MANUAL OF ZOOLOGY.
By the presence of teeth in distinct sockets, and, as will
be seen hereafter, especially in the structure of the limbs, the
Pterodactyles differed from all known Birds, and there can be
little question as to their being genuine Reptiles.  The only
Reptile, however, now existing, which possesses any power of
sustaining itself in the air, is the little Draco volans, but this
can only take extended leaps from tree to tree, and cannot
be said to have any power of flight properly so called. That
the Pterodactyles, on the other hand, possessed the power of
genuine flight, is shown by the presence of a median keel upon
the sternum, proving the existence of unusually - developed
pectoral muscles; by the articulation of the coracoid bones
with the top of the sternum, providing a fixed point or fulcrum
for the action of the pectoral muscles; and, lastly, by the
existence of air-cavities in the bones, giving the animal the
necessary degree of lightness.  The apparatus, however, of
flight was not a " wing," as in Birds, but a flying-membrane,
very similar in its mode of action to the patagium of the Mammalian order of the Bats. The patagium of the Bats, however,
differs from that of the Pterodactyles in being supported by
the greatly-elongated fingers, whereas in the latter it is only
the outermost finger which is thus lengthened out. The difficulty as to the position of the Pterosauria is evaded by Mr
Seeley by placing them in a distinct class, which he terms
Ornithosauria, and which he regards as most nearly related to,
but coequal with, the class Aves.
The Pterosauria are exclusively Mesozoic, being found from
the Lower Lias to the Middle Chalk inclusive, the Lithographic
Slate of Solenhofen (Upper Oolite) being particularly rich in
their remains. Most of them appear to have attained no very
great size, but the remains of a species from the Cretaceous
rocks have been considered to indicate an animal with more
than twenty feet expanse of wing, counting from tip to tip.
In the genus Pterodtacty/ls proper, the jaws are provided
with teeth to their extremities, all the teeth being long and
slender.
In D)imo/phodon, the anterior teeth are large and pointed,
the posterior teeth small and lancet-shaped.
In lRahpalor/ihynchals, the anterior portion of both jaws is
edentulous, and may have formed a horny beak, but teeth
are present in the hinder portion of the jaws.
ORDER IX.-DINOSAURIA.-The last order of extinct Reptiles
is that of the Diniosauria, comprising a group of very remarkable
Reptiles, which show many points of decided affinity to the
Birds on the one hand, and to the so-called Pachydermatous




EXTINCT ORDERS OF REPTILES.               45 
Mammals on the other.  Most of the Dinosauria were of
gigantic size, and the order is defined by the following
characters:The skin was sometimes naked, sometimes furnished with a
well-developed exoskeleton, consisting of bony shields, much
resembling those of the Crocodiles. A few of the anterior vertebre were opisthoccelous, the remainder having flat or slightly
biconcave bodies. The anterior trunk-ribs were double-headed.
The teeth were confined to the jaws and implanted in distinct
sockets. There were always two pairs of limbs, and these were
strong, furnished with claws, and adapted for terrestrial progression.  In some cases the fore-limbs were very small in
proportion to the size of the hind-limbs. No clavicles have
been discovered.
The most familiar examples of the Dinosauria are Megalosaurus and Iguanodon.
Mfegalosaurus is a gigantic Oolitic Reptile, which occurs also
in the Cretaceous series (Weald Clay). Its length has been
estimated at between forty and fifty feet, the femur and tibia
each measuring about three feet in length. As the head of
the femur is set on nearly at right angles with the shaft, whilst
all the long bones contain large medullary cavities, there can
be no doubt but that Mieegalosairus was terrestrial in its habits.
That is was carnivorous and destructive in the highest degree is
shown by the powerful, pointed, and trenchant teeth.
The Iguanodon is mainly, if not exclusively, Cretaceous,
being especially characteristic of the great delta-deposit of the
Wealden. The length of the Iguanodon has been estimated as
being probably from fifty to sixty feet, and from the close resemblance of its teeth to those of the living Iguanas, there is
little doubt that it was herbivorous and not carnivorous. The
femur of a large Iguanodon measures from four to five feet in
length, with a circumference of twenty-two inches in its smallest
part. From the disproportionately small size of the fore-limbs,
and from the occurrence of pairs of gigantic three-toed footsteps in the same beds, it has been concluded, with much probability, that Iguanodon, in spite of its enormous bulk, must
have walked temporarily or permanently upon its hind-legs,
thus coming to present a most marked and striking affinity to
the Birds.
The most remarkable, however, of the Dinosauria, is the
little Conmpsognat/us longijzes from  the Lithographic Slate of
Solenhofen, referred to this order by Professor Huxley. This
Reptile is not remarkable for its size, which does not seem to
have been much more than two feet, but for the remarkable




452             MANUAL OF ZOOLOGY.
affinities which it exhibits to the true Birds.  The head of
Compsognat/hus was furnished with toothed jaws, and supported
upon a long and slender neck.  The fore-limbs were very
short, but the hind-limbs were long and like those of Birds.
Theproximal portion of the tarsus resembled that of Birds in
being anchylosed to the lower end of the tibia; but the distal
portion of the tarsus —unlike that of Birds-was free, and was
I')t anchylosed with the metatarsus.  Huxley concludes that
" it is impossible to look at the conformation of this strange
Reptile, and to doubt that it hopped or walked in an erect or
semi-erect position, after the manner of a bird, to which its
long neck, slight head, and small anterior limbs must have
given it an extraordinary resemblance."




DIVISION II. SA UROPSIDA.
CHAPTER LXVI.
CLASS  IV. —A VES.
THE fourth class of the Verteblrala is that of Aves, or Birds.
The Birds may be shortly defined as being "oviparous Vertebrates with warm blood, a double circulation, and a covering
of feathers" (Owen). More minutely, however, the Birds are
defined by the possession of the following characters:The embryo possesses an amnion and allantois, and branchiae
or gills are never developed at any time of life upon the visceral
arches. The skull articulates with the vertebral column by a
single occipital condyle. Each half or ramus of the lower jaw
consists of a number of pieces, which are separate from one
another in the embryo; and the jaw is united with the skull,
not directly, but by the intervention of a quadrate bone (as in
the Reptiles).  The fore-limb in no existing birds possesses
more than three fingers or digits, and the metacarpal bones
are anchylosed together. In all living birds the fore-limbs are
useless as regards prehension, and in most they are organs of
flight. The hind-limbs in all birds have the ankle-joint placed
in the middle of the tarsus, the proximal portion of the tarsus
coalescing with the tibia, and the distal portion of the tarsus
being anchylosed with the metatarsus to constitute a single bone
known as the "tarso-metatarsus."
The heart consists of four chambers, two auricles, and two
ventricles; and not only are the right and left sides of the
heart completely separated from one another, but there is no
communication between the pulmonaryand systemiccirculations,
as there is in Reptiles. There is only one aortic arch, the right.
The blood is hot, having an average temperature of as much as
Io3~ to I04~. The blood-corpuscles are oval and nucleated.
The respiratory organs are in the form of spongy cellular
lungs, which are not freely suspended in pleural sacs; and
the bronchi open on their surface into a number of air-sacs,
placed in different parts of the body.




454             MANUAL OF ZOOLOGY.
All birds are oviparous, none bringing forth their young
alive, or being even ovo-viviparous. All birds are, lastly, provided with an epidermic covering, so modified as to constitute
what are known as fealhlers.
Professor Huxley's account of the method in which feathers
are produced is so remarkably clear, that no apology is necessary for quoting it in its entirety.  Feathers "are evolved
within sacs from the surface of conical papillae of the dermis.
The external surface of the dermal papilla, whence a feather is
to be developed, is provided upon its dorsal surface with a
median groove, which becomes shallower towards the apex
of the papilla. From this median groove lateral furrows proceed at an open angle, and passing round upon the under
surface of the papilla, become shallower, until, in the middle
line, opposite the dorsal median groove, they become obsolete.  Minor grooves run at right angles to the lateral furrows.
Hence the surface of the papilla has the character of a kind of
mould, and if it were repeatedly dipped in such a substance as
a solution of gelatine, and withdrawn to cool until its whole
surface was covered with an even coat of that substance, it is
clear that the gelatinous coat would be thickest at the basal
or anterior end of the median groove, at the median ends of
the lateral furrows, and at those ends of the minor grooves
which open into them; whilst it would be very thin at the
api.ces of the median and lateral grooves, and between the
ends of the nlinor grooves. If, therefore, the hollow cone of
gelatine, removed from its mould, were stretched from within,
or if its thinnest parts became weak by drying, it would tend
to give way, along the inferior median line, opposite the rodlike cast of the median groove, and between the ends of the
casts of the lateral furrows, as well as between each of the
minor grooves, and the hollow cone would expand into a flat
feather-like structure, with a median shaft, as a'vane' formed
of'barbs' and'barbules.'  In point of fact, in the development of a feather, such a cast of the dermal papilla is formed,
though not in gelatine, but in the horny epidermic layer developed upon the mould, and, as this is thrust outwards, it
opens out in the manner just described. After a certain
period of growth the papilla of the feather ceases to be
grooved, and a contin ous horny cylinder is formed, which
constitutes the'quill."
A typical feather (fig. 178) consists of the following parts:
-i. The "quill " or "barrel" (a), which forms the basal
portion of the feather, by which it is inserted in the skin on its
own dermal papilla.  It is the latest-formed portion of the fea



CHARACTERS OF AVES.                      45 5
ther, and consists of a hollow horny cylinder.  2. The " shaft"
(b), which is simply a continuation of the quill, and which forms
the central axis of the feather.
The inferior surface of the shaft
always exhibits a strong longitudinal groove, and it is composed
of a horny external sheath, containing a white spongy substance,
very like the pith of a plant.  3.
The shaft carries the lateral expansions or "webs" of the feather, collectively constituting the
"vane."  Each web is composed
of a number of small branches,
which form-an open angle with
the shaft, and which are known
as the " barbs" (c). The margins
of each barb are, in turn, furnished with a series of still smaller
branches, which are known as the
"barbules."  As a general rule,
the extremities of the barbules are.
hooked, so that those springing
from  the one side of each barb
interlock, with  those  springing
from  the opposite side  of the
next barb.  In this way the barbs
are kept in apposition with one
another over a greater or less                "c
portion of the entire web.  More
or less of the barbs in the lower 
portion of the feather are, however, disunited, and not connected
by their barbules; and these constitute what is known as the
" down.:'   In  the  Ostriches,
Emeus, and some others, all the
barbs of the feathers are disconnected, giving to the plumage of  Fig. 78. —Quill-feather (8?entosis).
these  birds  its  peculiarly  soft    a Quill or barrel; b Shaft; c c
character..  ^At the point w e    "'Webs, composed of the barbs, and
character.   At the point where   together forming the " vane."
the shaft joins the quill there is
very generally found a small feather, known as the " accessory
plume," or "plumule."   This is usually much the same in
structure as the main feather, but considerably smaller. It




456              MANUAL OF ZOOLOGY.
may, however, be as large as the original feather, or it may be
reduced to nothing more than a tuft of down.
The feathers vary in different parts of the bird, and are
generally divided into those which cover the body-" clothing
feathers," and those which occur in the wings and tail-" quillfeathers." As regards the great quill-feathers of the wings, the
longest are those which arise from the bones of the hand, and
they are called the " primaries." Those which arise from the
distal end of the fore-arm (radius and ulna) are termed the
"secondaries," and those which are attached to the proximal
end of the fore-arm are the " tertiaries."  The feathers which
lie over the humerus and scapula are the " scapulars." The
rudimentary "thumb" also carries some quills, which form
what is known as the "alula," or "bastard-wing."  The smaller
feathers, which cover the bases of the quill-feathers above and
below, are the "wing-coverts" — "greater," "lesser," and
"under."   The great quill-feathers of the tail (" rectrices")
form a kind of fan, of great use in steering the bird in flight;
and their bases are covered by a series of feathers which constitute the " tail-coverts."
The entire skeleton of the Birds is singularly compact, and at
the same time singularly light. The compactness is due to the
presence of an unusual amount of phosphate of lime; and the
lightness, to the absence in many of the bones of the ordinary
marrow, and its replacement by air.
As regards the vertebral column, birds exhibit some very interesting peculiarities.  The cervical region of the spine is
unusually long and flexible, since the fore-limbs are useless as
organs of prehension-and all acts of prehension must be exercised either by the beak or by the hind-feet, or by both acting
in conjunction.  In all birds alike, the neck is sufficiently long
and flexible to allow of the application of the beak to an oilgland placed at the base of the tail, this act being necessary
for the dug performance of the operation of " preening" —that
is, of lubricating and cleaning the plumage. The number of
vertebrae in the neck varies from nine to twenty-four, and their
structure is alway such as to allow of considerable.freedom of
motion one upon the other.  The dorsal vertebra vary from
six to ten in number, and of these the anterior four or five are
generally anchylosed with one another, so as to give a base of
resistance to the wings. In the Cursorial Birds, however (such
as the Ostrich and Emeu), and in some others (such as the
Penguin), in which the power of flight is wanting, the dorsal
vertebrae are all more or less freely movable one upon another.
There are no lumbar vertebrae, but all the vertebrae. between




CHARACTERS OF AVES.                  457
the last dorsal and the first caudal (varying from  nine to
twenty) are anchylosed together to form a bone which is ordinarily known as the " sacrum." To this, in turn, the iliac bones
are anchylosed along their whole length, giving perfect immobility to this region of the spine and to the pelvis.
The coccygeal or caudal vertebrae vary in number from
eight to ten, and are movable upon one another. The most
noticeable feature about this part of the spinal column is what
is known as the " ploughshare-bone." This is the last joint of
the tail, and is a long, slender, ploughshare-shaped bone, destitute of lateral processes, and without any medullary canal
(fig. I82, B).  In reality it consists of two or more of the
caudal vertebrae, completely anchylosed, and fused into a
single mass. It is usually set on to the extremity of the spine
at an angle more or less nearly perpendicular to the axis of
the body; and it affords a firm basis for the support of the
great quill-feathers of the tail (" rectrices "). It also supports
the coccygeal oil-glands, and can be raised at pleasure, so as
to meet the bill, when the operation of preening is in progress. In the Cursorial Birds, which do not fly, the terminal
joint of the tail is not ploughshare-shaped.  In the extraordinary Mesozoic bird, the Archkopteryx macrura, there is no
ploughshare-bone, and the tail consists of twenty separate
vertebrae, all distinct from one another, and each carrying
a pair of quill-feathers, one on each side (fig. 20I). As the
vertebrae of the ploughshare-bone are distinct from one another
in the embryos of existing birds, the tail of the Archceop/te-yx is
to be regarded as a case of the permanent retention in. the
adult of an embryonic character. In the increased number of
caudal vertebrae, however, and in. some other characters, the
tail of the ArchaZoeteryx makes a decided approach to the true
Reptiles.
The various bones which compose the skull of Birds are
amalgamated in the adult so as to form a single piece, and the
sutures even are obliterated, the lower jaw alone remaining
movable. The occipital bone carries a single occipital condyle
only, and this is hemispherical or nearly globular in shape. The
"beak" (fig. I79), which forms such a conspicuous feature in all
birds, consists of an upper and lower half, or a " superior" and
" inferior mandible." The upper mandible is composed almost
entirely of the greatly elongated intermaxillary bones, flanked
by the comparatively small superior maxillae. The inferior
mandible is primitively composed of twelve pieces, six on each
side; but in the adult these are all indistinguishably amalgamated with one another, and the lower jaw forms a single




458               MANUAL OF ZOOLOGY.
piece. As in the Reptiles, the lower jaw articulates with the
skull, not directly, but through the intervention of a distinct
bone-the quadrate bone or tympanic bone-which always reFig. I79.-Skull of Spur-winged Goose (PFcctro)teruls oallmzbelsis).
mains permanently movable, and is never anchylosed with the
skull. In no bird are teeth ever developed in either jaw, but
both mandibles are encased in horn, forming the beak, and
the margins of the bill are sometimes serrated. The quadrate
bone (os carre of the French) is in contact at one end with an
elongated bone (jugal bone), the other end of which comes
against the palate. By the depression of the lower jaw, assisted
by proper muscles, the quadrate bone is brought forward, and
the jugal bone is thus made to elevate the palate and upper
jaw. With one or two exceptions, the upper-mandible is thus
movable in all birds.
The thoracic cavity is bounded by the dorsal vertebrae,
which are usually, as before said, anchylosed to one another to
a greater or less extent. Laterally, the thorax is bounded by
the ribs, which vary in number from six to ten pairs.  In most
birds each rib carries a peculiar process-the "uncinate process"-which arises from its posterior margin, is directed upwaLrds and backwards, and passes over the rib next in succession behind, where it is bound down by ligament. The first
and last dorsal ribs carry no uncinate processes, and in some
cases the processes continue throughout life as separate pieces
(fig. I8o, B). Anteriorly, the ribs articulate with a series of
straight bones, which are called the "sternal ribs," but which
in reality are to be looked upon as the ossified "costal cartilages." These sternal ribs (fig. i8o, B) are in turn movably
articulated to the sternum in front, and " they are the centres
upon which the respiratory movements hinge" (Owen). In
front the thoracic cavity is completed by an enormously-expanded sternum or breast-bone, which in some birds of great




CHARACTERS OF AVES.                  459
powers of flight extends over the abdominal cavity as well, in
some cases even reaching the pelvis. The sternum of all
birds which fly, is characterised by the presence of a greatlydeveloped median ridge or keel (fig. I8o, A), to which are attached the great pectoral muscles which move the wings. As a
general rule, the size of this sternal crest allows a very tolerable
estimate to be formed of the flying powers of the bird to which
it may have belonged; and in the Ostriches and other birds
which do not fly,. there is no sternal keel. At its anterior
angles the sternum exhibits two pits for the attachment of the
coracoid bones.
The scapular or pectoral arch consists of the shoulder-blade
or scapula, the collar-bone or clavicle, and the coracoid bone,
on each side.  The scapula, as a rule (fig. I8o, A, s s), is a
C    C




460             MANUAL OF ZOOLOGY.
they are distinct bones, and are not anchylosed with the scapula. The coracoid bone on each side is always the strongest
of the bones forming the scapular arch. Superiorly it articulates with the clavicle and scapula, and forms part of the glenoid cavity for the humerus.  Inferiorly each coracoid bone
articulates with the upper angle of the sternum. The position
of the coracoids is more or less nearly vertical, so that they
form fixed points for the action of the wings in their downward stroke. The clavicles (fig 80o, A, c) are rarely rudimentary or absent, and are in some few cases separate bones. In
the great majority, however, of birds, the clavicles are anchylosed together at their anterior extremities, so as to form a
single bone, somewhat V-shaped, popularly known as the
"merry-thought," and technically called the "furculum " ("fourchette " of the French). The outer extremities of the furculum
articulate with the scapula and coracoid; and the anchylosed
angle is commonly united by ligament to the top of the sternum. The function of the clavicular or furcular arch is "to
oppose the forces which tend to'press the humeri inwards
towards the mesial plane, during the downward stroke of the
wing" (Owen). Consequently the clavicles are stronger, and
their angle of union is more open, in proportion to the powers
of flight possessed by each bird. The furculum is rudimentary
in the Ostrich, Emeu, and Cassowary.
We have next to consider the structure of the bones which
compose the fore-limb or "wing" of the bird; and as this
organ is the one which chiefly conditions the peculiar life of
the bird, it is in it that we find some of the most characteristic
points of structure in the whole skeleton.  Though considerably modified to suit its function as an organ of aerial progression, the wing of the bird is readily seen to be homologous
with the arm of a man or the fore-limb of a Mammal (fig. I80,
A, and fig. i8i).  The upper arm (brachium) is supported by
a single bone, the humerus, which is short and strong, and
articulates above with the articular cavity formed partly by
the scapula and partly by the coracoid (fig. I8T, h).  The
humerus is succeeded distally by the fore-arm (antibrachium)
constituted by the normal two bones, the radius and ulna
(fig. I8I, r, i), of which the radius is much the smaller and
more slender, and the ulna much the larger and stronger.
The ulna and radius are followed inferiorly by the bones of
the wrist or carpus; but these are reduced in number to ttwo
small bones, "so wedged in between the antibrachium and
metacarpus as to limit the motions of the hand to those of
abduction and adduction necessary for the folding up and ex



CHARACTERS OF AVES.                     46I
pansion of the wing; the hand is thus fixed in a state of pronation; all power of flexion, extension, or of rotation, is
removed from the wrist-joint, so that the wing strikes firmly,
and with the full force of the contraction of the depressor
muscles, upon the resisting air" (Owen).  One other bone
frig. i8I.-Fore-limb of the Jer-falcon. h Humerus; r Radius; u Ulna; t "Thumb;"
m Metacarpals, anchylosed at their extremities; p f Phalanges of fingers.
of the normal carpus (namely, the "os magnum ") is present,
but this is anchylosed with one of the metacarpals. There
are thus really three carpal bones, though only two appear
to be present. The carpus is followed by the metacarpus,
the condition of which agrees with that of the carpal bones.
The two outermost of the normal five metacarpals are absent,
and the remaining three are anchylosed-together with the
os magnum-so as to form a single bone (fig. I8i, nm).  This
bone, however, appears externally as if formed of two metacarpals united to one another at their extremities, but free
in their median portion. The metacarpal bone which corresponds to the radius is always the larger of the two (as
being really composed of two metacarpals), and it carries
the digit which has the greatest number of phalanges. This
digit corresponds with the "index" finger, and it is com



462              MANUAL OF ZOOLOGY.
posed of two, or sometimes three, phalanges (fig. 18i, p).  At
the proximal end of this metacarpal, at its outer side, there is
generally attached a single phalanx, constituting the so-called
"thumb" (fig. I8i, t), which carries the "bastard-wing." The
digit which is attached to the ulnar metacarpal corresponds to
the "ring finger," and never consists of more than a single
phalanx (fig. 8 I).
As regards the structure of the posterior extremity or hindlimb, the pieces which compose the innominate bones (namely,
the ilium, ischium, and pubes) are always anchylosed to one
another; and the two innominate bones are also always anchylosed, by the medium of the greatly-elongated ilia, to the
sacral region of the spine. In no living bird, however, with
the single exception of the Ostrich, are the innominate bones
united in the middle line in front by a symphysis pubis. The
stability of the pelvic arch, necessary in animals which support the weight of the body on the hind-limbs alone, is amply
secured in all ordinary cases by the anchylosis of the ilia with
the sacrum.
As in the higher Vertebrates, the lower limb (fig. I82, A)
consists of a femur, a tibia and fibula, a tarsus, metatarsus,
and phalanges; but some of these parts are considerably obscured by anchylosis. The femur or thigh-bone (fig. i82, A,f)
is generally very short, comparatively speaking. The chief
bone of the leg is the tibia (t), to which a thin and tapering
fibula (r) is anchylosed. The upper end of the fibula, however, articulates with the external condyle of the femur. The
ankle-joint is placed, as in Reptiles, between the proximal and
distal portions of the tarsus. The proximal portion of the
tarsus is undistinguishably amalgamated with the lower end of
the tibia....The distal portion of the tarsus is anchylosed with
the whole of the metatarsus to constitute the most characteristic
bone in the leg of the Bird-the "tarso-metatarsus" (as).  In
most of the long-legged birds, such as the waders, the disproportionate length of the leg it given by an extraordinary elongation of the tarso-metatarsus.
The tarso-metatarsus is followed inferiorly by the digits of
the foot. In most birds the foot consists of three toes directed
forwards and one backwards-four toes in all.  In no wild
bird are there more than four toes, but often there are only
three, and in the Ostrich the number is reduced to two. In
all birds which have three anterior and one posterior toe, it is
the posterior thumb or kal/ux (that is to say, the innermost
digit of the hind-limb) which is directed backwards; and it
invariably consists of tzoo phalanges only.  The most internal




CHARACTERS OF AVES.                           463
of the three toes which are directed forwards, consists of three
phalanges; the next has four phalanges; and the outermost or
"little" toe is made up of five phalanges (fig. I82, A).  This
f<
Fig. 182.-A, Hind-limb of the Loon (Coljymbs glacialis)-after Owen: i Innominato
bone; f Thigh-bone or femur; t Tibia, with the proximal portion of the tarsus anchylosed to its lower end; r Fibula; m Tarso-metatarsus, consisting of the distal
portion of the tarsus anchylosed with the metatarsus; t f Phalanges of the toes; B,
Tail of the Golden Eagle; s Ploughshare-bone, carrying the great tail-feathers.
increase in an arithmetical ratio of the phalanges of the toes,
in proceeding from the inner to the outer side of the foot, obtains in  almost all birds, and  enables us readily to detect
which digit is suppressed, when the normal four are not all
present. Variations of different kinds exist, however, in the
number and disposition of the toes. In many birds-such as the
Parrots-the outermost toe is turned backwards, so that there
are two toes in front and two behind. In others, again, the
outer toe is normally directed forwards, but can be turned
backwards at the will of the animal.  In the Swifts, on  the
other hand, all four toes are present, but they are all turned
forwards. In many cases-especially amongst the Natatorial




464              MANUAL OF ZOOLOGY.
birds-the hallux is wholly wanting, or is rudimentary. In the
Emeu, Cassowary, Bustards, and other genera, the hallux is
invariably absent, and the foot is three-toed. In the Ostrich
both the hallux and the next toe (" index ") are wanting, and
the foot consists simply of two toes, these being the outer toe
and Mie one next to it. The toes are mechanically flexed
during the sleep of the Bird, in virtue of an arrangement by
which, whilst all the flexor tendons pass behind the heed, one
of them runs in front of the knee. As the muscles, therefore,
are relaxed during sleep, and the weight of the body tends to
flex the knee, the tendon of this flexor is thereby put on the
stretch, and the toes are again bent involuntarily.
The digestive system of birds comprises the beak, tongue,
gullet, stomach, intestines, and cloaca. Teeth are invariably
wanting in birds, and the jaws are encased in. horn, constituting the bill. The form of the bill varies enormously in different birds, and it is employed for holding and tearing the prey,
for prehensile purposes, for climbing, and in some birds as an
organ of touch. In these last-mentioned cases the bill is
more or less soft, and is supplied with filaments of the fifth
nerve.  In many birds, too, in which the bill is not soft, the
base of the upper mandible is surrounded by a circle of naked
skin, constituting what is called the " cere," and this, no doubt,
serves also as a tactile organ.
The tongue of birds can hardly be looked upon as an organ
of taste, since it is generally cased in horn like the mandibles.
It is, in fact, principally employed as an organ of prehension;
but in some cases-as in the Parrots-it is soft and fleshy, and
then, doubtless, is to some extent connected with the sense of
taste. It is essentially composed of a prolongation of the
hyoid bone (the glosso-hyal), which is sheathed in horn, and is
variously serrated or fringed.
Salivary glands are invariably present, but they are rarely
of large size, and they have often a very simple structure.
In accordance with the structure of the neck, the gullet in
birds is usually of great length, and it is generally very dilatable.
In the carnivorous, or Raptorial, and in the granivorous birds,
the gullet (fig. 183, o), is dilated into a pouch, which is situated
at the lower part of the neck, just in front of the merry-thougl-ht.
This is what is known as the " crop" or " ingluvies" (c), and
it may be either a mere dilatation of the tube of the gullet, or
it may be a single or double pouch.  The food is detained in
the crop for a longer or shorter time, according to its nature,
before it is subjected to the action of the proper digestive
organs.  The esophagus, after leaving the crop, shortly opens




CHARACTERS OF AVES.                     465
into a second cavity, which is known as the "proventriculus"
or " ventriculus succenturiatus" (p). This is the true digestive
cavity, and its mucous membrane is richly supplied with gastric
sm                            /
Fig. 83.-Digestive System of the common Fowl (after Owen). o Gullet;  CrT;
s Proventriculus; g' Gizzard; sm Small ibtestine; k Intestinal cawca; I Large intestine; cl Cloaca.
follicles which secrete the gastric juice.  The proventriculus,
however, corresponds, not with the whole stomach of the
Mammals, but only with its cardiac portion; and it opens into
a second, muscular cavity, which corresponds to the pyloric
division" of the Mammalian stomach. The gizzard (gf) is situated below the liver, and forms in all birds an elongated sac,
having two apertures above, of which one conducts into the
duodenum or commencement of the small intestine, whilst the
other communicates with the proventriculus. The two chief
forms of gizzard are exhibited respectively by the Raptorial
birds, which feed on easily-digested animal food, and the
Rasores and some of the N/latores, which feed on hardlydigested grains. In the birds of Rapine the gizzard scarcely
deserves the name, being, as a rule, nothing more than a wide
membranous cavity with thin walls. In the granivorous birds,
whose hard food requires crushing, the gizzard is enormously
developed; its lining coat is formed of a thick, horny epithe



466              MANUAL OF ZOOLOGY.
lium, and its walls are extremely thick and muscular. This
constitutes a grinding apparatus, like the stones of a mill;
whilst the "crop" or cesophageal dilatation may be compared
to the "hopper" of a mill, since it supplies to the gizzard
"' small successive quantities of food as it is wanted " (Owen).
Supplementing the action of the muscular walls of the gizzard,
and acting in the place of teeth, are the small stones or pebbles, which, as is so well known, so many of the granivorous
birds are in the habit of swallowing with their food, or at other
times.  In fact there can be no doubt but that the gravel and
pebbles swallowed by these birds are absolutely essential to existence, since the gizzard, without this assistance, is unable
properly to triturate the food.
The intestinal canal extends from the gizzard to the cloaca,
and is, comparatively speaking, short.  The secretions of the
liver and pancreas are poured into the small intestine, as in
Mammals. The commencement of the large intestine is almost always furnished with two long " ceca " or blind tubes,
the length of which varies a good deal in different birds (fig.
L83, k). They are sometimes wanting; and their exact function is uncertain; though they are most probably connected
partly with digestion and partly with excretion.  The large
intestine is always very short-seldom  more than a tenth part
of the length of the body-and it terminates in the "cloaca "
(fig. I83, el).  This is a cavity which in all birds receives
the termination of the rectum, the ducts of the generative
organs and the ureters; and serves, therefore, for the exlpulsion of the faces, the generative products, and the urinary
secretion.
Respirtaioe z is effected in Birds more completely and actively
than in any other class of the Vertebrala, and as the result of
this, their average temperature is also higher.  This extensive
development of the respiratory process is conditioned by the
fact that, in addition to true lungs, air is admitted into a greater
or less number of the bones, and into a numler of cavities —
the so-called air-receptacles -which are distributed through
various parts of the body.  By this extensive penetration of
air into various parts of the body, the aeration of the blood is
effected not only in the lungs, but also over a greater or less
extent of the systemic circulation as well; and hence in Birds
this process attains its highest perfection.  The cavities of the
thorax and abdomen are not separated from one another by a
complete partition, the diaphragm  being only present in a
rudimentary form. The lungs are two in number, of a brightred colour, and spongy texture.  They are confined to the




CHARACTERS OF AVES.                        467
back of the thorax, extending along each side of the spine,
from the second dorsal vertebra to the kidney.  They differ
from the lungs of the Mammals in not being freely suspended
in a pleural membrane.  The pleura, on the other hand, is
reflected only over the anterior
surface of the lungs. The bronchi,
or primary divisions of the windpipe (fig. I84), diminish in size as
they pass through the lung, by
giving  off branches, which, in
turn, give off the true air-vesicles
of the lung.  When the bronchial              /
tubes reach  the  surface of the
lung, they open, by a series of
distinct apertures, into a series of
me air-sacs."  These are a series of
membranous sacs formed by the
continuation of the lining membrane of the bronchi, and  sup-                          <
ported by reflections of the serous
membrane of the thoracico-abdominal cavity.   In those aquatic;
birds which, like the Penguin, do    6
not enjoy the power of flight, the
air-cells are restricted to the abdomen; but in most birds they                              b
are continued along the sides of
the neck and limbs.   In  some Fig. I84. —Lung of Goose(afterOwen).
a Main bronchus dividing into seconcases-as the Pelican and Gannet  dary branches as it enters the lung,
these giving off smaller branches, the
-air-receptacles are situated be-  openings of which are seen on the
neath almost the whole of the in-  back of the bronchial tubes;b b Bristles passed from the bronchi through
tegument.  The air-cells not only  the apertures on the surface of the
the specific    lung by which the bronchi communigreatly reduce the specific gravity  cate with the air-receptacles.
of birds, and thus fit them for
an aerial life, but also assist in the mechanical work of respiration, and must also greatly promote the aeration of the
blood.
In connection with the air-receptacles, and as an extension
of them, is a series of cavities occupying the interior of a
greater or less number of the bones, and also containing air.
In young birds these air-cavities do not exist, and the bones
are filled with marrow as in the Mammals.  The extent also
to which the bones are "pneumatic" varies greatly in different
birds.  In the Penguin-which does not fly-all the bones
contain marrow, and there are no air-cavities. In the large




468              MANUAL OF ZOOLOGY.
Running birds (Cursores), such as the Ostrich, the bones of
the leg, pelvis, spine, ribs, skull, and sternum are pneumatic;
but the bones of the wings, with the exception of the scapular
arch, are without air-cavities, and permanently retain their
marrow. All birds which fly, with the singular exception of
the Woodcock, have air admitted to the humerus. In the
Pelican and Gannet, all the bones of the skeleton, except the
phalanges of the toes, are penetrated by air; and in the Hornbill even these are pneumatic. The functions discharged by
the air-cavities of the bones appear to be much the same as
those of the air-receptacles-namely, that of diminishing the
specific gravity of the body and subserving the aeration of the
blood.
The heart in all Birds consists of four chambers, two auricles
and two ventricles.  The right auricle and ventricle, constituting the right side of the heart, are wholly concerned with the
pulmonary circulation; the left auricle and ventricle, forming
the left side of the heart, are altogether occupied with the
systemic circulation; and no communication normally exists
in adult life between the two sides of the heart. In all essential details, both as regards the structure of the heart itself
and the course taken by the circulating fluid, Birds agree with
Mammals. The venous blood-namely, that which has circulated through the body-is returned by the venae cavae to the
right auricle, whence it is poured into the right ventricle. The
right ventricle propels it through the pulmonary artery to the
lungs, where it is aerated, and becomes arterial.  It is then
sent back by the pulmonary veins to the left auricle, whence it
is driven into the left ventricle. Finally, the left ventricle propels the aerated blood to all parts of the body through the
great systemic aorta.
The chief difference between Birds and Reptiles as regards
the course of the circulation is, that in the Birds the two sides
of the heart are completely separated from one another, the
blood sent to the lungs being exclusively venous, whereas that
which is sent to the body is exclusively arterial.  In Reptiles,
on the other hand, the pulmonary and systemic circulations
are connected together either in, or in the immediate neighbourhood of, the heart; so that mixed venous and arterial
blood is propelled both through the lungs and through every
part of the body.
In accordance with their extended respiration and high muscular activity, the complete separation of the greater and lesser
circulations, and the perfect structure of the heart, Birds maintain a higher average temperature than is the case with any




CHARACTERS OF AVES.                 469
other class of the Vertebrala. This result is also to a considerable extent conditioned by the non-conducting nature of the
combined down and feathers which form the integumentary
covering of Birds.
The urinary organs of Birds consist of two elongated kidneys and two ureters, but there is no urinary bladder. The
ureters open into the cloaca, or into a small urogenital sac
which communicates with the cloaca.
As regards the reproductive orgaJns, the males have two testes
placed above the upper extremities of the kidneys, and their
efferent ducts (zvasa defJerentia) open into the cloaca alongside
of the ureters. A male organ (penis) may or may not be present, but there is no perfect urethra. The female bird, as a
general rule, is provided with only one ovary and oviduct —
that of the left side-the corresponding organs of the right side
being rudimentary or absent. The oviduct is very long and
tortuous, and the egg, during its passage through it, receives
the albuminous covering which serves for the nutrition of the
embryo, and which is known as the "white" of the egg. The
lower portion of the oviduct is dilated, and the egg receives
here the calcareous covering which constitutes the "shell."
Finally, the oviduct debouches into the cloaca, into which the
egg, when ready, is expelled. The further development of the
chick is secured by the process of "incubation" or brooding,
for which birds are peculiarly adapted, in consequence of the
high temperature of their bodies.
The development of the ovum belongs to physiology, and
does not concern us here. It is sufficient to notice the means
by which in many cases the chick is ultimately enabled to escape
from the egg. When development has reached a stage at which
external life is possible, it is of course necessary for the chick
to be liberated from the egg, the shell of which is often extremely hard and resistant. To this end, in very many instances, the young bird is provided with a little calcareous
knob on the point of the upper mandible, and by means of this
it chips out an aperture through the shell.  Having effected its
purpose, this temporary appendage then disappears, without
leaving a trace behind.
The state of the young upon exclusion from the egg is very
different in different cases, and in accordance with this, Birds
have been divided into the two sections of the Autop/zagi or
Aves preacoces, and the Heterophagi or Aves altrices.  In the
lutozphagi the young bird is able to run about and help itself
from the moment of liberation from the egg. In the Hetero-.b4fgi the young are born in a blind and naked state, unable to




470               MANUAL OF ZOOLOGY.
feed themselves, or even to maintain unassisted the necessary
vital heat. In these birds, therefore, the young require to be
brooded over and fed by the parents for a longer or shorter
period after exclusion from the egg.
As regards their nervous system, the brain of Birds is relatively larger, especially as regards the size of the cerebrum
proper, than the brain of Reptiles, but its chief mass consists of the corpora striata. The cerebellum, though always
present, consists simply of the central lobe (the "vermiform
process"), and is not provided with the lateral lobes which
occur in the Mammals, or they are only present in a rudimentary form. The corpus callosum is absent, and the surface of
the cerebral hemispheres is devoid of convolutions.
As regards the organs of the senses, the eyes are always well
developed, and in no bird are they ever rudimentary or absent.
The chief peculiarity of the eye is that the cornea forms a
segment of a much smaller sphere than does the eyeball proper, so that the anterior part of the eye is obtusely conical,
whilst the posterior portion is spheroidal.  Another peculiarity
is that the form of the eye is maintained by a ring of from
thirteen to twenty bony plates, which are placed in the anterior
portion of the sclerotic coat. Eyelashes are almost universally
absent; but in addition to the ordinary upper and lower eyelids, Birds possess a third membranous eyelid-the " membrana
nictitans"-which is sometimes pearly-white, sometimes more or
less transparent.' This third eyelid is placed on the inner side
of the eye, and possesses a special muscular apparatus, by
which it can be drawn over the anterior surface of the eye like
a curtain, moderating the intensity of the light. As to the
organ of hearing, most birds possess no external ear or concha,
by which sounds'can be collected and transmitted to the internal ear. In some birds, however, as in the Ostrich and
Bustard, the external meatus auditorius is surrounded by a
circle of feathers, which can be raised and depressed at will.
The Nocturnal Birds, also, especially Owls, have the external
meatus auditorius protected by a musculo-membranous valve,
which foreshadows the cartilaginous concha of the majority of
Mammals.  The external nostrils in Birds are usually placed
on the sides of the upper mandible, near its base, in the form
* The membrana nictitans is simply a fold of the conjunctiva on the inner
side of the eye. It occurs in some Fishes (e.g., Sharks), in some Reptiles
and Amphibians, in Birds, in Monotremes and Marsupials, and in some of
the higher Mammals. In Man, however, in Monkeys, and in most of the
higher Mammals, it is rudimentary, and constitutes the so-called "plica
semilunaris."




CHARACTERS OF AVES.                  47 1
of simple perforations, which sometimes communicate from
side to side by the deficiency of the septum narium. In the
singular Aptleryx of New Zealand, the nostrils are placed at the
extreme end or tip of the elongated upper mandible. Sometimes the nostrils are defended by bristles, and sometimes by a
scale (Rasores). Taste must be absent, or almost absent, in
the great majority of birds, the tongue being nothing more than
a horny sheath surrounding a process of the hyoid bone, and
serving for deglutition or to seize the prey. In the Parrots,
however, the tongue is thick and fleshy, and some perception
of taste may be present. Touch or tactile sensibility, too, as
already remarked, is very poorly developed in Birds. The
body is entirely, or almost entirely, covered with feathers; the
anterior limbs are converted into wings, and rendered thereby
useless as organs of touch; and the posterior limbs are covered
with horny scales or feathers. The bill certainly officiates as
an organ of touch, but it cannot possess any acute sensibility,
as in most birds it is encased in a rigid horny sheath. In some
birds, however, such as the common Duck, the texture of the
bill is moderately soft, and it is richly supplied with filaments
of the fifth nerve; so that in these cases the bill doubtless constitutes a tolerably efficient tactile organ.  The "cere," too,
or the fleshy scale found at the base of the bill in some birds,
is in all probability also used as a tactile organ.
The last anatomical peculiarity of Birds which requires
notice is the peculiar apparatus known as the "inferior
larynx," by which the song of the singing birds is conditioned.
"The air-passages of birds commence by a simple superior
larynx, from which a long trachea extends to the anterior
aperture of the thorax, where it divides into the two bronchi,
one for each lung. At the place of its division there exists in
most birds a complicated mechanism of bones and cartilages,
moved by appropriate muscles, and constituting the true organ
of voice; this part is termed the i.n ferior larynx."-(Owen.)
The structure of the vocal apparatus is extremely complicated,
and there is no necessity for entering upon it here. It is to be
remembered, however, that those modifications of the voice
which constitute the song of birds, are produced in a special
and complex cavity placed at the point where the trachea
divides into the two bronchi, and not in a true larynx situated
at the summit of the windpipe.  Lastly, the trachea of birds is
always of considerable proportionate length, and it is often
twisted or dilated at intervals, this structure, doubtless, having
something to do with the production of vocal sounds."
* The student desirous of fuller information as to the anatomy of Birds




472              MANUAL OF ZOOLOGY.
Before passing on to the consideration of the divisions of
Birds, a few words may be said as to the.mzigralion of birds.
In temperate and cold climates comparatively few birds remain
constantly in the same region in which they were hatched.
Those which do so remain, are called " permanent birds " (aves
imanenfes).  Other birds, such as the Woodpeckers, wander
about from place to place, without having any fixed direction.
These are called " wandering birds " (aves erratice), and their
irregular movements are chiefly conditioned by the scarcity or
abundance of food in any particular locality. Other birds,
however, at certain seasons of the year undertake long journeys, usually uniting for this purpose into large flocks. These
birds-such as the swallows, for instance-are properly called
"migratory birds" (aves migratorice).   The movements of
these birds are conditioned by the necessity of having a certain mean temperature, and consequently they leave the cold
regions at the approach of winter, and return again for the
warmer season.
CHAPTER LXVII.
DIVISIONS OF BIRDS.
I. GENERAL DIVISIONS OF AVES.  2. NATATORES.
3. GRALLATORES.
OWING to the extreme compactness and homogeneity of the
entire class Aves, conditioned mainly by their adaptation to an
aerial mode of life, the subject of their classification has been
one of the greatest difficulties of the systematic Zoologist.
By Professor Huxley the Birds are divided into the following three orders:
I. SAURURE.- In this order the caudal vertebrae are numerous, and there is no ploughshare-bone.  The tail is longer
than the body, and the metacarpal bones are not anchylosed
together. This order includes only the single extinct bird the
Archalopteryx macrura, in which the long lizard-like tail is only
the most striking of several abnormalities.
2. RATIT. - This order comprises the Running birds,
should consult the masterly article by Owen on "Aves" in the' Cyclopxedia of Anatomy and Physiology,' or the second volume of the'Vertebrata' of the same author, from which the preceding summary has been
chiefly derived.




DIVISIONS OF BIRDS.                 473
which cannot fly, such as the Ostriches, Emeus, and Cassowaries. It is characterised by the fact that the sternum has
no median ridge or keel for the attachment of the great pectoral. muscles. The sternum is therefore raft-like (from the
Lat. rates, a raft), hence the name of the order.
3. CARINATE. -This comprises all the living Flying birds,
and is characterised by the fact that the sternum is furnished
with a prominent median ridge or keel (carina); hence the
name of the order.
This is probably the nearest approach to a strictly natural
classification of Birds which has yet been proposed; but the
order Carinatae is so disproportionately large as compared with
the other two, that it would lead to considerable inconvenience
if it were to be adopted here.
For the purposes of the present work it will be better to
adhere, with some modifications, to the classification of the
Birds originally proposed by Kirby, and since sanctioned by
the adoption of other distinguished naturalists. In this more
generally current, but certainly artificial, arrangement, the
Birds are divided into the following seven orders, founded
chiefly on the habits and mode of life, and on the resulting
anatomical or structural peculiarities.  To these an eighth
order must be added for the reception of the Mesozoic bird,
the A-rc/lcefpteryx, the discovery of which dates from a recent
period. Before entering upon a consideration of the individual orders, it will be as well to present to the student, synoptically and in an easily-remembered form, the leading differences
between these eight orders.
I. Natatores or Swoimmers.-These are characterised by the
fact that the toes are united by a membrane or web; the legs
are short, and are placed behind the point of equilibrium of
the body. The body is closely covered with feathers, and
with a thick coating of down next the skin.  (Ex. Ducks,
Geese, Pelicans, Gulls.)
2. Grallatores or Wlaaers.-The Wading birds are characterised by the possession of long legs, which are naked or
are not covered with feathers from the distal end of the tibia
downwards.  The toes are long, straight, and not united to
one another by a membrane or web.  (Fx. Curlews, Herons,
Storks.)
3. Cursores or Ruznners. -The Cursorial birds have very
short wings which are not used in flight, and the sternum is
without a ridge or keel.  The legs are exceedingly robust, and
there are only two, or at most three developed toes, the hindtoe or hallux being always absent or quite rudimentary.  The




474             MANUAL OF ZOOLOGY.
order agrees with the Ratitae of Huxley. (Ex. Ostrich, Emeu,
Apteryx.)
4. Rasores or Scratchers.-The Rasorial birds have usually
strong feet with powerful blunt claws adapted for scratching,
but sometimes for perching.  All the four toes are present.
The upper mandible is vaulted, and the nostrils are pierced in
a membranous space at its base, and are covered by a cartilaginous scale. (Ex. Fowls, Game-birds, Pigeons.)
5. Scansores or Climbers.-The Climbing birds are characterised by the structure.of the foot, in which two toes are
turned backwards and two forwards, so as to give the bird
unusual facilities in climbing trees.  (Ex. Parrots, Toucans,
Woodpeckers.)
6. Insessores or Perchers.-The Insessorial or Passerine birds
are characterised by having slender and short legs, with three
toes before and one behind, the two external toes generally
united by a very short membrane, and the whole foot being
adapted for perching. This is by far the largest order of birds,
and includes all our ordinary songsters, such as the Thrushes,
Linnets, Larks, &c., together with the Swallows, Hummingbirds, and many others.
7. Raptores or Birds of Prey.-The Pirds of Rapine are
characterised by their strong, curved, sharp-edged and sharppointed beak, adapted for tearing animal food; and by their
robust legs armed with four toes, three in front and one behind, all furnished with long, strong, crooked claws or talons.
(Ex. Eagles, Hawks, Owls.)
8. Saururre. -The metacarpal bones are not anchylosed
together, and the tail is longer than the body, and consists of
numerous free vertebrae, without a terminal ploughshare-bone.
The only member of this order is the extinct Arc(/al/tcryx.
ORDER I. NATATORES. — The order of the Nzltalores, or
Swimmers, comprises a number of birds which are as much or
even more at home in the water than upon the land. In
accordance with their aquatic habit of life, the Nlat/atores have
a boat-shaped body, usually with a long neck.  The legs are
short, and placed behind the centre of gravity of the body,
this position enabling them to act admirably as paddles, at the
same time that it renders the gait upon dry land more or less
awkward and shuffling. In all cases the toes are "webbed"
or united by membrane to a greater or less extent (fig. I85, A).
In many instances the membrane or web is stretched completely from toe to toe, but in others the web is divided or
split up between the toes, so that the toes are fringed with




DIVISIONS OF BIRDS.                 475
membranous borders, but the feet are only imperfectly webbed,
As their aquatic mode of life exposes them to great reductions
of temperature, the body of the Natatorial birds is closely
covered with feathers and with a thick coating of down next
the skin. They are, further, prevented from becoming wet in
the water by the great development of the coccygeal oil-gland,
by means of which the lustrous plumage is kept constantly
lubricated and waterproof.  They are usually polygamous,
each male consorting with several females; and the young
are hatched in a condition not requiring any special assistance
from the parents, being able to swim and procure food for
themselves from the moment they are liberated from the egg.
Fig. 185.-Natatores. A, Foot of Cormorant (Phalacrocorax); B, Beak of the
Bean-goose (A oser segetzun).
The Natatores are divided into the following four families:Fam. i. Brevipennatae.- In this family of the swimming
birds the wings are. always short, and are sometimes useless as
organs of flight, the tail is very short, and the legs are placed
very far back, so as to render terrestrial progression very
difficult or awkward. The family includes the Penguins, Auks,
Guillemots, Divers, and Grebes. In the Penguins (Spheniscida')
the wings are completely rudimentary, without quills, and
covered with a scaly skin. They are useless, as far as flight
is concerned, but they are employed by the bird as fins, enabling it to swim under water with great facility, and they are
also used on the land as fore-legs. The feet are webbed, and
the hinder toe is rudimentary or wanting. The Penguins live
gregariously in the seas of the southern hemisphere, on the
coasts of South Africa and South America, especially at Terra
del Fuego, and in the solitary islands of the South Pacific.
When on land the Penguins stand bolt upright, and as they
usually stand on the shore in long lines, they are said to present
a most singular appearance.  The best-known species are the




476              MANUAL OF ZOOLOGY.
Jackass Penguin (Spheniscus demnersus) of the Falkland Islands,
and the King Penguin (Aptenodytes Patagonica) of the Straits
of Magalhaens.  In the Auks (Alcidac) the wings, are better
developed than in the Penguins, and they contain true quillfeathers; but they are still short as compared with the size of
Fig. i86.-Jackass Penguin (S.5heniscus demersus).
the body, and are of more use as fins than for flight. The
Great Auk or Gare-fowl (Alca inmjennis) is remarkable for being
one of the birds which appear to have become entirely extinct
within the human period, having been, in fact, destroyed by
man himself.  It used to abound in the arctic regions, and
occasionally visited our own shores in the winter. The Little
Auk (Afergu/us alba) occurs still in abundance in the seas of
the arctic regions. Other well-known members of this group
are the Razor-bill, the Puffins (Fra/ercula arctica), and the
Guillemots (Uria). The Guillemots have a short tail, narrow
and pointed wings, short feet, and no hallux.  Like the other




NATATORES.                     477
members of the family, they inhabit northern and polar re
gions.
In the Divers (ColymbidaC), comprising the true Divers and
the Grebes, the power of flight is pretty well developed, but
the bird still'is much more active in the water, swimming or
diving, than on land. The Grebes are not uncommon in Britain, and are largely killed for making muffs, collars, and other
articles of winter dress. They have the membrane between
the toes deeply incised. They haunt the sea as well as lakes
and rivers, and swim and dive admirably. In the Divers proper the front toes are completely united by a membrane. The
Northern Diver or Loon (Colymbus glacialis) is a familiar example, and is found on the coasts of high northern latitudes.
Pain. 2. Lonz>i~pennata.-This family of Natatores is characterised by the well-developed wings, the pointed, sometimes
knife-like, sometimes hooked bill, and by never having the
hallux united with the anterior toes by a membrane. The
following are the more important groups coming under this
head:
a. Laridae, or Gulls and Terns, having powerful wings, a free
hinder toe, and the three anterior toes united by a membrane.
The gulls form an exceedingly large and widely distributed
group of birds; and the Terns or Sea-swallows are equally
beautiful, if not quite so common. The Terns are distinguished
by their long and pointed wings, forked tail, and comparatively
short legs. They fly with great rapidity over the surface of the
sea, from which they pick up their food.
b. Proce//aridc, or Petrels, closely resembling the true Gulls,
but having a rudimentary hinder toe, and having the upper
mandible strongly hooked. The smaller species of Petrel are
well known to all sailors under the name of Storm-birds and
Mother Carey's Chickens. They are nocturnal or crepuscular
in their habits, breed in holes in the rocks, lay but one egg,
and are almost all of small size and more or less sombre
plumage.  The largest member of the group is the gigantic
Albatross (Diomnedea exulans), not uncommonly found far from
land in both the northern and southern oceans. The Albatross
sometimes measures as much as fifteen feet from the tip of
one wing to that of the other, and the flight is powerful in
proportion.
Falnl. 3. Totlipalhnale, characterised by having the hinder
toe or hallux more or less directed inwards, and united to the
innermost of the anterior toes by a membrane (fig. I85, A). In
this family are the Pelicans, Cormorants, Gannets, Frigatebirds, Darters, and others. They all fly well, and have short




478             MANUAL OF ZOOLOGY.
legs, and amongst them are almost the only Natatorial Birds
which ever perch upon trees.
The Pelicans (.Pelicanide) are large birds, which subsist on
fish, and are found in Europe, Asia, Africa, and the New
World.  They sometimes measure as much as from ten to fifteen feet between the tips of the wings, and most of the bones
are pneumatic, so that the skeleton is extremely light. The
lower mandible is composed of two flexible branches which
serve for the support of a large "' gular " pouch, formed by the
loose unfeathered skin of the neck. The bill is long and
straight, and the upper mandible is strongly hooked at the tip.
The fish captured by the bird are temporarily deposited in this
pouch, and the parent birds feed their young out of it.
In the Cormorants (P]halacrocorax) there is no pouch beneath the lower mandible, but the skin of the throat is very
lax and distensible; the nail of the middle toe is serrated.
They are widely distributed over the world, one species being
very abundant in many parts of Europe.   The Gannets
(Sula) have a compressed bill, the margins of which are finely
crenate or toothed. They occur abundantly on many parts of
the coasts of northern Europe, one of the most noted of their
stations being the Bass Rock at the mouth of the Firth of
Forth. Another species (Sula variegatla) is of greater importance to man, as being one of the birds from the accumulated
droppings of which guano is derived.   The Frigate-birds
(TacAyjpetes) are chiefly remarkable for their extraordinary
powers of flight, conditioned by their enormously long and
powerful wings and long forked tail. They occur on the coasts
of tropical America, and are often found at immense distances
from any land.  The Tropic-birds (Phacton) inhabit intertropical regions, and are found far out at sea. They have
short feeble feet, and long pointed wings.
The Darters or Snake-birds (Plotus) are somewhat aberrant
members of this group, characterised by their elongated necks
and long pointed bills. They occur in America, Africa, and
Australia, and catch fish by suddenly darting upon them from
above.
Farn. 4. Lamellirostres.-The last family of the Natatores
is that of the Lanmellirstres, including the Ducks, Geese,
Swans, and Flamingoes; and characterised by the form of the
beak (figs. 179, I85), which is flattened in form and covered
with a soft skin.  The edges of the bill are further furnished
with a series of transverse plates or lamelloe, which form a kind
of fringe or " strainer," by means of which these birds sift the
mud in which they habitually seek their food. The bill is




NATATORES.                    479
richly supplied with filaments of the fifth nerve, and doubtless
serves as an efficient organ of touch. The feet are furnished
with four toes, of which three are turned forwards, and are
webbed, whilst the fourth is turned backwards, and is free.
The trachea in the males is often enlarged or twisted in its
lower part, and co-operates in the production of the peculiar
clanging note of most of these birds. The body is heavy, and
the wings only moderately developed.
The groups of the Ducks (Antaidce), Geese (Anserin&w),
and Swans (Cjgnidce), are too familiar to require much special.
notice.  The Anatide, or true Ducks, have the hallux furnished with a very narrow membranous lobe, and the lamina
of the upper mandible generally projecting. As examples may
be taken the Mallards and Teals (Boschas), the Widgeons
(Azareca), the Shoveller (Anas), and the Pin-tail Ducks (Dafila).
The Sea-Ducks (Fuligulinze) frequent the sea chiefly, and have
the hallux furnished with a wide membranous lobe. Good
examples are the Eider-duck (Somateria), the Surf-duck
(Oidemia), the Canvass-back Duck, and Pochard (F]igz3t a),
and the Golden-eye (Clangula).
The Anserince are distinguished from the Ducks chiefly by
their stronger and longer legs, and comparatively shorter wings.
Good examples are the Grey Lag (Anser ferus), the Canada
Goose (A. Canadensis), the Bean-goose (A. Segeturn), and the
Snow-goose (A. hyperboreus).
In the Swans the neck is extremely long, and the legs are
short. In the Hooper Swan (Cygnus fernus) the sternal keel is
double, and forms a cavity for the reception of a convoluted
portion of the trachea. This is not the case, however, with
the Mute Swan (C. olor), the Black Swan (C. atratus), or the
Trumpeter Swan (C. buccinalor), all well-known members of
the group.
The Flamingoes, however, forming the group of the Phoenicoptericea, require some notice; if only for the fact that the legs are
so long and slender that they have often been placed in the
order Gra/latores on this account. The three anterior toes,
however, are webbed or completely united by membrane, and
the bill is lamellate, so that there can be little hesitation in
leaving the Flamingo in its present position amongst the Natatores. The bill is singularly bent, both mandibles being suddenly curved downwards from the middle. The common
Flamingo (Phwnicptcrus ruber) occurs abundantly in various
parts of southern Europe.  It stands between three and four
feet in height, the general plumage being rose-coloured, the
wing-coverts red, and the quill-feathers of the wings black.




480              MANUAL OF ZOOLOGY.
The tongue is fleshy, and one of the extravagances of the
Romans during the later period of the Empire was to have
dishes composed solely of Flamingoes' tongues. Other species
occur in South America and Africa.
ORDER II. GRALLATORES.-The birds comprising the order
of the Grallatores, or Waders, for the most part frequent the
banks of rivers and lakes, the shores of estuaries, marshes, lagoons, and shallow pools, though some of them keep almost
exclusively to dry land, preferring, however, moist and damp
situations. In accordance with their semi-aquatic amphibious
habits, the Waders are distinguished by the great length of their
legs; the increase in length being mainly due to the great elongation of the tarso-metatarsus.  The legs are also unfeathered
from the lower end of the tibia downwards. The toes are
elongated and straight (fig. I87, A), and are never completely
palmate, though sometimes semi-palmate. There are three
anterior toes, and usually a short hallux, but the latter may be
wanting. The wings are long, and the power of flight usually
considerable; but the tail is short, and the long legs are
stretched out behind in flight to compensate for the brevity of
the tail. The body is generally slender, and the neck and
beak usually of considerable length (fig. I87, B). They are
sometimes polygamous, sometimes monogamous, and the young
of the former are able to run about as soon as they are hatched.
Fig. I87.-Grallatores. A, Leg and foot of the Curlew; B, Head of Snipe:
C, Beak of the Avocet.
The most typical Waders-those, namely, which are semiaquatic in their habits-spend most of their time wading about
in shallow waters or marshes, feeding upon small fishes, worms,




GRALLATORES.                      481
shell-fish, or insects. Others, such as the Storks, live mostly
upon the land, and are more or less exclusively vegetablefeeders.
The Gralla/ores are divided into the four families of the
Macrodaclyli, the Cultirostres, the Longirostres, and the Pressirostres.
Paim. I. AlacrodacyZli.-In this family the feet are furnished
with four elongated, sometimes lobate, toes, and the wings are
of moderate or less than average size. In many of their characters a considerable number of the birds of this family approach the Rasorial birds, and differ from the true Waders.
The beak is mostly short, rarely longer than the head, and is
compressed from side to side, or wedge-shaped.  The legs are
strong and not particularly lengthy; but the toes are often of
great length, and are furnished with long claws.  The neck is
not very long, and the tail is very short.  Some of them are
strictly aquatic in their habits, and, like the Coots, approach
in many respects to the Natatores; others, again, are exclusively
terrestrial. The most familiar members of this family are the
Rails (RaZlus), Water-hens (Gallinuile), the Coots (Fulica),
and the Jacana (Parra jacana). The Water-hens and Coots
are aquatic or semi-aquatic, swimming and diving with great
ease. In the Coots the toes are semi-palmate, being bordered
by membranous lobes, like the toes of the Grebes, but the
toes are not fringed in the Gallinules.  Amongst the Coots
should probably be placed the Notornis (Owen), long supposed
to be extinct, but recently proved to be still living in the
Middle Island of New Zealand.  The Notornsisis much larger
than the, ordinary Coots, and is remarkable in the fact that,
like many extinct and some living New Zealand birds, the
wings are so rudimentary as to be useless for flight. The true
Rails, comprising the common Land-rail (RaD/us aquaticus),
and the Corn-crake (Crexpratensis) of Britain, and the Marsh
Hen (Rallus elegans), and Virginian Rail (R. Virginianus) of
North America, live almost exclusively on land, though the
former usually frequents damp or marshy places.  In the
Jacanas, lastly, the feet are furnished with excessively' long
and slender toes, which enable the bird to run about upon the
leaves of aquatic plants; whilst the carpus is armed with formidable spurs.  They are natives of South America, Africa,
and India. Closely allied to the Jacanas are the Screamers
(Palamedea) of South America, of which the Horned Screamer
(P. cornuta) is the best known.  It has a long frontal horn,
and has spurs implanted on the edge of the wing.
Eaim. 2. Cultirostres.-In this family of the Gr-alalaores are




482             MANUAL OF ZOOLOGY.
some of the most typical and familiar forms contained in the
entire order. The bill in this family is long-usually longer
than the head-and is compressed from side to side; the legs
are long and slender, having a considerable portion of the
tibie unfeathered; and the feet have four toes, which are
usually connected to a greater or less extent at their bases by
membrane. In this family are the Cranes, Herons, Stork, Ibis,
Spoonbill, and others of less importance.
Fig. i88.-Crested Heron (Ardea cinerea). Europe.
The Cranes (Gruidve) are large and elegant birds, and are
chiefly remarkab.e for their long migrations, which were noticed
by many classical authors.  In these journeys the Cranes
usually fly in large flocks, led by a single leader, so that the
whole assemblage assumes a wedge-like form; or they fly in
long lines. The common Crane (Grus cinerea) breeds in the
north of Europe and Siberia, and migrates southwards at the
approach of winter. The Numidian Crane or Demoiselle inhabits Asia and Africa, the Stanley Cranes (Anthropoides) are
natives of the East Indies, and the Crowned Cranes (Bafiearica)
are African. The Herons (Ardeidce) are familiarly known to
every one in the person of the common Grey or Crested Heron




GRALLATORES.                      483
(Ardea cinerea, fig. i88).  It was one of the birds most generally pursued in the now almost extinct sport of falconry.
Various species of Heron are found over the whole world, both
in temperate and hot climates. Here, also, belong the various
species of Night Heron (NVycticorax), the Bitterns (Botaurus),
and the Boat-bills (Cancroma).
The Ibises (Tantalinze) form  a group of beautiful birds,
species of which occur in all the warm countries of the world.
They are distinguished by their metallic colours, long, cylindrical, curved bill, and more or less naked head. One, the
Ibis religiosa, was regarded by the ancient Egyptians as a deity,
and was treated with divine honours, being often embalmed
along with their mummies, or figured on their monuments.
The Storks (Ciconince) are large birds, of which one, the
common Stork (Ciconzia alba), is rarely found in Britain, but
occurs commonly on the Continent, where it is often semidomesticate(l. The Storks live in marshes, and feed on frogs,
fishes, &c. Nearly related to the true Storks are the gigantic
Marabout (Ciconia Marabou)i and Adjutant (C. Argala) of
Africa and India, which possess a sausage-shaped appendage
in front of the neck.
The Spoonbills (Plataleadee) are also large birds, very like
the Storks, but the bill is flattened out so as to form a broad
spoon-like plate.  The common White Spoonbill (Platalca
leucorodia) is found commonly on the Continent, but is of very
rare occurrence in Britain.
Farn. 3. Longirostres.-The third family of Waders is that
of the Longirostres, characterised by the possession of long,
slender, soft bills, grooved for the perforations of the nostrils
(fig. i87, B). The legs are sometimes rather short, sometimes
of great length; the toes are of moderate length, and the
hallux is usually short, and is sometimes absent. The bill in
these birds serves as an organ of touch, being used as a kind
of probe to feel for food in mud of marshy soil. To fulfil this
purpose, the tip of the bill is furnished with numerous filaments
of the fifth nerve.  They feed mostly upon insects and worms,
and are not strictly aquatic in their habits, mostly frequenting
marshy districts, moors, fens, the banks of rivers or lakes, or
the shores of the sea.
In this family of the Long-billed Waders are the various
species of Snipe and Woodcock (Scolop5acide), the Sandpipers
(Tringa), the Curlews (NlVmezius), the Turnstones (Strepsilas),
the Ruffs (AMachetes), the Redshanks (ITotanus), the Godwits
(Limosa), and others which need no special notice.
Eain. 4. Pressirostres. -- The members of this fanmily are
22




484             MANUAL OF ZOOLOGY.
characterised by the moderate length of the bill, which is
seldom longer than the head, and has a compressed tip. The
legs are long, but the toes are short, and are almost always
partially connected together at their bases by membrane. The
hallux is short, and is often wanting. The wings are long, and
they can both fly powerfully and run with great swiftness.  In
this section are two very distinct sub-families, the Charadriidce
or Plovers, and the Otidce or Bustards. In the former of these
the legs are long and slender, the toes are united at their bases
by a small membrane, and the hind-toe is very small and raised
above the ground, or is entirely wanting.  In this group are
the true Plovers and Lapwings (Charadrius and Vanellus), the
Pratincoles (Glareola), the Long-shanks (Rimazanto as), the
Oyster-catcher (HwNmatopus), and the Thick-knee (CEdicnzenmus).
In the Otidwe, or Bustards, the legs are long and the toes are
short and furnished with stout claws. The hinder toe or hallux
is entirely wanting; and these birds are chiefly interesting from
the affinities which they exhibit to the Rasores on the one
hand, and to the Cursores (Ostrich, &c.) on the other. The
wings, however, are of ample size, and the tail is long, the
reverse being the case in the Cursores.  The Bustards are
entirely confined to the Old World, and two species were formerly not uncommon in Britain. They are found in plains
and downs, and rarely fly, but run with great swiftness, using
the wings to accelerate their course.  They are polygamous,
and the males are generally brighter and more variegated in
plumage than the females.
CHAPTER LXVIII.
CURSORES AND RASORES.
ORDER III. CURSORES.-The third order of Birds is that of
the Cursores, or Runners, comprising the Ostriches, Rheas,
Cassowaries, Emeus, and the singular A4teryx of New Zealand.
In many respects the Cursores are to be looked upon as an
artificial assemblage; but in the meanwhile it will be most
convenient to consider them as forming a distinct division.
The Cursores are characterised by the rudimentary condition
of the wings, which are so short as to be useless for flight, and
by the compensating length and strength of the legs. In
accordance with this condition of the limbs, many of the bones




CURSORES AND RASORES.                    485
retain their marrow, and the sternum (fig. i89, B) is destitute
of the prominent ridge or keel, to which the great pectoral
muscles are attached (hence the name of Raltide, applied by
Huxley to the order). In the Ostrich, the pubic bones of the
pelvis unite to form a symphysis pubis, as they do in no other
bird; and in all, the pelvic arch possesses unusual strength and
stability. The legs are extremely robust and powerful, and the
hind-toe is entirely wanting, except in the Apteryx, in which it
is rudimentary.  The anterior toes are two or three in number,
and are provided with strong blunt claws or nails. The plumage
presents the remarkable peculiarity that the barbs of the
feathers, instead of being connected to one another by hooked
barbules, as is usually the case, are remote and disconnected
from one another, presenting some resemblance to hairs
Fig. I89.-Cursores. A, Foot of the Ostrich ('truthzio cameolis); B, Sternum of
the Enmeu (Dromaiozs Novce-Hollandiie).
The order Cursores may be divided into the two families of
the Struthionide  and the Apterygidce-the former characterised
by the absence of the hallux, and comprising the Ostrich,
Rhea, Emeu, and Cassowary, with several extinct forms; the
latter comprising only the Apteryx of New Zealand, and characterised by the possession of a rudimentary hallux.
The African Ostrich (Stru/hio camelus) occurs in the desert
plains of Africa and Arabia, and is the largest of all living
birds, attaining a height of from six to eight feet. The head
and neck are nearly naked, and the quill-feathers of the wings
and tail have their barbs wholly disconnected, constituting the
ostrich-plumes of commerce. The legs are extremely strong,
and are terminated by two toes only (fig. I89, A), these consisting respectively of four and five phalanges, showing that it
is the hallux and the innermost toe which are wanting. The
internal one of the two toes is much the largest, and is clawed,
the outer toe is small and clawless. The Ostriches run with
extraordinary speed, and can outstrip the fastest horse. They




486             MANUAL OF ZOOLOGY.
are polygamous, each male consorting with several females, and
they generally keep together in larger or smaller flocks. The
eggs are of great size, averaging three pounds each in weight,
and the hens lay their eggs in the same nest, this being nothing
more than a hole scratched in the sand. The eggs appear to
be hatched mainly by the exertions of both parents, relieving
each other in the task of incubation, but also partly by the heat
of the sun.,
The American Ostriches or Rheas are much smaller than
the African Ostrich, and have the head feathered, whilst the
feet are furnished with three toes each. The wings are rudimentary, and the phalanges are plumed and terminated by a
spur. They inhabit the great plains of South America, and are
polygamous.
The Emeu (Dromaius Nove-Hollandie) is exclusively found
in the Australian continent, and nearly equals the African
Ostrich in size, attaining a height of from five to seven feet.
The feet are furnished with three toes each, and the head is
feathered.  The throat, however, is naked, and the general
plumage resembles long hairs, the feathers hanging down on
both sides of the body from a central line or parting which
runs down the middle of the back. The Emeus are monogamous, and the eggs are dark green in colour. The male
Emeu is smaller than the female, and undertakes all the duties
of incubation.
The last of the Struthionidce is the Cassowary (Casuarius
ga/eatus), which inhabits the Moluccan  Islands and New
Guinea, and was first brought alive to Europe by the Dutch.
It stands about five feet in height, and possesses a singular
horny crest upon its head. The head and neck are naked,
with pendent wattles, and the feet have three toes each. The
general plumage is black, and the feathers more or less closely
resemble hairs. The wings are rudimentary, each with five
naked pointed quills. The male is much the smallest, and sits
upon the eggs. Besides the Galeated Cassowary, other species
have been described from New Britain and North Australia.
The second family of the Cursorial birds is that of the
Apterygidce, comprising only the singular Apteryx of New
Zealand.  The beak in the 4ipte;yx is long, slender, and
slightly curved, the tip being obtuse, and the nostrils placed
at the extremity of the upper mandible. The legs are comparatively short, and there is a rudimentary hind-toe or hallux,
forming a kind of spur, furnished with a claw. The wings are
* Mr Sclater, however, states that the duty of incubation is entirely
taken by the males.




RASORES.                       487
entirely rudimentary, and are quite concealed by the feathers,
each terminating in a sharp claw. The feathers are long and
narrow, and the tail is short and inconspicuous.  The Apteryx
is wholly confined to New Zealand, and is nocturnal in its
habits, living upon insects and worms.  Three species of
Apteryx have been described, of which A. australis (fig. 90o)
is the best known.
Fig.. I9o.-AiJteryx australis. (Gould.)
Besides the above-mentioned living forms, the order Cursores
comprises several gigantic extinct forms, which will be treated
of when describing the geological distribution of Birds as a
class.
ORDER IV. RASORES.-The fourth order of Birds is that of
the Rasores, or Scratchers, often spoken of collectively as the
"Gallinaceous" birds, from  the old name of " Gallinme," given
to the order by Linneus. The Rasores are characterised by
the convex, vaulted upper mandible, having the nostrils pierced
in a membranous space at its base. The nostrils are covered
by a cartilaginous scale.  The legs are strong and robust,
mostly covered with feathers as far as the joint between the
tibia and tarso-metatarsus. There are four toes, three in front
and one behind, the latter being short, and placed at a higher
evel than the other toes. All the toes terminate in strong




488              MANUAL OF ZOOLOGY.
blunt claws suitable for scratching (fig. I9I, A). The food of
the Scratchers or Gallinaceous birds consists chiefly of hard
grains and seeds, and in accordance with this they have a capacious crop and an extremely strong and muscular gizzard.
They mostly nidificate, or build their nests, upon the ground,
and the more typical members of the order are polygamous.
The males take no part in either nidificatjon or incubation,
and the young are generally "precocious," being able to run
about and provide themselves with food from the moment they
quit the egg. The young of the Pigeons and Doves, however,
are brought forth in a comparatively helpless condition. The
wings in the majority of the Rasores are more or less weak,
and the flight is feeble and accompanied with a whirring sound.
Many of the Pigeons, however, are capable of very powerful
and sustained flight.
The order Rasores is divided into two sub-orders, called respectively the Ganilzacei and the Colzmbacei, or sometimes,
from the characters of the sounds which they utter, the Clameza
tores and the Gemitores.
Sub - order i. Gallinacei or Carnzatores. - This sub - order
comprises the typical members of the order Rasores, such as
the common Fowls, Turkeys, Partridge, Grouse, Pea-fowl, and
a number of allied forms. Its characters are therefore those
of the order itself, but it is especially distinguished from the
Columbacei by being less fully adapted for flight. The body is
} 
Fig. 19.-Rasores. A, Foot of Fowl (Gallus Bankiva); B, Head of Guinea-fowl.
much heavier comparatively speaking, the legs and feet are
stronger, and the wings shorter and less powerful.  On the
whole, therefore, these birds are worse fliers than the Coalzmbacei,
and are better adapted for living upon the ground. The hallux
is elevated above the anterior toes, and merely touches the
ground in walking. The back of the tarsus, too, is usually
furnished in the males with a spur (ca/car), which is used as an
offensive weapon, and has sometimes been looked upon as a




RASORES.                      489
rudimentary toe.#  Lastly, the Gal/inacei are mostly polygamous, and the males are usually much more -brilliantly coloured
than the females, this being an adaptive modification of the
plumage to meet this peculiarity in their mode of life.t
The following are the most important families of the Gallinacei -
The Tetraonidce, or Grouse family, comprises the various
species of Grouse (eterao), the Ruffed Grouse (Bonasa), the
Cock ot the Plains ( Centrocercus), and the Ptarmigans (Lagopus).
The Perdicidca, or Partridge family, comprises the Partridges (Perdix), the Francolins (Francoainus), the Quails (Coturnix), the  Maryland Quail (Ortyx), the Tufted  Quails
(Lophortyx), &c.
The Phasianide or Pheasant family, comprises the Turkeys
and Guinea-fowl (AfeZeagriae), the common Pheasant (Phasianus Colchicus), the Golden and Silver Pheasants, the common
Fowl (Ga/zuis domesticus), and the Pea-fowl (Pavonine).  None
of these birds-all of which can be domesticated, and most of
which are of great value to man-are natives of this country,
though they will all breed readily, and thrive even in confinement. The domestic Turkey (Meleagris gallopavo) is originally
a native of North America, where it still occurs in a wild condition, having been brought to Europe about the beginning of
the sixteenth century. T~ he Guinea-fowl (Nurnida AIMeeagris) is
originally an African bird. The common Pheasant (P/hasianus
Colchicus), though now regarded as an indigenous bird, truly
belongs to Asia, and it is asserted that it was really brought to
Europe from Colchis by the Greeks; hence its specific name.
The common Fowl is certainly not a native of Europe, and it is
almost as certainly a native of Asia or of some of the Asiatic
islands; but its exact original habitat is uncertain, as is the
species from which the domestic breeds are descended (commonly said to be the Gallus Bankiva of Java). The introduction of the Fowl into Europe is lost in the mists of antiquity,
and it is wholly unknown whence the original stock may have
been brought.  The Pea-fowl (Pavo) are really natives of
Thibet and Hindostan, and were originally brought to Greece
by Alexander the Great. They were formerly much esteemed
as food, but are now regarded merely from an ornamental
point of view.
* In some cases (as in the Java Peacock) the female possesses spurs as
well as the male; and sometimes (as in Polyplectl-on) there are two or more
spurs on each leg of the male.
t The Guinea-fowl, Red Grouse, Ptarmigan, and Partridge are monogamous, in a state of nature at any rate.




490             MANUAL OF ZOOLOGY.
The Afegaspodidre, or Mound-birds, belong to India and Australia, and have very large feet and long claws. They build
immense mounds, often six or eight feet high, and twenty or
thirty feet in diameter. They lay their eggs in the centre of
these mounds at a depth of two or three feet, and leave them
to be hatched by the heat produced by the fermentation of the
vegetable matter of the mass.
The Craci/ce, or Curassows, are large heavy birds, belonging
to Central and South America, and to a great extent arboreal
in their habits. The oest-known species is the Crested Curassow (Crax aleclor) of Mexico and Brazil.
S -
Fig. 192.-Columbidae. Rock-pigeon (Columba ivour).
The second sub-order of the,Rasores is that of the Columbacec
or Gemitores, comprising the Doves and Pigeons, and often
raised to the rank of a distinct order under the name of Coa
lumb&.  The Columbacci are separated from the more typical
members of the Rasores by being furnished with strong wings,
so as to endow them with considerable powers.of flight. In
place, therefore; of being chiefly ground-birds, they are to a
great extent arboreal in their habits, and in accordance with




RASORES.                      491
this the feet are slender, and are well adapted for perching.
There are four toes, three in front and one behind, and the
former are never united towards their bases by a membrane,
though the base of the outer toe is sometimes united to that of
the middle toe. The hallux is articulated'on the same plane
as the other toes, and touches the ground in walking. Lastly,
they are all monogamous, and pair for life; in consequence of
which fact, and of their being readily susceptible of domestication, they present an enormous number of varieties, often so
different from one another that they would certainly be described as distinct species if found in a wild state. It seems
certain, however, that all the common domestic breeds of
Pigeons, however unlike one another, are really descended from
the Rock-pigeon (Cblumba Zivia), which occurs wild in many
parts of Europe, and has retained its distinguishing peculiarities unaltered for many centuries up to the present day.
Finally, the young of the Columnbacei are born in a naked and
helpless state, whilst those of the Gallinacei are " precocious,"
and can take care of themselves from the moment of their
liberation from the egg.
Of the various living birds included in this section, the true
Pigeons (Columdbice) are too well known to require any description; but the Ground-pigeons (Gouridae) depart to some
extent from this type, being ground-loving birds, more closely
allied to the ordinary Galzinacei. The only other member of
the sub-order which requires special notice, is the remarkable
extinct bird, the Dodo (Diduzs ineptus), which seems certainly
to belong here, though its size was gigantic, and some of its
characters very anomalous. The Dodo may, properly speaking, be said to be extinct, since it no longer occurs in a living
state; but it is not extinct in the sense that geologists speak of
"fossils" as extinct; since it has been extirpated by man himself within quite a recent period-in fact not more than three
centuries ago.  The Dodo was an inhabitant of the Island of
the Mauritius up to the commencement of the seventeenth century, and was a large bird, considerably over the size of a swan.
All that remains nowadays to prove the existence of the Dodo
are two or three old, but apparently faithful, oil-paintings, two
heads, a foot, and some feathers, to which a few bones have
recently been added. The Dodo owed its extermination -to
the fact that it was unable to fly. The body must have been
extremely weighty, and the wings were rudimentary and completely useless as organs of flight.  The legs were short and
stout, the feet had four toes each, and the tail was extremely
short, carrying,' as well as the wings, a tuft of soft plumles. The




492             MANUAL OF ZOOLOGY.
beak (unlike that of any of the Co/umbacei except the little
Didunculus strigirostris) was strongly arched towards the end,
and the upper mandible had a strongly-hooked apex, not at
all unlike that of a bird of prey. The nearest living ally of
the Dodo appears to be the little iDidunculus just alluded to,
which inhabits the Navigator Islands, and is little bigger than
a partridge.
It is worthy of notice that in the little island of Rodriguez,
lying to the east of Mauritius, there existed one large wingless
bird, the Solitaire or Pezopihaps, which has likewise become extinct during the human period. In the Mauritius, also, occur
the remains of the Aphanafteryx, a wingless bird believed to
have strong Grallatorial affinities, and to have been exterminated by man. Other cases in which wingless birds have been,
or are being, exterminated by man, lead us to the belief that
the absence of wings is not compatible with the coexistence of
birds and human beings. In other words, the sole protection
possessed by birds against the destructive propensities of man
is to be found in their power of flight.
CHAPTER LXIX.
SCANSORES AND INSESSORES.
ORDER V. SCANSORES.-The order of the Scansorial or Climbing birds is easily and very shortly defined, having no other
distinctive and exclusive peculiarity except the fact that the
feet are provided with four toes, of which two are turned backwards and two forwards.  Of the two toes which are directed
backwards, one, of course, is the hallux or proper hind-toe,
and the other is the outermost of the normal three anterior
toes. This arrangement of the toes (fig. I93, A) enables the
Scansores to climb with unusual facility.  Their powers of
flight, on the other hand, are generally only moderate and
below the average. Their food consists of insects or fruit..
Their nests are usually made in the hollows of old trees, but
some of them have the remarkable peculiarity that they build
no nests of their own, but deposit their eggs in the nests of
other birds. They are all monogamous.
The most important families of the Scansores are the Cuckoos
f Cuciidce), the Woodpeckers and Wry-necks (Picilta), the Par



SCANSORES.                       493
rots (Psitlacide), the Toucans (Rhcamp2asftide), -and the Trogons (Trogonidre).
Fig. 193.-Scans'res. A, Foot of Woodpecker (Picus);
B, Head of Love-bird (Agapornzis).
The Cucuiidae, or Cuckoos, are chiefly remarkable for the extraordinary fact that many of them, instead of nidificating and
incubating for themselves, lay their eggs in the nests of oth'er
birds. -The only bird not belonging to this family which has
the same "parasitic" habit, is the Cow Bunting (AMolotoklws
pecoris) of the United States.  As a rule, only one egg is
deposited in each, nest, and the young Cuckoo which is
hatched from it, is brought up by the foster-parent, generally
at the expense of the legitimate offspring. The large Channelbill (Scythrojs Novce-Ho/lazdiae) is said to possess the same
curious habit, but many species of this group build nests for
themselves in the ordinary manner.
The second family of the Scansores is that of the Picidn&, and
comprises the Woodpeckers and Wry-necks.  These birds feed
chiefly upon insects, and the tongue is extensible, barbed at
the point, and covered with a viscid secretion, so as to enable
them to catch their prey by suddenly darting it out. The bill
is strong and wedge-shaped, and the claws crooked.  The tailfeathers terminate in points, and are unusually hard and stiff,
assisting the bird in running up the trunks of trees.
The next family is that of the Parrots (Psitlacidce), the
largest group of the Scansores, comprising over three hundred
species.  The bill in the Parrots is large and strong, and the
upper mandible is considerably longer than the lower and is
hooked at its extremity (fig. 193, B). The bill is used as a
kind of third foot in climbing. At the base of the upper
mandible is a "cere," in which the nostrils are pierced.  The
tongue is soft and fleshy.  The feet are especially adapted for




49 4             AMANUAL OF ZOOLOGY.
climbing, some, however, of the Parrots moving about actively
on the ground. The colours of the plumage are generally extremely bright and gaudy; and they live for the most part upon
Fig. 194. —Psittacide. Purple-capped Lory (Lorius donmicella).
fruits. The Psittacidve are distributed throughout the tropics,
and in the southern hemisphere as far south as the 5 2d parallel.
They are monogamous, and make their nests in holes in the
rocks. Their natural voice is harsh and grating. The true
Parrots (Psittacus) are mostly inhabitants of tropical America,
and their prevailing colour is green.  The Cockatoos (Plyctolophuzs), the Love-birds (A,4ajporinis), and the Lorikeets (Trich/oglossus) belong to the Australian province. The Lories (Lorius)
inhabit the East (fig. 194). The true Macaws (Araince) are
exclusively American; and the true Parrakeets (Pezoporince)
are exclusively confined to the eastern hemisphere, being especially characteristic of Australia.
In the next family of the Scansores are the Toucans (Rhamlhastida), characterised by having a bill which is always very




INSESSORES.                     495
large, longer than the head, and sometimes of comparatively
gigantic size. The mandibles are, however, to a very great
extent hollowed out into air-cells, so that the weight of the bill
is much less thali would be anticipated from its size. The
tongue is very long, notched at its side, or feathered with delicate lateral processes.  The Toucans live chiefly upon fruits,
and are all confined to the hotter regions of South America,
frequenting the forests in considerable flocks.
The Trogons have short and weak feet, a short triangular
bill, the gape bordered with strong bristles, and short wings.
The plumage is soft and loose, and generally of the most gorgeous description. They inhabit the most retired recesses of
the forests of the intertropical regions of both hemispheres,
and show many decided points of affinity to the Goat-suckers..ORDER VI. INSESSORES.-The sixth order of Birds is that of
the Insessores, or Perchers-often spoken of as the Passeres, or
" Passerine" Birds.  They are defined by Owen as follows:" Legs slender, short, with three toes before and one behind,
the two external toes united by a very short membrane" (fig.
195, A, B).
"The Perchers form the largest and by far the most numerous order of birds, but are the least easily recognisable by distinctive characters common to the whole group.  Their feet,
being more especially adapted to the delicate labours of nidification, have neither the webbed structure of those of the
Szwuimners, nor the robust strength and destructive talons which
characterise the feet of the Birds of Rapinze, nor yet the extended toes which enable the  Wadter to walk safely over
marshy soils and tread lightly on the floating leaves of aquatic
plants; but the toes are slender, flexible, and moderately
elongated, with long, pointed, and slightly-curved claws.' The Perchers in general have the females smaller and less
brilliantly coloured than the males; they always live in pairs,
build in trees, and display the greatest art in the construction
of their nests. The young are excluded in a blind and naked
state, and wholly dependent for subsistence during a certain
period on parental care.  The brain arrives in this order at its
greatest proportionate size; the organ of voice here attains its
greatest complexity, and all the characteristics of the bird, as
power of flight, melody of voice, and beauty of plumage, are
enjoyed in the highest perfection by one or other of the groups
of this extensive and varied order."
The structure of the feet, then, gives the definition of the
order, but the minor subdivisions are founded on the nature
of the beak; this organ.varying in form  according to the




496                MANUAL OF ZOOLOGY.
nature of the food, "which may be small or young birds, carrion, insects, fruit, seeds, vegetable juices, or of a mixed kind"
(Owen).
Fig. T95.-Insessores.  A, Foot of Yellow Wagtail; B, Foot of Water-ouzel; C,
Conirostral beak (Hawfinch); D, Dentirostral beak (Shrike); E, Tenuirostral beak
(Humming-bird); F, Fissirostral beak (Swift).
In accordance with the form of the beak, the Inzscssores have
been divided into four great sections or sub-orders, known as
the Conirostres, Dentirostres, Tenuirostres, and Fissiroslres.
Sub-order I. Conirostres.-In this section of the izscssores
the beak is strong and on the whole conical, broad at the-base
and tapering with considerable rapidity to the apex (fig. I95,
C). The upper mandible is not markedly toothed at its lower
margin. Good examples of the Conirostral type of beak are
to be found in the common Sparrow, Hawfinch, or Bullfinch.
The greater number of the  Conirostres are omnivorous; the
remainder are granivorous, or feed on seeds and grains. The
sub-order includes the families of the Horn-bills (Buceridre),
the Starlings (Sturnidce), the Crows (Corvidce), the Cross-bills
(Loxiad&e), and the Finches and Larks (Fringillidce).
In the Horn-bills the conirostral shape of the beak is masked,
partly by its being of very great size, and partly by the fact
that above the upper mandible is placed a hollow appendage




INSESSORES.                    497
like a kind of helmet.  Both the beak and the appendage
above it are rendered light by the presence of numerous aircells.  The Horn-bills are exclusively confined to the warm
countries of the eastern hemisphere, and are the largest of all
the Insessorial birds, sometimes attaining the size of a goose.
They live on fruits, and make their nests in the holes of trees.
The best-known species is the Rhinoceros Bird (Buceros Rhinoceros) of India and the Indian Archipelago.
The family of the Corvidce, or Crows, is an extremely extensive one, and includes a large number of very dissimilar-looking birds, all characterised by their long, strong, and compressed beaks, the tip of the upper mandible being slightly
hooked and more or less notched.  In this family are the
Jays (Garrulina); the true Crows or Corvinaz (comprising the
Rooks, Carrion-crows, Ravens, Jackdaws, Magpie, Chough,
&c.), and the Birds of Paradise (Paradiseidxe).  These last
differ considerably from the ordinary Corvidab but can hardly
be separated as a distinct family. They are amongst the most
beautiful of all birds, and are entirely confined to New Guinea
and the neighbouring islands.  They feed upon insects and
fruit, and are largely destroyed for the sake of their feathers.
The natives who capture them usually cut off their legs; hence
the notion formerly prevailed that the Birds of Paradise were
destitute of these limbs.  It is only the males which possess
the brilliant plumage, the females being soberly dressed; and
in accordance with this fact, it is stated that the Birds of Paradise are polygamous, being in this respect an exception to
almost the entire order of the Inzsessores.*
The family of the Starlings (Stuzrnidce) is not separated from
that of the Crows by any important characters. Besides our
common Starlings, it includes a number of other more or less
singular birds, of which the Bower-birds of Australia are perhaps the most peculiar. These curious birds have the habit
of building very elaborate bowers, often very beautifully constructed and of considerable size, in which they amuse themselves and apparently make love to one another. These bowers
are wholly independent of their nests, which they construct
elsewhere.
The last family of the Covziros/res is that of the Prinugillid'e,
comprising the Finches, Linnets, and Larks. In these birds
the bill is stout and conical, with a sharp apex, but not having
the upper mandible toothed. The toes are adapted for perching, and are provided with long and curved claws, that of
* The Humming-birds are thought to be polygamous, and this is certainly the case with the Whydah Finch (Vidiua).




498              MANUAL OF ZOOLOGY.
the hinder toe being usually longer than the rest. They are
almost all monogamous, and they build more or less elaborate
nests. In this family are the
true Finches (Fringilla), the
Sparrows (Pyrgita), the Linnets and Goldfinches (Car__"      ~ duelis), the Whydah Finches
i  ZZi       (Vizdua), the Grosbeaks (Coccot/hraustes), the Bullfinches
(Pyrrhula), and many others,
Lut their numbers are so great
that any further notice of
them is impossible here. It
Fig. 196. —Head of the common Bullfinch  may be mentioned, however,
(Pyrritula zu/lgaris), showing the Coni-           however,
rostral beak.                  that the Finches of the Old
World are represented in the
tropical parts of America by the Tanagers (Tanag-rince), remarkable for their brilliant colours.
The only remaining members of the  Caonirstrcs which
require notice are the Cross-bills (Loxiadw), which are sometimes placed with the Finches, and sometimes considered
as a separate family. In these birds the structure of the beak
is so peculiar that its Conirostral character is completely
masked, and it has been looked upon as a deformity. Both
mandibles, namely, cross one another towards the tip, giving
the entire bill a most'remarkable appearance.  In point of
fact, however, instead of being a deformity, the bill of the
Cross-bills is a beautiful natural adaptation, enabling the bird
with the greatest facility to tear in pieces the hard fir-cones, on
the seeds of which it feeds.
Sub-order 2. Dentirostres.-The birds in this section are
characterised by the fact that the upper mandible is provided
with a distinct notch in its lower margin near the tip (fig. I 95, D).
They all feed chiefly upon insects. This sub-order includes the
Shrikes (Laniizde), the Fly-catchers (Jizuscicapitce), the Thrushes
(Aieru/ide), the Tits (Parina), and the Warblers (Sy/viada).
The Aluscicapidce, including the numerous species of Flycatcher, are the most insectivorous of the.Delt/iros/res. The
gape is wide and bordered with bristles, and the legs are short
and weak. They are mostly sedentary, catching their prey
from a fixed point.
The Shrikes are highly predacious birds, which in many
respects make a close approach to the true Birds of Prey.
They feed, however, mostly upon worms and insects, and only
occasionally destroy small birds or mice.




INSESSORES.                    499
The great family of the Thrushes (MAerulaide) comprises not
only the true Thrushes, Field-fares, and Blackbirds, but a
number of exotic forms, of which the most familiar are the
Orioles, so well known for their brilliant plumage and their
beautifully-constructed nests.
In the SyiziadZ, amongst other forms, are the Wag-tails
(Motaci//ince) and the Pipits (Anthus), the Titmice, Robins,
Hedge-sparrow, Stone-chat, Redstarts, and other well-known
British birds. The Titmice (Paring) are often placed in the
sub-order of the Conirostres. The Nightingale also belongs to
this family.
Sub-order 3. Tenuirostres.-The members of this sub-order
are characterised by the possession of a long and slender beak,
gradually tapering to a point (fig. I95, E). The toes are very
long and slender, the hind-toe or hallux especially so. Most
of the Tenuirostral birds live upon insects, and some of these
present a near resemblance in many of their characters to the
Dentirostres, but it is asserted that some live partially or wholly
on the juices of flowers.
The chief families of the Tenuirosfres are the Creepers
(Certiide), the Honey-eaters (Me/ip/hagide), the Hummingbirds (ir'ochziZide), the Sun-birds (Promerop'id)e),  and  the
Hoopoes (Uprpi'de), of which only the Creepers and Humming-birds need any further notice.
The family Cer-tlidz includes several familiar British birds,
such as the little brown Creeper (Certhia familiaris), the
Nuthatch (Sitta Europcea), and the Wrens (T/rogl/odytes). With
these are a number of exotic forms, of which the singular
Lyre-birds of Australia are the most remarkable.
The family of the Trochilidie, or Humming-birds, includes the
most fragile and brightly coloured of all the birds, some not
weighing more than twenty grains when alive, and many
exhibiting the most brilliant play of metallic colours. The
Humming-birds are pre-eminently South American, but extend
northwards as far even as the southern portions of Canada.
The bill (fig. 195, E) is always very long and slender, as are
the toes also.  The tongue is bifid and tubular, and appears to
be used either to catch insects within the corollas of flowers,
or to suck up the juices of the flowers themselves. The plumage of the males is always brilliant, with metallic reflections,
that of the female generally sombre. The legs are short and
weak, but the wings are proportionately very long, and the
flight is exceedingly rapid.
The Sun-birds represent in the Old World the Hummingbirds of the western hemisphere, and the Australian Honey



500             MANUAL OF ZOOLOGY.
eaters show also many points of resemblance to the -Zrochilide.
Sub-order 4. Fissirostres.-In this sub-order of the Insessores
the beak is short but remarkably wide in its gape (fig. I95, F),
and the opening of the bill is fenced in by a number of bristles
(vibrissae). This arrangement is in accordance with the habits
of the Fissirostres, the typical members of which live upon
insects and take their prey upon the wing. The most typical
Fissirostral birds, in fact, such as the Swallows and Goat-suckers,
fly about with their mouths widely opened; and the insects
which they catch in this way are prevented from escaping
partly by the bristles which border the gape, and partly by a
viscid saliva which covers the tongue and inside of the mouth.
The typical Fissirostres, characterised by this structure of the
beak, comprise three families — the Swallows and Martins
(HirundinidAe), the Swifts (Cypse/id(ej, and the Goat-suckers
(Caprimlulgidce). These three families differ in many important
respects from one another, but it would be inconvenient to
separate them here. The Swifts, especially, are remarkable
for the peculiarity that whilst the hallux is present, it is turned
forwards along with the three anterior toes. The Goat-suckers,
again, hunt their prey by night, and they are provided with
the large eyes and thick soft plumage of all nocturnal birds.
Besides the above, there remain the two families of the Kingfishers and Bee-eaters, which are generally placed amongst the
Fissirostres, though in very many respects the arrangement
appears to be an unnatural one.  These families are characterised by their stronger and longer bills, and by having the
external toe nearly as long as the middle one, to which it is
united nearly as far as the penultimate joint. In consequence
of this peculiar conformation of the toes, these families were
united by Cuvier into a single group under the name of
SyndacIyli.
The Caprimiuizgide are intermediate between the Owls and
the Passerine Birds. Their plumage is lax and soft, and they
have a hawking flight. The eyes and ears are large, the feet
short and weak, and the gape of enormous size and bordered
by vibrissoe.  Amongst the more remarkable members of the
family may be mentioned the Whip-poor-will (Antrosfomus
vociferts) of North America, the More-pork (-odai/glus Cuvieri)
of Australia, and the extraordinary Guacharo Bird (Sleatornis
Caripensis) of the valley of Caripe in the West Indies.
The Bee-eaters (Meropid(e) live upon insects, chiefly upon
various species of bees and wasps; but the King-fishers live
upon small fish, which they capture by dashing into the water.




RAPTORES.                      50o
The common King-fisher (Alcedo ispida) is a somewhat rare
native of Britain, and is perhaps the most beautiful of British
birds. Some exotic King-fishers are of large size, and one of
the most remarkable of them is the Laughing Jackass (Dacelo
gigas) of Australia, so called from its extraordinary song, resembling a prolonged hysterical laugh. A very beautiful species
is the Belted King-fisher (Ceryle alcyon) of North America.
The Bee-eaters are found chiefly in the warmer regions of the
Old World, and their place is taken in America by the Motmot;s (MAamotus).
CHAPTER LXX.
RAPTORES ANiD SA URUI'E.
ORDER VII. RAPTORES.-All the members of this order are
characterised by the shape of the bill, which is "strong,
curved, sharp-edged, and sharp pointed, often armed with a
lateral tooth" (Owen). The upper- mandible is the longest
(fig. I97, B), and is strongly hooked at the tip. The body is
very muscular; the legs are robust, short, with three toes in
front and one behind, all armed with long, curved, crooked
claws or talons (fig. I97, A); the wings are commonly pointed,
A                    B
Fig. 97. —A, Foot of the Peregrine Falcon: B, Head of Buzzard.
and of considerable size, and the flight is usually rapid and
powerful. The Birds of Rapine are monogamous, and the
female is larger than the male. They build their nests generally
in lofty and inaccessible situations, and rarely lay more than
four eggs, from which the young are liberated in a naked and
helpless condition.




502              MANUAL OF ZOOLOGY.
The order Raptores is divided into two great sections-the
Nocturnal Birds of Prey, which hunt by night, and have the
eyes directed forwards; and the D)iurnal Raptores, which
catch their prey by day, and have the eyes directed laterally.
The section of the 2Voturnal Raptores includes the single
family of the Strigidxe, or Owls. In these birds the eyes are
large, and are directed forwards. The plumage is exceedingly
loose and soft, so that their flight (even when they are of large
size) is almost noiseless; and it is generally spotted or barred with
different shades of grey, brown, or yellow. The beak is short,
strongly hooked, furnished with bristles-at its base, and having the
nostrils pierced in a membranous "cere" at the base of the upper
mandible. The cranial bones are highly pneumatic, and the head
is therefore of large size. The feathers of the face usually form
an incomplete or complete "disc" or circle round each eye
(fig. I98, B), and a circle of plumes is likewise placed round
A
Fig. i98.-A, Foot of tawny Owl (Ulula stridula); B, Head of white Owl
(Strixf Z-t ammIea).
each external meatus auditorius. Besides this auricular circle
of feathers, the external meatus of the ear is likewise protected
by a fold of skin. The legs are short and strong, and are furnished with four toes, all armed with strong crooked talons.
The outer toe can be turned backwards, so that the foot has
some resemblance to that of the Scansores.  The tarso-metatarsus is densely feathered (fig. I98, A), and the plumes sometimes extend to the extremities of the toes. The cesophagus is
not dilated into a crop; and the indigestible portions of the food
are rejected by regurgitation from the stomach in the form of
small pellets. The Owls hunt their prey in the twilight or on
moonlight nights, and they live mostly upon field-mice and
small birds, though they will also eat insects or frogs.




RAPTORES.                     503
The section of the DiurnaZRaptores includes the two groups
of the Acciipitrhinc (Falcons, Hawks, and Eagles), and the V1z1turideL, or Vultures.  The eyes in this section are much smaller
than in the preceding, and are placed laterally; and the plumage is not soft. As regards their power of flight, they show
a decided advance upon the Nocturnal Birds of Prey. The
wings are long and pointed; the sternal keel and pectoral
muscles are greatly developed; and many of the members of
this section exhibit a more rapid power of locomotion than is
seen in any other division of the animal kingdom. The bill is
long and strong, with a large "cere" at the base of the upper
mandible, in which the nostrils are pierced. The tarso-metatarsus and toes are usually covered by scales, and are rarely
feathered.  Lastly, the cesophagus is dilated into a capacious
crop, the gizzard is thin, the intestinal caeca are rudimentary,
and the intestinal canal is generally short and wide.
In the Accipi/rinue or Falconidre (fig. i97, B) the head and
neck are always clothed with feathers, and the eyes are more
or less sunk in the head, and provided with a superciliary ridge
or eyebrow.  It is to a great extent to the presence of this
ridge that many of these birds owe their fearless and bold expression. In this family are the Falcons, Hawks, Buzzards,
Kites, Harriers, and Eagles, most of which are so well known
that any description is unnecessary.
Fig I99.-Head of Vulture (.Weolthron percnol/erus)
In the Vulturidce (fig. I99) the eyes are destitute of an eyeblrow, and the head and neck are frequently naked, or covered




504              MANUAL OF ZOOLOGY.
only by a short down. In this family are the Bearded Vultures, the true Vultures, and the Condor.
The Bearded Vulture, or Lammergeyer (Gypados barbatus),
is the largest of European birds, measuring from nine to ten
feet from the tip of one wing to that of the other. This powerful and rapacious bird inhabits the mountain-ranges of the
south of Europe and the west of Asia, and feeds chiefly on
goats, lambs, and deer, which it kills by precipitating down
steep declivities. It is distinguished from the true Vultures by
the fact that the head and neck are feathered.
The true Vultures have the head, and generally the neck
also, naked, or covered with down.  They are filthy and disgusting birds, which live almost entirely upon carrion, a peculiarity which renders them of great service in hot climates.
The Secretary Vultures (Seryenlarius) are distinguished by
their very long and slender legs, unfeathered tarso-metatarsus,
and long wings armed with blunt spines. They are found in
Africa and the Philippine Islands, and live upon Serpents and
other Reptiles.
The last member of this section is the gigantic Condor
(Sarcorhampus gryphus).  This enormous bird has a stretch of
wing of over fourteen feet, and is usually seen soaring in majestic circles at a great elevation in the air, rising, it is said,
to a height of over twenty thousand feet.  It inhabits the lofty
mountain-ranges of the Andes, and lays its eggs at a height of
from ten to fifteen thousand feet. It differs from the Vultures
of the Old World chiefly in possessing a large fleshy protuberance or caruncle above the base of the beak.
Fig, 2oo. -Arc4ieoIteryx macrura, showing tail and tail-feathers, with detached ibone.




DISTRIBUTION OF AVES IN TIME.             505
ORDER VIII. SAURUR. — This order includes only the
extinct bird, the Ar4cheopteryx macrura, a single specimen of
which-and that but a fragmentary one-has been discovered
in the Lithographic Slates of Solenhofen (Upper Oolites).
This extraordinary bird appears to have been about as big as a
Rook; but it differs from all known birds in having two free
claws belonging to the wing, and in having a long lizard-like
tail, longer than the body, and composed of separate vertebrae.
The tail was destitute of any ploughshare-bone, and each vertebra carried a single pair of quills.  The metacarpal bones,
also, were not anchylosed together as they are in all other
known birds, living or extinct.
CHAPTER  LXXI.
DISTRIBUTION  OF AVES IN  TIME.
As regards the geological distribution of Birds, there are many
reasons why we should be cautious in reasoning upon merely
negative evidence, and more than ordinarily careful not to
infer the non-existence of birds during any particular geological
epoch, simply because we can find no positive evidence for
their presence. As Sir Charles Lyell has well remarked, "the
powers of flight possessed by most birds would insure them
against perishing by numerous casualties to which quadrupeds
are exposed during floods;" and " if they chance to be drowned,
or to die when swimming on water, it will scarcely ever happen
that they will be submerged so as to become preserved in
sedimentary deposits," since, from the lightness of the bones,
the carcass would remain long afloat, and would be liable to
be devoured by predacious animals.  As, with a few utterly
trivial exceptions, all the deposits in which fossils are found
have been laid down in water, and more especially as they are
for the most part marine, these considerations put forward by
Sir Charles Lyell afford obvious ground against the anticipation that the remains of birds should be either of frequent
occurrence or of a perfect character in any of the fossiliferous
rocks. In accordance with these considerations, as a matter
of fact, most' of the known remains of birds are either fragmentary or belong to forms which were organised to live a terrestrial life, and were not organised for flight.
The earliest remains which have been generally referred to




go6              MANUAL OF ZOOLOGY.
birds are in the form of footprints impressed upon certain
sandstones in the valley of the. Connecticut River in the
United States. These sandstones are almost certainly Triassic; and if the ornithic character of these footprints be admitted, then Birds date their existence from the commencement of the Mesozoic period, and, for anything we know
to the contrary, may have existed during the Palaeozoic
epoch.
The evidence as to the ornithic character of the footprints
in the American Trias is as follows:Firstly, The tracks are, beyond all question, those of a biped
-rthat is to say, of an animal which walked upon two legs.
No living animals walk habitually upon two legs except Man
and Birds, and therefore there is a primna facie presumption
that the authors of these prints were birds.
Secondly, The impressions are mostly tridactylous-that is
to say, formed by an animal with three toes on each foot, as is
the case in many Waders and most Cursorial birds.
Thirdly, The impressions of the toes show the same numerical progression in the number of phalanges as exists in living
birds-that is to say, the innermost of the anterior toes has
three phalanges, the middle one has four, and the outermost
toe has five phalanges.
Taking this evidence collectively, it would have seemed, till
lately, tolerably certain that these impressions were formed by
Birds.  We must not, however, lose sight of the possibility
that these impressions may have been formed by Reptiles
more bird-like in their characters than any of the living forms
with which we are acquainted. The recent researches of
Huxley, Cope, and others, go to show that the Dinosaugrian
Reptiles possessed the power of walking temporarily or permanently on the hind-legs, and many curious affinities to the
true Birds have been pointed out. It is therefore by no means
impossible that these footprints of the Connecticut valley are
truly Reptilian.The size and other characters of the above-mentioned impressions vary much, and they have certainly been produced
by several different animals. In the largest hitherto discovered, each footprint is twenty-two inches long, and twelve
inches wide, showing that the feet were four times as large as
those of the African Ostrich.  The animal, therefore, Nlwhich
* The occurrence of manyfozlr-foel impressions on these same sandstones,
and the further discovery of.the bones of Dinosaurian Reptiles in the same
beds, have rendered the Reptilian nature of these footprints almost certain;
but some may possibly have been formed by Birds.




DISTRIBUTION OF AVES IN TIME.            507
produced these impressions-whether Avian or Reptilian —
must have been of gigantic size.
The first unmistakable remains of a bird have been found
in the Solenhofen Slates of Bavaria, of the age of the Upper
Oolites. A single unique specimen, consisting of bones and
feathers, but unfortunately without the skull, is all that has
hitherto been discovered; and it has been named the Archeopteryx macrura.  The characters of this singular and aberrant
bird, which alone constitutes the order Saurura?, have been
already given, and need not be repeated here.
Other doubtful remains of birds have been alleged to occur
in the Mesozoic series, but many of these certainly belong in
reality to Pterodactyles. In the Cretaceous rocks, however, of
the United States, occur the bones of several Wading Birds
(Laornis, Telmatornis, and Palaeotringa).
In the Tertiary rocks, however, there are, comparatively
speaking, many remains of birds.  In the Eocene rocks of
France has been found a large bird, as big as an Ostrich, the
so-called Gastornis Parisiensis; and in England, in the same
formation, we have a small Vulture (Lithornis vulturintus), and
a King-fisher (Halcyornis tolia2icus). In the Eocene of Glaris,
in Switzerland, occurs also the oldest known Insessorial or
Passerine bird, the Protornis Glarisiensis, which was about as
big as a lark.
Numerous remains of birds have likewise been found in the
Miocene and Pliocene deposits.  Amongst these we have
Parrots, Trogons, Secretary Birds, Petrels, Cranes, Guillemots, &c.  With the exception, however, of the Mesozoic
Archeopteryx, by far the most remarkable remains of birds
have been found in the Post-tertiary or Pleistocene deposits.
All the remains now alluded to are those of gigantic wingless
birds; and it is worthy of notice that they are exclusively
found in regions now tenanted by smaller wingless birds,
whilst there is reason to believe that some of them have been
in existence during the human period. Most of the remains
in question have been found in New Zealand, where there
have been obtained the bones of several species of large wingless birds, referred by Owen to the genera 9Dinornis, PalapteOyx, and Aptornis.  The Dinornis gianlleus must have been
ohe of the most gigantic of the whole class of birds, the tibia
measuring upwards of a yard in length, and the skeleton indicating a bird which stood at least ten feet in height. In
another species, the Dinornis elephantopus, the " framework of
the skeleton is the most massive of any in the whole class of
birds," and "the toe-bones almost rival those of the Elephant"
23




508             MANUAL OF ZOOLOGY.
(Owen).  The feet were furnished with three anterior toes,
and are of interest as presenting us with an undoubted bird
big enough to produce the largest of the footprints of the
Triassic Sandstones of Connecticut. There is reason to believe from the traditions of the Maories that the Dinornis was
living at no very remote period, and that it has been exterminated by man.
In Madagascar, bones have been discovered of a bird as
large as, or larger than, the Dinornis giganfteus, which has been
described under the name of the zEpiornis maximus. With
the bones have been found eggs measuring from thirteen to
fourteen inches in diameter, and computed to be as big as
three ostrich-eggs, or one hundred and forty-eight hens' eggs.
Unlike New Zealand, where there is the Apteryx, Madagascar
itself has no living wingless birds; but in the neighbouring
island of Mauritius, the Dodo has been exterminated less than
three hundred years ago; and the little island of Rodriguez, ill
the same geographical province, has in a similar period lost
the wingless Solitaire (Pezophaps4




DIVISION III. lAiAMMALIA.
CHAPTER LXXII.
GENERAL CHARACTERS OF THE MAMMALIA.
THE last and highest class of the Vertebra/a, that of the Afammalia, may be shortly defined as including Vertebrate animals
in which some part or other of the integument is always providea
with hairs at some time of life; and the young are nourished, for
a longer or shorter time, by means of a special fluid-the milksecreted by special glands-the mammary glands.  These two
characters are of themselves sufficient broadly to separate the
Mammals from all other classes of the Vertebrate sub-kingdom. In addition, however, to these two leading peculiarities,
the Mammals exhibit the following other characters of scarcely
less importance:i. The skull articulates with the vertebral column by means
of a double articulation, the occipital bone carrying two condyles, in place of the single condyle of the Reptiles and Birds.
2. The lower jaw or mandible consists of two halves or
rami, united anteriorly by a symphysis, but not necessarily
anchylosed; but these are eaclh composed of a single piece,
instead of being complex and consisting of several pieces, as
in the Reptiles and Birds.  Further, the lower jaw always
articulates directly with the squamosal element of the skull;
and is never united to an os quadraturn, as in the Saurojsida.
3. The two hemispheres of the cerebral mass, or brain proper,
are united together by a more or less extensively developed
"corpus callosum" or commissure.
4. The heart consists-as in Birds-of four cavities or
chambers, two auricles and two ventricles. The right and left
sides of the heart are completely separated from one another,
and there is no communication between the pulmonary and
systemic circulations.  The red blood-corpuscles are nonnucleated, and, with the exception of the Cazmelidce, they are
circular biconcave discs.  There is only one aorta-the leftwhich turns over the left bronchus, and not over the right, as
it does in Birds.




510             MANUAL OF ZOOLOGY.
5. The cavities of the thorax and abdomen are completely
separated from one another by a muscular partition-the diaphragm or midriff.
6. The respiratory organs are in the form of two lungs
placed in the thorax, but none of the bronchi end in air-receptacles, distributed through the body, as in Birds.
7. The embryo mammal is invariably enveloped in an amnion, and an allantois is never wanting. The allantois, however, either disappears at an early period of life, or it develops
the structure knbwn as the "placenta."  The placenta is a
vascular organ which serves as a means of communication
between the parent and the foetus, but it will be noticed more
particularly hereafter.
8. In no Mammal do the visceral arches and clefts of the
embryo ever carry branchike, as they do in the Fishes and
Amphibians.
These are the essential characters which distinguish the
AMammalia as a class, but it will be necessary to consider these,
and some other points, in a more detailed manner.
In the first place, with regard to the osteology of the Mammals, the following points should be noticed:With the exception of the Whales and Dolphins (Cetacea),
and the Dugongs and Manatees (Sirenia), the vertebral column
is divisible into the same regions as in man-namely, into a
cervical, dorsal, lumbar, sacral, and caudal or coccygeal region
(see fig. I26). In the Cetacea and Sirenia the dorsal region
of the spine is followed by a number of vertebra which compose the hinder extremity of the body, but which cannot be
separated into lumbar, sacral, and caudal vertebrae.
In spite of the great difference which is observable in the
length of the neck in different Mammals, the number of
ivertebrae in the cervical region is extraordinarily constant,
being almost invariably seven, as in man.  In this respect
there is no difference between the Whale and the Giraffe.
The only exceptions to this law are the Manatus azstralis,
one of the Sea-cows, which has usually six cervical vertebre,
and the three-toed Sloth (Bradypus hicizdctyizs), which is commonly regarded as possessing nine, though competent anatomists would refer the posterior two of these to the dorsal
region.
The dorsal vertebrae are mostly thirteen in number, but they
vary fromn ten to twenty-four. In Man there are twelve, in one
of the Armadillos only ten, and in the three-fingered Sloth the
maximum is attained. The lumbar vertebrae are usually six
or seven in number, rarely fewer than four.  In Man they are




CHARACTERS OF MAMMALIA.                  511
five in number, and they are reduced to two in the two-toed
Sloth, one of the Ant-eaters, and the Duck-mole.
The first vertebra, or atlas, always bears two articular cavities for the reception of the two condyles of the occipital bone;
and the second vertebra, or axis, usually has an "odontoid"
process on which the head rotates. In the true Whales, however, in which the cervical vertebrae are anchylosed together
to a greater or less extent, and the neck is immovable, the
odontoid process is also wanting.
In almost all Mammals the spinous processes of the dorsal
vertebrae are very largely developed for the attachment of the
structure which is known as the ligamentum nuchk.'This is a
great band of elastic fibrous tissue, which is attached in front
to the occipital bone and spinous processes of the cervical
vertebrae, and which relieves the muscles of the task of supporting the head, in those Mammals which progress with the body
in a horizontal position.  The development of the ligamentum
nuckhe is consequently, as a rule, proportionate to the size
of the head and the length of the neck. In Whales no such
apparatus is necessary, owing to the fixation of the cervical
vertebra by anchylosis; and in Man, who walks erect, the
ligamzentum   nuch/e can hardly be said to exist as a distinct
structure, being merely represented by a band of fascia.
The number of lumbar and sacral vertebrae, as we have seen,
varies in different Mammals; but ordinarily some of the vertebrae are anchylosed into a single bone, and have the iliac bones
abutting against them, thus constituting the " sacrum" of
human anatomists. In the Cetacea and Sirenia, in which the
hind-limbs are wanting, and the pelvis rudimentary, there is no' sacrum.5"
The thoracic cavity or chest-in Mammals is always enclosed
by a series of ribs, the number of which varies with that of the
dorsal vertebrae. In most cases each rib articulates by its
head with the bodies of two vertebrae, and by its tubercle with
the transverse process of one of these vertebrae (the lower one).
In the Afonolremata (e.g., the Duck-mole), the ribs articulate
with the body of the vertebra only; and in the Whales, the
hindermost of the ribs, or all of them, articulate with the transverse processes only, and not with the centra at all.
There are usually no bony pieces uniting the ribs with the
sternum or breast-bone in front, as in Birds; but the so-called
"sternal ribs" of Azes are represented by the "costal cartilages" of the Mammals. In some cases, however, the cartilages of the ribs do become ossified and constitute sternal ribs.
Sometimes, as in the Armadillos, there is a joint between the




512             MANUAL OF ZOOLOGY.
vertebral rib and costal cartilage.  More rarely, as in the
Afonotremes, an intermediate piece is found between the vertebral and costal portions of the rib. Only the anterior ribs
reach the sternum, and these are called the "true" ribs; the
posterior ribs, which fall short of the breast-bone, being known
as the " false " ribs.
The sternum or breast-bone is formed of several pieces placed
one behind the other, but usually anchylosed together to form
a single bone. It is placed upon the ventral surface of the
body, and is united with the vertebral column by the ribs and
their cartilages.  It is generally a long and narrow bone,'but
in the Cetdcea it is broad. It is only in some burrowing animals (such as the Moles) and in the true flying Mammals (the
Bats), that the sternum is provided with any ridge or keel for
the attachment of the pectoral muscles, as it is in Birds. The
sternum is primitively composed of three pieces, an anterior
piece or pjresternum, a middle piece or vmesosternum, and a
posterior piece or xiph/isternum. The praesternum is the
" manubrium sterni " of human anatomy, and is the portion of
the sternum which lies in front of the attachment of the second
pair of ribs. All the other ribs are connected with the mesosternum. The xiphisternum  is the "xiphoid cartilage" of
human anatomy, and it commonly remains throughout life
more or less unossified. In the Monotremes there is a Tshaped bone above or in front of the prmesternum, but this is
probably to be regarded as belonging to the shoulder-girdle,
and as representinlg the "episternum" or " interclavicle" of
the Reptiles.
The normal number of limbs in the Mammalia is four, two
anterior and two posterior; and hence they are often spoken
of as " quadrupeds," though all the limbs are not universally
present, and other animals have four limbs as well. The anterior limbs are not known to be wanting in any Mammal, but
the posterior limbs are absent in the Cetacea and Sirenia.
As regards the structure of the anterior limb, the chief points
to be noticed concern the means by which it is connected with
the trunk. The scapula or shoulder-blade is never absent, and
it is in the form of a broad flat bone, applied to the outer
aspect of the ribs; and much more developed than in the Bir(ds.
The coracoid bone, which forms such a marked feature in tlb,
scapular arch of Aves, is fused with the scapula, and only articulates with the sternum in the Duck-mole and Echidna (Mlonotremata). In all other Mammals the coracoid forms merely a
process of the scapula, and does not reach the top of the breastbone. The collar-bones or clavicles never unite in any Mamo




CHARACTERS OF MAMMALIA.                513
mal to form a " furculum," as in Birds; but in the Monotremes
they unite with an " interclavicle" placed in front of the sternum. The clavicles, in point of fact, are not present in a welldeveloped form in any Mammals except in those which use the
anterior limbs in flight, in digging, or in prehension. The
Cetacca, the Hoofed Quadrupeds (Ungulata), and some of the
Edentala, have no clavicles.' Most of the Carnivora and some
Rodents possess a clavicle, but this is imperfect, and does not
articulate with the top of the sternum.  The Insectivorous
Mammals, many of the Rodents, the Bats, and all the Quadrumana, have (with man) a perfect clavicle articulating with the
anterior end of the sternum.
The humerus, or long bone of the upper arm (brachiurn), is
never wanting, but is extremely short in the Whales, in which
the anterior limbs are converted into swimming-paddles. In
many Mamrunals, as in the Monkeys, and Felidae (constituting
the most typical group of the Carnivora), the median nerve and
brachial or ulnar artery are protected on their way down the
arm by a canal placed a little above the elbow, and formed by
a process-the "supra-condyloid" process'-which is sometimes present in man as an abnormality.
In the fore-arm of all Mammals the ulna and radius are recognisable, but they are not necessarily distinct; and the radius;
as being the bone which mainly supports the hand, is the only
one'which is always well developed, the ulna being often rudimentary. In the Cetacea the ulna and radius are anchylosed
together; and in most of the Hoofed Quadrupeds they are
anchylosed towards their distal extremities.  In the flying
Mammals or Bats alone is the ulna ever altogether absent.
The fore-arm attains its greatest perfection in man, in whom
the radius can rotate upon the ulna, so as to allow the back of'
the hand to be placed upwards or downwards, these movements
being known respectively as "pronation" and "supination."
In the Monkeys only is there any approach to this power of
rotation.
The fore-arm is succeeded by the small bones which compose the wrist or "carpus."  These are eight in number in
man, but vary in different Mammals from five to eleven.
The metacarpus in man and in most Mammals consists of
five cylindrical bones, articulating proximally with the carpus,
and distally with the phalanges of the fingers. The most remarkable modification of this normal state of things occurs in
the Ruminants and in the Horse. In the Ruminants, in which
the foot is cleft, and consists of two toes only, there are two
metacarpal bones in the embryo; but these are anchylosed to



514               MANUAI, OF ZOOLOGY.
gether in the adult; and form a single mass which is known
as the " canon-bone" (fig. 201, ca). In the Horse, in which the
foot consists of no more than a single digit, there is only a
single metacarpal bone, on each side of which are two little bony
spines — the so-called "splintbones "   which  are attached
~/1/'!   superiorly to the carpus.'These
are to be regarded as rudimentary metacarpals; but by Cuvier
"r -     they were looked upon as imr —-    perfect fingers.  In most of the
other Ungulates there are at
C —.       least three metacarpals, and in
the Elephants there are five.
The normal number of digits
is five, but they vary from  one..p              to five.  The middle finger is
c,' __.aa  ia    the longest and most persistent
of the digits of the fore-limb;
and in the Horse it is the only
i  one which is left (fig. 2o0, A).
The thumb is very frequently
ON i ~5Js   absent. In the Ruminants there
are only two fingers which are
functionally useful, these carrying the hoofs.  In most RumiA  B      nants, however, there are two
rudimentary  and  functionally
Fig. 201.-A, Fore-leg of the Horse: r  useless digits in addition.
Radius; c Carpus; car Canon-bone,;.
Splint-bone; a Fi:rst phalanx or " great    Normally each digit has three
pastern;" b Second phalanx or "small  phalanges, except the thumb,
pastern;" c Ungual phalanx or "coffinbone."' B, Fore-limb of a Deer; r  which has only two.   In the
Radius; c Carpus; ca Canon-bone; s  Whales and Dolphins (Cetacc),
Supplementary toe.
in which the anterior limbs form
swimming-paddles, very like those of the Jchl/hyosaurtts and
Plesiosaurus, the  phalanges are  considerably increased  in
number as they are in those Reptiles.  In all the Mammalia,
too, except the Cetacea, it is the rule that the terminal phalanx
in each digit should carry a nail, claw, or hoof.
The power of opposing the thumb to the other digits of the
hand is found only in Man, and in a considerable number of
the Quadruzmna, but never so perfectly developed as in Man.
In Man only does this power attain its full perfection, and it
constitutes one of the most striking of the merely anatomical
peculiarities by which Man is separated from  the Monkeys.




CHARACTERS OF MAMMALIA.                 5 15
As, however, this feature is purely adaptive, and is'really to be
regarded as of extremely small physiological value, we ought
to learn from this that the difference between Man and the
Quadruzmana is to be sought in the mental powers-of each, and
not in any merely structural character.
Whilst the anterior limbs are never absent in any Man-m l,
the posterior limbs are occasionally wholly wanting, as in the
Cetacea and Sirenia.  Generally speaking, however, the posterior limbs are present, and the pelvic arch has much the same
structure as in Man. The two halves of the pelvis-the ossa
innominata-consist each of three pieces in the embryo-viz.,
the ilium, ischium, and pubes, which meet to form the cupshaped cavity known as the "acetabulum," with which the
head of the thigh-bone articulates. In the adult Mammal
these three bones are anchylosed together, and the two ossa
innominata unite in front by means of a symphysis pubis, constituted either by a cartilaginous union (synchondrosis), or by
merely ligamentous attachment. In some Mammals, however,
such as the Mole, and many of the Bats, the pubic bones remain disunited during life. As a rule, also, the ossa innominata are firmly united with the vertebral column. In the Cetaceans, in which the hind-limbs are wanting, and there is no
sacrum, the innominate bones are rudimentary, and are not
attached in any way to the spine.
The only other bones which are ever connected with the
pelvis are two small bones which are directed upwards from
the brim of the pelvic cavity in Marsupials and Monotremes.
These are the so-called " Marsupial bones," regarded generally
as not forming parts of the skeleton properly so called, but
as being ossifications of the internal tendons of the "external
oblique " muscles of the abdomen (fig. 2o4).
In those Mammals which possess hind-limbs, the normal
composition of the member is of the following parts: —I. A
thigh-bone or femur; 2. Two bones forming the shank, and
known as the tibia and fibula; 3. A number of small bones
constituting the ankle or tarsus; 4. Tlle "root" of the foot,
made up of the "metatarsus;" 5. The phalanges of the toes
(see fig. 128).
The thigh-bone or femur articulates with the pelvis, usually
at a very open angle. In Man it is distinguished by being the
longest bone of the body, and by having the axis of its shaft
nearly parallel to that of the vertebral column. In most
Mammals the femur is relatively shorter, and the axis of its
shaft deviates considerably from that of the spine, being some.
times at right angles, or even at an acute anl.d.




i56             MANUAL OF ZOOLOGY.
Of the bones of the leg proper the tibia corresponds to the
radius in the fore-limb, as shown by its carrying the tarsus;
and the fibula is the representative of the ulna. The articulation between the tibia and fibula on the one hand, and the
femur on the other, constitutes the " knee-joint," which is usually defended in front by the "knee-pan" or patella, a large
sesamoid bone developed in the tendons of the great extensor
muscles of the thigh. The patella is of small size in the Carnizorla, but does not appear to be wanting in any except the
Marsupials. In many cases the tibia and fibula are anchylosed
towards their distal extremities.  In the Horse the fibula has
much the same character as in Birds, being a long splint-like
bone which only extends about half-way down the tibia. In
the Ruminants the reverse of this obtains, the upper half of the
fibula being absent, and only the lower half present.
The tibia articulates with the tarsus, consisting in Man of
seven bones, but varying in different Mammals from four to
nine.
The foot consists normally of five toes connected with the
tarsus by means of five metatarsal bones, which closely resemble the metacarpals. In the Ruminants there are only two
metatarsals, and these are anchylosed in the adult, and carry
two toes. In the Horse there is only one metatarsal supporting a single toe. As a rule, the number of digits in the hindlimb or foot is the same as that in the fore-limb or hand; but
this is not always the case. In the Lions, Tigers, Cats, and
Dogs, the posterior limb carries only four toes, the innermost
toe or hallux being wanting. In the Quadriumana, again, all
the five toes are generally present, but the four outer toes are
much longer than in Man, and the hallux is shorter than the
other toes, and often opposable to them, so that the foot forms
a kind of posterior hand. The hallux is also not uncommonly
opposable in other cases.
The cranial bones are invariably connected with one another
by sutures, and in no other examples than the Monotremes
are these sutures obliterated in the adult.  The differences of
opinion which are entertained as to the fundamental structure
of the skull are so enormous, that it will be best not to attempt
here any detailed description of the skull of the Mammalia,
more especially as there is as yet no universal agreement even
as to the nomenclature to be employed. It is sufficient to remember that the skull is composed of a series of bony segments,
which are usually regarded as modified vertebrae.  The occipital bone carries two condyles for articulation with the first
cervical vertebra. The lower jaw is composed of two halves




CIHARACTERS OF MAMMIALIA.               517
or rami, which are distinct from another in the embryo, and
may or may not be anchylosed together in the adult. However this may be, in no Mammal is the ramus of the lower jaw
composed of several pieces, as it is in Birds and Reptiles, nor
does it articulate with the skull by the intervention of an os
quadratum. On the other hand, each ramus of the lower jaw
in the Mammals is composed of only a single piece, and articulates with the squamosal element of the skull, or, in other
words, with the squamous portion' of the temporal bone.
Teeth are present in the great majority of Mammals; but
they are only present in the embryo of the whalebone Whales,
and are entirely absent in the genera Ec/hidina, Mfanis, and
AMjrmecophara. In the Duck-mole (Ornithorhynchus) the teeth
are horny, and the same was the case in the extinct Rhytina
amongst the Sirenia.  In all other Mammals the teeth have
their ordinary structure of dentine, enamel, and crusta petrosa,
these elements being variously disposed in different cases. In
no Mammals are the teeth ever anchylosed with the jaw; and
in all, the teeth are implanted into distinct sockets or alveoli,
which, however, are very imperfect in some of the Cetacea.
Many Mammals have only a single set of teeth throughout
life, and these are termed by Owen "monophyodont."  In
most cases, however, the first set of teeth-called the " milk"
or " deciduous " teeth-is replaced in the course of growth by
a second set of "permanent" teeth. The deciduous and permanent sets of teeth do not necessarily correspond to one
another; but no Mammal has ever more than these two sets.
The Mammals with two sets of teeth are called by Owen
"diphyodont."
In Man and in many other Mammals the teeth are divisible
into four distinct groups, which differ from one another in
position, appearance, and function; and which are known
respectively as the incisors, canines, prcemolars, and molars
(fig. 202).  "Those teeth which are implanted in the premaxillary bones, and in the corresponding part of the lower
jaw, are called'incisors,' whatever be their shape or size.
The tooth in the maxillary bone which is situated at or near
to the suture with the prxmaxillary, is the' canine,' as is also
that tooth in the lower jaw which, in opposing it, passes in
front of its crown when the mouth is closed. The other teeth
of the first set are the' deciduous molars;' the teeth which
displace and succeed them  vertically are the'praemolars;'
the more posterior teeth, which are not displaced by vertical
successoI,, are the'molars' properly so called."- (Owen.)
The deciduous dentition, therefore, of a diphyodont Mammal




518             MANUAL OF ZOOLOGY.
consists of only three kinds of teeth-incisors, canines, and
molars. The incisor and canine teeth of the deciduous set
are replaced by the teeth which bear the same names in the
permanent set. The deciduous "molars," however, are replaced by the permanent "prmmolars," and the "molars" of
the permanent set of teeth are not represented in the deciduous series, only existing once, and not being replaced by successors.
Fig. c. —Teeth of the right side of the lower jaw of the Chimpanzee (after Owen).
i Incisors; c Canine teeth: hn Premolars; m Molars.
All these four kinds of teeth are not necessarily present in
all Mammals, and, as will be afterwards seen, the characters of
the teeth are amongst the most important of the distinctions by
which the Mammalian orders are separated from one another.
The variations which exist in the number of teeth in different
Mammals are usually expressed by a "dental formula," which
presents the " dentition " of both jaws in a condensed and
easily-recognised form.
According to Owen, the typical permanent dentition of a
diphyodont Mammal would be expressed by the following
formula:-.3-3    I -I      4-4    3-3
33; c; Ip l4    m 3   = 443-3'   I —I'      4-4    3-3
The four kinds of teeth are indicated ih such a formula by the
letters-incisors i, canines c, prmmolars pm, molars inm. The
numbers in the upper line indicate the teeth in the upper jaw,
those in the lower line stand for those in the lower jaw; and
the number of teeth on each side of the jaw is indicated by
the short dashes between the figures.




CHARACTERS OF MAMMALIA.                 519
As regards the digestive system of the Mafammalia, salivary
glands are present in all except the true Cetacea. The alimentary canal has in most cases essentially the same structure as in
man; and the same accessory glands are present,-namely, the
liver and pancreas. Some very remarkable modifications occur
in the structure of the stomach and in the termination of the
intestine; but these will be noticed in speaking of the orders
in which they occur. The cavity of the abdomen is always
separated from that of the thorax by a complete muscular
partition-the diaphragm-as is the case in no other Vertebrate
animals. The abdomen contains the greater portion of the
alimentary canal, the liver, spleen, pancreas, kidneys, and other
organs. The thorax mainly holds the heart and lungs.
The heart is contained in a serous bag, the pericardium, and
consists (as in Birds) of two auricles and two ventricles. The
effete and deoxygenated blood is returned from the tissues by
the veins, and is conducted by the two venae cavae to the right
side of the heart into the'right auricle.  From the right auricle
it passes into the right ventricle, whence it is propelled through
the pulmonary artery to the lungs. Having been submitted to
the action of the air, the blood, now arterialised, is carried by
the pulmonary veins to the left auricle, and thence into the left
ventricle. From the left ventricle the aerated blood is driven
through the aorta and systemic vessels to all parts of the
body.  In Mammals, therefore, as'in Birds, the pulmonary
and systemic circulations are altogether distinct and separate
from one another. The two sides of the heart-except in the
foetus and as an abnormality in adults-have no communication with one another except by means of the capillaries.
The red blood-corpuscles are never nucleated, and in all
except the Camelidz (in which they are oval) they are circular
and discoid.
The lungs of Mammals differ from those of Birds in being
freely suspended in the thoracic cavity, the greater part of
which they fill, and in being enclosed freely in a serous sac
(pleura) which envelops each lung.  The lungs are minutely
cellular throughout, and the bronchi never open on the surface of the lung into a series of air-receptacles communicating
with one another, and placed in different parts of the body, as
is the case in Birds.
There is no " inferior larynx" in any Mammal, and the upper
aperture of the true larynx is always protected by an epiglottis.
The kidneys in Mammals are situated in the lumbar region,
and exhibit a division of their substance into cortical and medullary portions.




;20            MANUAL OF ZOOLOGY.
There are two ovaries in all Mammals, and the oviducts
are known as the " Fallopian tubes." Each oviduct dilates on
its way to the surface into a uterine cavity, which opens into
the vagina.  In the Monotremes and Marsupials this primitive condition is retained throughout life, the uterus remaining
double, and opening by two apertures into the cloaca or vagina.
In most cases this condition is so far modified in the adult, that
the two uteri have coalesced inferiorly, so as to have only a
single opening into the vagina, whilst they separate into two
horns or "cornua" superiorly. Only in the Monkeys and in
Man have the two uteri completely coalesced to form a completely single cavity, into the " fundus " of which the Fallopian
tubes open. In male Mammals there are always two testes
present.  In many Mammals the testes are permanently
retained in the abdominal cavity and there is no scrotum.
This is the case in the Monotremes, the Elephants, all the
Cetacca, and many of the Ednc/ztala.  Mostly, however, the
testes at an early period of life are transferred from the abdomen to a pouch of integument called the "scrotum."
Usually the scrotum is placed beneath the pubic arch and
behind the penis, but this position is reversed in the Marsupials.
Mammary glands are present in all Mammals, and they are
regarded by Huxley as an extreme modification of the cutaneous sebaceous glands. In the male Mammals the mammary
glands are present, but, under all ordinary circumstances, they
remain functionally useless and undeveloped.  Considerable
differences obtain as to the number and position of the mammary glands in different cases; but they are always placed on
the inferior surface of the body, and their ducts in the great
majority of cases open collectively upon a common elevation
-the "teat" or "nipple."  In the Afonotrczlmaat, however,
there are no nipples, the ducts of the mammary glands opening either into a pouch of the integument (Ec/zidna) or upon a
flat surface (Orniltowzhynchus).
The young Mammal is nourished for a longer or shorter
time by the milk secreted by the mammary glands of the
mother. In ordinary cases the milk is obtained by voluntary
suction on the part of the young animal; but in the Marsupials
the young are at first unable to suck for themselves, and the
tnilk is forced out of the gland by the contractions of a special
muscle.
The nervous system of Mammals is chiefly remarkable for
the great proportionate development of the cerebral mass as
compared with the size of the spinal cord.  In the higher
Mammals, again, the hemispheres of the cerebrum are much




CIARACTERS OF MAI;ILMALIA.             521
more largely developed proportionately than the remaining
parts of the brain. The brain of the Mammals is chiefly distinguished from that of the lower Vertebrata by the fact that the
two hemispheres of the cerebellum are united by a transverse
commissure-the pons Varolii-and the hemispheres of the
brain are connected by a great commissure —the corpus callosum-which is, however, of small size in the lower MamYmaia.
The senses, as a rule, attain great perfection in the Mammals; and the only sense which appears to be ever entirely
wanting is that of vision. In one of the most familiar instances
of this last-mentioned fact- namely, in the Mole —it has
recently been shown that it is only in the adult that vision is
lost, but that the organs of sight are well developed in the
young. The sclerotic coat of the eye is never supported by a
ring of bony plates as in Birds and many Reptiles. As a rule,
in addition to the upper and lower eyelids there is a third
perpendicular lid-the vmembrana nictitans-but this is wanting
or quite rudimentary in Man and in the Monkeys.
An external ear or concha for collecting the vibrations of
sound is usually present, but is wanting in the Cetacea, many of
the Seals, and in some other cases.
The integument is furnished over a greater or less portion
of its surface with the epidermic appendages known as "hairs."
These are developed, much as feathers are, upon little eminences or papillae of the derma, but they do not split up in
the process of development as feathers do. In the Ml/anis or
Scaly Ant-eater the epidermic appendages are in the form of
horny scales, and not uncommonly they are developed into
long spines, as in the Echidna, Porcupine, and Hedgehog.
In the Armadillos, again, the integument has the power of
developing plates of bone over a greater or less extent of its
surface. The only apparent exception to the universal presence
of hairs in some part or other of the skin of all Mammals is
constituted by the Celacea, some of which are without hairs in
the adult state. Some, however, of these (such as the Whales)
possess a few bristles in the neighbourhood of the mouth even
when fully grown. And the Dolphins, which are totally hairless when adult, exhibit tufts of hair on the muzzle in the
foetal state,




522             MANUAL OF ZOOLOGY.
CHAPTER LXXIII.
CLASSIFICA TION1 OF THE MAlfIMALIA.
NUMEROUS classifications of the Mam;zialia have been proposed, and it is a matter of regret that no one has been
universally accepted by Zoologists. Here, it will be sufficient
to describe briefly the three leading systems upon which the
Mammalia have been divided into sub-classes; whilst the first
will be adopted as sufficient for all practical purposes.
I. By many writers the class MAammalia is divided into two
great primary divisions, the Placentalia or Placental Mammals,
and the Implacenlalia or Non-placental Mammals, according
as the structure known as the " placenta" is present or absent.
The placenta, as before said, is a vascular organ developed in
the greater number of Mammals, by means of which the blood
of the fcetus is brought into relation with the blood of the
mother. The sub-class Placentalia, in which such a vascular
connection between the mother and foetus exists, comprises by
far the largest number of the Mammals.  The sub-class Implacentalia, in which no such vascular connection exists, comprises only.the two orders of the 1Monotrenzata and the M4arsupialia.
II. By Professor Owen the Mamma/ia are divided into four
sub-classes, characterised by the structure of the brain, as
follows:
a. Lyencephala, characterised by the fact that the cerebral
hemispheres are usually without folds, and leave the cerebellum, the olfactory lobes, and part of the optic lobes uncovered.
The hemispheres are not connected together by a corpus callosum.  (Monotremata and Marsuzpialia.)
b. Lissencephala, characterised by the fact that the cerebral
hemispheres are smooth or are provided with few folds, and
leave the cerebellum and part of the olfactory lobes exposed.
A corpus callosum is.present. (Cizeiroptera, Insectivora, Rodentia,
Edentala.)
c. Gyrencephzala, characterised by the fact that the hemispheres
of the cerebrum cover the greater part of the cerebellum and
the olfactory lobes. A corpus callosum is present, and the
surface of the cerebral hemispheres is generally thrown into
numerous convolutions.  (Cetacea, Carnivora, Sirlnia, Proboscidea, Unguzdata, Quadrumana.)
d. Archencephala, characterised by the fact that the cerebral
hemispheres now completely overlap the cerebellum and olfac



DIVISIONS OF MAMMALIA.                523
tory lobes; the number of convolutions attains its maximum;
and there is a corpus callosum.  (Man.)
This is the primary classification of the Mammalia put forth
by Owen, and there can be no question but that in many
respects it expresses substantial and important differences. It
will not be adopted here, partly because it is somewhat difficult
to follow or to apply in practice, and partly because some of
the characters upon which it is fournded are denied by other
eminent naturalists. Thus, in the definition of the sub-class
Lyencephala it is stated as one of the essential characters that
there is no corpus callosum or commissure between the hemispheres of the cerebrum. On the other hand, it is asserted
by Flower and Huxley that a corpus callosuml does exist in
these animals, though it never attains to any high degree
of development.
III. It was proposed by De Blainville, and the arrangement
has been accepted by Huxley and Rolleston, to divide the
Mammalia into the following three sub-classes, founded upon
the nature of the reproductive organs:a. Ornithodeaphia, characterised by the fact that the uterine
enlargements of the oviducts do not coalesce even in their
inferior portion to form a common uterine. cavity, but open
separately as in the Birds and Reptiles, Furthermore, the two
uteri open, not into a distinct vagina, but into a cloacal cavity,
into which the rectum and ureters also discharge themselves;
so that the condition of parts is very much the same as it is
in Birds.
This division includes only the Duck-mole (Ornithorhynchus)
and the Porcupine Ant-eater (Echidna), forming collectively
the single order of the JMono/remata.
b. Diide/phia, characteristed by the fact that the uterine
dilatations of the oviducts continue distinct throughout life,
opening into two distinct vaginae, which in turn open into a
urogenital canal, which is distinct from the rectum, though
embraced by the same sphincter muscle.
This sub-class contains the Marszpqia/ia, such as the Kangaroos, Opossurns, Wombats, &c., most of which are almost
entirely confined to Australia. They have many other characters in common, which will be spoken of hereafter.
III. Monode/lphia, characterised by the fact that the uterine
enlargements of the oviducts coalesce to a greater or less
extent to form a single uterine cavity, which, however, generally
shows its true composition by being divided superiorly into
two cornua. The uterus opens again into a single vagina,
which is always distinct from  the rectum.  This sub-class




324            MANUAL OF ZOOLOGY.
corresponds with the division of the "Placental" Mammals,
and includes all the fiamma/ia except the Monotremes and
Marsupials.
Before going on to consider the different orders of the Aiamnzma/ia in detail, it may be as well very briefly to run over the
leading characters by which the various orders are distinguished:
Order I. Monotremafa, characterised by the fact that the
ureters and ducts of the reproductive organs open into a common urogenital canal, which in turn opens, along with the
rectum, into a " cloaca."  The testes are abdominal, and are
not lodged in a scrotum. The mammary glands have no
nipples. The young is devoid of a placenta, but the female
possesses no marsupial pouch, though the pelvis is furnished
with "marsupial bones." In this order are only the Duckmole and the Echidna.
Order II. Marsupia/ia, characterised by the fact that the
uterine dilatations of the oviducts open with the ureters into a
urogenital canal, which is distinct from the rectum, though
embraced by the same sphincter muscle. The testes are not
abdominal, but are lodged in a scrotum which is suspended
by a narrow neck in front of the penis. The females are
mostly furnished with a marsupial pouch in which the young
are carried for some period after birth. The young are not
provided with a placenta, and are born in a very imperfect
state of development. Marsupial bones are present. In this
order are the Kangaroos, Opossums, Wombats, &c.
Order III. Edentata or Bruta, characterised by the universal absence of the median incisors, and the general absence
of all the incisors. The canines are usually wanting as well,
and sometimes there are no molars either. There is only one
set of teeth, and the teeth have neither complete roots nor are
furnished with a covering of enamel. The toes are always
furnished with claws. Placenta sometimes deciduate, sometimes non-deciduate. As examples of this order may be taken
the Sloths, Armadillos, and the great Ant-eater.
Order IV. Sirenia, comprising the Dugongs and Manatees,
characterised by being adapted to an aquatic life. Body fishlike, with a strong horizontal tail-fin. There is no sacrum,
and the hind-limbs are invariably wanting, whilst the forelimbs are converted into swimming-paddles  There are, in
the living forms at any rate, two sets of teeth, and the molars
have flattened crowns adapted for a vegetable diet. There are
two nostrils, and these are placed at the upper part of the
snout. There are two manmme, and these are placed on the
chest, and not on the abdomen.




DIVISIONS OF MIAMMALIA.               5 2
Order V. Cetacea, comprising the true Whales and Dolphins,
characterised by being aquatic Mammals, with a horizontal
tail-fin, no sacrum nor hind-limbs, and fore-limbs in the form
of swimming-paddles. The nostrils are single or double, and
are placed on the top of the head. The mammary glands are
two in number, and are placed in the region of the groin.
There is never more than one set of teeth, and in many cases
the adult is destitute of teeth altogether.  Placenta non-deciduate.
Order VI. Ungulata or Hoofed Quadrizeds, comprising the
whole of the Ruminants, the Horses, and most of the old
group of the Pachydermatous Mammals. This order is split
up into many important sections, and, as a whole, it is simply
characterised by the fact that there are never more than four
full-sized toes to each limb, and that the extremities of the toes
are furnished with expanded nails, constituting hoofs. There
are no clavicles. Placenta non-deciduate.
Order VIZ  Hyracoidea, comprising only the single genus
iyrax, characterised by having no canines, but by having
long curved incisors, which grow from permanent pulps, as in
the Rodents.  There are no clavicles.  The front-feet have
four toes, and the hind-feet three. The placenta is deciduate
and zonary.
Order VII. Proboscidea, comprising no other living Mammal except the Elephant, characterised by having no canines,
but only molars and incisors, of which the latter grow from
permanent pulps, and constitute defensive tusks.  There are
no clavicles. The feet are five-toed. The nose is prolonged
into a proboscis.  The mamma are two in number.  The
placenta is deciduate and zonary.
Order IX. Carnivora, comprising all the well-known beasts
of prey, such as Lions, Tigers, Dogs, Cats, &c., together with
the aquatic Seals and Walruses. They are all characterised by
always possessing the three different kinds of teeth-incisors,
canines, and molars-the canines being usually of great length,
and a greater or less number of the molars having sharp cutting edges.  The clavicles are always rudimentary, the teats
are abdominal, and the placenta is deciduate and zonary.
Order X. Rodentia, comprising the Beavers, Rats, Mice,
Hares, Rabbits, Squirrels, and others, characterised by the
absence of canines and the possession of no more than two
incisors in the lower jaw, and usually no more than two in the
upper jaw. The incisors are greatly developed, growing from
permanent pulps, and continuing to grow during the life of the
animal. Placenta deciduate and discoidal.




526            MANUAL OF ZOOLOGY.
Order XI. Cheiroptera, comprising only the various Bats,
and characterised by the fact that the four outer or ulnar
fingers are greatly developed and elongated, and are united
together by a leathery flying-membrane or "patagium," which
is continued from the hand and arm to the side of the body
and hind-limb. By means of this patagium the Bats possess
the power of flight. Clavicles are always present. The teeth
vary a good deal, but there are always canines. The placenta
is deciduate and discoidal.
Order XII. Insectivora, comprising the Moles, Shrew-mice,
and Hedgehogs, characterised by having the crowns of the
molar teeth furnished with sharp and pointed cusps. Welldeveloped clavicles are present in almost all cases. The placenta is deciduate and discoidal.
Order XIII Quladrunmanza, comprising the Lemurs, Apes,
and Monkeys. Dentition usually the same as in man, or with
an additional prwmolar on each side of each jaw, or varying a
good deal in the lower forms. The series of teeth is uneven
and interrupted. The innermost digit of the fore-limb (poAlex)
is mostly opposable to the other fingers when present, but it
may be wanting. The hallux is also opposable to the other
toes of the hind-limb, so that the hind-feet constitute prehensile
hands.  Clavicles are always present.  The placenta is deciduate and discoidal.
Order XIV. Bimanan. —This order includes Man alone. The
dental formula is-.2-2    I —      2-2    3-3
-— 2; -C     ~  im   --      = 32.
2-2'   — 5   2-2    3-3
The teeth are nearly even, and are not interrupted by any
interval (diastemna). The pollex or thumb of the fore-limb is
opposable to the other digits, but this is not the case with the
hallux or great toe. The attitude of the body in progression
is habitually erect. The placenta is deciduate and discoidal.




NON-PLA CENTAL MAMMAMMALS.
CHAPTER LXXIV.
MONOTREMA TA AND MARS UPIALIA.
ORDER I. MONOTREMATA.-The first and lowest order of the
Mammalia is that of the AIonotremata, constituting by itself
the division Ornit/odelphia, and containing only two genera,
both belonging to Australia-namely, the Duck-mole (Ornit/wrhynchus) and the Porcupine Ant-eater (Echidna).
The order is distinguished by the following characters:The intestine opens into a "cloaca," which receives also the
products of the urinary and generative organs, which discharge
themselves into a urogenital canal, the condition of parts
being very much the same as in Birds. The jaws are either
wholly destitute of teeth (Echidna), or are furnished with horny
plates which act as teeth. The pectoral arch has some highly
bird-like characters, the most important of these being the
extension of the coracoid bones to the anterior end of the
sternum. The females possess no marsupial pouch, but the
pelvis is furnished with the so-called "marsupial bones," believed to be ossifications of the internal tendons of the external
oblique muscles of the-abdomen. The testes of the male are
abdominal throughout life, and there is therefore no scrotum,
whilst the vasa deferentia open into the cloaca. The corpus
callosum is very small, and has been asserted to be altogether
wanting. There are no external ears. The mammary glands
have no nipples, and their ducts open either into a kind of
integumentary pouch (Echidna) or simply on a flat surface
(Ornitlhorhynchus).  The young are said to be destitute of a
placenta, or, in other words, no vascular connection is established between the foetus and the mother. The feet have five
toes each, armed with claws, and the males carry perforated
spurs on the back of the tarsus (attached to. a supplementary
tarsal bone).
The order MoInotretmata includes only the two genera Orni.




528             MANUAL OF ZOOLOGY.
thorhynchus and Echidna —the one represented by a single
species (0. paradoxius), and the other by two species (E.
hystrix and E. setosa).  All are exclusively confined to Australia and Tasmania.
The Ornitorhynzchus or Duck-mole is one of the most extraordinary of Mammals. The body (fig. 203) resembles that
of a mole or small otter, and is covered with a close, short,
brown fur. The tail is broad and flattened. The jaws are
produced to form a beak just like that of a duck in appearance;
hence the name of "Duck-billed animal," often applied to it.
The margins of the jaw are-sheathed with horn, and furnished
with transverse horny plates; but there are no teeth. The
Fig. 203.-Ornithorhynchls laradoxuzs.
sternum is of five pieces, not counting in the episternum, and
there are sternal ribs. The nostrils are placed at the apex of
the upper mandible. The legs are short, and the feet have
five toes each, furnished with strong claws, which enable the
animal to burrow with facility. The toes are also united by a
membrane or web, so that the animal swims with great ease.
The Ornithorhynchus is exclusively found in Australia and
Tasmania, and inhabits streams and ponds. Its food consists
chiefly, if not exclusively, of insects, and the animal makes
very extensive burrows on the banks of the rivers which it frequents. The young are born quite blind, and nearly naked,
and the method in which they obtain milk from the mother is
somewhat obscure, as there are no nipples, nor is there any
marsupial pouch. It is certain, however, that the beak of the
young animal is extremely different from what it is in the adult
condition. The young animal is totally hairless, the mandibles
are soft and flexible, the tongue is not placed far back in the
mouth (as it is in the adult), and the eye is at first covered by
the skin.
* The genus Ec/zidna is represented by two species, E. hystrix




MARSUPIALIA.                      529
and E. setosa, both belonging to the Australian province. The
Echidtna hystrix is the best-known species, and in some external respects is not unlike a large hedgehog, having the back
covered with strong spines, interspersed with a general coating
of bristly hairs. The snout has not the form of a duck's bill,
as in the Ornithorhynchus, but the two mandibles are greatly
elongated, and are enclosed in a continuous skin till close
upon their extremities, where there is a small aperture for the
protrusion of a very long and flexible tongue. The jaws are
wholly devoid of teeth or anything in the place of teeth; and
the nostrils are placed at the extremity of the cylindrical snout.
The feet have five toes each, furnished with strong curved
digging-claws, but the toes are not webbed.  The Echidna
measures from  fifteen to eighteen inches in length, and is a
nocturnal animal. It lives in burrows, and feeds upon insects,
which it catches by protruding its long and sticky tongue.
ORDER II. MARSUPIALIA. -  The order Marsupialia constitutes by itself the sub-class Dideiphia, and forms with the
Mono/remata the division of the Non-placental Mammals.
With the single exception of the genus Dideikphys, which is
American, all the Marsupialia belong to the Melanesian province; that is to say, they all belong to Australia, Van Diemen's Land, New  Guinea, and some of the neighbouring.'
islands. -
The following are the characters which distinguish the
order:
The skull is composed of distinct cranial bones united by
sutures, and they all possess true teeth; whilst the angle of
the lower jaw is almost always inflected. The pectoral arch
has the same form as in the higher Mammals, and the coracoid no longer reaches the anterior end of'the sternum. All
possess the so-called "marsupial bones," attached to the brim
of the pelvis.  The corpus callosum  is- very'small, and has
been asserted to be absent. The young Marsupials are born
in a very imperfect condition, of very small size, and at a
stage when their development has proceeded to a very limited
degree only.  (In the Kangaroo the period of gestation is
only about thirty-nine days, and in the DidejpOhidc it is said to
be only fifteen or seventeen days). It is believed that there
is no placenta or vascular communication between the mother
* One Kangaroo (Macrojus Bruynii) is found in the Indian Archipelhago,
along with five Phalangers, which differ from the Australian forms in having the tail partially or entirely naked or scaly. There are also TreeKangaroos, and the curious Cuscus, distinguished by a prehensile tail,
large eyes, and slow progression.




530             MANUAL OF ZOOLOGY.
and foetus, parturition taking place before any necessity arises
for such an arrangement.  As the young are born in such
an imperfect state of development, special arrangements are
required to secure their existence.   When born, they are
therefore, in the great majority of cases, transferred by the
mother to a peculiar pouch formed by a folding of the integument of the abdomen. This pouch is known as the " marsupium," and gives the name to the order. Within the marsupium are contained the nipples, which are of great length.
Being for some time after their birth extremely feeble, and
unable to perform the act of suction, the young within the
pouch are nourished involuntarily, the mammary glands being
provided with special muscles which force the milk into the
mouths of the young. At a later stage the young can suckle
by their own exertions, and they leave the pouch and return
to it at will. In a few forms there is no complete marsupium
as above described; but the structure of the nipples is the
same, and the young are carried about by the mother, adhering to the lengthy teats.
The so-called "marsupial bones" (fig. 204) doubtless serve
to support the marsupial pouch and its contained young, but
this cannot be their sole function,
since they occur in the Monotremes,
in which there is no pouch. It is
believed by Owen that the function
of the marsupial bones is to assist in
the action of the mammae and testes,
serving respectively as a fulcrum for
the muscle spread over the mamm I J 1   mary gland and-for the cremaster.
The oviducts open into vaginal
tubes which open into a urogenital
canal; but this does not open into
a "cloaca," though embraced by a
sphincter muscle common to it and
to the rectum.  In other words, the
vagina is separated wholly or in great
part into two distinct tubes. The
testes are not abdominal throughout
life as in the Monotremes, but are
Fig. 204.-One side of the pelvis lodged in a scrotum.  This, howof a Kangaroo, showing the ever, is placed in front of the penis,
" marsupial bones" (rn)-after             p
Owen.                and not beneath the pubic arch as
in most Mammals. From this unusual position of the scrotum, it is regarded by Owen as being




MARSUPIALIA.                   531
the same structure as the marsupial pouch of the female,
turned inside out. Though they form an extremely natural
order, sharply separated from all the rest of the Mammals, the
Marsupials form a large and varied group. In fact this order,
from being the almost exclusive possessor of a continent as
large as Australia, has to discharge in the economy of nature
functions which are elsewhere discharged by several orders.
The Afarszpialia are divided by Owen into the following
sections:a. Rhizophaga. —In this section is the well-known Australian
animal, the Wombat (Phascolomys fossor), often called by the
colonists the "badger."   The Wombat is a stout, heavy
animal, which attains a length of from two to three feet. The
legs are very short and stout, and the animal burrows with
ease by means of strong curved digging-claws, with which the
fore-feet are furnished.  The tail inl the Wombat is quite
rudimentary, and the whole body is clothed with a brown
woolly hair. In its dentition the Wombat presents a curious
resemblance to the herbivorous Rodents.  There are two
incisors in each jaw, and these are long and rootless, growing
from permanent pulps. There are no canines, so that the
incisors and proemolars are separated by a considerable space.
The dental formula is-I   0-0         I I   4-4
I-'  c'; fm'  m 4   = 24.
1 —1  -o' - 0      4-4
The premnolars and molars agree with the incisors in growing
from permanent pulps, in which respect the Wombat differs
from all the other Marsupials, and agrees with the herbivorous
Rodents, with those-Edentata which have teeth, and with the
extinct Toxodon.-(Owen.)
The Wombat is a nocturnal animal, and feeds chiefly upon
roots and grass.
b. Poep/zaga.-In this section are the Kangaroos (Macrojodirze) and the Kangaroo-rats or Potoroos (f2jpsiprymnus), all
strictly phytophagous. The Kangaroos are distinguished by
the disproportionate length of the hind-limbs and disproportionate development of the posterior portion of the body as
compared with the fore-limbs and fore part of the body. The
hind-legs are exceedingly long and strong, and the feet are
much elongated-the whole sole being applied to the ground.
The hind-feet have four toes each, of which the central one
is by far the largest, and the two inner toes are very small,
and are united by a common integument.  The tail is also
extremely long and strong, and by the assistance of this organ
24




532             MANUAL OF ZOOLOGY.
and the powerful hind-limbs the Kangaroos are enabled to
effect extraordinarily long and continuous leaps. In fact, leaping is the ordinary mode of progression in the typical Kangaroos; and when walking upon all fours their locomotion
is slow and ungraceful. The anterior extremity of the body is
Fig. 205.-Koala or Kangaroo-bear (Phascolarctos cinereus) —after Gould
very diminutive as compared with the posterior, and the forelimnbs are quite small, but have five well-developed toes armed
with strong nails. The head is small, with large ears, and the
dental formula is3-3   o —0        - I-i    4-4
I-I  0;  n -; m 44 = 28.
There are therefore six upper incisors, two lower incisors,
and no functional canines (though rudimentary upper canines
are present in the young of some of the Kangaroos, at any
rate). The stomach is complex, and sacculated. The Kangaroos are all herbivorous, and mostly live, either scattered or
gregariously, on the great grassy plains of Australia. The
"Tree-kangaroos," however (constituting the genus Dendrolagus), live mostly in trees; and, in adaptation to this mode of
life, the fore-legs are nearly as long and strong as the hind-legs,
the tail is not used as a support, and the claws are long, curved,
and pointed. They are natives of New Guinea. The " Rock




MARSUPIALIA.                         5 33
Kangaroos " form the genus Petrogale, and inhabit the mountainous regions of North-western Australia.
The Kangaroo-rats (HypsiZprymnus) differ from the true Kangaroos chiefly in their smaller size, and in the presence of welldeveloped  upper carines (fig. 206, B), and in having scaly
tails. They are diminutive nocturnal animals, and they live
mostly upon roots.
c. Capopiaga. — Intermediate between the Kangaroos and the
typical members of the present section (the Phalangers) is the
Phascolarctos-the " native sloth" or " bear" of the Australian
colonists and the " koala" of the natives (fig. 205).  This curious animal is about two feet in length, having a stout body,
covered with a dense bluish-grey fur. The tail is wanting; and'
the feet are furnished with strong curved claws, which enable
the animal to pass the greater part of its existence in trees. In
g. o6 —A Dention of a Canivoous Masupial (Ty
Fig. 2o6. —A, Dentition of a Carnivorous Marsupial (Thylacinus), showing the long
and pointed canines and the trenchant molars and praemolars. B, Dentition of a
herbivorous Marsupial (Hyfisifirymsnus), showing the flat-crowned molars. (After
Owen.) c Canine teeth; i i Incisors.
this it is greatly'assisted by the fact that all the feet are prehensile, the hallux being opposable, and the digits of the forelimb divided into two sets, the thumb and index-finger being




534             MANUAL OF ZOOLOGY.
opposable to the other fingers. The koala is a slow animal
which feeds on the foliage of the trees in which it spends its
existence.
The typical group of the Carpophagous Marsupials is that of
the Phalangistidae or Phalangers, so called because the second
and third digits of the hind-feet are joined together almost to
their extremities.  The family includes a number of small
Marsupials, fitted for an arboreal -existence, to which end the
hallux is opposable and nail-less, whilst the four remaining toes
of the hind-feet have long curved claws.  The tail, too, is
generally very long, and its tip is usually prehensile. The
Phalangers are all small nocturnal animals which live upon
fruits and other vegetable food.  The best known of them is
the Australian Opossum (Phalang-ista zvu/piza), which must not
be confounded with the true or American Opossums, which
belong to another section of the ~A/lrszuialia. The Phalangers,
namely, are distinguished from  the Opossums properly so
called, amongst other characters, by their dentition, the
canine teeth being always very small and functionally useless in the lower jaw, and sometimes in the upper jaw as well.
The Phalangisa vulpizna is nocturnal and arboreal in its
habits, and its flesh is esteemed a-great delicacy by the native
Australians, with whom opossum-bunting is a favourite pursuit.
The flying Phalangers or Petauri are closely allied to the
true Phalangers, but differ in not having a prehensile tail, and
in having a fold of skin extending on each side between the
sides of the body and the fore and hind limbs. By the help
of these lateral membranes the Pelauri can take extensive leaps
from tree to tree; but though called "flying" Phalangers, they
have no power of flight properly so called. They are beautiful
little animals, nocturnal in their habits, and having the body
clothed with a soft and delicate fur.
d. Entozmophaga.- In this section the jaws are always
furnished with canine teeth, but these are not of very large
size, and the animals composing the section are therefore not
highly predacious, but "prey, for the most part, on the smaller
and weaker classes of invertebrate animals."  In this section
are the Bandicoots (Peranmeidce), the American Opossums
(Didelphince), and the Banded Ant-eater (Mjyrmecobizs).
The Bandicoots' (Perameiinde) are small Australian animals,
which appear to fill the place of the Hedgehogs, Shrew-mice,
and other small Insec/ivora of the Old World.  The hind*The name " DBandicoot " properly belongs to the Great Rat (Ahts
gi7hat1lets) of Tndia,




MARSUPIALIA.                   535
limbs in the Bandicoots are considerably longer than the forelimbs, and their progression is therefore by a series of bounds.
The fore-limbs have really five toes each, but only the central
three of these are well developed, the outermost and innermost
digits being rudimentary. The three functional toes are armed
with long strong claws, with which the Bandicoots burrow with
great ease.  The marsupial pouch-and this is a singular
point-opens, in some species at any rate, backwards instead
of forwards.  In the nearly-allied genus Chceropus, also from
Australia, it appears that the two outer toes of the fore-feet are
entirely absent.
The second family of this section —namely, the true Opos
sums or Didedphidei —is remarkable in being the only group of
the whole order which occurs out of the Australian province.
rThe Didedphide, namely, are exclusively found in North
and South America, where they are known as "Opossums."
A considerable number of species is known, but they are
mostly of small size, the largest measuring not more than from
two to three feet, inclusive of the tail. The Virginian Opossum (Dildelphys Virginiana) is the only member of the family
which is found in North America, and it was the earliest Marsupial known to science.  Most of the Opossums are carnivorous, feeding upon small quadrupeds and birds, but they also
eat insects, and sometimes even fruit. One species (Did/phyes
cancrivora) lives chiefly upon Crabs; and the Yapock (Chebi-a-;lecles) has webbed feet, and appears to lead a semi-aquatic life.
All the Didelphiide have the hallux nail-less and opposable to
the other toes, so as to convert the hind-feet into prehensile
hands, and all have a more or less perfectly prehensile tail,
these being adaptations to an arboreal life. The marsupial
pouch is sometimes not present in a complete form, but is
merely represented by cutaneous folds of the abdomen concealing the nipples.  In the Didel~phys dorsigera, in which this
peculiarity obtains, the young soon leave the nipples, and are
then carried about on the back of the mother, to whom they
cling by twining their prehensile tails round hers. The dentition
of the Opossums is remarkable for the great number of the
incisor teeth, the dental formula being5 —5 I.    I      3-3       4 —4 0
4-4     I I-I p 3-3        4- 4
The Banded Ant-eater (A/yrmecolius fasciatlus) is a small but
extremely elegant little animal, which inhabits Western and
Southern Australia, and lives upon insects (fig. 207). The tail
is bushy, and differs from that of the Didedpj/idwe in not being




536             MANUAL OF ZOOLOGY.
prehensile. The fore-feet have five toes armed with claws; the
hind-feet have only four toes. The.Myrmecobius is remarkable
for the extraordinary number of molar teeth, in which it exceeds
any existing Marsupial, and is only surpassed by some of the
Armadillos. The dental formula is4-4      I —I     3 —3      6-6
i 33; c I;   m3       m             = 54.
e. Sarcoaphaga.-This is the last section of the existing Marsupials, and includes a number of predacious and rapacious
forms, which fill the place held elsewhere by the true Carnivora.
They are distinguished by the fact that the intestine is destitute
of a caecum, and by their strictly carnivorous dentition, the
Fig. 207. —Myrmecobius fasciatus.
canines being strong, long, and pointed, whilst the molars and
praemolars have cutting edges furnished with three cusps (fig.
206, A). The best-known species of this section are the Thylacinus cynocephalus and the Dasyurus ursinus.  The former of
these is the largest of the rapacious Marsupials, being about as
big as a shepherd's dog. It is a native of Van Diemen's Land,
and is known to the colonists as the "hyaena." Its head is
very large, and the back exhibits several transverse black
bands.  It lives in caverns and amongst the rocks in the.wildest parts of the colony, and its numbers have been very
much reduced by the constant war waged upon it by the
settlers.  The Dasyurus ursilus is also a native of Van
Diemen's Land, where it is known as the "native devil."
Though smaller than the Thylacine, the Dasyurus is extremely
ferocious, and is capable of committing great havoc amongst
animals even as large as sheep.




PLA CENTAL MAMMAIALS.
CHAPTER LXXV.
EDENTA TA.
ORDER III. EDENTATA or BRUTA.-The lowest order of the
placental or monodelphous Mammals is that of the Edenta/a,
often known by the name of Brzia. The name Edentata is
certainly not an altogether appropriate one, since it is only in
two genera in the order that there are absolutely no teeth.
The remaining members of the order have teeth, but these
are always destitute of true enamel, are never displaced by a
second set, and have no complete roots. Further, in none of
the EEdentata are there any median incisors, and in only one
species (one of the Armadillos) are there any incisor teeth at all.
Canine teeth, too, are almost invariably wanting. Clavicles
are usually present, but are absent in the Scaly Ant-eater or
Manis. All the toes are furnished with long and powerful
claws.  The mammary glands are usually pectoral, but are
sometimes abdominal in position. The testes are abdominal
in position. The skin is often covered with bony plates or
horny scales.
The order Edentata is conveniently divided into two great
sections, in accordance with the nature of the food, the one
section being phytophagous, the other insectivorous. In the
former section is the single group of the Sloths (Bradypodide).
In the latter are the two groups of the Armadillos (Dasyypodid&e),
and the various species of Ant-eaters (the latter constituting
Owen's group of the Eden/ula).
The order Edent/a/a is but sparingly represented in modern
times, and its geographical distribution is peculiar. The true
Ant-eaters, the Armadillos and the Sloths, are entirely confined
to South America, in which country a group of gigantic extinct
Edentates existed in Post-tertiary times. The Scaly Ant-eater
or Manis is common to Asia and Africa, and the genus Orycjeropus is peculiar to South Africa.
The family Bradjtpodidea comprises some exceedingly curious




5 38             MANUAL OFI ZOOLQGYo
animals which are exclusively confined to South America, inlhabiting the vast primeval forests of that continent.  The
Sloths have a remarkably short and rounded face, and the
body is covered with hair.  The incisor teeth are altogether
wanting, btit there are always simple molars, and in the Twotoed Sloth or Unau the first tooth in each jaw on each side is
so much larger than the others, and so much more pointed,
that it has been regarded as a canine.  The stomach  is complex, somewhat resembling that of the Ruminants,  The cervical vertebrme are generally regarded as being more than the
normal seven in. number in the Three-toed Sloth, and the long
bones have no medullary cavitie3.  The most striking peculiarities, however, about the Sloths are connected with their
mode of life.  The Sloths, in fact, are constructed to pass
their life suspended from the under surface of the branches
of the trees amongst which they live; and for this end their
organisation is singularly adapted.  The fore-limbs are much
longer than the hind-limbs, and the bones of the fore-arm are
unusually movable.  All the feet, but especially the fore-feet,
are furnished with enormously long curved claws (fig. 208), by
the aid of which the animal is enabled to move about freely
suspended back downwards from the branches.  Not only is
this the ordinary mode of progressionil amongst the Sloths, but
even in sleep the animal appears to retain this apparently unnatural position.
Fg. 8. -oHand of Three-toed Sloth (B3rdypjts trfalcfyl2s)-after 0wen
Owing to the disproportionate size of the fore-limbs as conmparedl with the hind-limbs, and owing to the fact that the hindfeet are so curved as to render it impossible to apply the sole
to the ground, the Sloth is an extremely awkward animal upon
the ground, and it has therefore recourse to terrestrial progres




EDENTATA.                     539
sion only when absolutely compelled to do so   Whilst the
name of "Sloth" may thus appear to be a merited one from
the point of view of a terrestrial Mammal, it is wholly undeserved when the animal is looked upon as especially adapted for
an arboreal existence.  In the Ai or Three-toed Sloth (Brad,pus Iridecly/lus) there are three toes to each foot, and these are
short, completely rigid, and so enveloped in the integument
as to leave nothing visible except the enormously long and
crooked claws.  The hand and foot' are`ointed to the arm
and leg obliquely, so that the palm and sole cannot be applied
to the ground, but are turned inwards.   The ungual phalanges are also so articulated that the claws are bent inwards
towards the palm or sole.  There are sixteen pairs of ribs.
The molars are rootless, growing from permanent pulps, and
consisting of a simple cylinder of dentine enveloped in enamel.
In the Unau (Chocezpus) the feet are two-toed, and there are
twenty-three pairs of ribs, the greatest number known in the
Mammals.
The second family of the Etzentata is that of the Dasypodicdwe
or Armadillos. These are found exclusively in South America,
as are the Sloths, but they are very different in their habits.
The Armadillos are burrowing animals, furnished with strong
diggiihg-claws and well-developed collar-bones.  The jaws are
provided with numerous simple molars, which attain the enormous number of nearly one hundred in the great Armadillo
(Dasjpus gigas). The upper surface of the body is covered
with a coat of mail, formed of hard bony plates or shields,
united at their edges. A portion of this armour covers the
head and shoulders, and another portion protects the hindquarters; whilst between these is a variable number of movable bands which run transversely across the body, and give
the necessary flexibility to this singular dermoskeleton.  In
some species this flexibility is so great that the animal can roll
itself up like a hedgehog. The tail is likewise mostly covered
with bony scutes.
The Armadillos are confined entirely to South America,
ranging from Mexico to Patagonia. In this country, also, have
been found the remains of a gigantic armour-plated animal
allied to the Armadillos, which will be subsequently described
under the name of the GOpbt/odol.  Amongst the best-known
species of Armadillo are the Peba (Dasyplps Peba), the Poyou
(D. sexcinacus), the Tatouay (D.  Tafozay), and the Great Armadillo (D. gizns). A somewhat aberrant form is the Chlamnypjhorzls
(fig. 209) of South America, the total length of which is only
about six inches.




540             MANUAL OF ZOOLOGY.
The remaining members of the Eden/ala are the various
Ant-eaters, but these are so different from one another in their
characters that they form three distinct families, also distinguished by their geographical distribution.
Fig. 2og.-Chlamyphorus truncatus.
a. _Ayrmecop/hagide.-This family is exclusively confined to
South America, as are the two preceding, and it contains only
the Hairy or true Ant-eaters. These' curious animals feed
chiefly upon Ants and Termites, which they catch with their
long sticky tongues. The jaws are wholly destitute of teeth;
the body is covered with hair; there is a long tail; and the
feet are armed with long and strong curved digging-claws. The
toes are united by skin up to the bases of the claws, as in the
Sloths; the ungual phalanges are articulated in the same way,
and the palm and sole are similarly turned inwards.
The best-known species of this family is the Great Ant-eater
(Myrmecophagajubata).  This singular animal attains a length
of over four feet, and has an extremely long and bushy tail.
The jaws are produced to form a long and slender snout,
which is entirely enclosed in the skin, till just at its extremity,
where there is an aperture for the protrusion of the thread-like
tongue. The anterior feet have four, and the posterior feet
five toes, all armed with strong curved claws, which, when
not used in digging, are bent inwards, so that the animal
walks on the sides of the feet. The animal is perfectly harmless and gentle when unmolested, and leads a solitary life. It
lives mainly upon Termites, into the nests of which it forces
its way by means of the powerful claws.  When the Termites




EDENTATA.                     541
rush out to see what is the matter, the Ant-eater thrusts out its
glutinous tongue, an action which can be repeated with marvellous rapidity. Two other species have been described, both
much smaller than the preceding, and both arboreal ill their
habits, and furnished with prehensile tails.
b. Atfanid&e.-This family includes only the Scaly Ant-eaters
or Pangolins, all exclusively confined to the Old World, and
found in both Africa and Asia. The whole of the body, limbs,
and tail in the.ManidE is covered with an armour of horny
imbricated plates, overlapping like the tiles of a house, and
apparently consisting of agglutinated hairs.  The legs are
short, and furnished with four or five toes each, ending in long
and strong digging-claws; but there are no clavicles. The
tongue resembles that of the Hairy Ant-eaters in being long
and contractile, and capable of being exserted for a considerable distance beyond the mouth. It is covered with a glutinous
saliva, and is the agent by which the animal catches ants and
other insects. The jaws are wholly destitute of teeth. When
threatened by danger, the Pangolins roll themselves up into a
ball, like the hedgehogs. The tail is comparatively long, and
is covered with scales. Though very strong for their size,
none of the species attain a length of more than three or four
feet, inclusive of the tail.  The best-known species are the
Mlanis pentadaclyla of India, and the Afianis tetradactyla of
Africa.
c. Orycteropidw.-The last family of the living Edentata is
that of the Orycleropidw, comprising only the single genus
Orycteropus. This genus comprises only a single species, the
O. Capensis, which is peculiar to South Africa, and is known
by the Dutch colonists as the "Aardvark" or Ground-hog.
The animal is nocturnal in its habits, and lives upon insects.
The'body is elongated, and the tail is long, the species attaining a total length of four feet or more. The legs are short,
and the feet plantigrade, the anterior pair having four unguiculate toes, the posterior five.  The claws are strong and
curved, and enable the animal to construct extensive burrows.
The skin is very thick, and is thinly covered with bristly hairs;
and the tail is hairy. The head is elongated, and the mouth
small-devoid of incisor and canine teeth, but furnished with
a number of cylindrical molars (6_7).  The crowns of the
molars are flat, and they are composed of dentine traversed by
numerous dichotomising pulp-cavities. The tongue is long,
flat, and slender, and is covered by a sticky saliva, by the aid
of which the animal catches insects.  The head is long and




542             MANUAL OF ZOOLOGY.
attenuated, the snout truncated and callous, and the ears large,
erect, and pointed.
CHAPTER LXXVI.
SIRENIIA AND CE TA CEA.
ORDER IV. SIRENIA. —This order comprises no other living
animals except the Dugongs and Manatees, which are often
placed with the true Cetaceans (Whales and Dolphins) in a
common order. There is no doubt, in fact, but that the Sirenia
are very closely allied to the Cetacca; and though they are to
be regarded as separate orders, yet they may be advantageously considered as belonging to a single section, which has
been called &Azhtilata, from the constant absence of the hindlimbs.
The Sirenzia agree with the Whales and Dolphins in their
complete adaptation to an aquatic mode of life (fig. 2Io);
especially in the presence of a powerful caudal fin, which differs
from that of Fishes in being placed horizontally, and in being
a mere expansion of the integuments, not supported by bony
rays. The hind-limbs are wholly wanting, and there is no sacrum. The anterior limbs are converted into swimming-paddles
or "flippers."  The snout is fleshy and well developed, and
the nostrils are placed on its upper surface, and not on the top
of the head, as in the Whales.  Fleshy lips are present, and
the upper one usually carries a moustache. The skin is covered
with fleshy bristles.  The head is not disproportionately large,
as in the true Whales, and is not so gradually prolonged into
the body as it is in the latter. There may be only six cervical
vertebrae. The teats are two in number and are " thoracic,"
i.e., are placed on the chest. There are no clavicles, and
the digits have no more than three phalanges each. The testes
are retained throughout life within the abdomen, but vesiculae
seminales are present. The animal is diphyodont, the pernmanent teeth consisting of molars with flattened crowns adapted
for bruising vegetable food, and incisors which are present in
the young animal, at any rate. In the extinct R/hy/ina it does
not appear that there were any incisor teeth.
The only existing Sirenia are the Manatees (Afanazlus) and
the Dugmengs (Ha/icore), often spoken of collectively as " seacows," and forming the family of the Mifalatide.




SIRENIA.                      543
The Manatees are characterised by the possession of numerous molar teeth (8-8) and of two small upper incisors, which
are wanting in the adult. The tail-fin is oblong or oval in
shape, and the anterior limbs are furnished with nails to the
_/
Fig. 210o.-Sirenia.' Dugong (Haicoren
four outer digits. They occur on the east coast of North
America, especially in the Gulf of Mexico, and another species
is found on the west coast of Africa. They are generally found
in considerable numbers about the mouths of rivers and estuaries, and they appear to live entirely upon sea-weeds, aquatic
plants, or the littoral vegetation. They are large, awkward
animals, attaining a length of from eight to ten feet as a rule,
but sometimes growing to a length of nearly twenty feet.
The Dugongs (Halicore, fig. 210 o) have   molar teeth in
5-5
2-2
the young condition, but only 2-2 when old.  Inferior incis2 —2
ors are present in the young animal, but are wanting in the
adult. The upper jaw carries two permanent incisors, which
are entirely concealed in the jaw in the females, but which
increase in size in the males with the age of the animal, till
they become pointed tusks. The anterior extremities are nailless, and the tail-fin is crescentic in shape.  In their general
appearance and in their habits the Dugongs differ little from
the Manatees, and they are often killed and eaten. They
attain a length of from eight to ten, twelve, or more feet, and
are found chiefly on the coasts of the Indian Ocean. The bones
are remarkable for their extreme density, their texture being
nearly as close as ivory.
The Manatees and Dugongs, as before said, are the only
living Sifenia; but besides these there is a very singular form,
the Rhytizna Stelleri, which is now extinct, having been exter



544             MANUAL OF ZOOLOGY.
minated by man within a comparatively recent period. This
remarkable animal was discovered about the middle of the
eighteenth century in a little island (Behring's Island) off the
coast of Kamtschatka. Upon this island the celebrated voyager
Behring was wrecked, and he found the place inhabited by
these enormous animals, which were subsequently described
by M. Steller, who formed one of his party. The discovery,
however, was fatal to the Rhytina, for the last appears to have
been seen in the year I768. The RRhytiiza was an animal of
great size, measuring twenty-five feet in length, and twenty feet
at its greatest circumference. There can hardly be said to
have been any true teeth, but the jaws contained    large
lamelliform fibrous structures, which officiated as teeth, and
may be looked upon as molars. The epidermis was extremely
thick and fibrous, and hairs appear to have been wanting.
There was a crescentic tail-fin, and the anterior limbs alone
were present.
ORDER V. CETACEA.-In this order are the Whales, Dolphins, and Porpoises, all agreeing with the preceding in their
complete adaptation to an aquatic life (figs. 2I3, 2I4). The
body is completely fish-like in form; the anterior limbs are converted into swimming-paddles or "flippers;" the proximal
bones of the fore-limbs are much reduced in length, and the
succeeding bones are shortened and flattened, and are enveloped in a tendinous skin, thus reducing the limbs to oarlike fins; there are no external ears; the posterior limbs are
completely absent; and there is a powerful, horizontally-flattened, caudal fin, sometimes accompanied by a dorsal fin
as well. In all these characters the Cetacea agree with the
Sireniia, except in the one last mentioned. On the other hand,
the nostrils, which may be single or double, are always placed
at the top of the head, constituting the so-called " blow-holes"
or " spiracles;" and they are never situated at the end of a
snout. The body is very sparingly furnished with hairs, or
the adult may be completely hairless. The testes are retained
throughout life within the abdomen, and there are no vesiculake
seminales. The teats are two in number and are placed upon
the groin. The head is generally of disproportionately large
size, and is. never separated from the body by any distinct
constriction or neck. The lumbar region of the spine is long,
and, as in the Sirenia, there is no sacrumr, and the pelvis is
only present in a rudimentary form. There are no clavicles,
and some of the digits may possess more than three phalanges
each. Lastly, the adult is either destitute of teeth or is mono



CETACEA.                      545
phyodont —that is to say, possesses but a single set of teeth,
which are never replaced by others. When teeth are present,
they are usually conical and numerous, and they are always of
one kind only.
The Celacea may be divided into the three families of the
Baalnidde   or Whalebone Whales, the Depvhinidae or Dolphins
and Porpoises, and the Cafodontide or Sperm Whales.  Of
these, the Bal-enid&e are often spoken of as the " toothless"
Whales, whilst the other two families are called the "toothed"
Whales (Odontoceti).
Fig. 2II.-Skull of the Right Whale (Balrza mnystice/us)-after Owen.
Eaam. I. Balcenidc. -The Balaenidce or Toothless Whales
are characterised by the total absence of teeth in the adult
(fig. 2II).  Teeth, however, are present in the fcetal Whale,
but they never cut the gum. The place of teeth is supplied
by a number of plates of whalebone or " baleen " attached to
the palate; hence the name of "whalebone Whales" often
given to this family. They are the largest of living animals,
and may be divided into the two sections of the Smooth Whales,
in which the skin is smooth and there is no dorsal fin (as in
the Greenland Whale), and the Furrowed Whales, in which
the skin is furrowed and a dorsal fin is present (as in the socalled Finner Whales and Hump-backed Whales).
The Greenland or " Right" Whale (Balcana mysticetus) will
illustrate almost all the leading points of interest in the family.
The Greenland Whale is the animal which is sought after in
the whale-fishery of Europe, and hence the name of "Right "
Whale often applied to it.  It is an inhabitant of the Arctic
seas, and reaches a length of from forty to sixty feet. Of this
enormous length, nearly one-third is made up of the head, so
that the eye looks as if it were placed nearly in the middle of
the body, The skin is completely smooth, and is destitute of




546             MANUAL OF ZOOLOGY.
hairs in the adult. The fore-limbs are converted into "flippers " or swimming-paddles, but the main organ of progression
is the tail, which often measures from twenty to twenty-five
feet in breadth.  The mouth is of enormous size, the upper
jaw somewhat smaller than the lower, and both completely
destitute of teeth.  Along the middle of the palate runs a
strong keel bordered by two lateral depressions, one on each
side. Arranged transversely in these lateral depressions are
an enormous number of horny plates, constituting what is
known as the "baleen" plates, from which the whalebone of
commerce is derived. The arrangement of the plates of baleen
is somewhat as follows (fig. 212): —Each plate is somewhat
triangular in shape, the shortest side or base being deeply
sunk in the palate.  The outer edge of the plate is nearly
straight, and is quite unbroken.  The innei edge is slightly
concave, and is furnished with a close fringe formed of detached
fibres of whalebone. For simplicity's sake each baleen-plate
has been regarded here as a single plate, but in reality each
plate is composed of se eral pieces, of which the outermost is
by far the largest, whilst the others gradually decrease in size
towards the middle line of the palate.  The large marginal
plates are from eight to ten or fourteen feet in length, and
there may be about two hundred on each side of the mouth.
The object of the whole series of baleen-plates with which
the palate is.furnished, is as follows:-The Whale is a strictly
carnivorous or zoophagous animal, but owing to the absence
of teeth; and the comparatively small calibre of the esophagus,
it lives upon very diminutive animals.  The Whale, in fact,
lives mostly upon the shoals of small Pteropodous Molluscs,
Ctezophora and Mledussce, which swarm in the Arctic seas. To
obtain these, the Whale swims with the mouth opened, and
thus fills the mouth with an enormous mass of water.  The
baleen-plates have tlhe obvious function of a " screening-apparatus." The water is strained through the numerous plates of
baleen, and all the minute animals which it contains are arrested and collected together by the inner fibrous edges of the
baleen-plates.  When, by a repetition of this process, the
Whale has accumulated a sufficient quantity of food within the
central cavity of the mouth, it is enabled to swallow it, without taking the water at the same time.
We have now to speak of a phenomenon which has given
rise to a considerable amount of controversy-namely, what is
known as the " blowing " or " spouting " of the whale. In all
the Cetaceans the nose opens by a single or double aperture
(the latter in the Ratleniad) upon the top of the head, and




CETACEA.                          5 7
these external apertures or nostrils are known as the " blowholes" or "spiracles."   The act known to the whalers as
"blowing" consists in the expulsion from the blow-holes of a
jet of what is apparently water, or at any rate looks like it. The
act is performed by the whale upon rising to the surface, and
it is usually by this that the whereabouts of the animal is discovered.   The old view as to what takes place in the act of
blowing is, that the whale is really occupied in getting rid of
the surplus water which it has taken in at the mouth and
strained through the baleen-plates. The modern and doubtless correct view, however, is, that the water which has been
strained through the baleen really makes its escape at the side
F.g. 2x2.-Diagram of the Baleen-plates of a Whale. a a Section of the palatal sur.
face of the upper jaw, showing the strong median ridge or keel; b b Baleen-plates,
sunk at their bases in the palate; ff Fibrous margin of Baleen-plates.
of the mouth, an  does not enter the pharynx to be expelled
through the nose.  Upon this view the apparent column of
water emitted from the blow-holes in the act of blowing consists really of the expired air from the lungs, the contained
watery vapour of which is suddenly condensed on its entrance
into the cold atmosphere. With the expired air there may be
such water as may have gained access to the nose through the
blow-hole, for the expulsion of which proper provision exists




548             MANUAL OF ZOOLOGY.
in the form of muscular diverticula of the nasal cavity.  It is
also possible that the column of air in being forcibly expelled
from the blow-hole may take up with it some of the superincumbent water.
The skin in the Right Whale is perfectly smooth and naked,
but it is underlaid by a thick layer of subcutaneous fat, which
varies from eight to fifteen inches in thickness, and is known
as the "blubber." The blubber serves partly to give buoyancy to the body, but more especially to protect the animal
against the extreme cold of the medium in which it lives. It
is the blubber which is chiefly the object of the whale-fishery,
as it yields the whale-oil of commerce.
The whale which is captured in the Antarctic regions is not
the same species as the Greenland Whale, and is termed the
_Balzna australis.  It is much about the size of the Right
Whale, averaging about fifty feet, but the head is proportionately smaller. This whale is an inhabitant of the greater part
of the Pacific out of the regions of the tropics; but it is chiefly
captured when approaching land, which the females do for the
purpose of bringing forth their young.
The only remaining members of the Balanid& which require
notice are the Rorquals and Hump-backed Whales, constituting the group of the " Furrowed " Whales. These are collectively distinguished by having the skin furrowed or plaited to
a greater or less extent, whilst the baleen-plates are short, and
there is a dorsal fin.  The specific determination of these
animals is a matter of great difficulty, but there would appear
to be probably three well-marked genera — I. The genus
fegaptfera, including the so-called Hump-backed Whales, in
which the flippers are of great length, from one-third to onefifth of the entire length of the body.  2. The genus Baeunoptera, comprising the so-called Rorquals or Piked Whales, in
which the flippers are of moderate size.  3. The Finner
Whales proper (Physalus).
In all these genera there is a dorsal adipose fin, so that they
are all "Finner" Whales. The Balonoplerxe reach a gigantic
size, being sometimes as much as eighty or one hundred feet
in length. They are very active animals, however, and their
whalebone is comparatively valueless, so that the whalers
rarely meddle with them, though they are not uncommon, and
are often driven ashore on our own coasts.
Eram. 2. Catodontidcl. —The family of the Catodonlidxe or
Physeteridga comprises the Sperm Whales or Cachalots, with
which we commence the series of the Toothed Whales (Odonboceti). They are characterised by the fact that the palate is




CETACEA.                       549
destitute of baleen plates, and the lower jaw possesses a series
(about fifty-four) of pointed conical teeth, separated by intervals, and sunk in a common alveolar groove, which is only imperfectly divided by septa. The upper jaw is also in reality
furnished with teeth, but, with a single partial exception, these
do not cut the gum.
Fig. 2i3.-Spermaceti Whale (Pkyseter macrocePihalus).
The best-known species of this family is the great Cachalot
or Spermaceti Whale (Physeter macrocekphcaus, fig. 2I3).  This
animal is of enormous size, averaging from fifty to seventy feet
in length, but the females are a good deal smaller than the
males.  The head is disproportionately large, as in the Ba'lcezidt?, forming nearly one-third of the entire length of the body.
The snout forms a broad truncated muzzle, and the nostrils
are placed near the front margin of this.  The Sperm Whales
live together in troops or "schools," and they are found in
various seas, especially in the North Pacific. They are largely
sought after, chiefly for the substance known as "spermaceti;"
but besides this they yield oil and the singular body called
"ambergris."  The spermaceti is a fatty substance, which has
the power of concreting when exposed to the air, being in life
a clear white oily liquid. It is not only diffused through the
entire blubber, but is also contained in special cavities of the
head.  The sperm-oil yielded by the blubber is exceedingly
pure, and is free from the unpleasant odour of ordinary whaleoil. The ambergris is a peculiar substance which is found in
masses in the intestine, and is probably of the nature of a
biliary calculus, since it is said to be composed of a substance
very nearly allied to cholesterine. It is used both as a perfume itself, and to mix with other perfumes.
Faim. 3. Delphinida.- This family includes the Dolphins, Por
poises, and Narwhal, and is characterised by usually possessing
teeth in both jaws: the teeth being numerous, and conical in
shape. The nostrils, as in the last family, are united, but they
are placed further back, upon the top of the head. The single
blow-hole or nostril is transverse and mostly crescentic or lunate




550              MANUAL OF ZOOLOGY.
in shape. The head is by no means so disproportionately large
as in the former families, usually forming about one-seventh of
the entire length of the body.
Fig. 214. —The common Dolphin (Defihinus delAhis).
Th6 most noticeable members of this family are the true
Dolphins, the Pcrpoises, and the Narwhal.
The Dolphins have an elongated snout, separated from the
head by a transverse depression.  The common Dolphin (Del-.phinus delphis, fig. 2I4) is the best-known species.  It averages from six to eight feet in length, and has the habit of swimming in flocks, often accompanying ships for many miles. The
female, like most of the Cetacea, is uniparous. The Dolphin
occurs commonly in all European seas, and is especially abundant in the Mediterranean.
The common Porpoise (Phoczna communis) is the commonest
and smallest of all the Cetacea, rarely exceeding four feet in
length. The head is blunt, and is not produced into a projecting muzzle. The Porpoise frequents the North Sea, and is
commonly seen off our coasts. Another British species is the
Grampus (Phoccena ora), but this is much larger, attaining a
length of from eighteen to twenty feet. Nearly allied to the
Grampus is the so-called "Caing" Whale, or, as it is sometimes termed, the " Bottle-nosed" Whale (Globicephahis or
Phoccena globiceps). This species occurs not uncommonly
round the Orkney and Shetland Islands, and attains a length
of as much as twenty-four feet. It is gregarious in its habits,
and is often killed for the sake of its oil.
Closely allied to the true Dolphins are two curious Cetaceans,
belonging to different genera, but both inhabiting fresh waters.
One of these is the Gangetic Dolphin (Platanista Ganagetica),
which inhabits the Ganges, especially near its mouth. This
singular animal is characterised by the great length of its
slender muzzle, and by the small size of the eyes. It attains
the length of seven feet, and the blow-hole is a longitudinal
fissure, and therefore quite unlike that of the typical De



UNGULATA.                     551
phinidai. The other fresh-water form is the Znia Boliviensis,
which inhabits the rivers of Bolivia, and is found at a distance
of more than two thousand miles from the sea. In its essential
characters it differs little from its marine brethren, and it
attains a length of from seven (female) to fourteen feet (male).
The last of the J9elphinide is the extraordinary Narwhal or
Sea-unicorn (Monodon monoceros). The Narwhal is an inhabitant of the Arctic seas, and attains a length of as much as
fifteen feet, counting in the body alone. The dentition, however, is what constitutes the great peculiarity of the Narwhal.
The lower jaw is altogether destitute of teeth, and the upper
jaw in the females also exhibits no teeth externally, as a general
rule at any rate, though there are two rudimentary incisors
which do not cut the gum: In the males, the lower jaw is
likewise edentulous, but the upper jaw is furnished with two
molar' teeth concealed in the gum, and with two incisors. Of
these two upper incisors, that of the right side is generally
rudimentary, and is concealed from view. The left upper
incisor, on the other hand, is developed from a permanent
pulp, and grows to an enormous size,. continuing to increase
in length throughout the life of the animal. It forms a tusk of
from eight to ten feet in length, and it has its entire surface
spirally twisted. As an abnormality, both the upper incisors
may be developed in this way so as to form projecting tusks;
and it is stated that the tusk is occasionally present in the
female. The function of this extraordinary tooth is doubtless
offensive.
CHAPTER LXXVII.
UNG UL A TA.
ORDER VI. UN OULATA.-The order of the Unzgulafa, or Hoofed
Quadrupeds, is one of the largest and most important of all the
divisions of the Jfamnalina. It comprises three entire old orders
-namely, the Pachydeirmata, Solidungula, and Ruminantia.
The first of these old divisions-that of the Pachydermnalaincluded tle Elephants, Rhinoceros, Hippopotamus, Tapirs,
and the Pigs, all characterised, as the name implies, by their
thick integuments. The name is still used to express this fact,
though the order is now abandoned, and is merged with that
of the.Ungzulata; the Elephants alone being removed to a
separate order under the name of Proboscidca.




552              MANUAL OF ZOOLOGY.
The second old order-that of the Solidungula or Solipedes
-included the Horse, Zebra, and Ass, all characterised by the
fact that the foot terminates in a single toe, encased in an
expanded hoof.  The name Solidungula is still retained for
these animals, as a section of the Uizgulata.
The third old order-that of the Ruminanfia-includes all
those animals, such as Oxen, Sheep, Goats, Camels, Giraffes,
Deer, and others, which chew the cud or "ruminate," and have
two functional toes to each foot, encased in hoofs. The name
R]iuminantia is still retained for these animals, as constituting
a most natural group of the Un(hgulata.
All these various animals, then, are now grouped together
into the single order of the Unzgulata, or Hoofed Quadrupeds,
and the following are the characters of the order:All the four limbs are present, and that portion of the toe
which touches the ground is always encased in a greatly-ex-'.I
AB           C         D
A                         ~
Fig. 215.-Ungulata. A, Perissodactyle foot of Zebra (Solidtntgura) B, Artiodactyle
foot of Llama; C, Artiodactyle foot of Antelope; D, Perissodactyle foot of Rhinoceros.
panded nail, constituting a "hoof." There are never more
than four full-sized toes to each limb. Owing to the encasement of the toes in hoofs, the limbs are useless for prehension,
and only subserve locomotion; hence clavicles are always wanting in the entire order.  There are always two sets of enamelled
teeth, so that the animal is diphyodont. The molar teeth are
massive and have broad crowns, adapted for grinding vegetable
substances.
The order UnulftCza is divided into two primary sections:the Per-rissoacrlyla, in whiich the toes or hoofs are odd in num



UNGULATA.                     553
ber (one or three), and the Artiodaclyla, in which the toes are
even in number (two or four).
SECTION A. PERISSODACTYLA.-The section of the Perissodactyle Ungulates includes the. Rhinoceros, the Tapirs, the
Horse and its allies, and some extinct forms, all agreeing in
the following characters:The hind-feet are odd-toed in all (fig. 215, A, D), and the
fore-feet in all except the Tapirs. The dorso-lumbar vertebral
are never less than twenty-two in number. The femur has a
third trochanter.   The horns, if present, are not paired.
Usually there is only one horn, but if there are two, these are
placed in the middle line of the head, one behind the other
(fig. 216). In neither case are the horns ever supported by
bony horn-cores. The stomach is simple, and is not divided
into several compartments; and there is a large and capacious
caecum.
The three existing genera of Perissodactyle Ungulates -
namely, the Horse, Tapir, and Rhinoceros-are widely removed from one another in many important characters; but
the intervals between them are filled up by an extensive series
of fossil forms, commencing in the Lower Tertiary Strata.
Farn i. Rhinoeriade.-This family comprises only a single
genus, the genus Rhinoceros, unless, indeed, the little Hyrax
is to be retained in this order.  The Rhinoceroses are extremely large and bulky brutes, having a very thick skin, which
is usually thrown into deep folds. The muzzle is rounded
and blunt, and there are 7-7 molars, with tuberculate crowns.
7-7
There are no canines, but there are usually incisor teeth in
both jaws. The skull is pyramidal, and the nasal bones are
enormously developed. The feet are furnished with three toes
each, encased in hoofs. The nasal bones support one or two
horns, which are not paired. The horn is composed of longitudinal fibres, which are agglutinated together, and are of the
nature of epidermic growths, somewhat analogous to hairs.
When two horns are present, the hinder one is carried by the
frontal bones, and is placed in the middle line of the head
behind the anterior horn. The posterior horn is usually much
shorter than the anterior one; and if not, it differs in shape.
The Rhinoceroses live in marshy places, and subsist chiefly on
the foliage of trees. They are exclusively confined at the present day to the warmer parts of the Old World; but an extinct
species (Rhinoceros tichorhinzus) formerly inhabited England,
and ranged over the greater part of Europe.  Of the one*horned species, the best known is the Indian Rhinoceros (R.




554              MANUAL OF ZOOLOGY.
Indicus), which was probably the "Unicorn" of the ancients.
Another species with one horn (R. Sondaicus) inhabits Java.
Of the two-horned species, one (R. Sumatrensis) is found in
Sumatra, and is remarkable for the comparative absence of
cutaneous folds. The best known, however, is the African
Rhinoceros (R. bicornis), which occurs abundantly in Cape
Colony and in the southern parts of the African continent
(fig. 2I6.)
Fig. 2i6.-Head of two-horned Rhinoceros (R. bicornis).
Faim. 2. Tapirida. —The Tapirs are characterised by the
possession of a short movable proboscis or trunk. The skull
is pyramidal, like that of the pigs, and the nasal bones project
over the nasal cavity. The skin is hairy and very thick. The
tail is extremely short. The fore-feet have four toes each, but
these are unsymmetrical (the little toe being smaller than the
rest and not touching the ground), and the hind-feet have only
three toes, all encased in hoofs. The jaws are furnished with
incisor teeth, (3-3), small canines, and     molars.
Three species of Tapir are known, of which the most familiar is the American Tapir (T. Arnericanus), which inhabits the
vast forests of South America.  It is a large animal, some'
thing like a pig in shape, but brownish black in colour, and
having a mane.  It is nocturnal in its habits, and is strictly
phytophagous. The proboscis is employed in conveying the
food to the mouth, and the nostrils are placed at its extremity.
It attains altogether a total length of from five to six feet.
Another species, with longer hair (T. villosus), inhabits the
Andes, and a still larger species (7:.faliayanus is found in




UNGULATA.                     555
Sumatra and Malacca.  In this last, there is no mane, and
the general colour is black; but the back, rump, and sides of
the belly are white.
Nearly allied to the Tapirs is the fossil genus Palaot/lerium,
found in the Eocene Rocks of France and other countries.
Many species of the genus are known, all seeming to have
possessed a short proboscis like that of the Tapirs. All the
feet, however, were tridactylous.
Fiam. 3. Solidungula or Equide. —This family comprises the
Horses, Asses, and Zebras, characterised by the fact that the
feet have only a single perfect toe each, enclosed in a single
broad hoof, without supplementary hoofs (fig. 216, A). There
is a discontinuous series of teeth in each jaw; and in the
males, canines are present, but these are wanting in the females.
The dental formula is-.
3 —3    I —I     3-3    3-3
i33; c;  im; m3   -=4o.
33 —3;'         3-3   3-3
The skin is covered with hair, and the neck is furnished
with a mane.
The family EVuidee is divided by Dr Gray into two sections
or genera: l41/us, comprising the Horse; and Asinus, comprising the Asses and Zebras.
The genus EquZis is distinguished by the fact that the animal
is not banded, and has no dorsal line; both the fore and hind
legs have warts, and the tail is hairy throughout. The genus
appears to contain no more than one well-marked species, as
far as living forms are concerned-namely, the Equus cabal/us.
From this single species appear to have descended all the innumerable varieties of horses which are employed by man.
The native country of the horse appears to have been Central
Asia, but all -the known wild individuals at the present day
appear to be descendants of domestic breeds.
The genus Asinzus is characterised by the fact that there is
always a distinct dorsal line, and the body is more or less
banded; the fore-legs alone have warts, and the tail has a tuft
of long hairs at its extremity. The Ass is probably a native
of Asia (where the wild Ass is at present a native), and there
appears to be little doubt but that the common Ass is merely
the domesticated form of the wild Ass (Equns onager). An.other well-known species is the mule-like " Djiggetai" (Asimus
hemionus) of Central Asia. The striped members of this section are known as Zebras and Quaggas, and are natives of the
southern parts of Africa.
SECTION B. ARTIODACTYLA.-In this section of the Ungu.
25




556 5MANUAL OF ZOOLOGY.
lates the number of the toes is even-either two or four-and
the third toe in each foot forms a symmetrical pair with the
fourth (Fig. 215, B, C). The dorso-lumbar vertebrae are nineteen in number, and there is no third trochanter on the femur.
If true horns are present, these are always in pairs, and are
supported by a bony horn-core. The antlers of the Deer are
also paired, but they are not to be regarded as true horns.
The stomach is always more or less complex, or is divided
into separate compartments, and the caecum is comparatively
small and simple.
The section Artiodacctyla comprises the Hippopotamus, the
Pigs, and the whole group of the Ruminants, including Oxen,
Sheep, Goats, Antelopes, Camels, Llamas, Giraffes, Deer, &c.
Besides these there is an extensive series of fossil forms commencing in the Eocene or Lower Tertiary period, and in many
respects filling up the gaps between the living forms.
OMN IVORA.
I. HZippopotmide. —This group contains only the single
genus Zlpp5opofamums, characterised by the massive heavy body,
the short blunt muzzle, the large head, and the presence of
teeth of three kinds in both jaws. The incisors are 2-2, the
canines extremely large, x-I  and the molars, 7-7 or 6 --
I —                 7-7   6 —6'
with crowns adapted for grinding vegetable substances. The
upper canines are short, but the lower canines are in the form
of enormous tusks, with a chisel-shaped edge. The feet are
massive, and are terminated by four hoofed toes each. The
eyes and ears are small, and the skin is extremely thick, and
is furnished with few hairs. The tail is very short.
Several extinct species of Hlppopotamus are known, but
there is only one well-established living form, the Hzppopoarnzus amphibius or River-horse, and this is confined to the
African continent. It is an enormously bulky and unwieldy
animal, reaching a length of eleven or twelve feet. It is nocturnal in its habits, living upon grass and small shrubs, and it
swims and dives with great facility. It is found in tolerable
abundance in the rivers of Abyssinia, and occurs plentifully
in South Africa. Another supposed species (Hf. Liberiensis)
occurs on the west coast of Africa, but there is some doubt as
to the specific distinctness of this.
2. Suida.-The group of the Suida, comprising the Pigs,
Iogs, and Peccaries, is very closely allied to the preceding;




UNGULATA.                     557
but the feet have only two functional toes, the other two toes
being much shorter, and hardly touching the ground. All the
three kinds of teeth are present, but they vary a good deal.
The canines always are very large, and in the males they usually constitute formidable tusks projecting from the sides of
the mouth. The incisors are variable, but the lower ones are
always inclined forwards.  The molars vary from three to
seven on each side of the mouth (    or    ). The stoll3-3   7-7
ach is mostly slightly divided, and is not nearly. so complex as
in the Ruminants.  The snout is truncated and cylindrical,
fitted for turning up the ground, and is capable of considerable movement. The skin is more or less abundantly covered
with hair, and the tail is very short, or represented only by a
tubercle.
Of the true Swine, the best known and most important is the
Wild Boar (Sus scrofa), from which it is probable that all our
domestic varieties of swine have sprung. The Wild Boar
formerly inhabited this country, and is still abundant in many
of the forests of Europe. It is often hunted, and the size and
sharpness of its canines render it a tolerably formidable adversary, as is also its congener, the Indian Hog (Sus Indicus).
Another curious form, closely related to the Wild Boar, is the
Babyroussa (Sus Babyrussa), which inhabits the Malayan Peninsula, and some of the islands of the Indian Archipelago. It
is remarkable for the great size and backward curvature of the
upper canines. The upper canines pierce the upper lip in the
males, and their alveoli are directed upwards. The legs are
very long and slender; hence the name "Hog-deer" sometimes applied to it.
The African Wart-hogs, forming the genus Phacochrrus, are
distinguished by having a fleshy wart under each eye. They
inhabit Abyssinia, the Guinea coast, and other parts of Africa.
The American Peccaries (Dicotyles) represent the Swine of
the Old World. They are singular for having only three toes
on the hind-feet, the outer of the two supplemental hoofs being
wanting. The canines are not exserted, there is no tail, and
there is a glandular pouch on the loins secreting a fetid fluid.
They are exclusively confined to America, and the commonest
species is the Collared Peccary (Dicotyles torquatus). They
are not at all unlike small pigs either in their appearance or
in their habits, and they are gregarious, generally occurring in
small flocks.
Forming a kind of transition between the Swine and the true
Ruminants, is the extinct group of the Anoplotheridee, from the




558             MANUAL OF ZOOLOGY.
Lower Tertiary Rocks. The Anoplotheria were slender in
form, with long tails, and feet terminated by two hoofed toes
each, sometimes with small accessory hoofs. The dentition
consisted of six incisors in each jaw, small canines not larger
than the incisors, and seven molars on each side, there being
no interval or diastema between the molars and the canines.
RUMINANTIA.
The last section of the Artiodactyle Ungulates is the great
and natural group of the Ruminantia, or Ruminant animals.
This section comprises the Oxen, Sheep, Antelopes, Giraffes,
Deer, Camels, &c., and is distinguished by the following characters:
Tle foot is what is called " cloven," consisting of a symmetrical pair of toes encased in hoofs, and looking as if produced
by the splitting into two equal parts of a single hoof. In addition to these functional toes, there are sometimes two smaller
supplementary hoofs, placed at the back of the foot. The
metacarpal bones of the two functional toes of the fore-limb,
and the metatarsal bones of the same toes of the hind-limb,
coalesce to form a single bone, known as the " canon-bone."
The stomach is complex, and is divided into several compartments, this being in accordance with their mode of eating.
They all, namely, ruminate or " chew the cud "-that is to say,
they first swallow their food in an unmasticated or partiallymasticated condition, and then bring it up again, after a longer
or shorter time, in order to chew it thoroughly.
This process of rumination is so characteristic of this group,
that it will be necessary to describe the structure of the
stomach, as showing the mechanism by which this singular
process is effected. The stomach (fig. 217) is divided into
four compartments, which are usually so distinct from one
another that they have generally been spoken of as so many
separate stomachs. The gullet opens at a point situated
between the first and second of these cavities or "stomachs."
Of these the largest lies on the left side, and is called the
"rumen" or "paunch" (fig. 217, r), This is a cavity of very
large capacity, having its interior furnished with numerous
hard papillae or warts. It is the chamber into which the food
is first received when it is swallowed, and here it is moistened
and allowed to soak for some time. The second stomach,
placed to the right of the paunch, is much smaller, and is
known as the "'reticulum" or "honeycomb-bag" (h).  Its
inner surface is reticulated, or is divided by ridges into a




UNGULATA.                        559
number of hexagonal or many-sided cells, somewhat resembling the cells of a honeycomb. The reticulum is small and
globular, and it receives the food after it has lain a sufficient
time in the paunch.  The function of the reticulum is to compress the partially-masticated food into little balls or pellets,
which are then returned to the mouth by a reversed action of
the muscles of the cesophagus. After having been thoroughly
chewed and prepared for digestion, the food is swallowed for
the second time.  On this occasion, however, the triturated
food passes on into the third cavity (J), which is variously
known as the "psalterium," " omasum," or (Scoftict) the "manyplies." The vernacular and the first of these technical names
both refer to the fact that the inner lining of this cavity is
thrown into a number of longitudinal folds, which are so close
as to resemble the leaves of a book. The psalterium opens
by a wide aperture into the fourth and last cavity, the "abomasum" (a), both appearing to be divisions of the pyloric
F..ta~h oah.        r
Fig. 2x7. —Stomach of a Sheep. o Gullet; r R Czeyz or Paunch; h Honeyc-l'-bag or
Reticulum; A Manyplies or Psalteriumzt; a Fourth Stomach or A bozmasumt.
portion of the stomach. The mucous membrane of the abo.
masum is thrown into a few longitudinal folds, and it secretes
the true acid gastric juice.  It terminates, of course, in the
commencement of the small intestine-i.e., the duodenum.
The intestinal canal of Ruminants, as in most aniimals which
live exclusively upon a vegetable diet, is of great relative
length.
The dentition of the Ruminants presents peculiarities almost
as great and as distinctive as those to be derived from the
digestive system. In the typical Ruminants (e.g., Oxen, Sheep.
Antelopes) there are no incisor teeth in the upper jaw, their




560             MANUAL OF ZOOLOGY.
place being taken by a callous pad of hardened gum, against
which the lower incisors impinge (fig. 2I8).  There are also
no upper canine teeth, and the only teeth in the upper jaw
are six molars on each side. In the front of the lower jaw is
a continuous and uninterrupted series of eight teeth, of which
the central six are incisors, and the two outer ones are regarded by Owen as being canines.  Upon this view, canine
teeth are present in the lower jaw of the typical Ruminants,
and they are only remarkable for being placed in the same
series as the incisors, which they altogether resemble.in shape,
size, and direction. Behind this continuous series of eight
C   2
Fig. 218.-Skull of a hornless Sheep (after Owen). i Incisors; c Canines;
en Molars and Praemolars.
teeth in the lower jaw, there is a vacant space, which is followed behind by six molars on each side. The prmemolars
and molars have their grinding-surfaces marked with two
double crescents, the convexities of which are turned inwards
in the upper, and outwards in the lower teeth.
The dental formula, then, for a typical Ruminant aninial, is-.o —o    o-o      3-3    3 3
3 3 —3  I-I;       3m 3 —       = 3- 32
The departures from this typical formula occur in the Camelidae
and in some of the Deer.  Most of the Deer conform in their
dentition to the above formula, but a few forms (e.g., the




UNGULATA.                     56I
Musk-deer) have canine teeth in the upper jaw. These upper
canines, however, are mostly confined to the males; and if
they occur in the females, they are of a small size. The dentition-of the Canzelidte (Camels and Llamas) is still more aberrant, there being two canine-like upper incisors and upper
canines as well. The lower canines also are more pointed
and stand more erect than the lower incisors, so that they
are easily recognisable.  The group of the Ruminantia includes the families of the Camelidae (Camels and Llamas), the
Moschidae (Musk-deer), the Cervide (Deer), the Carnelopardalidce (Giraffe), and the Cavicornia (Oxen, Sheep, Goats, Antelopes).
a. Camelid&e.-The Camels and Llamas constitute in many
respects an aberrant group of the Ruminantia, especially in
their dentition, the peculiarities of which have been spoken of'
above, and need not be repeated here. In their feet, too, the
Carnmeidi are peculiar.  The feet are long and terminate in
only two toes, which are covered by an imperfect nail-like
hoof, covering no more than the upper surface of each toe.
The two hinder supplementary toes, which are mostly present in the Ruminants, are here altogether wanting; and the
soles of the feet are covered by a callous horny integument,
by which the two toes of each foot are conjoined, and upon
which the animal walks.  The head in all the CameZlidle is
destitute of horns, and the nostrils can be closed at the will of
the animal.
The true Camels are peculiar to Asia and Africa, and two
species are known, distinguished from one another by the
possession of.a double or single adipose hump on the back.
The African or Arabian Camel (Camelus Droamedarius) is often
called the Dromedary, and has only one hump on its back.
The two toes are united together by the callous sole; and the
chest, shoulders, and knees are furnished with callous pads,
upon which they rest when they lie down. The hump is
almost entirely composed of fat, and appears to act as a kind
of reserve supply of food, as it is noticed to diminish much in
size upon long journeys. The Camel can likewise support a
very prolonged privation of water, as the paunch is furnished
with large cells, which the animal fills when it has access to
water, and then makes use of subsequently as occasion may
require. The structure of the Camel adapts it admirably for
locomotion in the sandy deserts of Arabia and Africa; and as
it is very tlocile and good-tempered, it is almost exclusively
employed as a. beast of burden in the countries in which it
occurs.




562'MANUAL OF ZOOLOGY.
The Bactrian Camel (C. Bacfrianus) is distinguished by the
possession of two humps; but in other respects it does not
differ from  the Dromedary.  The two species are said to
breed together, and the hybrid offspring is stated to be occasionally fertile. The place of the Camels is taken in the New
World by the Llama and Alpaca, with two other nearly-allied
forms. These animals form the genus Auc/enia, and are in
many respects similar to the true Camels. They are distinguished, however, by having no hump upon the back, and by
the fact that the two toes are not conjoined and supported by
a callous pad, as in the Camels, but are separate, with separate
pads, and with strong curved nails. -The neck is long and
the head comparatively small, whilst the upper lip is mobile
and deeply cleft vertically. The Llamas are chiefly found in
Peru and Chili, and considerable doubt exists as to the number of species. They live in flocks in mountainous regions,
and are much smaller than the Camels in size. The true
Llama is kept as a domesticated animal, and used as a beast
of burden. The Alpaca is still smaller than the Llama, and
is not very unlike a sheep, having a long woolly coat. It is
partially domesticated, and the wool is largely imported into
Europe.
b. Moschide. —The second group is that of the Musk-deer,
characterised by the total absence of horns in both sexes, and
by the presence of canines in both jaws, those in the upper
jaw being in the form of tusks in the males, but being much
smaller in the females.
The true Musk-deer (Afoschlus moschicerus) is an elegant
little animal, which inhabits the elevated plains of central
Asia. It is remarkable for the fact that the male has a glandular sac on the abdomen, by which the well-known perfume,
musk, is secreted. The musk-gland is wanting in the Napu
(Afoschlus Javanicus) of Java, and also in the little Kancliil
(Tragulus pyjmomzus), which is the smallest of living Ruminants.
c. Cervidce.-This family is of much greater importance than
that of the MAfoschidae, including as it does all the true Deer.
They are distinguished from the other Ruminants chiefly by
the nature of the horns. With the single exception of the
Reindeer, these appendages are confined to the males amongst
the Cerivide, and do not occur in the females. They do not
consist, as in the succeeding group, of a hollow sheath of horn
surrounding a central bony core, nor are they permanently retained by the animal. On the other hand, the horns-or, as
they are more properly called, the antl/ers-of the Cervidae are
deciduous, and are solid. They are bony throughout, and are




UNGULATA.                      563
usually more or less branched (fig. 2I9), and they are annually
shed and annually reproduced at the breeding season. - They
increase in size and in the number of branches every time they
are reproduced, until in the old males they may attain an enormous size. The first time they are produced, the horns are
in the form of simple cylindrical shafts; the second year's
horns have one or two " tynes," and so on. The antlers are
carried upon the frontal bone, and are produced by a process
not at all unlike that by which injuries of osseous structures
are made good in man. At first the antlers are covered with a
Fig. 2i9.-Head of the Red-deer (Cervus elaihus).
sensitive hairy skin; but as development proceeds, the vessels
of the skin are gradually obliterated, and the skin dies and peels
off. In all the Deer there is a sebaceous gland, called the
"lachrymal sinus," or "larmier," which is placed beneath each
eye, and secretes a stronily-smelling waxy substance.
The Cervidce are very generally distributed, but no member
of the group has hitherto been discovered in either Australia
or South Africa, their place in the latter continent seeming to
be taken by the nearly-allied Antelopes (distinguished by their
hollow horns).




564             MANUAL OF ZOOLOGY.
Very many species of Cervide are known, and it is not possible to allude to more than two or three of the more familiar
and important forms. Three species occur in Britain-namely,
the Roebuck, Red-deer, and Fallow-deer, the last being a
doubtful native. The Roebuck (Capreolus caprcea) was once
very generally distributed over Britain, but is almost confined
to the wilder parts of Scotland at the present day. It is of
small size, and the horns are without brow-tynes, and are
of small size, with three terminal branches.  The Red-deer,
or Stag (Cervus ebiehus) is a much larger species, with welldeveloped spreading antlers. The Red-deer of Britain is represented in North America by a still larger species, known as
the Wapiti (Cervus Canadensis).
The third British species is the Fallow-deer (Danma platyceros),
characterised by the fact that the antlers are palmated-that
is, dilated towards their extremities. It is a doubtful native,
and is never found in a wild state at the present day. Allied
to the Fallow-deer is a gigantic extinct species, the Megaccros
Hibernicius, which inhabited Ireland, the Isle of Man, Scotland, and probably the greater part of Europe, up to a comparatively modern date, probably having survived into the
human period. It is often, but incorrectly, spoken of as the
Irish "Elk," but it is really a genuine Stag.  The animal ivas
of very great size, and was furnished with enormous spreading
and palmate antlers, which measure from ten to twelve feet
between the tips.
Of all the Deer, the largest living form is the true Elk (Aiccs
palmatus), which is generally distributed over the northern
parts of Europe, Asia, and America, being often spoken of as
the Moose. The antlers in the Elk are of a very large size, and
are very broad, terminating in a series of points along their
outer edges.
The only completely domesticated member of the C'rvizile
is the Reindeer (Cervus tarandus), which is remarkable for
the fact that the female is furnished with antlers similar to, but
smaller than, those of the males. At the present day the Reindeer is exclusively confined to the extreme north of Europe and
Asia, abounding especially in Lapland. Remains, however, of
the Reindeer are known to occur over the greater part of Europe,
extending as far south, at any rate, aS the Alps, and occurring
also in Britain. From this fact, taken along with many others,
the existence of an extremely cold climate over the greater
part of Europe at a comparatively recent period may be safely
inferred. The Reindeer lives chiefly upon moss and a peculiar kind of lichen (i/iczen rang-iferina), and they are exten



UNGULATA.                     565
sively used by tne Laplanders both as beasts of -burden and as
supplying food.
lThe so-called " Brockets," such as the Guazu-pita (Subudo
rufus) of South America, have simple horns in the form of a
stiletto. Lastly, the singular Muntjak of Java has the horns
supported on long bony pedicles springing from the frontal
bone; and the males have large upper canines.
d. Came/o pardazidae. -This family includes only a single
living animal-the Came/ojardalis Giraffa, or Giraffe-sometimes called the Camelopard, from the fact that the skin is
spotted like that of the Leopard, whilst the neck is long, and
gives it some distant resemblance to a Camel. There are no
upper canines in the Giraffe, and both sexes possess two small
frontal horns, which, however, are persistent, and remain permanently covered by a hairy skin, terminated by a tuft of long
stiff bristles. The neck is of extraordinary length, but, nevertheless, consists of no more than the normal seven cervical
vertebra. The fore-legs appear to be much longer than the
hind-legs, and all are terminated by two toes each, the supplementary toes being altogether wanting. The tongue is very
long and movable, and is employed in stripping leaves off the
trees. The Giraffe is the largest of all the Ruminants, measuring- as much as from fifteen to eighteen feet in height.  It is a
harmless and inoffensive animal, but defends itself very effectually, if attacked, by kicking. It is found in Nubia, Abyssinia,
and the Cape of Good Hope.
Remains of gigantic Ruminants allied to the Giraffe have
been found in France and Greece (He//adotiherium); but the
Sivatlherium, sometimes referred to this family, appears to have
been more nearly allied to the true Antelopes.
e. Caviorwnia. —The last family of the Ruminants is tllat of
the Cavicornia or BovidaE, comprising the Oxen, Sheep, (Goats,
and Antelopes. This family includes the most typical Ruminants, and those of most importance to man. The upper jaw
in all the Cavicornia is wholly destitute of incisors and canines,
the place of which is taken by the hardened gum, against
which the lower incisors bite.  There are six incisors and two
canines in the lower jaw, placed in a continuous series, and the
molars are separated by a wide gap from the canines. There
are six molars on each side of each jaw. Both sexes have
horns, or the males only may be horned, but in either case
these — appendages are very different to the "antlers" of the
Cervird. The horns, namely, are persistent, instead of being
deciduous, and each consists of a bony process of the frontal
bone-or "horn-core"-covered by a sheath of horn. The




566             MANUAL OF ZOOLOGY.
feet are cleft, but are furnished with accessory hoofs placed on
the back of the foot.
The Cavicornia comprise the three families of the A4ntilopidtie,
OvidcZ, and Bovidce. The Antelopes form an extremely large
section, with very many species. They are characterised by
their slender deer-like form, their long and slender legs, and
their simple cylindrical annulated or twisted horns, which are
sometimes confined to the males, but often occur in the females
as well (fig. 220). The Antelopes must on no account be confounded with the true Deer, to which they present many points of
similarity. The structure of the horns, however, is quite sufficient to distinguish them. The Antelopes are further distinguished by rarely having a beard or dew-lap, and by the
general possession of "inguinal pores " and "lachrymal sinuses."
Fig. 220.-Head of the Koodoo (Strelsiceros Koodoo).
The inguinal pores are the apertures of two involutions of the
integument of the groin, secreting a viscous substance, the use
of which is unknown. The lachrymal sinuses, or "tearpits,"
have already been mentioned as occurring in the Cervide, and
are not found in any of the Cavicornia except the Antelopes.
Each consists of a sebaceous sac placed beneath the eye, and
secreting a yellowish waxy substance. The function of these
glands is uncertain, but it is probably sexual. The Antelopes
are especially numerous, both in individuals and in species, in
Africa, in which country they appear to take the place of the
true Deer (only one species of Deer being indigenous to
Africa). Amongst the better-known African species of Antelopes are the Springbok, Hartebeest, Gnu, Eland, and Gazelle.'The only European Antelope is the Chamois (Rllpicapra tra



UNGULATA.                     567
gus), which inhabits the Alps and other mountain-ranges of
southern Europe. Amongst the more remarkable Antelopes
may be mentioned the Prong-buck (Antilope furcifer) of N.
America, in which there are no accessory hoofs, lachrymal
sinuses, or inguinal pores; the females are hornless, and the
horns of the male have a snag or branch in front. Another
curious form is the Chickara (A. quadricornis) of India, in
which the females are hornless, but the males have four
horns.
The Sheep and Goats (Ovide) have mostly horns in both
sexes, and the horns are generally curved, compressed, and
turned more or less backwards. The body is heavier, and the
legs shorter and stouter, than in the true Antelopes. In the
true Goats (Capra) both sexes have horns, and there are no
lachrymal sinuses. The throat is furnished with long hair,
forming a beard; and this appendage is usually present in both
sexes, though-sometimes in the males only. The goats live iii
herds, usually in mountainous and rugged districts. The domestic Goat ( Capra hircus) is generally believed to be a descendant of a species which occurs in a wild state in Persia and
in the Caucasus (the " Paseng," or Capra aegagrus). The true
sheep (Ovis) are destitute of a beard, and the horns are generally twisted into a spiral.  Horns may be present in both
sexes, or in the males only.'  Lachrymal sinuses are invarinb-ly absent. Numerous varieties of the domestic Sheep
(Ovis aries) are known, but it is not certainly known from what
wild species these were originally derived. The Merino Sheep
(a Spanish breed) and the Thibet Sheep are particularly celebrated for their long and fine wool. With the exception of
one species (the Big-horn, Ovis nontana), all the Sheep appear
to be originally natives of the Old World.
The true Oxen (Biovid2e) are distinguished by having simply
rounded horns, which are not twisted in a spiral manner.
There are no lachrymal sinuses. Most of the Oxen admit of
being more or less completely domesticated, and some of them
are amongst the most useful of animals, both as beasts of
burden and as supplying food. The parent-stock of our numerous breeds of cattle is not known with absolute certainty;
the nearest approach to British Wild Cattle being a celebrated
breed which is still preserved in one or two places. These
" Chillingham Cattle" are a fine wild breed, which at one time
doubtless existed over a considerable part of Britain. They
are pure white, with a black muzzle, the horns white, tipped
* In the Merino Sheep, and in some other breeds also, the males only
are horned.




568            MANUAL OF ZOOLOGY.
with black. Another large Ox, which formerly existed in Britain, and abounded over the whole of Europe, is the Aurochs
or Lithuanian Bison (Bos bison). The Aurochs is of very large
size, considerably exceeding the common Ox in bulk. It still
occurs in the forests of the Caucasus in a wild state, but it no
longer occurs wild in Europe, if we except a herd maintained
by the Czar in one of the forests of Lithuania. Nearly allied
to the Aurochs is. the American Bison or Buffalo (.Bison Americanus). This species formerly occurred in innumerable herds
in the prairies of North America, but it has been gradually
driven westwards, and has been much reduced in numbers.
It has an enormous head, a shaggy mane, and a conical
hump between the shoulders. Two other very well known
forms are the Cape Buffalo (Buba/lus Cayfer) and the common
Buffalo (Bubalus buIbalis).  The former of these occurs in
southern and eastern Africa, and the latter is domesticated in
India and in many parts of the south of Asia. The horns in
both species are of large size, and their bases are confluent, so
that the forehead is protected by a bony plate of considerable
thickness.
Amongst the more remarkable Asiatic Oxen may be mentioned the Zebu (Bos tauruzs, var. JIldiclls), distinguished by the
fatty hump over the withers at the back of the neck, and the
Yak (Bos grunniens) of Thibet, remarkable for its long silky tail.
The last of the Oxen which deserves notice is the curious
Musk-ox (Ovibos moschatus). This singular animal is at the
present day a native of Arctic America, and is remarkable for
the great length of the hair. It is called the Musk-ox, because
it gives out a musky odour. Like the Reindeer, the Musk-ox
had formerly a much wider geographical range than it has at
present; the conditions of climate which are necessary for its
existence having at that time extended over a very much
larger area than at present. The Musk-ox, in fact, in Posttertiary times is known to have extended over the greater part
of Europe, remains of it occurring abundantly in certain of
the bone-caves of France.
CHAPTER LXXVIII.
HYRA COIDEA  AND PROBOSCIDEA.
ORDER VII. HYRACOIDEA.-This is a very small order which
has been constituted by Huxley for the reception of two or




PROBOSCIDEA.                   $69
three little animals, which make'up the single genus Hyrax.
These have been usually placed in the immediate neighbourhood of the Rhinoceros, to which they have some decided
affinities, and they are still retained by Owen in the section of
the Perissodactyle Ungulates.
The order is distinguished by the following characters:There are no canine teeth, and the incisors of the upper jaw
are long and curved, and grow from permanent pulps, as they
do in the Rodents (such as the Beaver, Rat, &c.) The molar
teeth are singularly like those of the Rhinoceros. According
to Huxley, the dental formula of the aged animal is-..2-2   0-0       4 —4   3-3
z —;'c;' -           -:n 36.
2-2   0-0;  4 —4   3 —3
The fore-feet are tetradactylous, the hind-feet tridactylous,
and all the toes have rounded hoof-like nails, with the exception of'the inner toes of the hind-feet, which have an
obliquely-curved nail. There are no clavicles. The nose and
ears are short, and the tail' is represented by a mere tubercle.
The placenta is deciduate and zonary, whereas in the Ungulates
it is non-deciduate.
Several species of Hyrax are known, but they resemble one
another in all essential particulars. They are all gregarious
little animals, living in holes of the rocks, and capable of
domestication.  One species is said to be arboreal in its
habits. The "' coney" of Scripture is believed to be the Iflyrax
Syriacus, which occurs in the rocky parts of Syria and Palestine. Another species-the Rtyrax Capensis, or " Klipdas"
-occurs commonly in South Africa, and is known by the colonists as the " badger."
ORDER VIII. PROBOSCIDEA. —The eighth order of Mammals
is that of the Proboscidea, comprising no other living animals
except the Elephants, but including also the' extinct AMastodon
and Deiiotherium.
The order is characterised by the total absence of cafiine
teeth; the molar'teeth are few in number, large, and transversely ridged or tuberculate; incisors are always present, and
grow from persistent pulps, constituting long tusks (fig. 221).
In living Elephants there are two of these tusk-like incisors in
the upper jaw, and the lower jaw is without incisor teeth. In
theDeinotherium this is reversed, there being two tusk-like lower
incisors and no upper incisors. In the Mastodons, the incisors
are usually developed in the upper jaw, and form tusks, as in
the Elephants, but sometimes there are both upper and lower
incisors, and both are tusk-like.  The nose is prolonged into a




570               MANUAL OF ZOOLOGY.
cylindrical trunk, movable in every direction, highly sensitive,
and terminating in a finger-like prehensile lobe (fig. 22I). The
nostrils are placed at the extremity of the proboscis. The feet
are furnished with five toes each, but these are only partially
indicated externally by the divisions of the hoof. The feet are
furnished with a thick pad of integument, forming the palms
of the hand and the soles of the feet.  There are no clavicles.
The testes are abdominal throughout life. There are two teats,
and these are placed upon the chest. The placenta is deciduate and zonary.,'  XJ
otIan....u
Fig. 221.-Skull of the Indian Elephant (Elek&as!naicus). i Tusk-like upper incisors; vm Lower jaw, with molars, but without incisors; i Nostrils, placed at the
end of the proboscis. (After Owen.)
The recent Elephants are exclusively confined to the tropical
regions of the Old World, in the forests of which they live
in herds.  Only two living species are known-the Asiatic
Elephant (Eleplas Indicus) and  the African  Elephant (E.
Africanits).  There can be no doubt, however, but that the
Mammoth (E/ep/as primigetzius) existed in Europe within the
human period.
In both the living Elephants the " tusks " are formed by an




PROBOSCIDEA.                   57I
enormous development of the two upper incisors. The milktusks are shed early, and never attain any very great size. The
permanent tusks grow throughout the life of the animal, and
often reach six or seven feet in length, and from fifty to seventy
pounds in weight. In the Indian Elephant, and its variety
the Ceylon Elephant, the males alone have well-developed
tusks, but both sexes have tusks in the African species, those
of the males being the largest. The lower incisors are absent,
and there are no other teeth in the jaws except the large molars,
which are one or two in number on each side of each jaw. The
molar teeth are of very large size, and are composed of a
number of transverse plates of enamel united together by
dentine. In the Indian Elephant the transverse ridges of
enamel are narrow  and undulating, whilst in the African
Elephant they enclose lozenge-shaped intervals. The Indian
Elephant is the only species which is now caught and domesticated, and as it will not breed in captivity, the demand for
it is supplied entirely by the capture of adult wild individuals,
which are taken chiefly by the assistance of those which have
been already tamed. The Indian Elephant is distinguished
by its concave forehead, its small ears, and the characters of
the molars. Its skull is pyramidal, and it has five hoofs on the
fore-feet, and only four on the hind-feet. Its colour is generally pale brown.  (The so-called "White Elephants" are
merely albinos.) The African Elephant, on the other hand,
has a strongly convex forehead and great flapping ears. Its
colour is darker, its skull is rounded, and it has four hoofs on
the fore-feet, and only three on the hind-feet. The African
Elephant is chiefly hunted for the sake of its ivory, and there
is too much reason to believe that the pursuit will ultimately
end in the destruction of these fine animals. A great deal,
however, of the ivory of commerce comes from Siberia, and is
really derived from the tusks of the now extinct Mammoth,
which formerly inhabited the north of Asia in great numbers.
The Elephants are all phytophagous, living almost entirely
on the foliage of shrubs and trees, which they strip off by
means of the prehensile trunk. As the tusks prevent the
animal from drinking in the ordinary manner, the water is
sucked up by the trunk, which is then inserted into the mouth,
into which it empties its contents.
Many species of fossil Elephants are known, but the most
familiar of them is the Mammoth (EZlpihas prirzzeniuls).  This
enormous animal is now wholly extinct, but it formerly
abounded in the northern parts of Asia and over the whole
of Europe. It occurred also in Britain, and unquestionably




572             MANUAL OF ZOOLOGY.
existed in the earlier portion of the human period, its remains
having been found in a great number of instances in connection with human implements. From its great abundance in
Siberia,. it might have been safely inferred that the Mammoth
was able to endure a much colder climate than either of the
living species. This inference, however, has been rendered
a certainty by the discovery of the body of more than one
Mammoth embedded in the frozen soil of Siberia. These
specimens had been so perfectly preserved that even microscopical sections of some of the tissues could be made; and
in one case even the eyes were preserved. From these specimens we know that the body of the Mammoth was covered
with long woolly hair.
Closely allied to the true Elephants are the JMaslodons,
characterised by the fact that the crowns of the molar teeth
have nipple- shaped tubercles placed in pairs.  Generally
speaking, the two upper incisors formed long curved tusks, as
in the Elephants, but in some cases there were two lower
incisors as well. The various species of Mlastodon all belong
to the later Tertiary and Post-tertiary periods.
The last of the Proboscidea is a remarkable extinct animal,
the Deinotherium.  This extraordinary animal has hitherto
only been found in Miocene deposits, and little is known of it
except its enormous skull.  Molars and premolars were present
in each jaw, and the upper jaw
was destitute of canines and incisors.  In the lower jaw were
two very large tusk-like incisors,
which were not directed forwards
as in the true Elephants, but were
bent abruptly downwards (fig. 222).
The animal must have attained an
enormous size, and it is probable
that the curved tusks were used
Fig. 222.-Skull of Deinotheriurn either in digging up roots or in
giganteumz.
mooring the animal to the banks
of rivers, for it was probably aquatic or semi-aquatic in its
habits. It is placed by De Blainville in the Sircnia, being
regarded as a Dugong with tusk-like lower incisors.




CARNIVORA.                    573
CHAPTER  LXXIX.
CA RNlI' VORA.
ORDER IX. CARNIVORA.- The ninth order of Mammals is
that of the Carnivora, comprising the Ferce, or Beasts of Prey,
along with the old order of the Pinnipedia, or Seals and Walruses, these latter being now universally regarded as merely a
group of the Carnivora modified to lead an aquatic life.
The Carnivora are distinguished by always possessing two
sets of teeth, which are simply covered by enamel, and are
always of three kinds-incisors, canines, and molars-differing from one another in shape and size.  The incisors are
generally    (except in some seals); the canines are always
3-3
and are invariably much larger and longer than the inI  I,
cisors. The prxemolars and molars are mostly furnished with
cutting or trenchant edges; but they graduate from a cutting
to a tuberculate form, as the diet is strictly carnivorous, or
becomes more or less miscellaneous. In the typical Carnivores
(such as the Lion and Tiger), the last tooth but one in the
upper jaw and the last tooth in the lower jaw are known as
the " carnassial" teeth, having a sharp cutting edge adapted
for dividing flesh, and generally a more or less developed
tuberculated heel or process. A varying number, however, of
the molars and prmemolars may be " tuberculate," their crowns
being adapted for bruisihg rather than cutting. As a general
rule, the shorter' the jaw, and the fewer the prxemolars and
molars, the more carnivorous is the animal. The jaws are so
articulated as to admit of vertical but not of horizontal movements; the zygomatic arches are greatly developed to give
room for the powerful muscles of the jaws; and the orbits are
not separated from the temporal fossae. The intestine is comparatively short.
In all the Carnivora the clavicles are either altogether wanting, or are quite rudimentary.  The toes are provided with
sharp curved claws. The teats are abdominal; and the placenta is deciduate and zonular.
The order Carnivora is divided into three very natural sections 
Section I. Pinnigrada or Pinnihedia. - This section comprises the Seals and Walruses, in which the fore and hind




574              MANUAL OF ZOOLOGY.
limbs are short, and are expanded into broad webbed swimming-paddles (fig. 223, B). The hind-feet are placed very far
back, nearly in a line with the axis of the body, and they are
more or less tied down to the tail by the integuments.
Section II. Plantzhkrada.-This section comprises the Bears
and their allies, in which the whole, or nearly the whole, cf
the foot is applied to the ground, so that the animal walks
upon the soles of the feet (fig. 223, A).
Section ILL. Digitzgrada. —This section comprises the Lions;
Tigers, Cats, Dogs, &c., in which the heel of the foot is raised
entirely off the ground, and the animal walks upon the tips of
the toes (fig. 223, C).
Fig. 223.-Feet of Carnivora (after Owen). A, Planltgrada, Foot of Bear;
B, Pinnigrada, Hind-feet of Seal; C, Diitiegrada, Foot of Lion.
SECTION I. PINNIGRADA or PINNIPEDIA. -This section of
the Carnivora comprises the amphibious Seals and Walruses,
which differ from the typical Carnivores merely in points connected with their semi-aquatic mode of life. The body in
these forms is elongated and somewhat fish -like in shape,
covered with a short dense fur or harsh hairs, and terminated
behind by a short conical tail. All the four limbs are present,
but are very short, and the five toes of each foot are united
together by the skin, so that the feet form powerful swimmingpaddles.  The hind-feet are of large size, and are placed far
back, their axis nearly coinciding with that of the body (figs.
223, 224). From this circumstance, and from the.fact that the
integument often extends between the hind-legs and the sides
of the short tail, the hinder end of the body forms an admir



CARNIVORA.                     575
able swimming apparatus, similar in its action to the horizontal
tail-fin of the Cetacea and Sirenia.  The tips of the toes are
furnished with strong claws, but their powers of terrestrial locomotion are very limited. On land, in fact, the Seals can only
drag themselves along laboriously, chiefly by the contractions
of the abdominal muscles. The ears are of small size, and
are mostly only indicated by small apertures, which the animal
has the power of closing when under water. The bones are
light and spongy, and beneath the skin is a layer of fat or
blubber. The dentition varies, but teeth of three kinds are
always present, in the young animal at any rate. The canines
are always long and pointed, and the molars are generally
furnished with sharp cutting edges.
Fig. 224.-The Greenland Seal (Phoca Graenlandica).
The section Pinnzgrada includes the two families of the
Seals (P/ocidc) and Walruses (Trichecida).  The Seals are
distinguished by having incisor teeth in both jaws, and by the
fact that the canine teeth are not disproportionately developed.
They form a very numerous family, of which species are found
in almost every sea out of the limits of the tropics. They
abound, however, especially in the seas of the Arctic and
Antarctic regions. They live for the most part upon fish, and
when awake, spend the greater part of their time in the water,
only coming on land to bask and sleep in the sun and to suckle
their young. They appear to be universally polygamous. The
body is covered with a short fur, interspersed with long bristly
hairs; and the lips are furnished with long whiskers. which act
as organs of touch. The Seals are very largely captured for
the sake of tneir blubber.




576             MANUAL OF ZOOLOGY.
The only common British Seal is the Phoca vitulina, which
occurs not uncommonly on the northern shores of Scotland.
It is yellowish-grey in colour, and measures from. three to five
feet in length. Other Seals attain a much greater length-the
Great Seal measuring from eight to ten.feet, and the Bottlenosed Seal reaching a length of from twenty to twenty-five feet.
The only Seals which possess external ears constitute the genus
Otaria, and are almost exclusively confined to the seas of the
southern hemisphere.
The second family of the Pinnigrade Carnivores is that of
the Trichecidae, comprising only the Walrus or Morse (Trichecus rasmarus).  The chief peculiarity by which the Walrus is
Fig. 225.-Skull of the Walrus (Trichecus rosinarus (after Owen).
i Tusk-like upper incisors.
distinguished from the true Seals is found in the dentition.
According to Owen, there are six incisors in the upper jaw
and four in the lower; but these are only present in the young
animal, and soon disappear, with the exception of the outermost pair of upper incisors.  The upper canines are enormously developed, growing from persistent pulps, and constituting two large pointed tusks, which attain a length of over
fifteen inches (fig. 225). The direction of the tusks is downwards and slightly outwards, and they project considerably
below the chin. The adult animal has usually three simple




CARNIVORA.                     577
molars fwith flat crowns behind the tusks in the upper jaw; and
four similar teeth on each side of the lower jaw; but the first
of these has been regarded as a lower canine. The upper lip
has many pellucid bristles as large as a straw in thickness. In
the adult the incisors are obsolete, except the lateral pair in
the upper jaw. Unlike the Seals, the Walrus is not poly —
gamous.
Except as regards its dentition, the Walrus agrees in all
essential respects with the Seals. It is a large and heavy
animal, attaining a length of from ten to fifteen feet or upwards. The body is covered with short brownish or yellowish
hair, and the face bears many long stiff bristles. There are
no external ears. The chief use of the tusk-like canines
appears to be that of assisting the unwieldy animal to get out
of the water upon the ice; but they doubtless serve as weapons
of offence and defence as well. The Walrus is hunted by
whalers, both for its blubber, which yields an excellent oil, and
for the ivory of the tusks. It is found, living in herds, in the
Arctic seas, being especially abundant at Spitzbergen and Nova
Zembla.
SECTION II. PLANTIGRADA. —The Carnivorous animals belonging to this section apply the whole or the greater part of
the sole of the foot to the ground (fig. 223, A); and the portion of the sole so employed is destitute of hairs in most
instances (the sole is hairy in the Polar Bear). From the
structure of the foot, the Plantigrada have great power of rearing themselves up on the hind-feet. They approach the Izsectivora in their comparatively slow movements and their
nocturnal habits, and in possessing no caecum. They mostly
hybernate, and their feet are always pentadactylous.
The typical family of the Plantigrade Carnivora is that of
the Ursitde or Bears, in which the entire sole of the foot is applied to the ground in walking. The Ursidz are much less
purely carnivorous than the majority of the order, and in accordance with their omnivorous habits, the teeth do not exhibit
the typical carnivorous characters. The incisors and canines
have the ordinary carnivorous form, but the "carnassial" or
sectorial molar has a tuberculate crown instead of a sharp
cutting edge. The dental formula is-.3-3    I-I       4-4    2-2
3- C I            4; m  m 33 = 42.
3-31             4-44'  3-3-5
The claws are formed for digging, large, strong, and curved,
but are not retractile. The tongue is smooth; the ears small,




578             MANUAL OF ZOOLOGY.
erect, and rounded; the tail short; the nose forms a movable
truncated snout; and the pupil is circular.
As shown by their smooth tongues and tuberculate molars,
the Bears are not peculiarly or strictly carnivorous. They eat
flesh when they can obtain it, but a great part of their food is
of a vegetable nature.
The Bears are very generally distributed over the globe,
Australia alone having no representative of the family. The
common Brown Bear (Ursus Arctos) was at one time an inhabitant of Britain, and also existed over the whole of Europe.
At the present day the Brown Bear is only found in the great
forests of the north of Europe and in Asia. It feeds on
roots, fruits, honey, insects, and, when it can obtain them, upon
other Mammals. It attains a great age, and hybernates during
the winter months. Very nearly allied to the Brown Bear is
the Black Bear of America (Ursus Americanus).  Both are of
some commercial value, being hunted for the sake of their skins,
fat, and tongues.  A much larger American species is the
Grizzly Bear (Ursusferox), found in many parts of the American continent. It is about twice as large as the ordinary
Bear, but it is said to subsist to a great extent upon vegetable
food, such as acorns. The most remarkable, however, of the
bears is the great White Bear (Thalassarctos maritnuts), which
is exclusively a native of the Arctic regions. It is a very large
and powerful animal, the fur of which is quite white. The
paws are very long, and the soles of the feet are covered with
coarse hair, giving the animal a firm foothold upon the ice.
The Polar Bear differs from the other Ursiaze in being exclusively carnivorous, since vegetable food would be wholly unattainable. It is as much at home in the water as on land,
and lives chiefly upon seals and fish, and upon the carcases of
Cetaceans.
Other well-known Bears are the Syrian Bear (Ursusa Syriacus) of Mount Lebanon, the Sloth Bear (Prochilus labialus) of
India, and the Malayan Bear (Helarctos Malayanus) of Borneo
and Sumatra.
It is a singular fact that the bones of a bear-the Ursus
sjpelacus or Cave Bear-have been found, in Britain and in many
parts of Europe, along with the bones of other Carnivora, such
as the Cave Lion and Cave Hyoena. The Ursus spelceus was
a larger and more powerful animal than even the Polar Bear,
and there can be no doubt that it existed in the earlier portion
of the human period.
Nearly allied to the true Bears are several small animals, of
which the Racoons (Procyon), the Coati (XVasua), the Wah




CARNIVORA.                     579
(Ailurus), and the Kinkajou (Cercolepies) are the best known.
The. Racoons are natives of tropical and northern America,
and have a decided external resemblance to the Bears. They
have tolerably long tails, however, and sharp muzzles.  The
commonest species is the P,rocyon botor of North America, which
derives its specific name from its habit of washing its food
before eating it. The place of the Racoon is taken in India
by the Wah (Aiitrus fuigens), which inhabits northern Hindostan.  It is about the size of a large domestic cat, and is very
prettily coloured, being chestnut brown above, and black inferiorly, with a white face and ears. The Kinkajous (Cercoleptes) are inhabitants of South America, and, as is the case
with so many of the animals of this continent, they are adapted
for an arboreal life, to which end their tails are prehensile.
The Coatis (Naszta) are very closely allied to the Racoons,
and are exclusively confined to the American continent. All
the above-mentioned little animals (with the exception of the
Wah) present a singularly close resemblance to the Lemurs of
the Old World, and appear to be their representatives in the
western hemisphere.  In the genus Paradoxuzrzs of the Indian
Archipelago, the tail is capable of being rolled up, but its extremity is not prehensile.  The " Benturongs" (Arc/ictis) have
a long, hairy, and prehensile tail. They are nocturnal animals
which are found in India, and are in some respects intermediate between the Racoons and the Civets.
The only remaining family of the Plaitigr-ada is that of the
Meli(ie or Badgers, characterised by their elongated bodies
and short legs, and by the fact that the carnassial tooth has a
partly cutting edge, and is not wholly tuberculate as in the
Bears.
The common Badger (Me/es taxus), which may be regarded
as the type of this group, occurs'in Britain, and is one of the
most inoffensive of animals.  It is nocturnal in its habits, and
is a very miscellaneous feeder, not refusing anything edible
which may come in its way, though living mainly on roots and
fruits. The Badger burrows with great ease, and can bite very
severely. The European Badger is represented in the United
States and Canada by the "Siffleur" (Me/es Lnbradoricus),
and in the hilly parts of India by the Indian Badger (M. co/laris).
The Glutton (Gui/o /uscus), often called the Wolverine, is of
common occurrence in the northern parts of Europe, Asia,
and America.  It is from two to three feet in length, and
though doubtless a tolerably voracious animal, it is certainly
not so much so as to deserve the name of Glutton. The
Grison (Gl/o 7/ittalus) is a closely-allied species, which is found
k  216




580             MANUAL OF ZOOLOGY.
in South America. The Ratels or Honey-badgers (Meztivora)
are much like the common Badger in their habits and appearance, but they get their name from their fondness for honey.
They are natives of southern and eastern Africa.
SECTION III. DIGITIGRADA.-In this section of the Carnivora
the heel is raised above the ground, with the whole or the
greater part of the metacarpus, so that the animals walk more
or less completely on the tips of the toes (fig. 223, C). No
absolute line, however, of demarcation can be drawn between
the Plantigrade and Digitigrade sections of the Carnivora, since
many forms (e. g., AMusteidce and iverridce) exhibit transitional
characters, and it has even been proposed to place these in a
separate section, under the name of Semi-plant/igrada.
The first family of the Digiitigrada is that of the MAustelidce
or Weasels, including a number of small Carnivores, with short
legs, elongated worm-like bodies, and a peculiar gliding mode
of progression (hence the name of Vermiformes, sometimes
applied to the group). Amongst the best known of the MAustelide are the common Weasel (Ak/ustela vulgaris), the Pole-cat
(Afustela pulorius), and the Ferret (AMustela furo), the last being
supposed to be only an albino variety of one of the Pole-cats.
It is really an African species, but has been long domesticated
in Europe. Many of the A/ustelidce are of great commercial
importance, furnishing beautiful and highly-valued furs.
Amongst these are the Ermine (AMustela erminea), and the
Sable (Afustela zibe/lina). It is asserted, however, that most of
the Sable of commerce is derived from the Black Mink (Puiorizus nzirescens) and the Pine Marten (Mustela Americana) of
the United States and Canada.
Almost all the Weasels have a very disagreeable odour, produced by the secretion of greatly-developed and modified
sebaceous glands, placed in the neighbourhood of the anus,
and known as the anal glands. In this respect, however, the
nearly-allied genus Al/ephitis, comprising the American Skunk,
is facile princeps. The Skunk is a pretty little animal, with a
long bushy tail, and when unmolested it is perfectly harmless.
If pursued or irritated, however, it has the power of ejecting
the secretion of the anal glands to a greater or less distance
with considerable force.  The odour of this secretion is
so powerful and persistent that no amount of washing will
remove it from a garment, and its characters are said to be of
the most intensely disagreeable description.
Also belonging to the family of the Myustlei&e, and very
nearly allied to the Weasels, are the Otters (Iut/-a), distinguished by the possession of webbed feet adapted for swim



CARNIVORA.                     581
ming. The body is long, the legs short, and the tail long,
stout, and horizontally flattened. The common Otter (Lutra
zvulgaris) is a native of Britain, frequenting. the banks of
streams and lakes. It lives upon fish, and is highly destructive
to Salmon. A closely-allied form is the American Otter (Lutra
Canadensis).  In the Sea Otters (Enhydra) the tail is very
short. They are found on both sides of the North Pacific, and
yield a very valuable fur.
The second family of the Semi-plantigrade Carnivores is that
of the Viverritd', the Civets and Genettes. They are all of
moderate size, with sharp muzzles and long tails, and more or
less striped, or banded, or spotted. The carnassial molar is
trenchant; the canines are long, sharp, and pointed; and the
tongue is roughened by numerous prickly papille.  The claws
are semi-retractile, and the pupils can contract, on exposure to
light, till they resemble a mere line. In most of their characters, therefore, the Civets are much more highly carnivorous
than are any of the preceding families, and they approach in
many respects very close to the typical group of the Dziit/igrada
(viz., the FeZide), having especially very close affinities with
the Hymnas. All the species of the family are furnished with
anal glands, which secrete the peculiar fatty substance kno'wn
as "civet."
The true Civet-cat is the Vierrea civetla, a native of Africa.
It is a small nocturnal animal, which climbs trees with facility,
and feeds chiefly upon small mammals, reptiles, and birds, but
also upon roots and fruits.  It furnishes the greater part of the
" civet" of commerce, which was formerly in great repute both
as a perfume and as a medicinal agent. It is a pomade-like
substance with a strong musky odour, and is secreted by a
deep double pouch beneath the anus.  The Genette (Viverra
genet/a) is very closely related to the preceding, and is a native
of Africa and southern Europe, being not uncommonly domesticated and kept like a cat. The anal pouch in the Genette is much reduced in size, and has hardly any perceptible
secretion.  Another nearly-allied species is the Ichneumon
(Herpestes), which is kept as a domestic animal in Egypt, and
lives upon Snakes, Lizards, the eggs of the Crocodile, and
small Mammals.
Forming a transition between the Viverridee and the Eelide
is the family of the Hytenidej distinguished by the fact that,
atone of all the Carnivora, both pairs of feet have only four
toes each. The hind-legs are shorter than the fore-legs, so that
the trunk sinks towards the hind-quarters, and the tail is short.
The tongue is rough and prickly.  The head is extremely




582             MANUAL OF ZOOLOGY.
broad, the muzzle rounded, and the muscles of the jaw
extremely powerful and well developed. The claws are nonretractile. All the molars are trenchant except the last upper
molar, which is tuberculate. The upper carnassial has a small
internal tubercle, and the lower carnassial is wholly trenchant.
There is a deep glandular pouch beneath the anus.
There are-two well-known species of Hymena, and the whole
group is exclusively confined to the Old World. The bestknown species is the Striped Hyana (Hyaena striata), which is
found in North Africa, Asia Minor, Arabia, and Persia. It is
an ill-conditioned ferocious beast, but will not attack man
unless provoked. The Spotted Hyaena (H, &cocun/a) occurs
solely in Afri'ca, being especially abundant in Cape Colony.
If the so-called Aardwolf (P;roteles) is to be placed amongst the
Hyxenas, as is generally done, then the characters to be drawn
from the feet are not invariable; since this singular animal has
the fore-feet furnished with five toes, whilst the hind-feet are
tetradactylous (as is the case in the Dogs). It is a nocturnal
burrowing animal, and is found in South Africa. The singular
"Hunting Dog " (Lycaon pictus), again, of South Africa, agrees,
with the Hymnas in being tetradactylous, but has no mane,
and approaches the Dogs in its dentition and osteology.
An extinct Hyaena, considerably larger than either of the
living forms, formerly existed in Britain and in various parts
of Europe. It is known as the Cave Hywena (H. spelea), its
remains having been principally found in caves.
The next family is that of the Canid&, comprising the Dogs,
Wolves, Foxes, and Jackals.  The members of this family
are characterised by having pointed muzzles, smooth tongues,
and non-retractile claws.  The fore-feet have five toes each,
6- 6.
the hind-feet have only four. The molar teeth are 767,
7-7
sometimes 7j7, and of these, two or three on each side are
7 —7
tuberculate.  The carnassial has a tolerably large heel or
process.
The true Dogs (i.e., the Dog and Wolf) have round pupils,
and a tail which is of moderate length and rarely very hairy.
The Foxes ( ulpes) have very long bushy tails, and the pupil
contracts to a mere line.
The Dog (Canisfamiliaris) is only known to us at the present
day as a domesticated animal.  Such wild dogs as there are,
are probably merely derived fi-om the domestic dog; and the
original stock, or stocks, from which our numerous varieties of




CARNIVORA.                     583
dogs have sprung, is still uncertain. It is worth while remembering, however, all our varieties of dogs are capable of interbreeding; and there is a strong probability that the Wolf is
the parent stock of at least some of our domestic breeds. The
Dog, in fact, will interbreed with both the Wolf and the Jackal.
Fig. 226.-Skull of Jackal (Canis aureus)
The genus Canis, besides the Dog, contains the well-known
Jackal (Canis aureus), and the Wolf (Canis lupzus), and many
writers place the Foxes in the same genus. The Foxes, however, are better considered as forming a separate genus ( Vules),
of which there are many species, all more or less like the
common Fox ( Vulpes vulgaris).  One of the most remarkable
species is the Arctic Fox, which abounds in the Arctic regions,
and changes its colour with the season, being brown in summer
and white in winter.  The soles of its feet are hairy.  Other
well-known Foxes are the Red Fox (V. fulvus) of North America, the Deccan Fox (V. Bengalensis) of India, and the Caama
( V. Caama) of Africa.
The Jackals have a round pupil and a dental formula like
that of the Dogs. They inhabit Asia and Africa, are gregarious, hunt in packs, and burrow in the ground.
The last group of the Diogitigrada is that of the Fe/lide or
Cat tribe, comprising the most typical members of the whole
order of the Carnivora, such as the Lions, Tigers, Leopards,
Cat, and Panthers. The members of this family all walk upon
the tips of their toes, the soles of their feet being hairy, and
the whole of the metacarpus and heel being raised above the
ground (fig. 223, C). The jaws are short, and owing to this
fact, and to the great size of the muscles concerned in mastication, the head assumes a short and rounded form, with an
abbreviated and rounded muzzle. The molars and prxmolars
are fewer in number than in any other of the Carnivora (hence
the shortness of the jaws), and they are all trenchant, except




j84             MANUAL OF ZOOLOGY.
the last molar in the upper jaw, which is tuberculate. The
upper carnassial has three lobes, and a blunt heel or internal
process. The lower carnassial has two cutting lobes, and no
internal process. According to Owen, the dental formula is3-3    I —1        3-3    I —I; c; Am n.; m — I  = 30.
The legs are nearly of equal size, and the hind-feet have
only four toes each, whilst the fore-feet have five. All the
toes are furnished with strong, curved, retractile claws, which,
when not in use, are withdrawn within sheaths by the action
of elastic ligaments, so as not to be unnecessarily blunted.
Fig. 227. —Skull of Lion (Felis leo).
The tongue is roughened and rendered prickly by the presence
of horny papillae, thus rendering it a most efficient rasp in
licking the flesh from the bones of the prey. All the members
of this group are exceedingly light upon their feet, and are
excessively muscular, and they have all the habit of seizing
their prey by suddenly springing upon it.
It is questionable if any good genera have hitherto been
established in this family, and all the species may be considered as belonging to the single genus Felis.
The Lion (Felis leo) is too well known to require -much special notice. Its colour is always uniform; generally a yellowish or reddish brown. The tail is terminated by a tuft of long
hairs, and the male is Usually furnished with a mane, which is
very short, however, in an Indian form. The Lion is exclusively confined to the Old World, and is an inhabitant of Africa
and all the southern parts of Asia. It is doubtful how far




CARNIVORA.                     585
any valid species of Lions have as yet been established. The
Lions are all nocturnal, and capture their prey by suddenly
leaping upon it.  They are by no means the generous and
courageous animals they are generally considered to be; but,
on the contrary, are cruel, cunning, and cowardly. They are
enormously strong, and it is said that a full-grown Lion can
run, and even leap, though carrying an ox in its jaws. Though
now much restricted in its range, the Lion had formerly a much
more extensive distribution, a form considerably larger than
the modern species having formerly existed in Europe, andeven in Britain (Felis sjeaga).
In the tigers (Felis tzgris), the tail is without a tuft of hairs
at its extremity, and the skin is marked with stripes or spots.
The Royal or Bengal Tiger is a native of southern Asia, but
occurs also in Java and Sumatra. The skin is reddish yellow,
marked with numerous transverse black stripes. It is a large
and powerful animal, and, upon the whole, is probably a more
dangerous opponent than even the Lion.
Of the large Spotted Cats, the largest is the Jaguar (Felis
onca) which inhabits South America and the southern parts of
North America. It is a very large and powerful animal, said
to be able to carry a bullock without difficulty, and it can both
swim and climb with great facility. Another American species
is the Puma (Fells concolor), in which the colour is uniformly
reddish brown.  It is exclusively confined to America, and
though of large size (nine feet in length, including the tail), it
is a very cowardly species, and is seldom or never known to
attack man.
The Leopard (Felis leopardius) is another well-known species,
smaller than the Tiger, and marked with black spots in place
of stripes. It is a native of all the warmer parts of the Old
World.
The Panther is probably merely a variety of the Leopard,
and the Ounce (Felis uncia) is generally believed to be only
its immature form. Another allied form is the Cheetah or
Hunting Leopard (~Felisjubata), of southern Asia and Africa.
Of the smaller Felidoe, the best known are the Lynxes and
the Cats, properly so called. Of these the Lynxes are distinguished by their short tails, and by the fact that the ears are
furnished with a pencil of hairs. The best-known species are
the European Lynx (Fells lyncus), the Caracal (F. caracal) of
southern Asia and Africa, and the Canadian Lynx (F. Canadensis) of North America.  In the true Cats (Felis cants), the
tail is long, and the ears are not tufted. The Wild Cat formerly
existed in Britain, but is now extinct, though it still occurs in




s586            MANUAL OF ZOOLOGY.
Europe, especially in the Hartz and Carpathian Mountains.
It is a large and fierce animal, and appears to be quite a match
for any man not possessing firearms. It seems tolerably certain that the Wild Cat is not the original stock of the Domestic
Cat, the exact origin of which is uncertain.  It has been supposed, however, that the Domestic Cat is descended from a
small species (Fc/is man/icu/ala) which occurs in Nubia.
CHAPTER LXXX.
RODENTIA.
ORDER X. RODENTIA.  The tenth order of MVammalia is
that of the Rodcitzia, or Rodent Animals, often spoken of as
Glires, conmprising the Mice, Rats, Squirrels, Rabbits, Hares,
Beavers, &c.
The Rodentia are characterised by the possession of two
long curved incisor teeth in each jaw, separated by a wide interval from the molars. The lower jaw never has more than
two of these incisors, and the upper jaw very rarely; but sometimes there are four upper incisors.  There are no canine
teeth, and the molars and proemolars are few in number (rarely
more than four on each side of the jaw). The feet are usually
furnished with five toes each, all of which are armed with claws;
and the hallux, when present, does not differ in form from the
other digits. The testes pass periodically firom the abdomen
into a temporary scrotum, and the placenta is discoidal and
deciduate.
The most characteristic point about the Rodents is to be
found in the structure of the incisors, which are adapted for
continuous gnawing-hence the name. of Rodentia. The incisor teeth are commonly two in each jaw, and they grow from
persistent pulps, so that they continue to grow throughout the
life of the animal. They are large, long, and curved (fig. 228,
B), and are covered anteriorly by a plate of hard enamel. The
back part of each incisor is composed only of the comparatively
soft dentine, so that when the tooth is exposed to attrition, the
soft dentine behind wears away more rapidly than the hard
enamel in front. The result of this is that the crown of the
tooth acquires by use a chisel-like shape, bevelled away behind, and the enamel forms a persistent cutting edge (fig. 228).
The gnawing action of the incisors is assisted by the articu



RODENTIA.                        587
lation of the lower jaw, the condyle of which is placed longitudinally and not transversely, so that the jaw slides backwards
and forwards. The molars, consequently, have flat crowns, the
enamelled surfaces of which are always arranged in transverse
ridges, in opposition to the antero-posterior movement of the
jaw.  The intestine is very long, and. the c'ecum voluminous
Fig. 228.-A, Skull of the Beaver (after Owen). B, Diagram of the incisor tooth of a
Rodent, showing the chisel-shaped point; a Enamel; d Dentine.
(rarely wanting). The brain is nearly smooth, and without
convolutions. The orbits are not separated from the temporal
fossae, and the eyes are directed laterally. The Rodents are
almost all very small animals, and they are mostly very prolific. They subsist principally, if not entirely, upon vegetable
matters, especially the harder parts of plants, such as the bark
and.roots. Many of them possess the power of building elaborate nests, and most of them  hybernate.  They are very
generally distributed over the whole world, but no member of
the order has hitherto been detected in rocks older than the
Eocene Tertiary.
The Order Rodentia comprises a very large number of families, only the more important of which can be noticed here.
Eram. I. Ieporid&.- In this family are the Hares (Lejus
timidus) and Rabbits (Lepus cuniculus), distinguished amongst
the Rodenits by the possession of two small incisors in the
upper jaw, placed behind the central chisel-shaped incisors, so
that there are four upper incisors in all. The molars and praemolars aie rootless, and the dental formula is2-2    0-0        3-3    3-3
i-i  c;;    2-2m -          =28.
I —-I'  0 — 0    2 —-2    3-3
The clavicles are imperfect. The fore-legs, are furnished
with five toes, and are considerably shorter than the hind-legs,




588             MANUAL OF ZOOLOGY.
which have only four toes. The two orbits communicate by
an aperture in the septum.  Generally there is a short erect
tail.
The common Hare (Lepus timidus) is dispersed over the
whole of Europe, but is not met with in Sweden and Norway,
its place there being taken by the Mountain-hare (white in
winter), which occurs commonly in Scotland. As a rule, the
Hares occur in temperate regions, but some are found in
Africa, and one species (Lejiusgiacialis) is a native of the.Arctic
regions, whilst the common American Hare (L. Amnericanits)
extends from Canada to Mexico. The Rabbit is also a native
of temperate regions, but appears to thrive, to a more than
average extent, in Australia.
In the Calling Hares or Pikas (LZagorwnys), the legs do not
differ much in size, there is no visible tail, and the clavicles
are nearly complete. They are found in Russia, Siberia, and
North America.
EaMn. 2. Cavit&. —As examples of this family may be taken
the Capybara (Hydrochzwrus capybara) and the Guinea-pig
(Carvia apercea). In this family the body is covered with hair,
without spines, and the tail is rudimentary. The Capybara is
the largest of living Rodents, attaining a length of three or
four feet. It is a South American form, leading a semi-aquatic
life, to which end the feet are incompletely webbed. It is a
harmless stupid animal, and is not ufilike a small pig in appear:
ance. The Cavia ajperea is likewise a South American animal,
and is believed to be the parent stock of the Guinea-pigs so
often kept as domestic pets iri Europe. To the same group
as the Capybara belong the Agoitis (Dasyproctda) and the Pacas
(Cavlogenys), all of which have eight rootless molars in each
jaw, whilst the two former have four toes to the fore-feet, and
three toes on the hind-feet.  The various species of Agouti are
found in South America and the West Indies, whilst the Pacas
are exclusively South American. In this family, also, are usually placed the Chinchillas (ChZinchi/la) of Chili and Peru.
Earn. 3. Ifystricied. —In this family are the well-known Porcupines, distinguished from the other Rodents by the fact that
the body is covered with long spines or " quills," mixed with
bristly hairs. They have four molars on each side of each jaw,
and they possess imperfect clavicles.
The true Porcupines (Hystrix) have non-prehensile tails,
which are mostly furnished with long hollow spines, but sometimes with scales. and bristles. They are found in both the
Old and New World, but the American species differ in several
respects from those of the eastern hemisphere. They are mostly




RODENTIA.                      589
inhabitants of hot climates, with the exception of the common
Porcupine (H. cris/ala), which occurs in southern Europe and
in the north of Africa.  In the genus Athzerura of Asia and the
Indian Archipelago, the tail is terminated by a bundle of flattened horny strips. In the genus Erethizon, represented by the
Canada Porcupine (E. dorsatum) of North America, the quills
are short, and are half hidden in the hair.
The nearly-allied genus Cercolabes is South American, and it
is distinguished from the preceding by the possession of a long
prehensile tail. In fact, Cercolabes, like so many of the inhabitants of this wonderful continent, is adapted for an arboreal life, instead of being confined to the ground.
Elm.4. 4. Casoarid.-The best-known example of this family
is the Beaver (Castorfiber).  The distinctive peculiarities of
the family are the possession of distinct clavicles, the possession of five toes to each foot, and the fact that the hinder feet
are mostly webbed, adapting the animal to a -semi-aquatic life.
The Beaver is a large Rodent, attaining a length of from
two and a half to three feet. Naturally it is a social animal,:iving in societies, and this is still the case in America; but in
northern Europe and Asia, where the animal has been much
hunted, it leads a solitary life. When living in social communities the beavers build dams across the rivers, as well as habitations for themselves, by gnawing across the branches of trees
or shrubs, and weaving them together, the whole being afterwards plastered with mud. In this last operation the tail, which
is flattened and scaly, is employed very much'as a mason uses
his trowel. There is no doubt but that the Beaver shows extraordinary ingenuity in these-and similar operations; but there
can be equally little doubt as to the greatly-exaggerated stories
which have been set afloat in this connection. The Beaver is
hunted chiefly for the sake of the skin, but also for the substance known as castoreum. This is a fatty substance, secreted
by peculiar glands, and employed as a therapeutic agent.
There are two other members of the Castoridee which are
likewise largely captured for the sake of their skins.  One of
these is the Musquash (Fiber Zibethicus), which inhabits North
America, and the other is the Coypu (Afyopotamus coypus),
which inhabits burrows in the banks of rivers in Chili. In the
Musquash the hind feet are not completely webbed, and the
tail is moderate in size, and covered with short hairs and small
rounded scales. In the Coypu the hind feet are webbed, but
the tail is long, rounded, and furnished with scales and scattered hairs.
Fam. 5. Muridce.-The fifth family of Rodents is that of




590             MANUAL OF ZOOLOGY.
the MAurid&e, comprising the Rats, Mice, and Lemmings.  In
this family the tail is long, always thinly haired, sometimes
naked and scaly. The lower incisors are narrow and pointed,
and there are complete clavicles. The hind-feet are furnished
with five toes, the fore-feet with four, together with a rudimentary pollex.
The Rats (Mus raftus and Afus dccumanus), the.common
Mouse (Mus musculus), the Field-mouse (Mus sylvaticus), and
the Harvest-mouse (AMus messoriuzs), are all well-known examples
of this family, and are too familiar to require any description.
The three first are also common in North America.  Closely
allied to the true Rats are the Hamsters (Cricetus, fig. 229), and
the Voles (Arvicola)  the latter represented by many species'in
both Europe and America.
A less familiar example of this family is the Lemming (Myoies
Fig. 229.-Common Hamster (Cricetus vulgnaris).
linmmus). This curious little Rodent is found inhabiting the
mountainous regions of Norway and Sweden. It is chiefly remarkable for migrating at certain periods, generally towards the
approach of winter, in immense multitudes and in a straight
line, apparently in obedience.to. some blind mechanical impulse. In these journeys the Lemmings march in parallel
columns, and nothing will induce them to deviate from the
straight line of march.
Fam. 6. DiZjodide.-The sixth fafmily of the Rodents, which
is sufficiently important to need notice, is that of the Dipodidat
or Jerboas, mainly characterised by the disproportionate length
of the hind-limbs as compared with the fore-limbs. The tail
also is long and hairy, and there are complete clavicles. The
Jerboas live in troops, and owing to the great length of the
hind-legs, they can leap with great activity and to great dis



RODENTIA.                     591
tances. They are all of small size, and inhabit Russia, North
Africa, and North America. The best-known members of this
family are the common Jerboa (Dipus E/gypticus), which lives
in societies and constructs burrows; the Jumping Hare (Pedeles
Capensis) of South Africa, and the Jumping Mouse (Afierioncs
Hudsonicus) of North America. Here also may be placed the
Gerbilles (Gerbillus) of the Old World.
Earm. 7. Myoxidce.-The members of this family are commonly known as Dormice, and they are often included in the
following family of the Squirrels and Marmots. They only require to be mentioned, as they must nbt be confounded with
the true Mice (AMuride ) on the one hand, or the Shrew-mice
(Soricidce) on the other; the latter, indeed, belonging to another order (Insectivora). The common Dormouse (Mfyoxus
ave/lanarius) is a British species, and must be familiarly known
to almost everybody. No species of this family have yet been
described from the New World.
Eam. 8. Sciuride.-This is the last family of Rodents which
calls for any special mention, and it comprises the true Squirrels,
the Flying Squirrels, and the Marmots.
The true Squirrels (Sciurus) are. familiarly known in the
person of the common British species (Sciurus vulgaris), and
the equally common  Gray Squirrel (S. cinereus) of the
United States. Numerous species more or less closely allied
to these occur in other countries, and they are especially
abundant in North America.
In the genera Plerormys and Sciuropterus, or Flying Squirrels,
there is a peculiar modification by which the animal can take extended leaps from tree to tree. The skin, namely, extends in
the form of a broad membrane between the hind and fore legs,
and this acts as a kind of parachute, supporting the animal in
the air. There is, however, no power whatever of true flight,
and the structure is identically the same as what we have l:reviously seen in the Flying Phalangers (Petauszis), which take
the place of the Flying Squirrels on the Australian continent.
The Flying Squirrels are found in southern Asia, Polynesia, the
north-east of Europe, Siberia, and North America.
The Marmots (Arctolnys), unlike the true Squirrels, are terrestrial in their habits, and live in burrows. Various intermediate forms, however, are known, by which a transition is
effected between the typical Squirrels and the Marmots. Such,
for example, are the Ground Squirrels (T'namias) of Europe,
Asia, and North America. There are numerous species of this
family inhabiting various parts of Europe and northern Asia,
and generally distributed over.the whole of North America.




592              MANUAL OF ZOOLOGY.
Good examples. are the Alpine Marmot (A. Apinzus) of
Europe and the Prairie Dog (Cynonys Ludzovicianus) of North
America.
CHAPTER LXXXI.
CHEIROPTERA.
ORDER XI. CHEIROPTLfRA.' -This order is undoubtedly "the
most distinctly circumscribed and natural group" in the whole
class of the AManmmalia. In many respects, however, it would
be advantageous to regard the Cheirojtera as a sub-order of
the next order (namely, the Insectivora) specially modified to
lead an aerial life; just as the -Pilzntzgorada are regarded as a
mere section of the Carnivor-a specially modified to suit an
aquatic life.
Thle Chzeiroptera are essentially characterised by the fact 1hat
the anterior limbs are longer than the posterior, the digits of
the fore-limb, with the exception of the pollex, being enormously elongated (fig. 230).  These elongated fingers are
united by an expanded membrane' or " patagium," which is
also extended between the fore and hind limbs and the sides
of the body, and in many cases passes also between the hindlimbs and the tail. The patagium thus formed is naked,
or nearly so, on both sides, and it serves for flight. Of the
fingers of the hand, the pollex, and sometimes the next finger
as well, is unguiculate, or furnished with a claw; but the
other digits are destitute of nails.  In the hind-limbs all the
toes are unguiculate, and the hallux is not in any respect different from  the other digits.  Well-developed clavicles are
always present, and the radius has no power of rotation upon
the ulna. The mammary glands are two in number, and are
placed-upon the chest. There are teeth of three kinds, and
the canines are always well developed. The molars are tuberculate or grooved in the frugivorous forms, and cuspidate in
the insectivorous species. The ulna is sometimes quite rudimentary. The bones are not pneumatic. The testes are abdominal except during the breeding season. The stomach is
complex and the intestine long in the fruit-eating Bats; but
the reverse of this obtains amongst the Insectivorous forms.
* The Cheiro5tera were placed by Linneus in his order Primates, which
contained also the Lemurs, the Apes, and Man.




CHIEIROPTERA.                     593
The C/heiroptera are cosmopolitan in their distribution, and the
oldest known species is from the Eocene rocks.
The Bats are all crepuscular and nocturnal in their habits,
and are sometimes carnivorous, sometimes frugivorous. The
eyes are small, but the ears are very large, and their sense of
touch is most acute.  During the day they retire to caves or
crevices amongst the rocks, where they suspend themselves by
means of the short thumbs, which are provided with curved
claws. In their flight; though they can fly in the genuine and
proper sense of the term, and can turn with great ease, they
Fig. 230.-Skeleton of Fox-bat (Pleroqjus)-after Owen.
are by no means as rapid and as active as are the true birds.
The tail is sometimes short, sometimes moderately long, and
is usually included in a continuation of the leathery patagium,
which stretches between the hind-legs, and is termed the " inter-femoral membrane." The body is covered with hair, but
the patagium is usually hairless, or nearly so.  Most of the
Bats hybernate.
The Cheiroptera are conveniently divided into the two sections of the Insectivora and Frugivora, according as the diet
consists of insects or of fruits.




594              MANUAL OF ZOOLOGY.
SECTION A. INSECTIVORA. -In this section are the three
families of the VespertiiowideZ, Rhinolophidae, and Phyllosoamidx.
Fam. I. Yespertilionide. —In this family are the ordinary
Bats, distinguished by having a dentition very like that of the
order of the Insectivorous Mammals, the molar teeth being
furnished with small pointed eminences or cusps, adapted for
crushing insects.  The nose is not furnished with leaf-like
appendages, and the tail is usually elongated, and enclosed in
a large inter-femoral membrane. About fifteen species of this
family have beeh described as British, but of these only two
are at all common.  Of these two, the Pipistrelle ( Vcspertilio
pipis/relza) is the commonest species, occurring over the whole
of Britain.  The long-eared Bat (Plecotzusaurituzs) is also not
uncommon, and is distinguished by its greatly elongated ears,
Fig. 23r.-A, Head of Vampire-bat (AZectops aner). B, Head of Fox-bat
(Pteropaus, ersona/tus)-after Gray.
which are confluent above the forehead.  The largest British
species is the Noctule (Vespertilio noctzu/a), which measures as
much as fifteen inches in expanse of wing.
Fam. 2. Rhinolop/hide. -The second family of the Insec.
tivorous Bats is that of the R/hinolophid&e or Horse-shoe Bats,
which in niost respects are very similar to the Vesperti/ionfilte,
but are distinguished by the possession of a complex leaf-like
apparatus appended to the nose. Of this family, two British
species are known-the Greater and Lesser Horse-shoe Bats
(Rhinolojphus ferrum-equinum and R. hiipposideros).
Earm. 3. Phyllostomrid&e.-This is the only remaining family
of the Insectivorous Bats, and comprises the well-known Vampire-bats (fig. 23T, A), distinguished by having leaf-like nasal
appendages, and by the fact that the ears are of small size;
whereas in the preceding they are always very large (Rhinolo.




INSECTIVORA.                   595
pfius), and are often confluent above the forehead (Megaderma).
They are all of large size, and are natives of South America.
The Vampire-bat (Phyflostoma spectrumn) has an expanlse of wing
of two feet and a half, and lives chiefly upon insects. It also
has the habit of sucking the blood of sleeping animals, appearing sometimes to attack even man, though apparently never
doing any substantial or lasting injury.
SECTION B. FRUGIVORA.-In the fruit-eating section of the
Cheiroptera are only the Pteropidc  or the Fox-bats, so called
from the resemblance of the head to that of a fox (fig. 23I, B).
The head in these bats is long and pointed. The ears are
of moderate size, and the nose is destitute of any appendages.
Cutting incisors and canines are present in both jaws, and the
Fox-bats do not refuse to eat small birds or mammals. They
live, however, mostly upon fruits, and the molars are therefore
not cuspidate, but are furnished with blunt tubercular crowns.
The tail is very short, or is entirely absent. The Pteropidwc are
amongst the largest of the Bats, one species-the Pteropus
edulis, or Kalong-attaining a length of from four to five feet
from the tip of one wing to that of the other. The Pteropidce
are especially characteristic of the Pacific'Archipelago-Java,
Sumatra, Borneo, &c.-but they also occur in Asia, Australia,
and Africa. They do not occur, however, in either North or
South America.
CHAPTER LXXXII.
INSE C TI VORA.
ORDER XII. INSECTIVORA.-The twelfth order of Mammals
is that of the Ansectivora, comprising a number of small Mammals which are very similar to the Rodents in many respects,
but want the peculiar incisors of that order, and are likewise
always furnished with clavicles.
In the Insectivora, all the three kinds of teeth are usually
present, but the exact nature of the dentition varies considerably in different cases. The incisors and canines present little
special, but the molars are always serrated with numerous
small pointed eminences or cusps, adapted for crushing insects.
With one exception, clavicles are always present in a complete
form. All the feet are usually furnished with five toes; all the
toes are furnished with claws; and the animal walks on the




596              MANUAL OF ZOOLOGY.
soles of the feet, or is plantigrade. The testes pass periodically
from the abdomen into a temporary scrotum; and the placenta
is deciduate and discoidal.  They are mostly nocturnal and
subterranean, and generally hybernate. They are all of small
size, and are found everywhere, except in the continents of
South America and Australia, where their place is filled by
Marsupials.
The three leading families of the
Jnsectivora are the Tatfidev or Moles,
the Soricid2e or Shrew mice, and the
Erinaceidce or Hedgehogs.
Famn. i. Ta. pide.-T'he body in
this family is covered with hair; the
feet are formed for digging and burFig. 232. —Insectivora.  Skull of rowing, and the toes are furnished.the common Hedgehog (EL-lznaces E     dLropre,s).   with strong curved claws.  There
are no external ears; and the eyes
in the adult are rudimentary, and more or less completely
useless as organs of vision. There is a peculiar bone for the
support of the muzzle. The clavicles are strong, the arm very
short, the hand wide, and the palm always turned outwards
and backwards. The fur is short and velvety, and the tail
very short or wanting, in most cases.
Fig. 233.-European Mole (Ta1Iao Eurojian).
The common Mole (Talpa Eurojcea, fig. 233) is the only
British species of the family, and a representative form (Condylura) occurs in North America. One of the most remarkable
of the Talpidc is the Golden Mole (Chrysochloris aureus) of
Africa. In form and habits this species resembles the common Mole, but the hairs of the fur have the property of dispersing the rays of light, and thus of giving rise to beautiful




GALEOPITrHECIDX,                   g97
netallic colours, such as are produced by the "setx'. of the
Sea-mice (Aphzrodiie) amongst the Annelides,  The star-nosed
Moles (Co/l/dy//ra) are North American, and are distinguished
by a fringe of elongated membranous caruncles surrounding
the nostrils. The tail is moderately long.
FEarn. 2. Soricidide.-The Soricidwe or Shrew-mice are distinguished by having the body c(vvered with hair, and the feet not
adapted for digging; whilst there are external ears, and the
eyes are well developed.  Of all the Izisectivora, no division is
more abundant or more widely distributed than that of the
Shrew-mice.  In general form and appearance the Shrews very
closely resemble the true Mice (Jlla-ridza) and the Dormice
(Mlyoxidae), but they are in reality widely different, and must
not be confounded with them.  The common Shrew (o'rcx
a-ralzeus) and the Water-Shrew (Sorex fodienzs) are both wellknown species of this family.  The smallest known Mammal
is one of the Shrews (Sorex Etruscus), which is not more than
two and a half inches in length, counting in the tail.  Besides
the true Shrews, the Shrew-moles (Scalops) and the Elephant
Shrews (il/acroscedides) are included in this family, the former
being North American, whilst the latter are African.
EalZm. 3. Erinzaceid~T.-The last family of the iJzsect/iora is
that of the Hedgehogs, characterised by the fact that the
upper part of the body is covered with prickly spines, the feet
are not adapted for digging, and they have mostly the power
of rolling themselves into a ball at the approach of danger.
The common Hedgehog (Erinlacezs Eza-opceizs) is in every way
a typical example of this family, but is too well known to require any description.  Other species of Erinaceazs have' been
recorded from Africa and India.
The "' Tenrecs" (Cetze/es) are natives of Madagascar, and
may be regarded as Hedgehogs without the power of rolling
themselves up into a ball. They have no tail, and have the
skin beset with spines or spine-like bristles.
The " Banxrings" (Tzapaia) are arboreal in their habits, and
are confined to the Indian Archipelago. They must be regarded
as the type of a distinct family of /insectivora. They have a
long attenuated snout, with large eyes, a long body, and a close
fur intermixed with soft hairs. The feet are plantigrade, fivetoed, with naked soles and sickle-shaped claws. The tail is
longer than the body, compressed a:nd fringed at the sides.
GALEOPITHECIDE.
Before passing on to the Quadrz//ia/la, mention must be
made here of a very singular animal which forms a kind of




598             MANUAL OF ZOOLOGY.
connecting link between the. orders of the Insecfivora and
Quadrumana, having been sometimes placed in the one and
sometimes in the other, or having been regarded as the type
of a separate order. The order includes only the single genus
Galeopithecus, comprising the so-called " Flying Lemurs."  All
the Galeop5itheci inhabit the Indian Archipelago, but the best
known is the Galeopithecus volans of Java, Sumatra, and
Borneo. The most characteristic point in this singular animal
is the presence of a flying membrane, presenting some superficial resemblance to the patagium of the Bats, but in reality
very much the same as the integumentary expansions of the
Flying Squirrels and Flying Phalangers.  This membrane in
the Galeopit/lecus extends as a broad expansion from the nape
of the neck to the arms, from the arms to the hind-legs, and
from the hind-legs to the tail, forming an inter-femoral membrane.'The fingers are not- elongated, and do not support a
patagium, as in the Bats, so that the animals have no power of
true flight, and can simply take extended leaps from tree to
tree. The feet are furnished with five toes each, united by a
membrane, but neither the hallux nor the pollex are opposable
to the other digits. The dentition is complicated, and consists of incisors and molars, and, according to Owen, canines
also, the dental formula being2-2   I-I        2-2    3-3
I2 —-2;; C-  on *-i;  m -- n    34.
3-3   I —I       2 —2    3-3
The six lower incisors are split into narrow strips, like the teeth
of a comb. The Galeopith/eci live chiefly upon small birds and
insects, but also partially upon fruits.  They are nocturnal
animals, arboreal in their habits, and they sleep head-downwards, suspended by their prehensile tails.
CHAPTER LXXXIII.
QU A DR UMA NA.
ORDER XIII. QUADRUMANA.-The thirteenth order of Mammals is that of the Quarwunviana, comprising the Apes, Monkeys, Baboons, Lemurs, &c., characterised by the following
points:The hallux (innermost toe of the hind-limb) is separated
from the other toes, and is opposable to them, so that the




QUADRUMANA.                      599
hind-feet become prehensile hands. The pollex (innermost
toe of the fore-limbs) may be wanting, but when present, it
also is usually opposable to the other digits, so that the animal
becomes truly quadrumanous, or four-handed.
2-2
The incisor teeth generally are 22, and the molars 3-3
2 —2                3-3'
with broad and tuberculate crowns. Perfect clavicles are present. The teats are two in number, and are pectoral in position, and the placenta is discoidal and deciduate.
Fig. 234.-Green Monkey or Guenon (Cercocebus sabevus) —after Cuvier.
The Quadrumana are divided. by Owen into three very
natural groups, separated from one another by their anatomical
characters and by their geographical distribution as follows:Section A. Strepsirhina.-The members of this section are
characterised by the nostrils being curved or twisted, whilst
the second digit of the hind-limb has a claw. This section
includes the true Lemurs and a number of allied forms. It is
chiefly referable to Madagascar as its geographical centre; but
it spreads westwards into Africa, and eastwards into the Indian
Archipelago.
Section B. Platyrhina.-This section includes those Quadrumana in which the nostrils are placed far apart; the thumbs




600             MANUAL OF ZOOLOGY.
of the fore-feet are either wanting, or, if present, are not opposable to the other digits; and the tail is generally prehensile.
The Platyrhine Monkeys are exclusively confined to South
America.
Setizon C. Caltarhina.- In this section the nostrils are oblique, and placed close together. The thumb of the fore-limb
(pollex), with one exception, is present, and is always opposable to the other digits. The Catarhine Monkeys are restricted
entirely to the Old World, and, with the single exception of a
Monkey which inhabits the rock of Gibraltar, they are exclusively confined to Africa and Asia. It is in the Catarhine section of the Quadrumana that we have the highest group of
the Monkeys-that, namely, of. the Anthropoid or Tail-less
Apes.
STREPSIRHINA.
This section of the Quadrumana, as before said, is characterised by the possession of twisted or curved nostrils, placed
at the end of the snout. The incisor teeth are generally much
modified, and are in number  3  as a rule; the lower
3-3                    3-3
incisors are produced and slanting; the prremolars are 
2-2
or 2-2  and the molars are tuberculate.  The second digit
of the hind-limb has a claw, and both fore and hind feet have
five toes each, all the thumbs being generally opposable. In
the true Lemurs, all the digits, except the second toe of the
hind-feet, are furnished with nails.
This section is often called that of the Prosimia, and it includes several families, of which the Aye-Ayes, Loris, and true
Lemurs are the most important. - In many works the Galeopithecus is also placed in this section.
The family of the Aye-Ayes (Cheiromyde) includes only a
single animal, the Cheiromys Madinagascariensis.  In appearance
the Aye-Aye is not very unlike a large Squirrel, having a hairy
body and a long bushy tail. There are no canines, and the
molars are separated by a wide interval from the incisors. The
incisors are ploughshare-shaped, and grow from  permanent
pulps, as in the Rodents.  The fore-feet have five toes, armed
with strong claws, but the pollex is scarcely opposable to the
other digits.  The middle-finger is about as long as the ringfinger, but only about half as thick, its last two joints being
hairless. The hind-feet have also five toes, of which the hallux
is opposable, and the second digit is furnished with a long




QUADRUMANA.                     6oi
claw. As far as is yet known, the Cheiromys is entirely confined to Madagascar.
In the JVycticebidc are the Loris and the Slow Lemurs, in
which there is no tail, or but a rudimentary one; the ears are
short and rounded, and the eyes are large, and are placed close
together. The species of this family are all of small size, and
are exclusively confined to the eastern portion of the Old
World, occurring in Java, Ceylon, the southern parts of Asia,
and other localities in the same geographical area. They are
nocturnal in their habits, living mostly on trees, and feeding
upon insects; and from the slowness with which some of them
progress, they are sometimes spoken of as "Slow Lemurs."
The best-known species are the Slender Loris (L. graci/is) of
Ceylon, and the Nycticebus tardigrad.us of the East Indies.
The largest and most important of the families of the Strepsir-lina is that of the Lemuridce or true Lemurs. In this family
the muzzle is elongated, the feet are all furnished with opposable thumbs, and the nails on all the toes are flat, with the
exception of the second toe of the hind-foot, in which there is
a long and pointed claw. The body is covered with a soft
fur, and the tail is usually of considerable length, and is
covered with hair. They are easily domesticated; and though
capable of biting pretty.severely, their disposition is gentle and
docile. They are mostly about the size of cats, and not unlike
them in appearance, being often termed " Madagascar cats"
by sailors. They are found almost exclusively in the great
forests of Madagascar, moving about amongst the trees with
great activity, by means of their prehensile tails.. They appear
to fill in Madagascar the place occupied by the higher Quadrumana upon the adjoining continent of Africa. The largest
species is the Indri, which has very long hind-legs, and stands
as much as three feet in height.
PLATYRHINA.
The section of the Platyrhine Monkeys is exclusively confined to South America, and one of its leading characters is to
be found in the almost universal possession of a prehensile
tail; this being an adaptive character by which they are
suited to the arboreal life which so many of the South American Mammals are forced to lead. There are neither cheekpouches nor natal callosities, and there is an additional prwemolar, and sometimes a molar less than in man and the Old World
Monkeys. The nostrils are simple, wide apart, and placed
3-3
nearly at the extremity of the snout.  The prxmolars are ---




602             MANUAL OF ZOOLOGY.
in number, and have blunt tubercles. The thumbs of the forehands are either wanting altogether, or, if present, are not
opposable, though versatile.
The Platyrhine Monkeys are divided into the two sections
of the Hapalid&e and Cebide.
Eram. I.  apalide. —In this family the number of teeth is
the same as in the Old World Monkeys and in Man, but
there is an additional prmemolar on each side of each jaw, and
a molar less. According to Owen, the dental formula of the
Marmoset is2-2    I-I       3-3   2-2
z-; c; p         —'Z'; n - 32.
The molars, however, are tuberculate, and though the number of teeth is the same as in the Catarhine Monkeys, in their
other characters the Marmosets are genuine Platyrhines. The
hind-feet have an opposable hallux with a flat nail, but all the
other toes are unguiculate, and the pollex is hardly opposable.
The tail is long, but is not prehensile.
The Hapalidce are all small monkeys, mostly about as big
as Squirrels, and they are exclusively South American, occurring especially in Brazil.  The best-known species is the
common Marmoset (Hapale5enicillata), but several species are
domesticated and kept as pets.
Eaam 2. Cebidea.-In this family are all the typical Platyrhine
Monkeys, in which the dentition differs from that of the R-tpalid&a in having an additional molar, so that the molars are the
same as in the Catarhina and in Man, but the prmemolars are
more numerous. The dental formula is2 —-2   I-I     3-3   3-3
i 2 —2' c      -j; in; m - = 36.
There are neither cheek-pouches nor " callosities;" and the
face is usually more or less naked, though sometimes whiskered. The tail is long, and is mostly prehensile; though in
rare instances it is non-prehensile, and has its extremity clothed
with hairs. The thumb of the fore-hand may be wanting, and,
if present, is not opposable. All the fingers are furnished with
flat nails. Their qiet is miscellaneous, consisting partly of insects and partly of fruit.
The Cebide are exclusively confined to the warmer parts of
South America, in the vast forests of which they are met with
in large troops, climbing amongst the trees.  The Spider
Monkeys (Ateies), the Howling Monkeys (Mfyceles), the Capuchin Monkey (Cebus), and the Squirrel Monkey (Ca/llitirix),
may serve as typical examples of this section of the Quadru



QUADRUMANA.                       603
manza.  In Ateles the tail is long, slender, and powerfully prehensile; and the limbs are very long and slender. The pollex
is absent, or is quite rudimentary.  In Afycetes there is a bony
drum which is formed by a convexity of the os hyoides and
communicates with the larynx. The voice is thus rendered
extraordinarily resonant. The pollex is not opposable, but is
placed on a line with the other fingers.
CATARHINA.
The third and highest section of the Quadrumana is that of
the Catarhzina or Old World Monkeys. In this section the
nostrils are oblique, and are placed close together, and the
septum  narium  is narrow.  The thumbs of all the feet are
opposable, so that the animal is strictly quadrumanous. In
Colobus alone the anterior thumbs (pollex) are wanting. The
dental formula is the same as in man, viz.:
2-2    I —I       2-2    3-3
2-2; c 1; 5inm 2-2'  3 32.
The incisors, however, are projecting and prominent, and
the canines-especially in the males-are large and pointed.
Moreover, the teeth form an uneven series, interrupted by a
diastema or interval.  The tail is never prehensile, and is
sometimes absent. Cheek-pouchesc are often present, and the
skin covering the tubera ischii is almost always callous and
destitute of hair, constituting the so-called " natal callosities."
With the single exception of a Monkey which inhabits the
Rock of Gibraltar, all the Catarhina are natives of Africa
and Asia.
There are three well-marked groups or tribes of the Catarhine Monkeys.  In the first of these the tail is long, and
there are both cheek-pouches and natal callosities. In this
tribe is the genus Sezmnopithecus, all the species of which are
natives of Asia and its islands. One of the best-known species
is the Sacred Monkey of the Hindoos (Semnopitliccus eute/lus)..Closely allied to the Sezmnopitheci is the genus Colobus, in
which alone, of all the Catarhine Monkeys, the pollex is either
altogether absent or totally rudimentary. Closely allied to
Semnozit/hecus, also, is the Proboscis Monkey or Kahau (Piresbtizs
nasalis), distinguished by its elongated proboscidiform nose,
short pollex, and long tail. Here also come the little Guenons
(Cercocebus and Cercopit/zecus, fig. 234).  Also referable to this
* The cheek-pouches are sacs or cavities in the cheeks, which open into
the mouth, and serve to hold any superfluous food.
27




604             MANUAL OF ZOOLOGY.
division is the genus Yfacacus or Inuus (comprising the Macaques), which includes most of the Monkeys which are ordinarily brought to this country. It is a Macaque which occurs
at the Rock of Gibraltar, and is the only wild Monkey which
is found in Europe at the present day. Most of the Macaques
are Asiatic, and a good example is the Wanderoo (M. Silenus)
of India.
The second tribe of the Catarhine Monkeys is that of the
Baboons (Cynocephalus and Pajio). In these forms the tail is
mostly short, and is often quite rudimentary. The head is large,
and the muzzle is greatly prolonged, having the nostrils at its
extremity. The facial angle is about 30~, and the whole head
has much the aspect of that of a large dog. The natal callosities are generally large and conspicuous, and usually of some
bright colour. The Baboons are large strong animals, extremely unattractive in outward appearance, and of great
ferocity. More than any other of the Monkeys, they employ
the fore-limbs in terrestrial progression, running upon all-fours
with the greatest ease. They are mainly inhabitants of Africa,
and one of them, the Mandrill (Cynocefhalus Aainon), attains
very nearly the height of a man. The best-known species is
the Chacma (Cynocephalus porcarius), the Derrias (C. Hamzadryas), the Common Baboon (C. papio), and the Mandrill. The
Derrias is found in Arabia and Abyssinia, and occurs both
embalmed and sculptured upon ancient monuments in Egypt
and Nubia. The Mandrill is rendered probably without exception the most disgustingly hideous of living beings by the
possession of large blood-red natal callosities and of enormous
cheek-protuberances striped with brilliant colours in alternate
ribs.
The third family of the Catarhine Monkeys is that of the
Anthropomorphous or Anthropoid Apes, so called from their
making a nearer approach in anatomical structure to man than
is the case with any other Mammal. The members of this
family are Apes in which there is no tail, and cheek-pouches
are absent, whilst in some cases there are also no natal callosities. The hind-limbs are short-shorter than the fore-limbs
— and the animal can progress in an erect or semi-erect
position. At the same time, the thumbs of the hind-feet
(hallux) are opposable to the other digits, so that the hindfeet are prehensile hands. The spine shows a single curve,
and articulates with the back part of the skull. The canine
teeth of the males are long, strong, and pointed, but this is
not the case with the females. The structure, therefore, of
the canine teeth is to be regarded in the light of a sexual




QUADRUMANA.                     605
peculiarity, and not as having any connection with the nature
of the food.
In this tribe are the Gibbons (Hylobates), the Orang-outang
(Simnia satyrus), the Chimpanzee, and the Gorilla.
The Gibbons form the genus Hylobates, and they belong to
southern Asia and the Indian Archipelago. The anterior limbs
are extremely long, and the hands nearly or quite reach the
ground when the animal stands in an erect posture. There is
no tail, but there are natal callosities. The body is covered
with a thick fur. One of the best known of the Gibbons is
the Siamang (Hylobates syndactylus), which has been sometimes
regarded as making a nearer approach to man than any other
of the Monkeys.  It is a native of Sumatra. It is the largest
of the Gibbons, and derives its specific name from the fact
that the index and middle toes of the hind-foot are united to
one another by skin as far as the nail joint. Another wellknown species is the common Gibbon (hI. lar).
In the Orang or "Mias" (Simia satyrus) there are neither
cheek-pouches nor natal callosities, and the hips are covered
with hair. As in the Gibbons, the arms are excessively long,
reaching considerably below the knee when the animal stands
in an erect posture. The hind-legs are very short, and there
is no tail. When full grown the Orang stands about four feet
high. It never progresses with the help of a stick, or walks
erect at all, except along the branches of trees, supporting itself
by a higher branch, or when attacked. When young, the head
-f-~ ~" /
Fig. 235.-A, Skull of the Orang-outang. B, Skull of an adult European.
of the Orang is not very different from that of an average
Elropean child; but, as the animal grows, the facial bones




606            MANUAL OF ZOOLOGY.
become gradually produced, whilst the cranium remains in a
tolerably stationary condition; great bony ridges are developed
for the attachment of the muscles of the jaws and face; the
incisors project; and ultimately the muzzle becomes as pronounced and well-marked a feature as in the typical CarniVzaor
(fig. 235, A). The Orangs are inhabitants of Sumatra and
Borneo.
The genus Troglodytes contains the Chimpanzee (T. niger)
and the Gorilla (T. Gorilla). The Chimpanzee is a native of
Western Africa, and has the arms much shorter, proportionately,
than in the Gibbons and Orangs; still they are much longer
than the hind-limbs, and they reach beneath the knee when
the animal stands erect. The ears in the Chimpanzee are
large, and the body is covered with dark-brown hair. The
animal can stand erect, but the natural mode of progression is
on all-fours. The hands are naked to the wrist, and the face
is also naked, and is much wrinkled. The Chimpanzee lives in
society in wooded districts, constructs huts, and can defend
itself against even the Elephant.
The Gorilla is in most respects the same as the Chimpanzee, but is much larger, attaining a height of fully five feet.
The hind-limbs are short, and the ears small. It is an enormously strong and ferocious animal, and is found in Lower
Guinea and in the interior of equatorial Africa. It possesses
a laryngeal sac, has a most appalling voice, and is polygamous.
The Gorilla is now generally regarded as the most human of
the Anthropoid Apes.
CHAPTER LXXXIV.
BIEA NVA.
ORDER XIV. BIMANA.-This, the last remaining order of the
Mamrnmalia, comprises Man (imino) alone, and it will therefore
require but little notice here, the peculiarities of Man's mental
and physical structure properly belonging to other branches of
science.
Zoologically, Man is distinguished from all other Mammals
by his habitually erect posture and bipedal progression. The
lower limbs are exclusively devoted to progression and to supporting the weight of the body. The anterior limbs are shorter
than the posterior, and have nothing whatever to do with pro



DISTRIBUTION OF MAMMALIA IN TIME.   607
gression. The thumb is opposable, and the hands are prehensile, the fingers being provided with nails. The toes of the
hind-limb are also furnished with nails, but the hallux is not
opposable to the other digits, and the feet are therefore useless
as organs of prehension. The foot is broad and plantigrade,
and the whole sole is applied to the ground in walking.
The dentition consists of thirty-two teeth, and these form a
nearly even and uninterrupted series, without any interval or
diastema. The dental formula is-. 2-2   I-I    2-2    3-3
2 —2'  I-I'; ~ 2 —2;  m 3 — =32
The brain is more largely developed and more abundantly
furnished with large and deep convolutions than is the case
with any other Mammal. The mammm are pectoral, and the
placenta is discoidal and deciduate.
Man is the only terrestrial Mammal in which the body is
not provided with a covering of hair.
The zoological or anatomical distinctions between Man and
the other Mammals are thus seen to be of no very striking
nature, and certainly of themselves would not entitle us to
consider Man as forming more than a distinct order. When,
however, we take into account the vast and illimitable psychical
differences, both intellectual and moral — differences which
must entail corresponding structural distinctions — between
Man and the highest Quzadrumana, it becomes a question
whether the group Bimana should not have the value of a
distinct sub-kingdom; whilst there can be little hesitation in
giving Man, at any rate, a class to himself. At any rate, man's
psychical peculiarities are as much an integral portion, or
more, of his totality, as are. his physical characters, and, as
Dr Pritchard says,-" The sentiments, feelings, sympathies,
internal consciousness, and mind, and the habitudes of mind
and action thence resulting, are the real and essential characteristics of humanity."
CHAPTER LXXXV.
DISTRIBUTION  OF MAMMALIA   IN  TIME.
As a matter of course, the remains of Mammals are scanty,
and occupy but a small space in the geological record, since
the greater number of the _Afaimmalia are terrestrial, and the




608             MANUAL OF ZOOLOGY.
greater number of the stratified fossiliferous deposits are marine.
The Mammals, too, are the most highly organised of the entire
sub-kingdom of the Vertebrata; and therefore, in obedience to
the well-known law of succession, they ought to make their
appearance upon the globe at a later period than any of the
lower classes of the Vertebrata. Such, in point of fact, is to a
great extent the case; and if the geological record were perfect,
the law would doubtless be carried out to its full extent.
It is in the upper portion of the Triassic Rocks-that is to
say, not long after the commencement of the Mesozoic or
Secondary epoch — that Mammals for the first time make their
appearance; four species being now known in a zone of rocks
which are placed at the summit of the Trias, just where this
formation begins to pass into the Lias. The earliest of these
-the oldest known of all the Mammals-appears at the upper
part of the Upper Trias (Keuper) and also at its very summit
(Penarth beds), and has been described under the name of
Microlestes antiquus. The nearest ally of Ai~icrolestes amongst
existing Mammals would seem to be the Marsupial and insectivorous Myrmecobius, or Banded Ant-eater of Australia. As
only the teeth, however, of Microles/es have hitherto been discovered, it is impossible to decide positively whether this
primeval Mammal was Marsupial or Placental.
The next traces of Mammals occur in the Stonesfield Slate
(Lower Oolites), and here four species, all of small size, are
known to occur.  Most of these- were Marsupial, but it is
possible that one was placental. They form the genera A4nphiiestes, Amphitherium, Phzascolotheriurm, and Stereognathuzs. After
the Stonesfield Slate another interval succeeds, in which no
Mammalian remains have hitherto been found; but in the freshwater formation of the Middle Purbeck-at the top, namely, of
the Oolitic series-as many as fourteen small Mammals have
been discovered.  These constitute the genera Plagiaulax,
Triconodon, and Galestes. Another gap then follows, no Mammal having hitherto been discovered in any portion of the
Cretaceous series (with doubtful exceptions).
Leaving the Mesozoic and entering upon the Kainozoic
period, remains of Mammals are never absent from any of the
geological formations. From the base of the Eocene Rocks
up to the present day remains of Mammals invariably occur,
constantly increasing in number and importance, till we arrive
at the fauna now in existence upon the globe.
The number of known fossil Mammals is so great, and thei
exhibit so many peculiarities and divergences from existing
forms, that it will be impossible here to do more than simply




DISTRIBUTION OF MAMMALIA IN TIME.   609
point out the leading facts known as to the distribution of each
order of Mammals in past time.
Order L. Monotremata.-The Monotremes are not known to
be represented at all in past time; and this need not excite
any surprise, seeing that the order is represented at the present
day by no more than two genera, both confined to a single
geographical region. Upon theoretical grounds, however, it
may be expected that we shall ultimately discover that the
antiquity of the order AMonotremata is extremely high.
Order IS. Mafrsuzpialia.-This is probably the oldest of the
Mammalian orders; but owing to the detached and fragmentary condition of almost all Mammalian remains-consisting
mostly of the ramus of the lower jaw, or of separate teeth-it
is not possible to state this with absolute certainty.  The
Microlestes of the Trias, the oldest, or nearly the oldest, of the
Mammals, was probably a Marsupial; but the evidence upon
this point is not conclusive. In the Triassic rocks of America,
also, perhaps at a lower horizon than that at which Microlestes
occurs in Europe, has been found the jaw of a small Mammal,
which is probably Marsupial, and has been named Dromatherium (fig. 236).
Fig. 236.-Lower jaw of Dromatherium sylvestre (after Emmons). From rock.s,
supposed to be of Triassic age, in North Carolina.
In the next mammaliferous horizon, however-namely, that
of the Stonesfield Slate in the Lower Oolites-there is no doubt
but that some of the Mammalian remains, if not all, belong to
small Marsupials (fig. 237). From this horizon the two genera
Phiascolotherium and Amphitherium, are almost certainly referable to the Maarsupialia; the latter seeming to be most nearly
related to the living Myrrmecobius, whilst the former finds its
nearest living ally in the Opossums of America. The Slereognathus of the Stonesfield Slate is in a doubtful position. It
may have been Marsupial; but, upon the whole, Professor Owen
is inclined to believe that it was placental, hoofed, and herbivorous.
With the occurrence of small Marsupials in England within
the Oolitic period, it is interesting to notice how the fauna ot
that time approached in other respects to that now inhabiting
Australia. At the present day, Australia is almost wholly




6io              MANUAL OF ZOOLOGY.
tenanted by Marsupials; upon its land-surface flourish Aram.
carice and Cycadaceous plants, and in its seas swims the Port
Jackson Shark (Cestracion Philippi); whilst the Molluscan
genus Trigonia is nowadays exclusively confined to the Australian coasts. In England, at the time of the deposition of the
Y         2
f-.,..
Fig. 237.-Oolitic Mammals, natural size. z. Lower jaw and teeth of Phascolotheriam;
2. of Triconzofon; 3. of A oz/tithzeeriaum; 4. of Plagiaulax.
Stonesfield Slate, we must have had a fauna and flora very
closely resembling what we now see in Australia. The small
Marsupials, Almp/iti/erium and Phascolot//erium, prove that the
Mammals were the same in order; cones of Araucarian pines,
with tree-ferns and fronds of Cycads, occur throughout the
Oolitic series; spine-bearing fishes, like the Port Jackson
Shark, are abundantly represented by genera such as Acrodus
and Stroophodus; and, lastly, the genus  frirgonia, now exclusively Australian, is represented in the Stonesfield Slate by
species which differ little from those now existing.
In the middle Purbeck beds (Upper Oolite), where fourteen
species of Mammals are known to exist, it is probable that all
were Marsupial.  All the Purbeck Mammalia were of small
size, the largest being no bigger than a pole-cat or hedgehog.
They form the genera Pla-iaulcax, Tricozodton, and Galestes, of
which Plagiazlax is believed to be most nearly allied to the
living Kangaroo-rat (Hypsiprymnus) of Australia.
In the Tertiary series of rocks Marsupials are of rare occurrence; but an Opossum, closely allied to the existing American
forms, has been discovered in the Eocene rocks of France
(Gypseous series of Montmartre), and has been named the
Didelphys gypsorum.
The next occurrence of Marsupials is in the later Tertiary
(Pliocene) and in the Post-tertiary epoch; and here they are
represented by some very remarkable forms. The remains in
question have been found in the bone-caves of Australia-the
country in which Marsupials now abound above every other




DISTRIBUTION OF MAMMALIA IN TIME.   611
part of the globe; and they show that Australia, at no distant
geological period, possessed a Marsupial fauna, much resembling -that which it has at present, but comparatively of a
much more gigantic size. In the remains from the Australian
bone-caves almost all the most characteristic living Marsupials
of Australia and Van Diemen's Land are represented; but the
extinct forms are usually of much greater size. We have
W\ombats, Phalangers, Flying Phalangers, and Kangaroos, with
carnivorous- Marsupials resembling the recent Thylacinus and
Dasyuruls.  The two most remarkable of these extinct forms
are Djiprolodonl and ThylacoZeo. In most essential respects
Diprotodon resembled the Kangaroos, the dentition, especially,
showing many points of affinity.  The hind-limbs, however, of
Diprotodon were by no means
so disproportionately long as in
the Kangaroos. In size Diprotodon must have many times            - -;a
exceeded the largest of the living Kangaroos, since the skull
measures three feet in length
(fig. 238). Thylacoleo was a car- 
nivorous and predacious Marslpial, equally gigantic when Fig. 238.-Skull of Di/rootodon Ats/rnais.
compared  with living forms.
2Thylacoleo, in fact, must have been, on a moderate estimate,
at least as large as a Lion; the largest living carnivorous
Marsupial being no larger than a shepherd's dog. The fleshtooth or carnassial molar of TShylacoleo measures two inches
and a quarter across, or very nearly double the measurement
of the same tooth in the largest existing Lion.
Order III. Edzent/at.-The Edentates, like the Marsupials,
are singularly circumscribed at the present day. No member
of the order is at the present day indigenous in Europe.
Tropical Asia and Africa have the Scaly Ant-eaters or Pangolins:
and in Africa occurs the Edentate genus Orycteropus. South
America, however, is the metropolis of the  dent/a/a, the order
being there represented by the Sloths, the Armadillos, and.the
true Ant-eaters. It is also in South America that by far the
greater number of extinct Edentates have been found; and, as
in the case of the Australian Marsupials, the fossil forms are
gigantic in size compared with their living representatives.
The Sloths (Bradypodide) of the present day were represented i, Post-tertiary times by a group of gigantic forms
referable to the genera Afylodon, Aifealoznyx, and ffegat/heriuln.
Of these, Myodon  attained a length of eleven feet, and Mega



612              MANUAL OF ZOOLOGY.
therium (fig. 239) was eighteen feet in length, with bones as
massive, or more so, than the Elephant.
Fig. 239. —lIeganteriuzm. From the Upper Tertiaries of South America (Pleistocene).
In the same way the little banded Armadillos of South
America were formerly represented by gigantic species, constituting the genus Gly/ptodoni. The Glyptodons (fig. 240) differed
from the living Armadillos in having no bands in their armour,
so that they must have been unable to roll themselves up. It
is rare at the present day to meet with any Armadillo over
two or three feet in length; but the length of the Glyptodon
clavipes, from the tip of the snout to the end of the tail, was
more than nine feet.
Fig. 240. —GlIltodon clavZies. Pleistocene deposits of South Americ.
All these gigantic South American Edentates occur in Posttertiary deposits.  Older, however, than any of these is the
Afacrotherium.  This is a gigantic Edentate, intermediate in
some respects between  the Pangolins and Orycteropus, and
found in certain lacustrine deposits of France, of Miocene age.
Order IV. Sirenia. —This order contains only the living
Manatees and Dugongs, and is of little geological importance.
The Haitiherium, however, of the Eocene, Miocene, and Plio



DISTRIBUTION OF MAMMALIA IN TIME.   613
cene rocks, is a large form, intermediate between the African
Manatee and the Dugong.
Order V  Cetacea.-The Celacea, also, are of little geological
importance. Remains of Dolphins (Ziphzius) and of Whales
(Balzenodon) are found in Miocene deposits; and numerous
ear-bones of Whales occur in the Red Crag of Suffolk (Pliocene). The most remarkable, however, of the extinct Cetacea,
is the Zeufglodon of the American and Maltese Miocene deposits. This was an enormous toothed Whale, about seventy
feet in length; but, unlike any of existing Cetaceans, it had
the posterior teeth implanted by two distinct fangs or roots.
By Owen, Zeugflodon is regarded as the type of a distinct family,
intermediate between the Cetacea and the Sirenia.  In Saurocetes, a large Cetacean from the Tertiary beds of Buenos Ayres,
there were double-fanged teeth with conoid crowns. It was
much smaller than Zeuglodon.
Order VI. Ungulata. —The hoofed Mammals are represented in past time by so many extinct forms that it will be
wholly impossible here to do more than merely allude to some
of the more important genera.
The earliest-known Ungulates occur in the Eocene rocks,
where the order is represented by very numerous and interesting forms, the more important of which are Piolop/hus, Pa/!eothierium, and Anaopiotherizum.
Of the section of the Ungulates comprising the living Horse,
Zebra, and Ass (Solidungula), the earliest fossil example is the
Anc/zitzherium of the Lower Miocene, and this was succeeded
by the Hipparion of the Miocene rocks. This genus differed
from the existing Equidce in the presence of two small toes
with hoofs, one on each side of the single functional toe,
which alone remains in living horses. In the Pliocene period
appear, for the first time, remains of horses which, like the
present form, possessed only a single toe encased in a single
hoof. It is ihteresting to observe that one of the Pliocene
horses (Efquus curvidens) occurs in South America; though
this continent certainly possessed no native horse at the time
of its discovery by the Spaniards. About twenty horses-one
of them standing no more than two and a half feet in heighthave been described from North America, in which continent
no indigenous horse existed at the time of its discovery.
Of the Rhzinoceridce, a hornless species (Acerot/lerium) occurs in
Miocene and Pliocene strata; but the best-known fossil species
is the two-horned woolly Rhinoceros (?. fichlorhzinus). This
curious species occurs in Post-pliocene deposits, and must have
ranged over the greater part of Europe.  It was adapted to a




614              MANUAL OF ZOOLOGY.
temperate climate, and, like the Mammoth, possessed a thick
covering of mixed wool and hair. This has been demonstrated
by the discovery of a frozen carcass in Siberia.
Of the Hzippopotamide, the earliest-known species is the.iDppopotamus major of the Pliocene period. This form agreed
in all essential respects with the living HY  am'phibius of Africa,
but it must have ranged over the whole of Southern Europe.
Hexaprotodon, of the Tertiary deposits of the Sivalik Hills of
India, is closely allied to Hijppopotamus, but had six lower
incisors.
Of the Suida, or Pig tribe, various extinct forms are known
from the Eocene and. Miocene rocks, where the family is
represented by the genera C/ezroy5otamus, Anthracotherium,
Hyopolamucs, and Hzipohyus.
As regards the past existence of the Ruminants, the Cervide,
or Stag tribe, is represented, for the first time in the Miocene
period, by the genus Dorcatherium.  The best-known species,
however, of this family is the ilfegacero-s Hibernicus, or so-called
Irish Elk (fig. 241), which is not a true Elk, but is intermediate
Fig. 241.-The Irish Elk (AIegaceros Hibernicus).
between the Fallow-deer and Reindeer.  A fossil Camel (C.
Sivalensis) has been discovered in the Tertiary deposits of the
Sivalik Hills of India. Of the Giraffe family-represented at
the present day by a single African species-a form has been
discovered in the Pliocene rocks of Greece, and has been
described under the name of Helladolherium.  Somewhat




DISTRIBUTION  OF MAMMALIA IN TIME.   6x5
similar forms have been found in the Pliocene deposits of the
Sivalik Hills of India.
The earliest-known Antelopes are Miocene, but the largest
and most extraordinary fossil examples of this family are two
gigantic four-horned. Antelopes, which occur in the Pliocene
strata of the Sivalik Hills of India, and have been described
under the names of Sivatlherium and Bramatherium.
The Bovide, or Ox tribe, has hitherto only occurred in rocks
not older than the Pliocene or Post-pliocene. At this latter
period England alone possessed four oxen-viz., the Lithuanian Aurochs (Bos bison or Baos priscus), the Wild Bull or
Urus (Bos primigenius), the Bos antiqus, and a small aboriginal
species, the Bos longifrons, believed by Owen to be " the source
of the domesticated cattle of the Celtic races before the Roman
invasion."
Order VI. Hyracoidea.-This little order, represented at
the present day by no more than the single genus Hyrax, is
not known to have any fossil representatives.
Order JVII. Proboscidea.-This order, including no other
living forms than the Elephants, came into existence in the
Miocene period, where it is represented by all its three sections, Deinotheriumn, Mastodon, and Elephas.
Fig. 242.-Skeleton of alnstoaodn.
The Deinotlerium (fig. 222) was a gigantic Miocene Mammal, probably something like the living Elephants, but having
no incisors in the upper jaw. In place of these, the lower jaw
was furnished with two long tusk-like incisors, which were
bent downwards.
In most essential respects the Mastodons (fig. 242) resemble
the Elephants, but the molar teeth were furnished with nippleshaped eminences.  Usually there are two tusk-shaped upper
incisors, but sometimes lower incisors are present as well




616             MANUAL OF ZOOLOGY.
Four Mastodons occur in the Miocene of Europe, and three
in that of India.
No Elephant has yet been discovered in the Miocene rocks
of Europe, but six species are known from Miocene strata in
India. In the Pliocene period Europe possessed its Elephants
(viz., E. priscus and E. meridionalis); but the best known of
the extinct Elephants, as well as the most modern, is the
Mammoth (E. primigenius, fig. 243). The Mammoth enjoyed
Fig. 243. —Skeleton of the Mammoth (EZeA'asfrnzigmiruJ.
a very extended geographical distribution, remains of it occurring in Britain, continental Europe, Siberia, and throughout a
large portion of North America. There can also be no question but that the Mammoth existed in the earlier portion of
the human period.
Order IX. Carnivora.-If the little Microlestes of the Upper
Trias be Marsupial, as is most probably the case, then the
order Carnivora is comparatively modern, the earliest undoubted remains having been found in the Eocene rocks.
The tribe of the FeZide is represented in the Miocene period
by the large Machairodus, with sabre-shaped upper canines.
Species of this genus must have been as large as a Lion. In
the later Pliocene and Post-pliocene deposits occur the remains
of a large Lion-the Cave-lion or Felis speaea —along with
which, in Britain and continental Europe, are the bones of a
large Hymena (H. spelcea) and a gigantic Bear (U rsus speuceus).
Remains of Wolves, Foxes, Badgers, Otters, Pole-cats, Weasels,
and other Carnivora are also found in various later Tertiary
deposits, and in bone-caves.
Order X. Rodentia.-No Rodent animal is as yet known to
have occurred earlier than the Eocene period. Here are found
forms allied to the living Dormouse and Squirrel. In the




DISTRIBUTION OF MAMMALIA IN TIME.   617
Miocene rocks occur numerous small Rodents.  In the Pliocene and Post-pliocene deposits the order is also well represented, the most remarkable form being the Great Beaver
(Trogontherizum), which appears to have survived into the historical period.
Order XI. Cheirojtera.-The earliest-known indications of
Bats are in the Eocene period, but the order is of no geological
importance.
Order XII. Inzsectivora.-.The Insectivorous Mammals, likewise, commenced their existence, so far as is known, in the
Eocene period; and they, also, are of no importance from a
geological point of view.
Order XIII. Quadrumana.-The earliest-known remains of
Quadrumana occur in the Miocene period. Several genera
are known, but the most important are Pliopithecus and Dryopithecus, both of which are European, and both of which belong
to the section of the Catarhine Monkeys which are at present
characteristic of the Old World. They appear to be most
nearly allied to the recent Gibbons. It is interesting to notice
that the American fossil Monkeys-from the later Tertiary
deposits of South America-belong to the division of the Quadrumana now peculiar to that continent —to the section,
namely, of the Platyrhine Monkeys.
GEOGRAPHICAL SUCCESSION OF ORGANIC FORMS.
A few words may be said here on a law which may be called
the " law of the geographical succession of organic forms," and
which is illustrated more completely by the Mammzalia than by
any other extinct animals. An examination, namely, of the
facts of the geological distribution of Mammals leads to the
striking generalisation that " the present distribution of organic
forms dates back to a period anterior to the origin of existing
species" (Lyell). In other words, though the extinct Mammals of the later geological deposits of any given country differ
specifically from those now existing in the same country, they
are nevertheless referable to the same orders, and are in every
respect more closely allied to the present Mammalian fauna
than to that of any other country. A few examples will render
this perfectly clear.
Australia at the present day is an altogether peculiar zoological province, characterised by the abundance and variety of
Marsupials which inhabit it. In the Post-tertiary deposits of
Australia, however, we are presented with proofs that Marsupials were just as characteristic of Australia during late geolo



618             MANUAL OF ZOOLOGY.
gical epochs as they are now. In the Post-pliocene period we
know that Australia was occupied by Kangaroos, Kangaroorats, Wombats, Phalangers, and Carnivorous Marsupials, in
every way representing the living Marsupials in zoological
value, but specifccally distinct, and generally of gigantic size.
In the same way, South America at the present day is especially characterised by a Mammalian fauna, containing many
peculiar forms, the Edentata being especially conspicuous, and
having a larger representation than in any other region. Similar but distinct forms, however, are found to have existed in
South America anterior to the creation of any existing species.
Thus, the modern Sloths of South America are represented by
the colossal Mylodon, Megaalonyx, Scelidothzeriunm, and Megat/heriunz. The little armour-plated Armadillos are represented by
the equally colossal Glyftodon. The Llamas-representing in
South America the Camels of the Old World-are represented
by the curious extinct genus Macrauc/zenia.  The Platyrhine
Monkeys have their extinct representatives.  Fossil Tapirs
take the place of the two existing species; and the Peccaries
are represented by at least five extinct species of Dicotyles.
Similarly, India is at present the only country in which fourhorned Antelopes occur; and it is in the Sivalik Hills that
there have been found the two gigantic four-horned Antelopes
which constitute the genera Sivatherium and Bramatherium.
In Europe, again, the Mammalian fauna of the later Tertiary
periods is much more closely allied to that now characterising
the Old World, than to that of the New. We have the Lion,
Bear, Wolf, Fox, and other well-known Carnizora.  Elephants,
Rhinoceroses, and Hippopotami, then as now, are characteristic
Old World forms. The Ruminants are equally characteristic
of the eastern hemisphere, though not exclusively confined to
it, and they have numerous and varied representatives in later
Tertiary deposits. The Giraffe is represented by the idl/adotheriurm, and the Bactrian Camel by the Meoycotheriurm of the
Siberian Drift. The fossil Quadrumana, too, of Europe, all
belong to the Catarhine section of the order.
It is unnecessary to pursue the subject further, but no law
is more firmly established than this: "That with extinct as
with existing Mammalia, particular forms were assigned to
particular provinces; and that the same forms were restricted
to the same provinces at a former geological period as they
are at the present day" (Owen).  It is to be borne in mind,
however, that the law, as just stated, holds good for the later
Tertiary period only, and does not apply, in any manner that
admits of being traced, to the earlier geological epochs.




TABLE OF VERTEBRATA.                 619
TABULAR VIEW OF THE CHIEF SUBDIVISIONS
OF THE SUB-KINGDOM  VERTEBRATA.
SUB-KINGDOM VI.-VERTEBRATA,
CLASS I. PISCES.
Order i. Pharyngobralnch ii.
2. Marsipobranchii.
3. Teleostei.
4. Ganoidei.
5. Elasmobranchii.
6. Dipnoi.
CLASS II. AMPHIBIA.
Order I. Labyrinthodont a.
2. Ophiomorpha.
3. Urodela.
4. Anoura.
CLASS III. REPTILIA.
Order I. Chelonia.
2. Ophidial.
3. Lacertilia.
4. Crocodilia.
5. Ichthyopterygia.
6. Sauropterygia.
7. Anomodontia.
8. Pterosauria.
9. Deinosauria.
CLAss IV. AVES.
Order I. Natatores.
2. Grallatores.
3. Cursores.
4. Rasores.
Sub-order a. Gallinacei.
b. Columbacei
5. Scansores.
6. Insessores.
Sub-order a. Conirostres,
b. Dentirostres.
c. Tenuirostres.
d. Fissirostres.
7. Raptores.
8. Saururxe.




620              MANUAL OF ZOOLOGY.
CLASS V. MAMMALIA.
Division A. Ornithodelphia.
Order I. Monotremata.
Division B. Didelphia.
Order 2. Marsupialia.
Division C. Monodelphia.
Order 3. Edentata.
4. Sirenia.
5. Cetacea.
6. Ungulata.
Section Perissodacdyla.
a. Multungula.
b. Solidungula.
Section Artiodactya.
a. Omnivora.
b. Ruminantia.
7. Hyracoidea.
8. Proboscidea.
9. Carnivora.
a. Pinnigrada.
b. Plantigrada.
c. Digitigrada.
xo. Rodentia.
Ix. Cheiroptera.
1 2. Insectivora.
13. Quadrumana.
a. Strepsirhina.
b. Platyrhina.
c. Catarhina.
14. Bimana.




GLOSSARY.
ABDOMEN (Lat. abdo, I conceal). The posterior cavity of the body, containing the intestines and others of the viscera. In many In-vertebrates there
is no separation of the body-cavity into thorax and abdomen, and it is only
in the higher Annulao that a distinct abdomen can be said to exist.
ABERRANT (Lat. aberro, I wander away). Departing from the regular type.
ABNORMAL (Lat. ab, from; norma, a rule). Irregular; deviating from the
ordinary standard.
ABOMASUM. The fourth cavity of the complex stomach of the Ruminants.
ABRANCHIATE (Gr. a, without; bragchia, gills). Destitute of gills or branchiae.
ACALEPH.E (Gr. akalephe, a nettle). Applied formerly to the Jelly-fishes or
Sea-nettles, and other Radiate animals, in consequence of their power of
stinging, derived from the presence of microscopic cells, called "threadcells," in the integument.
ACANTHOCEPHALA (Gr. akantha, a thorn; kephale, head). A class of parasitic
worms in which the head is armed with spines.
ACANTHOMETRINA (Gr. ackantha; and metra, the womb). A family of Protozoa,
characterised by having radiating siliceous spines.
ACANTHOPTERYGII (Gr. akantha, spine; pterux, wing).  A group of bony
fishes with spinous rays in the front part of the dorsal fin.
ACARINA (Gr. akari, a mite).  A division of the Aracha-ida, of which the
Cheese-mite is the type.
ACEPHALOUS (Gr. a, without; kephale, head). Not possessing a distinct head.
ACETABULA (Lat. acetabulusm, a cup). The suckers with which the cephalic
processes of many Cephalopoda (Cuttle-fishes) are provided.
ACETABULUM. The cup-shaped socket of the hip-joint in Vertebrates.
ACRITA (Gr. akritos, confused). A term sometimes employed as synonymous
with Pr-otozoa or the lowest division of the animal kingdom.
ACTINOMERES (Gr. aktin, a ray; meros, a part). The lobes which are mapped
out on the surface of the body of the Ctenophora, by the ctenophores, or
comb-like rows of cilia.
ACTINOSOMA (Gr. aktin; and soma, body). Employed to designate the entire
body of any Actinozoin, whether this be simple (as in the Sea-anemones),
or composed of several zooids (as in most Corals).
ACTINOZOA (Gr. aktin; and zoon, an animal).  That division of the Coelenterata of which the Sea-anemones may be taken as the type.
ADELARTHROSOMATA (Gr. adelos, hidden; arthros, joint; soma, body).  An
order of the Arachnida.
AGAMrC (Gr. a, without; games, marriage).  Applied to all forms of reproduction in which the sexes are not directly concerned.
ALLANTOIDEA. The group of Vertebrata in which the foetus is furnished with
an allantois, comprising the Reptiles, Birds, and Mammals.
ALLANTOIS (Gr. alias, a sausage). One of the "membranes" of the foetus in
certain Vertebrates.




622                         GLOSSARY.
ALVEOLI (Lat. dim. of alrus, belly). Applied to the sockets of the teeth.
AMBULACRA (Lat. ambulacrumn, a place for walking).  The perforated spaces
or "avenues" through which are protruded the tube-feet, by means of
which locomotion is effected in the Echinodermata.
AMBULATORY (Lat. ambulo, I walk).  Formed for walking.  Applied to a
single limb, or to an entire animal.
AMIETABOLIC.(Gr. a, without; mnetabole, change).  Applied to those insects
which do not possess wings when perfect, and which do not, therefore, pass
through any marked metamorphosis.
AMNION (Gr. aintos, a lamb).  One of the foetal membranes of the higher
Vertebrates.
AMNIIOTA. The group of Vertebrata in which the foetus is furnished with an
amnion, comprising the Reptiles, Birds, and Mammals.
AM(EBA (Gr. avnoibos, changing). A species of Rhizopod, so called from the
numerous changes of form which it undergoes.
Am(EBIFORM. Resembling an A mceba in form.
AMORPHOZOA (Gr. a, without; morphe, shape; zo6ih, animal). A name sometimes used to designate the Spongqes.
AMPHIBIA (Gr. amphi, both; bios, life).  The Frogs, Newts, and the like,
which have gills when young, but can always breathe air directly when
adult.
AMPHICCELOUS (Gr. amphi, at both ends; koilos, hollow). Applied to vertebrae which are concave at both ends.
AMPHIDISCS (Gr. araphi, at both ends; diskos, a qloit, or round plate). The
spicula which surround the gemmules of Sponyilla, and resemble two
toothed wheels united by an axle.
ANPHIOXUS (Gr. amphi, at both ends; oxus, sharp). The Lancelet, a little
fish, which alone constitutes the order Pharyngqobranchii.
AmPMPRNEEUSTA (Gr. amnphi, both; _pneo, I breathe). Applied to the " perennibranchiate " Amphibians which retain their gills througlh life.
AMPHIPODA (Gr. amphi; and pouens, a foot). An order of Crustacea.
ANAL (Lat. anus, the vent). Connected with the anus, or situated near the
anus.
ANALLANTOIDEA.  The group of Vertebrata in which the embryo is not furnished with an allantois.
ANALOGOUS. Applied to parts which perform the same function.
ANAMNIOTA. Tile group of Vertebrata in which the embryo is destitute of an
amnion.
ANARTHROPODA (Gr. a. without; arthros, a joint; pens, foot). That division of
A anulose animals in which there are no artist lated appendages.
ANCHYLOSIS or ANKYLOSTS (Gr. ar,,nklos, crocked). The union of two bones
by osseous matter, so that they become one bone, or are immovably joined
together.
ANDROGYNOUS (Gr. angr, a man;.une, a woman).  Synonymous with hermaphrodite, and implying that the two sexes are united in the same individual.
ANDROPHORES (Gr. aner, a man; and pheero, I carry). Applied to medusiform
gonophores of the Hlydrozoa, which carry the spermatozoa, and differ in
form from those in which the ova are developed.
ANNELIDA (a Gallicised form of Annulata).   The Ringed Worms, which
form one of the divisions of the Anarthr-opoda.
ANNULTXED. Composed of a succession of rings.
ANNULOIDA (Lat. annulus, a ring; Gr. eidos, form). The sub-kingdom com.
prising the Echinodermata and the Scolecida (= —Echiozoa).
ANNULOSA (Lat. aianulus). The sub-kingdom comprising the Anarfthropoda
and the Arthrolpoda or Articulata, in all of which the body is more or less
evidently composed of a succession of rings.
ANOMODONTIA (Gr. anomios, irregular; odous, tooth).  An extinct order of
Reptiles, often called Dicynodontia.
ANOMURA (Gr. anlomios, irregular; oura, tail). A tribe of Decapod Crust acea,
of which the Hermit-crab is the type.




GLOSSARY.                            623
ANOPLURA (Gr. anoplos, unarmed; oura, tail). An order of Apterous Insectq.
ANOURA (Gr. a, without; oura, tail).  The order of Amphilia comprising
the Frogs and Toads, in which the adult is destitute of a tail. Often called
Jatrachia.
ANTENNaE (Lat. antenna, a yard-arm). The jointed horns or feelers possessed
by the majority of the A rticulata.
ANTENNULES (dim. of antennce). Applied to the smaller pair of antennme in
the Crustacea.
ANTIBRACHIUM (Gr. anti, in front of; brachion, the arm).  The fore-arm of
the higher Vertebrates, composed of the radius and ulna.
ANTL.ERS. Properly the branches of the horns of the Deer tribe (Ceividee),
but generally applied to the entire horns.
ANTLIA (Lat. antlia, a pump).  The spiral trunk or proboscis with which
Butterflies and other Lepidopterous Insects suck up the juices of flowers.
APHANIPTERA (Gr. aphanos, inconspicuous; pteonz, a wing).  An order of
Insects comprising the Fleas.
APLACENTALIA. The section of the Mlammalia, comprising the two divisions
of the Didelphiac and Mozodelphia, in which the young is not furnished
with a placenta.
APODA (Gr. a, without; podes, feet). Applied to those fishes which have no
ventral fins. Also to the footless Caeciliee amongst the z mphibia.
AtPODAL. Devoid of feet.
APODEMATA (Gr. apodaio, I portion off).  Applied to certain chitinous septa
which divide the tissues in Csrustacea.
APTERA (Gr. a, without; pteron, a wing). A division of Insects, which is
characterised by the absence of wings in the adult condition.
APTEROUS. Devoid of wings.
APTERYX (Gr. a, without; pterux, a wing). A wingless bird of New Zealand,
belonging to the order Cursores.
ARACHNIDA (Gr. araclhne, a spider).  A class of the Articzclata, comprising
Spiders, Scorpions, and allied animals.
ARBORESCENT. Branched like a tree.
ARCHEOPTERYX (Gr. archaios, ancient; ptc2rx, wing).  The singular fossil
bird which alone constitutes the order of the Saururce.
ARCHENCEPHALA (Gr. archo, I overrule; egkephalos, brain). The name applied by Owen to his fourth and highest group of Mlnawnalia, comprising
Man alone.
ARENACEOUS. Sandy, or composed of grains of sand.
ARTICULATA (Lat. articulus, a joint).  A division of the animal kingdom,
comprising Insects, Centipedes, Spiders, and Crustaceans, characterised by
the possession of jointed bodies or jointed limbs. The term A rtliropoda is
now more usually employed.
ARTIODACTYLA (Gr. artios, even; daktilos, a finger or toe). A division of the
hoofed quadrupeds (Ungulata) in which each foot has an even number of
toes (two or four).
ASCIDIOIDA (Gr. askos, a bottle; eildos, a form). A synonym of Tunicata, a
class of Molluscous animals, which have the shape, in many cases, of a twonecked bottle.
ASEXUAL. Applied to modes of reproduction in which the sexes are not concerned.
ASIPHONATE. Not possessing a respiratory tube or siphon. (Applied to a
division of the Lamlellibrancliate Molluscs.)
ASTEROID (Gr. aster, a star; and eidos, form).  Star-shaped, or possessing
radiating lobes or rays like a star-fish.
ASTEROIDEA. An order of Echinodevrmata, comprising the Star-fishes, characterised by their rayed form.
ASTOMATOUS (Gr. a, without; stonza, mouth). Not possessing a mouth.
ATLAS (G'r. the god who holds up the earth). The first vertebra of the neck,
which articulates with and supports the skull.
ATIUrUM (Lat. a hall). Applied to the great?hamber or "cloaca," into which
the intestine opens in the Tanicata.




624                          GLOSSARY.
AURELLA (Lat. aurum, gold). Applied to the chrysalides of some Lepidoptera,
on account of their exhibiting a golden lustre.
AURICLE (Lat. dim. of awris, ear). Applied to one of the cavities of the
heart, by which.blood is driven into the ventricle.
AUTOPHAGI (Gr. autos, self; phago, I eat).  Applied to birds whose young
can run about and obtain food for themselves as soon as they escape from
the egg.
AVES (Lat. avis, a bird). The class of the Birds.
AVICULARIUM (Lat. avicula, dim. of avis, a bird). A singular appendage,
often shaped like the head of a bird, found in many of the Polyzoa.
Axis (Gr. axon, a pivot). The second vertebra of the neck, upon which the
skull and atlas usually rotate.
AZYGOS (Gr. a, without; zugos, yoke). Single; without a fellow.
BACTERIUM (Gr. baklerion, a staff). A kind of staff-shaped filament which
appears in organic infusions after they have been exposed to the air.
BALANIDE (Gr. balanos, an acorn).  A family of sessile Cirr-ipides, commonly called "Acorn-shells. "
BALEEN (Lat. baleeaa, a whale).  The horny plates which occupy the palate
of the true or "whale-bone" Whales.
BATIDES (Gr. batos, a bramble).  The falnily of the Elasmobhraec/lii comprising the Rayvs.
BATRACHIA (Gr. h)atrachos, a frog). Often loosely applied to any of the A mphibia, but sometimes restricted.to the Amphibians as a class, or to the
single order of the A noura.
BIFID.  Cleft into two parts; forked.
BILATERAL. Having to symmetrical sides.
BIMANA (Lat. bis, twice; manus, a hand). The order of Mammalia comprising Man alone.
BIPEDAL (Lat. bis, twice; pes, foot). Walking upon two legs.
BIRAMOUS (Lat. bis, twice; ramus, a branch). Applied to a limb which is
divided into two branches (e.g., the limbs of Cirripedes).
BIVALVE (Lat. his, twice; valvve, folding-doors). Composed of two plates or
valves; applied to the shell of the Lamellibranchiata and Brachiop,da,
and of the carapace of certain Crustacea.
BLASTOIDEA (Gr. blastos, a bud; and eidos, form). An extinct order of Echi.
nodermata, often called Pent-emites.
BRACHIOPODA (Gr. brachion, an arm; pous, the foot). A class of the Molluscoida, often called "Lamp-shells," characterised by possessing two
fleshy arms continued from the sides of the mouth.
BRACHIUM (Gr. brachion, arm). Applied to the upper arm of Vertebrates
BRACHYURA (Gr. brachus., short; oura, tail).  A tribe of the Decapod Crustaceans with short tails (i.e., the Crabs).
BRACTS. (See Hydrophyllia.)
BRADYPODIDAE (Gr. bradus, slow; podes, feet).  The family of Edentata comprising the Sloths.
BRANCHIA (Gr. bragchia, the gill of a fish). A respiratory organ adapted to
breathe air dissolved in water.
BRANCHIATE. Possessing gills or branchice.
BRANCHIFERA (Gr. bragchia, gill; and phero, I carry). A division of Gasteropodous Molluscs, in which the respiration is aquatic, and the respiratory
organs are mostly in the form of distinct gills.
BRANCHIO-GASTEROPODA (= Branchifera).
BRANCHIOPODA (Gr. bragchia; and pous, foot). A legion of Crustacea, in
which the gills are supported by the feet.
BRANCHIOSTEGAL (Gr. bragchia, gills; stego, I cover). Applied to a membrane
and rays by which the gills are protected in many fishes.
BREVILINGUIA (Lat. brevis, short; lingua, tongue).  A division of the Lacertilta.
BREVIPENNATAS (Lat. brevis, short; penna, a wing). A group of the Nataturial Birds.




GLOSSARY.                            625
BRONCHI (Gr. broqehos, the windpipe).  The branches of the windpipe
(trachea), by which the air is conveyed, to the vesicles of the lung.
BRUTA (Lat. brutus, heavy, stupid). Often used to designate the Mammalian order of the Edentata.
BRYOZOA (Gr. bruon, moss; zoin, animal). A synonym of Polyzoa, a class of
the Mollu.scoida.
BucCAL (Lat. bucca, mouth or cheeks). Connected with the mouth.
BURSIFORM (Lat. bursa, a purse; forma, shape).  Shaped like a purse; subspherical.
BYSSIFEROUS. Producing a byssus.
BYssUS (Gr. busses, flax). A term applied to the silky filaments by which the
Pinna, the common Mussel, and certain other bivalve Mollu ca, attach
themselves to foreign objects.
CADUCIBRANCHIATE (Lat. caducus, falling off; Or. bragchia, gill). Applied
to those Amphibians in which the gills fall off before maturity is reached.
CADUCoUS. Applied to parts which fall off or are shed during the life of the
animal.
CAECAL (Lat. ccecus, blind). Terminating blindly, or in a closed extremity.
C CcuM (Lat. ccacus); A tube which terminates blindly.
CESPITOSE (Lat. ccespes, a turf). Tufted.
CAINOZOIC. (See Kainozoic.)
CALCAR (Lat. a spur). Applied to the "spurs" of Rasorial Birds; and also
to the rudiments of the hind-limbs in certain Snakes.
CALCAREOUS (Lat. calx, lime). Composed of carbonate of lime.
CALICE. The little cup in which the polype of a coralligenous Zoophyte
(Actinozo6n) is contained.
CALYCOPHORID2E (Gr. kalux, a cup; and phecro, I carry). An order of the
Oceanic Hydrozoa, so called from their possessing bell-shaped swimming
organs (nectocalyces).
CALYX (Lat. calyx, a cup). Applied to the cup-shaped body of Vorticella
(Protozoa), or of a Crinoid (Echinodermata).
CAMPANULARIDA (Lat. campanula, a bell). An order of Hydroid Zoophytes.
CANINE (Lat. canis, a dog). The eye-tooth of Mammals, or the tooth which
is placed at or close to the prnemaxillary suture in the upper jaw, and the
corresponding tooth in the lower jaw.
CAPITULUM (Lat. dim. of caput, bead). Applied to the body of a Barnacle
(Lepadidce), from its being supported upon a stalk or peduncle.
CARAPACE. A protective shield. Applied to the upper shell of Crabs, Lobsters, and many other Crustacea; also to the case with which certain of the
Infusoria are provided. Also the upper half of the immovable case in which
the body of a Chelonian is protected.
CARINATA (Lat. carina, a keel). Applied by Huxley to all those birds in
which the sternum is furnished with a median ridge or keel.
CARNIVORA (Lat. care, flesh; voro, I devour). An order of the Mammalia.
CARNIVOROUS (Lat. care, flesh; voro, I devour). Feeding upon flesh.
CARNOSE (Lat. care). Fleshy.
CARPOPHAGA (Gr. karpos, fruit; phago, I eat). A section of the Marsupialia.
CARPUS (Gr. karpos, the wrist). The small bones which intervene between
the fore-arm and the metacarpus.
CATARHINA (Gr. kata, downwards; rhines, nostrils). A group of the Quadrumana.
CAUDAL (Lat. cauda, the tail). Belonging to the tail.
CAVICORNIA (Lat. cavus, hollor; cornu, a horn).  The "hollow-horned"
Ruminants, in which the horn consists of a central bony " horn-core " surrounded by a horny sheath.
CENTRUM (Gr. kentron, the point round which a circle is described by a pair
of compasses). The central portion or "body" of a vertebra.
CEPHALIC (Gr. kephale, head). Belonging to the head.
CE:PIIALO-BRANCHIATE (Gr. kephale; and bragchia, gill). Carrying gills upon




626                           GLOSSARY.
the head. Applied to a section of the Annelida, which, like the Seralke,
have tufts of external gills placed upon the head.
CEPHALOPHORA (Gr. kephale; and phero, I carry). Used synonymously with
Encephala, to designate those Mollusca which possess a distinct head.
CEPHALOPODA (Gr. kephale; and podes, feet). A class of the Mollusca, comprising the Cuttle-fishes and their allies, in which there is a series of arms
ranged round the head.
CEPHALOTHOR.AX (Gr. kephale; and thorax, chest). The anterior division of
the body in many Crustacea and Arachnida, which is composed of the
coalesced head and chest.
CEItE. The naked space found at the base of the bill of some birds.
CERVICAL (Lat. cervix, neck). Connected with the region of the neck.
CESTOIDEA (Gr. kestos, a girdle).  An old name for the Tceniada, a class of
intestinal worms with flat bodies like tape (hence the name Tapeworms).
CESTRAPHORI (Gr. kestra, a weapon; phero, I carry). The group of Elasmobranchii represented at the present day by the Port Jackson Shark.
CETACEA (Gr. ketos, a whale). The order of Mammals comprising the Whales
and Dolphins.
CHI.ETOGNATHA (Gr. chaite, bristle; gnathos, jaw). An order of the Anzarthropoda, comprising only the oceanic genus Sagitta.
CHEIROPTERA (Gr. cheir, hand; pteron, a wing).  The order of Mammals
comprising the Bats.
CHELE  (Gr. chele, a claw).  The prehensile claws with which some of the
limbs are terminated in certain Crustacea, such as the Crab, Lobster, &c.
CHELATE. Possessing chelie; applied to a limb.
CHELICER2E (Gr. chele, a claw; and keras, a horn).  The prehensile claws of
the Scorpion, supposed to be homologous with antennoe.
CHELONIA (Gr. chelone, a tortoise).  The order of Reptiles comprising the
Tortoises and Turtles.
CHELONOBATRACHIA (Gr. chelone, a tortoise; batrachos, a frog).  Sometimes
applied to the Amphibian order of the Anoura (Frogs and Toads).
CHILOGNATHA (Gr. cheilos, a lip; and guathos, a jaw). An order of the Myriapoda.
CHILOPODA (Gr. cheilos; andpodes, feet). An order of the Myriapoda.
CHITINE (Or. chitonl, a coat).  The peculiar chemical principle, nearly allied
to horn, which forms the exoskeleton in many Invertebrate animals, especially in the Arthropoda (Crustacea, Insecta, &c.)
CHLOROPHYLL (Gr. chloros, green; and hyllos, a leaf).  The green colouring
matter of plants.
CHROMATOPHORES (Gr. chroma, complexion, or colour; and phero, I carry).
Little sacs which contain pigment-grainules, and are found in the integument of Cuttle-fishes.
CHRYSALIS (Gr. chrusos, gold). The motionless pupa of butterflies and moths,
so called because sometimes exhibiting a golden lustre.
CHYLAQUEOUS FLUID. A fluid consisting partly of water derived from the
exterior, and partly of the products of digestion (chyle), occupying the
body-cavity or perivisceral space in many Invertebrates (An nielides, Echinocleirms, &c.), and sometimes having a special canal-systemn for its conduction
(chylaqueous canals).
CHY~E (Gr. chulos, juice).  The milky fluid which is the result of the action
of the various digestive fluids upon the food.
CHYLIFIC (Gr. chulos, juice [chyle]; and Lat. facio, I make).  Producing
chyle. Applied to one of the stomachs, when more than one is present.
The word is of mongrel origin; and " chylopoietic" is more correct.
CHYME (Gr. chumros, juice). The acid pasty fluid produced by the action of
the gastric juice upon the food.
CHYME-MASS. The central, semi-fluid sarcode in the interior of an Infusorian.
CILIA (Lat. cilium, an eyelash). Microscopic, hair-like filaments, which have
the power of lashing backwards and forwards, thus creating currents in
the surrounding or contiguous fluid, or subserving locomotion in the animal
which possesses them.




GLOSSARY.                              627
CILIOGnADA (Lat. ciltzsm; and gradior, I walk). Synonymous with Cteaophora,
an order of Actinozoa.
CINCLIDES (Gr. kiglis, a lattice).  Special apertures in the column-walls of
some Sea-aiiemones (ActiZice), which probably serve for the emission of the
cord-like "craspeda."
CIRRI (Lat. cirrus, a curl). Tendril-like appendages, such as the feet of Barnacles and'Acorn-shells (CirriHpedes), the lateral processes on the arms of
Bracliopoda, &c.
CIRRIFJsEROUS or CIRnIGEROU8. Carrying cirri.
CIRRIPEDIA, CIRRHIPEDIA, or CIRRHOPODA (Lat. cirrus, a curl; and pes, a
foot). A sub-class of Crustacea with curled jointed feet.
CIRROSTOMI (Lat. cirrus, a tendril; Gr. stoma, mouth). Sometimes used to
designate the Phaaryngobranclhii.
CLADOCERA (Gr. klados, a branch; keras, a horn).  An order of Crustacea
with branched antennme.
CLAVATE (Lat. clatvus, a club). Club-shaped.
CLAVICLE (Lat. clavicula, a little key). The "collar-bone," forming one of
the elements of the pectoral arch of Vertebrates.
CJOACA (Lat. a sink). The cavity into which the intestinal canal and the
ducts of the generative and urinary organs open in common, in some Invertebrates (e.g., in Insects), and also in many Vertebrate animals.
CLYPEIFORM (Lat. clypeus, a shield; and forma, shape). Shield-shaped; applied, for example, to the carapace of the King-crab.
CNIDE (Gr. knide, a nettle). The urticating cells, or "thread-cells," whereby
many Coelenterate animals obtain their power of stinging.
COCCOLITHS (Gr. kokkos, a berry; lithos, stone).  Minute oval or rounded
bodies, which are found either free or attached to the surface of coccospheres.
COCCOSPHERES (Gr. kokkos; and sp2haira, a sphere). Spherical masses of sar.
code, enclosed in a delicate calcareous envelope, and bearing coccoliths
upon their external surface. Both coccospheres and coccoliths are embedded in a diffused plasmodium of sarcode, the whole constituting a low
RhBizopodic organism.
COCCYGEAL. Connected with the coccyx.
Coccyx (Gr. kokkux, a cuckoo). The terminal portion of the spinal column
in man, so called from its resemblance to a cuckoo's beak.
CocooN (French cocoJI, the cocoon of the silk-worm; connected with Fr.
coque, shell, which is derived from the Lat. concha). The outer covering of
silky hairs with which the pupa or chrysalis of many insects is protected.
CODONOSTOMA (Gr. kodon, a bell; stoma, mouth). The aperture or mouth of
the disc (nectocalyx) of a Medusa, or of the bell (gonocalyx) of a mechisiform gonophore.
CELENTERATA (Gr. koilos, hollow; eonteron, the bowel).  The sub-kingdor
which comprises the Hgdrozoa and Actinozoa.  Proposed by Frey and
Leuckhart in place of the old term  Radiata, which included other animals
as well.
C(ENENCHYMA (Gr. koinos, common.; encluuma, tissue).  The common calcareous tissue which unites together the various corallites of a compound
corallum.
C(ENECIUM (Gr. koinos, common; oikos, house). The entire dermal system
of any Pol/zool-: employed in place of the terms polyzoary or polypidom.
C(ENOSARC (Gr. koinos, common; scrx, flesh). The common organised medium by which the separate polypites of a compound Jlydrozode are connected together.
COLEOPTERA (Gr. koleos, a sheath; ptereso, wing).  The order of Insects
(Beetles) in which the anterior pair of wings are hardened, and serve as
protective cases for the posterior pair of membranous wings.
COLUBRINA (Lat. collber, a snake). A division of the Ophidia.
COLUMBACEI (Lat. columba, a dove).  The division of Rasorial Birds comprising the Doves and Pigeons.
COLUMELLA (Lat. dim. of coltmena, a column).  In Conchology, the central
fS8




628                           GLOSSARY.
axis round which the whorls of a spiral univalve are wound. Amongst the
Actinozoa, it is the central axis or pillar which is found in the centre of the
thecea of many corals.
COLUMN. Applied to the cylindrical body of a Sea-anemone (Alctinia); also
to the jointed stem or peduncle of the stalked Crinoids.
COMMISSURAL (Lat. committo, I solder together).  Connecting together;
usually applied to the nerve-fibres which unite different ganglia.
CONcHA (Lat. a shell). The external ear by which sounds are collected and
transmitted to the internal ear.
CONCHIFERA (Lat. concha, a shell; fero, I carry). Shell-fish. Applied in a
restricted sense to the bivalve Molluscs, and used as a synonym for Lamellibranchiata.
CONDYLE (Gr. kondulos, a knuckle). The surface by which one bone articulates
with another. Applied especially to the articular surface or surfaces by
which the skull articulates with the vertebral column.
CONIROSTRES (Lat. conlus, a cone; rostrum, a beak).  The division of Perching
Birds with conical beaks.
COPEPODA (Gr. kope, an oar; podes, feet). An order of Crustacea.
CORACOID (Gr. korax, a crow; eidos, form).  One of the bones which enters
into the composition of the pectoral arch in Birds, Reptiles, and Monotremes. In most Mammals it is a mere process of the scapula, having, in
man, some resemblance in shape to the beak of a crow.
CORALLIGENOUS. Producing a corallum.
CORALLITE. The corallum secreted by an Actinozod6a which consists of a
single polype; or the por tion of a composite corallum which belongs to, and
is secreted by, an indivilial polype.
CORALLUM (from the Latin for red coral). The hard structures deposited in,
or by, the tissues of an A ctinozo6n-commonly called a " coral."
CORIACEOUS (Lat corium, hide). Leathery.
CORPUS CALLOSUM (Lat. the "firm body"). The great band of nervous matter which unites the two hemispheres of the cerebrum in the Mammals.
CORPUSCULATED (Lat. corpzscuzlum, a little body or particle).  Applied to
fluids which, like the blood, contain floating solid particles or "corpuscles."
CORTICAL LAYER.  T'he layer of consistent sarcode, which in the lntfusoria
encloses the chyme mass, and is surrounded by the cuticle. Sometimes
called the " parenchyma of the body."
CosTSe (Lat. costa, a rib).  Applied amongst the Crinoidea to designate the
rows of plates which succeed the inferior or basal portion of the cup (pelvis).  Amongst the Corals the "costee" are vertical ridges which occur
on the outer surface of the theca, and mark the position of the septa
within.
COSTAL (Lat. costa, a rib). Connected with the ribs.
CRANIUM (Gr. kranion, the skull). The bony or cartilaginous case in which
the brain is contained.
CRASPEDA (Gr. kraspedon, a margin or fringe). The long, convoluted cords,
containing thread-cells, which are attached to the free margins of the
mesenteries of a Sea-anemone.
CREPUSCULAR (Lat. crepusculum, dusk). Applied to animals which are active
in the dusk on twilight.
CRINOIDEA. (Gr. kr;inos, a lily; eidos, form). An order of Echinodermnata, comprising forms which are usually stalked, and sometimes resemble lilies in
shape.
CROCODILIA (Gr. krlokodeilos, a crocodile). An order of Reptiles.
CROP. A partial dilatation of the gullet, technically called " ingluvies."
CRUSTACEA (Lat. crusta, a crust).  A class of articulate animals, comprising
Crabs, Lobsters, &c., characterised by the possession of a hard shell or
crust, which they cast periodically.
CTENOCYST (Gr. kteis, a comb; kustis, a bag or cyst). The sense-organ (probably auditory) which occurs in the Cteqophor-a.
CTENOID (Gr. Rteis, a comb; eidos, form). Applied to those scales of fishes,
the hinder margins of which are fringed with spines or comb-like projections




GLOSSARY.                                 629
CTENOPImORAt (Or. f2ics, a comb; and pliero, I carry).  An order of Actinozoa.
comprising oceanic creatures, which swim  by means of "etenophores," or
banlds of cilia arallngOed in comb-like plates.
CUgsORES (Lat. cqn'vro, I run).  An order of Aves, comprising birds destitute
of the power of flight, but formed for running vigorously (e.g., the Ostrich
and Emeu).
CUSPIDATE.  Furnislhed with small pointed eminences or'" cusps."
CUTICLE (Lat. cedt;cula, dim. of cu2ls, Slin).  The pellicle which forms the
outer layer of the body amongst the Izfitsoria.  The outer layer of the iln
tegument generally.
CuTIrs (Lat. skin).  The inferior vascular layer of the integument, often called
the cutis vera, the coeoiun, or the dermea.
CYCLOID (Cr. keklos, a circle; eidos, form).  Applied to those scales of fishes
which have a regularly circular or elliptical outline with an even margin.
CYCLOSToToI.  Sometimes used to designate the fag-fishes and Lampreys,
forming the order lln ars?)obo  ac/h i.
CYST (Gro kEstis, a bladder or bag).  A sac or vesicle.
CYsTICA.  The embryonic forms (scolices) of certain intestinal worms (Tapeworms), which were described as a distinct order, until their true nature
was discovered.
CYST()IDEA (Gr. kustis, a bladder; and eidos, form).  An extinct order of,chie/eodeirmata.
DECAPODA (Gr. delCa, ten; podes, feet).  The division of Crtstacccec which have
ten ambulatory feet; also the family of Cuttle-fishes, in which there are
ten arms or ceph'lic processes.
DEcmIDuous (Lat. cecido, I fall off). Applied to parts which fall off or are
shed during the life of the animal.
DECOLLATED (Lat. decollo, I behead).  Applied to univalve shells,, the apex of
which falls off in the course of growth.
DEINOSAURnIA (Gr. deineos, terrible; sats'na, lizard).  Aln extinct order of Reptiles.
DENDnRIFORr, DENDRITIC, DENDROID (Gr. dendclon, a tree).  Branched like a
tree, arborescent.
DENTIIOSTRES (Lat. dens, a tooth; r-ost'run, a beak).  The group of Perchi),g
Birds in which the upper mandible of the beak has its lower margin toothed.
DERMA.  (See Cutis.)
D)EnRAL (Gr. derma, skin).  Belonging to the integument.
I)EIRMOSOLERITES (Gr. deirme, slin; skleros, hard).  Masses of spicules which
occur in the tissues of some of the A lc/yonidce (A ctieozoa).
DsSMIDI2E.    Minute fresh-water plants, of a green colour, without a siliceous
epidermis.
DEUTEnOZO0IDS (Gr. devlteeros, second; zoen, animal; eidos, form).  The zohiids
which are produced by genmmation from zooids.
D1XTRAL (Lat. dextla, the right hand). Right-handed; applied to the direction of the spiral in the greater number of univalve shells.
DIAPHRAGAM (Gr. diapl-cagima, a partition).  The " midriff," or the muscle
which in Maam7aealia forms a partition between the cavities of the thorax
and abdomen.
DIASTEMA (Or. dia, apart;,histemi, to place).  A gap or interval, especially
between teeth.
DIASTOLE (Gr. diastello  I separate or expand).  The expansion of a contractile
cavity such as -the heart, which follows its contraction or "C systole."
DIATOMACE.ZE (Gr. diateanno, I sever).  An order of minute plants, which are
provided with siliceous envelopes.
DIBRnNCHAlTA (Gr. dis, twice; brcaqclcia, gill).  Tle order of Ce/)7nalpojoda
(comprising the Cuttle-fishes, &c.) in which only two gills are present.
DICYNODONTIA (Gr. dis, twice; kuose, dog; odous, tooth).  An extinct order
of Reptiles.
DIDELPHIA (Gr. dis, twice; ddei7t/s, womb).   The subdivision of Mammals
comprising the lMarsupials,




630                          GLOSSARY.
DIGIT (Lat. digitus, a finger). A finger or toe.
DIGITIGRADA (Lat. digitus; gradior, I walk). A subdivision of the Carnivora.
DIGITIORADE.  Walking upon the tips of the toes, and not upon the soles of
the feet.
DIMEROSOMATA (Gr. dis; meros, part; soma, body). An order of Arachlnida,
comprising the true Spiders, so called from the marked division of the body
into two regions, the cephalothorax and abdomen. The name Araneidca is
often employed for the order.
DIMYARY (Gr. dis, twice; muong, muscle). Applied to those bivalve Molluscs
(Lanellibranchiata) in which the shell is closed by two adductor muscles.
DlasCIOus (Gr. dis, twice; oikos, house).  Having the sexes distinct; applied
to species which consist of male and female individuals.
DIPHYODONT (Gr. dis, twice; phuo, I generate; odous, tooth). Applied to
those Mammals which have two sets of teeth.
DIPHYOZOOIDS. Detached reproductive portions of adult Calycole]koride, an
order of oceanic Hydrozoa.
DIPNoi (Gr. dis, twice; pnoe, breath).  The order of fishes represented by
the Lep idosiren.
DIPTERA (Gr. dis, twice; pteron, wing). An order of Insects characterised
by the possession of two wingcs.
DIscoID (Gr. diskos, a quoit; eidos, form).  Shaped like a round plate or quoit.
DISCOPHORA (Gr. diskos, a quoit; phero, I carry).  This term'is applied to
the JIleditsce, or Jelly-fishes, from their form; and is sometimes used to
designate the order of the Leeches (Iliruldinea), from the suctorial discs
which these animals possess.
DISSEPIMENTS (Lat. dissepio, I partition off). Partitions. Used in a restricted
sense to designate certain imperfect transverse partitions, which grow from
the septa of many corals.
DIsTAL. Applied to the quickly growing end of the hydrosoma of a Hrydrozo6n; the opposite, or "proximal," extremity growing less rapidly, and
being the end by which the organism is fixed, when attached at all.
DIURNAL (Lat. dies, day). Applied to animals which are active during the
day.
DiVERTICULUM (Lat. diverticdsluxn, a by-road).  A lateral tube with a blind
extremity springing from the side of another tube.
DORSAL (Lat. dersium, back). Connected with the back.
DORSIBRANCHIATE (Lat. dorsum, the back; Gr. braychia, gill). Having external gills attached to the back; applied to certain Annelides and Molluscs.
The term is of mongrel composition, and "notobranchiate" is more correctly
employed.
ECDERON (Gr. ek, out; deros, skin). The outer plane of growth of the external integumetntary layer (viz., the ectoderm, or epidermis).
ECDYSIS (G1. ekdusis, a stripping off). A shedding or moulting of the skin.
EcHINOCocCs (Gr. eclhinos, a hedgehog; kokkos, a berry). The larval forms
(scolices) of tie tapeworm of the dog (Teenia ecleinococcus), commonly known
as "Lhydatids. "
ECRINODERMATA (Gr. echinos; and derma, skin). A class of animals comprising the Sea-urchins, Star-fishes, and others, most of which have spiny
skins.
ECHINOIDn A (Gr. echin?os; and eidos, form). An order of Echinodermata, comprising the Sea-urchins.
ECHINULATE. Possessing spines.
ECTOCYST (Gr. ektos, outside; kustis, a bladder). The external investment of
the ccencecium of a Polyzoon.
ECTODERM (Gr. ektos; and derena, skin)). The external integumentary layer of
the C/leanterata.
ECTOSARC (Gr. ektos; sasx, flesh). The outer transparent sarcode-layer of certain RPhizopods, such as the A mrba.
EDENTATA (Lat. e, without; dens, tooth).  An order of Jlclnnmalzia often
called Brata.




GLOSSARY.                              63 
EDENTULOUS.  Toothless; without any dental apparatus.  Applied to the
mouth of any animal, or to the hinge of the bivalve Molluscs.
EDRIOPHTHALMATA (Gr. hedcalios, sitting; opht/halmos, eye). The division of
Czrustacea in which the eyes are sessile, and are not supported upon stalks.
ELASMOBRANCHII (Gr. elasma, a plate; braqch/ia, gill). An order of Fishes,
including the Sharks and Rays.
ELYTRA (Gr. elutron, a sheath). The chitinous anterior pair of wings in
Beetles, which form cases for the posterior membranous wings. Also applied to the scales or plates on the back of the Sea-mouse (A/pl-rodite).
EMBRYO (Gr. en, in; bruo, I swell). The earliest stage at which the young
animal is recognisable in the impregnated ovum.
ENCEPHALON (Gr. eycephllos, brain).  The portion of the cerebro-spinal nervous axis contained within the cranium.
ENCEPHALOUS  Gr. en, in; kephale, the head).  Possessing a distinct head.
Usually applied to all the M1ollusca proper, except the Lamellibranchicata.
ENCYSTATION (Gr. en, in; kustis, a bag). The transformation undergone by
certain of the Protozoa, when they become motionless, and surround themselves by a thick coating or cyst.
ENDERON (Gr. eln, in; deros, skin). The inner plane of growth of the outer
integumentary layer (viz., the ectoderm, or epidermis).
ENDOCYST (Gr. endon, within; kustis, a bag).  The inner membrane or integumentary layer of a Polyzo6n. In Cristatella, where there is no "ectocyst,"
the endocyst constitutes the entire integument.
ENDODERM (Gr. endon; and derma, skin).  The inner integumentary layer of
the Coelenterata.
ENDOPODITE (Gr. endon; and pens, foot). The inner of the two secondary
joints into which the typical limb of a Crustacean is divided.
ENDOSARC (Gr. endon; and sarx, ties}h). The inner molecular layer of sarcode
in the Amoeba, and other allied Rhlizopods.
ENDOSKELETON (Gr. eudon; and skelctos, dry). The internal hard structures,
such as bones, which serve for the attachment of muscles, or the protection
of organs, and which are not a mere hardening of the integument.
ENSIFORM (Lat. ensis, a sword; fortna, shape). Sword-shaped.
ENTOMOPHAGA (Gr. entoama, insects; ophugo, I eat). A section of the Marsupialia.
ENTOMOSTRACA (Gr. entoma, insects; ostrakon, a shell).  Literally, shelled
insects-applied to a division of Crustacea.
ENTOZOA (Gr. eutos, within; zodat, animal). Animals which are parasitic in
the interior of other animals.
EOCENE (Gr. eos, dawn; kainos, new or recent). The lowest division of the
Tertiary rocks, in which species of existing shells are to a small extent
represented.
EPIDERMIS (Gr. epi, upon; derma, the true skin).  The outer non-vascular
layer of the skin, often called the scarf-skin or cuticle.
EPIMERA (Gr. epi, upon; mterof, thigh). The lateral pieces of the dorsal are
of the somite of a Crustacean.
EPIPoDIA (Gr. epi, upon; pous, the foot). Muscular lobes developed from
the lateral and upper surfaces of the " foot " of some Molluscs.
EPIPODITE (Gr. epi, upon; pous, foot). A process developed upon the basal
joint, or " protopodite," of some of the limbs of certain Crustacea.
EPISTERNA (Gr. epi, upon; sternon, the breast-bone).  The lateral pieces of
the inferior or ventral arc of the soemite of a Crustacean.
EPISTOME (Gr. epi; and stoma, mouth). A valve-like organ which arches over
the mouth in certain of the Polyzoa.
EPITHECA (Gr. epi; and theke, a sheath). A continuous layer surrounding the
thecae in some Corals, and being the external indications of tabule.
EPIZOA (Gr. epi, upon; zood, animal).  Animals which are parasitic upon
other animals. In a restricted sense, a division of Crustacea which are
parasitic upon fishes.
EQUILATERAL (Lat. cequus, equal; latus, side). Having its sides equal. Usually applied to the shells of the Brac/iopoda.  When applied to the spiral




632                         GLOSSARY.
shells of the Foraminifera, it means that all the convolutions of the shell
lie in the same plane.
EQUIVALVE (Lat. sequals, equal; valvte, folding-doors).  Applied to shells
which are composed of two equal pieces or valves.
ERRANTIA (Lat. erro, I wander). An order of Annelida, often called Nereidea,
distinguished by their great locomotive powers.
EURYPTERIDA (Gr. eurus, broad; pteron, wing).  An extinct sub-order of
Crulstacea.
EXOPODITE (Gr. exo, outside; poes, foot). The outer of the two secondary
joints into which the typical limb of a Crustacean is divided.
EXOSKELETON (Gr. exo, outside;'skeletos, dry). The external skeleton, which
is constituted by a hardening bf the integument, and is often called a
"dermoskeleton. "
FASCICULATED (Lat. fasciculus, a bundle). Arranged in bundles.
FAUNA (Lat. Fcuni, the rural deities of the Romans). The general assemblage of the animals of any region or district.
FEMUR. The thigh-bone, intervening between the pelvis and the bones of
the leg proper (tibia and fibala).
FIBULA (Lat. a brooch). The outermost of the two bones of the leg in the
higher Vertebrata; corresponding to the tlsla of the fore-arm.
FILIFORM (Lat. filunm, a thread; formna, shape). Thread-shaped.
FISSILINGUIA (Lat. findo, I cleave; lingua, tongue). A division of Lacertilia,
with bifid tongues.
FISSION (Lat. findo, I cleave). Multiplication by means of a process of seltf
division.
FISSIPAROUS (Lat. findo; and pario, I produce). Giving origin to fresh structures by a process of fission.
FISSIROSTRES (Lat. findo, I cleave; rostrum, beak).  A sub-order of the
Perching Birds.
FLAGELLUM (Lat. for whip). The lash-like appendage exhibited by many Infusoria, which are therefore said to be "flagellate."
FLORA (Lat. Flora, the goddess of flowers). The general assemblage of the
plants of any region or district.
FOOT-JAWS. The limbs of Crustacea, which are modified to subserve mastication.
FOOT-SECRETION. The term applied by Mr Dana to the sclerobasic corallum
of certain A ctinozoa.
FOOT-TUBERCLES.  The unarticulated appendages of the Annelida, often
called parapodia.
FORAMINIFERA (Lat. foramen, an aperture; fero, I carry). An order of Protozoa, usually characterised by the possession of a shell perforated by
numerous pseudopodial apertures.
FRUGIVOROUS (Lat. frux, fruit; voro, I devour). Living upon fruits.
FURCULUM (Lat. dim. of furca, a fork). The " merry-thought " of birds, or
the V-shaped bone formed by the united clavicles.
FUSIFORM (Lat. fusus, a spindle; and foryma, shape). Spindle-shaped, or
pointed at both ends.
GALLINACEI (Lat. gallina, a fowl). Sometimes applied to the whole order of
the Rasorial Birds, but properly restricted to that section of the order of
which the common Fowl is a typical example.
GANOLION (Gr. gagglion, a knot). A mass of nervous matter containing nervecells, giving origir to nerve-fibres.
GANOID (Gr. ganos, splendour, brightsess). Applied to those scales or plates
which are composed of an inferior layer of true bone covered by a superior
layer of polished enamel.
GANoIDEI. An order of Fishes.
GASTEROPODA (Gr. gaster, stomach; pous, foot). The class of the 2Iolluscae
comprising the ordinary univalves, in which locomotion is usually effected
by a muscular expansion of the under surface of the body (the " foot ").




GLOSSARY.                            633
GEIMAm (Lat. gewma, a bud). The buds produced by any animal, whether.
detached or not.
GEMMATION. The process of producing new structures by budding.
GEMMIPAROUS (Lat. geanita, a bud; paeio, I produce). Giving origin to new
structures by a process of budding.
GEMMULFES tLat. dinl. of gelnmma). The ciliated embryos of many C'clentefrata;
also the seed-like reproductive bodies or " spores " of SJosyila.
GEPHYREA (Gr. gephura, a bridge). A class of the Anart/lropodoa, comprising
the Spoon-worms (Sipuz2cults) and their allies.
GIZZARD. A muscular division of the stomach in-Birds, Insects, &c.
GLADIUS (Lat. a sword). Applied to the horny endoskeleton or "pen" of
certain Cuttle-tishes.
GLENOID (Gr. yleeae, a cavity; eidos, form). A shallow cavity; applied especially to the shallow articular cavity in the shoulder-blade to which the head
of the h'umerus is jointed.
GNATHITES (Gr. qnatlos, a jaw). The masticatory organs of Crastacea.
GONOBLASTIDIA (Gr. yogenos, offspring; blastidiow, dim. of blastos, a bud). The
processes which carry the reproductive receptacles, or "gonophores," is
many of the Hydrozoa.
GONOCALYX (Gr. yonos; and kalux, cup). The swimming-bell in a medusiform
gonophore, or the same structure in a gonophore which is not detached.
GONOPH{ORE (Gr. goyeos; and phero, I carry). The generative buds, or receptacles of the reproductive elements, in the Hydrozoa, whether these become
detached or not.
GONOSOME (Gr. gones; and soma, body). Applied as a collective term to the
reproductive zoiids of a Hydrozoin.
GONOTHECA (Gr. genos; and theke, a case). The chitinous receptacle within
which the gonophores of certain of the Hydrozoa are produced.
GRALLATORES (Lat. grallm, stilts). The order of the long-legged Wading Birds.
GRANIVORO US (Lat. g#ra~num, a grain or seed; vore, I devour). Living upon
grains or other seeds.
GRAPTOLLT1DA, (Gr. gra2jho, I write; litiws, stone). An extinct sub-class of
the lH?drozo(0.
GREAR.tlINIDA (Lat. greyarius, occurring in numbers together). A class of the
Protozoa.
GUARD. The cylindrical fibrous sheath with which the internal chamberQd
shell (phragmnacone) of a Belemnite is protected.
GYMNOL2EMATA (Gr. yumnos, naked; laimos, the throat). An order of the
Polyzoa in which the mouth is devoid of the valvular structure known as
the "epistome."
GYMNOPHIONA (Gr. gumnos, naked; ophis, a snake). The order of the Amphibia comprising the snake-like Ccecilice.
GYMNOPHTHALMATA (Gr. gumnos; and opkthalmos, the eye). Applied by Edward Forbes to those Medusa in which the eye-specks at the margin of the
disc are unprotected. The division is now abandoned.
GYMNOSOMATA (Gr. gumnos; and soma, the body). The order of Pteropoda in
which the body is not protected by a shell.
GYNOPHORES (Gr. gEne, woman; phero, I carry). The generative buds, or
gonophores, of Hydrozoa, which contain ova alone, and differ in form from
those which contain spermatozoa.
GYRENCEPHALA (Gr. guroo, I wind about; egkephalos, brain). Applied by
Owen to a section of the Mammlalia in which the cerebral hemispheres are
abundantly convoluted.
HIAMAL (Gr. haima, blood). Connected with the blood-vessels, or with the
circulatory system.
HEMATOCRYA (Gr. haima, blood; cruos, cold).  Applied by Owen to the
" cold-blooded" Vertebrates-viz., the Fishes, Amphibia, and Reptiles.
HILEMATOTHERMA (Gr. haima, blood; thermos, warm). Applied by Owen to
the "warm-blooded" Vertebrates-viz., Birds and Mammals.
HAX,LLlX (Lat. allex, the thumb or great toe).  The innermost of the fiy




634                          GLOSSARY.
digits which normally compose the hind foot of a Vertebrate animal. In
man, the great toe.
HALTERES (Gr. halteres, weights used by athletes to steady themselves in
leaping). The rudimentary filaments or "balancers" which represent the
posterior pair of wings in the Dipterca, an order of Insects.
HAUSTELL.TE (Lat. haurio, I drink). Adapted for sucking or pumping up
fluids; applied to the mouth of certain Crvmstacea and ln.secta.
[HECTOCOTYLUS (Gr. hekaton, a hundred; kothlos, a cup).  The metamorphosed reproductive arm  of certain of the male Cuttle-fishes.  In the
Argonaut the arm  becomes detached, and was originally described as a
parasitic worm.
IIELMIrTHOID  (Gr. helrzins, an intestinal worm).  Worm-shaped, vermiform.
HEMELYTRA (Gr. hemni, half; electron, a sheath). The wings of certain Insects,
in which the apex of the wing is membranous, whilst the inner portion is
chitinous, and resembles the elytron of a beetle.
HEMIMsETABOLIC (Gr. hedi, half; metlabole, change).  Applied to those Insects
which undergo an incomplete metamorphosis.
HErMIPTERA (Gr. henmi; and pteron, wing). An order of Insects in which the
anterior wings are sometimes " hemelytra. "
HERMAPHRODITE (Gr. Hermes, Mercury; Aphrodite, Venus). Possessing the
characters of both sexes combined.
H ETEROCERCAL (Gr. heteros, diverse; kerkos, tail).  Applied to the tail of
Fishes when it is unsymmetrical, or composed of two unequal lobes.
IIETEROGANGLIATE (Gr. heteros, diverse; gtggylion, a knot).  Possessing a
nervous system in which the ganglia are scattered and unsymmetrical (as
in the Molllusca. fur example).
HETEROMORPHIC (Gr. heteros; mlorphe, form). Differing in form or shape.
HETEROPHAGI (Gr. heteros, other; pl/ato, I eat). Applied to Birds the young
of which are born in a helpless condition, and require to be fed by the
parents for a longer or shorter period.
HEXAPOD (Gr. hexa, six; pous, foot). Possessing six legs; applied to the
Insecta.
HILTUM (Lat. hilzmn, a little thing). A small aperture (as in the gemmules of
sponges), or a small depression (as in Nloctliuca).
HIRUDINEA (Lat. hAirado, a horse-leech). The order of Annelida comprising
the Leeches.
HISTOLOGY (Gr. histos, a web; logos, a discourse). The study of the tissues;
more especially of the minuter elements of the body.
HOLOCEPHALI (Gr. holes, whole; kephale, head). A sub-order of the Elacsmobranckii comprising the C(hinzerw.
EIOLOMETABOLIC (Gr. holos, whole; metabole, change).  Applied to Insects
which undergo a complete metamorphosis.
HOLOSTOMATA (Gr. holos, whole; stoma, mouth).  A division of Gasteropodoas
iotlluscs, in which the aperture of the shell is rounded, or "entire."
HOLOTHULROIDEA (Gr. holothotriosn; and eidos, form). An order of Echinoder.
mnatc comprising the Trepangs.
HOsMOCERCAL (Gr. homos, same; kerkos, tail). Applied to the tail of Fishes
when it is symmetrical, or composed of two equal lobes.
HOMOGANGLIATE (Gr. honsos, like; gagglion, a knot).  Having a nervous system in which the ganglia are symmetrically arranged (as in the Annulosa
for example).
HOMOLOGOUS (Gr. homos; and logos, a discourse). Applied to parts which
are constructed upon the same fundamental plan.
HoMoMoRPHOUS (Gr. homos; and morp/te, foerm). Having a similar external
appearance or form.
HUMERUS. The bone of the upper arm (brachizsm) ill the Vertebrates.
HYALINE (Gr. hualos, crystal). Crystalline or glassy.
HYDATIDS (Gr. hudatis, a vesicle). The vesicle containing the larval forms
(Echinococci) of the tapeworm of the dog.
HYDRAFORM. Resembling the common fresh-water polype (Hldala) in fornl.




GLOSSARY.                              635
HYDROCAULUS (Gr. hudra, a water-serpent; and kaulos, a stem).  The main
stem of the ccenosarc of a Hydrozo6a.
HYDROCYSTS (Gr. hudra; and kustis, a cyst).  Curious processes attached to
the ccenosarc of the PhIysolo wrid e, and termed "feelers" (fiihler and taster
of the Germans).
HYDR(ECIUM (Gr. hudra; and oikos, a house). The chamber into which the
cenosarc in many of the Calycophoridce can be retracted.
HYDROrDA (Gr. hudra; and eidox, form).  The sub-class of the llydrozoa,
which comprises the animals most nearly allied to the Hydra.
HYDROPE1YLLIa (Gr. hudra; and phyllon, a leaf).  Overlapping appendages
or plates which protect the polypites in some of the oceanic Ilydrozoa
(Calycophiorid  and Plhysophoridce). They are often termed "bracts," and
are the " deck.tiickee" of the Germans.
HYDRORHIZA (Gr. hAdra; and rhiza, root). The adherent base or proximal
extremity of any Hydrozodn.
HYDROSOMA (Gr. hudra; and soma, body).  The entire organism  of -any
lHydrozoan.
HYDROTHECA (Gr. A.udra; and theke, a case).  The little chitinous cups in
which the polypites of the Sertularida and C'ampanularida are protected.
HY.DRoZOA (Gr. hudra; and zo6n, animal).  The class of the Coelenterata,
which comprises animals constructed after the type of the Hydra.
HYMENOPTEPRA (Gr. ]h~umen, a membrane; pteron, a wing). An order of Insects (comprising Bees, Ants, &c.) characterised by the posscssion of four
membranous wings.
HYOID (Gr. U; eidos, form).  The bone which supports the tongue in Vertebrates, and derives its name from its resemblance in man to the Greek
letter U.
HYPOSTOME (Gr. hupo, under; stoma, mouth). The upper lip, or " labrum,"
of certain Crustacea (e.g., T'rilobites).
HYRACUIDEA (Gr. hurax, a shrew; eidos, form).  An order of the laXamaliac
constituted for the reception of the single genus Jlyrax.
ICHTHYODORULITE (Gr. ichthus, fish; dorus, spear; litios, stone).  The fossil
fin-spines of Fishes.
ICHTHYOMORPHA (Gr. ichthus; morphe, shape).  An order of Amphibians,
often called Urodela, comprising the fish-like Newts, &c.
ICHITHYOPHTHIRA (Gr. ichthlus; phl/heir, a louse). An order of Cr stacea comprising animals which are parasitic upon Fishes.
IcHTHYOPSlDA (Gr. ichthus; opsis, appearance).  The primary division of
Vertebrala, comprising the Fishes and Amphibia.  Often spoken of as the
Branchiate Vertebrata.
ICHTHYOPTERYGIA (Gr. ichthus; pterux, wing). An extinct order of Reptiles.
ICHTHYOSAURIA (Gr. ichtlius; saura, lizard). Synonymous with Icht/hqo)f(eryyqia.
ILIUM. The haunch-bone, one of the bones of the pelvic arch in the higher
Vertebrates.
IMAGO (Lat. an image or apparition).  The perfect insect, after it has undergone its metamorphoses.
IMBRICATED. Applied to scales or plates which overlap one another like tiles.
INCISOR (Lat. incido, I cut). The cutting teeth fixed in the intermaxillary
bones of the Maeimalia, and the corresponding teeth in the lower jaw.
INEQUILATERAL. Having the two sides unequal, as in the case of the shells
of the ordinary bivalves (Lamellibranchiata). When applied to the shells
of the Foraminz7fera, it implies that the convolutions of the shell do not lie
in the same plane, but are obliquely wound round an axis.
INEQUIVALVE. Composed of two unequal pieces or valves.
INFUNDIBULUM (Lat. for funnel).  The tube formed by the coalescence or
apposition of the epipodia in the Cephalopoda- — commonly termed tle
" funnel," or'" siphon."
INFUSORIA (Lat. infusumn, an infusion).  A class of Protozoa, so called be.
cause they are often developed in organic infusions.
INGUINAL (Lat. inqguen, groin). Connected with, or situated upon, the groin.




636                          GLOSSARY.
INOPERCULATA (Lat. in, without; operculeum, a lid).  The division of p].
monate Gasteropoda in which there is no shelly or horny plate (operculum)
by which the shell is closed when the animal is withdrawn within it.
INSECTA (Lat. inseco, I cut into). The class of Articulate animals commonly
known as Insects.
INSECTIVORA (Lat. insectun, an insect; voro, I devour). An order of Mammals.
INSECTIVOROUS. Living upor. Insects.
INSESSORES (Lat. insedeo, I sit upon). The order of the Perching Birds, often
called Passeres.
INTERAMBULACRA. The rows of plates in an Echinoderm which are not perforated for the emission of the "tube-feet."
[NTERMAXILLAE, or PREMAXILL,E. The two bones which are situated between
the two superior maxillhe in Vertebrata. In man, and some monkeys, the pr emaxillie anchylose with the maxillee, so as to be irrecognisable in the adult.
INTUSSUSCEPTION (Lat. intots, within; suscipio, I take up). The act of taking
foreign matter into a living being.
INVERTEBRATA (Lat. in, without; vertebra, a bone of the back). Animals
without a spinal column or backbone.
ISCHIUM (Gr. iseltioe,, the hip). One of the bones of the pelvic arch in Vertebrates.
ISOPODA (Gr. isos, equal; podes, feet).  An order of Crustacca in which the
feet are like one another and equal.
JUGULAR (Lat. juyglun, the throat).  Connected with, or placed upon, the
throat. Applied to the ventral fins of fishes when they are placed beneath
or in advance of the pectorals.
KXINcZOIC (Gr. kaccnos, recent; zoe, life).  The Tertiary period in Geology,
comprising those formations in which the organic remains approximate
more or less closely to the existing fauna and flora.
KERATODE (Gr. keras, horn; eidos, form). The horny substance of which the
skeleton of many sponges is made up.
KERATOSA. The division of Sponges in which the skeleton is composed of
keratode.
LABIUM (Lat. for lip). Restricted to the lower lip of Articulate animals.
LABRUM (Lat. for lip). Restricted to the upper lip of Articulate animals.
LABYRINTHODONTIA (Gr. lalbyri nthos, a labyrinth; odous, tooth).  An extinct
order of Amphlibia, so called from the complex microscopic structure of
the teeth.
L.CERTILIA (Lat. lace)Eta, a lizard).  An order of Reptiliac comprising the
Lizards and Slow-worms.
LEMIODIPODA (Gr. laitos, throat; dis, twice; podes,.feet). An order of Crus,
tacea, so called because they have two feet placed far forwards, as it were
under the throat.
LAMELLIBRANCHIATA (Lat. lamella, a plate; Gr. brarlchia, gill). The class of
Jlollesca, comp,rising the ordinary bivalves, characterised by the possession
of lamellar gills.
LAMELLIROSTRES (Lat. lamella, a plate; rostrum, beak).   The flat-billed
Swimming Birds (Natatores), such as Ducks, Geese, Swans, &c.
LARVA (Lat. a mask). The insect in its first stage after its emergence from
the egg, when it is usually very different from the adult.
LARYNX. The upper part of the windpipe, forming a cavity with appropriate
muscles and cartilages, situated beneath the hyoid bone, and concerned in
Manmmals in the production of vocal sounds.
LENTICULAR (Lat. lens, a bean). Shaped like a biconvex lens.
LEPIDOPTERA (Gr. lepis, a scale; pteron, a wing). An order of Insects, comprising Butterflies and Moths, characterised by possessing four wings which
are usually covered with minute scales.
LEPIDOTA (Gr. lepis, a scale).  Formerly applied to the order Dipsoi, con.
taining the Mud-fishes (Lepidosireat).




GLOSSARY.                            637
LEPTOCARDIIA (Gr. leptos, slender, small; cardia, heart). The name given by
Muller to the order of Fishes comprising the Lancelet, now called Pharyngobranch/ii.
LIGAMENTUM NUCHA3 (Lat. nucha, the nape of the neck). The band of elastic
fibres by which the weight of the head in Mammalia is supported.
LINGUAL (Lat. libqua, the tongue). Connected with the tongue.
LINGULA (Lat. liulta, a little tongue).  The upper flexible portion of the
labium or lower lip in Insects.
LiSSENCEPHALA (Gr. liesos, smooth; eykephalos, brain). A primary division
of Mlanmmalia, according to Owen, in which the cerebral hemispheres are
smooth or have few convolutions.
LITHOCYSTS (Gr. lithos, a stone; kustis, a cyst). The sense-organs or "marginal bodies" of the Lcernarida or Steganophthalnmate AMedusce.
LONGIPENNATE (Lat. longus, long; penna, wing). A group of the Natatorial
Birds.
LONGIROSTRES (Lat. longus; rostrumc, beak). A group of the Wading Birds.
LOPHOPHUORE (Gr. lophos, a crest; and pheero, I carry). The disc or stage upon
which the tentacles of the Poltyzoa are borne.
LOPHYROPODA (Gr. lopozuros, having stiff hairs; and peodes, feet).  An order
of C(rustacea.
LOaRCA (Lat. a breast-plate).  Applied to the protective case with which
certain Infusoria are provided.
LORICATA (Lat. lomrca, a cuirass).  The division of Reptiles comprising the
C'lielonia and C6roco(il/ia, in which bony plates are developed in theskin (de rma).
LIJUCENARIDA (Lat. lcernea, a lamp). An order of the Ilydrozoa.
LUMBAR (Lat. lumbus, loin). Connected with the loins.
LUNATE (Lat. luna, moon). Crescentic in shape.
LYENCEPHALA (Gr. luo, I loose; egke2p/alos, brain).  A primary division of
Mammals, according to Owen.
MACRODACTYLI (Gr. makros, long; dakttulos, a finger). A group of the Wading Birds.
MACRURIA (Gr. mza1ros, long; oura, tail).  A tribe of Decapod Crustaceans
with long tails (e.g., the Lobster, Shrimp, &c.)
MADREPORIFORM. Perforated with small holes, like a coral; applied to the
tubercle by which the ambulacral system of the LEchinoderms mostly communicates with the exterior.
MALACOSTRACA (Gr. mnalakos, soft'; ostrakon, shell). A division of Crustacea.
Originally applied by Aristotle to the entire class Crustacea, because their
shells were softer than those of the Mollusca.
MALLOPHAGA (Gr.  mallos, a fleece; phayo, I eat). An order of Insects which
are mostly parasitic upon birds.
MAMMALIA (Lat. mamma, the breast). The class of Vertebrate animals which
suckle their young.
MANDIBLE (Lat. maneditnlnm, a jaw).  The upper pair of jaws in Insects;
also applied to one of the pairs of jaws in Crustacea and Spiders, to the beak
of Cephalopods, the lower jaw of Vertebrates, &c.
MANTLE. The external integument of most of the Molluscsa, which is largely
developed, and forms a cloak in which the viscera are protected. Technically called the " pallium."
MANUBRIUM (Lat. a handle). The polypite which is suspended from the roof
of the swimming-bell of a Mledusa, or from the gonocalyx of a medusiform
gonophore amongst the Hydrozoa.
MANUS (Lat. the hand). The hand of the higher Vertebrates.
MxARsIPoBRANCHII (Cr. ztar-sipos, a pouch; bragchia, gill).  The order of
Fishes comprising the Hag-fishes and Lampreys, with pouch-like gills.
MARSUPIALIA (Lat. marsvpiumc, a pouch). An order of Mammals in which the
females mostly have an abdominal pouch in which the young are carried.
MASTAX (Gr. mouth). The muscular pharynx or " buccal funnel" into which
the mouth opens in most of the Rotifera.
M.STI'cATonR (Lat. maedtico, I chesw). Applied to parts adapted for chewing.




638                          GLOSSARY.
MAXILL3 (Lat. jaws). The inferior pair or pairs of jaws in the' rlEool;eoda
(Insects, Crustacea, &c.) The upper jaw-bones of Vertebrates.
MAXILLIPEDES (Lat. maxillce, jaws; pes, the foot). The limbs in Crustacees
and Myriapoda which are converted into masticatory organs, and are cornmonly called " foot-jaws."
MEDULLA (Lat. marrow). Applied to the mfarrow of bones, or to the spinal
cord, with or without the adjective " spinalis."
MEDUS.E.  An order of Hydrozoa, commonly known as Jelly-fishes (Disco_phora, or Acaleplce), so called because of the resemblance of their tentacles
to the snaky hair of the Medusa. Many Medusce are now known to be
merely the gonophores of Hydrozoa.
MEDUSIFORM.  Resembling a Medusa in shape.
MEDUSOID. Like a Medusa; used substantively to designate the medusiform
gonophores of the Hqdrozoa.
MEMBRANA NICTrTANS (Lat. nicto, I wink). The third eyelid of Birds, &c.
MENTUM (Lat. the chin). The basal portion of the labium or lower lip in
Insects.
MIEROSTOMATA (Gr.,eiron, thigh; stoma, mouth). An order of Crustacea in
which the appendages which are placed round the mouth, and which officiate as jaws, have their free extremities developed into walking or prehensile organs.'1MESENTERIES (Gr. mesos, intermediate; enteron, intestine).  In a restricted
sense, the vertical plates which divide the somatic cavity of a Sea-anemone
(Actinia) into chambers.
MESOPODIUM (Gr. mesos, middle; poeas, foot). The middle portion of the
" foot" of Molluscs.
MESOSTERNUM  (Gr. mesos, intermediate; sternon, the breast-bone).  The
middle portion of the sternum, intervening between the attachment of the
second pair of ribs and the xiphoid cartilage (xiphisterntum).
MESOTHORAX (Gr. mesos; and thorax, the chest). The middle ring of the
thorax in Insects.
MESOZOIC (Gr. roesos; and zoe, life). The Secondary period in Geology.
METACARPUS (Gr. meta, after;. karpos, the wrist). The bones which form the
" root of the hand," and intervene between the wrist and the fingers.
METAMORPHOSIS (Gr. meta, implying change; morphe, shape). The changes
of form which certain animals undergo in passing from their younger to
their fully-grown condition.
METAPODIUM (Gr. meta, after; poes, the foot).  The posterior lobe of the
foot in Mollusca; often called the " operculigerous lobe," because it develops the operculum when this structure is present.
METASTOMA (Gr. meta, after; stonma, mouth).  The plate which closes the
mouth posteriorly in the Crustacea.
METATARSUS (Gr. meta, after; tarsos, the instep).  The bones which intervene between the bones of the ankle (tarsus) and the digits in the hind-foot
of the higher Vertebrates.
METATHORAX (Gr. meta, after; thorax, the chest). The posterior ring of the
thorax in Insects.
MIMErTrI (Gr. mimetikos, imitative).  Applied to organs or animals which resemble each other in external appearance, but not in essential structure.
MOLARS (Lat. mola, a mill). The " grinders " in man, or the teeth in diphyodont Mammals which are not preceded by milk-teeth.
MOLLUSCA (Lat. mollis, soft). The sub-kingdom which includes the Shellfish proper, the Pol/yzoa, the Tusoicata, and the Lamp-shells; so called from
the generally soft nature of their bodies.
MOLLUSCOIDA (MIollusca; Gr. eidos, form). The lower division of the Mollusca,
comprising the Polyzoa, Tunicata, and Bracs.iopoda.
MONRADS (Gr. meons, unity).  Microscopical organisms of an extremely
simple character, developed in organic infusions.
M'[oNoCULOUS. Possessed of only one eye.
MOINODELrPHA (Gr. monos, single; dell)les, womb). The division of lcz mm alia
in which the uterus is single.




GLOSSARY.                              639
MONC:ECTous (Gr. monos, single; oikos, house).  Applied to individuals in
which the sexes are united.
MONOMYARY (Gr. menoos, single; muon, muscle). Applied to those bivalves
(Lamellibranchiata) in which the shell is closed by a single adductor muscle).
MONOPHYODONT (Gr. mnoos; phuo, I generate; odous, tooth).  Applied to
those Mammals in which only a single set of teeth is ever developed.
MONOTHALAMOUS (Gr. montos; and thalamsos, chamber).  Possessing only a
single chamber. Applied to the shells of Foraminifera and Alollusca.
MONOTREMATA (Gr. 9zonos; trema, aperture).  The order of Malnmals comprising the Duck-mole and Echidna, in which the intestinal canal opens
into a " cloaca" common to the ducts of the urinary and generative organs.
MULTILOCULAR (Lat. multus, many; locclus, a little purse).  Divided into
many chambers.
MULTIVALVE. Applied to shells which are composed of many pieces.
MULTUNGULA (Lat. multus, many; ungula, hoof).  The division of Perissodactyle Ungulates, in which each foot has more than a single hoof.
MYELON (Gr. muelos, marrow). The spinal cord of Vertebrates.
MYRIAPODA (Gr. munrios, ten thousand; podes, feet). A class of A rthlropoda
comprising the Centipedes and their allies, characterised by their numerous
feet.
NACREOUS (Fr. nacre, mother-of-pearl, originally Oriental).  Pearly; of the
texture of mother-of-pearl.
NATATORES (Lat. nare, to swim). The order of the Swimming Birds.
NATATORY (Lat. nare, to swim). Formed for swimming.
NAUTILOID.  Resembling the shell of the Nautilus in shape.
NECTOCALYX (Gr. necho, I swim; kalux, cup). The swimming-bell or "disc"
of a AIedusa or Jelly-fish.
NEMATELMIA (Gr. nema, thread; helmins, a worm).  The division of Scolecida
comprising the Round-worms, Thread-worms, &c.
NEMATOCYSTS (Gr. enema, thread; kustis, a bag).  The thread-cells of the
Coelenterata.  (See Cnidae.)
NEMATOIDEA (Gr. nzenza, thread; eidos, form). An order of Scolecida comprising the Thread-worms, Vinegar-eels, &c.
NEMATOPHORES (Gr. nema, thread; phero, I carry).  Cwecal processes foun(d
on the ccenosare of certain of the Sertularida, containing numerous threadcells at their extremities.
NEMERTIDA (Gr. JNev7ertes, proper name).  A division of the Tusrbellariat
WIornes, commonly called " Ribbon-worms."
NERVURES (Lat. ne-rvus, a sinew). The ribs which support the membranous
wings of insects.
NF,URAL (Gr. neuron, a nerve).  Connected with the nervous system.
N'XURAPOPHYSIS (Gr. neurob2,  a nerve; apophzlsis, a projecting part).  The
" spinous process" of a vertebra, or the process formed at the point of
junction of the neural arches.
NEUROPODIUM (Gr. neuroon, a nerve; poets, the foot). The ventral or inferior
division of the "foot tubercle" of an A nnelide; often called the "ventral
oar. "
NEUROPTERA (Gr. neuronl; and pferon, a wing). An order of Insects characterised by four membranous wings with numerous reticulated nervures
(e.g., Dragon-flies).
N]UTvIR (Lat. neither the one nor the other). Having no fully-developed sex.
NInIFICATION (Lat. nid es, a nest; facio, I make). The building of a nest.
NOCTURNAL (Lat. nox, night).  Applied to animals which are active by night.
NOR.MAL (Lat. norman, a rule).  Conforming to the ordinary standard.
NOTOBRANCHIATA (Gr. wotos, the back; and bl;aychia, gill).  Carrying the
gills upon the back; applied to a division of the A nnelidn.
NOTOCHORD (Gr. notos, back; chorde, string).  A cellular rod which is developed in the embryo of Vertebrates immediately beneath the spyinal cord,
and which is -usually replaced in the adult by the vertebral column.  Often
it is spoken of as the " chorda dorsalis."




640                          GLOSSARY.
NOTOPODIUM (Or. notes, the back; and peots, the foot). The dorsal division
of one of the foot-tubercles or parapodia of an Annielide; often called the
", dorsal oar."
NUCLEATED. Possessing a nucleus or central particle.
NUCLEOLUS.  1. The minute solid particle in the interior of the nucleus of
some cells. 2. The minute spherical particle attached to the exterior of
the  "nucleus," or ovary, of certain Infusoria, performing the functions of
a testicle.
NUCLEUS (Lat. nucleus, a kernel). l- The solid or vesicular body found in
many cells. 2. The solid rod, or band-shaped body, found in the interior
of many of the Protozoa, and having, in certain of them, the fiunctions of
an ovary.  3. The "madreporiform tubercle" of the ]Echinodervzata. 4.
The embryonic shell which is retained to form the apex of the adult shell
in many of the Mollusca.
NUDIBBRANCHIATA (Lat. nudtus, naked; and Or. brgeCtcia, gill). An order of
the Gasteropoda in which the gills are naked.
NYMPHS. The active pupae of certain Insects.
OCCIPITAL. Connected with the orcirnt, or the back part of the head.
OCEANIc. Applied to animals which inhabit the open ocean (- pelagic).
OCELLI (Lat. diminutive of oculu.s, eye). The simple eyes of many Echinoderms, Spiders, Crustaceans, Mollulscs, &c.
OCTOPODA (Gr. octo, eight; poes, foot). The tribe of Cuttle-fishes with eight
arms attached to the head.
ODONTOCETI (Gr. odous, tooth; ketos, whale!.  The "toothed" Whales, in
contradlistinction to the "whalebone" Whales.
ODONTOID (Gr. odous; eidos, form). The " odontoid process" is the centrum
or body of the first cervical vertebra (atlas). It is detached from the atlas,
and is usually anchylosed with the second cervical vertebra (axis), and it
forms the pivot upon which the head rotates.
ODONToPHORE (Gr. odous, tooth; phero, I carry). The so-called "tongue"
or masticatory apparatus of Gasteropoda, Pteropoda, and Cephaloepoda.
(ESOPHAGUS. The gullet or tube leading from the mouth to the stomach.
OLcGOCEHETA (Gr. o/i.os, few; chaite, hair). An order of. Annelida, comprising the Earth-worms, in which there are few bristles.
OMASUM (Lat. bullock's tripe). The third stomach of Ruminants, commonly
called the psalteriunt, or many-plies.
OMNIvOROUS (Lat. omeaia, everything; yore, I devour). Feeding indiscriminately upon all sorts of food.
OPERCULATA (Lat. operculum, a lid). A division of pulmonate Gasteropoda,
in which the shell is closed by an operculum.
OPERCULUM. A horny or shelly plate developed'in certain -lollltsca upon
the hinder part of the foot, anti serving to close the aperture of the shell
when the animal is retracted within it; also the lid of the shell of a Balanus or Acorn-shell; also the chain of flat bones which cover the gills in
many fishes.
OPHIDIA (Gr. ophis, a serpent). The orderof Reptiles comprising the Snakes.
OPHIDOBATRACHIA (Gr. ophis; batrachos, a frog).  Sometimes applied to the
order of Snake-like Amphibians comprising the Cceciliae.
OPHIOMORPHA (Gr. ophis; morphe, shape). The order of Amphibia comprising the Caccilice.
OPHIuRoIDEA (Gr. ophis, snake; oura, tail; eidos, form). An order of Echinmodermata comprising the Brittle-stars and Sand-stars.
OPISTnOBRANCHIATA (Gr. opisthen, behind; bragchia, gill).  A division of
Gasteropoda in which the gills are placed on the posterior part of the
body.
OPISTHOC(ELOUS (Gr. opisthen, behind; koilos, hollow). Applied to vertebrae,
the bodies of which are hollow or concave behind.
ORAL (Lat. os, mouth). Connected with the mouth.
ORNITHODELPHIA (Gr. ornis, a bird; delphus, womb). The primary division
of Mammals comprising the lionotrefieata.




GLOSSARY.                            641
ORTHOrrlmRs (Gr. orthos, straight; pterol, wing). * An order of Insects.
OSCULA (Lat. diminutive of os, mouth). 1. The large apertures by which a
sponge is perforated (" exhalant apertures "). 2. The suckers with which
the Teeniada (Tape-worms and Cystic Worms) are provided.
OSSICULA (Lat. diminutive of os, bone). Literally small bones. Often used
to designate any hard structures of small size, such as the calcareous plates
in the integument of the Star-fishes.
OSTRACODA (Gr. ostrakon, a shell). An order of small Crustaceans which
are enclosed in bivalve shells.
OTOLITHS (Gr. ous, ear; and lithos, stone). The calcareous bodies connected
with the sense of hearing, even in its most rudimentary form.
OVARIAN VESICLES or CAPSULES. The generative buds of the Sertularida.
OVARY (OvARlUM). The organ by which ova are produced.
OVIPAROUS (Lat. ovum, an egg; and pario, I bring forth). Applied to animals
which bring forth eggs, in contradistinction to those which bring forth their
young alive,
OVIPOSITOR (Lat. ovum; and pone, I place). The organ possessed by some insects, by means of which the eggs are placed in a position suitable for their
development.
OvIsAc. The external bag or sac in which certain of the Invertebrates carry
their eggs after they are extruded from the body.
OVOVIVIPAROUS (Lat. ovum, egg; vivus, alive; pario, I produce). Applied
to animals which retain their eggs within the body until they are hatched.
OVUM (Lat. an egg). The germ produced within the ovary, and capable
under certain conditions of being developed into a new individual.
PACHYDERMATA (Gr. pachus, thick; derma, skin). An old Mammalian order
constituted by Cuvier for the reception of the Rhinoceros, Hippopotamus,
Elephant, &c.
PALEONTOLOGY (Gr. palalos, ancient; and logos, discourse). The science of
fossil remains or of extinct organised beings.
PALaEOZOiC (Gr. palaios, ancient; and zoe, life). Applied to the oldest of the
great geological epochs.
PALLIOBRAINCHIATA (Lat. palliunm; andGr. bragchin, gill). An old name for
the Brachiopoda, founded upon the belief that the system of tubes in the
mantle constituted the gills.
PALLIUM (Lat. pallium, a cloak). The mantle of the Mollusca. Pallial: relating to the mantle. Pallial lie or impression; the line left in the dead
shell by the muscular margin of the mantle. Pallial shell; a shell which is
secreted by, or contained within, the mantle, such as the "'bone" of the
Cuttle-fishes.
PALPI (Lat. palpo, I touch). Processes supposed to be organs of touch, developed from certain of the oral appendages in Insects, Spiders, and Crustacea, and from the sides of the mouth in the Acephalous Molluscs.
PAPILLA (Lat. for nipple). A minute soft prominence.
PARAPODIA (Gr. para, beside; podes, feet). The unarticulated lateral locomotive processes or " foot-tubercles " of many of the Annelida.
PARIETAL (Lat. paries, a wall). Connected with the walls of a cavity or of
the body.
PARIETOSPLANCHNIC (Lat. paries; Gr. splaychna, viscera). Applied to one
of the nervous ganglia of the Molletsca, which supplies the walls of the body
and the viscera.
PARTHENOGENESIS (Gr. parthenos, a virgin; and gignomai, to be born).
Strictly speaking, confined to the production of new individuals from virgin
females by means of ova without the intervention of a male. Sometimes
used also to designate asexual reproduction by gemmation or fission.
PATAGIUM (Lat. the border of a dress). Applied to the expansion of the integument by which Bats, Flying Squirrels, and other animals support themselves in the air.
PATELLA. The knee-cap or knee-pan. A sesamoid bone developed in the
tendon of insertion of the great extensor muscles of the thigh.




642                          GLOSSARY.
PECTINATE (Lat. pecten, a comb). Comb-like; applied to the gills of certain
Gasteropods; hence called Pectinibranchiata.
PECTORAL (Lat. pectuEs, chest). Connected with, or placed upon, the chest.
PERENNIBmRANCHIATA (Lat. perennis, perpetual; Gr. bragclhia, gill). Applied
to those A4 pmhibia in which the gills are permanently retained throughout
life.
PEDAL (Lat. pes, the foot). Connected with the foot of Mollusca.
PEDICELI.ARITA (Lat. pedicellts, a louse). Certain singular appendages found
in mnany Echinoderms, attached to the surface of the body, and resembling
a little beak or forceps supported on a stalk.
PEDICLE (Lat. dim of pes, the foot). A little stem.
PEDIPALPI (Lat. pes, foot; and palpo, I feel). An order of Arachnida comprising the Scorpions, &c.
PEDUNCLE (Lat. pecltnceuls, a stem or stalk).  In a restricted sense applied
to the muscular process by which certain Breachioipods are attached, and to
the stem which bears the body (capitulum) in Barnacles.
PEDUNCULATE. Possessing a peduncle.
PELAGIC (Gr. pelaqos, sea). Inhabiting the open ocean.
PELVIS (Lat. for basin). Applied, from analogy, to the basal portion of the
cup (calyx) of Cri~noids. The bony arch with which the hind-limbs are connected in Vertebrates.
PERGAMENTACEOUS (Lat. pergamena, parchment). Of the texture of parchment.
PERICARDIUM (Gr. peri, around; kardia, heart).  The serous membrane in
which the heart is contained.
PERIDERM (Gr. peri, around; and derma, skin).  The hard cuticular layer
which is developed by the cosnosare of certain of the Hygdrozoa.
PERIGASTRIC (Gr. peri, around; and gaster, stomach).  The perigastric space
is the cavity which surrounds the stomach and other viscera, corresponding
to the abdominal cavity of the higher animals.
PERIOSTRACUM (Gr. peri; and ostr akon, shell). The layer of epidermis which'covers the shell in most of the Mollusca.
PERIPLAST (Gr. peri; and plasso, I mould).  The intercellular substance or
matrix in which the organised structures of a tissue are embedded.
PERISOME (Gr. peri; and soria, body). The coriaceous or calcareous integument of the Echinodernzata.
PERISSODACTYLA (Gr. perissos, uneven; da/ttlos, finoer).  Applied to those
Hoofed Quadrupeds (Un'ulata) in which the feet have an uneven number
of toes.
PERISTOME (Gr. peri; and stoma, mouth). The space which intervenes between the mouth and the margin of the calyx in Vorticella; also the space
between the month and the tentacles in a sea-anemone (ActilLia); also
the lip or margin of the mouth of a univalve shell.
PERIVISCERAL (Gr. peri; and Lat. viscera, the internal organs). Applied to
the space surrounding the viscera.
PETALOID. Shaped like the petal of a flower.
PHALANGES (Gr. phalanx, a row). The small bones composing the digits of
the higher Vertebrata. Normally each digit has three phalanges.
PHARYNGOBRANCHII (Gr. pharugx, pharynx; bragchia, gill). The order of
Fishes comprising only the Lancelet.
PHARYNX. The dilated commencement of the gullet.
PHRAGMACONE (Gr. phragma, a partition; and konos, a-cone). The chambered
portion of the internal shell of a Belemnite.
PHYLACTOLEMATA (Gr. phulass, I guard; and lainmos, throat). The division
of Polyzoa in which the mouth is provided with the arched valvular process
known as the "epistome."
PHYLLOCYSTS (Gr. phullon, leaf; and kustis, a cyst). The cavities in the interior of the " hydrophyllia " of certain of the Oceanic Ilydrozon.
PHYLLOPODA (Gr. phullon, leaf; and poens, foot). An order of (Crestacea.
PHYOGEMMARIA (Gr. phtuo, I produce; and Lat. genoma, bud). The small
gonoblastidia of VFeella, one of the Physophoridee.
PHYSOGRADA (Gr. phnsa, bellows or air-bladder; and Lat. gradioni, I walk),




GLOSSARY.                             643
Applied formerly to the PhysophoridYe, an order of Oceanic Hydrozoa, in
which a "float" is present.
PHYSOPHORIDAE (Gr. phuzsa, air-bladder; and phei'o, I carry). An order of
Oceanic Hydrozoa.
PHYTOID (Gr. phuton, a plant; and eidos, form). Plant-like.
PHYTOPHAGOUS (Gr. phuton, a plant; and phago, I eat).  Plant-eating, or
herbivorous.
PINNATE (Lat. pinna, a feather). Feather-shaped, or possessing lateral processes.
PINNIGRADA (Lat. pinna, a feather; gradior, I walk). The group of Carnivorea, comprising the Seals and Walruses, adapted for an aquatic life. Often
called Pinuzipedia.
PINNULA (Lat. dim. of pinn[za). The lateral processes of the arms of Crinoids.
PIscES (Lat. piscis, a fish). The class of Vertebrates comprising the Fishes.
PLACENTA (Lat. a cake). The " after-birth," or the organ by which a vascular connection is established in the higher Manmalia between the mother
and the fwetus.
PLACENTAL. Possessing a placenta, or connected with the placenta.
PLACOID (Gr. plax, a plate; eidos, form).  Applied to the irregular bony
plates, grains,- or spines which -are found in the skin of various fishes
(Elasmlobranchii).
PLAGIOSTOMI (Gr. plagios, transverse; stoma, mouth). The Sharks and Rays,
in which the mouth is transverse, and is placed on the under surface of the
head.
PLANARIDA (Gr. plane, wandering). A sub-order of the Turbellaria.
PLANTIGRADE (Lat. planta, the sole of the foot; gradior, I walk). Applying
the sole of the foot t;o the ground in walking.
PLANULA (Lat. planus, flat). The oval ciliated embryo of certain of the fydr ozoa.
PLASTRON. The lower or ventral portion of the bony case of the Chelonians.
PLATYELMIrA (Gr. platyos, broad; and helmnins, an intestinal worm).  The
division of Scolecicl(t comprising the Tape-worms, &c.
PLATYRiINA (Gr. plafts, broad; rhines, nostrils). A group of the Quadrumana.
PLEURA (Gr. the side). The serous membrane covering the lung in the airbreathing Vertebrates.
PLEURON (Gr. pleuron, a rib). The lateral extensions of the shell of Crustacea.
PLUTEUS (Lat. a pent-house). The larval form of the Echinoidea.
PNEUMATIC (Gr. pneuma, air). Filled with air.
PNEUMATOCYST (Gr. prneeuma, air; and kustis, cyst).  The air-sac or float of
certain of the Oceanic HIydrozoa (Physophoridc).
PNEUMATOPHORE (Gr. pneuma, air; and phero, I carry).  The proximal
dilatation of the coenosarc in the Physophoridce which surrounds the pneumatocyst.
PNEUMOSKELETON (Gr. pneuma; and skeletos, dry).  The hard structures
which are connected with the breathing organs (e.g., the shell of Molluscs).
PODOPHTHALMATA (Gr. penous, foot; and ophthalmos, eye). The division'of
Crustacea in which the eyes are borne at the end of long foot-stalks.
PODOSOMATA (Gr. pous, foot; sonma, body). An order of Areachnida.
POEPHAGA (Gr. poe, grass; phago, I eat). A group of the Marsupials.
POLLEX (Lat. the thumb). The innermost of the five normal digits of the anterior limb of the higher Vertebrates. In man, the thumb.
POLYCYSTINA (Gr. polus, many; and kustis, a cyst). An order of Protozoa,
with foraminated siliceous shells.
POLYGASTRICA (Gr. polus; anti gaster, stomach).  The name applied by
Ehrenberg to the Infusoria, under the belief that they possessed many
stomachs.
POLYPARY. The hard chitinous covering secreted by many of the Hydrozoa.
POLYPE (Gr. polus, many; pous, foot).  Restricted to the single individual of
a simple A ctinozo6n, such as a Sea-anemone, or to the separate zooiids of a
compound Actinozo/6h. Often applied indiscriminately to any of the Coelen.
teerata, or even to the Polyzoa.




644                         GI,OSSARY.
POLYPIDE. The separate zooid of a Polyzorn.
POLYPIDOM. The dermal system of a colony of a Hydrozoln, or Polyzo6n.
POLYPITE. The separlate zoiid of a lydrozo6n.
POLYSTOME (Gr. -polus, many; and stoma, mouth). Having many mouths;
applied to the Acinetce amongst the Protozoa.
POLYTHALAMOUS (Gr. polus; and thalasmos, chamber). Having many chambers; applied to the shells of Foraminifera and Cepehalopoda.
POLYZOA (Gr. poles; and zooir, animal). A division of the Molluscoida, comprising compound animals, such as the Sea-mat. Sometimes called Bryozoa.
POLYZOARIUM. The dermal system of the colony of a Polyzo6n (= Polypidom).
PORCELLANOUB. Of the texture of porcelain.
PORIFERA (Lat. porus, a pore; and fero, I carry). Sometimes used to designate the Foranminifera, or the Spon~ges.
POST-ANAL. Situated behind the anus.
POST-EaSOPHAGEAL. Situated behind the gullet.
POST-ORAL. Situated behind the mouth.
PRLE-MAXILLX. (See Intermaxillae.)
PRXIMOLARS (Lat. prace, before; mnolares, the grinders).  The molar teeth of
Mammals which succeed the molars of the milk-set of teeth. In man, the
bicuspid teeth.
PRAE-CESOPHAGEAL  Situated in front of the gullet.
PHR-STERNUM. The anterior portion of the breast-bone, corresponding with
the maeeubrinm sterni of human anatomy, and extending as far as the ppint
of articulation of the second rib.
PRESSIROSTRES (Lat. pressus, compressed; rostrmn, beak). A group of the
Grallatorial Birds.
PSOBOSCIDEA (Lat. proboscis, the snout). The order of Mammals comprising
the Elephants.
PROBOSCIS (Lat. or Gr. the snout). Applied to the spiral trunk of Lepidopterous Insects, to the projecting mouth of certain Crinoids, and to the central polypite in the Medusse.
PROCCELOUs (Gr. pro, front; koilos, hollow). Applied to vertebrae, the bodies
of which are hollow or concave in front.
PROGLOTTIS (Gr. for the tip of the tongue). The generative segment or joint
of a Tape-worm.
PRO-LEGS. The false abdominal feet of Caterpillars.
PRONATION (Lat. proiues, lying on the face, prone). The act of turning the
palm of the hand downwards.
PROPODIUM (Gr. pro, before; pe.s, foot). The anterior part of the foot in
Molluscs.
PRoscoLEX (Gr. pro, before;: colex, worm). The first embryonic stage of a
Tape-worm.
PROSOBRANCHIATA (Gr. proso, in advance of; braychia, a gill).  A division
of Gasteropodous Molluscs in which the gills are situated in advance of the
heart.
PROSOMA (Gr. pro, befors; soma, body). The anterior part of the body.
PROTHORAX (Gr. pro; and thorax, chest). The anterior ring of the thorax of
insects.
PR6TOPHYTA (Gr. psotos: and phuton, plant). The lowest division of plants.
PROTOPLASM (Gr. protos; andplasso, I mould). The elementary basis of organised tissues. Sometimes used synonymously for the "sarcode " of the
Protozoa.
PROTOPODITE (Or. protos, first; and pous, foot). The basal segment of the
typical limb of a Crustacean.
PROTOZOA (Gr. protos: and zois, animal). The lowest division of the animal
kingdom.
PROVENTRICULUS (Lat. pro, in front of; ventriculus, dim. of venter, belly). The
cardiac portion of the stomach of Birds.
PROXIMAL (Lat. proximu-, next). The slowly-growing, comparatively-fixed
extremity of a limb or of an organism.




GLOSSARY.                            645
PSALTERIUM (Lat. a stringed instrument). The third stomach of Ruminants.
(See Omasumn.)
PSEUDEMBRYO (Gr. pseudos, falsity; embruon, embryo). The larval form of an
Echinoderm.
PSEUDOBRANCHIA (Gr. pseudos, falsity; braycglia, gill). A supplementary gill
found in certain fishes, which receives arterialised blood only, and does
not, therefore, assist in respiration.
PSEUDOH3MAL (Gr. pseudos, falsity; and hlaima, blood). Applied to the vascular system of A nnelida.
PSEUDO-HEARTS. Certain contractile cavities connected with the atrial system
of Brachiopoda, and long considered to be hearts.
PSEUDO-NAVICELLAL (Gr. pseudos, false; and Navicsda, a genus of Diatoms).
The embryonic forms of the Gregarinidce, so called from their resemblance
in shape to the Nlavicula.
PSEUDOPtDIA (Gr. pseudos; and pous, foot).  The extensions of the bodysubstance which are put forth by the Rkidzopoda at will, and which serve
for locomotion and prehension.
PSEUDOVA (G. pseudos; Lat. ovum, egg). The egg-like bodies from which
the young of the viviparous Aphkis are produced.
PTEROPODA (Gr. pteron, wing; and potes, foot). A class of the Mollhsca which
swim by means of fins attached near the head.
PTEROSAURIA (Gr. pteron, wing; saunta, lizard). An extinct order of Reptiles.
PUBrs (Lat. pubes, hair). The share-bone; one of the bones which enter into
the composition of the pelvic arch of Vertebrates.
PULMOGASTEROPODA (= Pulmonifera).
PULMONARIA. A division of A rachlida which breathe by means of pulmonary sacs.
PULMONATE. Possessing lungs.
PULMONIFERA (Lat. pulmso, a lung; and fero, 1 carry). The division of Mollusca which breathe by means of a pulmonary chamber.
PUPA (Lat. a doll). The stage of an insect immediately preceding its appearance in a perfbct condition. In the puipa-stage it is usually quiescent-when
it is often called a " chrysalis;" but it is sometimes active —when it is often
called a " nymph."
PYLORUS (Gr. puloros, a gatekeeper).  The valvular aperture between the
stomach and the intestine.
PYRIFORM (Lat. pyrus, a pear; andforena, formed). Pear-shaped.
QUADRUMANA (Lat. quatuor, four; manus, hand). The order of Mammals
comprising the Apes, Monkeys, Baboons, Lemurs, &c.
RADIATA (Lat. radius, a ray). Formerly applied to a large number of animals
which are now placed in separate sub-kingdoms (e.g., the Coelenterata, the
fEchinodermnata, the I7fusoria, &c.)
RADIOLARIA (Lat. radius, a ray). A division of Protozoa.
RADIUS (Lat. a spoke or ray). The innermost of the two bones of the forearm of the higher Vertebrates. It carries the thumb, when present, and
corresponds with the tibia of the hind-limb.
RAMUS (Lat. a branch). Applied to each half or branch of the lower jaw or
mandible of Vertebrates.
RAPTORES (Lat. rapto, I plunder). The order of the Birds of Prey.
RASORES (Lat. adelo, I scratch). The order of the Scratching Birds (Fowls,
Pigeons, &c.)
RATITE (Lat. rates, a raft). Applied by Huxley to the Culsorial Birds, which
do not fly, and have therefore a raft-like sternum without any median
keel.
RECTUM (Lat. rect us, straight). The terminal portion of the intestinal canal,
opening at the surface of the body at the anus.
REPtrILIA (Lat. repto, I crawl). The class of the Vertebrata comprising the
Tortoises, Snakes, Lizards, Crocodiles, &c.
RwsTICULAlhIA (Lat. reticulum, a net). Employed by Dr Carpenter to desig.




646                          GLOSSARY.
nate those Protozoa, such as the Foracminifera, in which the pseudopodia
run into one another and form a network.
RETICULUM (Lat. a net). The second division of the complex stomach of
Ruminants, often called the "honeycomb bag."
REVERSED. Applied to spiral'univalves, in which the direction of the spiral
is the reverse of the normal-i.e., sinistral.
RHIZOPHAGA (Gr. rhiza, root; phaqyo, I eat). A group of the Marsupials.
RHIZOPODA (Gr. rhiza, a root; and poses, foot). The division of Protozoa comprising all those which are capable of emitting pseudopodia.
RHYNCHOLITES (Gr. rhluncos, beak; and tithos, stone).  Beak-shaped fossils,
consisting of the mandibles of C'ephalopoda.
RODENTIA (Lat. rodo, I gnaw). An order of the Mammals; often called Glires
(Lat. glis, a dormouse).
ROSTRUM (Lat. rostrum, beak).  The "beak" or suctorial organ formed by
the appendages of the mouth in certain insects.
ROTATORIA (= Rotifera).
ROTIFERA (Lat. rota, wheel; and feore, I carry).  A class of the Scolecidca
(A nnuloida) characterised by a ciliated "trochal disc."
RUGOSA (Lat. ruqosus, wrinkled).  An extinct order of Corals.
RUMEN (Lat. the throat).  The first cavity of the complex stomach of Ruminants; often called the " paunch."
RUMINANTIA (Lat. rumninor, I chew the cud). The group of Hoofed Quadrupeds (Ungulata) which "ruminate" or chew the cud.
SACRUM. The vertebra (usually anchylosed) which unite with the haurchbones (ilia) to form the pelvis.
SAND-CANAL (= STONE-CANAL).  The tube by which water is conveyed from
the exterior to the ambulacral system of the Echinodermzata.
SARCODE (Gr. sarx, flesh; eidos, form). Tile jelly-like substance of which the
bodies of Protozoa are composed.  It is an albuminous body containing oilgranules, and is sometimes called "animal protoplasm."
SARCOIDS (Gr. sarx; and eidos, form). The separate amcebiform particles
which in the aggregate make up the "flesh" of a Sponge.
SAURIA (Gr. saura, a lizard).  Any lizard-like Reptile is often spoken of as a
"Saurian;" but the term is sometimes restricted to the Crocodiles alone,
or to the Crocodiles and Lacertilians.
SAUROBATRACHIA (Gr. santa; batracl]os, fr'og).  Sometimes applied to the
order of the tailed Amphibians (Urodela).
SAUROPSIDA (Gr. saura; and opsis, appearance).  The name given by Huxley
to the two classes of the Birds and Reptiles collectively.
SAUROPTERYGIA (Gr. sanra; pterux, wing). An extinct order of Reptiles,
called by Huxley Plesiosaeria, from the typical genus Plesiosaurus.
SAURURmE (Gr. santta; oura, tail).  The extinct order of Birds comprising
only the Archceoptesrxx.
SCANISORES (Lat. sceaedo, I climb). The order of the Climbing Birds (Parrots,
Woodpeckers, &c. )
SCAPHOGNATHITE (Gr. skaphlos, boat; and gnathos, jaw). The boat-shaped
appendage (epipodite) of the second pair of maxillase in the Lobster; the
function of which is to spoon out the water from the branchial chamber.
SCAfULA (Lat. for shoulder-blade). The shoulder-blade of the pectoral arch
of Vertebrates; in a restricted sense, the row of plates in the cup of
Crsinoils, which give origin to the arms, and are usually called the "axillary
radials."
BCLERENCHYMA (Gr. skleros, hard; and eniclhuma, tissue).  The calcareous
tissue of which a coral is composed.
SCLER'ITES (Gr. skieros). The calcareous spicules which are scattered in the
soft tissues of certain A ctieozoa.
SCLEROBASIC (Gr. skleros, hard; basis, pedestal). The coral which is produced
by the outer surface of the integument in certain A ctiozoa (e.g., Red Coral),
and forms a solid axis which is invested by the soft parts of the animal. It
is called " foot-secreticn'" by Mr Dana.




GLOSSARY.                              647
SCLERODERMIC (Gr. skleros; and derma, skin).  Applied to the corallum
which is deposited within the tissues of certain Actinozoa, and is calleou
"tissue-secretion" by Mr Dana.
SCLEROTIC (Gr. skleros, hard). The outer dense fibrous coat of the eye.
SCOLECIDA (Gr. skolex, worm). A division of the Annuloida.
SCOLEX (Gr. skolex). The embryonic stage of a Tape-worm, formerly known
as a " Cystic Worm "
SCUTA (Lat. scittum, a shield). Applied to any shield-like plates; especially
to those which are developed in the integument of many Reptiles.
SELACHIA or SELACHII (Gr. selaclhos, a cartilaginous fish, probably a shark).
The sub-order of Elasmobranchii, comprising the Sharks and Dog-fishes.
SEPIOSTAIRE. The iiternal shelh of the Cuttle-fish, commonly known as the
"cuttle-bone."
SEPTA. Partitions.
SERPENTIFORm.  Resembling a serpent in shape.
SERTULARIDA (Lat. serturn, a wreath). An order of HBydro,.oa.
SESSILE (Lat. sedo, I sit). Not supported upon a stalk or peduncle; attached
by a base.
SELTE (Lat. bristles). Bristles, or long stiff hairs.
SETIFEROUS. Supporting bristles.
SETIGEROUS (= Setiferous).
SETOSE. Bristly.
SILICEOUS (Lat. silex, flint). Composed of flint.
SINISTRAL (Lat. sinistra, the left hand).  Left-handed; applied to the direction of the spiral in certain shells, which are said to be " reversed."
SINUS (Lat. sinus, a bay). A dilated vein or blood-receptacle.
SIPHON (Gr. siphon, a tube).  Applied to the respiratory tubes in the Mollusca; also to other tubes of different functions.
SIPHONoPHORA (Gr. siphon; and phero, I carry).  A division of the Hydrlozoa,
comprising the Oceanic forms (Calycophoridwe and Physoplhori.ce).
SIPHONOSTOMATA (Gr. sphon,; and stoma, mouth).  The division of Gasteropodous Miolluscs, in which the aperture of the shell is not "' entire," but
possesses a notch or tube for the emission of the respiratory siphon,
SIPHUNCLE (Lat. siphuncuzlus, a little tube).  The tube which connects
together the various chambers of the shell of certain C'e.calopoda (e.g.,
the Pearly Nautilus).
SIPHUNCULOIDEA (Lat. siphunculus, a little siphon). A class of Anearthroopoda
(A znulosa).
SIRENIA (Gr. seiren,,   a mermaid).  The order of  armmnzalia comprising the
Dugongs and Manatees.
SOLIDUNGULA (Lat. solid us, solid; lungula, a hoof).  The group of Hoofed
Quadrupeds comprising the Horse, Ass, and Zebra, in which each foot has
only a single solid hoof.  Often called Sol)ipedia.
SOMATIC (Gr. soma, body).  Connected with the body.
SOMATOCYST (Gr..soena; and Xt:stis, a cyst). A peculiar cavity in the ccenosarc
of the Calycoplhoridce (RlHydrozoa).
SOMITE (Gr. soma).   A single segment in the body of an  Articulate
animal.
SPERMARIUM. The organ in which spermatozoa are produced.
SPERMATOPHORES (Gr. spe'ma, seed; phero, I carry). The cylindrical capsules of the Cephalopeda, which carry the spermatozoa; sometimes called
the " moving filaments of Needham."
SPERMATOZOA (Gr. sperma, seed; and zo6n, animal). The microscopic filaments which form the essential generative element of the male.
SPICULA (Lat. spiculusm, a point). Pointed needle-shaped bodies.
SPINNERETS. The organs by means of which Spiders and Caterpillars spin
threads.
SPIRACLES (Lat. spiro, I breathe).  The breathing-pores, or apertures of the
breathing-tubes (trachae) of Insects. Also the single nostril of tiae Hagfishes, the " blow-hole" of Cetaceans, &c.
SPLANCHNOSKELF:TON  (Gr. splegcycltna, viscera; skcletos, dry).  The hard




648                          GLOSSAR'-.
structures occas'onally developed in connection with the internal organs or
viscera.
SPONGE-PARTICLES. (See Sarcoids.)
SPONGIDA (Gr. spoggos, a sponge). The division of Protozoa commonly known
as sponges.
SPORES (Gr. spora, seed).  Germs, usually of plants; in a restricted sense,
the reproductive "gemmules" of certain Sponges.
SPOROSACS (Gr. spora, seed; and sakkos, a bag).  The simple generative
buds of certain Hydrozoa, in which the medusoid structure is not developed.
SQUAMATA (Lat. squama, a scale). The division of Reptiles comprising the
Oplhidia and Lacertilia in which the integument develops horny scales, but
there are no dermal ossifications.
STATOBLASTS (Gr. statos, stationary; blastos, bud). Certain reproductive buds
developed in the interior of Polyzoa, but not liberated until the death of
the parent organism;
STEGANOPHTHALMATA (Gr. steganos, covered; and ophthalmos, the eye). Applied by Edward Forbes to certain feledusa, in which the sense-organs
(" marginal bodies") are protected by a sort of hood. The Steyanophthalmata are now separated from the true Medusidce, and placed in a separate
division under the name Lucernarida.
STELLERIDA (Lat. stella, star). Sometimes employed to designate the order
of the Star-fishes.
STELLIFOIRM. Star-shaped.
STEMMATA (Gr. stemma, garland). The simple eyes, or "ocelli," of certain
animals, such as Insects, Spiders, and Crustacea.
STERNUM (Gr. sternon). The breast-bone.
STIGMATA. The breathing-pores in Insects and Arachnida.
STOLON (Gr. stoles, a sending forth). Offshoots.-The connecting processes
of sarcode, in l'oraminifera; the connecting tube in the social Ascidians;
the processes sent out by the coenosarc of certain A ctinozoa.
STOMAPODA (Gr. stoma, mouth; poes, foot). An order of Crustacea.
STOMATODE (Gr. stomea). Possessing a mouth. The Infusoria are thus often
called the Stomatode Protozoa.
STREPSIPTERA (Gr. streph/o, I twist; andpteron, iving).  An order of Insects
in which the anterior wings are represented by twisted rudiments.
STREPSIRHINA (Gr. streph/o, I twist; rhines, nostrils).  A group of the Quadrumana, often spoken of as Prosimiae.
STROBtLA (Gr. strobilos, a top, or fir-cone).  The adult Tapeworm with its
generative segments or proglottides; also applied to one of the stages in
the life history of the Lucernarida.
STYLIFORM (Lat. stylus, a pointed instrument; forma, form). Pointed in
shape.
SUB-CALCAREOUS. Somewhat calcareous.
SUB-CENTRAL. Nearly central, but not quite.
SUB-PEDUNCULATE. Supported upon a very short stem.
SUB-SESSILE. Nearly sessile, or without a stalk.
SUPINATION (Lat. supinus, lying with the face upwards). The act of turning
the hand with the palm upwards.
SUTURE (Lat. sue, I sew).  The line of junction of two parts which are
immovably connected together. Applied to the line where the whorls
of a univalve shell join one another; also to the lines made upon the
exterior of the shell of a chambered Cephalopod by the margins of tle
septa.
SWIMMERETS. The limbs of Crustacea, which are adapted for swimming.
SYMPHYSIS (Gr. sumphusis, a growing together).   Union of two bones in
which there is no motion, or but a very limited amount.
SYNAPTICULA (Gr. sunapto, I fasten together). Transverse props sometimes
found in Corals, extending across the loculi like the bars of a grate.
SYSTOLE (Gr. su.tello, I contract). Applied to the contraction of any contractile cavity, especially the heart.




GLOSSARY.                            649
TABrLE (Lat. tabula, a tablet). Horizontal plates or floors found in some
Corals, extending across the cavity of the " theca," from side to side.
TACTILE (Lat. tango, I touch). Connected with the sense of touch.
T.ENIADA (Gr. tainia, a ribbon). The division of Scolecida comprising the
Tapeworms.
TE.NIOID (Gr. tainia; and eidos, form). Ribbon-shaped, like a Tape-worm.
TARSO-AMETATARSUS. The single bone in the leg of Birds produced by the
union and anchylosis of the lower or distal portion of the tarsus with the
whole of the metatarsus.
TARSUS (Gr. tarsos, the flat of the foot). The small bones which form the
ankle (or " instep " of man), and which correspond with the wrist (caTpus)
of the anterior limb.
TECTIBRANCHIATA (Lat. tectus, covered; and Gr. bragchia, gills). A division
of Opistlobranchiate Gasteropoda in which the gills are protected by the
mantle.
TEGUMENTARY (Lat. tegzumentum, a covering). Connected with the integument or skin.
TELEOSTEI (Gr. teleios, perfect; osteon, bone). The order of the "Bony"
Fishes.
TELSON (Gr. telson, a limit). The last joint in the abdomen of Cr-ustacea;
variously regarded as a segment without appendages, or as an azygos
appendage.
TENUIROSTRES (Lat. tenuis, slender; rostrum, beak). A group of the Perching Birds characterised by their slender beaks.
TERGUM (Lat. for back). The dorsal arc of the sonmite of an Arthropod.
TERRICOLA (Lat. terra, earth; and cole, I inhabit). Employed occasionally
to designate the Earth-worms (Lumbricidae).
TEST (Lat. testa, shell). The shell of Mollusca, which are for this reason
sometimes called " Testacea;" also, the calcareous case of Echinoderms;
also, the thick leathery outer tunic in the Tunicata.
TrESTAcEOUS. Provided with a shell or hard covering.
TESTIS (Lat. testis, the testicle). The organ in the male animal which produces the generative fluid or semen.
TETRABRANCHIATA(Gr. tetra, four; bragchia, gill). The order of Cephalo2poda,
characterised by the possession of four gills.
THALASSICOLLIDA (Gr,- thalassa, sea; kolla, glue). A division of Protozoa.
THECA (Gr. theke, a sheath). A sheath or receptacle.
THECOSOMATA (Gr. theke; and soma, body).  A division of Pterol2odons
Molluscs, in which the body is protected by an external shell.
THERIOMORPHA (Gr. ther, beast; morphe, shape). Applied by Owen to the
order of the Tail-less Amphibians (Anoura).
THORAX (Gr. a breastplate). The chest.
THREAD-CELLS. (See Cnidse.)
THYSANURA (Gr. thsusanoi,. fringes; and ouera, tail).  An order of Apterous
Insects.
TIBIA (Lat. a flute). The shin-bone, being the innermost of the two bones of
the leg, and corresponding with the radius in the anterior extremity.
TOTIPALMATE (Lat. totus, whole; palma, the palm of the hand). A group
of Wading Birds in which the hallux is united to the other toes by membrane, so that the feet are completely webbed.
TRACHEA (Gr. tracheia,.the rough wind-pipe). The tube which conveys air to
the lungs in the air-breathing Vertebrates.
TRACHEaE. The breathing-tubes of insects and other articulate animals.
TRACHEARIA. The division of Arachlida which breathe by means of trachewe.
TREMATODA (Gr. trena, a pore). An order of Scolecida.
TRICHOCYSTS (Gr. thrix, hair; and kustis, a cyst). Peculiar cells found in
certain Inlfsoria, and very nearly identical with the "thread-cells" of
Coelenterata.
TRILOBITA (Gr. treis, three; lobos, a lobe). An extinct order of Crustaceans.
TRITOZOiID (Gr. tritos, third; z6on, animal; and -eidos, form). The zohid




650                          GLOSSARY.
produced by a deuterozooiid; that is to say, a zoiiid of the third generation.
TROCHAL (Gr. trochos, a wheel). Wheel-shaped; applled to the ciliated disc
of the Rot fe)ra.
TROCHANTER (Gr. trecho, I turn).  A process of the upper part of the thighbone (femur) to which are attached the muscles which rotate the limb.
There may be two, or even three, trochanters present.
TtOCHOID (Gr. trochos, a wheel; and eidos, form). Conical with a flat base;
applied to the shells of Foraminifera and Univalve Molluscs.
TROPHI (Gr. troohos, a nourisher). The parts of the mouth in insects which
are concerned in the acquisition and preparation of food. Often called
" instrumenta cibaria."
TROPHOSOME (Gr. trepho, I nourish; and soma, body). Applied collectively
to the assemblage of the nutritive zoiids of any Hydrozo6ni.
TRUNCATED (Lat. trunco, I shorten). Abruptly cut off; applied to univalve
shells, the apex of which breaks off, so that the shell becomes "decollated."
TUBICOLA (Lat. tuba, a tube; and cola, I inhabit).  The order of A nnelida
which construct a tubular ease in which they protect themselves.
TuBICOLOUS. Inhabiting a tube.
TUNICATA (Lat. tunica, a cloak). A class of MIolluscoida which are enveloped
in a touoh leathery case or "test."
TURBELLARIA (Lat. Surbo, I disturb).  An order of Scolecida.
TURBINATED (Lat. turbo, a top). Top-shaped; conical, with a round base.
ULNA (Gr. oleze, the elbow). The outermost of the two bones of the forearm, corresponding with thefibela of the hind-limb.
UMBELLATE (Lat. serbella, a parasol).  Forming an umbel-i.e., a number of
nearly equal radii all proceeding from one point.
UMBILICUS (Lat. for navel). The aperture seen at the base of the axis of
certain univalve shells, which are then said to be "perforated" or "umbilicated. "
UMBO (Lat. the boss of a shield). The beak of a bivalve shell.
UMBRELLA. The contractile disc of one of the Lucernarida.
UNCINATE (Lat. u2cinus, a hook). Provided with hooks or bent spines.
UNGUICULATE (Lat. unguis, nail). Furnished with claws.
UNGULATA (Lat. ungulca, hoof). The order of lannImals comprising the Hoofed
Quadrupeds.
UNGULATE. Furnished with expanded nails constituting hoofs.
UNILOCULAR (Lat.  uuzcs, one; and loculus, a little purse).  Possessing a single
cavity or chamber. Applied to the shells of Fo` raminifera and Jlollusca.
UNIVALVE (Lat.  0st, one0110; valve, folding-doors).  A shell composed of a
single piece or valve.
URODELA (Gr. oura, tail; delos, visible). The order of the tailed Amphibians (Newts, &c.)
URTICATING CELLS (Lat. urtica, a nettle).  (See Cnidve.)
VACUOLES (Lat. vacusts, empty). The little cavities formed in the interior of
many of the Protozoa by the presence of little particles of food, usually
surrounded by a little water. These are properly called " food-vacuoles,"
and were supposed to be stomachs by Ehrenberg. -Also the clear spaces
which are often seen in the tissues of many Ccel-eterata.
VARICES (Lat. varix, a dilated vein). The ridges or spinose lines which mark
the former position of the mouth in certain univalve shells.
VASCULAR (Lat. vas, a vessel). Connected with the circulatory system.
VELUM (Lat. a sail). The membrane which surrounds and partially closes
the monuth of the " disc " of Mledusce, or mredusiform gonophores.
VENTRAL (Lat. veter, the stomach). Relating to the inferior surface of the
body.
VENTRICLE (Lat. dim of venter, stomach). Applied to one of the cavities of
the heart, which receives blood from the auricle.




GLOSSARY.                            651
VERMES (Lat. vermis, a worm). Sometimes employed at the present day in
the same, or very nearly the same, sense as Aanauloida, or as Annuloida
plus the Anarthropoda.
VERMIFORM (Lat. vermis, worm;. andforma, form). Worm-like.
VERTEBRA (Lat. verto, I turn). One of the bony segments of the vertebral
column or back-bone.
VERTEBRATA. (Lat. vertebra, a bone of the back, from vertere, to turn). The
division of the Animal Kingdom roughly characterised by the possession of
a back-bone.
VESICLE (Lat. vesica, a bladder). A little sac or cyst.
VIBRACULA (Lat. vibro, I shake). Long filanmentous appendages found in
many Polyzoa.
VIBRIONES (Lat. vibro, I shake). The little moving filaments developed in
organic infusions.
VIPERINA (Lat. vipera, a viper). A group of the Snakes.
VIVIPAROUS (Lat. vivus, alive; and pario, I bring forth).  Bringing forth
young alive.
WHORL. The spiral turn of a univalve shell.
XIPHISTERNUM (Gr. xiphos, sword; sternon, breast-bone).  The inferior or
posterior segment of the sternum, corresponding with the " xiphoid cartilage " of human anatomy.
XIPHOSURA (Gr. xiphos, a sword; and oura, tail). An order of Crustacea,
comprising the Limuli or King-Crabs, characterised by their long swordlike tails.
XYLOPHAGOUS (Gr. xulon, wood; and phago, I eat). Eating wood; applied
to certain Mollusca.
ZOUID (Gr. zoon, animal; and eidos, like). The more or less completely independent organisms, produced by gemmation or fission, whether these remain attached to one another or are detached and set free.
ZOOPHYTE (Gr. zoon, animal; phuton, plant). Loosely applied to many plantlike animals, such as Sponges, Corals, Sea-anemones, Sea-mats, &c.
ZOOSPORES (Gr. zo6n, animal; and spora, seed).  The ciliated locomotive
germs of some of the lowest forms of plants (Protophyta).
29




INDEX
AARDVARk, 541.                            Agouti, 588.
Aardwolf, 582.                            Ailurus, 579.
Abdominalia (Cirripedia), 214; (Fishes),  Air-bladder of Fishes, 374.
385.                                    Air-receptacles of Birds, 466, 467.
Abranchiata (Vertebrata), 359.            Aleedo, 501.
Abyla, 95.                                Alca, 476.
Acalephce, 100.                           Alces, 564.
Acanthocephala, 165, 172; characters of,  Alcidee, 476.
175, 176.                               Alcyonaria, 116; characters and divisions
Acanthometra, 61.                           of, 125-128; distribution of, in time, 139.
Acanthometrina, 61.                       A lcyonidoe, 125, 126.
Acanthophis, 432.                         A lcyonium, 126.
Acanthopteri, 387.                        Allantoidea, 359.
Acanthopterygii, 376, 382.                Allantois, 359, 360.
Acanthospongia, 68.                       Alligator, 442, 444.
Acarida, 240.                             Alpaca, 562.
Acarina, 238; characters and families of,  Alveolus (Belemnite), 330.
239.                                    Amber, insects preserved in, 278.
Accipitrince, 503.                        Amblyrhynchus, 442.
Acephala (Mollusca), 300.                 Amblystoma, 411.
Acerotherium, 613.                        Amlbulacral syStem (Echinodermata), 142,
Acervulina, 56.                             143; of Echinus, 147; of Star-fishes,
Acetabula, 322.                             151; of Ophiuroidea, 154; of Crinoidea,
Achetina, 260.                              155; of Holothuroidea, 160, 161.
Achtheres, 209.                           Ameiva, 439.
Acicula. 319.                             Ametabolic Insects, 254, 257.
Aciculid6e, 319.                          Amia, 391.
Acineta, 70, 75.                          Ammodytes, 386.
Acipenser, 403.                           Anwnonites, 333, 334, 335, 337.
Acmcea, 318.                              Ammonitide, 333, 334, 335; characters
Acorn-shells, 210, 211, 212.                of, 333; distribution of, in time, 337.
Acrodus, 397.                             Amnion, 359.
Acrotreta, 297.                           Amniota, 359.
Acrydium, 260.                            Amoeba, 7, 48; structure of, 50; pseudoActeonic, 319.                              podia of, 51; reproduction of, 51.
Actinia, 115, 117, 118.                   Amoebea, 49, 51, 52.
Actisidce, 117, 118; development of, 118.  Amoebina, 52.
Actinomeres, 130.                         Amphibia, 359, 360, 399, 400; general
Actinophrys, 52, 54, 61.                    characters of, 406-408; development of,
Actinosoma, 116.                            406, 407; respiratory organs of, 407;
Actinozoa, 80; characters of, 114, 115;    orders of, 408-417; distribution of, in
divisions of, 116; distribution of, 134.  time, 418.
Aculeus, 268.                             Amphiccelia (Crocodilia), 443, 445.
Adelarthrosomata, 238; characters and   Amphidiscs, 66.
families of, 241.                       Ainphilestes, 608..Egijindoe, 103, 110.                     Amphioxscs, 348, 356, 373, 376..'gignopsis, 103.                         Anphipnseusta, 410.
dEolidce, 319.                            Amphipoda, 208, 223; characters of, 224;.olis, 319.                                 heart of, 225..Xpiornis, 508.                           Amphisboena, 435, 437.
Agarnidce, 440.                           Amphispowgjia, 68.
Agapornis, 494.                           Aemphitherium, 608, 609.
A gathistega, 57.                         Amphiutma, 410, 411.
Agelacrisnites, 158.                      Ampullaria, 310, 318.




INDEX.                                   653
Anacanthini, 385.                          Aplysia, 319.
Anallantoidea, 359.                        Aplysiadce, 314, 319.
Analogy, 17.                              Apoda (Cirripedia), 215; (Amphibia),
Anamniota, 359.                              409; (Fishes), 384, 386.
Ananchytidoe, 150.                        Apodemata, 204.
A narthropoda, 185, 14.                    Apolemiadce, 99.
Anas, 479.                                 Aporosa (Corals), 123, 139, 140.
Anatidce, 479.                             Aporrhais, 317.
Anatina, 307.                              Appendicularia, 290, 291.
Anatisidmce, 307.                          Aptenodytes, 476.
Anchitherium, 613.                         Aptera, 254, 257.
Ancyloceras, 333, 334, 335, S38            Apterygidoe, 485, 486.
Ancylus, 319.                              Apteryx, 484, 486, 487.
Andrias, 412, 418.                         Aptornis, 507.
Androphores, 98.                           Apus, 219, 234.
Anrgelina, 220.                            Aquiferous system  (see Water-vascular
Anguillula, 177, 179.                        system).
Anguillulidoe, 179.                        Arachnactis, 117, 119.
Anguis, 435, 437, 438.                     Arachnida, 199, 200; characters of, 235;
Animals and Plants, differences between,    somite of, 235; organs of the mouth of,
8-12.                                      236; respiratory process of, 237; disAnisonema, 76.                               tribution in time, 244.
Annelida, 185; characters of, 187-189;  Arainoa, 494.
pseudoheemal system of, 1f88; orders of,  Araneida, 241; characters of, 243; webs
189; distribution of, in time, 197, 198;    of, 243; reproductive process of, 244;
phosphorescence of, 76; urticating cells    distribution of, in time, 244.
of, 80.                                 Area, 306.
Annulata (see Annelida).                   Arcadoe, 3n5, 306.
Annuloida, 16; characters and divisions   Arcella, 52.
of, 141, 142.                           Arcellini, 52.
Annulosa, 16; characters and divisions   Archceocidaris, 150, 165.
of, 185.                                Archceocyathus, 68.
Anodon, 3'6.                               Archceopteryx, 457, 472, 474, 504, 505,
Anomodontia, 448.                            507.
Anomura, 230, 231.                         Archencephala, 522.
Anoplotherium., 557, 613.                 Archiulidce, 247.
Anoplura, 258.                            Archiulus, 247.
Anoura, 407; characters of, 413; develop-   Arctictis, 579.
ment of, 415; families of, 416.         Aretisca, 239.
Anser, 479.                                Arctomnys, 591.
Anserince, 479.                            Ardea, 482, 483.
Ant-eaters, 511, 540, 541.                Ardeidce, 482.
Antelopes, 561, 566, 615.                  Arenicola, 196, 198.
Antennae, of Lobster, 206, 228; of Rhizo-   Argonauta, 322, 325, 338; shell of, 327,
cephalta, 210; of Cirripedes, 211, 212;    328; reproductive process of, 325; hecof Cladocera, 218; of Xiphosura, 222;    tocotylus of, 325, 328.
of Arachnida, 236; of Myriapoda,   Argonautidce, 328, 335.
246; of Pauropus, 247; of insecta,   Aristotle's Lantern, 148.
254.                                    Armadillos, 510, 511, 521, 524, 539.
Antennules, of Lobster, 206; of Limulus,  Arms, of Star-fishes, 150; of Ophiuroidea,
222.                                      153; of Crinoidea, 155; of Comatula,
Anthracotherium, 614.                        157; of Cystoidea, 159; of Brachi:oAnthropoid Apes, 604.                       poda, 294; of Cuttle-fishes, 322; of
Anthropoides, 482.                          Nautilus, 330, 331.
Anthus, 499.                              Artemia, 219.
Antilopidce, 566.                         Arthrogastra, 212.
Antipathidoe, 122, 129.                   Arthropoda, 185; characters and divisions
Antipathes, 122, 139.                        of, 199, 200.
Antlia, 265.                              Articulata, 199.
Ants, 261, 262; communities of, 269;  Artiodactyla, 553, 555, 556.
slave-making instincts of, 270; relations   Arvicola, 590.
with plant-lice, 270.                    Asaphus, 220.
Antrostomus, 500.                         Ascaris, 177, 179.
Apes, 604.                                Ascidiadoe, 291.
Aphanapteryx, 492.                         Ascidioida (see Tunicata).
Aphaniptera, 264.                         AscidinIns, solitary, social, and compound,
Aphides, 259; alleged parthenogenesis    290, 291.
of, 32.                                 Ascoceras, 333.
Aphrodite, 195, 197.                      Asellus, 226.
Apiocrinidce, 157.                         4sinus, 555.
Apiocrinus, 163.                          A4siphonida (Lamellibranchiata), 305, 306.
Aplacental Mammals, 522.                   Aspergillumn, 308.




654                                 INDEX.
Asplanchna, 183.                           Barnacles, 210, 211, 212, 213, 214.
Astacus, 228.                              Bascanion, 433.
Astarte, 307.                              Bathybius, 11, 58.
Asteriadoe, 153.                           Batides, 397, 398.
Asterinidce, 153.                          Batrachia, 413.
Asteroidea, 143, 144; general characters   Bats, 512, 513, 515, 526, 592, 598, 594.
of, 150; families of, 153; distribution   Bear, 577, 578, 616.
of, in space, 162; in timle, 162, 163, 164.   Beaver, 589.
Asteroid Polypes, 125.                     Bee-eaters, 500.
Astrceidoe, 138, 140.                      Bees, parthenogenesis of, 32, 33; communAstrogoniunm, 164.                           ities of, 268.
Astropecten, 151, 164.                     Belemnnites, structure of, 329.
Astropectinidce, 155.                      Belemnitidce, 329, 330, 335, 338.
Astrophydioe, 155.                         Belemnitella, 335.
Astrophyton, 154.                          Belemniteuthis, 335.
Ateles, 602, 6r3.                          Belinurus, 234.
Atherura, 589.                             Bellerophina, 337.
Athorybiadce, 99.                          Bellerophon, 337.
Athyris, 296.                              Belodon, 445.
Atlanta, 319.                              Beloptera, 335.
Atlantidee, 316, 319.                      Beluga, 392.
Atolls, 135, 136, 138.                     Benturong, 579.
Atrial system (Brachiopoda), 275, 294.     Berve, 133.
Atrium (Tunicata), 289.                    Bervidce, 134.
Auchenia, 562.                             Bimana, 526; general characters of, 606.
Auloporidce, 140.                          Biology, definition of, 1.
Aulosteges, 297.                           Bioplasm, 5.
Aurelia, 110.                              Bipes, 435, 437.
Aurelia, 256.                              Bipinnaria, 152.
Auricula, 319.                             Bird-lice, 258.
Auricularia, 160.                          Birds of Prey, 501.
Auriculidce, 317, 319.                     Bird's-head process, 282,
Aves, 359; general characters of, 453;   Birgus, 231.
feathers of, 454, 456; vertebral column   Bison, 568.
of, 456, 457; beak of, 457; pectoral   Bivalve Shell-fish, 300.
arch and fore-limb of, 458-462; hind-   Bladder, contractile, of Rotifera, 182.
limb of, 462-464; foot of, 463; ligestive   Blastoidea, 144; general characters of,
system of, 464-466; respiratory system     159; distribution of, in time, 163.
of, 466, 467; circulatory system  of,  Blattina, 260.
468; nervous system  and organs of  Blennidoe, 887.
sense of, 470; reproductive system  of,  Blind-worm, 437.
469; migrations of, 472; divisions of,   Boa, 433.
472; orders of, 474-505; distribution of,   Boidoe, 493.
in time, 505-508.                        Bombidce, 269.
Avicula, 306.                              Bonasa, 489.
Avicularia, 282, 284.                      Bonellia, 186.
A viculidce, 305, 306.                     Book-scorpion, 241,
Avocet, 480.                               Bopyridce, 226.
Axinus, 306.                               Bos, 568, 615.
Axolotl, 411, 412.                         Boschas, 479.
Aye-Aye, 600.                               Botaurus, 483.
Bothrioeephalus, 167, 170.
BABOON, 604.                               Botryllidce, 292.
Babyroussa, 557.                           Botryllus, 290, 291.
Bacteria, 36, 37.                           Bourgueticrinus, 157.
Bactrites, 338.                             Bovide, 565, 567, 615.
Baculites, 333, 334, 335, 838.              Brachiopoda, 274, 275, 276; general char.
Badger, 579.                                  acters of, 292; shell of, 292, 293; arms
Balcena, 545, 548.                            of, 294; atrial system of, 294; nervous
Balcenidoe, 545, 546.                         295; vascular system of, 295; divisions
Balcenodon, 613.                             of, 295; distribution of, in space, 298;
Balcenoptera, 548                            in time, 298; development of, 295.
Balancers, 250, 264.                       Brachiuna, 209.
Balanidce, 207, 211, 212, 213; distribution   Brachymetopus, 234.
of, in time, 233.                        Brachyura, 208; characters ot, 231, 232;
Balanus, 212, 213.                            development of, 232.
Balearica, 482.                             Bracts, 95 (see Hydrophyllia).
Baleen, 545, 546, 547, 548.                BradypodidEe, 537, 611.
Balistdoce, 388.                           Bradypus, 510, 538, 539.
Bandicoot, 534.                            Bramatheriurm, 615.
Banxring, 597.                             Branchial arches (Fishes), 367, 371.
Barrier-reefs, 135, 136, 137, 138.         Branchial hearts (Cuttle-fishes), 324.




INDEX.                                     655
Branchial sac (Tunicata), 288, 289, 291;   Caprimulgidc, 500.
(Lancelet), 377.                           Caprinella, 306.
Branchiata (Vertebrata), 359.                Capybara, 588.
Branchifera, 313, 317.                        Carapace, of Diffugia, 51; of Arcella, 52;
Branchiobdella, 190.                           of Vaginicola, 75; of Crustacea, 203,
Branchiogasteropoda, 310, 313.                  204; of Lolbster, 228; of Crab, 232; of
Branchiopoda, 208, 215, 217.                   Chelonian Reptiles, 424.
Branchiostegal rays, 366, 372, 383.           Carcharias, 396, 397.
Branchiostonma, 377 (see Arnphio;zus)         Carcharodon, 4u5.
Blranchipus, 219.                             Carchesium, 75.
IBrevilinguia, 436.                           Cardiadce, 306, 307.
Brevipennatoe, 475.                           Cardiurn, 307.
Brine-shrimp, 219.                            Carduelis, 498.
Bruta, 537 (see Edentata).                    Carinaria, 315, 319; distribution of, in
Bryozoa (see Polyzoa).                         time, 337.
Bubalus, 568.                                Carinatoe, 473.
Buccinidce, 313, 317.                        Carnivora, 513, 516, 522, 525; general
Buccinum, 305, 314, 317.                        characters of, 573; divisions of, 573,
Buceridoe, 496.                                 574; distribution of, in time, 616.
Buceros, 497.                                Carpenteria, 57, 60.
Buffalo, 568.                                Carriage-spring apparatus (Brachiopeoda),.3ufo, 414, 416.                                294.
BluforLidoe, 416.                             Carteria, 122.
Bulbus arteriosus, 372, 382, 890, 394.        Caryocaris, 234.
Buli'maus, 319.                               Cassidina, 226.
Beella, 319.                                  Cassidulida, 150.
Bzcllidce, 314,- 319.                         Cassis, 317.
Bursaria, 75.                                Cassowary, 464, 486.
Bustards, 464.                               Castor, 589.
Butterflies, 265, 266.                       Castoridve, 589.
Byssus (of Lamellibranchiata), 305.          Casuarius, 486.
Catarhina, 600, 603.
CACHALOT, 549.                               Catodontidce, 545, 548.
Caducibranchiata (Amphibia), 407, 408,   Cats, 516, 583, 585.
410, 411.                                  Cavia, 588.
Caeca, intestinal (of Birds), 466.           Cavicornia, 561, 565.
Cneca, pyloric (of Fishes), 373.              Cavidwe, 588.
Ccecilice, 409, 410.                         Cebidre, 602.
Caiman, 444.                                 Cebus, 602.
Calan.aries, 329.                            Cells, of Polyzoa, 280, 282.
Calcarea (Sponges), 67.                      Cellulose, in Ascidians, 9, 287.
Calceola, 128, 297.                          Cement-gland, of Cirripedes, 211, 211,
Calcispongice, 67, 70.                       Centetes, 597.
Calice (Corals), 120.                        Centipedes, 245, 246.
Callianiridoe, 134.                          Centrocercus, 489.
Calling Hares, 588.                          Cephalaspis, 393, 403.
Callithrix, 602.                             Cephalobranchiata (see Tubicota).
Callograpsus, 113.                           Cephalopoda, 275, 276, 277, 300; general
Callorhy'nchus, 397.                           characters of, 322; arms of, 322, 323;
Callymidoe, 134.                               suckers of, 323; funnel of, 323; ink-bag
Calycophoridce, 93;  polypites of, 94;          of, 324; mandibles of, 323; digestive
pyloric valve of, 94; tentacles of, 94;      system of, 324; branchire of. 324; nerreproduction of, 95; development of,         vous system of, 324; vascular system of,
95; distribution of, 112.                    324; reproduction of, 324-326; skeleton
Calyptrcea, 318.                               of, 326, 327; divisions of, 327; distribuCalyptrceidce, 314, 318.                       tion of, in time, 337, 338.
Calyx (of Vorticella), 72; (of Crinoids),   Cephalophora (Mollusca), 300.
156, 163.                                  Cephaloptera, 399.
Camelidoe, 509, 519, 560, 561.               Cephalothorax, of Crustacea, 202; of Ar
Camelopardalidoe, 561, 565.                    achnida, 235.
Camelus, 561.                                Cephaluna, 209.
Campanularia, 91.                            Cephea, 110.
Camnpanulasrida, 83, 92; medusiform go-   Cerastes, 432.
nophores of, 92.                           Ceratiocaris, 234.
Canals, of Sponges, 65; of Alcyonaria,   Ceratites, 333, 335, 337.
125; of Ctenophora, 131, 132, 133.         Ceratodus, 401.
Cancroma, 483.                              Cercolabes, 589.
Canidoe, 582.                                Cercoleptes, 579.
Canis, 582, 583.                             Cere, of Birds, 464, 471.
Capitulum (Lepadidee), 211, 213.             Cerianthus, 117, 133.
Capra, 567.                                  Cerithiadce, 313, 317.
Calpreolus, 564.                             Cerithium, 317.




656                                    INDEX.
Certhia, 499.                                 Ciconia, 483.
Certhidoe, 499.                              Ciconince, 483.
Cervidce, 561, 562, 563, 614.                 Cidaridoe, 150.
Cervus, 564..                                Cidaris, 146.
Ceryle, 501.                                 Cilia, of Sponges, 65; of Infusoria, 70, 71;
Cestidce, 134.                                 of Actinozoa, 114; of Ctenophora, 130,
Cestoidea (see Tceniada).                      131; of Echinus, 149; of Annelides,
Cestracion, 397, 404.                           189.
Cestraphori, 397, 404.                       Ciliata (Infusoria), 70.
Cestum, 134.                                 Cinclides, 118.
Cetacea, 510, 511, 512, 513, 514, 515, 519,   Cinulia, 318.
520, 521, 522, 525; general characters of,   Cirrhi, of Annelides, 188; of Cerripedia,
544; groups of, 545; distribution of, in     211, 213; of Brachiopoda, 294; of Lantime, 613.                                   celet, 376, 377.
Cetiosaurus, 445.                            Cirrhopoda (see Cirripedia).
Chceropotamus, 614.                          Cirripedia, 207, general characters of,
Chceropus, 535.                                210, 211; development of, 211, 212;
Chcetognatha, 198, 199.                        shell of, 211, 212, 213; reproduction of,
Choetonotus, 180.                              213, 214; divisions of, 214; distribution
Chalcidee, 437.                                of, in tinme, 233.
Chama, 306.                                  Cirrostomi, 376 (see Pharyngobranchii).
Chameleo, 441.                               Civet, 581.
Chameleontidce, 441.                         Cladocera, 208; characters of, 217, 218.
Chamidce, 306.                               Clamatores, 488.
Charadriidce, 484.                           Clangula, 479.
Cheilostomata, 286, 298                      Classification, 19.
Cheiromydce, 600.                            Clausilia, 319.
Cheironys, 600.                              Clavellinidce, 291.
Cheironectes, 535.                           Cleodora, 320.
Cheiroptera, 522, 526; general characters,   Clepsine, 191, 198.
592, 593; divisions of, 594; distribution   Cliidoe, 321.
of, in time, 617.                          Climacograpsus, 118.
Cheirotheriumn, 417.                         Clio, 321.
Chels, 206; of King-crab, 221; of Scorpion,   Cliona, 68.
236, 242; of Book-scorpion, 241.           Clitellum, 191.
Chelicerse, 236, 242.                        Cloaca, of Rotifera, 182; of.lnsecta, 252;
Chelichnus, 428.                               of Tunicata, 288; of Amphibia, 406,
Chelifer, 241.                                 408; of Reptiles, 421; of Birds, 466; of
Chelonia, 423; general characters of, 423,     Monotremes, 523, 527.
424; subdivisions of, 426; distribution   Clotho, 433.
of, in time, 428.                          Clupeidoe, 385.
Cheloniidce, 426, 428.                       Clypeastridce, 150.
Chelonobatrachia, 413 (see Anoura).          Clytia, 88.
Chelydidge, 424.                             Cnidle, 80.
Chelydra, 427.                               Coati, 579.
Chemnitzia, 317.                             Coccidce, 260.
Chilognatha, 247.                            Coccoliths, 58
Chilopoda, 246.                              Coccospheres, 58, 59.
Chimera, 246, 247.                           Coccosteus, 385, 393, 408.
Chimceridce, 396.                            Coccothraustes, 498.
Chimpanzee, 606.                             Coccus, 259.
Chinchilla, 588.                             Cocoon, 256.
Chirotes, 435, 437.                          Coelenterata, 16, 77  characters of, 78;
Chiton, 277, 318.                              thread-cells of, 80; divisions of, 80.
Chitonidee, 314, 318.                        Coelogenys, 588.
Chlamydosaurus, 441.                         Ccenenchyma, 120.
Chlanayphorus, 539, 540.                     Ccencecium, 280, 282.
Chlorophyll in animals, 9.                   Ccenosarc, 82; of Oceanic Hydrozoa, 93;
Cholcepus, 539.                                 of Physalia, 100; of Velella, 100.
Chondropterygidcsm, 376, 394.                Coleoptera, 249, 254; mouth of, 250; charChondrosteus, 403.                              acters of, 271; sections of, 273.'Chonetes, 297.                               Collospheera, 62, 63.
Chorda dorsalis (see Notochord).              Colobus, 603.
Chromatophores, 322.                          Colossochelys, 428.
Chrysalis, 256                                Coluber, 433.
Chrusochloris, 596.                           Colubrina, 431, 433.
Chylaqueous Canals (Medusoe), 101.           Columba, 491.
Cllylaqueous fluid, of Rotifera, 182; of   Columbacei, 488, 490.
Annelida, 188, 195.                        Columbidee, 491.
Chylific stomach, of Insects, 252.           Colunlella, of Corals, 120; of the shells of
Chyme-mass, of Infusoria, 71.                   Gasteropoda, 312.
Cicada, 260.                                 Column, of Actinidce, 117.




INDEX.                                    657
Colymbidf, 477.                             Cryptochiton, 318.
Colymbus, 477.                              Cryptoniscus, 226.
Comarocystites, 159.                        Cryptophialus, 215.
Comatula, 157, 158; distribution of, in   Crystalline stylet, 303.
time, 163.                                Ctenocyst, 132.
Compsognathus, 451.                         Ctenodiscus, 151.
Conchifera, 300 (see Lamellibranchiata).   Ctenoid, scales of Fishes, 362.
Condylura, 596.                             Ctenophora, 115, 116; characters of, 130;
Conidee, 313, 317.                            homologies of, 133; divisions of, 134;
Conirostres, 496.                             distribution of, 135.
Conocardium, 307.                           Ctenophoral canals, 132, 133.
Conodonts, 403.                             Ctenophores, 130, 131.
Conovuclus, 319.                            Ctenostomata, 280, 287.
Contractile vesicle, of Protozoa, 45; of  Cuckoo, 493.
Amcaeba, 50; of Paramociurm, 71; of  Cuculidce, 493.
Vorticella, 73; of Epistylis, 75.        Cucullcea, 306.
Conularia, 321, 337.                        Culex, 265.
Conus, 317.                                 Culicidce, 264.
Coot, 481.                                  Cultellus, 307.
Copepoda, 208; characters of, 217.          Cultirostres, 481.
Coral, 119 (see Corallum).                  Curlew, 483.
Corallite, 120.                             Cursores, 468, 473; characters of, 484.
Corallium, 128, 135, 139.                   Cuticle, of Amceba, 50; of Infusoria, 71;
Corallunl, 119; distinctions between dif-    of Noctiluca, 76.
ferent corallJ, 129.                      Cuttle-bone, 326, 329.
Coral-reefs, 135-138.                       Cuttle-fishes, 322, 323, 324, 325, 327.
Cordylophora, 85, 86, 88; gonophores of,  Cyamus, 224.
86; distribution of, 112.                 Cyanea, 107, 110.
Cornulites, 197.                            Cyathaxonidee, 138.
Cortical layer, of Irtnfsoria, 71; of Noc-   Cyathophyllidoe, 138.
tiluca, 76.                               Cycladidoe, 307.
Corvidce, 496, 497.                         Cyclas, 304, 307.
Coryne, 86, 88.                             Cycloid, scales of Fishes, 362.
Corynida, 83; characters of, 85; repro-  Cyclolabridce, 387.
duction of, 86-88; types of, 89, 90; de-   Cyclophorus, 319.
velopment of, 89; distribution of, 112,  Cyclophthalmus, 244.
113.                                      Cyclopoidea, 203.
Corynoides, 113.                            Cyclops, 217.
Coryomorpha, 85, 90.                       Cyclostoma, 319.
Coturnix, 489.                             Cyclostomata (Polyzoa), 287, 298; (Fishes),
Coypu, 589.                                   378.
Cracidce, 490.                             Cyclostomi (Fishes), 378:
Crane, 482.                                Cyclostotnidce (Gasteropoda), 317, 319.
Crane-fly, 265.                             Cydippe, 130.
Crania, 293, 297, 298.                      Cygnidve, 379.
Craniadce, 295, 297.                        Cygnus, 379.
Craspeda, 118.                              Cylichna, 319.
Crax, 490.                                 Cymothoa, 226.
Crex, 481.                                 Cynocephalus, 604
Cribella, 151, 152.                        Cynomys, 592.
Cricetsus, 590.                            Cynthia, 288.
Crinoidea, 143, 144; general characters   Cypreea, 317.
of, 155-157; distribution of, in space,   Cyprceidce, 313, 317.
162; in time, 163; structure of calyx in   Cypridina, 216.
fossil forms of, 163.                    Cyprina, 307.
Crioceras, 333, 334.                       Cyprinidce (Mollusca), 307; (Fishes), 385
Cristatella, 281, 282.                     Cypris, 216.
Crocodilia, 420, 421, 422, 423; general  Cypselidoe, 500.
characters of, 442; divisions of, 443;  Cyrena, 307.
distribution of, in time, 444, 445.      Cyrtia, 296.
Crocodilus, 443, 444.                      Cyrtoceras, 333, 335, 337.
Crop of Insects, 252; of Birds, 464.       Cyrtolites, 337.
Cross-bill, 498.                           Cysticerci, 169, 170.
Crossopterygides, 390.                     Cystic Worms, 166, 168, 170.
Crotalidce, 432.                           Cystiphyllidce, 138.
Crotalus, 432.                             Cystiphyllum, 129.
Crust, of Crustacea, 201; of Trilobites, 219.  Cystoidea, 144; general characters of,
Crustacea, 200; general characters of,    158; distribution of, in time, 164.
200, 201; Morphology of a typical Crus-  Cythere, 216.
tacean, 204-207; divisions of, 207, 208;  Cytherea, 307.
distribution of, in space, 233; in time,
233, 234.                                Dacelo, 501.




658                                 INDEX.
Dactylethra, 416.                         Dicynodontia, 448.
Dactylopterus, 369.                       Didelphia, 523, 529.
Dafila, 379.                              Didelphidce, 529, 535.
Dakosaurus, 445.                          Didelphys, 529, 535, 610.
Dauma, 564.                               Didunculus, 492.
Dacphnia, 218.                            Didus, 491.
Darwinian Theory, 40.                      Didymograpsus, 113.
Dasypodidoe, 537, 539.                    Difflugia, 51.
Dasyprocta, 588.                          Digitigrada, 574, 580.
Dasypus, 539.                             Dimorphodon, 450.
Dasyurus, 536.                            Dimyaria, 305.
Decapoda (Cruestacea), 227; distribution   Dinophis, 435.
of, in time, 234; (Cephalopoda), 328,  Dinornis, 507, 508.
329.                                    Dinosauria, 450, 451.
Decollated shells, 278.                   Diomedea, 477.
Deer, 561, 563, 564.                      Diphydce, 96.
Deinosauria (see Dinosauria).             Diphyes, 96.
Deinotherium, 569, 572, 616.              Diphyllidia, 319.
Delphinidce, 549, 551.                    Diphyozobids, 95.
Delphinula, 318.                          Diplcacanthus, 403.
Delphinus, 550.                           D iplodonta, 307.
Demodex, 241.                             Di'plograpsus, 112, 113.
Dendrocoela, 174.                         Diplostomum, 173.
Dendrograpsus, 111, 118,                  Dipnoi, 399, 403; general characters of;
Dendrolagus, 532.                           399-401.
Dendrophyllia, 121.                       Dipodidoe, 590.
Dendrostyles, 109..Diprotodon, 611.
Dental formula, 518.                      Diptera, 252, 256; mouth of, 252; charDentalidce, 314, 318.                       acters of, 264.
Dentalina, 55.                            Dipterus, 403.
Dentalium, 318; shell of, 811; position   Dipuss, 591.
of, 318.                                Discina, 297, 298.
Dentirostres, 496, 498.                   Discinidre, 295, 297.
Development, 34; Retrograde, 25; of  Discophora (Medustc), 83; characters of,
Gregarinidre, 47; of Foraeinifera, 55;    100-103.
of Hydra, 85; of Corynida, 89; of  Discophora (Leeches) —see Hirudinea.
Sertularida, 92; of Calycophoridce, 95;  Dissepiments of Corals, 123.
of Physophoridee, 98; of Medusidoe,  Distal, 81.
103; of Lucernarida, 106, 107, of Ac-   Distonma, 172, 173.
tinidce, 118; of Pleurobrachia, 132; of  Distribution, geographical, 40; bathyEchinodermata, 142-144; of Eehin-    metrical, 41; geological, 42.
oidea, 144; of Asterozdea, 152, of  Dithyrocaris, 234.
Ophiuroidea, 154; of Comrnatula, 158;  Dodo, 491, 492, 508.
of Holothuroidea, 160; of Toeniada,   Dog, 516, 582, 583.
167-170; of Trematoda, 172; of Nemer-  Dog-fishes, 397.
tida, 175; of Acanthocephala, 176; of  Dolabella, 319.
Trichina, 178; of thle Guinea-Worm,  Doliolumn, 290.
178; of Tubicolar Annelides, 193; of  Dolphins, 510, 514, 521, 544, 549, 550, 613.
Errant Annelides, 196; of Crustacea,  Donasx, 307.
202; of Ichthyophthira, 209; of Rhizo-   Dorcatherium, 614.
cephala, 210; of Cirritpedia, 211; of  JDoridce, 314, 319.
Copepoda, 217; of Ostracoda, 216; of  Doris, 315, 319.
Phyllopoda, 218; of Trilobita, 220; of  Dormice, 591.
Linmulus, 222; of Isopoda, 225; of Am-   Dorsal vessel, of Insects, 253.
phipoda, 224; of Stonzapoda, 227; of  Dorsibranchiata, 195 (see Errantia).
Macrura, 228; of Anomura, 231; of  Draco, 441, 450.
Brachyuroa, 232; of Myriapoda, 246;  Dracunculus, 178.
of lnsec'a, 254, 255, 256; of Polyzoa,   Dreissena, 306.
286; of Ti-unicata, 290; of Brachiopoda,   Dromaisus, 486.
295; of LIaoellibranchiata, 304; of  Dromatheriurn, 609.
Gasteropodt., 311; of Amphibia, 406-  Dromedary, 561.
408.                                    Dronmia, 231.
Dextral shells, 278.                      Dryopithecus, 617.
Dibsranchiata (Cephalopoda), 327; cha-  Duck, 471, 479.
racters of, 327; divisions of, 328; dis-  Duck-mole, 511, 512, 517, 520, 523, 527,
tribution of, in time, 338.                528.
Diceras, 3(16.                             Dugong,. 510, 524, 542, 543.
Dicoryle, 89.                             Dytiscidoe, 257.
Dicotyles, 557, 618.
Dicranoyraps-us, 118.                      EAGLE, 503.
Dictyolnema, 113.                          Ecderon, 114.
Dicywndon, 448.                            Echidna, 512, 517, 529, 521, 524, 528, 529.




INDEX.                                    659
Echinidda, 150.                             Epistylis, 74.
Echinococci, 171.                           Epizoa, 207; characsters of, 208
Echinoconidce, 150.                         Equidwe, 555.
Echinodermata, 141; general characters   Equus, 555, 613.
of, 142; development of, 143; divisions   Erethizon, 589.
of, 144; distribution of, in time, 163-   Erichthys, 227.
165.                                      Erinaceidoe, 597.
Echinodon, 441..Erinaceus, 597.
Echinoidea, 143; characters of, 144-150;  Errantia, 189; characters of, 194; gemtest of, 144; ambulacral system of, 147;    mation of, 196; development of, 196;
digestive system  of, 148; families of,     distribution of, in time, 197.
150; distribution of, in space, 162; in   Esocidce, 385.
time, 164.                                Evtdendrium, 89.
Echinoneidce, 150.                          Eugereon, 273.
Echinorhynchus, 176.                        EuliMna, 317.
Echintozoa, 141 (see Annuloida).            Esinice, 197.
Echinus, 146, 147, 148.                     Eunicea, 197.
Echizurus, 186.                             Euosmphalus, 318.
Ectocyst, 282.                              Euplectella, 68.
Ectoderm, 79, 114.                         Eupsamrnidce, 140.
Ectosarc, 50.                              Euryale, 154.
Edaphodus, 397, 405.                       EEurypterida, 223; distribution of, in
Edentcita, 513, 520, 522, 524; general    time, 234.
characters of, 537; distribution of, in   Eurypterus, 234.
time, 6 11.                              Exoccetus, 369.
Edriophthalmata, 208; characters and   Exopodlite, 204.
divisions of, 223.                       Extracrinus; 163.
Elasmobranchii, characters of, 394, 395;
divisions of, 395; position of, in the   FACIAL Suture of Trilobites, 220.
scale of Fishes, 399; distribution of, in   Falconidoe, 503.
time, 404.                                Favositidoe, 139.
Elasmoodsuws, 397, 405.                     F avospongia, 68.
Eledone, 335.                               Feathers (structure of), 454, 455.
Elephant, 514, 520, 525.                    Feather-star, 157.
]Elephant-shrew, 597.                       Felidce, 513, 583, 585.
Elephas, 570, 571, 615.                     Felis, 584, 585..,lysia, 319.                               Fenestella, 298.
Ilysiadce, 315, 319.                        Ferce, 573.
Elytra, of Aphrodite, 195; of Coleoptera,  Fliber, 589.
250, 271.                                Field-bug, 259.
Ernarginula, 318.                          Filaria, 178.
Emeu, 486.                                 File-fishes, 388.
Enzydidce, 427, 428.                       Finches, 497, 498.
Emys, 427.                                 Finner-whales, 548.
Enaliosauria, 446.                         Firola, 319.
Enallostega, 57.                           Firolidoe, 316, 319.
Encephala (Mollusca), 300, 308.            Fissilignguia, 436.
Encrinus, 163.                             Fissioni, 25, 27; of corals, 124.
Enderon, 114.                              Fissirostres, 496, 500.
Endocyst, 282, 283.                        Fissurella, 318.
Endoderm, 79, 114.                         Fissuirellidre, 314, 318.
Endopodite, 204.                           Flagella, 45, 76.
Endosare, 50.                              Flagellata (Infusoria.), 70, 76.
Endostyle, 289.                            Flamingo, 479.
Enhydra, 581.                              Flat-fishes, 364, 386, 398.
Entomostega, 57.                           Flints, origin of, 69.
Entomostraca, 208; characters of, 215;  Float of Physophoridce, 97.
divisions of, 215.                       Floscularia, 180, 183.
Entosolenia, 55.                           Flukes (Suctorial worms), 171.
Entozoa, 165.                              Flustra, 9, 26, 283.
Eocystites, 164.                           Flying-Dragon, 441.
Eosaurus, 446.                             Flying-Lemur, 598.
Eozoon, 59.                                Flying-Squirrel, 591.
Ephemeridce, 261.                          Food of animals and plants, 10.
Ephyra, 107.                               Food-vacuoles, 50, 71, 75.
Epidermis (of the shell of Mollusca), 278.   Foot, of Rotifera, 181; of LamellibranEpimera, 203.                                chiata. 304; of Gasteropoda, 309; of
Epipodite, 206.                              Heteropoda, 315; of Pteropoda, 320;
Epipodium, 309; of Pteropoda, 320; of    of Cephalopoda, 323.
Cephalopoda, 323.                        Foot-jaws, of Lobster, 206; of Centipedes,
Episterna, 204.                              246.
Epistome, 2S4, 286.                        Foram.niifera,     3, 26, 46, 53; sarcode of,




66o                                   INDEX.
53; pseldopodia of, 54; test of, 53, 54;   Generations, alternation  of, 28-31; of
unilocular and multilocular, 55; stolons     Salpians, 290.
of, 55; classification of, 56; affinities of,   Generation, spontaneous, 36-38.
57; distribution of, in space and time,   Genette, 581.
59, 60.                                    Geocorisoe, 260.
lI'orficula 250.                            Geomelania, 319.
Formicidce, 269.                             Geophilus, 246.
Fowl, 489.                                   Gephyrea, 185, 186.
Fox, 582, 5S3                                Gerbillus, 591.
Fox-bats, 595.                               Gibbon, 605.
Francolinus, 489.                            Giraffe, 510, 561, 565, 614..Fratercula, 476.                            Gizzard, of Insects, 252; of Birds, 485.
Fringilla, 498.                              Glabella, 220.
F'ringillidoe, 497, 498.                     Gladius (Cuttle-fishe), 326, 329.
Frilnging-reefs, 135.                        Glareola, 484.
Frog, 414, 417; development of, 415.         Glaucus, 319.'u.lgora, 260.                               Gtires, 586 (see Rodentia),
Fulica, 481.                                 Globicephalus, 550.
FsUligulCa, 479.                             Globigerina, 54, 56.
Fuligalince, 479.                            Glycimeris, 307.
Functions, specialisation of, 13-15.         Glyptodon, 612, 618.
Fungidce, 140.                               Glyptolepis, 403.
Funiculus, of Polyzoa, 285.                  Goat, 567
Funnel, of Clenophora, 131; of Ceophalo-   Goat-sucker, 495, 500.
poda, 323; of Nautilus, 332.               Gobiidce, 387.
Furculum. 460.                               Goniaster, 153, 164.
Futsuus, 317.                                Goniatites, 333, 338.
Goniodiscus, 164.
GADIDAE, 386                                 Goniophyllum., 129.
Galeocerdo, 405.                             Gonoblastidia, 88, 89.
Galeodes, 236, 241.                          Gonocalyx, 87; structure of, 87, 88
Galeo2piihecedo, 597.                          canals of, 87.
Galeoplithecus, 598                          Gonophores, 86, 87; medusiform, 87, 88,
G,ls'es, 610.                                92, 95, 98, 102, 103, 110.
Galllnacei, 488.                            GonosoIne, 82.
Gallince, 487.                               Gonotheca, 92.
Gallinutce, 481.                             Gordiacea, 165; characters of, 176.
Gallus, 489.                                 Gordius, 176.
GamnearugS, 225.                             Gorgonidce, 125, 129, 135; characters of,
Ganasidce, 240.                                127; distribution of, in time, 139.
Gannet, 478.                                 Gorilla, 606.
Ganoduzs, 405.                               Gostridce, 491.
Ganoid (Scales of Fishes), 362.              Gratllatores, 473; characters of, 480.
Ganoidei, charac(ters of, 388; divisions of,   Grantia, 67.
391, 392; distribution of, in time, 403.    Graophularia, 139.
Garrulinoe, 497.                             Grcapolitidce, characters of, 110-112; disGasteropoda, 274, 275, 276, 300; general       tribution of, in time, 113.
characters of, 308-311; foot of, 309;   Greenland Whale, 545.
odontophore of, 309; circulatory and   Gregarina, 46.
respiratory organs of, 310; embryo of,   Gr-egarinidce, 46, 47; reproduction of, 47.
311; shell of, 311; divisions of, 313-317;   Grigithides, 234.
families of, 317-319; distribution of, in   Grison, 579.
time, 336.                                 Gromia, 53.
Gastornis, 507.                              Gromida, 56.
Gastrobranchus, 381.                          Growth, 3, 25; correlation of, 18.
Ga.strocblt a, 3(18.                          Gruidce, 482.
Gastr..:c;/(eidwe, 306, 308.                 Grus, 482.
Gavial, 442, 444.                             Gryllina, 260.
Gavi'as, 444.                                Guard, of Belemnite, 330, 335.
Gecarcinus, 228, 232.                         Guinea-fowl, 489.
Geckotidce, 439.                              Guinea-pig, 588.
Geese, 479.                                   Guinea-worm, 178.
Gelasimus, 232.                               Gulo, 579.
GeSnitores, 488, 490.                         Gymnodontidce, 388.
Gemlnation, continuous and discontinu-   Gymnolcemata, 286.
onus, 25-27; internal, 28; of Foramin-   Gymnophiona, 409.
ifera, 55; of Vorticella, 73; of Hydra,   Gymnophthalmata (AMedusidce), 88, 100,
84; of medusiform gonophores, 103; of         110.
corals, 123; of NYdidide, 192; of Errant   Gymnnosonmata, 321.
Annelides, 196; of Polyzoa, 279, 281;   Gymnotus, 384.
of Tunicata, 290.                          Gynophores, 98.
Gemmules, of Spongilla, 66.                   Gypaetos, 504.




INDEX.                                     66i
GTyrencephala, 522.                            160; families of, 162; distribution of,
Gyroceras, 333.                                in space, 162; in time, 165.
Homocercal (tails of Fishes), 371.
Hcenzatocrya, 360.                           Homology, 17; serial, 17.
Ilemnatopus, 484.                            Homomorphism, 18.
Hoematothermna, 360.                         ilomnoptera, 259.
Hag-fishes, 378, 379, 380, 381.              Honey-eater, 499.
Ilaimeia, 125.                               Hoopoe, 499.
Hair-worms, 176.                             Horn-bill, 496.
Halcyornis, 507.                             Horse, 514, 516, 555, 613,
Halicore, 542, 543.                          Humming-birds, 499.
Haliomma, 61.                                Hunting-dog, 582.
llaliotidce, 314, 318.                       Hycena, 582, 616.
Haliotis, 318.                               Iiycenidwe, 581.
Htalitherium, 612.                           Hyalea, 321, 337.
Halteres, 250, 264.                           lyaleadke, 321.
Hamites, 338.                                Hyalochaetide, 122.
Hamster, 590.                               tHyalonema, 67.
Hapale, 602.                                 lyalonemadoe, 122, 129.
Ilapalidce, 602.                            tlybodws, 397.
Harpa, 317.                                  Hydatids, 168, 171.
Hlaustellata, 208 (see Epizoa).             HIydatinsa, 181.
Hlawks, 503.                                iydra, 26, 27, 28, 80, 81; structure of,
Hectocotylus, 325, 328.                        83; reproduction of, 84, 85; threadHedgehollg, 521, 597.                         cells of, 80; development of, 85; disHelarcto-s, 578.                               tribution of, 112.
Helianthoid Polypes, 116.                   Iydrachnidce, 240.'
Ilelicidce, 317, 319.                       Hydractinsia, gonophores of, 86, 89.
Helicoidea, 57.                             Hydra-tuba, 30, 106, 107.
Helicostega, 57.                            Hydrida, 83.
Helix, 319.                                 Hydrocaulus, 90.
Ifelladotherium, 565, 614.                  Hydrochcerus, 588.
Hemelytra, 250, 260.                        Elydrocorisce, 260.
Hemeristia, 273.                            Hydrocysts, 97.
Hernicardiuzm, 307.                         Hydrcecium, 95, 96.
HeminLetabola (Insecta), 254, 258.          Hydroida, characters and divisions of,
Herniptera, 252; characters of, 259.          83; reproduction of, 86, 89; distin~
lIeptatrema, 381.                             guised from Polyzoa, 279, 280.
Hermit-crab, 231.                           Hydroid Zoophytes (see Hydroida)
Heron, 482, 483.                            Hydrophidoe, 434.
Herpestes, 581.                             HIydrophilidce, 257.
Heterocercal (tail of fishes), 371.         HIydrolhyllia, 95j 97.
Heterogeny, 37.                             Hydrorhiza, 83.
Rleteromastix, 76.                          Hydrosoma, 81.
lIeterowzera, 273.                          Hydrotheca, 85, 90.
Heterophagi, 469.                           Hlydrozoa, 79, 80, 81, 82; characters of,
Heteropoda, 313; characters of, 315;          80; terminology of, 81; divisions of,
shell of, 315; divisions of, 316; dis-      83; reproduction of, 86, 89; Oceanic,
tribution of, in time, 336, 337.            93; distribution of, in space and time,
Heteroptera, 260.                             112, 113.
Hexaprotodon, 614.                          Hyla, 407, 414.
Himantopus, 484.                            Hylobates, 605.
Hipparion, 613.                             Hymenocaris, 234.
Hippobosca, 265.                           fIymenoptera, 256, 267, 268.
Hlippocampidoe, 388.                        Hyoid arch (Fishes), 366, 367.
Hippocrepian Polyzoa, 284.                  Hyopotamus, 614.
Hiippohyuts, 614.                          Ifyponome, 158.
HIippopotamides, 556, 614.                  Hypostome, of Trilobites, 219.
Ilippopotamns.s, 556, 614.                  Hypsiprymnnus, 531, 533.
Ilippurites, 306.                           Hyracoidea, 525; general characters of,
1iippuritidce, 306.                           5068.
Hirudinea, 188; general cnaracters of,  HyJrax, 569.
189, 190.                                iHystricidoe, 588.
Hirundntidc, 500.                         HIystrix, 588.
Holocephal, 395; characters of, 396.
1lolocystis, 128, 139.                      Ianthina, 318.
Holometabolo ( Insecta), 255, 264.          Ibis, 483.
IHoloptychius, 403.                         Ichneumon (Insecta), 268.
Ilolostomnata (acsteropoda), 312, 313, 317.  Ichtlhyodorulites, 385, 396, 404.
Holothuria, 1;0, 161, 162.                  Ichthyomnorpha, 410.
Iolothuridce, 1(52                          Ichthyophthira, 207, 209.
lolothuroidea, 143, 144; characters of,  Ichthyopsidca, 360.




662                                   INDEX.
lchthyopterygia, 423; characters of, 445,   Labrum, of Lobster, 206; of Trilobites,
446.                                         219; of Scorpion, 236; of lnsecta, 250.
lchthyosauria, 445.                          Labyrinthodontia, 417, 418.
lchthyosattrus, 446, 448.                    Lacerta, 439.
Idothea, 226.                                Lacertidce, 438.
Iguana, 440, 451.                            Lacertilia, 413, 423; general characters
lguanidoe, 440.                                of, 435, 436; families of, 437-441; disIguanodon, 451.                                tribution of, in time, 441.
lyanthidce, 118.                             Lcemoelipoda, 208; characters of, 224.
Ilyanthus, 118.                              Lagenc, 55.
Imago, 254.                                  Lagolnys, 5S8.
imperforata (F'orarninifera), 58, 56.        Logopus, 489.
Implacentalia (Marimmalia), 522.             Lamellibranchiata,  274, 276; general
Individuality, general definition of, 27;       characters of, 300; shell of, 801; diin Sponges, 69.                              gestive  system   Qf, 302; circulatory
Infundibulum, of Cephalopoda, 323.             systeml of, 303; mantle of, 302; branIhsfusoria, spontaneous generation of, 87,     chive of, 303; reproduction  of, 304;
38; characters of, 70; divisions of, 70;     muscles of, 304; habits of, 305; diviaffinities of, 77; Ciliated, 70; Suctorial,  sions of, 305; families of, 306-3 8;
75; Flagellate, 76; Compared  with           distribution of, in time, 336.
Rotifera, 183.                             Lamellirostres, 478.
Inia, 551.                                   Lamplrey, 372, 378, 379, 380.
Innoceta (Ophidia), 413.                     Lanlllls hells, 292.
Inocerarmus, 306.                            Lant elct, 34S, 356, 358, 371, 8'3, 376;
Inoperculata, 316, 319.                        tInatoIy of, 376, 377.
Jnsecta, 200; general characters of, 248-   Land-salamnandemrs,   413.
257; organs of the mouth  of, 250;   Laniidws, 498.
wings of, 249; digestive systenl  of,  Loeredea, 193.
252; tracheae of, 253; circulation of,   Laornis, 507.
253; metamorphoses of, 254; partheno-   Laridce, 477.
genesis of, 31-34; sexes of, 256; orders   Lark, 497.
of, 257-272; distribution of, in time,   Larva, of Echinodermanta, 143, 144; of
273.                                         Echinoidea, 144; of Asteroidea, 151,
Insectivora, 522, 526; general characters      152; of Ophiuroidea, 154; of Crinoiof, 595; families of, 596; distribution      dea, 155, 158; of Holothuroidea, 160;
of, in time, 617.                            of Tceniada, 168, 170, 171; of Tremainsessores, 474; characters of, 495; see-    toda, 172; of Nemertida, 174; of Acantions of, 496.                               thocephala, 176; of Ichthyophthira,209;
Integro-pallialia, 303, 305, 306.              of Rhizoeephala,210; of Cirripedia, 211;
Invertebrata, general characters of, 346,      of Limulus, 222; of Macrura, 228; of
347.                                         Brachyura, 232; of Myriapoda. 246; of
Ischiodus, 397, 405.                           lansecta, 254, 255; of Tunicata, 290; of
Isis, 121, 128.                                Brachiopoda, 295; of LamellibranchiIsocardia, 307.                                ata, 304; of Gasteropoda, 311; of AmIsopoda, 208; characters of, 225; develop-     phibians, 406, 407, 415.
ment of, 225; distribution of, in time,   Leech, 189, 190, 191.
234.                                       Lemu.tridce, 601.
Ilulus, 247.                                 Leopard, 585.
Ixodes, 240.                                 Lepradidce, 207, 211; characters of, 213;
Ixodidce, 240.                                 distribution of, in time, 234.
Lepas, 212.
JAGUAR, 585.                                 Lepidoganoidei, 391, 403.
Jelly-fishes, urticating  powers of, 100;   Lepidcptera, 256; nmouth of, 251; charnature of, 102; former classification of,    acters of, 265.
100.                                       Lepidosiren, 373, 374, 379; characters of,
Jerboa, 590, 591.                              400, 401.
Jumping Hare, 591.                           Lepidosteus, 363, 389, 391.
Jumping Mouse, 591.                          Lepidota, 408 (see Dipnoi)
Lepisma, 258.
KANCAROO, 529, 531, 532.                     Leporidce, 588.
Kangaroo-rat, 531, 533.                      Leptcena, 296.
Kellia, 307.                                 Leptidce, 240.
Keratode, 64.                                Leptocardia, 376  (see  Pharyngobrau.
Keratosa (Sponges), 67.                         chii).
King-crabs, 221, 223.                        Lep~us, 588.
Kinkajol, 579.                               Lernoea, 36, 209..Rolinclria, 296.                            Libellulidoe, 261.
Knsinckiadce, 296.                           Lieberkuhnia, 53.
Ligia, 226.
LABRTIU.r, of Lobster, 206; of Arachnida,   Ligula, 251.
236; of lnsecta, 250, 251, 252.            Limnacidce, 319.




INDEX.                                    663
Limacina, 321.                             Macrauchenia, 618.
Limacinidms, 321.                          Macrobiotidce, 239.
Limax, 316, 319.                           Macrodactyli, 481.
L imicolce, 191.                            Macropodidce, 531.
Lirnnadia, 219.                            Macropus, 529.
Limncea, 319.                               Macroscelides, 597.
Lim nceidce, 317, 319.                      Macrospondylus, 445
Limnoria, 226.                              Macrotherium, 612.
Limosa, 483.                                Macrura, 228; characters of, 228-230.
Limulus, 221, 222, 234.                     Mactra, 307.
Lingua (Insects), 2.51..Mactridce, 306, 307.
Linaual Ribbon (Alollusca), 309.            Madreporidce, 140.
Linguatulina, 239.                          Madreporiform  tubercle, of EchinoderLingula, 293, 296, 297.                       mata, 143; of Echinoidea, 146; of AsLingulidce, 295, 297.                         teroidea, 151; of Ophiuroidea, 154; of
Lion, 574, 584, 616.                          Holothuroidea, 161.
Lissencephala, 522.                        MHalacodermata (Zoantharia), 116, 117,
Lithobius, 246.                               134, 139.
Lithocysts, 104, 108.                      Malacopteri, 383.
Lithodomi, 305.                            Malacopterygii, 376, 382,
Lithornis, 507.                            Malacostraca, 223.
Littorina, 313, 318.                       Malapterurus, 385.
Littorinidee, 314, 318.                    Mallophaga, 258.
Lituites, 333, 335.                        Malpighian tubes, of Insects, 237, 252.
Lituovlida, 56.                             Mammalia, 352, 3594 general characters
Liver-fluke, 172.                            of, 509; osteology of, 510, 517; teeth of,
Lizards, 413, 435, 436.                      517, 518; digestive system of, 519; cirLlama, 561, 562.                             culatory system of, 519; respiratory
Lobster, morphology of, 203-207; general      system of, 519; nervous system of, 520;
anatomy of, 228-230.                       reproductive system  of, 520; integuLob-worln, 196.                              mentary system of, 521; primary diviLoculi, of shell of Foraminifera, 53; of      sions of, 522; orders of, 524-526; disCorals, 120.                               tribution of, in time, 607-617.
Locustina, 260.                            Mammoth, 571, 616.
Lotigo, 329, 335.                          Manatee, 510, 542, 543.
Longipennatce, 477.                        Manatidee, 542.
Longirostres, 483..                        Manatus, 510, 524, 542, 543.
L.ophiidoe, 387.                           Mandibles, of Lobster, 206; of Arachnida,
Lophobracchii, 338.                          236; of MAyriapoda, 246; of Insecta, 250,
Lophopea, 286.                               251; of Cephalopoda, 323, 332; of VerteLophopore, 284, 286.                         brates, 352.
Lophopus, 282, 283.                        Afanide, 541.
(Lophortyx, 489.                            M1anis, 517, 521, 541.
Lophyropoda, 208, 215.                     Mantle, of Tunicata, 287; of Brachiopoda,
Loricata, 421.                               293; of Lamellibranchiata, 302; of GasLorius, 494.                                 teropoda, 309; of Cephalopoda, 322; of
Love-bird, 494.                              Nautilus, 331.
Loxiadce, 498.                             Manubrium, 87, 88, 95, 101, 103.
Lucernaria, 104, 105.                     AMareca, 479.
Lucernariadce, 105.                        Marginal bodies, of Medusce, 101, 104; of
Lucernarida, 30, 83; general characters      Lucernarida, 104, 109.
of, 104; umbrella of, 104, 108; divisions   Mlarginella, 317.
of, 104; development of, 106, 107;  Marmoset, 602.
structure of reproductive zoOids of, 108,  M3armot, 591, 592.
109.                                     Marsipobranchii, 378; general characters
Lucina, 307.                                 of, 378-380; families of, 379; distribuLucinidce, 306, 307.                         tion of, in time, 403.
Luidia, 151, 164.                          Marsupial bones, 515, 527, 530.
Lumnbricide, 191.                          Marsupialia, 516, 521), 522, 523, 524; genLumbricus, 191.                              eral characters of, 529; families of, 531Lutcra, 580.                                 536; distribution of, in space, 529; in
Lutraria, 307.                               time, 6(;9, 611.
Lycaon, 582.                               Marsupites, 163.
Lyencephala, 522.                          Mastax, 181.
Lynx, 585.                                NMastodon, 569, 572, 615.
Maxillae, of Lobster, 206; of Arachnkia,
MAcAcus, 604.                                236; of Insecta, 250, 251.
Maccaw, 494.                               Maxillipedes, of Lobster, 206; of Ceuti.
Maceliodon, 441.                             pedes, 246..
Machairodus, 618                           May-flies, 261.
Machetes, 483.                             Afeandrina, 125, 138.
MAacleurea, 319, 887.                      Measles, of Pig, 170; of Ox, 170.




664                                   INDEX.
Medusadx, 100, 101; structure of, 101;   Monads, 37, 38.
exact nature of, 102, 103.                AMonera, characters of, 49.
Alegaceros, 564, 614.                        Monitor, 439.
Megaderma, 595.                              Monkeys, 513, 514, 520, 526, 59.
Alegalonyx, 611, 618.                        Mlonodelphia, 523.
JMegalosaurus 451.                           Monodon, 551.
Megalotrocha, 180.                           Monomerosomata, 238, 239.
Megapodidce, 490.                            Monomyaria, 305.
Megaptera, 548.                              Monostega, 57.
3Megatherium, 611, 612.                      Monothalamia, 55.
Melania, 317.                                 Monotremata, 511, 512, 515, 520, 522, 523,
MAelaniadee, 313, 317.                          524; general characters of, 527; distribu.
AMeleca7ris, 489.                               tion of, in space, 528; in time, 609.
[eleagrinoe, 489.                            Mopsea, 128, 139.
MAeles, 579.                                  Morphology, 12.
Aelicerta, 180, 181, 188                     Morse, 576.
Mfelidae, 579.                               Mosasaurus, 441, 442.
lMeliphagidce, 499.                          Moschidoe, 561, 562.
Alellivora, 580.                             Mloschus, 562.
Melobesia, 5S.                                Motacillince, 499.
Memibrana nictitans (of Birds), 470; of   Mother-of pearl, 277.
Mammals, 470, 521.                         Moths, 265, 267.
Alenlbranchus, 410, 411.                     Mud-fish, 373, 374, 379, 399.
JMenopomna, 410, 411, 412.                   Mnuilidce, 3S7.
Mentuni, 251.                                Miilleria, 306.
Mephitis, 580.                               Multivalve shells, 277, 315.
JMergitlus, 476.                             Murcenidoe, 384.
Mieriones, 591.                              MArchisonia, 318.
Mferopidce, 500.                             Mu-rex, 317.
AMerostola ta, 215; characters and divi-   Mu'ricidce, 313, 317.
sions of, 221; distribution of, in time,234.  Matridce, 589, 590.
Merzilidce, 498, 499.                        Mus, 590.
Mferycotheritzm, 618.                       MNaca, 265.
Mesenteries (of Actinozoa), 114, 115, 118,   Aluscicapidc, 498.
121, 133.                                  Musk-deer. 561, 562.
Mesopodium, 309.                             Musk-ox, 568.
Mesotllorax, 249..Alstela, 580.
Metapodium, 309.                             Mlustelidce, 580.
Metasoma, 322; 331.                          M4utilata, 542.
Metamorphosis,35; ofMypriapoda,246;ofln-   Mya, 302, 305, 807.
secta, 254; incomplette.255; colnplete, 255.  Mlyacidce, 306, 307.
Metastoma, of Lobster, 206; of Eurypter-   Mlycetes, 602, 603.
ida, 223.                                 MAyiiobatis, 399.
Metathorax, 249.                             Mylodon, 611, 618
AMianmia, 273.                               AMyochama, 307.
Iricroconchus, 198.                          Myodes, 590.
AMicrolestes, 608, 609, 616..yopotam.us, 589.
Miliola, 54.                                MIyoxidce, 591.
Miliolida, 56.                               Jlyloxus, 591.
Milleporidce, 140.                           M1Iyriapoda, 2q0; general characters of,
Millipedes, 245, 247.                          245; development of, 246; distribution
Mimicry, 18.                                   of, in time, 247.
Mites, 240.                                 AMyrinecobiats, 535, 536.
Mitra, 317.                                 MAyrmecophaga, 517, 540.
Modeeria, 102.                               Alyrmecophagidoe, 540.
Modiola, 306.                                Ms[yrneleo, 261.
Mole, 512, 515, 521, 596.                    Mysis, 227.
Maolglcla, 290.                             lMytilidcv, 305, 306.
Afolluesca, 16, 274; general characters of,  AMytilis, 305, 306.
274-278; digestive system  of, 274; cir-   Myxine, 379, 381.
culatory  system  of, 275; respiratory   Mjxinide, 378, 381.
organs of, 275; nervous system of, 276;  Mhyxinoids, 374, 379.
sense-organs of, 276; reproduction of,
276; shell of, 276-278; divisions of, 278;   NACRrOUS shells, 27T.
distribution of, in time, 298, 336.        Jraidide, 191, 192.
Molluzsca Proper, 278; characters of, 300;  TNais, 192.
divisions of, 300; distribution of, in   Naja, 432, 433, 434.
time, 336-338.                             Narwhal, 551.
Molluscoida, 278; characters and divisions   Nassa, 317.
of, 279; distribution of, in space, 297;   Nasiea, 579.
in time, 298.                              Natatores, 473; general characters of, 474.
Molothraus, 493.                            iNathetes, 441.
Mvalottas, 501.                              Natica, 317.




INDEX.                                     665
raticidw, 313, 317.                          Octopoda, 328, 334.
Nauplizs, 210.                                Octopodidov, 328, 336
Nautilidce, characters of, 883; sections of,   Octopus, 325, 335..335; distribution of, in time, 337.        Oculinidse, 140.
Nautiloid Foraminifera, 55, 57.               Ocypoda, 232.
Nautilus, Paper, 328; shell of, 327, 328;   Odontaspis, 405.
Pearly, 330; anatomy of, 331; shell of,   Odontoceti, 545, 548.
327, 331.                                  Odontophora, 300, 308.
Nebalia, 218, 234.                           Odontophore, 309.
Nectocalyces, 93; structure  of, 95; in   Oedicnemus, 484.
Calycophoridce, 95, 96; in Meduside,   Oidemia, 479.
101; distinguished from the umbrella of   Oldharnia, 113, 298.
the Lucernarida, 104.                       Oligochwata, 191, 192, 198,
Neetosac, 95.                                 Oliva, 317.
Needham, moving filaments of, 325.            Ommastrephes, 335.
Nematelmita, 165; characters of, 175.         Onmnivora (Ungulata), 556.
Nematocysts, 80.                              Onchuna, 209.
Nematoda, 165, 166; characters of, 176;   Onchus, 404.
parasitic forms of,177; free forms of, 179.   Oncidiadoe, 317, 319.
Nelmatophores, 82, 92.                        Oncidium, 319.
YNernertes, 174                               Oniscus, 226.
Nei ertida, 166, 173; characters of, 174;   Onychoteuthis, 323, 335.
developmlent of 175.                       Operculata, 317, 319.
Nereidwe, 196.                                Operculun, of Balanidoe, 212,214; of Gas
Nereidea, 194.                                  teropoda, 309; of Heteropoda, 315; of
Nereis, 196.                                    Pteropoda, 320; of Fishes, 365, 366.
Neerita, 318.                                 Ophicrinus, 158.
Neritilna, 318.                               Ophidia, 423; general characters of. 428Neritidoe, 314, 318.                            431; divisions of, 431; distribution of,
Nervures, 249.                                  in tine, 434.
Neuropodium, 188.                             Ophidobatrachia, 409.
Neuroptera, 251, 261, 278.                    Ophiocoma, 154, 164.
Newts, 412, 413.                              Ophioderma, 164.
Nidamlental ribbon, 276.                      Ophiolepis, 154, 164.
Noctiluca, 76.                                Ophiomnorpha, 409.
Nodosaria, 54, 55.                            Ophisacuqus. 437.
Nothosaurus, 448.                             Ophisura, 154.
iNotidanus, 405.                              Ophiusidea, 155.
Notochord, 347, 348.                          Ophiueroidea, 143, 144; general characters
Notommnatina, 183.                              of, 153; families of, 155; distribultion of,
Notonzectc, 259.                                in space, 162; in time, 163, 164.
Notopodiuim, 188.                             Opisthobranchiata, 313, 314, 318.
Notornis, 481.                               Opisthocoelia (Crocodilia), 445.
_Nucleobranchiata, 315 (see Iteteropoda).    Opossurl, 534, 535.
Nucleolus of Paramcihun, 71, 72.             Orang-outang, 605.
Nucleuls, of Protozoa,' 44; of Gregarina,   Orbitoides, 60.
46; of Amceba, 50; of lnfusoria, 71;   Orbitolites, 56.
of Vorticella, 73; of Echinodermata,   Oreaster, 164.
152 (see Madreporiform  tubercle); of   Organ of Bojanus, 205, 304.
the shell of Mollusca, 277.                Organ-pipe Coral, 126.
N'udibranchiata, 310; characters of, 314,   Organs of the mouth of Insects, 250-252.
divisions of, 319.                         Oribatidoe, 240.
NioneLiuLs, 483.                             Ornithodelpia, 523.
N'unilda, 489.                               Ornithorhynchucs, 517, 520, 523, 527, 528.
Nummnrnulites, 56, 59, 60.                   Ornzithosasuria, 450.
Numnlll  titt fli lestone, 60.               Ofrthis, 296.
Nyeticebidce, 601.                           Orthisina, 296.
Nyleticebus, (;01.                           O1rthoceras, 333, 334, 335, 337.
3'ctficorax, 483.                            Orthoceratidt, 335, 337.
Nym1ph, 254, 255.                            Orthoptera, 250, 260, 27,3.'Nyyiphon1, 239.                             Orttyx, 489.
Orycteropidce, 541.
Obolus, 297.                                 Orycterptus,9, 541.
Oceanic IlHydrooa, 93; divisions of, 93-   Osclla, of Sponges, 64, 69; of Tapeworm,
100; distribntion of, in space, 112.         168.
Ocelli, of Medusco,   101; of Echinoidea,   Osteolepis, 391, 403.
146; of Asteloisdea, 152; of J'lanarida,   Ostraciontidce, 388.
174, of Rotifera, 182; of A itnelida, 189;   Ostracodtla, 208; characters of, 216; disof Chcetognatha, 199; of Limsulus, 221;      trilution of, in tilme, 234.
cf Araschnida, 238; of Myrioapodca, 246;   Ostracostei, 392, 403.
of Insecta, 254; of''unicata, 276; of   Ostrea, 305, 306.
Laeelliblranchata, 276; of Gastero-   Oatreidce, 305, 306.
poda, 309.                                  Ostrich, 48S4, 485.




666                                 INDEX.
Otaria, 576.                               Peachia, 117,.133.
Ot.idce, 484.                              Pearly Nautilus, 322, 323, 326, 327, 330,331,
Otter, 580, 581.                             334.
Oudenodon, 449.                            Peccary, 557, 618.
()varian vesicles, of Sertularid, 91.      Pecten, 305, 306.
Ovibos, 568.                               Pectinaria, 194.
Ovidce, 567.                               Pectunculus, 306.
Ovipositor, 250, 268.                      Pedetes, 591.
Ovis, 567.                                 Pedicellariae, 146, 151.
Ovulum, 317.                               Pedicellina, 284.
Owls, 502.                                 Pedicellinea, 286.
Oxen, 561, 567, 568, 615.                  Pediculus, 258.
Oxyuris, 177.                              Pedipalpi, 241, 242.
Pelagia, 105, 110.
PACA, 588.                                 Pelagide, 104, 105; structure of generaPachydernata, 5516                           tive zooids of, 108.
Paddle-fish, 392.                          Pelias, 432.
Paguridce, 231.                            Pelicanidce, 478.
Palceaster, 164.                           Pelonaia, 277.
Pal?chinuls, 150, 164.                    Pen, of Cuttle-fishes, 326, 329.
Palceichthyes, 402.                        Peneus, 228
Palceocoryne, 113.                          Penguin, 475, 476.
Palcoe, imli(ls, 159.                      Penieulus, 2)9.
Palceodtliscus, 164.                       Pennatula, 126, 127.
Palceophis, 434.                           Ponnatulidce, 125, 126, 135; distribution
Palceospongia, 68.                           of, in time, 139.
Paloeetherium, 555, 613.                   Pentacerotidce, 153.
Palceotringa, 507.                         Pentacrinus, 155, 157, 163.
Palamedea, 481.                            Pentamera (Coleoptera), 273.
Palapteryx, 507.                           Pentanerus, 296.
Pali (Corals), 120.                        Pentastomida, 239.
Pallial line, 302, 303, 304.               Pentatoma, 259.
Pallial sinus, 304.                        Pentrerrites, 160, 163.
Palliobranchiata, 292.                     Peramnelidce, 534.
Palliun (see Mantle).                       Perchers, 495.
Paludicella, 284.                          Percidoe, 387.
Paludicellea, 286.                         Perdicidce, 489.
Paludina, 318.                             Perdix, 489.
Paludinidee, 314, 318.                     Perennibranchiata (Amphibia), 406, 407,
Paludomus, 317.                              408, 410, 411.
Palythoa, 122.                             Perforata (Foraminifera), 53, 56; (Corals),
Paimphagus, 52.                              123, 139, 140.
Pangolin, 541.                             Pericardium, of Crustacea, 201, 207; of
Panopoea, 3u7.                               Nautilus, 332.
Panspermy, 37.                             Periderm, 90.
Pantopoda, 239.                            Peridiniuin, 76.
Paper Nautilus, 322, 326, 328.             Perigastric space, of Polyzoa, 284.
Papio, 604.                                Periostracuml, 278.
Paradiseidce, 497.                         Perischoechinidoe, 164.
Paradoxurus, 579.                          Perissodactyla, 552, 553.
Paramncecium, 38, 70; structure of, 71,  Peristome, of Vorticella, 73; of the shell
72; reproduction of, 72.                   of Gasteropoda, 312.
Pararturicea, 129.                         Peristonlial space of Actinia, 117.
Parapodia, 188.                            Peritoneum (Tunicata), 289.
Parince, 498, 499.                         Perivisceral space, of Actinozoa, 115.
Pa'keria, 59.                              Perna, 304.
Parmacella, 319.                           Petaurus, 534.
Parenaphorus, 318.                         Petraster, 164.
Parra, 481.                                Petrogale, 533.
Parrakeets, 494.                           Petromyzon, 380.
Parrots, 494.                              Petronyzonidre, 378, 380.
Parthenogenesis, 31-34; of Ostracoda, 216;  Petrospongiadce, 68.
of Insects, 32, 33.                       Pezophaps, 492, 508.
Passeres, 495.                             Pezoporince, 494.
Patagium, 449, 450, 592, 593.               Phacochcerus, 557.
Patella, 311, 318.                          Phoenicopteridce, 478.
Patellidce, 314, 318.                      Phcenicopterus, 479.
Pauropoda, 247.                            Pha'ton, 478.
Pauropus, 245, 246, 247.                   Phalacrocorax, 478.
Pavo, 489.                                 Phalangers, 534.
Pavonaria, 127.                            Phalangidce, 241.
Pavonince, 489.                            Phalangistidce, 534.




INDEX.                                    667
Phalansterium, 76.                           402; distribution  of, in  time, 402Pharyngobraitchii, 87.                        405.
Pharyngognathi, 387.                        Placenta, 510, 522.
Pharynx, of Ascidians, 288, 289; of Lance-   Placentalia (Mammalia), 522.
let, 377.                                 Placodus, 448.
Phascolarctos, 532, 588.                    Placoganoidei, 391, 392, 403.
PhaScoloimys, 531.                          Placoid (scales of Fishes), 363.
Phascolotherium, 608, 609, 61G.             Placoidei, 394.
Phasianicoe, 489.                           Placqiaulax, 608, 610.
Plhasiaus, 489.                             Plagiostomi, 395; characters of, 897.
Phasmidce, 18.                              Planarida, 173, 174, 183.
Pheasant, 489.                              Planorbis, 312, 319.
Pheronerna, 67.                             Plantigrada, 574, 577.
Philine, 319.                               Planula, 106.
Phillipsia, 234.                            Plastron, 424, 425.
Phoca, 575.                                 Plataleadcce, 483.
Phoccena, 550.                              Platanista, 550.
Phocidce, 575.                             Platyelmia, 165; characters of, 166.
Pholadidoe, 277, 306, 308.                  Platyrhina, 599, 601.
Pholadomya, 307.                            Plecotus, 594.
Pholas, 305, 308.                           Plectognathi, 387.
Phorus, 318.                                Plesiosauria, 447.
Phosphorescence of the Sea, 76.             Plesiosaurus, 447, 448.
Phrag:acone, 277; of Spirula, 326, 330;  Pleura, of Lobster, 203; of Trilobite, 221.
of Belemnite, 330, 335.                   Pleuracanthus, 4.4, 41,5.
Phragmoceras, 335.                          Pleurobrachia, 130, 131; ctenophores of,
Phryganeidoe, 261.                            130; canal-system of, 131, 132; developPhylactolcemata, 286.                         ment of, 13'2; homologies of, 133.
Phyllidia, 319.                             Pleurobrachiadce, 134.
Phyllidiadce, 314, 319.                     Pleurobranchidve, 314, 319.
Phyllirrhoe, 319.                           Pleurobranchus, 319.
Phyllirrhoidce, 314, 319.                   Pleuronectidce, 386, 398.
Phyllium, 18.                               Pleuronema, 76.
Phyllocyst, 95.                             Pleurotoma, 317.
Phyllopoda, 208; characters of, 218; dis-   Pleurotomaria, 318.
tribution of, in time, 234.               Pliolophus, 613.
Phyllostorna, 595.                          Pliopithecus, 617.
Phyllostomidee, 594, 595.                   Plotus, 478.
Pliyogemlmaria, 98.                         Plough-share bone, 457.
Physa, 319.                                 Plurnaster, 164.
Physalia, 80, 93, 97, 98.                   Plumularia, 92.
Physaliadce, 100.                           Pluteus, 143, 144, 148.
Physalus, 548.                              Plyctolophus, 494.
Physeter, 549.                              Pneumatic filaments of Physophoride, 97.
Physeteridce, 548.                          Pneumnatocyst, 97.
Physiology, 13.                             Pneumatophore, 97, 98.
Physophora, 98.                             Pneunodermon, 321.
Physophoridce, 93; characters of, 97, 98;  Podargus, 500.
tentacles of, 97; reproduction of, 98;  Podophthalmata, 208; characters of, 227.
distribution of, in space, 113.           Podosomata, 239.?hysostomata, 383.                          Podura, 250, 258.
Picidoe, 493.                              Polistes, 33.
Pigeons, 491.                              Polyarthra, 183.
Pigment-spot, of Infusoria, 75; of Roti-  Polycoelia, 139.
fera, 182.                                Polycystina, 61, 62.
Pileolus, 318.                             Polydesmuts, 247.
Pileopsis, 318.                            Polygastrica (of Ehrenberg), 71.
Pilidiumn, 174, 175.                       Polynoe, 197.
Pinna, 305, 306.                           Polypary, 85, 89, 90.
Pinnigrada, 574, 575.                      Polype, 116.
Pinnipedia, 574.                           Polypide, 280, 281.
Pinnoctoputs, 335.                         Polypidom, 82.
Pipa, 414, 416.                            Polypite, 81.
Pipe-fish, 388.                            Polyplectron, 489.
Pipidce, 416.                              Polypterus, 391.
Pisces, 359, 360; general characters of,  Polystome Insfusoria, 76.
362; scales of, 362; skeleton of, 363-  Polythalamia (ForaminLifera), 55.
369; limbs of, 367; tail of, 370; digestive   Polytremna, 59.
system  of, 373; respiratory system    Polyxenia, 102.
of, 371; heart of, 372; swim-bladder of,   Polyzoa, 274, 275, 276; characters of, 279;
374; nervous system  of, 374; repro-       distinctions from  HBydrozoa, 279, 2S0;
ductive system of, 374, orders of, 376-    typical polypide of, 281; avicularia of,




668                                 INDEX.
282; lophophore of, 284; nervous system   Pseudembryo, 144.
of, 284; digestive system of, 284; repro-  Pseudobranchia, 390.
duction of,285; statoblasts of,285; devel-  Pseudohbemal system, 188.
opment of, 286; relations to Tunicata,  Pseudo-hearts, 294.
291; divisions of, 286; orders of, 286; dis-  Pseudonavicelle, 47.
tribution of, in space, 297; in time, 298.  Pseudopodia, 45, 48, 49, 51, 54, 61, 61
Polyzoarium, 280.                          Pseudopus, 435.
Pontarachna, 241.'                         Pseudoscorpionidce, 241.
Pontobdella, 191, 198.                     Psittacidce, 493, 494.
Poramnbonites, 296.                        Psittacus, 494.
Porcellana, 231.                           Psogus, 165.
Porcellanous shells, 277.                  Psorospermice, 48.
Porcellia, 337.                            Ptarmigan, 489.
Porcupine, 521, 588, 589.                  Pteraspis, 385, 402, 403.
Pores of Sponges, 64, 65.                  Pterichthys, 385, 392, 393, 408.'
Porites, 138.                              Pteroceras, 317.
Poritidce, 140.                            Pterodactyles, 449, 450.
Porpoise, 544, 549, 550.                   Pteromys, 591.
Portuguese man-of-war, 80, 93, 97, 98, 99.   Pteropidce, 595.
Potanmides, 317.                           Pteropoda, 300, 308, 311; general charPoulpe, 325, 328.                            acters of, 320; foot of, 320; shell of, 320;
Praya, 95.                                   divisions of, 321; distribution of, in
Prayidce, 96.                                space, 321; in time, 337.
Pressirgstres, 481, 483.                   Pteropus, 595.
PPrestwichia, 234.                         Pterosauria, 423; general characters of,
Priapulacea, 187.                            449; distribution of, in time, 450.
Primates, 592.                             Pterygotus, 223, 234.
Primnnoa, 129.                             Ptilodictya, 298.
Pristis, 399.                              Ptilotd apsus, 113.
Proboscidea, 522, 525; characters of, 569;  Ptilcpora, 298.
distribution of, in time, 615, 616.      Ptychoceras, 333, 3838.
Proboscis, of Medusce, 101; of Crinoidea,  Pulcx, 264.
156, 159; of Planarida, 173; of Acan-   Pulicidce, 264.
thocephata, 175; of Gephyrea, 186; of.Pulmogasteropoda, 310, 313, 316.
Errantia, 195; of Lepidoptera, 251; of  Pulmonaria (Arachnida), 238, 241.
Proboscidea, 570.                        Pula onifera (Mollusca), 313, 316
Procellaridce, 477.                        Puma, 5S5.
Prochilits, 578.                           Pupa, 254, 255, Z56.
Procoelia (Crocodilia), 448, 44g           Puepa, 319, 337.
Procyon, 579.                              Pupina, 319.
Producta, 297.                            Puppipara, 264.
Prodtuctidoe, 297, 298.                    Purples, of Wheat, 179.
Proglottis, 167, 170.                      Pu~rpura, 317.
Pro-legs, 266.                             Putorius, 580.
Proeropidce, 499.                          Pycnogonum, 239.
Pro-ostracum, 329, 330.                    Pygidium, 219, 220, 221.
Propodite, 204.                            Pyram~idella, 317.
Propodiutm, 309.                           Pyramidellidoe, 313, $17.
Proscolex, 168, 170.                       Pyrgita, 498.
Prosinmice, 600.                           Pyrosonidce, 292.
Prosobranchiata, 313; divisions of, 313,317.  Pyrrhuzla, 498.
Prosoma, 322, 331.                         PyruLla, 317.
Prosoponiscus, 234.                        Python, 421, 433.
Prostomium, of Planarida, 173; of Annelides, 188.                              QUADRATE Bone, 352, 360.
Protaster, 164.                            Quadrumnana, 513, 514, 516, 522, 526;
Proteles, 582.                                characters of, 598; sections of, 598,
Proteolepas, 215.                            599; distribution of, in time, 617.
Proteus, 410, 411.                         Quagga, 555.
Proteus-animalcule, 49.
Prothorax, 249.                            RABBIT, 588.
Protoplasm, 5.                             Racoon, 579.
Protopodite, 204.                          Radiata, 78.
Protopteri, 399 (see Dipnoi).              Radiolaria. 46; characters of, 6L
Protoruis, 507.                             Radiolites, 306.
Protovirgularia, 139.                      Raia, 398.
Protozoa, 14; general characters of, 44 45;  Raltidae, 481.
classification of, 45, 46.                Rallus, 481.
Proventriculus, of Earthworm, 191; of  Ramphorhynchus, 449, 450.
Birds, 465.                             BRana, 414, 415, 417.
Proximal, S1..Ranidae, 415, 417.
Psammobia, 307.                             Jlanina, 232.




INDEX.                                      669
Raptores, 475; characters of, 501; sec-  Sable, 580.
tions of, 502.                             Scenuridce, 191.
Rasores, 465, 471, 475; characters of,  Sagitta, 198.
487; sections of, 488.                     Salamanders, 410, 411, 412, 4i&
Rastrites, 111.                              Salamandra, 413, 416.
Rat, 590.                                    Salmonidce, 385.
Ratel, 580.                                  Salpidce, 290, 292..latitce, 472.                               Sand-pipers, 483.
Rays, 394, 395, 398, 399, 405.               Sand-worms, 194.
Red Coral, 119, 128.                         Sanguisuga, 190, 191.
legnum Protisticum, 8.                      Sarcode, 44; characters of, 44, 45.
Rein-deer, 562, 564.                         Sarcodictyun, 126.
Reproduction, general phenomena of, 24-   Sarcoids, of Sponges, 64, 65, 67.
34; sexual, 25; non-sexual, 25-34.         Sarcoptes, 240.
Reptilia, 859, 360; general characters of,  Sarcorhampses, 504.
419; jaw of, 420; teeth of, 421; circula-   Sarsia, 102, 103.
tion of, 422; respiration of, 423; orders   Saetria, 436.
of, 423-452.                               Saurillus, 441.
Respiratory tree, of Holothurians, 161.      Scaurobatrachia, 410 (see Urodela).
Respiratory tubes, of Rotifera, 182.         Saurocetes, 613.
Reticulosa (see Foraminifera), 54, 56.       Sauropsida, 360.
Jetiolites, 111.                             Sastropterygia, 423; general characters of,
Reversed shells, 278.                          447; distribution of, in time, 448.
Rhabdoccela, 174.                            Sauruurce, 472, 474; characters of, 505;
Rhabdoidea, 57.                                distribution of, in time, 507.
hilhabdopleura, 284, 286.                    Saw-fish, 399.
Ihabdopleurea, 286.                          Saxicava, 308.
Rhantphastide, 493, 494.                     Scalaria, 318.
Rhea, 486..                                  Scalops, 597.
i.hinobatis, 399.                            Scalpellusn, 214..Rhinoceridee, 553, 611.                     Scansores, 474; characters of, 492; famh'hinoceros, 553, 554, 613.                    ilies of, 493.
ihinzolophidoe, 594.                         Scaphites, 335.
Rhinolophus, 594.                            Scaphognathite, 206.
lhizocephala, 207; characters of, 210.       Scelidotheriu'mn, 618.
RIhizocrinus, 156, 157, 162.                 Scincidce, 437.
Rhizophysiadce, 99.                          Scincuts, 438.
Rhizopoda, 46,; characters of, 48; pseudo-   Scissurella, 318.
i)odia of, 48; divisions of, 49.           Sciuridce, 591.
Rhizostomca, 109, 110.                       Sciutropterus, 591.
Rhizostomidce, 104; definition  of, 106;   Sciurus, 591.
development of, 106, 107; structure of   Sclerenchyma, 121.
reproductive zoiids of, 109.               Sclerobasica (Zoanctharia), 119; divisions
Rhynchonella, 296, 298.                        of, 122.
Rhynchonellidce, 294, 295, 296.              Sclerobasic corallum, 119, 121.
Rhynchosaurus, 449.                          Sclerodermata (Zoantharia), 122; diviRhynchota (see Hemiptera).                     sions of, 123, 139.
Rhytina, 517, 542, 543, 544.                 Sclerodermic corallum, 119, 123.
Ribbon-worms, 174.                           Sclerogenidoe, 387..issoa, 318.                                 Scolecida, 141, 142; characters and divi-.odentia, 513. 522, 525; general char-         sions of, 165, 106.
acters of, 586; families of 587-591; dis-   Scolex, 168, 170, 171.
tribution of, in time, 616.                Scolites, 197.
Rorqual, 548.                                Scolopacidce, 483.
Rot, of Sheep, 172.                          Scolopendra, 245, 246.
Rotalina, 56.                                Scomberidce, 387.
Rotatoria, 179 (see Rotifera).               Scorpion, 236, 241, 242.
Rotifera, 6, 165; characters of, 180; wheel-   Scorpionidce, 242; characters of, 242; disorgan of, 180; water-vascular system of,    tribution of, in time, 244.
182; masticatory organs of, 181; affini-   Scutigera, 246.
ties of, 183; vitality of, 6; distinctions   Scylloea, 319.
from Infusoria, 183.                       Scyllaridce, 203.
Round-worms, 176.                            Scythrops, 493.
Rugosa, 116; characters of, 128; distribu-   Sea-anemones, 117, 13S
tion-.f, in time, 138; families of, 140.   Sea-cucumbers, 160.
Rurninantia, 513, 514, 516; characters of,  Seals, 575.
558; dentition of, 560; stomach of, 558,   Sea-mouse, 194, 195.
559; families of, 561; distribution of, in   Sea-slugs, 314.
time, 614.                                 Sea-spiders, 239.
Rupicapra, 566.                              Sea-worms, 194.
Saella, 193.                                 Segmental organs, of Leeches, 100; of
Sabellaria, 194.                               Earthworm,192; of Errant Annelides, 195.




670                                   INDEX.
Selachii, 394, 397; characters of, 397.      Solen, 307.
Semnopithecus, 603.                          Solenidce, 306, 307.
Sepia, 330, 335.                             Solidungula, 552, 555, 615.
Sepiadee, 329, 335, 338.                     Solipedia (see Solidungula).
Sepiostaire, 326, 329.                       Solitaire, 492.
Septa, of Corals, 120, 123; of the shell of   Solpugidce, 241.
Tetrabranchiate Cephalopods, 327, 331,  Sornateria, 479.
332, 333.                                  Somatic cavity, of Ccelenterata, 79; of
Seriatoporidce, 140.                           Hydrozoa, 80; of Hydra, 84; of AcSerpentarius, 504..tinozoa, 114.
Serpula, 194.                                Somatocyst, 93, 94.
Sertularida, 83; characters of, 90; hydro-   Somite, 199; of Cruwtacea, 203; of Arachthecme of, 90; polypites of, 91; repro-      nida, 235.
duction of, 91; development of, 92;   Sorex, 597.
distribution of, in space and time, 112,   Soricidce, 597.
113.                                       Soroidea, 57.
Sette, of Annelides, 188, 189, 191, 192,   Sparsispongia, 68.
194.                                       Spatangidce, 150.
Sharks, 394, 395, 397, 405.                  Spatularia, 392.
Sheat-fishes, 3S5.                           Species, definition of, 23; origin of, 39, 40.
Sheep, 567.                                  Spermatophores, 325.
Shell of M[ollusca, 276, 278; of Brachio-   Sperm-whale, 549.
poda, 292, 293; of.Lamellibranchiata,   Sphcerogastra, 243.
301; of Gasteropoda, 311; of Hetero-   Sphceroica, 226.
poda, 315; of Pteropoda, 320; of Ar-   Sphceronectidoe, 96.
gonauta, 327, 328; of Nautilus, 327,   Sphcerozourn, 62.
331; of Tetrabranchiate Cephalopods,   Sphagodus, 404.
332, 333.                                  Sphargis, 426.
Shrew-mice, 597.                             Spheniscidoe, 475.
Shrew-mole, 597.                             Spheniscus, 476.
Shrikes, 498.                                Spicula, of Sponges, 64, 67; of RadioSiamang, 605.                                  laria, 61, 62; of Actinozoa, 121, 126.
Sigaretus, 318.                              Spider-monkey, 602.
Silicea (Sponges), 67, 69.                   Spiders, 235, 236, 237, 243.
Siluridce, 385.                              Spinax, 395.
Silurus, 385.                                Spiniferites, 69.
Simia, 605.                                  Spinnerets of Spiders, 244; of Caterpillars,
Simosautrus, 448.                              266.
Sinupallialia, 304, 306, 307.                Spirialis, 321.
Siphonia, 67, 68.                            Spirifer, 296.
Siphonida, 305, 306.                         Spiriferidce, 296, 298.
Siphonophora, 83; characters of, 93;   Spiriferisa, 296.
divisions of, 93-100.                      Spirorbis, 194, 198.
Siphonops, 409.                              Spir-ula, 326, 330, 335.
Siphonostomata (Gasteropoda), 312, 313,  Spirulidce, 329, 335.
317.                                       Spirulirostra, 335.
Siphonotreta, 297.                           S[lanchnoskeleton, 277.
Siphons, of Lamellibranchiata, 303; of  Spondylus, 306.
Gasteropoda, 311.                          Spongida, 49, 63' skeleton of, 64, 67;
Siphuncle, of the shell of Nautilus, 327,      sarcoids of, 64, 67; aquiferous system
331, 332; of Belemnlites, 330; of Tetra-     of, 65; reproduction of, 66; classificabranchiata, 332, 333; of Nautilidce,         tion of, 67; distribution of, in space,
333; of Ammonitidce, 333; of Ortho-          68; in time, 68; affinities of, 69; indiceras, 334.                                  viduality of, 69.
Sipunculacea, 187.                           Spongilla, 68; reproduction of, 66; sarSipunculoldea, 185.                            coids of, 67.
Sipunculus, 186.                             Spoon-bill, 483.
Siredon, 411, 412.                           Spoon-worm, 185, 186.
Siren, 410, 411.                             Spores, of Sponges, 66.
Sirenia, 510, 512, 515, 517, 522, 524; char-   Sporosac, of Corynida, 86, 88
acters of, 542-544; distribution of, in   Spring-tails, 250, 258.
time, 612.                                 Squalidee, 397.
Sirenidce, 411.                              Squamse, of Aphrodite, 195.
Sitta, 499.                                  Squamata (Reptilia), 421.
Sivatheriurn, 565, 615, 618.                 Squamulina, 57.
Slaters, 226.                                Squids, 322, 329.
Sltnonia, 234.                               Squilla, 227.
Sloth, 510, 511.                             Squirrel, 591.
Snakes, 420, 423, 428, 429, 430, 481.        Staggers, of Sheep, 171.
Solarium, 318.                               Star-nosed Mole, 596.
Solaster, 152.                               Statoblasts, 28, 285.
Solecurtus, 307.                             Stauridce, 140.




INDEX.                                   671
Stauridia, 88.                            Syngnathide, 388.
Steatarnis, 500.                          Syrinx, 186.
Steganodictyum, 68.
Steganophthalmata (Medusso), 100, 104,  Tabanidce, 265.
105, 110.                               Tabulae, of Corals, 123.
Stem-muscle, of Vorticella. 72            Tabulata, 123, 139.
Mtemmata (see Ocelli).                     Tachypetes, 478.
Stenaster, 164.                           Tcenia, 167, 169, 170, 17,.
Steneosaurus, 445.                         Tceniada, 165; characters and develop.
Stentor, 9, 75.                             ment of, 166-171.
Stephanoceros, 180, 183.                  Talitrus, 225.
Stephanomiadce, 99.                       Talpa, 596.
Sterelmintha, 172.                        Tc1lpidce, 596.
Stereognathus, 608, 609.                  Tamias, 591.
Sternaspis, 186.                          Tancgrince, 498.
Sternum, of Crustacea, 204; of Arach-   Tanais, 226.
nida, 235; of Chelonia, 426; of Aves,  Tank-worms, 178.
459; of Mammalia, 512.                  Tantalince, 483.
Stichostega, 57.                          Ta;le-wornm, 166, 167, 168, 169, 170.
Stigmata, of Physophoridce, 97; of Leeches,  Tapir, 554, 618.
190; of Arachnida, 238; of. lnsecta,   Tapiridce, 554.
253.                                    Tardi4grada, 239.
Stolbns, of Foraminifera, 55; of com-   Tectibranchiata, 314, 318.
posite Actinozoa, 124; of social Tutni-   Teleosaurus, 445.
cata, 290.                               Teleostei, characters of, 381-383; subStomapoda, 208; characters of, 227; de-    divisions of, 383-388; distribution of, in
velopment of, 227; distribution of, in    time, 403-405.
time, 234.                               Tellina, 307.
Stomatodendra, 109.                        Tellinides, 306, 307.
Stork, 481, 483.                           Telmatornis, 507.
Strepsilas, 483.                          Telson, of Crustacea, 202; of Lobster,
Strepsiptera, 250.                           204; of Limulus, 222; of Scorpion,
Strepsirhina, 599, 600.                      242.
Streptospondylus, 445.                     Tenrec, 507.
Strigidoe, 502.                           Tentacles, of Hydra, 83; of Tubularia,
Stringocephalus, 296.                      90; of Calycophoridoe, 94; of PhysoStrobila, of Rhizostomidee, 107; of Tenmi-    vhoridce, 97; of Medusidoe, 101; of
ada, 169, 170.                            Hydra-tuba, 106; of Actinia, 117; of
Strombidoe, 276, 309, 317.                  Alcyonaria, 125; of Pleurobrachia,
Strombus, 317.                               131; of Holothuroidea, 161; of PolyStrophalosia, 297.                          zoa, 283; of Tunicata, 287; of CuttleStrophomnena, 296.                           fishes, 328, 329.
Strophomenidoe, 296, 298                   Tentaculites, 197, 337.
Struthio, 485.                             Tenthredinidce, 268.
Struthionidoe, 485.                        Tenuirostres, 496, 499.
Sturgeon, 392, 403.                        Terebella, 194; development of, 193.
Sturionidoe, 392, 403.                     Terebratella, 296.
Sturnidoe, 496, 497.                       Terebratula, 294, 295, 296.
Stylops, 271.                              Terebratulides, 295, 296, 299.
Sub-brachiata, 386.                        Terebratulina, 296.
Sub-kingdoms, 15.                          Teredo, 308.
Subulo, 565.                              Tergum, of the exoskeleton of Crustacea,
Suchosaurus, 445.                           203; of Arachnida, 235.
Suctoria (Infusoria), 70, 75.             Terricola, 191.
Suida, 556, 614.                          Termites, 261; communities of, 262.
Sula, 478.                                Test, of Foraminifera, 53, 54; of EchinSurinam Toad, 416.                          oidea, 144, 145; of Tunicata, 287, 293.
Sus, 557.                                 Testacella, 277, 319.
Suspecta (Ophidia), 433.                  Testudinidce, 427.
Swallow, 500.                             Testudo, 428.
Swarm-spores, of Sponges, 66.             Tetrabranchiata (Cephalopoda), 327; charSwifts, 463, 500.                           acters of, 330; divisions of, 333; disSwim-bladder, of Fishes, 374.               tribution of, in time, 337.
Swimmerets, of Lobster, 204, 205, 23.     Tetradecapoda, 224.
Swimming-bells, 95.                       Tetramera, 273.
Sycum, 69.                                Tetranychus, 240.
Sylviadoe, 498, 499.                      Tetrao, 489.
Synapta, 162.                             Tetraonidoe, 489.
Synapticulh, 123.                         Teuthidoe, 329, 335, 338.
SynaptidAe, 162.                          Thalassarachna, 241.
Syndactyli, 500.                          Thalassarctos, 578.
Syndendrium, 109.                         Thalassemacea, 187.




672                                 INDEX.
TIhalassicolla, 62, 68.                    Tritonildce, 314, 319.
Thalassicollida, 62.                       Trochilidce, 499.
Theca, 321, 337.                           Trochoceras, 333, 335.
Theca, of sclerodermic corallum, 120.      Trochocystites, 164.
Thecaphora, 90, 93.                        Trochoid shell, of Foramiilfera, 56; of
Thecidoe, 139.                               Gasteropoda, 312.
Thecididce, 296.                           Trochis", 313.
Thecidiumr, 296.                           Troglodytes, 499.
Thecodontia, 445.                          Trogon, 495.
Thecodontosaurus, 445.                     Trogonidee, 493, 495.
Thecosomata, 321.                          Trogontherium, 617.
Thelyphonidce, 242.                        Tromnbididce,' 241.
Theriomorpha, 413 (see Anourw)             Trophi, of Insects, 250.
Thoracica (Cirripedia), 214                Trophosomne, 82.
Thread-cells, 78, 80.                      Truncated Shells, 278.
Thread-wormns, 176, 177.                   Trygon, 399.
Thylacinus, 536.                           Tube-feet, of Echinus, 147; of Asteroidea,
Thylacoleo, 611.                             152; of Ophiuroidea, 154; of Crinoidea,
Thysanura, 258.                              155; of Iolothuroidea, 161.
Ticks, 239, 240.                           Tubicola, 189; characters of, 192, 193;
Tiger, 583, 585.                             development of, 193; distribution of, in
Tipulc( 265.                                 time, 197.
Tipulidve, 264, 265.                       Tubifex, 192, 198.
Toad, 416.                                 Tubiporidce, -125, 126, 130.
Tongue, of Insects, 251; of Gasteropoda,   Tubularia, 85, 89.
309; of Cephalopoda, 323; of Fishes,   Tubularida, 85 (see Corynida).
366; of Snakes, 429; of Lizards, 437; of  Tubulosa, 123, 139, 140.
Crocodile, 443; of Birds, 464, 471.      Tunicata, 275, 276; characters of, 287;
Tornatella, 318.                             respiratory process of, 289; circulation
Tornatellidce, 314, 318.                     of, 289; reproduction of, 290; homoTorpedo, 398.                                logies of, 291; divisions of, 291; disTortoise Encrinite, 163.                     tribution of, in space, 297; in time
Tortoises, 420, 421, 423, 427, 428.          298.
Tortrix, 428.                              Tunics, of Ascidians, 287.
Totanus, 483.                              Tupaia, 597.
Totipalmatce, 477.                         Turbellaria, 165; characters of, 173 
Toucan, 494.                                 divisions of, 174.
Toxoceras, 333, 334.                       Turbinated Shells, 312.
Toxodon, 531.                              Turbinidce, 314, 318.
Tracheee, 200; of Arachnida, 237; of  Turbinolidve, 140.
Myriapoda, 245; of linsecta, 253.        Turbo, 318.
Trachearia (Arachnida), 238.               Turkey, 489.
Trachyderma, 198.                          Turrilites, 333, 334, 335, 338
Trachynema, 103.                           Turritella, 314, 318.
Trachynemidce, 103, 110.                   Turritellidme, 313, 318.
Tragulus, 562.                             Turtles, 423, 426, 427.
Transformation, 35.                        Tylenchus, 179.
Trematis, 297.                             Tylodina, 319.
Trematoda, 165; general characters of,  Type, morphological, 15.
171, 172; development of, 172; habitat
of, 173.                                 UMBILICATED shell of Gasteropoda, 312.
Tremoctopus, 335; reproduction of, 325.    Umbo, 301.
Triarthra, 183.                             Umbrella, 319.
Trichecidce, 575, 576.                     Umbrella of Lueernarida, 104, 108.
Trichecus, 576.                             Ungulata, 513, 522, 525; characters of,
Trichina, 177.                               551; divisions of, 552; distribution of,
Trichocysts, 75.                              in time, 613.
Trichoglossus, 494.                         UTnio, 306.
Trichoptera, 261.                           Unionidce, 305, 306.
Triconodon, 608, 610.                      Univalve Shells, 277, 308, $11.
Tridacna, 307.                              Upupidce, 499.
Tridacnidce, 306, 307.                      Uria, 476.
Trigonia, 306.                              Usraster, 164.
Trigoniadce, 305, 306.                      Urnatella, 284.
Trilobita, 219; structure of the crust of,  UTrodela, 407; characters of, 410.
220; distribution of, in time, 234.       Ursidae, 577.
Trimera, 273.                               Ursus, 578, 616.
Tringidce, 483.                            Urus, 615.
Trionycidce, 427, 428.
Trionyx, 427.                              VACUOLES, of Protozoa, 50; of Infusoria,
Triton (Mollusca), 317; (Amphibia), 413.     71.
Tritonia, 319.                              Vaginicola, 75.




INDEX.                                   673
Vagintulus, 319.                          Vtorticella, 71; structure of, 72; reproValkeria, 283.                              duction of, 73, 74.
Valvata, 318.                             Vorticlava, 85.
Vanellus, 484.                           VPulpes, 582, 583.
Varanidce, 439.                           Vulturidce, 503.
Varanuts, 439.
Varices, 312,                             WAH, 579.
Veil, of Gonophores, 87; of nectocalyces,   Waldheimia, 296.
95; of naked-eyed Meduses, 101.          Walrus, 576, 577.
Velella, 97, 98, 99.                      WaTblers, 499.
Velellidce, 100.                          Wasps, 269.
Venenosa (Ophidia), 433.                  Water-hen, 481.
Veneridce, 306, 307; distribution of, in   Water-vascular system, of Annuloida,
time, 336.                                 141; of Echinoidea, 147; of Asteroidea,
Venerupis, 307.                             151; of Ophiuroidea, 154; of Crinoidea,
Ventriculites, 68.                          155; of Holothuroidea, 160, 161; of
Venus, 307.                                 Scolecida, 166; of Tweniada, 167; of
Venus's girdle, 134.                        Trematoda, 171; of Turbellaria, 173;
Vermes, 142.                                of Acanthocephalae 176; of Nematoda,
Ver7netus, 311, 318.                        177; of Rotifera, 182.
Verrucidoe, 214; distribution of, in time,  Weas6l, 580.
233.                                    Websteria, 139.
Vertebra, structure of, 349, 350.         Whalebone Whales, 517, 545.
Vertebrata, 345; general characters of,  Whales, 510, 511, 513, 514, 517, 521, 544,
345-349; skeleton of, 349-354; digestive    545, 548, 613.
system of, 354; blood of, 356; respira-  Wolverine. 579.
tory system of, 357; nervous system of,  Wombat, 531.
358; reproduction of, 359; develop-  Wood-pecker, 498.
ment of, 359; divisions of, 359-361.    Wrasse, 387.
Vesicle, contractile, of Protozoa, 45; of  Wry-neck, 493.
Amoeba, 50; of Paramrcecium, 71; of
Epistylis, 75.                          Xanthidia, 69.
Vesicles, of Medsusce, 101, 104.          Xiphosura, 208; characters of, 221; disVespidoe, 269.                              tribution of, in time, 234.
Vespertilio, 594.                         Xylobisus, 248.
Vespertilionidce, 594.                    Xylophaga, 308.
Vibracula, 282.
Vibrios, 36.                              ZEBRA, 555.
Vidua, 497, 498.                          Zeuglodon, 613.
Viperina, 431, 432.                       Ziphius, 613.
Virgularia, 126, 127.                     Zoantharia, 116; Malacodermata, 117,
Visceral arches, of the embryo of Verte-    129, 134; Sclerobasica, 119, 122, 139;
brates, 348.                              Sclerodermata, 122, 123, 130, 189.
Vitrea (Sponges), 67.                     Zoanthidoe, 119.
Viverra, 581.                             Zoanthus, 119.
Viverridoe, 581.                          Zoea, 218, 227, 228, 231, 232.
Voytia, 94.                               Zonites, 337.
Vole, 590.                                Zotid, 82.
Voluta, 317.                              Zoology, definition of, L
Volutidae, $13, 817.                      Zootoca, 439.