Cornell University Library Sthaca, Nem Park : COMSTOCK MEMORIAL LIBRARY ENTOMOLOGY BOUGHT WITH THE INCOME OF a FUND GIVEN BY THE STUDENTS OF JOHN HENRY COMSTOCK PROFESSOR OF ENTOMOLOGY 1915 From ~“Puvate Libary of a “Vrok. J... Comstock. Zoology for high schools and colleges, THE AMERICAN SCIENCE SERIES FOR SCHOOLS AND COLLEGES. The principal objects of the series are to supply the lack—in some subjects very great—of authoritative books whose principles are, so far as practicable, illustrated by familiar American facts, and also to supply the other lack that the advance of Science perennially creates, of text-books which at least do not contradict the latest generalizations. The books of this series systematically outline the field of Science, as the term is usually employed with reference to general education. The scheme includes an Advanced Course, a Briefer Course, and an Elementary Course. (> In ordering be careful to state which course is desired—Advanced, Briefer, or Elementary. Physics. By Groraces F, Barxer, Professor in the University of Pennsylvania. In Preparation. Chemistry. By Ira Remsen, Professor in the Johns Hopkins University. Advanced Course, 850 pp. Briefer Course, 387 pp. Elementary Course, 272 pp. Astronomy. By Simon NeEwcoms, Professor in the Johns Hopkins University, and Epwarp 8. Houpen, Director of the Lick Observatory. Advanced Course, 512 pp. Briefer Course, 352 pp. Biology. By Wiuu1am T. SEDe@wIcrK, Pro- fessor in the Massachusetts Insti- tute of Technology, and Epmunp B. Wixson, Professor in Bryn Mawr College. Purt .—Introductory, 193 pp. Botany. By C. E. Bessry, Professor in the University of Nebraska; formerly in the Iowa Agricultural College. Advanced Course, 611 pp. Briefer Course, 292 pp. Zoology. By A. 8. Packarp, Professor of Zoology and Geology in Brown University. Advanced Course, 722 pp. Briefer Course, 338 pp. Elementary Course, 290 pp. The Human Body. By H. NEWELL Mari, Profes- sor in the Johns Hopkins Univer- sity. c Advanced Course, 621 + 34 pp. Copies without the Appendix on Reproduction will be sent when specially ordered. Briefer Course, 377 pp. Elementary Course, 261 pp. Political Economy. By Francois A. WALKER, Presi dent Massachusetts Institute of Technology. Advanced Course, 490 pp. Briefer Course, 415 pp. HENRY HOLT & O©O., Pustisuers, NEW YORK. AMERICAN SCIANCH SERIES—ADVANCED COURSE LOOWOGY FOR HIGH SCHOOLS AND COLLEGES BY A, % PACKARD, M.D., Px.D. MEMBER be T. ATIONAL ACADEMY OF SCIENCES; PROFESSOR OF ZOOLOGY AND GEOLOGY IN BROWN UNIVERSITY SEVENTH EDITION, REVISED NEW YORK HENRY HOLT AND COMPANY 1889 Copyright, 1879, 1886. by Henry Hott & Co. PREFACE, Tuts book is designed to be used quite as much in the la- boratory or with specimens in hand, as in the class-room. If Zoology is to be studied as a mental discipline, or even if the student desires simply to get at a genuine knowledge, at first hand, of the structure of the leading types of animal life, he must examine living animals, watch their movements and habits, and finally dissect them, as well as study their mode of growth before and after leaving the egg or the parent, as the case may be. But the young student in a few weeks’ study in the laboratory cannot learn all the principles of the science. Hence, he needs a teacher, a guide, or at least a manual of instruction. This work is an expansion of a course of lectures for college students, but has been pre- pared to suit the wants of the general reader who would ob- tain some idea of the principles of the science as generally accepted by advanced zoologists, in order that he may under- stand the philosophical discussions and writings relating to modern doctrines of biology, especially the law of evolution and the relations between animals and their surroundings, The book has been prepared, so far as possible, on the in- ductive method. The student is presented first with the facts; is led to a thorough study of a few typical forms, taught to compare these with others, and finally led to the principles or inductions growing out of the facts. He has not been assailed with a namber of definitions or diagnoses applicable to the entire group to which the type may belong before he has learned something about the animals typical iv PREFACE, of the order or class ; but these are placed after a description of one or a few examples of the group to which they may belong. The simplest, most elementary forms are first no- ticed, beginning with the Protozoa and ending with the Ver- tebrates. In working up from the simplest forms to those more complex, it is believed that this is the more logical and philosophical method, and that in this way the beginner in the science can better appreciate the gradual unfolding of the lines of animal forms which converge toward his own species, the flower and synthesis of organic life. ‘Still the learner is ad- vised to begin his work by a study of the first part of Chap- ter VITI., on Vertebrates, and to master, with a specimen in hand, the description of the frog, in order that he may have a standard of comparison, a point of departure, from which to survey the lower forms. Particular attention has been given to the development of animals, as this subject has been usually neglected in such manuals. Some original matter is introduced into the book ; a new classification of the Crustacea is proposed, the orders being grouped into the subclasses Veocarida and Paleocar- ida. Most of the anatomical descriptions and drawings have been made expressly for this book, and here the author wishes to acknowledge the essential aid rendered by Dr. C. 8. Minot, who has prepared the drawings and descriptions of the fish, frog, snake, turtle, pigeon, and cat. In compiling the book, the author has freely used the larger works of Gegenbaur, Huxley, Peters and Carus, Claus. Rolleston. and others, whose works are enumerated at the end of the volume, and in many cases he has paraphrased or even adopted the author's language verbatim when it has suited his purpose. Besides these general works many mon- ographs and articles have been drawn upon. In order to secure a greater accuracy of statement, and to render the work more authoritative as a manual of Zoology, PREFACE. Vv the author has submitted the manuscript of certain chapters to naturalists distinguished by their special knowledge of certain groups. The manuscript of the sponges has been read by Professor A. Hyatt ; of the worms and Mollusca, by Dr. Charles S. Minot; of the Echinoderms, by Mr. Walter Faxon; of the Crustacea, by Mr. J. 8. Kingsley. Proofs of the part relating to the fishes have been revised by Professor T. Gill, whose classification as given in his ‘‘ Arrangement of the Families of Fishes,” has been closely followed, his defin- itions having been adopted often word for word. The man- uscript of the Batrachians and Reptiles has been read by Professor E. D. Cope, whose classification, given in his “‘Check-List of North American Batrachia and Reptilia,” has been adopted. Proofs of the part on birds have been read by Dr. Elliott Coues, U.8.A., whose admirable “ Key to the Birds of North America” has been freely used, the author’s words having been often adopted without quotation- marks. Dr. Coues has also revised the proofs of the pages re- ferring to the Mammals. To the friendly aid of all these gentlemen the author is deeply indebted. As to the illustrations, which have been liberally provided by the publishers, a fair proportion are original. The full- page engravings of the anatomy of the typical Vertebrates have been drawn expressly for this work by Dr. C. 8. Minot ; a number have been prepared by Mr. J. 8. Kingsley ; Prof. W. K. Brooks has kindly contributed the drawing of the nervous system and otocyst of the clam, and a few of the sketches are by the author. The publishers are indebted to Prof. F. V. Hayden for illustrations kindly loaned from the Reports of the U.S. Geological Survey of the Territories; a few have been loaned by Prof. 8. F. Baird, U.S. Commissioner of Fish and Fisheries, and the members of the U.S. Entomological Com- mission ; a number have been loaned by the Peabody Acad- vi PREFACE. emy of Science, Salem, Mass.; by the publishers of the American Naturalist, and by the Boston Society of Natural History, while forty of the cuts of birds have been electro- typed from the originals of Coues’ Key, and Tenney’s Zoology. Measurements are usually given in the metric system ; in such cases the approximate equivalent in inches and fractions of an inch are added in parentheses. Should this manual aid in the work of education, stimu- late students to test the statements presented in it by person- al observations, and thus elicit some degree of the inde- pendence and self-reliance characteristic of the original in- vestigator, and also lead them to entertain broad views in biology, and to sympathize with the more advanced and more natural ideas now taught by the leading biologists of our time, the author will feel more than repaid. Brown UNIVERSITY, Providence, R. I., October 25, 1879, PREFACE TO THE FIFTH EDITION. More radical changes have been made in this than any former edition. The Yunicata have been transferred to a position next below the Vertebrates in the group Chordata. The Merustomata. together with the Trilobites, have been laced in a cluss called Podostomata (in allusion to the fact that the head and mouth appendagesare foot-like). Their po- sition is between the Crustacea and Arachnida. The branch -irthropoda is divided into six classes, viz.: 1, Crustacea ; 2. Podostomata ; 3, Malacopoda ; 4. Myriopoda; 5, Arach- nida; 6, Insecta. The orders of insects have been increased from eight to sixteen, according to the arrangement en pp. 365, 366. For the order of Mayflies we propose the name Plectoptera (Gr. plectos, a fine net, in allusion to the finely net-veined wings), and for the Panorpide, the ordinal name Jfecrptera (Gr. mecos, length, in allusion to the long, narrow wings). Numerous minor changes and corrections have also been made. PROVIDENCE, June, 1886. CONTENTS. ——S ae PAGE INTRODUCTION 3.5 ce ciies eactiuienew ace wie tance eer te eee 1 Definition Of ZOO PY .iscceces cies airareieranieaneaeeeeireae: Givin 1 MOT phOlO By sc 52. io-sie soars wiaeaie estintsunre actus osmiere Giaawiace edward ee 5 Organs and their Functions.......... 0.0... cc ec ec eee eeee 8 CorrelationcOf Organs sxc screiiscievetssin, axe deer Veeiesaig Aeca oe ws 9 Adaptation of Organs... 2... .. 6. cece cece cece e eee ee en nees 10 Analogy and Homology.........scce ese ee eee cece eeneee 12 PUY SIOLOB Ys veces asia Sioa 5 spas Sue nite Haws GaN eutteearanaes 12 Pay Cholog ys ase. é ses 304 9405 4 aad dale eels eae eee 12 RE prod aceite cso 5 6 age w perese ace den ara Grates ietele aesucgimalee diets 13 Binibry ology vsacscces oe teceeeteen taacckeeen waciey 13 Classification... ... eeraa 2 ev ead Sra eteanens eet ae deaneve nea nctereel es 13 ZOOR CORTE P IY. sce. esau obs sata cB vk Jase BURGOS eS Ora mia guavetevenas 16 CHAPTER I. Branch 1. PROTOZOA...... cc cece ec ene eee e neces 17 Il. «2. PORIFERA (Sponges)............2..005 42 III. «3. Ca@LENTERATA (Hydroids, Jelly-fishes, ands ROlyps)is.c2 se wcioma Seat Acveomes 51 IV. « 4, ECHINODERMATA (Crinoids, Starfish, Sea Urehins, etc.......c..ceceeee 96 Vv, (65 VERMES) (WoOrMS8): 6 ta3-visa sacneiesaies aie 188 VI. “6. Mo.uusca (Bivalves, Snails, Cuttles)... 220 VIL. “7. ARTHROPODA (Crustaceans and Insects) 265 VIII. (8). VERTEBRATAS «uy vnsesieeseeaedaaus 369 IX. COMPARATIVE ANATOMY OF ORGANS..........+- 631 Organs of Digestion, the Mouth and Teeth... 631 Organs of Circulation. .......... cece eee eee 635 Organs of Respiration.............e.eeeeee 637 The Nervous System........... eee cece ecees 638 Organsof Sens@ic..nenek scacatielar eae ceee hs 640 CONTENTS. vill PAGE CHAPTER X. DEVELOPMENT... ....0ccccccccccceecene seiiaaeses 644 Metamorphosis... ...c0ceesererceacsesseeee 651 Parthenogenesis and Alternation of Genera- TODS: soy dow een site onde saan eed 652 Dimorphism and Polymorphism............. 654 Individuality cece sere a ieeus dae tee te 656 PY DTIGiby soctace ate /ie eee o:e's sUlals atahavenneeae See 657 XI. THE GEOGRAPHICAL DISTRIBUTION OF ANIMALS 658 Means of Dispersal.........020.¢000008 208 660 Division of the Earth into Faune...........- 661 Distribution of Marine Animals............- 664 Chief Zoological Faune of the Earth........ 666 XII. THE GEOLOGICAL SUCCESSION OF ANIMALS...... 668 XIII. THE ORIGIN OF SPECIES....... 00... cece cece eee 671 XIV. PROTECTIVE ‘RESEMBLANCE p16 .cssucr es eauisce create 675 XV. InsTINcT AND REASON IN ANIMALS........ .-- 680 XVI GROSSAR Ys bred ead Site tkmsmarika dees oes eee 689 RVIL. INDES ic ce cess sap viha Resi ieee Vas eewenain OOG ZOOLOGY. INTRODUCTION. Definition of Zoology.—That science which treats of liv- ing beings is called Biology (ios, life; Adyos, discourse). It is divided into Botany, which relates to plants, and Zo- ology (G¢@orv, animal ; Adyos, discourse), the science treating of animals. It is difficult to define what an animal is as distinguished from a plant, when we consider the simplest forms of either kingdom, for it is impossible to draw hard and fast lines in nature. In defining the limits between the animal and vegetable kingdoms, our ordinary conception of what a plant or an animal is will be of little use in dealing with the lowest forms of either kingdom. A horse, fish, or worm differs from an elm tree, a lily, or a fern in having organs of sight, of hearing, of smell, of locomotion, and special organs of digestion, circulation, and respiration, but these plants also take in and absorb food, have a circulation of sap, respire through their leaves, and some plants are me- chanically sensitive, while others are endowed with motion —certain low plants such as diatoms, etc., having this power. In plants, the assimilation of food goes on all over the organism, the transfer of the sap is not confined to any one portion or set of organs as such. It is always easy to distinguish one of the higher plants from one of the higher animals. But when we descend to animals like the sea-ane- mones and coral-polyps which were called Zoophytes from their general resemblance to flowers, so striking is the exter- nal similarity between the two kinds of organisms that the 2 ZOOLOGY. early observers regarded them as ‘‘ animal flowers ;’”? and in consequence of the confused notions originally held in regard to them the term Zoophytes has been perpetuated in works on systematic zoology. Even at the present day the com- pound Hydroids, such as the Serfularia, are gathered and pressed as sea-mosses by many persons who are unobservant of their peculiarities, and unaware of the complicated anat- omy of the little animals filling the different leaf-like cells. Sponges until a very late day were regarded by our leading zoologists as plants. The most accomplished naturalists, however, find it impossible to separate by any definite lines the lowest animals and plants. So-called plants, as Bacte- rium, and so-called animals, as Protameba, or certain mo- nads, which are simple specks of protoplasm, without gen- wine organs, may be referred to either kingdom ; and, in- deed, a number of naturalists, notably Haeckel, relegate to a neutral kingdom (the Protisfa) certain low- est plants and animals. Even the germs (zo- ospores) of monads like Cve//a (Fig. 1), and those of other flagellate infusoria, may be mistaken for the spores of plants ; indeed, the active fla- Fig.1.—Urel- gellated spores of plants were described as in- la,a flagellate fusoria by Ehrenberg ; and there are certain so- infusorian, or monad. with called flagellate infusoria so much like low two large ci- lia called plants (such as the red snow, or Profococcus), Gadiy maz in the form, deportment, mode of reproduc- mines tion, and appearance of the spores, that even now it is possible that certain organisms placed among them are plants. It is only by a study of the connecting links between these lowest organisms leading up to what are un- doubted animals or plants that we are enabled to refer these beings to their proper kingdom. Asa rule, plants have no special organs of digestion or circulation, and nothing approaching to a nervous svstem. Most plants absorb inorganic food, such as carbonic acid gas, water, nitrate of ammonia, and some phosphates, silica, etc. ; all of these substances being taken up in minute quan- tities. Low fungi live on dead animal matter, and promote the process of putrefaction and decay, but the food of these DISTINCTIONS BETWEEN ANIMALS AND PLANTS. 3 organisms is inorganic particles. The slime-moulds called Myzxomycetes, however, envelop the plant or low animals, much as an Ameba throws itself around some living plant and absorbs its protoplasm ; but Myxomycetes, in their man- ner of taking food, are an exception to other moulds. The lowest animals swallow other living unimals whole or in pieces ; certain forms like Amada (Fig. 2) bore into minute algee and absorb their pro- toplasm ; others engulf sili- cious-shelled plants (diatoms) absorbing their protoplasm, No animal swallows silica, lime, ammonia, or any of the phosphates as food. On the other hand, plants manu- , Fig. 2.—Ameeba. a Protozoan. The right- hand figure shows three pseudopodia on facture or produce from in- the right side; in the two other figures the ‘ pseudopodia are withdrawn in the body- organic matter starch,* sugar mass. and nitrogenous substances which constitute the food of animals. During assimilation, plants absorb carbonic acid, and in sunlight exhale oxygen; during growth and work they, like animals, consume oxygen and exhale carbonic acid. Animals move and have special organs of locumotion ; few plants move, though some climb, and minute forms have thread-like processes or vibratile lashes (cilia) resem- bling the flagella of monads, and flowers open and shut, but these motions of the higher plants are purely mechanical, and not performed by special organs controlled by nerves. The mode of reproduction of plants and animals, however. is fundamentally identical, and in this respect the two king- doms unite more closely than in any other. Plants also, like animals, are formed of cells, the latter in the higher forms combined into tissues. As the lowest plants and animals are scarcely distinguish- able, it is probable that plants and animals first appeared contemporaneously ; and while plants are generally said to form the basis of animal life, this is only partially true ; a large number of fungi are dependent on decaying animal matter; and most of the Protozoa live on animal food, as * Starch has been found by Bergh in Cilio-flagellate Infusoria. 4 ZOOLOGY. do a large proportion of the higher animals. The two kingdoms supplement each other, are mutually dependent, and probably appeared simultaneously in the beginning of things. It should be observed, however, that the animal kingdom overtops the vegetable kingdom, culminating in man. In speaking as we have of low animals and high animals, we are comparing very unequal quantities; the distance be- tween monad and man is well-nigh infinite. But there isa series or chain, sometimes broken and often with lost links, connecting the extremes ; and as there are wide differences in form, so there are great extremes in the organs and de- gree of complication of function of the simple as compared with the more complex forms. The improvised stomach of an Amceba is not comparable with the stomach of an hydra, nor is the stomach of the latter creature with that of a horse ; there is a gradual perfection and elaboration or spe- cialization of the stomach as we ascend in the animal series. So it is with organs of locomotion ; the pseudopods and cilia of the Protozoans are replaced in the star-fishes and worms by hollow tentacles or various fleshy soft appendages ; in crabs and insects by stiff, jointed limbs, with different lev- erage systems; and these are replaced in vertebrates by genuine limhs supported by bones. A comparative view of the origin and structure of organs succeeds in this book the systematic account of the animals themselves. We thus see that the organs of the higher animals are merely modificutions of organs often having the same general functions as in the lower animals; the lower or simpler have preceded in geological history the higher or more specialized forms, and thus we are, in ascending the animal series, going from the simple to the complex. For this reason the plan of this work has been to lead the stu- dent from the simpler forms of animal life to the more complex ; and though the vertebrate animals, such as fishes and dogs, are more familiar and interesting to us, the seri- ous student of zoology will feel that it is more logical and better in the end to study the animal world in the order in which the different forms have appeared—as we believe, MORPHOLOGY. 5 through the orderly operations of physical and biological laws, under the guidance of an Infinite Intelligence—a Creator whose modes of working are revealed to us in what we call the laws or processes of nature. Zoology is subdivided thus : ( Morphology or gross Anatomy, and minute Anatomy (Histology). Physiology and Psychology. Zoology. « Reproduction and Embryology. Systematic Zoology or Classification. Paleontology. Zoogeography. Morphology.—In order to properly understand Zoology, one should first study Morphology—v.e., the general struc- ture of animals. The student should first thoroughly ac- quaint himself with the anatomy of a vertebrate animal, such as a frog, as compared with that of a toad or salaman- der. The examination and comparison of the organs of animals belonging to distinct groups, is called Comparative Anatomy. The study of Morphology also includes the rela- tion of the different organs to one another, and of all to the walls of the body. Finally, we need also to study the com- position of the tissues of the different organs ; each kind of tissue being formed of different kinds of elements or cells. This department of Comparative Anatomy is called Histol- ogy (Greek, zords, web or tissue; Adyo:, discourse). It treats of the cell, and the combination of cells into germ- layers, tissues, and organs. The Cell.—The primary elements of the bodies of animals are called cells. They are microscopic portions of proto- plasm either with or without a wall. Protoplasm largely consists of protein, which is a compound of carbon, hydro- gen, oxygen, nitrogen, and sulphur, associated with a large proportion of water. Cells are originally more or Jess spherical sacs, and the protoplasm forming the cell-mass is the dynamic part of the cell. The protoplasm of animal as well as vegetable cells, the protoplasm of eggs and of the cells forming the different tissues of the animal body, as 6 ZOOLOGY. well as the entire Amcba or monad, is complex. It consists of carbon, hydrogen, oxygen, nitrogen, and sulphur, combined in nearly the same proportions. The protoplasm of different cells exerts widely different forces and capabilities. An egg- cell becomes a man, whose brain-cells are the medium of the intellectual power which enables him to write the history of his own species, and to be the historian of the forms of life which stand below him. The cell is the morphological unit of the organic world. With cells the biologist can in the imagination reconstruct the vegetable and animal worlds. The primitive form of a cell, when without a nacleus or nucleolus, is called a cytode ; genuine cells have a nucleus, the latter containing a nucleolus. Animals composed of but a single cell, such as the .4meda or an Infusorian, are said to be unicellular, Cells grow by absorbing cell-food—i.e., by the assimilation of matter from without, and this matter may be in masses of considerable size when seen under the microscope. Cells multiply by self-division. The egg-cell undergoes division of the yolk into two, four, eight, and afterward many cells; the cells thus formed become arranged into two layers or sets called germ-layers. The outer is called the ectoderm and SS the inner the endoderm. A third germ- layer arises between them, called the Fig. 3.—Germ of Sagitta, mesoderm or middle germ-layer. From ae Pee peusendoderm: these germ-lavers. or cell-layers, the cleated: cells: tissues of the body are formed, such as muscle, bone, nerve, and glandular tissue. These tissues form organs, hence animals (as well as plants) are called or- ganisms, because they have certain parts formed of a partic- ular kind of tissue set apart for the performance of a special sort of work or physiological labor. This separation of parts for particular or special functions is called differentia- tion ; and the highest animals are those whose bodies are most differentiated, while the lowest are those whose bodies are least differentiated ; hence high animals are specialized, and, on the other hand, Jow animals are stmple. Thus dit- CELLS AND TISSUES. 7 ferentiation of organs involves the division of physiological labor. Tissues.—Of the different kinds of tissues there is, first, epithelial tissue (Fig. 4) consisting of cells with a nucleus and nucleolus, and placed side by side, forming a layer. All the organs develop originally from epitheliwm, which isthe prim- itive cell-structure and forms the tissues of the germ-layers. Epithelial cells form the skin of animals, and also the lining of the digestive canal. The cells of the latter may, as in sponges, bear a general resemblance to a flagellate infuso- Fig. 4.—Vertical section through the skin of an embryonic shark, showing at # the epithelial cells, forming the epidermis; c, corium; eé, columnar epithelium.—Afte. Gegenbaur. rian, as Codosiga, or they may each bear many hairs, called cilia, which by their constant motion maintain currents of the fluids passing over the surface of the epithelium. The tissue forming glands is simply modified epithelium. Connective tissue is formed by isolated rounded or elon- gated cells with wide spaces between them filled with a ge- latinous fluid or protoplasm, and occurs between muscles, etc. An analogous (but hypoblastic) tissue forms the “ no- tocord,” wrod supporting the bodies of vertebrate embryos. Gelatinous tissue is a variety of connective tissue found in the umbrella of jelly-fishes (Awrelia, etc.). Ftbrous and elastic tissue are also varieties of connective tissue. Cartilaginous tissue is characterized by cells situated in a 8 ZOOLOGY, still firmer intercellular substance ; and when the intercel- lular substance becomes combined with salts of lime form- ing bone, we have bony tissue. The blood-corpuscles originate from the mesoderm as independent cells floating in the circulating fluid, the blood- cells being formed contemporaneously with the walls of the vessels enclosing the blood. In the invertebrates the blood- cells are either strikingly like the .lm@du in appearance, or are oval, but still capable of } changing their form. Thus blood- " corpuscles arise like other tissues, ofc RRA except that they finally” Vecome ree. Afuscular tissue is also composed of cells, which are at first nucleated and afterward lose theirnuclei. From being at first oval, the cells finally become elongated and more or less spindle-shaped, forming fibres; these unite into bundles forming muscles. Each fibre is ensheathed in a membrane called sarcolemma. Muscular fibres may be simple or striated (Fig. 5). The contractility of muscles is due to the con- tractility of the protoplasm = originating in the cells forming a the fibres. Nervous tissue is made up of nerve-cells and fibres pro- ceeding from them; the for- mer constituting the centres of nervous force, and usually massed together, forming a ganglion or nerve-centre from - : k which nerve-fibres pass to the Fig.6,—A ganglion in the clam, with periphery and extremities of *'’®* 9 © proceeding from it. the body, and serve as conductors of nerve-force (Fig. 6). Organs and their Functions.—Iaving considered the different kinds of cells and the tissues they form, we may now consider the origin of organs and their functions. The Protaumeeba may be considered as an organless being. In Ameba (Fig. 11) we first meet with a specialized portion of the body, set apart for the performance of a special function. ORGANS AND THEIR FUNCTIONS. 3 Such is the nucleus ; so that Amoeba is a genuine organism. Ascending to the flagellate Infusoria (Fig. 1), we have the flagella developed as external, permanent organs of locomo- tion. In the Hydra (Fig. 36) the tentacles are organs whose functions are generalized. Inthe worms we have or- gans arranged in pairs on each side of the body, and in gen- eral among the higher invertebrates, especially the crusta- ceans and insects, and markedly in the vertebrates, we have ‘the bilateral symmetry of the body still farther emphasized in the nature and distribution of the appendages. Of the internal organs of the body, the most important is the digestive cavity, which is at first simple and primitive in the gastrula or embryo of all many-celled animals, and as we ascend in the animal series we witness its gradual special- ization, the digestive tract being differentiated into dis- tinct portions (i.e., the esophagus, stomach, and intestine), ‘each with separate functions while the organs of respiration, digestion, secretion, and excretion originate as offshoots or outgrowths from the main alimentary tract. In like man- ner the skeleton is at first simple and afterward is extended into the different organs, the various parts of the ap- pendicular skeleton corresponding to the inercased flexi- bility and diversified leverage power ; so that limbs become subdivided into joints, and these joints still further subdi- vided as we go from the points of attachment to the peri- phery or extremities, as seen in the tendency to an irrelative repetition of joints in the limbs and feelers of crustaceans and insects, and the digits of the lower vertebrates. Correlation of Organs.—Cuvier established this princi- ple, showing that there is a close relation between the forms of the hard and soft parts of the body, together with the functions they perform, and the habits of the animal. For example, in a cat, sharp teeth for eating flesh, sharp curved claws for seizing smaller animals, and great muscular actiy- ity coexist with a stomach fitted for the digestion of animal rather than vegetable food. Soin the ox, broad grinding teeth for triturating grass, cloven hoofs that give a broad support in soft ground, and a several-chambered stomach coexist with the habits and instincts of a ruminant. ‘Thus 10 ZOOLOGY, the form of the teeth presupposes either aruminant or carni- yore. Hence this prime law of comparative anatomy led to the establishment by Cuvier of the fundamental laws of paleontology, by which the comparative anatomist is en- abled to restore from isolated teeth or bones the probable form of the original possessor. Of course the more perfect the series of bones and teeth, or the more complete the re- mains of insects or mollusks, the more perfect will be our knowledge, and the less room will there be for error in re- storing extinct animals. Adaptation.—An organ with a certain normal use or function may be adapted, in consequence of a change in the habits of the animal, to another use than the original one. To take an extreme case, the 1nadas, or climbing fish, may use its fins to aid it in ascending trees. On the other hand, by disuse organs become aborted or rudimentary. The teeth of the whalebone whale are rudimentary in the young, and are replaced by whalebone, which is more useful to the animal ; the eyes of the blind-fish are rudimentary, func- tionless. Those of certain cave-insects are entirely wanting, being lost through disuse, owing to a change of life from the light, outer world to totally dark caverns, and the con- sequent disuse of their eyes. Nature is economical. Every thing that is not of use as a rule disappears. It would bea waste of material to nourish and care for an organ in a cave- animal, or a parasitic insect or crustacean, which would be of no use to the animal. On the other hand, if the leg or tail of a newt is snipped off by some rapacious fish, it grows out again. Moreover, the animal organism is far more pliable than is generally supposed. Not only is nature continually repair- ing wounds and waste, not only is the body being contin- ually made over again, but certain animals undergo a change of form, either generally or in particular parts. If the environment is unchanged, the animal remains true to its species. The dogma of the invariability or stability of species is a fallacy. Change the climate, moisture or dryness, the nature of the soil ; introduce the natural enemies of the animal or remove them ; destroy the balance of nature, in LAW OF INHERITANCE AND TRANSMISSION. 11 other words, and the organism changes. The plants and animals of the mummies and monuments of Egypt are prob- ably the saine as those now living in that country, because the climate and soil have remained the same. The assemblages of life that have successively peopled the surface of the earth, and which are geological time-marks, have probably become extinct because they could not adapt themselves to more or less rapid oscillations of continents and islands, to consequent changes of climate and the in- coming of destructive types of life. This probably accounts for the origin, culmination, and extinction of different types of life. The earth has been, and still is, in a state of unstable equilibrium. Organic life has been and is even now, in a degree, being constantly readjusted in harmony with these changes of the earth’s surface and climate. Thus this adaptation of organs to their uses, of animals to their environment, the laws controlling the origination of new forms of life and the extinction of those which have acted their part and are no longer of service in the economy of nature, is part of the general course of nature, and evinces the Infinite Wisdom and Intelligence pervading and contin- ually operating in the universe.* Coupled with variability is the law of inheritance and transmission of variable parts, and the habits thus induced by the variation of parts. It should be observed that the portions which vary most are the peripheral parts—i.e., fingers and toes, tentacles and antenna, the skin and scales and hair; it is by modifications and differences brought about in those: parts most used by animals that the multi- tudes of specific forms have resulted. There is, as Darwin States, a general tendency of organisms to vary; the laws accounting for this tendency to vary have yet to be formu- lated ; though the attempts of Lamarck in this direction laid the way for the discovery and application of the funda: * That animals and plants are self-evolved, that the world has made ‘itself, and that all is the result of so-called physical and biological laws ‘operating from within outward, is as inconceivable as the medieval capable of automatically throwing out pseudopodia, and reproducing by simple self-division of the body-mass into two individuals, or by division into a number of germ-like or spore-like young, which increase in size by absorption of the protoplasm of other organisms. Group 1. Gymnomonera, comprising the genera Protameba, Protogenes, and Myxodictyum, which do not become encystcd. Group 2. Lepomonera, which become encysted and protected by a. case, as in the genera Protomonas, Protomyxa, Vampy- rella, and Myxastrum. Cuass II.—Ruizopopa (Root Animaicules). General Characters of Rhizopods.— strength and lightness to the ¢ shell (Figs. 80, 81, 82). The outlet of the alimentary canal is situated on the aboral Fig. 80.—Schematic figures of a Sea-urchin. A. from the oral end; B, from one side. Ambulacra indicated by rows of dots. 7, ambulacral; é7, interambulacral areas; 0, mouth; @, vent.—After Gegenbuur. (abactinal) or upper end of the shell, while the madre- poric plate is situated upon the top or end of the shell (as the animal moves mouth downward), being a modifica- Fig. 81.—Aboral end of the shell of an Echinus, with the upper end of the rows of pates, a, ambulacral area; 2, interambu- acral area; g, genital plates; ig, intergeni- tal plates; m, one of the genital plates ee madreporic plate; 2, anal opening in the aboral area surrounded by the genital plates. The tubercles to which the spines. are attached are only drawn on one ambula- cral and one interambulacral area; on the- former are also drawn the tion of one of the genital pores throngh plates (Fig. 81, m). There are five large plates, one at each end of the interambulacral zones meeting on the aboral end of the body ; in them ure the ovarian openings through which the eggs escape ; these ae the suckers protrude.— After Gegen- QUT. ANATOMY OF SHA-URCHILNS. 119 five plates are called the genital plates, while in each of the five smaller plates at the end of each ambulacral series is an ; eye-speck. The pedicel- ; lari are three-pronged, knob-like spines, scat- tered over the body, es- pecially near the mouth. They partly serve to re- move the fecal matter, but their main function is not known. Besides the pedicel- larie, Lovén has discov- ered on most living Echini, with the excep- tion of Cidaris, small button-like bodies called Fig. 82.—View of the caleareous net-work “2 heridia, situated ne from a plate of the integument of a Sea-urchin short stalk, moving on & (Cidaris). 6, section perpendicular to the hori- a zontal net-work of straight rods.—After Gegen- slightly marked tubercle. a They are supposed to be sensorial, probably organs of taste and smell, The internal anatomy of the sea-urchin may be best studied Fig. 83.—Shell of a Sea-urchin (Strongylocentrotis lividus). a, anus; 0e, esophagus #, intestine; s, one of the rods of the tooth-apparatus; m, muscles of the jaws; p, ves sels of the sucking feet; po, extremity of the water-vessel; cw, ocular plate; v, ovary. by cutting the shell into two halves, oral and aboral. Remov- ing the aboral end, the digestive canal may be seen in place. 420 ZOOLOGY, It consists of a narrow cesophagus (Fig. $3, e), more or less pentagonal near the mouth, dilating into the stomach ; and of a terminal intestine. The long stomach passes from left to right around the interior of the body, then turns up toward the aboral end, and curves back in the opposite course, again passing around the body from right to left, forming two series of loops partly enclosing the ovaries ; it is held in place by a broad, thin membrane or ** mesentery.”’ The reproductive and other organs are much as described in the star-fish, there being five ovaries or spermuaries, the sexes being distinct. The nervous ring around the mouth sends off five nerves along the ambulacra, which are accom- panied by a water-vascular canal sending branches to the tentacles, and a pseudo-hemal canal, there being an oral and aboral (anal) hemal ring (their presence is denied by Hoff- mann), as well as an ora] water-vascular ring, with five Polian vesicles (present only in the true Echini and Clypeastroids), a stone-canal and a fusiform tube or “‘ heart ’’* next to it, while the alimentary canal is accompanied by two hemal vessels, one on the ‘‘ dorsal’’ and the other on the free or ventral side, communicating with a lacunar network in its walls. In Echinus it is difficult to perceive any bilateral sym- metry, the parts radiating, as in the star-fish, from the cen- tre; but in the Sputangus and allied forms it is easy to di- vide the animal into a right and left side, and the body is more or less elongated, asin Powrtalesia (Fig. 87°, the mouth being situated at one end and the anus at the other. The mode of development of the common sea-urchin (Fig. 78) has been discovered by Mr. A. Agassiz. The earli- est stages are much as described in the star-fish. The form of the pluteus larva is quite remarkable, there being eight very long slender arms supported by slender calcareous rods projecting from the body, and, during the movements of the animal, opening and shutting like the rods of an um- brella. The body is provided with a sinuous row of vibra- * Tt should be observed that the latest and best observers are at vari« ance regarding the structure and function of the so-called Echinoderm “"Beart,”? DEVELOPMENT OF THE SEA-URCHIN. 121 tile cilia. When the larva is twenty-three days old the ru- diments of the five tentacles of the sea-urchin appear. By this time the pluteus-form is acquired, and also at this pe- riod the sea-urchin growing upon the deciduous pluteus scaffolding has concealed the shape of the digestive cavity of the larva, and the spines are so large as to conceal the tentacles. The body of the pluteus is gradually absorbed by the growing sea-urchin ; the spines and suckers of the latter increasing in size and number with age, until by the time the larval body has disappeared the young Echinus is more like the adult than the star-fish at the same period in 84.—Hemiaster_ Philippii, with the young in two of the marsupia.—From write Thompson's Voyage of the Challenger. life. Grube has found that Anochanus sinensis, supposed to have come from the Chinese or East Indian seas, has no metamorphosis; while Hemiaster cavernosus of Chili was found by Philippi to carry its young in marsupia and to develop directly. Several species of sea-urchins in the cooler portions of the South Atlantic, especially at the Falkland Islands and Kerguelen Island, also develop directly in marsupia or brood- hollows, without passing through a metamorphosis. In Hemi- 122 ZOOLOGY. aster Philippti Gray (Fig:. 84 and 85), from the latter island, certain of the ambulacral plates are greatly expanded and depressed ‘‘ so as to form four deep, thin-walled oral cups, sinking into and encroaching upon the cavity of the test, and forming very efficient protective marsupia.’? The spines are so arranged that a kind of covered passage leads from the ovarial opening into the marsupium, and along this passage the eggs, which are very large (a millimetre in diameter) are passed and arranged in rows, each egg being kept in place by two or three spines bending over it, Here the eggs develop, and the embryos, after the calcareous roe Wyse Dhenienine Vorego or the cusicnger ee ieteniind plates once begin to develop, rapidly assume the parent form ; when they leave the marsupium they are about two and a half millimetreslong. In Cidaris nutriz Wyville-Thompson the eggs are protected in a sort of tent by certain spines near the mouth. Tlere the young develop without a meta- morphosis. The allies of these forms in the Northern At- lantic are either known or supposed to be metabolous; and Sir Wyville-Thompson states that no free-swimming Echi- noderm larve (pluteus, etc.) were seen by the Challenger Exvedition in the Southern Ocean. PRINCIPAL FORMS OF SHA-URCHLNS. 123 Taking a rapid survey of the principal forms of sea- urchins, we may divide the class of Hchinoidea into two or- ders: the Palechinida, or older sea-urchins, in which the shell is composed of more than twenty rows of plates; and the Autechinida with twenty rows of plates. * Order 1. Palechinida.—Comprises first the suborder Me- lonitida, in which there are more than ten rows of ambula- eral plates, represented by Melonites of the coal formation, and Protechinus, Palechinus, Archeocidaris, etc. In the ‘second suborder Hovidaria, there are ten rows of ambulacral plates. A type of the group, Locidaris Kaiserlingti, appears an the Permian formation. Order 2. Autechinida.— ‘To this division belong sea- ‘urchins with twenty rows of plates. The first suborder is the Desmosticha, comprising those sea-urchins with band- like ambulacra extending from the mouth to the oppo- site extremity, and of more or less regular, flattened, spherical form. Such are Cidaris, Echinus, Echinom- ; Fig. 86.—Echinarachnius parma, com- tra, Clypeaster, and H#ehi- monSand-cake. Natural size.—After A. a e Agassiz. narechnius. The L£chinus esculentus Linn., of the Mediterranean Sea, is as large as an infant’s head, and is used as an article of food. In Clypeaster the body is large and the shell very solid. C, subdepressus Agassiz is common on the Floridan coast. An orbicular flattened type are the sand-cakes, of which the Echinarachnius parma Gray (Fig. 86) is abundant in the shallower portions of the North Atlantic, from low-water mark to forty fathoms. It is replaced southward from Nantucket to Brazil by Mellita testudinata Klein. The last suborder, Petalosticha, is characterized by the * These are terms proposed by Haeckel, who regards these divisions ‘as subclasses, but we think they should more properly be called orders. 12+ ZOOLVGY. leaf-like ambulacra, and the irreguiarly heart-shaped, often elongated, form of the shell, an anterior and posterior end. being well defined. ‘They for the most part live buried in the sand or sandy mud, not moving about so actively as the Desmosticha. Of the family Spatangide the singular genus Pourta- lesia (Fig. 87, P. Jeffreysii Wyville-Thompson) deserves notice, the species of which are bottled-shaped, with a thin, transparent shell. The transition from such a form as this to the Holothurians is not a very extreme one. This genus, A. Agassiz states, is the living representative of Jn- fulaster of the Cretaceous period. P. miranda A. Agassiz was dredged in the Florida Straits, in about three hundred Fig. 87.—Pourtalesia Jeffreysii, slightly enlarged.—After Wyville-Thompson, and fifty fathoms, and by British naturalists in the Shet- land Channel. P. Jeffreysii was dredged in six hundred. and forty fathoms, near the Shetland Islands. Spatangus is distinctly heart-shaped, as is Hemiéaster. An interesting deep-sea or abyssal form not uncommon in deep soft mud, at the depth of one hundred fathoms, off the- coast of Maine and Massachusetts, and extending from Flor- ida around to Norway, is Schizaster fragilis Agassiz. Echinoderms range to a great depth in the ocean, and are: largely characteristic of the abyssal fauna of the globe. In space they are widely distributed, there being but two. Kchinid faune on the eastern coast of the United States, one arctic, the other tropical. While a large number of species characterize the urctic or circumpolur regions, the FOSSIL ECHINODERMS, 125 larger proportion of species are tropical and subtropical. My. A. Agassiz divides the Echinid fauna of the world into four realms: the American, Atlantic, Indo-Pacific, and Australian. Though Crinoids were the predominant type of Echino- derms in the paleeozoic rocks, a few star-fish and Ophiurans appeared in the Upper Silurian period, and with them were associated one species of sea-urchin, Palechinus, though the genus was more numerously represented in the Coal period. Some Paleozoic forms resembled the living gen- era Calveria and Phormosomu, and belong to the extinct Carboniferous genera Lep/dechnus and Lepidesthes ; in all these forms, fossil and recent, the interambulacral plates overlapped one another so as to give a certain amount of flexibility to the shell. This feature existed in a less de- gree in Archeociduris. The characteristic American car- boniferous genera are Melonites, Oligoporus, and Lepidecht- nus. The Permian Zoczduris is nearly allied to drcheoci- daris, so that it is a true paleozoic type (Nicholson). In the Mesozoic epoch (Trias, Lias, and Jura) appeared a more modern assemblage of Spatangide, and genera such as Hemiciduris and Hypodiadema, closely allied to the Cida- ride proper, appeared in the Trias. The Jurassic beds are characterized by genera allied to Diudema, Echinus, Ci- daris, and a number of species of the families Cassidulide and Galeritide. A large number of genera survived in the Cretaceous period, which, however, is characterized by the marked development of the Spatangide. In the Upper Cretaceous the earliest Clypeastride appeared, while the Tertiary Echinid fauna is quite similar to the present one. The striking fact in the geological history of the class is the persistence of many of the cretaceous genera in the abyssal or deep-sea fauna of the present time (A. Agassiz). 126 ZOOLOGY. Cuass IIL.—ECHINOIDEA. Spherical, heart-shaped, or disk-like Echinoderms, with a solid shell of tm- movable plates, bearing interambulacral spines ; with a mouth and anal opening, the mouth in most of the species armed with fire teeth ; am- bulacral feet irell developed. The sexes distinct, Development either direct, or, as in most cases, by a marked metamorphosis from a pluteus larca, Order 1. Palechinida.—Shell composed of more than twenty rows of plates. Suborder 1. Velonztida (Melonites, Protechinus, Palechinus, Archzocidaris). Suborder 2. Hoctdaria (Eoci- daris). Order 2. Autechinida.—Shell composed of twenty rows of plates. Suborder 1. Desmostici.a (Cidaris, Echinus, Strongylocen- trotus, Echinometra, Clypeaster, and Echinarachnius). Suborder 2. Petalosticha (Echinobrissus, nochanus, Pour- talesia, Spatangus, and Schizaster). Laboratory Work.—We have already given some hints as to the mode of dissecting sea-urchins, which should be done under water in deep pans. Great care must be taken in removing the digestive canal, which is very delicate in itself, and usually filled with sand. In study- ing the water-vascular and blood-vessels, careful, skilful injections with -carmine are indispensable. The spines may be studied by making thin longitudinal and transverse sections. The test, or shell, should be de- muded of the spines in order to study the relations of the ambulacral, interambulacral, and genital plates. Crass IV.—HoLotHuRorDeEa (Sea-cucumbers, General Characters of Holothurians._We now come to Echinoderms in which the body is usually long. cylin- drical, with a tendency to become worm-like, and in cer- tain genera, as Synapta, Chirodota, and Evpyrgus, it is difficult both in their larval stages (Synapta) and in the external and internal anatomy of the adults to separate them from worms like Sipunculus ; authors have therefore been led to the adoption of one of two views: first, either that the worms and Echinoderms have had a common origin, and the latter, though truly radiate, have no near affinities (though strong analogies) with the Celenterates, or the re- HABITS OF HOLOTHURIANS. 127 ‘semblance between the two branches (Echinoderms and worms) is one simply of analogy, and involves no blood-rela- tionship. On the other hand the radiated arrangement of parts and the development and relations of the water-vas- cular system ally them, through the Ctenophores, with the Actinozoa and Hydroida, and it seems more natural to re- gard the Echinoderms as forming a branch of animals in- termediate between the Hydroida and the worms, there being certain low worms with a water-vascular system. But the student will be better able to appreciate these general ‘questions after a more or less thorough acquaintance with the forms and structure of the pres- ent group. For this purpose he should first examine living sea- cucumbers, and then carefully ‘dissect them. A detailed study of the anatomy of a Pentacta or a Holothuria, one a northern the other a subtropical and tropical form, and of a Synapta, found everywhere along our coast in sand below tide-marks, will give the groundwork ; and this knowledge, autoptically acquired, can then be corrected and extended by reading Monographs or compiled state- ments to be found in the more authoritative general works on iS ‘comparative anatomy. : Fig. 88.—Pentacta Siondosa.— Living Holothurians can be pro- F!™ Tenney’s Zoology, -cured with the dredge or dug out of the sand between tide- marks. They should be kept in aquaria, and their moye- ments watched as well as their mode of locomotion, and the action of their branchiz or external gills (tentacles). The common sea-cucumber, north of Cape Cod, and ex- tending through the Arctic regions around to Great Britain, is Pentacta frondosa Jaeger (Fig. 88). It lives from ex- 128 ZOOLOGY. treme low-water mark to a depth of fifty fathoms. It is of a tan-brown color, from six inches to nearly a foot in length, and in its form and the corrugations of its tough, leathery skin resembles a cucumber in nearly all respects except ‘color. There are five series of ambulacral feet, each series consisting of two irregular rows. Around the mouth is a circle of ten much-branched tentacles or gills (homolo- gous with the ambulacral feet). On laying the body open by making a cut extending from the mouth to the vent, the thick muscular walls of the body may be observed, and the general relations of the viscera to the body-walls, which have nothing of the radiate arrange- ment of parts, so clearly marked in the other Echinoderms,. the ambulacra, tentacles, and longitudinal muscles alone be- ing arranged in a radiate manner.* Unlike other Echino- derms, the madreporic body is internal, and there is a ca- pacious cloaca or rectum, and a large vent. On the inside of the body-walls are numerous small cir- cular (transverse) muscles forming slight ridges, which serve to contract the body, and five ‘double large longitudinal muscles (Fig. 89, 7) lying in the ambulacral zones. The mouth is surrounded by a muscular ring, from which arise ten large, much-branched tentacles. The pharynx, or the portion corresponding to ‘‘ Aristotle’s lantern,’’ of the sea- urchin is broad and short, with five large retractor muscles (r) originating from the ambulacral or longitudinal muscles on the anterior third of the body. The stomach is short, not much wider than the intestines, with well-marked trans- verse folds within. The intestine (é) is several times longer than the body, with longitudinal small folds, and held in place by a large, broad mesentery which accompanies the in- testine through the greater part of its length. The intes- tine terminates suddenly, in a large cloaca (¢), Srom which. * In Eupyrgus and Echinocucumis it is difficult to perceive any radia-. tion in the body except in the unbroken circle of tentacles, while in Sipunculus and allied worms (Gephyrea) the tentacles form a complete circle, and these worms have a ring-canal and an imperfect or rudi- mentary system of vessels thought by some authors to correspond to the water-vasculur system of Echinoderms. ANATOMY OF HOLOTHURIANS. 129: on one side arises the “‘ respiratory tree,’’ which has but one main stem, and is only occasionally held in place by mus- cular threads. The branches are numerous, and are smaller Fig. 89.—Pentacta frondosa. t, tentacles; J, longitudinal muscles; #, retractor mus~ cles of the tentacular system; é, intestine; c. cloaca; b, er tree; vr, water- vascular ring or ring-canal, v, radial water-vascular canal; m. madreporie body; pp, polian vesicles; am, ampulle; @, a’, pseudo-hemal'contractile vessels (from Carus);, 0, ovary; 0v, ee J.8. Kingsley from a dissection made by the author. 5 2 and paler than the ovarian tubes. The water enters the cloaca (c), passes into the respiratory tree (2), oozes out of 130 ZOOLOGY. the ends of the branches, filling the body, whence it is taken up by the madreporic body and carried into the water- vascular system by the narrow duct on the left side of the pharynx. Besides being respiratory, this organ is supposed to be depuratory in its function. In some Holothurians certain organs (the Cuvierian organs), supposed by Semper to be organs of defence, as they are readily thrown out when the animal is disturbed, are attached either to the stem of the respiratory tree or to the cloaca. The madreporic body (m) forms a rosette, partly surrounding the membrane at- tached to one side of the pyloric end of the stomach, and leads by the madreporic canal, which is closely bound down to the pharynx, to the ring-canal (vr). Also connected with the ring-canal are two enormous Polian vesicles (p, p), which are nearly two thirds as long as the body ; by slitting up their base with scissors they can be followed to the ring- canal. The latter (vr) is a capacious canal surrounding the mouth, and can be detected by laying open the oral-opening, and then by cutting across the longitudinal muscles (as at 7’) the radial vessels may be followed along the body under the muscles. Just above the ring-canal is situated the nervous ring (nr), and its radial nerves (7) can be traced along and outside of the radial water-vascular canals. The ampulle (am) are red, conical, flask-shaped, conspicuous organs, lying irregularly, a row on each side of each longitudinal muscle. ‘They are filled with water from the small lateral vessels of the radial water-vascular canals. The single ovary is com- ‘posed of a large mass of long tubes, which are larger than and tangled up with the branches of the respiratory tree. ‘The oviduct is attached by a membrane to the stomach, and opens between two of the tentacles on the edge of the mouth. The blood or pseudo-hemal vessels * are difficult. without very fine dissections, to be made out. The svstem consists of a plexus of vessels lying next to the ring-canal, from which two vessels (7, a’) pass along opposite sides of the in- * These vessels in Fig. 89 have been copied from Carus’ Icones Zo- otomice ; in other respects the drawing represents the anatomy of PP. frondosa. ANATOMY OF HOLOTHURIANS. 131 testine. A fluid containing nucleated cells fills both the pseudo-hemal and water-vascular canals. Holothuria floridana Pourtales is a large, dark-brown sea-cucumber, with the feet scattered irregularly over the body, and with smaller tentacles than in Pentacta, which is. abundant just below low-water mark on the Florida reefs, and grows to about fifteen inches in length. The aliment- ary canal is filled with foraminifera and pieces of shells, corals, etc.; it is about three times the length of the body,. and ends in a much larger coecum than that of Pentacta. There are two widely separated branches of the ‘ respira- tory tree,’’ one being free, and the other, tied to the body- walls by thread-like muscular attachments, extends to the pharynx. The pharynx is calcareous, while in Pentacta it is muscular. On the madreporic body is a group of about thirty pyriform stalked bodies, the longest, including the- stalk, about a quarter of an inch in length. Succeeding these bodies, and situated on the madreporic canal, leading to the ring-canal, are a large number of Polian vesicles, the- largest one an inch in length. The duct passes spirally. nearly round the csophagus, and empties into the ring- canal by the ducts nearly a quarter of an inch apart. In connection with the tentacles or branchiz are twenty long,. slender tentacular ampulle, not present in Pentacta and Thyone. The ovarian tubes are very small, some enlarging: and bilobate at the end. Closely allied in external form to Holothuria floridana, though belonging to a different family (including Pentacta),. is Thyone briareus (Lesueur), which lives just below tidal marks, from Long Island Sound to Florida. In this genus the ambulacral feet are not arranged in rows, but scattered over the surface of the body. This species is very common, and as it is more accessible to the student than any other of the sea-cucumbers, we give some points in its anatomy as compared with Pentacta, with which it is more close.y allied. than to Holothuria. In a specimen about eight centi- metres (three inches) long the intestine is over two metres. (about seven feet) long, the cesophagus opening into an oval stomach less than an inch in length. The tentacles. 132 ZOOLOGY. are capable of being very deeply retracted, and as in Pentacta there are no tentacular ampulle. The small madreporic body is much as in Pentacta, and connects with a duct (madreporic canal) leading to the ring-canal. There are three Polian vesicles, one fusiform and an inch in length, the two others slenderer. The cloaca is of mod- erate size, as in Pentacta, and the respiratory trees divide at once into two very bushy branches. The ovarian tubes form a brush or round broom-like mass or tuft, about an inch long, the tubes small, yellow, and of nearly uniform length, the oviduct straight and bound down to the walls of the body. We might here mention the most aberrant type of Holo- thurians, the Rhopalodina described by Sernper, who states that the body is flask-shaped, with the mouth and vent situ- ated near each other on the smaller end of the body. Thc mouth is surrounded by ten tentacles, and there are ten -apille around the anus. There is a spacious cloaca or respiratory tree. “* Ten ambulacra diverge from the centre of the enlarged aboral end of the body, and extend like so many meridians to near the commencement of the neck of the flask. In correspondence with each ambulacrum isa longitudinal muscular band ; and it is an especial peculiarity of Rhopalodina that five of these are attached to the anal circlet, and five to the circum-cesophageal circlet’’ (Huxley). The earlier stages of development of Holothurians, so far as known, is like that of star-fishes. The larvawhen fully grown is called an auricular/a. It is transparent, cylindri- cal, annulated, with four or five bands of cilia, and usually with certain ear-like projections, from which it derives the name originally given to this larval form. Before the auri- cularia is fully formed the young Holothurian begins to bud out from near the side of the larval stomach, the calcareous, cross-like spicules appear, and the tentacles arise. The ear- like projections disappear, the auricularia thus becoming cylindrical. Itissoon absorbed by the growing Holothurian, which in some genera is strikingly worm-like, and it seems that the Holothurian is more directly developed from the larva than in the case of the star-fish and sea-urchins, the METAMORPHOSIS OF HOLOTHURIANS. 133 ‘metamorphosis being less marked—z.e., growth is more continuous, as in the Crinoids. In Holothuria tremula and Synaptula vivipara there has been observed a very slight metamorphosis, the young de- veloping directly in a marsupium, as in the star-fishes and sea-urchins. Cladodactyla crocea Lesson, of the Falkland Islands, according to Sir Wyville-Thompson, carries its young in a sort of nursery, being ‘‘ closely packed in two con- tinuous fringes adhering to the water-feet of the dorsal am- bulacra.’’? THe also found that in Psolus ephippifer Wyvilie- Thompson, which is covered with calcareous plates, there is .a dorsal group of larger tessellated plates, each supported by a broad pedicel embedded in the skin. Under these mushroom-like plates brood-cavities or cloister-like spaces -are left between the supporting columns, and in this archi- tectural marsupium the embryos directly develop into sea- cucumbers. It follows that in all free-swimming Echino- derm larvee, there is a true metamorphosis as distinct as in the butterfly, while in other forms in which development is direct. the embryo is sedentary and lacks the cilia and vari- -ous appendages so characteristic of the ordinary larval Echinoderms ; thus there are different stages in the differ- ent classes of Echinoderms between direct development o1 continuous growth, and a complete metamorphosis like that of the star-fish or sea-urchin, in which the pluteus or larva is but a temporary scaffolding, as it were, for the building up of the body of the adult. Turning now to the classification of the Holothnrians, and beginning with the lowest, simplest, most generalized forms (which are also remarkably worm-like), and ascend- ing to higher or more complicated forms, we find that there are two orders, those without feet (Apoda) and those with -ambulacral feet (Peduta).* * It is possible that the Holothurians shouid he divided into two sub- ‘classes, one Diplostomidea Semper, in which the body is spherical and the mouth and anus are close together, with ten ambulacral rows, etc., and the normal, cylindrical, bipolar Holothurians. Semper’s Diplostomz- -dea is based on Rhopalodina lageniformis Gray, from the Congo Coast, -and regarded hy Semper as the type of a fifth class of Echinoderms. 134 ZOOLOGY. Order 1. Apoda.—The simplest apodous form is the Eupyrgus scaber Littken, in which the body shows no external signs of longitudinal muscles, though there are five small ones, and is covered with spine-like, soft papilla bearing calcareous plates. We have dredged it. frequently on the coast of Labrador in shoal- water. It has a circle of fifteen unbranched. tentacles, and is about one centimetre long. It also occurs in Greenland and Norwegian waters. J/yriotrochus has a transparent skin dotted with minute white spots, which, when magnified, appear to be wheel-like, calcareous plates. It has a single Polian vesicle, and there is no respiratory tree nor Cuvierian appendages (Huxley). We have dredged this beautiful form (JZ, Rinkii Steenstrup) in sand, in shoal- water, on the coast of Labrador. the foot furming a creeping disk; thebody either nuked and bilaterally sum- metric, or enclosed in « spiral shell, and consequently behind the hea& asymmetrical. Mouth with pharyngeal teeth and a lingual ribbon (odon- tophore). Nertons system consisting of four pairs of ganglia, the brain well dertloped. The intestine usually ending near the mouth. The heart with usually a single auricle. Breathing by a single gill, or a lung like gill ; @ double kidney, but forming a single inass, S xes united or sepa- rate. Young pissing through « morula, gastrula, sometimes a trocho- sphere and usually a celiger stage; in the land-snails development direct. Subclass 1, Scaphopoda—No head, several long thread-like tentacles : foot long, trilobed. “licll long, conical, open at each end. A single order \enoconche. (Dentalium, Siphonodenta- lium.) Suiclass 2. Pteropoda —Bods with two wing-like expansions (velum) on the front part of the foot, for -wimming ; body naked or shelled. Hermaphrditic. Larva with a velum and shell. Order 1. T..costornata (Hyalea, Cleodora, Cavolina), Order 2. Gymnosomata. (Clione). Subelass 3. Gastrapoda.—Order 1, P:osobranchiata (Halictis, Patella, Trochus, Littorina, Lunatia, Pa'udina, Turritella, Ianthina, Cyprea, Strombus, Cassis, Buecinum, Nassa, Purpura.) Order 2. Opisthobranchiata, (Bulla, Aplysia. Eolis, Doris.) Order 3. Pulmonata, \Limnezus, Planorbis, Auricula, Helix, Bulimus, Limax). GENERAL CHARACTERS OF CEPHALOPODS. 253 Subclass 4. Heteropoda.—Naked or shell-bearing mollusks, with a large prominent head, large movable eyes, and foot with a keel- like fin. The sexes are distinct. Respiration by gills. Or- der 1. Pterotracheidw.—Pterotrachea, Carinaria, Firoloides, Order 2, Atlantide,—Atlanta (living) ; Bellerophon (fossil), Laboratory Work.—The Gastropods are very difficult to dissect, and it is quite essential that the -specimen be freshly killed, and that it has died as fully ex- panded as possible. For this purpose they should be al- lowed, as Verrill suggests, to die in stale sea-water, with the parts expanded ; when the animal is nearly dead, the soft parts can be forcibly held out by the hand while the animal is killed by immersion in alco- hol. Shells and other marine animals may be obtained by means of the dredge (Fir. 211), an iron frame with a net, to which is attached ua Fig. 206.—Dredge. rope and weight. Crass IIl.—CepHatopopa (Sguids and Cuttle-fishes). General Characters of Cephalopods.— The essential features of this class may be observed by a study of the com- mon squid, represented by Fig. 207. The following account is based on dissections of Loligo Pealit Lesueur (Fig. 208). A general view of the body of the entire squid, with its arms and suckers, is given in the accompanying illustration (Fig. 207) of Loligo pallida Verrill. The body is fish-like, pointed behind, and with two broad fleshy fin- like expansions at the end of the body. The head is dis« tinct from the mantle or body, and the mouth is surrounded by a crown of ten long stout pointed arms, provided on the inner side with two rows of alternately arranged cup-shaped suckers, each sucker being spherical, hollow, with a horny 254 ZOOLOGY. rim inside. Two of the ten arms arise from the under side of the head; they are twice the length of the eight others, and oval at the end. On each side of the head behind the tentacles are the remarkably large eves, which, though usuai- ly said to be more like the vertebrate eye than those of any other invertebrate, are really constructed fundamentally on the same plan as the cye of the snail; differing in several important respects from that of a Vertebrate, the resem- blances between the two being superficial, while the struc- ture of the eyes of mollusks is quite unlike that of Crusta- ceans, insects or Vertebrates. The mantle loosely invests the front of the body next to \ the head, so that the water \| passes In around the neck in ds | order to bathe the gills, which A341! are quite free from the visce- 3 ralmass. The mantle is beau- / tifully colored and spotted, the change of color being due to the change in form of the pigment masses or chromato- phores, which are under the influence of the peripheral nerves. The mantle is supported = one Thea Watlecl aoe eter a oe hoy pee (Fig. 209). 0 pen- shaped thin support, ex- tending from the upper side of the anterior edge of the mantle to the end of the body. In the Sepia of the Medi- terranean Sea this is thick. formed of limestone, and is called the ‘ cuttle-fish bone.” The organs of digestion consist of a mouth, pharynx, cesophacus, stomach ‘and intestine. The mouth is situated ll WS li is eq te S dissections. Fie. 208.—Anatomy of common squid.—Drawn by J.S. Kingsley, from the author’g The brain (@) in nature is situated above the cesophagus., 256 ZOOLOGY. between the tentacles, and is surrounded by a double fleshy lip, the outer fold of the lip bearing short fleshy pointed lobes opposite the spaces between the tentacles. The pharynx is larse, muscular and bulbous. contain- ing two powerful horny teeth, shaped like a par- rot’s beak ; the two jaws are unequal, the lower one the smaller, moving vertically. On opening the base of the smaller jaw, the lingual ribbon or odontophore (Fig. 208, yo) may be discovered ; it consists of seven rows of teeth, somewhat us in those of Architeuthis Hartingti (Fiz. 210). The cesophagus (@) is long and slender, with two long oval salivary glands (sg) on each sicle of it, just behind the pharynx; the salivary duct leading into the mouth-cavity. The cesophagus has several internal longitudinal folds, and passes on one side of the large liver (7) which lics in front of the stomach, and which is about one third as long as the whole body, extending Lack- wards. On laying open the stomach, a series of large ey ie y semicircular transverse curved valves may be Fig. 209,.- seen, occupying the anterior third of the stom- Pen of Loligo , pallita. dorsal - ce as et are scattered glandalar Sea ane assess ne pyloric end opens into an oval Verrili. cecum (ca) with about fourteen longitudinal, thin high ridges. There is no spiral portion attached. The intestine (iz) is straight, thick, and passes forward, ending in a large vent (a), the edges of which are lobulated. The *‘ink- ae a oa ' Lag” (Fig. 208, 2) can be recog- bAyy ne | ae) < nized as 2 purse-like silvery sac, 7, ~ A e. filled with a dense pigment, the ” Po sepia, which, like the Chinese Fig. 210.—Part of lingual ribbon of Fe : Archileuthis Hartingii ; enlarged. sepia, can be used for drawing. The duct is straight, and is intimately attached to the in- testine, ending close to the vent, both the vent and cp en- ing of the duct of the ink-bag being situated at the bot- tom of the funnel or siphon (Fig. 208, f), which is a large ANATOMY OF LOLIGO. 257 short muscular canal with a large orifice extending on the ventral side to the base of the tentacles. Through this siphon passes excrementitious matter as well as the ink, and the stream of water which is forcibly ejected from the siphon, thus propelling the squid through and sometimes out of the water. The two gills (Fig. 208, 7), are large, long slender bodies, at- tached by a thin membrane to the inner wall of the mantle, and are quite free from the visceral mass. From the bran- chial vein arise two rows of lamelle like the teeth of a comb. At the base of each gill is a flatted oval body, the ‘‘bran- chial heart,” or auricle (Fig. 208, 52). The auricles are quite separate from the large four-cornered flat ventricle (Fig. 208, /), lying in front of the stomach, and which throws off an artery from each corner, the aorta being the largest, and passing parallel to the cesophagus, while a large vein (vena cava) is sent off to the gills from a circular sinus in the head. The nervous system is more complicated than usual in Mollusca, and is very difficult to dissect. In Loligo Pealii the highly concentrated nervous system is mainly contained in an imperfect cartilaginous brain-box (cg), a slight anticipation of the skull of the Vertebrates. The brain (supracesophageal ganglion, Fig. 208, d) rests upon the very large optic nerves, which dilate at the base of the eye, the latter being partially imbedded in sockets in the brain-box. The visceral (parie- tosplanchnic) ganglion lies beneath and a little behind the brain, supplying the nerves for the ears (otocysts), which are enclosed in the cartilaginous brain-box, and there is a fine canal leading from the ears to the surface of the body, so that, as Gegenbaur states, it is possible to distinguish a mem- branous and a cartilaginous labyrinth, analogous to the similar parts found in the Vertebrates. The pedal ganglion (Fig. 208, p) is paired with the visceral ganglion (Fig. 208, r), but lies in front of it, behind and under the bulbous pha- rynx, and from it arise ten nerves (¢), which are distributed one to each arm, passing between the two rows of suckers. Two smaller ganglia, the superior buccal and inferior buccal, lie one above and one below the beginning of the cwsophagus. 258 ZOOLOGY. Besides this set of five cephalic ganglia, there are three pairs of ganglia belonging to the visceral or sympathetic nerve, which arise from the visceral ganglion situated among the viscera ; a single one (the ventricular or splanchnic ganglion) is situated over the stomach near the origin of the aorta, which sends a nerve to the cecum, and another accompanies the aorta; the mate to this ganglion is situated near the vena cava. A pair of ganglia is situated on the mantle walls (ganglia stellata), and there are two branchial ganglia. The kidneys (£) are irregular branching spongy bodies, in intimate con- nection with the auricles or branchial hearts. The sexes are distinct. The ovary (0) is large, especially when the eggs are ripe, and is situated in the end of the body-carvity. The single oviduct is as in some worms, separate from the ovary, and in this respect the Cephalopods approach or anticipate the Vertebrates, in which the oviduct is also separate from the ovary. The oviduct (ov) is a thick straight tube, with a flaring, deeply-lobed mouth. The eggs,when ex- truded, are enveloped in a large gelatinous capsule (Fig. 211), which is secreted by the large flattened nidamental gland (c) on the floor of the body-cavity, tied down at each end by cord-like membranes. Usually there ener esieeue are two nidamental glands. maleate, The earliest phase of development of the egg of most Cephalopods (Sepia, Loligo) is like that of birds and reptiles, the yolk undergoing partial segmentation, the blasto- derm being restricted to a small disk, asin Vertebrates. Even- tually the blastoderm encloses the whole yolk, the mantle begins to form, the eves are at first in-pushings of the outer germ-layer, and the mouth appears. The digestive tract originates from a primitive invagination of the outer germ- layer (ectoderm), as in .1mphiowus, Ascidians, worms, and some Ceelenterates. About the tenth day, as observed by Ussow, at Naples, the gills, siphon or funnel, and arms arise, DEVELOPMENT OF CU. TTLE-FISHES. 259 and a day later the rudiments of the ears, of the pharynx and salivary glands; while a day or two after, the ventri- cle, auricles, the kidneys, the ink-sac, and liver develop. Contrary to the usual rule the ganglia arise from the middle instead of the outer germ-layer. After this the germ grad- ually develops until it rises above the surface ‘or the egg, and soon the yolk is partly absorbed and is contained in a Fig. 212. Fie, 213. Fig. 212,—Embryo of Loligo Pealii. a, a’’,a'”,a’’”’, the right arms belonging to four pairs; c, the side of the head; e, the eye; /, the caudal fins; h, the heart; m, the mantle in which the color-vesicles are already developed and capable of chang- ing their colors; 0, the internal cavity of the ears; s, siphon.—After Verrill. Fig. 213.—The same as Fig. 212, but more advanced. The lettering in Figs. 212 and 213 the same.—Both after Verrill. large yoke sac, as in Figs, 212, 213. Finally the young cut- tle-fish hatches in the form indicated by Fig. 214, and then swims free upon the surface of the sea. The development of Cephalopods in general is, then, di- rect, ¢.e., there is no metamorphosis, the phases of meta- morphosis seen in most other mollusks not appearing; but in an unknown species of cuttle-fish whose eggs were found floating on the Atlantic, the germ, after the partial segmen- tation of the yoke, assumed a free-swimming condition (Fig. 115) before the definitive features (Fig. 116) of the cuttle-fish 260 ZOOLOGY, appeared. The squids or cuttle-fish are very active, some- times leaping out of the water and falling on the decks of large vessels. They dart rapidly back- om, ward by ejecting the water from their fn siphon or funnel. The Cephalopods are divided into two orders, according to the number of their gills. ; Order 1. Tetrabranchiata. — This group, in which the gills are four in | number, is represented by the Vautilus, the sole living representative of a num- ber of fossil forms, such as Orthoceruas, Goniatites and Ammonites. Nautilus pompilius Linn. (Fig. 217), and iVautilus umbilicatulus are the only survivors of about 1500 extinct od Fite ae” Species.of the order. Order 2. Dibranchiata. —The Di- branchiates are so called from possessing but two gills, while the Tetrabranchiates had, as in Vautilus, numerous unarmed tentacles ; these are now represented by ten (Decapoda). or are nt > Fig. 215. Fie. 216. Fig. 215.—Development of an unknown cuttle-fish. 7, cilia ; y, yolk; m#, man- tle beginning to develop. Fig. 216.—The same, much farther advanced. a, a’, a”, arms; m, mouth: dr. br, mills; 7, funnel; A, ear; g, optic ganglion ; mt, mantle, the dotted line ending ina chromatophore.—After Grenacher. eight (Octopoda) arms, provided with numerous suckers. To the ten-armed forms belong Spiruda, adiminutive cuttle, with BELEMNITES. 261 an internal coiled shell. The shells of Spirula Peronit La- marck are rarely thrown ashore on Nantucket ; it lives upon Fig. 247.--Pearly Nautilus, WY. pompilius. Seen in section showing pi chambers und siphuncle. Half natural size—From Tenney’s Zo- ology. the high seas. The extinct Belemnites had, like the recent Moroteuthis Verrill, a straight conical shell, the ‘‘ thunder- Fig. —Poulpe or Common Octopus of Brazilian Coast. bolt” fossil. Allied to Loligo and Ommastrephes, are gigan- tic cuttle-fishes which live in mid-ocean, but whose remains 262 ZOOLOGY. have been found at sea, or cast ashore at Newfoundland and the Danish coast; or their jaws occur in the stomach of sperm whales, as squid of all sizes form a large proportion of the food of sperm whales, dolphins, porpoises, and other Cetaceans provided with teeth. The largest cuttle-fish known is Architeuthis princeps Verrill, the body of which must be about six and a half metres (nineteen feet) in length, and nearly two metres (five feet, nine inches) in circumference. The two longer arms are 9 metres long. Architeu- this monachus Steen- strup has a body about two metres (seven feet) long, and the two long- er arms seven metres (twenty-four feet) long. A still larger individual was esti- mated by Verrill to be in total length about See so fourteen metres (forty- lateral view, Gulf of Maneater Veil "@ four feet). It is some- times thrown ashore on the coast of Newfoundland and Labrador, and in one in- stance attacked two men in a boat. The Octopus (Fig. 218) and Argonauta represent the eight-armed forms. PAPER NAUTILUS. 263 Those weird, horrifying creatures, the Octopi, are very soft- bodied, and live on shore just below or at low-water mark, or in deeper water. They have no shell or pen. Octopus punc- tatus Gabb expands 44 metres (14 feet) from tip to tip of the outstretched arms. They are brought of this size into the markets of San Francisco, where they are eaten by Italians and Chinese. An Indian woman at Victoria, Vancouver Island, in 1877, was seized and drowned by an Octopus, prob- ably of this species, while bathing on the shore. Smaller spe- cies on coral reefs sometimes seize collectors or natives, and fastening t) them with their relentless suckered arms tire and frighten to death the hapless victim. Octopus Bairdit Verrill (Fig. 219) inhabits the Gulf of Maine at from fifty to one hundred fathoms. The Argonauta, or paper nautilus, has a beautiful, delicate shell. A. argo lives in the Mediterranean, and in deep water %0 to 100 miles off the coast of Southern New England. The animal lives in the shell, but is not permanently attached to it, the shell not being chambered, and holds on to the sides by the greatly expanded terminations of two of its arms, which secrete the shell. The males are very small, not more than five centimetres (one inch) in length. During the reproductive season the third left arm becomes larger and different in form from the others, and becoming encysted is finally detached from the body, and deposited by the male within the mantle-cavity of the female, where the eggs in a way unknown are fertilized by the spermatic bodies. The free arm was supposed originally to be a parasitic worm, and was described under the name of Hectocotylus. The living species of Cephalopods have a wide geographi- cal range, and a high antiquity, the earliest forms appearing in the Lower Silurian Period, while the type culminated in the Triassic,Jurassic and Cretaceous Periods, Cuass III.—CEPHALOPODA. Mollusks with the head-lobe divided into arms, usually provided with suckers » eyes more highly organized than in any other invertebrates ¢ 264 ZOOLOG Y. nervous ganglia much concentrated and protected by an imperfect carta. ginous capsule ; pharynz armed with two teeth like a parrot’s beak, be- sides an odontophore. Sexes distinct. Usually development is direct, with no metamorphosis ; segmentation of the yolk partial, and a primi tive streak is present as in birds and reptiles. Order 1. Tetrabranchiata.—With four gills. (Nautilus, living; Or- thoceras, Goniatites, Ammonites, extinct.) Order 2. Dibranchiata.—With two gills. (Spirula, Belemnites, ex- tinct, Sepia, Architeuthis, Loligo, Ommastrephes, Octopus Argonauta.) TABULAR VIEW OF THE CLASSES OF MOLLUSCA. Cephalopoda, Cephalophora, Lamellibranchiata. J Laboratory Work.—The cuttles are not easy to dissect. A horizon- tal section through the head will show the relations of the cartilaginous capsule to the brain, optic nerves and eyes. The nervous ganglia can only be traced after tedious dissection. To study the viscera freshly- killed specimens are quite essential. oan MoLuusea. CHAPTER VIL. BRANCH VII.—ARTHROPODA (CrusTACEANS AND INSECTS). General Characters of Arthropods.—To this group be- long those Articulates which have jointed appendages, 7. ¢., antennz, jaws, maxille (or accessory jaws), palpi, and legs arranged in pairs, the two halves of the body thus being more markedly symmetrical than in the lower animals. The skin is usually hardened by the deposition of salts, carbon- ate and phosphate of lime, and of a peculiar organic sub- stance, called chitine. The segments (somites or arthro- meres) composing the body are usually limited in num- ber—twenty in the Crustaceans and eighteen in the insects— while each arthromere is primarily divided into an upper {tergum), lower (sternum), and lateral portion (pleurum). These divisions, however, cannot be traced in the head either of Crustaceans or insects. Moreover the head is well marked, with one or two pairs of feelers or antenne, and from two to four pairs of biting mouth-parts or jaws, and two compound eyes ; besides the compound eyes there are simple eyes in the insects. The germ is three-layered, and there is usually a well-marked metamorphosis. The Arthropoda are nearest related to the worms, certain Annelides, with their soft-jointed appendages (tentacles as well as lateral cirri) and well-marked head anticipating or foreshadowing the Arthropods. On the other hand, certain low parasitic Arthropods, as Linguatula, have been mistaken for genuine parasitic worms. So close are the affinities of the Vermes and Arthropods that they were by Cuvier united as a Branch Articulata, and while the Annelides and Arthropods may have had a common parentage, the recent progress in our knowledge of the worms, has led naturalists to discard the 266 ZOOLOGY. Articulata of Cuvier as a heterogeneous assemblage of forms embracing at least three branches of the animal | king- dom, namely, the Vermes, _ Tunicata, and Arthropo- da. The Arthropoda are di- vided into six well-de- fined classes, t.¢., the Crustacea with two body- ~ f “ regions, the head-thorax Fig. 220.—Shrimp, Palemonetes cuigariz. and abdomen (Fig. 220), a, cephalo-thorax ; 6, abdomen, and breathing through the body-walls or by external gills; the Podostomata, which are marine and breathe by gills, while the remaining four classes breathe by internal air-tubes and live on land. These are the Malacopoda, Myriopoda, Arachnida, and Insecta. Crass L—Crustacea (Water-fleas, Shrimps, Lobsters, and Crabs). General Characters of Crustaceans.—The typical forms of this class are the craw-fish, lobster, and crab, which the student should carefully examine as standards of comparison, from which a general knowledge of the class, which varies greatly in form in the different orders, may be obtained. The following account of the lobster will serve quite as well for the craw-fish, which abounds in the rivers and streams of the Middle and Western States. The body of the lobster consists of segments (somites, arthromeres), which in the abdomen are seen to form a com- plete ring, bearing a pair of jointed appendages, which are inserted between the sternum and tergum, the pleurum not being well marked in the abdominal segments. The abdo- men consists of seven segments. One of these segments (Fig 221 D’) should be separated from the others by the stu- dent, in order to observe the mode of insertion of the legs. Each segment bears but a single pair of appendages, and it Fig. 221.—External anatomy of the lobster.—After Kingsley. 268 ZUOLOGY. 1s a general rule that in the Arthropods each segment bears but a single pair of appendages. The abdominal feet are called ‘‘swimmerets ;” they are narrow, slender, divided at the end into two or three lobes or portions, and are used for swimming, as well as in the female for carrying the eggs. The first pair are slender in the female (Fig. 221, B ? ) and not. divided, while in the male (Fig. 221, B¢@) they are much larger, and modified to serve as intromittent organs. The sixth segment (Fig. 221, () bears broad paddle-like append- ages, while the seventh segment, forming the end of the body and called the “telson,” bears no appendages. It rep- resents mostly the tergum of the segment. Turning now to the cephalo-thorax, we see that there are two pairs of an- tenne, the smaller pair the most anterior ; a pair of mandi- bles with a palpus, situated on each side of the mouth ; two pairs of maxille or accessory jaws, which are flat, di- vided into lobes, and of unequal size ; three pairs of foot-jaws (maxillipedes), which differ from the maxille in having gills like those on the five following pairs of legs. There are thus thirteen pairs of cephalo-thoracic appendages, indicating that there are thirteen corresponding segments; these, with the seven abdominal segments, indicate that there are twenty segments in a typical Crustacean. By some authors the eyes are regarded as homologues of the appendages, but in early life they are seen to be developed on the second antennual seg- ment, as they are in the lower Crustacea. They are simply modified epithelial cells of the body-walls, as in the eyes of the lower invertebrates. The ears are situated in the smaller antenne (Fig. 221, a’). In the second or larger antenne are situated the openings of the ducts (Fig. 221, h) leading from the ‘‘ green glands,” while the external openings of the ovi- ducts are situated, each on one of the third pair of thoracic feet. It is impossible, except by counting the appendages them- selves, to ascertain with certainty the number of segments in the cephalo-thorax, the dorsal portion of the segments be- ing more or less obsolete, but the carapace, or shield of the head-thorax, may be seen, after close examination, to rep- resent the second antennal and mandibular segments, ANATOMY OF THE LOBSTER 269 and is so developed as to cover the other cephalo-thoracic segments, thus exemplifying, in an interesting way, Audou- in’s law of the development of one segment or part of a segment at the expense of adjoining parts or segments; this law, so universal in the Arthropods, as well as throughout the animal kingdom, also applies to the appendages. The same parts are to be found in the crab, but in a modi- fied form, owing to the development or transfer of the weight of the organization headwards; in other words, the crab is more cephalized than the lobster; this is seen in the small abdomen folded under the large, broad cephalo-thorax, and in the greater concentration headwards of the nervous sys- tem of the crab. To study the internal structure of the lobster, the dorsal surface of the carapace and of each abdominal segment should be removed ; in so doing the hypodermis or soft inner layer of the integument is disclosed ; it is usually filled with red pigment cells. The dorsal vessel, or heart, lies under the hypodermis of the carapace, this being an irregular hexagonal mass surrounded by a thin membrane (pericar- dium) with six valvular openings for the ingress of the. venous blood. The colorless, corpusculated blood is pumped by the heart backwards and forwards through three anterior arteries, one median and two lateral, the median artery pass- ing towards the head over the large stomach, and the two lateral, or hepatic arteries, passing to the liver and stom- ach. From the posterior angle of the heart arise two arteries ; the upper, a large median artery (the superior ab- dominal). passes along the back to the end of the abdomen, sending off at intervals pairs of small arteries to the large masses of muscles filling the abdominal cavity ; the lower is the second or sternal artery, which connects with one extend- ing along the floor of the body near the thoracic ganglia of the nervous cord. The arteries become, at least in the liver, finely subdivided, forming a mass of capillaries. There are no veins such as are present in the Vertebrates, but a series of venous channels or sinuses, through which the blood re- turns to the heart. There is a large vein in the middle of the ventral side of the body. 270 ZOOLOGY. The blood is driven by the heart through the arteries, and a large part of it, forced into the capillaries, is collected by the ventral venous sinus, and thence passing through the gills, where it is oxygenated, returns to the heart. The gills are appendages of the three pairs of maxilli- pedes and the five pairs of feet, and are contained in a chamber formed by the carapace ; the sea-water passing into the cavity between the body and the free edge of the cara- pace is afterwards scooped out through a large opening or passage on each side of the head, by a membranous append- age of the leg, called the ‘‘ gill-paddle” (Scaphognathite). The digestive system consists of a mouth, opening between the mandibles, an @sophagus, a large, membranous stomach, with very large teeth for crushing the food within the large or cardiac portion, while the posterior or pyloric end forms a strainer through which the food presses into the long, straight intestine, which ends in the telson. The liver is very large, dark green, with two ducts emptying on each side into the junction of the stomach with the intestine. The nervous system consists of a brain situated directly under the base of the rostrum (supracesophageal ganglion), from which a pair of optic nerves go to the two eves, and a pair to each of the four antenne. The mouth-parts are supplied with nerves from the infracesophageal ganglion, which, with the rest of the nervous system, lies in a lower plane than the brain. There are behind these two ganglia eleven others; the cephalo-thoracic portion of the cord is protected above by a framework of solid processes, which forms, as it were, a ‘‘false-bottom” to the cephalo-thorax ; this has to be carefully removed before the nervous cord can be laid bare. A sympathetic nerve passes around each side of the wsophagus and distributes branches to the stomach. The nerves of special sense are the optic and anditory nerves. The eves are compound, namely, composed.of many simple eves, each consisting of a cornea and crystalline eone, connected behind with a long. slender connective rod, uniting the cone with a spindle-shaped body resting on or against an expansion of a fibre of the optic nerve, and is ensheathed by a retina or black pigment mass (Fig. 221 s) ANATOMY OF THE LOBSTER. Q71 Though as many images may be formed in each eye as there are distinct crystalline cones, yet, as in man with his two eyes, the effect upon the lobster’s mind is probably that of @ single image. The lobster’s ears are seated in the base of the smaller or ‘first antenne ; they may be detected by a clear, oval space on the upper side; on laying this open, a large capsule will be discovered ; inside of this capsule is a projecting ridge covered with fine hairs, each of which contains a minute branch of the auditory nerve. The sac is filled with water, in which are suspended grains of sand which find their way into the capsule. A wave of sound disturbs the grains of sand, the vibrations affect the sensitive hairs, and thus the impression of a sound is telegraphed along the main audi- tory nerve to the brain. Organs of touch are the fine hairs fringing the mouth- parts and legs. The seat of the sense of smell in the Crus- tacea is not yet known, but it must be well developed, as nearly all Crustacea are scavengers, living on decaying mat- ter. Crabs also have the power of finding their way back to their original habitat when carried off even for several miles. The two large so-called “‘ green glands” situated on each side within the head-thorax, and having an outlet at the base of each of the larger antenne, are probably renal in their functions, corresponding to the kidneys of the verte- brate animals. The shell glands are of the same nature. The ovaries and corresponding male glands, are volumi- nous organs, the testes being white, and the ovaries, when the lobster is about to spawn, being highly colored, usually pale green, and the ovarian eggs are quite distinct. The lobster spawns from March till November; the young are hatched with much of the form of the adult, not passing through a metamorphosis, as in most shrimps and crabs. They swim near the surface until about one inch long, when they re- main at or near the bottom. The lobster probably moults but once annually, during the warmer part of the year, after having nearly attained its maturity, and when about to moult, or cast its tegument, the carapace splits from its hind edge as far as the base of the 272 ZOOLUG Y. rostrum or beak, where it is too solid to separate. The lobster then draws its body out of the rent in the anterior part of the carapace. ‘The claw—at this time soft, fleshy, and very watery—is drawn out through the basal joint, without any split in the old crust. In moulting, the stomach, with the solid teeth in the cardiac portion, is cast off with the old in- tegument ; why the stomach can thus be rejected is explained by the fact that the mouth, esophagus, and stomach are con- tinuous in early embryonic life with the epithelium forming the outer germ-layer, the mouth and anterior part of the alimentary canal being the result of an invagination of the ectoderm. The old skin is originally loosened and pushed away from the hypodermis, or under-layer, by the growth of temporary stiff hairs, which disappear after the skin is cast ; the hairs, however, at least in the craw-fish, do not occur on the line of the facetted cornea, on the eye-staik, or on the inner Jamelle of the fold of the carapace over the gill- opening. The Crustacea first appeared, so far as the geological record shows, during the Cambrian period, as the remains of a Hy- menocaris occur in the Lingula flags with those of Trilobites. This is a Phyllocaridan, an order which characterizes the Paleozvic age. In the Cambrian period also flourished Ostracods, while barnacles date from the Upper Silurian period. The oldest Phyllopod Crustacean is an Estheria of the Devonian period, at which time also appeared the first shrimp. In the Carboniferous period appeared the Gam- psonychide, a family of Schizopod shrimps, representcd in the United States by Paleocaris typus; also a family of true shrimps, the 4nthracaride, represented by Anthrapalemon. During this period also lived the Syncarida, a group connect- ing the sessile-eyed and stalk-eyed Crustacea, 7.e.. the Iso- pods and Decapods. The Isopods appeared in the Devonian period, while the genuine crabs appeared in the Jurassic period. Order 1. Cirripedia.—The barnacles would, at a first glance, hardly be regarded as Crustacea at all, and were regarded as Mollusca, until, in 1936, ‘Thompson found that the young barnacle was like the larve of other low Crustacea (Copepoda). The barnacle is, 2s in the common sessile form ANATOMY OF THE BARNACLE. 273 (Fig. 222), a shell-like animal, the shell composed of several pieces, with a multivalve, conical movable lid, having an opening through which several pairs of long, many-joint- ed, hairy appendages are thrust, thus creating a current which sets in towards the mouth. The com- mon barnacle (Balanus balanoi- des Stimpson) abounds on every rocky shore from extreme high- water mark to deep water, and the student can, by putting a group of them in sea-water, ob- serve the opening and shutting : of the valves and the movements Fig. 922.—A barnacle. Balanus of the appendages or “cirri.” Ren DOSS The structure of the barnacle may best be observed in dissecting a goose barnacle (Lepas fascicularis Ellis and Solander, Fig. 223). This barnacle consists of a body (capit- ulwm) and leathery peduncle. There are six pairs of jointed feet, representing the feet of the Cyclops (Fig. 231). The mouth, with the upper lip mandibles (B, 1), and two pairs of maxille, will be found in the middle of the shell. A short cesophagus (according to J. 8. Kingsley, whose ac- count we are using) leads to a pouch-like stomach and tubular intestine. This form, like most barnacles, is hermaphroditic, the ovary (4, 0)lying at the bottom of the shell, or in the pedunculated forms in the base of the peduncle, while the male gland (¢) is either close to or some distance from the ovary. There is also at the base of the shell, or in the pe- duncle when developed, a cement-gland, the secretion of which is for the purpose of attaching the barnacle to some rock or weed. While the sexes are generally united in the same indi- vidual, in the genera dla (Fig. 224) and Scalpellum (Figs. 225, 226, besides the normal hermaphroditic form, there are females, and also males called ‘‘complementary males,” which are attached parasitically both to the females and the hermaphroditic forms, living just within the valves or fastened to the membranes of the body. These comple 274 ZOOLOGY. mental males are degraded, imperfect forms, with sometimes no mouth or digestive canal. The apparent design in nature of their different sexual forms is to effect cross fertilization. The eggs pass from the ovaries into the body-cavity, where OH Mi, Fig. 223,—Anatomy of Lepas fuscicularis, ™#°* repeated, a sign of inferiority. There is a pair of simple eyes consolidated into one as in Limnetis and Limnadia, or as in Apus, there is a pair of compound eyes, situated in the cara- pace, apparently on one of the antennal segments. In Bran- 2 chipus and Artemia the compound eyes are stalked, an antic- ipation of the stalked eye of the lobster, ete., but the eye, it should be noticed, is not developed from a separate segment, but from one of the two antennal segments. All the members of this order hatch in the Nauplius form, the three pairs of appendages of the larva, representing the two pairs of antenne and the mandibles of the adult. The spe- cies live in pools of fresh water liable to dry up in summer ; they lay eggs which drop to the bottom, and show great vi- tality, withstanding the heat and dryness after the water has evaporated ; the young hatching after the rains refill the pools or ditches. Fig. 239.—Limnadia Agassizii, enlarged. 282 ZOOLOGY. This suborder presents a beautiful series of increasingly complex forms, as we ascend from Limunetis to Branchipus. In Limnetis the bivalve shell encloses the ani- mal, and is the size of a small flattened pea. There are from ten to twelve feet - bearing segments. L. Gouldii Baird (Fig. 238) is very rare in Canada and New England. The shell of Limnadia is thin, oval, and there are from eighteen to twenty-six feet-bearing segments. L. (Eulimnadia) Agassizii Packard (Fig. 239) b eal inhabits small pools in Southern New En- SC gland. The shell of Zstheria (Fig. 241, E's- «Sil ve. theria Belfragei Packard) is sometimes mis- le of male Bsthe- taken for that of the fresh-water mollusks qe, 1, Gand Cyclas and Pisidium. The males of the fore- end of body. going genera hare the first pair of feet modi- fied to form large claspers (Fig. 240). In Apus the abdomen projects beyond the large carapace, and ends in two long many-jointed appendages. There are about sixty pairs of feet, each foot — divided into several leaf -like- lobes, wherein respiration is carried on. These Phyllopods usually swim upon their backs, as in the species of Bran- chipus. The females chiefly differ from the males in the presence of AD: trig 944,~Shel of Rhea orbicular egg-sac on the eleventh pair Bejrage, enlarged three of feet, the sac being a modification of re two of the lobes of the feet, and containing but a few eggs. pus equalis Packard (Fig. 242, Fig. 244 A, represents the larva of a European jus) inhabits pools in the western plains. Lepidurus differs from Apws in having the telson spoon-shaped instead of square. ZL. Couesti Packard (Fig. 243) occurs on the Rocky Mountain plateau in Utah and Montana. It is an interesting fact in zoo-geography that there are no species of Apus and Lepidurus east of the west- ern plains. tus has been found by Siebold to reproduce parthenogenetically. The various species of Branchipus and Artemia have no PHYLLOPOD CRUSTACEANS. 283 carapace, the mandibular segment being small and not over- lapping the segments behind it. The second antenn# are Fig. 243.—Lepidurus Couesii, side and dorsal view, natural 61Ze. Fig. 242.—Apus equailis, natural size. large and in the male adapted for clasping. In Thamnocephalus (Fig. 245, T. brachyurus Packard, from Kansas) there is a singular shrub- like projection of the front of the head, and the abdomen is spatulate or spoon-shaped at the end. Bran- chinectes Coloradensis Pack. (Fig. 246) is a Rocky Mountain form. _ Fig. 24—e, Larva of Apus can- ; 5 ‘i ; ormts. — After Zaddach. _ 8, The brine-shrimp, Artemia, lives Nauplius of Artemia salina of Eu: only in brine-vats or in the salt "?* lakes of the West and of Southern Europe. Artemia 9" G cilis Verrill (Fig. 247) has thus far only been found in tubs 284 ZOOLOGY. of concentrated salt water on railroad bridges in New En- gland. Artemia fertilis Verrill abounds in Great Salt Lake. wy alc : a ree) Fig. 245.—Thamnocephalus platyurus, male, natural size. side and front view. @, head of the female ; 4, end of the body of the female, showing the ovisac. They may often be seen swimming about in pairs, as in Fig. 248. This species has a Nauplius young like that of Fig. 246.—Branchinectes Coloradensis Pack. the brine-shrimp of Europe (Fig. 244 0). It is a signifi- cant fact, bearing on the question of the origin of species, that, according to Schmankiewitsch, Artemia may change its TETRADECAPODS. 285 form, the change being induced by the greater or less saltness of the water. Artemia produces young by budding (parthe- nogenesis) as well as from eggs. e a 6 A species observed near Odessa ; produced females alone in warm 7S weather; and only in water of Ge ee / medium strength were males, os produced. The eggs of Arte- OR g mia fertilis have been sent in moist mud from Utah to Mu- nich, Germany, and specimens raised from the eggs by Siebold, proving the great vitality of the eggs of these Phyllopods, a fact paralleled by the similar vitality of the eggs of the king-crab. Fig. 244 6 represents the Nau- , ae plius of the European brine- shrimp. Order 4.— Edriophthalma.— To this order belong the sow- bugs (Zsopoda) and the beach- fleas (Amphipoda). In these , Fig, 247.—Brine- shrimp, Artemia if gracilis, enlarged. 4, first antenna ; 0 Crustacea there is no cephalo- second antenna or clisper; ¢, stalked, thorax, but the head is small, ater verry ee) See bearing two pairs of antenne, and a pair of jaws, and three pairs of maxilla. The thorax is continuous with the abdo- men. Respiration is performed by lamellate or leaf-like gills on the middle feet in the Amphipods, or on the hinder = abdominal feet in = the Isopods. The lowest Isopods are “parasitic, they Fig. 248.—Artemia fertilis from Great Salt Lake. e, . ‘ipatnee ¢, male claspers. * graduate into the Amphipods, and the higher Amphipods are connected with the shrimps (De- capoda) through a group (probably a suborder) of synthetic forms (Paleocaris, Acanthotelson and Gampsonyz, Fig. 249) such as are found in the coal formation of Illinois 286 ZOOLOGY. and Europe, which we have called Syncarida, and which have antenne and tails like shrimps, but the body Fig. 249-—Gampsonyx fimbriatus of European coal measures, 244 times natural Bize. and limbs like Amphipods. In the Isopods the body is flat- tened and the head rather broad. Fig. 251 is a dorsal view of Serolis Gau- dichaudi Audouin and Edwards, with the two pairs of antenne and pointed sides of each thoracic segment, dissected to show the nervous system, the two pairs of antennal nerves ; the optic nerves (op) sent to the compound eyes. Fig. 252 represents a trans- verse section of the body, showing the mode of insertion of the legs, and the equality in the tergal and sternal sides of the body, Fig. 254 represents a gill. In the common pill-bug (Porcellio) aérial respiration is per- formed by respiratory cavities situated in the abdomen. In Ty/os similar cavities are filled with a multitude of branching ceca, serving for aérial respiration, thus antici- pating the tracheary system of insects. The nervous system is quite simple. (Fig. 250, Idotea, and Fig. 251, that of Serolis.) The digestive canai is straight, consisting Fig. 250.—Nervous of a short cesophagnus, a membranous stom- eecce Ween te. ach, and usvally a short tubular intestine ; ron the liver consisting of several short cceca. In Serolis Gaudichaudi the stomach is somewhat pear- EMBRYOLOGY OF ONISCUS. 287 shaped, widest behind, extending a little behind the middle of the body. The intestine is about one half as wide as the stomach. Certain Isopods possess segmental organs. Fig. 251.—Dissection of Serolis to show the nervous system.—Dissected and drawn by J. S. Kingsley. There is no cecal enlargement, and no “urinary” tubes. The sexes are distinct. ‘The young are hatched in the form of the adult, there being no metamorphosis. The development of the pill-bug, Oniscus murarius, is probably typical of that of most Tetradecapods and Deca- Fig. 252 —Transverse section of Serolis. ¢, t, tergum; 8, s, sternum; em, epime- ru es, episternum, at insertion of the legs.—Prepared and drawn by J. 8. Kings- ley. pods (Bobretzky). The first change after fertilization is the origin of the formative or primitive blastodermic cells at one 288 ZOOLOGY. pole of the egg. This single cell subdivides, its products forming the “‘blastodermic disk” or outer germ-layer, the segmentation of the yolk being partial. The third (innermost) and middle germ-layers next. arise (the same processes go on in certain shrimps, viz.: Crangon and Palemon). The intestine is formed by an in-pushing of the ae oN. COouter germ-layer. The limbs now bud out, the ae result of the pushing out of the outer germ- layer (ectoderm). The nervous cord arises from the ectoderm ; the large intestine originates in me the yolk-sac, its epithelium first s appearing in the liver-sac. The heart is the last to be formed. Ex- ternally the antenne in Oniscus Fis 953 — andalso 1s¢//us are the first to bud Mouth-parts of cut; the remaining appendages of Polis. m, an- dible ; mz’, first the head and thorax arise contem- maxilla; mz’, Fig. 34.—A second maxilla; poraneously, and subsequently the gill of Serolis — palpns. “Drawn abdominal feet. The abdomen in ley. «the Isopods is curved upwards and backwards, while in the embryo Amphipods it is bent be- neath the body. The development of the Amphipods or beach-fleas is nearly identical with that of the Isopods. The eggs of cer- tain species undergo total segmentation, while those of other species of the same genus (Gammarus) partially segment, as in the spiders, and in a less degree the insects, Standing next below Cymothoa, which is of the general. Isopod shape, but which lives parasitically on the tongue and other parts of fishes, but which from their parasitic habits become slightly changed in form, the females espe- cially, sometimes becoming blind, is the family of which Bopyrus is arepresentative. The females (Fig. 257) are par- asitic under the carapace of various shrimps. In B. palemon- eticola Packard, the females are many times larger than the males ; the ventral side of the body is partly aborted, having been absorbed by its pressure against the carapace of its host, which is swollen over it ; it retains its position by rawn by J. S. Kingsley. ISOPODA, 289 Fre. 257. Fig. 255.—Section of the embryo pill-bug. 4, intestine; 7, epithelium form- Ing the walls of the two lobes of the liver ; g, transverse section of the nervous cord ; h, walls of the body.—After Bobretzky. Fig, 256.—Section of more advanced embryo pill-bug. h, heart; ip: hypoeder- mal layer or body-walls ; m,mu-cular wall of the intestine: ¢, epithelial lining of the intestine; p, dividing cell-wall between the heart and intestine; 7, two lobes of the liver; g, ganglion. the clear space being filled with the fine granular substance of the ganglion.—After Bobretzky. Fiz. 257.—Bopyrus. A, ventral, B, dorsal side of the female; @, lateral and D, dorsal view of the male; c!, head and first thoracic segment ; ¢?, antenne--all en. larzed.— Packard, del. 290 ZIOLOGY. the sharp hook-like legs around the margin of the body. The head has no eyes nor appendages. The male (Fig. 257, C, D) is but slightly modified, is very minute, and is lodged partly out of sight under the ventral plates of the female, whose body is about five millimetres (a fifth of an inch) in length. aN Fig. 258.—Arcturus Bafini, with its young clinging to its antenne.—After Wyville- Thompson. Various species of Porcellio (sow-bugs) live under stones on land; and allied to -1sellus, the water sow-bug, is the marine Limnoria lignorum White, which is very injurious to the piles of bridges, wharves, and any submerged wood. The highest Isopods are Jdotea, of which J. irroratus Say (Fig. 250) is our most abundant species, being common in eel-grass, etc.. between and just below tide-marks ; and Are- turus (Fig. 258, 4. Baffin Sabine), from the Arctic seas. PHYLLOCARIDA. 291 The series of Amphipods begins with Cyamus ceti (Linn.), the whale-louse, passes into Caprella, with its linear body and spider-like legs, to Hyperia, which lives as a mess-mate of the jelly-fish, Cyanea, and culminates in the water-flea (Gammarus ornatus Edwards) and sand-flea (Orchestia agilis Smith), abundant and leaping in all directions from under dried sea-weed at high-water mark. Fig. 259 represents Gammarus robustus Smith, a fresh- water form common in the western territories. Fig. 259.—Gammarus robustus Smith, Utah, Enlarged.—After Smith. Order 5. Phyllocarrda.—This name is proposed for a group of Crustacea, the forerunner of the Decapoda and hitherto regarded as simply a family (Nedaliade@), in which there is an interesting combination of Copepod, Phyllopod, and Decapod characters, with others quite peculiar to them- selves. The type is an instance of a generalized one, and is very ancient, having been ushered in during the earliest Si- lurian period, when there were (for Crustacea) gigantic forms (Dithyrocaris was over one foot in length) compared with those living at the present day. The order connects the Decapods with the Phyllopods and lower orders. The mod- ern Nebalia is small, about a centimetre (.40-.50 inch) in length, with the body compressed, four of the abdominal segments projecting beyond the carapace, the last abdominal segment bearing two large spines. There is a large rostrum overhanging the head ; stalked eyes, and two pairs of anten- ne, the second pair nearly as long as the body and many- jointed. The mandibles are succeeded by two pairs of max- 292 ZOOLOGY. ille. Behind these mouth-parts are eight pairs of short, leaf- like respiratory feet, which do not project beyond the edge of the carapace. These are succeeded by four pairs of large, long swimming feet, and there are two additional pairs of small abdominal feet. There is no metamorphosis, develop- ment being direct, the young hatching in the form of the adult. Of the fossil forms, Hymenocaris was regarded by Salter as the more generalized type. The genera Peltocaris and Discinocaris characterize the Lower Silurian period ; Ceratiocaris the upper ; Dictyocaris the Upper Silurian and Lowest Devonian strata ; Dithyrocaris and Argus the Car- boniferous period. Our northeastern and arctic species is Nebalia bipes (Fabricius), which occurs from Maine to Green- Jand. Order 6. Thoracostraca.—In the Stomapods, represented by Sguilla, the gills are attached to the base of the hinder ab- dominal feet. Sgwilla lives in holes below low-water mark. The snborder Decapoda (Shrimps, Lobster).— A general knowledge of the Crustacea representing this, the high- est group of the class, may be obtained by a study of the craw-fish and lobster. All Decapods have twenty seg- ments in the body, a carapace covering the thorax and con- cealing the gills, which are highly specialized and attached to the maxillipedes and to the legs; usually a pair of stalked eyes, two unequal pairs of antenne, the hinder pair the larger and longer ; a pair of mandibles, often provided with a palpus, two pairs of lobed maxille, three pairs of maxilli- pedes, while the name of the order is derived from the fact that there are five pairs of well-marked legs, or ten in all. To the abdomen are appended six pairs of swimming feet. called ‘‘swimmerets.” Another distinctive characteristic of most, in fact all the higher Decapods, is the short, or five or six-sided heart. The early phases of embryological development in the De- capods are much asin the Ldriophithalma. Most Decapods leave the egg in a larval state called the Zoéa. In the shrimps, Lucifer and Peneus, the young is a Nauplius, like a voung Entomostracan, having but three pairs of feet, and asingle eye. The Zoéa has no thoracic feet, and usually at first DECAPODA. 293 no abdominal feet ; the compound eyes are large and usually sessile, and the carapace is often armed with a long dorsal and frontal spine. Fig. 260 represents the Zoéa, or larva of the common shore crab (Cancer irroratus Say). After sev- Fig, 260.—Zoéa of the common Crab. Cancer. Much enlarged.—After Smith. eral moults, the thoracic legs appear, the mouth - parts change from swimming -legs to appendages fitted for pre- paring the food to be swallowed and digested. This stage in the short-tailed Decapods or crabs, is called the Mega- lops stage (Fig. 261); certain immature crabs having been mistaken for and described as mature Crustacea, under the name Megalops. After swimming about the surface in the Zoéa and Megalops conditions, the body becomes more bulky, more concentrated headwards, and the crab descends to the bottom and hides under stones, etc. The development of the individual crab is, in a general gense, an epitome of the development of the order. In the lowest genera, as in Cuma and Mysis, the form is some- what like an advanced Zoéa, while the remarkable concentra- tion of the parts headwards, seen in the crabs, is a great 294 ZOOLOGY. step upwards. Dana’s law of cephalization, or transfer of parts headwards, is more strikingly manifested in the Crus- tacea than in any other animals. Nearly all Decapods undergo this decided metamorphosis ; in only a few forms, such as the craw-fish, lobster, and a few shrimps and crabs, do the young leave the egg in the general form of the adult, the Zoéa stage being rap- idly assumed and dis- carded during em- \ bryonic life. Most Crustacea bear their eggs about with them ; in only a few cases, as the Syuilla and the land-crab of the West Indies, are the eggs left by the parent in holes or on the sea-shore. Thoracostraca in- clude Stomapods, the Schizopoda, rep- resented by Mysis ; the Cumacea, repre- sented by Cuma ; the long-tailed Decapods, Fig, 261.—Megalops of the Crab.—After Smith, Such as the shrimps and lobster, called Aacrura, and the genuine short-tailed Decapoda, or Bra- chyura. Most of the species of the crabs are confined to tropical seas and live in shallow water. The Decapods appeared in the Coal Period, and were rep- resented by somewhat generalized forms, such as 4Anthra- palemon (Fig. 262) from the coal measures of Illinois. Recently a genuine shrimp (Palgopalemon) has been de- scribed by Whitfield from the Upper Devonian formation of Ohio. Crustacea, especially shrimps and crabs, are sensitive to FOSSIL CRABS. 295 shocks and sounds. When alarmed, lobsters are said to cast off their large claws, but the latter are again re- newed. It is more probable, however, that the claws are torn off during their contests with each other. Hensen found that crabs and shrimps liy- ing in water do not notice sounds made in the air. The hairs about the mouth are the organs of tac- tile sense, and have been made by Hensen to vibrate to certain sounds. The eyes may be greatly devel- oped in shrimps living at great depths ; thus Thalascaris, a shrimp living near the bottom of the At- lantic Ocean, is remarkable for the large size of its eyes. In the spe- cies of Alpheus, which live in holes in sponges, etc., the eyes are small. ma The eyes of the blind Willemesia, Fig. 262. Anthrapalemon gracilis. dredged at great depths by the ; : “‘Challenger” Expedition, are rudimentary, though in the young the eyes are better developed. This is the case with the young of the blind craw-fish Cambarus pellucidus (Tell- kampf, Fig, 263) of Mammoth and other caves. The fact that the eyes in the young are larger than in the adult indi- cates that this species has descended from other forms living in neighboring streams, and well endowed with the sense of sight. The eye (Fig. 264) of the blind craw-fish differs from that of the normal species in its smaller size, conical form, the absence of a cornea (indicated by the dotted lines in A), the pigment cells being white instead of black, and by differences in the form of the brain, that of the blind species being fuller on the sides. Crabs breathe by gills, but the palm crab breathes by lungs. Crass IJ.—PopostomaTa. Podostomata.—This class is proposed for the king-- crab (Limulus). the only survivor of a large number of fossil JAerostomata, which dominated the Silurian seas. 2u6 ZOOLOGY. It comprises the order of MJerostomata represented at the present day by the king-crab, and the order Trilobita, which is wholly extinct. The organization of the king-crab is so CY Fig. 263.—Cambarus pellucidus, the blind craw-fish of Mammoth Cave. Natura Size. wholly unlike that of the Crustacea, when we consider the want of antenne, the fact that the nervous system is PODOSTOMATA. 297 peculiar in form and also ensheathed by arteries, and the peculiar nature of the gills of the abdominal feet, as well as the highly developed system of blood-vessels; that we are obliged to place it with the Trilobites in a division by itself. Fig. 264. a Brain and eye of a normal Cambarus from Iowa. The same of the blind craw-fish from Mammoth Cave. é Cornea.—Packard, del. Recent researches also on its development prove that the Podostomata should form a distinct class of Arthropods, equivalent on the one hand to the Crustacea and on the other to the Arachnida, but from the fact that they breathe like most Crustacea by external gills, we prefer to retain them in a position between the Crustacea and Arachnida. Order 1. Merostomata.—The only living representative of this order is the king-crab, belonging to the genus Limulus, represented in American waters by Limulus Polyphemus Linn., which ranges from Casco Bay, Maine, to Florida and the West Indies. The body of the king-crab is very large, sometimes nearly two feet in length ; it consists of a cephalo-thorax composed of six segments and an abdomen with nine segments, the ninth (telson) forming a long spine. The cephalo-thorax is broader than long, in shape somewhat like that of Apus, with a broad flat triangular fold on the under side. Above are two large lunate compound eyes, near the middle of the head, but quite remote from each other, and two small sim- ple eyes situated close together near the front edge of the head. There are no antenne, and the six pairs of append- 298 ZOOLOGY. ages are of uniform shape like legs, not like mandibles or maxille, and are adapted for walking; the feet are pro- vided with sharp teeth on the basal joint for retaining the food. The mouth is situated between the second pair: the first pair of legs are smaller than the others. All end in two simple claws, except the sixth pair, which are armed with several spatulate appendages serving to prop the crea- ture as it burrows into the mud. The males differ from the females in the hand and opposing thumb of the second pair of feet. These cephalo-thoracic appendages are quite as dif- ferent from those of most Crustacea as those of the mites and spiders, which have a pair of mandibles and maxille, the latter provided with a palpus. Appended to the ab- domen are six pairs of broad swimming feet, all except the first pair of which bear on the under side two sets of about one hundred respiratory leaves or plates, into which the blood is sent from the heart, passing around the outer edge and returning around the inner edge. This mode of respiration is like that of the Isopods. The alimentary canal consists of an csophagnus, which rises directly over the mouth, a stomach lined with rows of large chitinous teeth, with a large conical, stopper-like valve projecting into the posterior end of the body ; the intestine is straight, ending in the base of the abdominal spine. The liver is very voluminous, ramifying throughout the cephalo- thorax. The nervous system is quite unlike that of the Crustacea ; the brain is situated on the floor of the body in the same plane as the rest of the svstem, and sends a pair of nerves to the compound cre. a single nerve supplying the ocelli.* The feet are all suppliel with nerve: from a thick ring surrounding the «@sophagus. The nerves to the six pairs of abdominal legs are sent otf from the ventral cord. * The nervous system of Limulus is quite unlike that of the Scorpion, where the brain is situated in the upper part of the head and supplies the maxille with nerves, and is situated directly over the infracso- phageal ganglion; and, besides, there is no wsophageal ring as in Limulus, only the two commissures connecting the brain with the infraesophageal ganglion as usual in the Crustacea and Arachnida ir general. ANATOMY OF THE KING-CRAB. 299 The heart is tubular, with eight pairs of valvular openings for the return of the venous blood which flows into the pericardial sac from all parts of the body ; the arterial blood Fig. 265.—Nervous and part of thecirculatory system of Limulus polyphemus, the King-Crab. a, vent ; @, esophagus ; 2, brain; 0, nerve to the smaller eyes; 0’, nerve to the larger eyes ; s, nerve-ring around the esophagus. All the nerves are surround- ed by an arterial coat.—After Milne Edwards. is sent out from the arteries branching from the front end of the heart flowing around the upper side of the edge of the cephalo-thorax through numerous minute vessels. Also there are a pair of branchial arteries, and two arteries in the base of the spine. 300 ZOOLOGY. The arrangement of the ventral system of arteries 13 very peculiar and quite characteristic of this animal. The cso- phageal nervous ring, and in fact the entire nervous cord, is ensheathed in a vascular coat, so that the nervous system and its branches are bathed by arterial blood. ‘The veins are better developed than usual; there being in the cephalo- thorax two large collective veins along each side of the in- testine. Closely connected with the two large collective veins are two large brick-red glandular bodies each with four branches extending up into the dorsal side of the cephalo-thorax. They are probably renal in their nature. Both the ovaries and testes are voluminous glands, each opening by two papille on the under side of the first ab- dominal feet. At the time of spawning the ovary is greatly distended, the branches filled with green eggs. Unlike most Crustacea, the female king-crab buries her eggs in the sand between tide-marks, and there leaves them at the mercy of the waves, until the young hatch. The eggs are laid in the Northern States between the end of May and cho Fie. 266. Fie. 267. ; ne oo eee sua 3 @m, serous membrane ; ch, chorion. early in July, and the young are from a month to six week: in hatching. After fertilization the volk undergoes total segmentation, much as in spiders and the craw-fish. When the primitive disk is formed the outer layer of blastodermic cells peels off soon after the limbs begin to appear, and this constitutes EMBRYOLOGY OF THE KING-CRAB. 301 the serous membrane (Fig. 206, am), which is like that of insects. Then the limbs bud out; the six pairs of cephalic limbs appear at once as in Fig. 266. Soon after the two basal pairs of abdominal leaf-iike feet arise, the abdomen be- comes separated from the front region of the body, and the segments are indicated as in Fig, 267% A later stage (Fig. 268) is signalized by the more highly developed dorsal portion of the embryo, an increase in size of the abdomen, and the appearance of nine distinct abdominalsegments. The segments of the cephalo-thorax are now very clearly defined, as also the division between the cephalo-thorax and abdomen, the latter being now nearly as broad as the cephalo-thorax, the sides of which are not spread out as in a later stage. ae (268.—King-erab shortly before hatching ; trilobitic stage, enlarged ; side and At this stage the egg-shell has split asunder and dropped off, while the serous membrane, acting as a vicarious egg- shell, has increased in size to an unusual extent, several times exceeding its original dimensions and filled with sea- water, in which the embryo can freely move. Ata little later period the embryo throws off an embry- onal skin (amnion), the thin pellicle floating about in the egg. Still later in the life of the embryo the claws are de- veloped, an additional rudimentary gill appears, and the abdomen grows broader and larger, with the segments more 302 ZOOLOGY. distinct ; the heart also appears, being a pale streak along the middle of the back extending from the front edge or the head to the base of the abdomen. Just before hatching the head-region spreads out, the ab- domen being a little more than half as wide as the cephalo- thorax. The two compound eyes and the pair of ocelli on the front edge of the head are quite distinct ; the append- ages to the gills appear on the two anterior pairs, and the legs are longer. The resemblance to a Trilobite is most remarkable, as seen in Fig. 268, It now also closely resembles the fossil king-crabs of the Carboniferous formation (Fig. 269, Prest- wichia rotundatus, Fig. 270, Belinurus lacoe?). Fig. 269.—Prestw‘chia. natural size.— After Worthen. q Fig. 270.—Belinurus lacoei. In about six weeks from the time the eggs are laid the embryo hatches. It now differs chiefly from the previous stage in the abdomen being much larger, scarcely less in size than the cephalo-thorax ; in the obliteration of the seg- ments, except where they are faintly indicated on the car- diac region of the abdomen, while the gills are much larger than before. The abdominal spine is very rudimentary ; it’ forms the ninth abdominal segment. The reader may now compare with our figures of the re- RELATIONSHIP OF LIMULUS TO TRILOBITES. 303 vently hatched Limulus (Fig. 271), that of Barrande’s larva of Trinucleus ornatus (Fig. 272, natural size and enlarged). He will see at a glance that the young Trilobite, born with- out any true thoracic segments, and with the head articu- lated with the abdomen, closely resembles the young Limu- lus. In Limulus no new segments are added after birth ; in the Trilobites the numerous thoracic segments are add- ed during successive moults. ‘The Trilobites thus pass through a well-marked metamorphosis, though by no mrans so remarkable as that of the Decapods and the Phyllopods. Fig. 272,—Larva of a Trilo- bite, Trinucleus ornatus.— After Barrande. ‘Fig. 271.—Larva of the King-crab. The young king-crabs swim briskly up and down, skim- ming about on their backs like Phyllopods, by flapping their gills, not bending their bodies. In asucceeding moult, which occurs between three and four weeks after hatching, the abdomen becomes smaller in proportion to the head, and the abdominal spine is about three times as long as broad. At this and also in the second, or succeeding moult, which oc- ‘curs about four weeks after the first moult, the young king- crab doubles in size. It is probable that specimens an inch long are about a year old, and it must require several years for them to attain a length of one foot. The Limuli of the Solenhofen slates (Jurassic) scarcely differed in appearanee from those of their living descend- ants. Limulus, Prestwichia, Bellinurus, and Euproéps form 304 ZOOLOGY. the representatives of the suborder -Yiphosura. The second suborder Eurypterida is represented by extinct genera Ptery- gotus, Eurypterus and allies which appeared in the upper Silurian Period and became extinct in the Coal Period. In these forms the cephalothorax is small, flattened and nearly square, while the abdomen is long, with twelve or thirteen segments, the last one forming a spoon-shaped or acute spine. The appendages of the cephalothorax were adapted for walking, one pair sometimes large and chelate; the hinder pair paddle-like. The gills were arranged like the teeth ina rake, the flat faces being fore and aft. While the king-crab burrows in the mud and lives on sea-worms, the Eurypterida probably swam near the surface, and were more predatory than the king-crabs. The -Verostomata are a gen- eralized type, with some resemblances to the trachnida as well as to the genuine Crustacea, resembling the former in the want of antenne, and their mode of development. Order 2. Trilobita.—The members of this group are all extinct. The body has a thick dense integument like that of Limulus, and is often variously ornamented with tuber- cles and spines. The body is divided into three longi- tudinal lobes, the central situated over the region of the heart as in Limulus. The body is more specialized than in the Verostomata, being divided into a true head consisting of six segments bearing jointed appendages, somewhat like those of the Merostomata, with from two to twenty-six dis- tinct thoracic segments (probably bearing short jointed limbs not extending beyond the edge of the body, which support- ed swimming and respiratory lobes). The abdomen consisted of several (greatest number twenty-eight) coalesced segments, forming a solid portion (pygidiwm), sometimes ending in a. spine, and probably bearing membranous swimming feet. The larval trilobite was like that of a king-crab, and after a number of moults acquired its thoracic segments, there being a well-marked metamorphosis. The Trilobites (Paradozrides, Agnostus, etc.) appeared in the lowest Silurian strata. cul- minated in the upper Silurian, and died out at the close of the Coal Period. CLASSIFICATION OF CRUSTACEA, 805 Cuass. I. CRUSTACEA, Arthropoda breathing by gills situated on the legs, or respiring through the body-walls. Body in the higher forms divided into two regions, a cephalo-thoraz and abdomen. Two pairs of antenne ; mandibles usu- ally with a palpus. Heart nearly square, or in the lower forms tubular. Often a distinct metamorphosis. Sexes distinct, eacept in a few cases (certain burnacles, etc.). Order 1. Cirripedia.—Sessile often retrograded ; antenne not devele oped, living parasitically, the appendages of the head some-~ times forming net-like organs. Young hatched in the nau- plius state. Suborder 1.—Rhizocephala (Sacculina, Pelto- gaster). Suborder 2.—Genuine Cirripedia (Balanus, Lepas.) Order 2. Entomostraca.—A cephalo-thorax developed ; mandibles and three pairs of maxille ; five pairs of thoracic feet, no ab- dominal feet ; without any gills. The parasitic forms more or less modified in shape, with sucking mouth-parts; all the young of the nauplius form. Suborder 1. Copepoda (Cyclops). Suborder 2. Stphonostoma (Lernea, Caligus, and Argulus). Order 3. Branchiopoda. Thoracic feet leaf-like ; one to three pairs of maxilla ; number of body-segments varying from a few to sixty ; cephalo-thorax often well developed, and forming a bivalved shell. Young usually a Nauplius. Suborder 1, Ostracoda (Cypris). Suborder 2. Cladocera (Daphnia). Sub- order 3. Phyllopoda (Limnadia, Apus, Branchipus, and Ar- temia.) Order 4, Edriopthalma.—No cephalothorax, thoracic segments dis- tint; respiration often carried on by the abdominal feet, Suborder 1. Jsopoda (Idotza, Asellus). Suborder 2. Am- phipoda (Gammarus). Order 5. Phyllocarida.—Body compressed ; rostrum distinct from the carapace ; thoracic feet leaf-like ; no metamorphosis. (Ne- balia.) Order ae Thoracostraca.—Cephalothorax well marked, abdomen often bent beneath the cephalothorax; breathing by gills attached to the maxillipedes and legs. Heart often nearly pentagonal. Usually a well-marked metamorphosis; young called a Zoéa. Suborder 1. Cumacea (Cuma). Suborder 2. Synearidu (Acanthotelson). Suborder 3. Sfomapoda (Squilla). Sub- order 4, Schizopoda (Mysis). Suborder 5. Decapoda (Cran- gon, Astacus, Homarus, Cancer). 206 ZOOLOGY. Crass I.—PODOSTOMATA. Appendages of the cephalothoraz in the form of legs, spiny at the base ; no antenne ; brain supplying nerves to the eyes alone; nerves to the cephalothoracie appendages sent off from an w@sophageal ring ; nervous system ensheathed by a ventral system of arteries ; metamorphosis slight. Seres distinct, Order 1. Merostomata.—No distinct thoracic segments and appendages. (Limulus, Eurypterus.) Order 2, Trilobita.—Numerous free thoracic segments and jointed ap- pendages. (Agnostus, Paradoxides, Calymene, Trinucleus, Asaphus; all extinct.) CLASSIFICATION OF THE ORDERS OF CRUSTACEA AND PODOSTOMATA. 8 5 > & § < = = 2 S z = gS 3 8 = € = = Ss 3S = = = g 3 8 a be = 5 — = = Is == = > L 2 s 8 pM ~ = = ° * and ~ = oS =e 8 3 gL S 3 =a s = I = 3S = $s 8 = 8 S | | s = CRUSTACEA. PoposTOMATA. Laboratory Work.—In dissecting the lobster, the shell or crust may be removed by a stout knife ; the whole dorsal portion of the cephal»- thorax and each segment behind, including the base of the telson, should be removed, care being taken not to injure the brain, which lies just under the base of the rostrum. The hypodermis, or reddish, mem- branous, inner layer of the integument, should then be dissected awa7, exposing the heart, the stomach, the liver, and the large muscles of the abdomen. The arterial system can be injected with carmine GENERAL CHARACTERS OF INSECTS. 307 through the heart, and the finer arteries traced into the large claws and legs. In the crab, the entire upper side of the carapace may be removed by the point of a knife. The smaller Crustacea, especially the water-fleas, may be examined alive under the microscope as trans- parent objects. In the larger forms the stomach may be laid open by the scissors in order to study its complicated structure. The eyes of the lobster should be hardened in alcohol and fine sections made for the microscope. This isan operation requiring much care and expc- rience. Experts in embryology have sliced the eggs of certain Crusta- cea and studied their embryology with great success. Tue AIR-BREATHING ARTHROPODA (Centipedes, Spiders. Insects). General Characters of Insects.—While in the worms there is no grouping of the segments into regions, we have seen that in most Crustacea there are two assemblages of segments—4. ¢., a head-thorax andabdomen. In the insects there is astep higher in the scale of life, a head is separated from the rest of the body, which is divided into three regions, the head, thorax, and hind-body (abdomen). More- over, the insects differ from the Crustacea in breathing by internal air-tubes which open through breathing-holes (spiracles) in the sides of the body. The six-footed insects also have wings, and their-presence is correlated with a differentiation or subdivision of the two hinder segments of the thorax into numerous pieces. The number of body-segments in winged insects is seven- teen or eighteen—/. ¢., four in the head, three in the thorax, and ten or eleven in the hind-body. In spiders and mites there are usually but two segments in the head, four in the thorax, and a varying number (not more than twelve) in the abdomen ; in Myriopods the number of segments varies greatly—z. e., from ten to two hundred. The appendages of the body are jointed, and perform four different func- tions—i. e., the antennz are sensorial organs, the jaws and maxille are for seizing and chewing or sucking food; the 30S ZOOLOGY. thoracic appendages are for walking, and the spinnerets of the spider, as well as the sting or ovipositor of many insects, are subservient in part to the continuance of the species. Of the winged insects there are two types : first, those in which the jaws and maxille are free, adapted for biting, as in the locust or grasshopper, and, second, those in which the jaws and maxille are more or le:: modified to suck or lap up liquid food, as in the butterfly. bee. and bug. Nearly all insects undergo a nieramGr ois the young being called a larva (caterpillar, grub, maggot) ; the larva transforms into a pupa (chrvsalis), and the pupa into the adult (imago). In order to obtain a knowledge of the :tracture, external and internal. of insects. the student should make a careful study of the anatomy of a locust or ¢rasshopper with the aid of the following description ; and afterward rear from the ege a caterpillar and watch the different steps in its metamor- phosis into a pupa and adult. The knowledge thus acquired will be worth more to the student than a volume of descrip- tions. On making a superficial examination of the tocust ‘Calop- tenus fremur-rvhrum, or C. spretus), its body will be seen to consist of an external crust. or thick, hard integument, pro- tecting the soft part: or viscera within. Thi: antesument is at intervals segmented or jointed. the segments more or less like rings, which, in turn, are subdivided into pieces. These sezments are most simple and easily comprehended in the abdomen or hind-body, which is comp s:ed of ten of them. The body consists of seventeen of thes: segments, variously modified and more or les: imperfect and difficult to make out, especially at each extremity of the body— t.e..in the head and at the end of the abdomen. These seventeen segments, moreover, are grouped into three re- gions. four composing the head, three the thorax, and ten the hind-body, or abdomen. On examining the abdomen, it will be found that the rings are quite perfect, and that each segment may be divided into an upper ‘tergal , a lateral (pleural), and an under sternal) portion, or arc Fig. 273, 1). ANATOMY OF INSECTS. 309 These parts are respectively called tergite, pleurite, and sternite, while the upper region of the body is called the cao i (ES % 4 0 Tarsus\s, — Palpus : Tibia rial & WY ~y Upteranum. oy a Prothorax. ~ "Frockont v7 oe ge e Go Fig. 278,—External anatomy of Caloptenus spretus, the head and thorax dis- jointed. up, uropatagium; f, furcula; c, cercus —Drawn by J. S. Kingsley. tergum, the lateral the pleurum, and the ventral or under portion the sternum. 310 ZOOLOGY. As these parts are less complicated in the abdomen, we will first study this region of the body, and then examine the more complex thorax and bead. The abdomen is a little over half as long as the body, the tergum extending far. down on the side and merging into the pleurum without. any suture or seam. The pleurum is indicated by the row of spiracles, which will be noticed further on. The sternum forms the ventral side of the abdomen, and meets the pleu- rum on the side of the body. In the female (Fig. 273, B), the abdomen tapers some- what toward the end of the body, to which are appended. the two pairs of stout, hooked spines, forming the oviposi- tor (Fig. 273, B,r, 7’). The anus is situated above the upper and larger pair, and the external opening of the oviduct, which is situated between the smaller and lower pair of spines, and is bounded on the ventral side by a movable tri-- angular acute flap, the egg-guide (Fig. 273, B, eg, and Fig. 276), The thorax, as seen in Fig. 273, consists of three seg- ments, called the prothorax, mesothorax, and metathorax, or fore, middle, and hind thoracic rings. They each bear a. pair of legs, and the two hinder each a pair of wings. The upper portion (tergum) of the middle and hind segments, owing to the presence of wings and the necessity of freedom. of movement to the muscles of flight, are divided or differ- entiated into two pieces, the scutwm and scutellum* (Fig. 273), the former the larger, extending across the back, and the scutellum a smaller, central, shield-like piece. The protergum, or what is usually in the books called the pro- thorax, represents either the scutum or both scutum and scutellum, the two not being differentiated. The fore wings are long and narrow, and thicker than the hinder, which are broad, thin, and membranous, and most active in flight, being folded up like a fan when at rest and tucked away out of sight under the fore wings, which act as wing-covers. * There are in many insects, as in many Lepidoptera and Hymenop- tera and some Neuroptera, four tergal pieces—7. é., preescutum, scutum, scutellum, and postscutellum, the first aud fourth pieces being usually very small and often obsolete. 311 ANATOMY OF INSECTS, Fig. 274. 312 ZOOLOGY. Turning now to the side of the body under the insertion of the wing (Fig. 274), we see that the side of each of the middle and hind thoracic rings is composed of two pieces, the anterior, episternum, resting on the sternum, with the epimerum behind it; these pieces are vertically high and narrow, and to them the leg is inserted by three pieces, called respectively coxa, trochantine, and trochanter (see Fig. 274), the latter forming a true joint of the leg. The legs consist of five well-marked joints, the femur (thigh), ¢ibia (shank), and tarsus (foot), the latter consist- ing in the locust of three joints, the third bearing two large claws with a pad between them. The hind legs, especially the femur and tibia, are very large, adapted for hopping. The sternum is broad and large in the middle and hind thorax, but small and obscurely limited in the prothorax, with a large conical projection between the legs. The head is mainly in the adult locust composed of a sin- gle piece called the epicranium (Figs. 274 and 275, #), which carries the compound eyes, ocelli, or simple eyes (Fig. 275, e), and antenne. While there are in real- ity four primary segments in the head of all winged insects, correspondmmg to the four pairs of appendages in the head, the posterior three segments, after early em- bryonic life in the locust, become obsolete, and are mainly represented by their ap- pendages and by small portions to which the appendages are attached. The epicranium ; represents the antennal segment, and aoe ee mostly corresponds to the tergum of the seg- apretus, # epicran ment. The antenne, or feelers, are in- um; (C, clypeus; JZ, labrum; 0 0, ocelli; e, 7 eye: aantenna; ma, Serted in front of the eyes, and between mandible; ma,portion +, i i 7 mandible; mz,portion them is the anterior ocellus, or simple eye, by the labrum; p, while the two posterior ocelli are situated maxillary palpus; p’, e o Jabial palpus.—Kings- above the insertion of the antenne. In dey del. 5 3 ‘ é front of the epicranium is the clypeus (Fig. 275), a piece nearly twice as broad as long. To the clypeus is attached a loose flap, which covers the jaws when they are at rest. This is the upper lip or labrum (Fig. 275), MOUTH-PARTS OF INSECTS. 313 There are three pairs of mouth-appendages : first, the true jaws or mandibles (Fig. 273), which are single-jointed, and are broad, short, solid, with a toothed cutting and grinding edge, adapted for biting. The mandibles are situated on each side of the mouth-opening. Behind the mandibles are the maxille (Fig. 273), which are divided into three lobes, the inner armed with teeth or spines, the middle lobe unarmed and spatula-shaped, while the outer forms a five- jointed feeler called the maxillary palpus. The maxille are accessory jaws, and probably serve to hold and arrange the food to be ground by the true jaws. The floor of the mouth is formed by the labium (Figs. 273 and 274), which in real- ity is composed of the two second maxille, soldered together in the middle, the two halves being drawn separately in Fig. 273; to each half is appended a three-jointed palpus. Within the mouth, and situated upon the labium, is the tongue (lingua), which is a large, membranous, partly hol- low expansion of the base of the labium ; it is somewhat pyriform, slightly keeled above, and covered with fine, stiif liairs, which, when magnified, are seen to be long, rough, chitinous spines, with one or two slight points or tubercles on the side. These stiff hairs probably serve to retain the food in the mouth, and are, apparently, of the same struc- ture as the teeth in the crop. The base of the tongue is narrow, and extends back to near the pharynx (or entrance to the gullet), there being on the floor of the mouth, behind the tongue, two oblique slight ridges, covered with stiff, golden hairs, like those on the tongue. The internal anatomy may be studied by removing the dorsal wall of the body and also by hardening the insect several days in alcohol and cutting it in two longitudinally by a sharp scalpel. The esophagus (Fig. 276, @) is short and curved, contin- uous with the roof of the mouth. There are several longi- tudinal irregular folds on the inner surface. It terminates in the centre of the head, directly under the supra-cesopha- geal ganglion, the end being indicated by several small coni- cal valves closing the passage, thus preventing the regurgita- tion of the food. The two salivary glands consist each of a 314 ZOOLOGY. bunch of follicles, emptying by a common duct into the floor of the mouth. The cesophagus is succeeded by the crop (ingluvies). It dilates rapidly in the head, and again enlarges before pass- ing out of the head, and at the point of first expansion or enlargement there begins a circular or oblique series of folds, armed with a single or two alternating rows of simple spine- like teeth. Just after the crop leaves the head, the ruge or folds become longitudinal, the teeth arranged in rows, each row formed of groups of from three to six teeth, which point backward so as to push the food into the stomach. In alcoholic specimens the folds of the crop and cesophagus are deep blood-red, while the muscular portion is flesh-col- ored. It is in the crop that the “‘ molasses ’’ thrown out by the locust originates. The proventriculus is very small in the locust, easily over- looked in dissection, while in the green grasshoppers it is large and armed with sharp teeth. A transverse section of the crop of the cricket shows that there are six large irreg- ular teeth armed with spines and hairs (Fig. 277). It forms a neck or constriction between the crop and true stomach. It may be studied by laying the alimentary canal open with a pair of fine scissors, and is then seen to be armed with six flat folds, suddenly terminating posteriorly, where the true stomach (chyle-stomach, ventriculus) begins. The chyle-stomach is about one half as thick as the crop, when the latter is distended with food, and is of nearly the same diameter throughout, being much paler than the red- dish crop, and of a flesh-color. From the anterior end arise six large gastric ceca, which are dilatations of the true chyle-stomach, and probably serve to present a larger surface from which the chyle may escape into the body-cavity and mix with the blood, there being in insects no lacteal vessels or lymphatic system. The stomach ends at the posterior edge of the fourth ab- dominal segment in a slight constriction, at which point (pyloric end) the urinary tubes (vasa urinaria, Fig. 276, ur) arise. These are arranged in ten groups of about fifteen tubes, so that there are about one hundred and fifty long, fine tubes in all. 315 ANATOMY OF INSECTS. SS SSS Se Fig. 276.—Inte anatomy of Ciloptenus femur-rubrum, at, antenna and nerve leading to it from the “ brain” or supra-cesophageal ganglion (sp), oc, ocelli, ax nerves leading to them from the “ brain : @, esophugus ; m, mouth: 7b, labium or under lip ; 77, infra-ces: geal ganglion, sending three pairs of nerves tc the mandibles, maxille, and labinm Tespectively (not clearly shown in the engraving) ; sm. sympathetic or vagus nerve, starting from a ganglion restin, above the esophagus, and connecting with another ganglion (sg) near the hinder end of the crop; sad, salivary g'ands (the termination of the salivary duct not clearly shown Ws the engraver); nv, nervous cord and ganglia; ov, ovary; ur, urinary tubes (cut off, leaving the stumps): ovt, oviduct; sb, sebaceous gland; 6c, bursa co ulatrix; ovt/, site of opening of the oviduct (the left oviduct cut away); 1-10, abdominal segments, “the other organs labelled in full.—Drawn from his original dis- sections by Mr, Edward Burvesg, 316 ZOOLOGY. The intestine (ileum) liesin the fifth and sixth abdominal segments. Behind the intestine is the colon, which is smaller than the intestine proper, and makes a partial twist. The colon suddenly expands into the rectum, with six large rectal glands on the inside, held in place by six muscular bands attached anteriorly to the hinder end of the colon. The rectum turns up toward its end, and the vent is situated just below the supra-anal plate. Having described the digestive canal of the locust, we may state in a summary way the functions of the different divisions of the tract. The food after being cut up by the jaws is acted upon while in the crop by the salivary fluid, which is alkaline, and pos- sesses the property, as in ver- tebrates, of rapidly transform- ing the starchy elements of the food into soluble and as- similable glucose. The diges- tive action carried on in the crop (ingluvies) then, in a veg- etable-feeding insect like the Fig. 277.—Transverse ~ertion of the locust, results in the conver- migucaley allay 4: ROMY Tides Nel een sion of the starchy matters i ener into glucose or sugar. This process goes on very slowly. When digestion in the crop has ended, the matters submitted to an energetic pressure by the walls of the crop, which make peristaltic contrac- tions, filter gradually through the short, small proventricu- lus, directed by the furrows and chitinous project.ons lining it. The apparatus of teeth does not triturate the food, which has been sufficiently comminuted by the jaws. This is proved by the fact, says Plateau, that the parcels of food are of the same form and size as those in the crop, before passing through the proventriculus. The six large lateral pouches (ceca) emptying into the commencement of the stomach (ventriculus) are true glands, which secrete an al- DIGESTION IN INSECTS. 317 kaline fluid, probably aiding in digestion. In tne stomach (ventriculus) the portion of the food which has resisted the action of the crop is submitted to the action of a neutral or alkaline liquid, never acid, secreted by special local glands or by the lining epithelium. In the ileum and colon ac- tive absorption of the liquid portion of the food takes place, and the intestine proper (ileum and colon) is thus the seat of the secondary digestive phenomena. The reaction of the secretion is neutral or alkaline. The rectum is the ster- coral reservoir. It may be empty or full of liquids, but never contains any gas. The liquid products secreted by the urinary tubes are here accumulated, and in certain cir- cumstances here deposit the calenli or crystals of oxalic, uric, or phosphatic acid. Insects, says Plateau, have no special vessel to carry off the chyle, such as the lacteals or lymphatics of vertebrates ; the products of digestion—viz., salts in solution, peptones, sugar in solution, and emulsion- ized greasy matters—pass through the fine coatings of the digestive canal by osmosis, and mingle outside of this canal with the currents of blood which pass along the ventral and lateral parts of the body. Into the pyloric end of the stomach empty the urinary tubes, their secretions passing into theintestine. These are organs exclusively depuratory and urinary, relieving the body of the waste products. The liquid which they secrete contains urea (?), uric acid, and urates in abundance, hip- puric acid (?), chloride of sodium, phosphates, carbonate of lime, oxalate of lime in quantity, leucine, and coloring mat- ters. The nervous system of the locust, as of other insects, con- sists of a series of nerve-centres, or so-called brains (ganglia), which are connected by two cords (commissures), the two cords in certain parts of the body in some insects united into one. There are in the locust ten ganglia, two in the head, three in the thorax, and five in the abdomen. The first ganglion is rather larger than the others, and is called tne “‘brain.’”? The brain rests upon the oesophagus, whence its name, supra-cesophageal ganglion. From the brain arise the large, short, optic nerves (Fig. 276, not lettered, but repre- 318 ZOOLOGY. sented by the circle behind the brain, sp; Fig. 278, op), which go to the compound eyes, and from the front arise the three slender filaments which are sent to the three ocelli (Fig. 276, oc). From immediately in front, low down, arise NERVOUS SYSTEM OF INSECTS. 319 the antennal nerves (Fig. 276, af). The simple brain of the locust may be compared with the more complicated brain of an ant, as seen in Fig. 279. The infra-csophageal ganglion (Fig. 278, if), as its name implies, lies under the esophagus at the base of the head, un- Fig, 279.—Right half of an ant’s-brain: “@, infra-cesophageal ganglion ; Gr, brain; €, central connective portions ; W, semi-circular bodies of the small-celled portion of tue brain lyin+ next to the basal portion of the brain, from which the nerves to the simple eyes (au) arise; Au, optic lobes; An, antennal lobes (the bodies appearing like cells are rounded massvs of the network of the substance of the cord; 7, cellu- lar cortical substance of the brain; ko, twofold body of the commissure connecting the brain wih the iufra-cesophigeal ganglion.—After Leydig, from Graber. der abridge of chitine, and directly behind the tongue. It is connected with the supra-cesophageal ganglion by two com- missures passing up each side of the esophagus, From the ander side of the infra-esophageal ganglion arise three pairs of nerves, which are distributed to the mandibles. 320 ZOOLOGY. maxille,and labium. The mandibular nerves project for- ward and arise from the anterior part of the ganglion, near the origin of the supra-cesophageal commissures, while the maxillary and labial nerves are directed downward inte. those organs, The sympathetic ganglia are three in number ; one situ- ated just behind the supra-cesophageal ganglion (Fig. 273, as), resting on the ceesophagus, and two others situated each side of the crop, low down. Each of the two posterior ganglia is supplied by a nerve from the anterior ganglion. Two nerves pass under the crop con- necting the posterior ganglia, and from each posterior ganglion a nerve is sent backward to the end of the proventriculus. A pair of nerves pass under the cesophagus from each side of the anterior sympathetic ganglion, and another pair pass downward to a round white body, whose nature is unknown (Fig. 273, w). Fig. 280 represents an enlarged view of the brain and sympathetic nerve of amoth. The heart isa long tube lying in the abdomen, dilating Fig. 280.— Supra-cesopha- geal ganglion and visceral (or eympathetic) nervous system of the silk-worm moth (Bom- Zz mori). _gé, Supra-ceso- eal ganglion (“* brain **) ; @, antennary nerve; 0, optic nerve; 7, azygos trunk of the at six places along its course, and ending in a conical point near the end of the abdomen; it is held in visceral nervous system; 7, its roots oe prom. the supra-cesophag' nglion ; 8, nae nerve iit gangli- onic enlargements & s8°.— After Braudt, from Gegen- baur. place by fine muscular bands. All insects breathe by means of a complicated system of air-tubes rami- fying throughout the body, the air entering through a row of spiracles, or air-holes, or breath- ing-holes (stigmata), in the sides of the body. There are in locusts two pairs of thoracic and eight pairs of abdominal spiracles. The first thoracic pair (Fig. 281) is situated on the membrane connecting the prothorax and mesothorax, and is covered by the hinder edge of the protergum (usually called prothorax). The second spiracle is situated on the RESPIRATORY ORGANS OF INSECTS. 321 posterior edge of the mesothorax. There are eight abdominal spiracles, the first one situated just in front of the auditory sac or tympanum (see Fig. 274), and the remaining seven are small openings along the side of the abdomen, as indicated in Fig. 281. From these spiracles air-tubes pass in a short distance and connect on each side of the body with the spi- racular trachea (Fig. 281, 8, Fig. 282, s), as we may call it. The air-tubes consist of two coats, in the inner of which is developed the so-called spiral thread (tenidium). These spiracular trachese begin at the posterior spiracle, and extend forward into the mesothorax, there subdividing into several branches. Branches from them pass to the two main ven- tral trachee (Fig. 281, v), and to the two main dorsal tra- chee (Fig. 281, D, Fig. 282, D). The main tracheal sys- tem in the abdomen, then, consists of six tubes, three on a side, extending along the abdomen. ‘The pair of ventral tracheze extend along the under side of the digestive canal; the dorsal trachez rest on the digestive canal. These six tubes are connected by anastomosing traches, and, with their numerous subdivisions and minute twigs and the sys- tem of dilated trachez or air-sacs, an intricate network of trachez is formed. The system of thoracic air-tubes is quite independent of the abdominal system, and not so easy to make out. The tubes arising from the two thoracic stigmata are not very well marked; they, however, send two well-marked traches into the head (Fig. 281, ¢, Fig. 282, c), which subdivide into the ocular dilated air-tube (Fig. 281, oc, Fig. 282, oc) and a number of air-sacs in the front of the head. The series of large abdominal air-sacs, of which there are five pairs (Fig. 282, 3-7), arise independently of the main trachexw directly from branches originating from the spira- cles, as seen in Fig. 281. They are large and easily found by raising the integument of the back. There is a large pair in the mesothorax (Fig. 282, 2) and two enormous sacs in the prothorax (Fig. 282, 1), sometimes extending as far back as the anterior edge of the mesothorax. All these sacs are superficial, lying next to the hypodermis or inner layer of the integument, while the smaller ones are, in many cases, ZOOLOGY. 322 RESPIRATION IN INSECTS. 323 buried among the muscles. Besides the ordinary air-sacs, there is in the end of the abdomen, behind the ovaries, a plexus of six dilated air-sacs (Fig. 282, I, II, III), which are long, spindle-shaped, and are easily detected in dis- secting. There is a system of dilated trachee and about fifty air- sacs in the head. In the legs two trachee pass down each side of the femora, sending off at quite regular intervals numerous much-branch- ing, transverse twigs; there is one large and a very small trachea in the tibia, and the main one extends to the ex- tremity of the last tarsal joint. By holding the red-legged locust in the hand, one may observe the mode of breathing. During this act the por- tion of the side of the body between the spiracle and the pleurum (Fig. 273, A) contracts and expands ; the contrac- tion of this region causes the spiracles to open. The gen- eral movement is caused by the sternal moving much more decidedly than the tergal portion of the abdomen. When the pleural portion of the abdomen is forced out, the soft pleural membranous region under the fore and hind wings contracts, as does the tympanum and the membranous por- tions at the base of the hind legs. When the tergum or dorsal portion of the abdomen falls and the pleurum con- tracts, the spiracles open ; their opening is nearly but not always exactly co-ordinated with the contractions of the pleurum, but as a rule they are. There were sixty-five con- tractions in a minute in a locust which had been held be- tween the fingers about ten minutes. It was noticed that when the abdomen expanded, the air-sacs in the first ab- Fig, 281.—Showing distribution of air-tubes (trechez) and air-sacs—side view of the body. v, main ventral trachea (only one of the two shown); 8, left stigmatal trachea, connecting by vertical branches with D, the left main dorsal trachea; c, left cephalic trachea ; 0c, ocular dilated trachea. From the first, second, third, and fourth spiracles arise the first four abdominal air-sacs, which are succeeded by the plexus of three pairs of dilated trachee, I, II, III, in Fig. 287. Numerous air-sacs and trachez are represented in the head and thorax. The two thoracic spiracles are rep- resented, but not lettered. . Fig. 282.—D, left dorsal trachea; 8S, left stigmatal trachea ; I, IT, III, first, second, and thira pairs of abdominal dilated trachee, forming a plexus behind the ovaries; 1, pair of enormous thoracic air-sacs; 2, pair of smaller air-sacs ; 3-7. abdominal gir-sacs; oc. ocular dilated trachea and air-sacs : c, cephalic trachea. The relations of the heart to tne dorsal trachee are indicated.—Drawn by Emerton from disser- tions by author. 324 ZOOLOGY. dominal ring contracted. The respiratory movements, as Plateau states, consist of the alternate contraction and re- covery of the figure of the abdomen in two dimensions, 7.¢., vertical and transverse. During expiration the abdomen contracts, while during inspiration it returns to its normal shape. (Miall and Denny’s ‘‘ The Cockroach.”’) It is evident that the enormous powers of flight possessed by the locust, especially its fac- ulty of sailing for many hours in the air, is due to the presence of these air-sacs, which float it up in the atmospheric sea. Other insects with a powerful flight, as the bees and flies. have well- developed air-sacs, but they are Jess numerous. It will be seen that, once having taken flight, the locust can buoy itself up in the air, con- me stantlv filling and refilling its internal buoys or | balloons without any muscular exertion, and \j Bind thus be borne along by favorable winds to its Fig, 263,— destination. It is evident that the process of Longitudinal respiration can be best carried on in clear, sunny trachea of Hy- weather, and that when the sun sets, or the drophiluspiceus 4 G < or water-beetle. weather 1s cloudy and damp, its powers of flight é€p. epithelium; s Sea cee cv, cuticula; 7, are lessened, owing to the diminished power of sPXfier Muact’ Tespiration. The finer structure of the trachea is seen in Fig. 283. It is difficult to explain many of the actions of insects, from the fact that it is hard for us to appreciate their men- tal powers, instincts, and general intelligence. That they have sufficient intellectual powers to enable them to main- tain their existence may be regarded as an axiom. But in- sects differ much in intelligence and also in the degree of perfection of the organs of sense. The intelligence of in- sects depends, of course, largely on the development of the organs of special sense. The sense of sight must be well developed in the locust, there being two large, well-developed compound eyes, and three simple ones (ocelli), sitaated between the former, sup- plied with nerves of special sense. Fig. 254 represents the eye of a moth greatly enlarged to show the finer structure. SENSES OF INSECTS. 325 The antenne are, in the locust, organs of smell. The palpi are probably only organs of touch. It has been shown by F. Will that wasps have the sense of taste, and that minute gustatory organs are placed near the mouth. These organs, in the shape either of pits or projecting bulbs, in connection with peculiar nerve-endings, are situated on the labium, paraglosse, and on the inner side of. the maxilla. Similar organs occur in ants. Fig. 284.—Longitudinal section of the facetted eye of asphinx: the eye-capsule or sclera facetted externally (f), and sieve-like within, shows the rod-like ending of the optic nerve-fibres ; k, layer of the crystalline lens; 7, iris-like-pigment zone; ch, ae composed of pigment cells ; sn, optic nerve ; ¢7, trachea lost in fine bundles of fibrille.—After Leydig, from Graber. The ears are well developed in the locust, and we know that the sense of hearing must be delicate, not only from the fact that a loud alarum with kettles and pans affects them, but the movements of persons walking through the grass invariably disturb them. Besides this, they produce a fid- dling or stridulating sound by rubbing their hind legs against their folded wing-covers, and this noise is a sexual 826 ZOOLOG ¥. sound, heard and appreciated by individuals of the other sex. Any insect which produces a sound must be supposed to have ears to hear the sound pro- x e duced by others of its species. " In the antenne, palpi, and abdominal appendages of dif- nute olfactory organs consisting donfaal append wesota ta chrysopuay, Of pits alone (Fig. 285), or of ee ae oS De perforated at the end, and pegs associated with the pits. The ears (or auditory sacs) of the locust are situated, one on each side, on the basal joint of the abdomen, just be- ferent insects are seated mi- Fig. 286.—Ear of a locust (Caloptenus italicus) seen from the inner side. T, tym. janum; TR, its border ; 0, u, two horn-like processes ; bi. pear-shaped vesicle ; Rn, auditory nerve ; ga, terminal ganglion; st, stigma ; mm, opening and m’ closing mus- cle of the same ; WY, tensor muscle of the tympanum-membrane.—After Graber. hind the first abdominal spiracle (Fig. 274). The ap- paratus consists of a tense membrane, the fymponum, sur- rounded by a horny ring (Fig 286). ‘* On the internal sur- ORGANS OF HEARING. B27 face of this membrane are two horny processes (ow), to which is attached an extremely delicate vesicle (02) filled with a transparent fluid, and representing a membranous labyrinth. This vesicle is in connection with an auditory nerve (n} Fig. 287.—A Carabus-beetle in the act_of walking or running. Three legs (Z1, FR, I’), are directed forward, while the others (#1, L?, #%), which are directed back- ward toward the tail, have ended their activity. @ 0, ¢ d, and e/ are curves describect by the end of the tibiee and passing back to the end of the body; bh, di, and g are edd described by the same legs during their passive change of position.—After raber. which arises from the third thoracic ganglion, forms a gan- glion (ga) upon the tympanum, and terminates in the im- mediate neighborhood of the labyrinth by a collection of 328 ZOOLOGY. cuneiform, staff-like bodies, with very finely-pointed ex- tremities (primitive nerve-fibres?), which are surrounded by loosely aggregated ganglionic globules.”” (Siebold’s Anatomy of the Invertebrates.) In walking, the locust, beetle, or, in fact, any insect, raises and puts down its six legs alternately, as may be seen by observing the movements of a beetle (Fig. 287). While the structure of the limb of a ver- tebrate and insect is not homol- ogous, yet the mechanism or functions of the parts are in the main the same, as indicated in Figs. 288 and 289. The footprints of insects are sometimes left in fine wet sand on the banks of streams or by the seaside. In Fig. 290 the black dots are made by the fore, the clear circle by the middle, and the black dashes by the hind legs (Graber). The wings are developed as folds of the integument, and strengthened by hollow rods called ‘‘ veins ;’’ their branches Fig, 288, Section of the fore leg of Called “‘ venures.’’? There are a Stag beetle, ~howing the muscles. 3. ; : : extensor, B, flexor of the leg: ex. IM the wings of most insects tne eae eM, i six main veins—i.e., the costal, siepepe, penor of the fomaro- abled the subcostal, median, subme- dian, internal, and anal. They are hollow and usually contain an air-tube, and a nerve often accompanies the trachea in the principal veins. The arterial blood from the heart (as seen in the cockroach by Moseley) flows directly into the costal, subcostal, median, and submedian veins ; here it is in part aérated, and returns to the heart from the hinder edge of the wings through the hinder smaller branches and the main trunks of the internal FLIGHT OF INSECTS. 329 and anal veins. So that the wings of insects act as lungs as well as organs of flight. For the latter purpose, the principal veins are situated near the front edge of the wing, Fig. 289.—Diagram of the kuee-joint of a vertebrate (A) and_an insect’s limb (B). a_upper, 6, lower shank, united at A by a capsular joint, at B by a folding joint ; d, extensor or lifting muscle ; d!, flexor or lowering muscle of the lower jo.nt. The dotted line indicates in A the contour of the leg. After Graber, called the costa, and thus the wing is strengthened when the most strain comes during the beating of the air in flight. The wing of an insect in making the strokes during flight describes a figure 8 in the air. A fly’s wing makes 330 revolutions in a second, executing therefore 660 simple oscillations. The sexes are always distinct in insects, the only known exception being certain very low aquatic Arthropods called Tardigrada, in which both sexual glands occur in the same individual. The testes of the common red- legged locust form a single.mass of tubular glands, resting in the upper side of the third, fourth, and fifth segments of the hind body. Figs. 291 and 292 represent this structure in other insects. The ovaries consist of two sets of about twenty long tubes, within which the eggs may be found in various stages of de- velopment. The eggs pass into two main tubes which unite to form the single oviduct which lies on the floor of the abdomen. Above the opening of the oviduct is the sebific + Fig. 290.—Foot- ‘tracks of Wecro- phorus vespillo. atural size.—Af- ter Graber. gland and its duct. This gland secretes a copious supply of a sticky fluid, which is, as in many other insects, poured 330 ZOOLOGY. out as the eggs pass out of the oviduct, thus surrounding them with a tough coat. The external parts consist of the ovipositor (Fig. 273, Be, and Fig. 276), which is formed of two pairs of spines (rhab- dites) adapted for boring into the earth ; and of the egg. guide (Figs. 273 and 276, eg), a triangular flap guarding the under side of the opening of the oviduct. SS SN Fig. 291.—Male sexual apparatus of a bark-beetle. eee coca) i oe sl, vas deterens ; ho, testis; 02, seminal vesicle; @g, of “Acheta campestris.—After ductus ejaculatorius.—After Graber. Gegenbaur. There is a remarkable uniformity in the mode of develop- ment of the winged insects. In general, after fertilization of the egg, a few cells appear at one end of the egg ; these multiply, forming a single layer around the egg, this layer constituting the blastoderm. This layer thickens on one side of the egg, forming a whitish patch called the primitive streak or band. The blastoderm molts, sloughing off an outer layer of cells, a new layer forming beneath ; the skin thus thrown off is called the serous membrane; the second germ-layer (ectoderm) then arises, and a second a ie of Sphinx Membrane (called amnion, but not inte oe” Siero iene homologous with that of vertebrates) Fe nna ely onter, peels off from the primitive band just as the appendages are budding out, so that the body and appendages of the embryo insect are en- cased in the amnion as the hand and fingers are encased by aglove. As seen in the accompanying Figs. 293-298, the DEVELOPMENT OF INSECTS. 331 appendages bud out from the under side of the primitive band, and antennae, jaws, legs, ovipositor (or sting), and the abdominal feet of caterpillars are at h first all alike. Soon the appendages Sak begin to assume the form seen in the larva, and just before the insect hatches the last steps in the elabora- “tien of the larval form are taken. As to the development of the in- ternal organs, the ner- vous system first origi- nates; the alimentary canal is next formed ; Fig. 294,—Embrvo of Sphinx : : much more advanced. fh, Veart; and at about this time g, ganglion; @, intestine; m, * a rodimenta y muscular bandsrun. the stigmata and air- hing to the heart ; s, stigma and G . . Deraniye ot a trachea ts dia tubes arise as Invagina- t rec Kousieveny, & 88°95 tions of the outer germ- layer. The development of the salivary glands precedes that of the uri- nary tubes, which, with the genital glands, are originally offshoots of the primitive digestive tract. Finally the heart is formed. When the insect hatches, it either cuts its way through the egg-shell by a temporary egg-cnt- ter, as in the flea, or the expansion of the head and thorax and the convulsive movements of the body, as in the grasshopper, burst the pig. 095, shell asunder. The serous membrane is left in Primitive the shell, but in the case of grasshoppers the roth, qintcgtis larva on hatching is still enveloped in the am- segments ‘in- dicated, and nion. This is soon cast as a thin pellicle. their rudimen- tary append- The principal change from the larval to the ages. ¢, upper : ec lip ; at, anten- adult locust or grasshopper is the acquisition of ne; ma, man- wings. In such insects, then, as the Orthoptera Pek a ee and Hemiptera, in which the adults differ from geen? axtt the newly hatched larva mainly in the posses- legs Ps sion of wings, metamorphosis is said to be in- complete. In the beetle, butterfly, or bee, the metamorphosis «s complete ; the caterpillar, for example, is a biting insect, 332 is voracious, and leads a different life from the quiescent, sleeping pupa or chrysalis, which takes no food; on the other hand, the imago or butterfly has mandibles, which are rudimentary, and incapable of biting, while the maxille, or “‘tongue,’’ which were rudimentary in the caterpillar, become now greatly developed; and the butterfly takes Fig. 296.—Embryo of a Water-beetle (Hydrophilus). E, egg ; K, head ; ol, upper lip: m, mouth ; @n, antenne ;_ k,. man- dibles; k, g, maxille: B, thorax ; ,, ba, 3, legs ; hy-Ayo, ten pairs of rudimentary abd - minal legs, of which all except 2, disappear before the insect hatches ; a, anus,—After Kowa- Jeysky. ig. 297. Profile view of embryo. ree lettering as in Fig. BM, nervous cord; 0G, brain; D. veers canal ; sch, the weso- Phagus ; St, stigmatai op nings of the tracheal system ; 2. heart.— After Blitschli. Fi Hon 296. liquid food and but little of it, while its surroundings and mode of life are entirely changed with its acquisition of wings. Thus the butterfly leads three different lives, differ- ing greatly in structure, externally and internally, at these three periods, and with different environments. METAMORPHOSIS OF INSECTS. 333 Most caterpillars moult four or five times; at each moult the outer layer of the skin is cast off, the new skin arising from the hypodermis, or inner layer of the in- tegument. The skin opens on the back behind the head, the caterpillar drawing itself out of the rent. In the change from the caterpillar to the chrysalis, there are re- markable transformations in the muscles, the nervous, digestive, and circulatory system, inducing a change of form, external and internal, characterizing the different stages in the metamorphosis. While the changes in form are comparatively sudden in flies and butterflies, the steps that lead to them are gradual. How gradual they are may be seen by a study of the metamorphosis of a bee. In the nest of the humble or honey bee, the young may be found in all stages, from the egg to the pupa gayly colored and ready to emerge from its celi. Jt is diffienlt to indicate where the chrysalis stage begins and the larva stage ends, yet the metamorphosis is more complete—namely, the adult bee is more unlike the larva, than in any other insect. Besides the normal mode of de- velopment, certain insects, as the _ Fig. 298.—Embryo of the Louse. 2 am, serousmembrane; db, amnion; plant-louse (Aphis), the bark-louse as, antenne ; vk forehead.—After (Coccus), the honey-bee, the Po- mika listes wasp, the currant saw-fly (Nematus), the gall-flies, and a few others, produce young from unfertilized eggs. Certain moths, as the silk-worm moth (Bombyx mort) and others, have been known to lay unfertilized eggs from which caterpillars have hatched. This anomalous mode of repro- duction is called parthenogenesis, and fundamentally is only a modification of the mode of producing young by budding which is universal in plants, and is not unusual, as we have 334 ZOOLOGY. seen. among the lower branches of the animal kingdom. The object or design in nature, at least in the case of the plant-lice and bark-lice, as well as the gall-flies, is the pro- duction of large numbers of individuals, by which the per- petuity of the species is maintained. Insects are both useful and injurious to vegetation. Were it not for certain bees and moths, orchids and many other plants would not be fertilized ; insects also assist in the cross-fertilization of plants. For full crops of many of our fruits and vegetables, we are largely indebted to bees. flies, moths, and beetles, which, conveying pollen from flower to flower, ensure the production of abundant seeds and fruits. Mankind, on the other hand, suffers enormous losses from the attacks of injurious insects. Within a period of four years, the Rocky Mountain locust, migrating castward, in- flicted a loss of $200,000,000 on the farmers of the West. In the year 1864, the losses occasioned by the chinch-bug in the corn and wheat crop of the valley of the Mississippi amounted to upward of $100,000,000. It is estimated that the average annual losses in the United States from insects are about $100,000,000. On the other hand. host: of ichneumon flies and Tachina flics reduce the numbers and prevent undue increase in the numbers of injurious insects. The number of species of insects in collections is about 200,000. Of these there are about 25,000 species of Hyine- noptera (bees, wasps, etc.); about 25,000 species of Leji- doplera (butterflies and moths); about 25,000 Diptera (two- winged flies), and 90,000 Coleoptera (beetles ; with about 400 species of Arachnida (spiders, etc.), and $00 species of VMyrivpoda (millepedes, centipedes, etc.) Insects are distributed all over the surface of the earth. Most of the species are confined to the warmer portions of the globe, becoming fewer in the number of species as we approach the North Polar regions. Many are inhabitants of fresh water; a very few inhabit the sea. Insects, except a Silurian Blattid, first appeared in the Devonian rocks; these were Veuroptera and Orthoptera, with representatives of other groups which seem generalized in their structure. But if highly developed flying insects. be- lonzing, at least the May fly, to existing families. appeared PERIPATUS. 335 in the Devonian period, it is reasonable to suppose that other insects, besides forms like cockroaches, must have inhabited the dry land of the Silurian period. While true scorpions have been found in the Upper Silu- tian rocks of Scotland, Sweden, and New York, the oldest insect-remains are the wing of Palewodlattina douvillei, an insect probably allied to the cockroach, and found in the Middle Silurian rocks of France. In the Devonian of St. Johns, N.B., have been discovered fragments of the wings either of a May-fly or dragon-fly, and five other species of doubtful position. In the Carboniferous formation insect-remains are more numerous; they belong to the Thysanura, Orthoptera, May- flies, dragon-flies, Hemiptera, with composite forms (uge- -reon) and genuine Newroptera, allied to Stalis and Corydalus. No insects with a complete metamorphosis (except the Neu- roptera) are yet known to have lived before the Mesozoic age. Crass I.—Matracopopa (Peripatus). Characters of Malacopoda.—T'his group is represented by a single animal, the strange Peripatus of tropical coun- tries, in which the body is cylindrical, the integument, an- tennz, and limbs soft, not chitinized, with the head not separate from the body, and bearing a pair of many-jointed extensible antenne, with two pairs of rudimentary jaws {mandibles and maxilla), and from fourteen to thirty-three purs of feet. There is a pair of nephridia to each segment. It differs from other Arthropods in the two widely separated minutely ganglionated nervous cords sent backward from the brain; also in the minute, numerous tracheal twigs arising from numerous minute oval openings (rudimentary spiracles) situated irregularly along the median line of the ventral surface of the body. The feet are soft, fleshy, and end in two claws. Peripatus is viviparous. According tu the description and figures of Mr. Moseley, the young develop much as in the chilopodous Myriopods (Geophilus), show- ing that Peripatus is nearer to the Myriopods than any other group. That it is a tracheate animal was also proved by Mr. Moseley; but owing to the nature of the nervous system, the minute trachee and their numerous irregular 336 ZOOLOGY. spiracular openings, with no chitinous edge, this form cannot be placed among the Myriopods. It is certainly not a worm, but, on the whole, connects the worms with the sucking Myriopods, and suggests that the insects may have descended from forms somewhat like Pertpatus. Peripatus tuliformis- inhabits the West Indies, and either P. Edwardsii Blanch- ard, or an undescribed species about four centimetres in length (with twenty-seven pairs of legs), inhabits the Isth- mus of Panama. ‘The name Jalacopoda was proposed by De Blainville, who suggested that Peripatus connected the: Alyriopods with the Annelids. Crass I].—Myriopopa (Centipedes, etc.). Characters of Myriopoda.—The centipedes and millepedes: are distinguished by their cylindrical body, the abdominal seg- ments being numerous and similar to the thoracic segments, all provided with a pair of feet. The head bears a pair of antenne, but the jaws are not homologous with those of in- sects. The internal organization is simple, like that of the larvee of insects. Some Seolopendre@ are suid to be viviparous. Order 1. Diplopoda.—To this group belong the mille- pedes, Ju/us, ete. (Figs. 299-302). The first maxille are absent. The segments ure round or flattened, and the feet. are inserted near together, the sternum being undeveloped. In some forms (Fig. 299, Scoterpes Coper Packard, from Mammoth Cave) the body is hairy. They are all harmless. The eggs are laid in large numbers an inch or two beneath the surface of the earth. They undergo total segmentation, and in afew days the larva (Fig. 300) hatches. At this time it bears a resemblance to a Podura, having but three pairs of fect, the third pair attached to the fourth thoracic seg- ment. After a series of moults, new segments and new feet appear, and thus these Myriopods undergo a distinct meta- morphosis. The specics feed on dead leaves and fruit. Order 2. Paurapodu.—Vhe two orders of Myriopods are connected by Pauropus, which by Lubbock is regarded as the type of a distinct order (Pauropoda). Our only species, Pauropus Lubbockii Pack. (Fig. 304), consists of six seg- ments besides the head, and the young Pauropus has but MYRIOPODS. Fig. 300.—Larva of Julus. a, third ab- dominal segment, with the new limbs just budding out; 5, new segments arising be- en the ae Fig. 209.—Scoter- and the last segment.— pes copei of Mam- After Newport. moth Cave. Fig. 302. —Polydesmus cavicola, from Utah, top and side view. a, antenna; 0, a segment and leg; c, dorsal view of two segments show- ; @, side view of two terminal ing ornamentation segments of the body—all magnified. 337 Vs y at => A ae SS ZS FS ASE a Fig. 301. I ae mus ery- thropygus --common Poly des- mus. Fig. 303. —Geophilus. Natural size. 338 ZOOLOGY. three pairs of feet, and in this and other respects resembles Podura. Asecond form, Hurypauropus, of Ryder, has six segments, with nine pairs of feet wholly concealed from above by the expanded seg- ments. The antenne end in a terminal globular hyaline body with a long pedicel, as in Pauropus, and the mouth-parts are as in that genus. Z. spinosus Ryder is reddish brown, and one mm. in length. Order 3. Chilopoda.—This group is rep- resented by the centipede and Lithobius, in which the body is flattened, the sternal region being well developed. In Geophilus ‘Fig. 303, (7. bipuncticeps Wood) and allies there are from thirty to two hundred seg- ments. Our most common form is Litho- bius Americanus Newport, found under logs, ete. The centipede \Srolopendra heros Girard) is very poisonous, the poison- bets Mach eo sac being lodged in the two large fangs or Jarged. Fig. 3 on; first pair of legs. In Cermatia the body is oer of feet and first’ short, with compound eyes and remarkably long slenderlegs. C. forceps Rafinesque, of the Middle and Southern States, is said to be poisonous; it preys upon spiders. Cuass II].—Aracuyipa (Spiders, ete.). Characters of Arachnida.—The bodies of spiders and scor- pions, etc., are divided into two regions. a head-thorax and abdomen, the head being closely united with the thorax. There are no antenne, only a pair of mandibles and a pair of maxille, with four pairs of legs. There are never any compound eves. The young are usually like the adult, except in the mites, in which there _ Fig. 305—Head of Pau is a slight metamorphosis. In all sect Sach enlarged Arachnida there is a liver, this organ not being present in the winged insects. PYCNOGONIDA. 339 The type of this class is the spider, which is character- ized by the pos- session of two or three pairs of spinnerets, which are jointed ap- pendages _ ho- mologous with the legs. Be- sides trachesx, spiders have a Fig. 366.—Anatomy of a spider, diagrammatic Jongitudinal so-called lung section through the body. au, simple eyes and nerves leading (Fi 306 L) to them from the brain (supra-cesophageal ganglion. 0G) ; &- , 3 Gn, mandibles ; 4d, palpus of maxilla /,; /g, first pair of legs, @ Om pose d of b,-bg, succeeding pairs; A, head ; Br, thorax ; a hind-body or abdomen; #2, heart or dorsal vessel; Z, lung in front of several leaves, the opening of the oviduct G; the spinning-glands (sp) con- . : nect with the spinnerets, sp W. The digestive tract is -haded, into which the and in the abdomen enveloped in the liver.—After Graber. . blood flows, and is thus aérated. In Lycosa the blood flows through the heart from the head backward. There is a great range of structure, from the lowest mites to the spiders, certain mites having no heart, no trachez, very rudimentary mouth-parts, and no brain, there being but a single ganglion in the abdomen. Order 1—The Pycnogonida are marine forms, without air- tubes, with four pairs of long legs, into which ccecal prolonga- tions of the stomach pass, as seen in Fig. 307. Order 2. Tardigrada.— The bear animalcules (Fig. 308) are related to the mites. In these Fig. 307.—Ammothoé pycnogo- . i : : noides a, stomach with cceca (b, singular beings the ovary and 6, b,d) extending into the legs.— testis exist in the same individual. **0™ Geeenbaur. Macrobiotus Americanus Pack. is common in sphagnum swamps. Like the Rotatoria, these low forms are capable of revivifying after being apparently dead and dried up. 340 ZOOLOGY. Order 3. Linguatulina.—This group comprises remark- able worm-like forms, which are parasites. The young are mite-like, the body spherical, with boring jaws, and two Fig. 308—Milnesium tardigradum, X Fig. 309.—Pentastoma teenioides. 120 times. J. mouth-parts; 6, alimentary Natural size-—From Verrill canal; ov, ovary.—After Doyere. Fig. 310.—Ixodes albipictustrom a partly domesticated moose. The tick natural size, gorged with blood, and its six-legged young, much enlarged. a, beak or man- dibles armed with teeth; b, maxilla, and c, maxillary palpus: d, a foot with sucker Fig. 311.—Ixodes bovis. Natural size and claws, enlarged. and enlarged. THE MITES. 341 ‘pairs of short-clawed feet. Pentastoma (Fig. 309) occurs in the lungs and liver of man, und in horses and sheep. Order 4. Acarina.—The mites are degenerate Arach- nida, the body being oval in form, the head usually small, more or less merged with the thorax, while the latter is not differentiated from the abdomen. There is a Fig. 312.—Sugar-mite. Much Fig. 313.—Carolina scorpion (Buthus enlarged. Carolinianus). Natural size. (and last) pair being added after a moult. A typical mite, though above the average size of the members of the group, is the tick (Fig. 310, Lvodes albi- pictus Pack). Closely allied to this is Ixodes bovis Riley, the cattle-tick (Fig. 311), which buries its head .in ‘the skin, anchoring itself firmly by means of the backward-pointing teeth of its jaws. Other examples of mites are the cheese and sugar mites (Fig. 312, Tyroglyphus sacchari). The lat- ter appear as white specks in sugar, and to them is due the disease known as grocers’ itch. Certain mites live ge Fa Piehrercanete under the epidermis of the leaves of — , trees, often forming galls. 342 ZOOLOGY. Order 5. Arthrogastra.—In this group belong scor- pions (Fig. 313), false scorpions (Fig. 314), the whip scor- pions, and the harvest-man (Phalangium). In all these forms the abdomen is plainly segmented, the segments not being visible in the mites or spiders. Usually the maxillary palpi are much enlarged, and end in claws. The scorpion is viviparous, the young being brought forth alive. The young scorpions cling to the back of the mother. The sting of the scorpion is lodged in the tail, which is perforated, and contains in the bulbous enlargement an active poison. Though producing sickness, pain, and swelling in the arm, the sting of the scorpion is seldom fatal. The little false-scorpions (Chelifer. Fig. 314) often occur in. books, under the bark of trees, and understones. The whip- scorpion is confined to warm countries. Thelyphonus gigan- teus Lucas occurs in New Mexico and Mexico. Its abdomen ends in a long lash-like appendage. Its bite is poisonous. The harvest-men, or daddy-long-legs, are common in dark. places about houses. They feed on plant-lice. Our common species is Phalangium dorsatum Say. Order 6. Araneiia.—The spiders are always recogniza~- ble by their spherical abdomen. attached bya slender pedicel to the head-thorax. They breathe, like the scorpions, both by lungs as well as by trachee, and the young resemble the parent in having four pairs of feet. The development of the spider has some peculiarities not found in the higher insects. The egg undergoes total seg- mentation. The germ is somewhat worm-like, as in Fig. 315, then, as in (’, the primitive band forms, with head and tail end much alike. Afterward (Fig. 316) the head ac- celerates in development, and the appendages begin to bud out, six pairs of abdominal limbs appearing and then totally disappearing, except the three pairs of spinnerets, as if the spiders were descended originally from some Mvriopod-like form. The mandibles are vertical. and end in hollow points, through which the poison exudes, the two poison-glands being situated in the head. The male spider is usually much smaller than the female ; the latter lay their exes in eo silken cocoons. The tarantula (Zycosa) usually lives in TRAP-DOOR SPIDERS. 343 holes in the ground, and sometimes conceals the opening by covering it with a few dead leaves. Our largest spider is Nephila plumipes of the Southern States. The common garden spider is Epeira vulgaris Hentz. It lives about B A ¢ Fig. 315.—Development of the Spider.—A, worm-like stage ; B, primitive band ; C, the same more advanced, with rudiments of limbs. houses and in gardens ; its geometrical web is very regular. The large trap-door spider (Mygale) has four lung-sacs in- stead of two, as in the other spiders, and only two pairs of spinnerets. Myyale Henzti Girard inhabits the Western plains and Utah ; Mygale avicularia Linn. of South America is known to seize small birds, and suck their blood. There are probably about six or eight hundred species of spiders in North America; their colors are often brilliant, and sometimes, from the harmony in their colora- tion with that of the flowers in which they hide, or the leaves on which they may rest, elude the _ : : . : 2 Fig. 816.—Embryo Spider, still grasp of insectivorous birds. more advanced. This and Fig. 315 In their instincts and reasoning **¢" “lsparéde. power, spiders are quite on a level with the insects, as proved by their nest- and web-constructing abilities. bt4 ZOOLOGY. Crass VI.—INSEcTA. General Character of Insects.—The triregional division of the body is better marked in the genuine winged insects than in the Myriopods and spiders. ‘They usually have com- pound as well as simple eyes; usually two pairs of wings; three pairs of thoracic legs; often a pair of jointed abdomi- nal appendages, besides an ovipositor or sting which mor- phologically represents three pairs of abdominal legs. Order 1. Thysanura.—The spring-tails (Poduwra) and bristle-tails (Zepisma) represent this group. They are wing- less, with some affinities to the Myriopods; and the typical form Campodea (Fig. 319) is regarded as the ancestral form of the six-footed insects, as it is a generalized type, and forms like it may have been the earliest insects to appear. In Podura, the spring-tail, and also in Smynthurus (Smynthurus quadrisignatus Pack., Fig. 317), the characteristic organ is a forked abdominal appendage or ‘‘spring,” held in place by a hook; when released the pihis pe! spring darts backward, sending the insect thurus, a spring- high in the air. ne ee eear Our commonest Poduran is Tomocerus plumbeus Linn. (Fig. 318), found all over the northern hemisphere, in North America and Europe. The snow-flea, Achorutes nivicola Fitch, is blue-black, and is often seen leaping about on the snow in forests. The Podurans belong to the suborder Collembola; the higher forms, which bear a greater resemblance to the larve of Neuropterous insects and to the young cockroach, are the Cinura. Scolopendreila, with its well-developed ab- ‘dominal legs, represents the suborder Symphyla. In the group Cinwra there is no spring, but the tail ends in two or three bristles; and in Machilis, the highest form, there are compound eyes. In all there are jointed abdominal appendages, which structures are unique among Hexapodous insects. Campodea staphylinus (Fig. 819) is a small white DERMAPTERA AND ORTHOPTERA. 3845 slender form, with long, many-jointed antenne, and two long, slender, jointed caudal ap- pendages. Cave. Order 2. : It lives. under stones, and C. Cooket lives in Mammoth Dermaptera. — The earwigs (Forficula) have a flat BO Fig. 318.—A Poduran (Tomocerus) and its scales. Much enlarged. body, ending in a forceps; while the <, fore-wings are small, the large hind- wings being folded under them. Order 3. Orthoptera.—The insects of this group, so called from the straight-edged fore-wings of the grass- hoppers, locusts, crickets, etc., are characterized by their net- veined wings and incomplete metamorphosis. Organs of hearing may be situated either on the fore-legs, as in the green grasshoppers, katydids, or at the base of the abdomen, as in the locusts. Most Orthoptera have a large ovi- positor, by which they burrow in the earth or into soft wood, and deposit their eggs singly or in masses. Mantis ~ . (Fig. 320) lays its eggs in a cocoon- like mass. | Fig, 819.—Campodea. a, mandibles; b, maxilla. Many Orthoptera, as the crickets, green grasshoppers, 346 ZOOLOGY. katydids, etc., aud iocusts, produce loud, shrill sounds, which are sexual calls. They stridulate in three ways—t.é., first, by rubbing the base of one wing-cover on the other (crickets and green grasshoppers); second, by rubbing the inner surface of the hind legs against the outer surface of the front wings (some locusts): third, by rubbing together the upper surface of the front edge of the hind wings and- Fig. 320.—An African Mantis, or soothsayer, with its egg-mass.—From Mon- teiro’s Angola. = the under surface of the wing-covers during flight (some locusts). Order 4. Platyptera.—This group comprises the bird- lice, Psocide, Perlide, and white ants (Zermitide). The body is flattened, the head horizontal. The pronotum is usually large, broad, and square. The bird-lice (Wallophaga) are more nearly related to the wingless Psocide, such as the death-tick (Atropos) than to the Hemiptera, among which they are usually placed, since their free jaws and mouth- parts generally are like those of the Psocide. ‘They prob WHITE ANTS. 847. ably form a suborder of Platyptera. In the larval and pupal Perla (Fig. 321), tufts of gills are situated on the under side of the prothorax, and in the adult winged Pteronarcys these gills are * retained. The white ants top the Platypterous series; they live in stumps and fallen trees, and in the tropics do much harm by undermining the sills of houses, and destroying furniture, books, ete. The colonies are very large and populous. In our Jermes flavipes there ure males and females, workers and soldiers; the workers being small, ant-like, with small round heads, while the soldiers have Fig. 321.—Perla, larva. Fig. 322.—Pupa of a Drag- Fig. 323.—Agrion, natural size, and a, its on-1 ae (Eschna). larval gill, much enlarged. large square heads, with long jaws; the pups are active. Fritz Miller found in Brazil that owe species of Termes was differentiated into six different kinds of individuals: viz., a set of winged and wingless females; winged and wingless males; workers and soldiers. A male always lives with a female, and a wingless male and female may, on the death of a winged normal male and female, replace them. He 348 ZOOLOGY. found a male (king) living with thirty-one complementat females. : Order 5. Odonata.—Here belong the dragon-flies, in which the prothorax is remarkably small, the thorax nota- ble for the great development of the side- -pieces, the dorsal - pieces being rudimentary. The wings of both pairs are large, of nearly equal size, and finely net-veined. The larve are all aquatic, some of them having gills (Fig. 323, a) at the end of the body. Order 6. Plectoptera.—The May-flies have rudimentary mouth-parts; while the hind-wings. are small, sometimes wanting, and the hind-body ends in three long filaments. The larve are aquatic and breathe by gills placed on the sides Fig. 824.—May-fly and larva, the latter enlarged. Fig. 325.—Thrips. Order %. Thysanoptera.—This group is represented by Thrips, and belongs nearer to the Hemiptera than any other order. The mouth-parts are united to form a short conical sucker. The mandibles are bristle-like, bulbous at the base, and situated inside of the maxillz, which are flat, triangular, with palpi shorter than those of the labium. The wings are narrow and ‘fringed, sometimes wanting; the pronotum is largé, and the two-jointed feet are swollen at the ends, being without claws. The metamorphosis is incomplete; the pupa is active, its limbs and wings encased by a membrane, and the antenne are turned back on the head. Order 8. Hemiptera.—Insects of this group are called IEMIPTERA. 349 bugs. They all have sucking mouth-parts, the mandibles and first maxille being bristle-like, and ensheathed by the labium or second maxille. Their metamor- phoses are incomplete, the larva being like the adult, except that the wings are absent. Many bugs secrete a disagreeable fluid from glands seated in the metathorax. The lice are low, wingless parasitic Hemiptera. The sguash-bug (Fig. 326, Corews tristis) and chinch-bug (Blissus leucopterus Uhler) are types of the order. Pir Paeerin he While most insects live but a year or two, or three at the most, the seventeen-year locust (Cicada sep- temdecim Linn., Fig. 327) lives over sixteen years as a larva, Fig. 827._Seventeen-year Locust. u, b, pupa; d, incisions for eggs.—After Riley. finishing its transformations on the seventeenth; there is also, according to Riley, a thirteen-year variety of this species. The froth insect (Ptyelus lineatus) abounds on grass in early summer. The cochineal insect (Coccus cacti) belongs to the Coccide, or bark-lice; the dried female is used as a dyestuff, and abounds in Central America. 350 ZOOLOGY. The plant-louse (Fig. 330, Aphis mali Fabr.) is provided with two tubes on the hind-body from which honey-dew drops, which attracts ants, wasps, ete. In summer the Fig. 328.—Cochineal in- sect, male: female natural size and enlarged. Fig. 329.—Apple Aphis. Natural size and enlarged. plant-lice reproduce asexually, and as there may be nine or ten generations, one virgin aphis may become the parent of millions of children and grandchildren. Order 9. Neuroptera.—We now come to insects with a complete metamorphosis. All the foregoing orders are tcc @ ametabolous, the species a u passing through an incom- wil plete metamorphosis, the Fig. 330. coe aud aroupeof axaiked AEVE resembling the adult. eggs. This order is now restricted to those net-veined insects with a complete metamorphosis, the mouth-parts free, adapted for biting, with the ligula entire and large, broad, flat, and rounded, while the pro- thorax is large, broad, and square. The gronp comprises the Sivlide (Corydalus) and the Hemerobiide (Chrysopa, Mantispa. Rhaphidiv. and Hemerobins). Order 10. Mecaptera.—The scorpion-flies are represented by a single family (Panorpide), with the typical genera Lanorpa and the wingless Boreus. They are net-veined insects, but differ from the europlera in the caterpillar- like larve and in the imagines having a minute rudimentary ligula, the head being elongatcd, with minute mandibles atthe end of the snout. The maxille are long, and connate with the labium. Order 11. Trichoptera.—The group of caddis-flies, whose MECAPTERA. 351 cylindrical larve are called case-worms, differ from the Neuroptera in features which ally them to the Lepidoptera. The mandibles are obsolete, but well developed in the larva Fig. 331.—Mantispa interrupta — Fig. 332.—Fresh- Fig. 332a.—Larva of the Say: and side view of the samme lyhatchedlarvaof same, but older, before the without wings. Natural size.— Mantispa styria- first moult. Enlarged.— Emerton del. ca. Enlarged. After Brauer. ee ely i ope at 4 4 Fig. 233.—Panorpa. Fig. 334.—Case-worm}; a, its case. and pupa; the maxille are connate with the labium, while the palpi of both pair are well developed. The general proportions of the head and body and of the legs are much as in the Tineid moths. 352 ZOOLOGY. Order 12. Coleoptera.—The beetles form a homogeneous: and easily circumscribed group, all having the fore-wings thickened, not used in flight, and forming sheaths (elytra Fig. 335 —Pine weevil. a, larva; 5, pupa. or wing-covers) for the hinder pair. The mouth-parts are free and adapted for biting. The metamorphosis is com- plete. The young or larve of beetles are called grubs. Examples of beetles and their transformations are the pine Fig. 336 —June Beetle and its transformations, 1, pupa; 2, larva.—After Riley. weevil (Fig. 335, Prssodes strobi Peck) and the June beetle (Fig. 336,.Lachnosterna fusca Frohl.). The oil beetle is. remarkable for passing through three larval stages (Fig. OIL BEETLE. 353 337, Meloé angusticollis Say), the first larva being minute and parasitic on bees, sucking their blood, while in the Fig. 337,—Oil Bectle. a, firstJarva; 5, second larva; ¢, third larva; d@, pupa. second and third stages it feeds on the pollen mass designed for the young bees. Fig. 338.— Stylops childreni, male, dorsal and side view. Much enlarged. The blister beetles (Lytta marginata) undergo a similar series of transformations called a hypermetamorphosis, 354 ZOOLOGY. The most aberrant of beetles is Stylops (Figs. 338 and 339, S. childreni Westwood), the male of which has minute fore Fig. 339.—Stylops childreni, female. Fig. 340.—Astraptor illuminator, larva. 2, parasitic in the abdomen of a bee; b, top view of the same. Mauch en- Jarged. pe Fig. 342.—The early stages of the common House-fly. A, dorsal and side view of the larva ; @, air-tubes; sp, spiracle. (€, the spiracle enlarged. , head of the same larva, enlarged ; 01, labrum (7); md, mandibles; ma, maxille; at, antenne. ZF, a terminal spiracle much enlarged. D, pupanum; sp, spirac.e, All the figures much enlarged. - wings. The female is wingless, grub-like, imperfectly de- veloped, and is viviparous, the young issuing from her body THE HOUSE-FLY. 355 in all directions. A few beetles are phosphorescent. Such are the fire-flies, the cucuyo of the West Indies, the glow- worm, and certain grubs, such as Astraptor illuminator (Fig. 340), IJelanactes, and the young of a snapping beetle. Fig. 343.—Bot-fly of the ox and its larva. Order 13. Siphonaptera.—The fleas (Fig. 341) are wing- less, with sucking mouth-parts; all the palpi four-jointed. Order 14, Diptera.—The common house fly (Fig. 342) is atype of this division, all the members of which have but two wings, while the tongue is especially developed for lap. ping up liquids. The common héuse- fly lives one day in the egg state, from five days to a week as a maggot, and from five to seven days in the pupa state. It breeds about stables. The Tachina-fly is beneficial to man, from its parasitism in the bodies of caterpillars and other injurious insects. The bot-fly (Fig. 343, Hypoderma : bovis DeGeer) is closcly allied to the #8 34—Sumphus politus house-fly, but the maggot is much larger. The larval bot-fly of the horse lives in the stomach, that of the sheep in the frontal sinus. The Syrphus flies (Fig. 344, Syrphus politus Say) mimic wasps ; they are most useful in devouring aphides, while in. 356 ZOOLOGY. 8 Fig. 341.—Mctamorphosis of Sarcopsylla penetrans, or jigger, which lives in the toe of the natives of tropical America, 1, egg; 2, embryo; 3,larva; 4, cocoon; 5, pupa: 6, fecundated female ; 7. the same on the third day from its entrance under the skin of its human host; 8, the same after several days’ residence in the skin of its host ; 9, fally grown female magnified four times ; 10, head of the rame still more enlarged ; 11, the female before it has entered the skin of it~ host ; 12, the mouth-parts, much out ed ; m, mandibles ; d, maxillary palpi; wu, under-lip or labium.— After Karsten and Guyon. THE UESSTAN-FLY. 357 the larva state. They may be recognized as greenish maggots living among groups of plant- lice. In the two-winged gall- flies (Fig. 345, Cecidomyia destructor Say, or Hes- sian-fly) the body is small and slender, with long antenne. The crane-flies (Tipula) are large flies, standing near the head of the order, and, like the gall-fly, the chry- salis has free append- ages, there being no puparium or pupa-case, as in the lower flies. Lastly, we have the mos- quito (Figs. 346 and 347), whose larva is aquatic, and breathes by a process on the end of the body, containing a trachea. Order 15. Lepidoptera. — The butterflies and moths form a well-defined group, and are known by their scaly bodies (Fig. 348), the spiral maxilla or tongue, rolled up between the two large labial palpi, and their usually broad wings. As the butterfly, the type of the order, has peen described at some Jength, we will only enumerate some of the Fig. 345.—Hessian-fly. a, larva; b, pupa; ce. incision in wheat stalk for larva. (Mag- nified).—After Fitch. Fig. 346.—A, larva; c, its respiratory tube, B, pupa; d, respiratory tube; a, two paddles at the end of the hoy. Fig. 347.—Head and mouth parts of mos- quito. e, eye; a, antenne; lbr, labrum; h, hypopharynx; m, mandibles; ma, maxille; mzp, maxillary palpus; Jb, labium; c, cly- peas. (Magnified.) 358 ZOOLOGY. typical forms. The lowest group are the plume-moths (Pterophorus), in which the wings are fissured. Above Fig. “38, —Showing mode of ar- rangement of the es on the wings of a Moth, Fig. 350.—Grain Moth, Tinea granella. a, larva; 6. pupa, nat. size and enlarged ¢, grain of wheat held together by a web.—After Cartis. Fig 351.—Army-worm Moth. a. male; 4, female; c,eye; d, male; e, portion @ female antenna. Much magnified.—After Riley. them stand the clothes and grain moths ‘Figs. 349 and 350), which are minnte moths with narrow wings. THE COTTON-WORM. 309 The larger moths are represented by the canker-worm, the grass army-worm (Fig. 351), and the cotton army-worm (Fig. 352), so destructive to vegetation; the silk- worm moth (Bombyx mori Linn.), of the Old World, and the American silk-worm (Telea Polyphemus Linn.). Certain species of the silk- worm family, called basket-worms (Giceticus), live in cases con- structed of short or long strips Fig. 352.—Egg, caterpillar, and moth (Fig. 353. Our native species ea argillacea, the Cotton Army- jg Thyridopteryx ephemercfor- mis Haworth. The hawk-moths (Sphinz) are distinguished by their large size and very long tongue. The butterflies differ from the moths in having knobbed anten- nz, while the chrysalides are often ornamented with golden or silvery spots. Order 16. Hymenoptera.—The bees stand at the head of the insect series in perfection and specialization of parts, especially the organs of the mouth, and from the fact that in the course of the metamorphosis from the larva to the pupa the first ab- dominal segments hecome transferred to the thorax—a striking instance of the principle of transfer of parts headward. In the large head, spheri- cal thorax, and short, conical abdo- men, the bees are opposed to the dragon-flies and other Neuroptera, in which the abdomen is long, the p¥ie., 353. Cases of African thorax composed of three homogene- ous segments, and the mouth-parts only adapted for biting. In the bee there is a marked differentiation of the parts of 360 ZOOLOGY. the first and second maxillz ; the tongue or fleshy prolonga- tion of the second maxille (Jabiwm, see Fig. 354, g) being very long and adapted for lapping up liquid food in the ‘bottom of flowers. The Hymenoptera are represented by the saw-flies, the gall-flies, the ichneumon-flies and the ants, the sand-wasps, mud-wasps (Fig. 363), paper-making wasps, and bees. The lowest family is the Uroceride, or horn-tails (Fig. 355, larva of Tremex columba Linn.), whose fleshy white Fig. 354.—Side view of the front part of the head of the Humble Bee. a, clypeus covered with hairs; 5, labrum; c, the fleshy epipharynx partially concealed by the base of the mandibles (d); é, lacinia or blade oe the maxillz, with their two-jointed palpi (/) at the base ; j, the labium to which is appended the ligula (¢g) ; below are the labial palpi; 2, the two basal joints ; %, compound eyes, Jarvee bore in trees. The adults are large, with a long, saw- like ovipositor. In the saw-flies (Tenthredinide, Fig. 356, the pear-slug, Selandria cerasi Peck) the larva strongly re- sembles a caterpillar, having eight pairs of abdominal feet. The gall-flies (Fig. 857, Cynips) are small Hymenoptera which lay eggs in the leaves or stems of the oak, etc., which, from the uritation set up by their presence, causes the de- formation termed a gall. HABITS OF ANTS. 361 The ichneumon-flies (Fig..358) are very numerous in spe- cies and individuals ; by their ovipositor, often very long, they pierce the bodies of caterpillars, inserting several or many eggs into them; the larve develop feeding only on the fatty tissues of their host, but this usually causes the death of the caterpillar before its transformation. Certain minute species, with veinless wings (Fig. 859, Platygaster), of the canker-worm eggs, are egg-parasites, ovipositing in ° the eggs of butterflies, dragon-flies, ete. Fig. 357,—Gall-fly of oak, / Fig. 358.—An Ichneumon-fly, Fig. 355. —Horn- we tail : larvaof 77e- meacolumta. Nat. g1Ze. H * Fig. 356.—Pear Slug, palatal i EOE pig stg parse of Canker 1 larged ; 8, the fly. worm, Highly magnified. The family of ants is remarkable for the differentiation of the species and the consequent complexity of the colony, the division of labor and the reasoning powers manifested by the workers and soldiers, which, with the males and females, constitute the ant-colony. Certain ants enslave other species ; have herds of cattle, the aphides; build complicated nests or formicaries (Fig. 361), tunnel broad rivers, lay up seeds for use in the winter- 362 ZOOLOGY. time, are patterns of industry, and exhibit a readiness in overcoming extraordinary emergencies, which show that > NE S s, aan as yy Z Wa Re We , ifleg NN A \ ’ they have sufficient reasoning powers to meet the exigencies of their life ; their ordinary acts being instinctive—namely, Fig. 361.—Diagram of an ant’s nest (Ecodoma), the chambers below containing the ant food.—After Belt, the results of inherited habits. ‘The leaf-cutter ants of Central and South America (Fig. 360) are famous from MUD-WASPS. 363 their leaf-cutting habits ; the soldiers have large triangular heads, while the workers have much smaller rounded heads. Fig. 362 represents a species of Eciton. Fig. 362,.—Eciton. Fig. 363.—Mud-dauber, The mud-daubers (Pelopeus, Fig. 363) build their nests against stone walls, of pellets of mud, while the sand- and mud-wasps dig deep holes (Fig. 364, Sphex ichneumonea Fig. 364.—Sand-wasp (Sphex), Natural size. Linn.) in gravelly walks, and have the instinct to sting grasshoppers in one of the thoracic ganglia, thus paralyzing the victim, in which the wasp lays her eggs; the young 364 ZOOLOGY. hatching, feed upon the living but paralyzed grasshoppers, the store of living food not being exhausted until the larval Fig. 3455.—Nest of Andrena. g, level of ground; 4, first-made cell, con- taining a pupa; 2,2, larve; e, pollen mass with an egg laid on it; f, pollen mass freshly deposited by the bee.— Emerton del, wasp is ready to stop eating and finish its transformations. The genuine paper-making Wasps are numerous in species; here the workers are winged, and only differ from the females or queens in being rather smaller and with unde- veloped ovaries. The series of genera from Odynerus, which builds cells of mud, and in which there are no workers, up to those which have work- ers and build paper cells, such as Polistes, is quite continu- ous. The gennine paper- making wasps, such as Vespa, build several tiers of cells, ar- ranged mouth downward, and enveloped by a wall of several thicknesses of paper. In the Vespe, the females found the colony, and raise a brood of workers, which early in the summer assist the queen in completing the nest. The bees also present a gradual series from those which are solitary, living in holes in the earth, like the ants (Fig. 365, nest of .4n- drena vicina Smith’, and form- ing silk-lined carthen cocoons, to those which are social, with winged workers, slightly dif- fering from the queens. The queen humble-bee hybernates, and in the spring founds her colony by laying up pellets ot CLASSIFICATION OF INSECTS. 365: pollen in some subterranean mouse-nest or in a stump, and the young hatching, gradually eat the pollen, and when it is exhausted and they are fully fed, they spin an oval cylin- drical cocoon ; the first brood are workers, the second males and females. ‘The partly hexagonal cells of the stingless bees of the tropics (Melipona) are built by the bees, while the hexagonal cells of the honey-bee are made by the bees from wax secreted by minute subcutaneous glands in the abdomen. Though the cells are hexagonal, they are not built with mathematical exactitude, the sides not always being of the same length and thickness. The cells made for the young or larval drones are larger than those of the workers, and the single queen cell is large and irregularly slipper-shaped. Drone eggs are supposed by Dzierzon and Siebold not to be fertilized, and that the queen bee is the only animal which can produce either sex at will. Certain worker-eggs have been known to transform into queen bees. On the other hand, worker-bees may lay drone eggs. The maximum longevity of a worker is eight months, while some queens have been known to live five years. The latter will often, under favorable circum- stances, lay from 2000 to 3000 eggs a day. The first brood of workers live about six weeks in summer, and are suc- ceeded by a second brood. Crass VI.—INSECTA. A distinct head, thorax, and abdomen, three pairs of legs; breathing by trachee; usually two pairs of wings; usually with a metamorphosis, which is either incomplete or complete. Series J. Ametadbola, or with an incomplete metamorphosis. Order 1. Thysanura.—Wingless, minute, with a spring; or ab- domen ending in a pair of caudal stylets; usually no compound eyes; no metamorphosis (Podura, Campodea, Lepisma). . Order 2. Dermaptera.—Body flat; the abdomen ending in a forceps; fore-wings small, elytra-like; hind-wings ample, folded under the first pair (Forficula). 366 ZOOLOGY. Order 3. Orthoptera.—Wings net-veined; fore-wings narrow, straight, not often used in flight; metamorphosis incom- plete; pupa active (Caloptenus, Locusta, Phaneroptera, Acheta). Order 4. Platyptera.—Body usually flattened; pronotum usually large and square; often wingless (Mallophaga or bird-lice, Perla, Psocus, white ants). Order 5, Odonata.—Prothorax small; thorax spherical; both pairs of wings of nearly the same size, net-veined. Larva and pupa aquatic; labium forming a large mask (Agrion, Libel- lula). Order 6. Plectoptera.—Mouth-parts nearly obsolete; wings net- veined, hinder pair small, sometimes wanting; abdomen ending in three filaments. Larve aquatic, with large jaws, and with gills on the side of the hind body (Ephemera). Order 7. Thysanoptera.—Mouth-parts forming a short conical sucker; palpi present; wings narrow, fringed; abdomen end- ing in a long ovipositor (Thrips). Order 8. Hemiptera.—Mouth-parts forming a sucking beak; pro- thorax usually large; fore-wings often thickened at base; pupa active (Coreus, Arma, Pentatoma, Cicada, Coccus, Aphis). Serres HT. Metabola, or with a complete metamorphosis. Order 9. Neuroptera.—Wings net veined; mouth-parts free, adapted for biting; ligula large, rounded; prothorax large, square. Larve often aquatic (Corydalus, Chrysopa, Myr- meleon) Order 10. Mecaptera.—Wings somewhat net-veined, or absent. Larve like caterpillars (Panorpa, Boreus). Order 11. Trichoptera.—Wings and body like those of moths; mandibles obsolete in imago. Larve usually aquatic, liv- ing in cases (Phryganea). Order 12. Coleaptera,—Fore-wings thick, ensheathing the binder pair, which are alone used in flight; mouth-parts free, adapted for biting; metamorphosis complete (Doryphora, Clytus, Lucanus, Harpalus, Cicindela). Oider 13. Siphonaptera. — Wingless; mouth-parts adapted for sucking. Larva maggot-like, but with a well-developed head and mouth-parts (Pulex). Order 14. Diptera.—But one pair of wings; mouth-parts adapted for lapping and sucking; a complete metamorphosis (Musca, (Estrus, Syrphus, Cecidomyia, Tipula, Culex). CLASSIFICATION OF INSECTS. 367 Order 15. Lepidoptera.—Body and wings covered with scales; maxille lengthened into a very long tongue; larve (cater- pillars) with abdominal legs (Tinea, Geometra, Noctua, Bombyx, Sphinx, Papilio). Order 16. Hymenoptera.—Wings clear, with few veins; mouth- parts with a variety of functions, 7.¢., biting, lapping liquids, etc. In the higher families the thorax consists of four segments, the first abdominal segment of the larva being transferred to the thorax in the pupa and imago. Metamorphosis complete (Tenthredo, Cynips, Ichneumon, Sphex, Vespa, Apis). TABULAR VIEW OF THE SIXTEEN ORDERS OF INSECTA. 5 s § 8 oe tie Ss gs .s : Bi ess = Tete Beg [32s S88 : es Ss & & : 8 gs 8 2 § & BSB os S BS § SF. & ss fF ¢£ ma &§ § § Re Fs sg ~ SS 2 8 2 ¢ | * s 88 8 || | }y eee a S ee | 4 | a | | | Metabola | Ametabola. Thysanura. (Campodea.) Laboratory Work.—In dissecting Myriopods, spiders, and insects, the ‘dorsal portion of the integument should be carefully removed with fine scissors, leaving the hypodermis untouched; this should then be raised, disclosing the delicate heart or dorsal vessel. The alimentary canal will be found passing through the middle of the body; it should be laid open with the scissors, or, better, a hardened alcoholic specimen an readily be cut in two longitudinally, and if the section is true, the «esophagus and crop—for example, of a locust—can be laid open, and 368 ZOOLOGY. the rows of teeth examined. The thoracic and abdominal portions of the nervous system, which lies loosely on the fioor of the body, can be readily found by raising the alimentary canal ; but the brain and infra- cesophageal ganglia cau best be detected by a lonyitudinal section of the head. The ovaries always lie above the iutes.ine, and the two oviducts unite below the nervous cord to form the common duct which opens on the ventral side of the third segment in front of the anus, which is situated dorsally. Insects should be dissected in a shallow pan lined with wax or cork, and tlie parts floated cut ; fresh specimens are desirable. The body may also be dissected, each segment with its. appendages being separated and glued in their true sequence toa card. By simply dissecting an insect in this way, the student will acquire a valuable Knowledge of the external structure of insects, Dragon-fly (Diplax Elisa). CHAPTER VIII. BRANCH VIIL—VERTEBRATA. General Characters of Vertebrates.— The fundamental characters of the Vertebrates are the possession of a segmented vertebral column, enclosing a nervous cord, and a skull which contains a genuine brain; yet these features, though common to most Vertebrates, are wanting in the lancelet (Amphtoxus) and in a degree in the hag-fish, and even the lamprey ; but the essential character is the division of the body-cavity by the notochord (in the lancelet, etc.), or by the back-bone of higher Vertebrates into two sub- ordinate cavities, the upper (neural) containing the nervous cord, and the lower (enteric) the digestive canal and its ap- pendages and the heart. These are the only characters which will apply to every known Vertebrate animal (compare p. 206 with Figs. 366, 370, and 371). In general, however, the Vertebrates are distinguished from the members of the other branches by the following characters: they are bilaterally symmetrical animals, with a dorsal and ventral surface, a head connected by a neck with the trunk ; with two eyes and two ears, and two nasal open- ings, always occupying the same relative position in the head ; an internal cartilaginous or bony, segmented skeleton, con- sisting of vertebre, from the bodies of which are sent off dorsal processes which unite to form a cavity for a spinal cord, the latter sending off spinal nerves in pairs * correspond- ing to the segmentations (vertebree) of the spinal column. * Except in Amphioxus, in which the spinal nerves arise right and left alternately. 370 ZOOLOGY. From the underside of the vertebre are sent off processes articulating with the ribs, which enclose the digestive and central circulatory organs. There is a skull formed by a con- tinuation of the vertebral column, enclosing a genuine brain, consisting of several pairs of ganglia. To the vertebral col- umn are appended two pairs of limbs, supported by rays ir- regularly repeated, or a series of bones of a definite number, Fig. 306.—Transverse section of a worm, of Amphioxus, and of a Vert: brate con- trasted. a, outer or skin layer; 6, dermal counective layer; c. muselex; d, seg- mental organ: #, arterial, aud z, venous bloud-vessel; g. intestiue ; /, notochord.— After Haeckel. attached to the vertebral column by a series of bones called respectively the shoulder and pelvic girdle. It will be observed that the fact of segmentation, so prom- inent a feature in the Worms and Arthropods, survives, or at least reappears In a marked degree in the Vertebrates, as seen not only in the vertebral column, but in the arrangement of the spinal nerves. It is perceived also in the arrangement of the muscles into masses corresponding to the vertebra ; and in the segmental organs or tubes forming the kidneys of the sharks and rays, while segmentation is especially marked in the disposition of the primitive vertebre of the early em- bryos of all Vertebrates. The digestive canal consists of a mouth with lips or jaws, armed with tecth, a pharynx leading to the Jungs ; an wsoph- agus and thyroid gland ; sometimes a crop (ingluvies), often a fore-stomach (proventriculus) ; a stomach and intestine, cloaca and vent. Into the beginning of the intestine passes a duct leading from a large liver; a gall-bladder. usually a pancreas, and a spleen, also communicating with the intestine. The products of digestion do not all pass through the walls of the stomach and directly enter the circulation, as in the invertebrates, but there is a system of intermediate vessels NERVOUS SYSTEM OF VERTEBRATES. d71 called the lacteal system or absorbents, which take up a part of the chyle from the digestive organs and convey it to the blood-vessels, There is atrue heart, with one, generally two, auricles, and one or two ventricles with thick, muscular walls, and besides arteries and veins, a capillary system, 7. e., minute vessels connecting the ends of the smaller arteries with the smaller veins. There are no genuine capillaries in the lower animals exactly comparable with those of the Vertebrates. The blood is red in all the Vertebrates except the lancelet, and contains two sorts of corpuscles, the white corpuscles like the blood-corpuscles of invertebrates, and 1ed corpuscles not found in invertebrates, and which are said by some authors to be derived from the white corpuscles. While fishes and larval Amphibians breathe by gills, all land and amphibious Vertebrates breathe the air directly by means of cellular sacs called lungs, and connected by a trachea with the pharynx, the trachea being situated beneath the cesopha- gus, and the opening from the mouth into the pharynx lead- ing into the trachea being placed below the throat or passage to the esophagus. ‘The air filling the cells or cavities of the lungs passes by osmose through the walls of the cells into the blood sent by the heart through the pulmonary artery, and after being oxygenated, the blood returns by the pulmonary vein to the heart. On the other hand, carbonic acid passes from the blood out of the lungs through the trachea. The nervous system of Vertebrates consists of a brain and spinal cord. The brain consists of four pairs of lobes, 1. ¢., the olfactory lobes, cerebral hemispheres, the optic thalami (Thalamencephalon) and pineal gland, and the optic lobes; and two single divisions : the cerebellum and the beginning of the spinal cord, called the medulla oblongata. The olfactory lobes are the most anterior, and send off the nerves of smell to the nose. The cerebral hemispheres in the fishes and amphibians are little larger than the adjoining lobes, but in the reptiles become larger, until in the mammals, and especially in the apes and man, they fill the greater part of the brain-box and overlap the cerebellum ; the latter, in the mammals, also exceeding all the other lobes in size, excepting the cerebrum. Br2 ZOOLOGY. Attached to a downward prolongation (infundibulum) of the optic thalami is the curious pituitary body. The medulla sends nerves to the skin and muscls, giving sensibility and motion to the face, eyes and nose, to the larynx and sensitive portion of the lungs; a pair also is sent to the lungs and heart. If the spinal marrow is severed, the parts below are paralyzed ; if the medulla is cut or broken up mammals die at once, while the lower Vertebrata die sooner or later. The brain in an embryo originally consists cf three vesi- cles or primitive lobes; and the correspondence between Fig, 367.—Diagrammatic, tonyitudinal and vertical section of a Vertebrate brain. Ms, mid brain; what lies in front of this is the fore brain, and what lies behind, the ‘hind brain. L, jamina terminalis; O/f, olfactory lobes ; Hmp, cerebral hemi- spheres; Th Z, thalamencephaton ; Pa, pineal gland ; Py, pituitary body; FY, fo- Tamen of Munro: cs, corpus striatum ; Th, optic thalamus; ¢ oe corpora quadri- gemina; C'C, crura cetebri: Ch, cerebellum ; LY; pons varolii ; a, Taortulla oblon- gata; t olfactorii ; ZI, optici 5 I7Z, point of exit from the brain of the Motores oculorum ; IV, of the pathetici ; , of the abducentes; V- a origin of the other cerebral nerves ; 1, olfactory ventricle ; 2, lateral ventricle » third ventricle ; 4, fourth ventricle.—After Huxley. the three primitive lobes, called respectively the forc, mid, and hind brain, may be seen by the following table : TABULAR VIEW OF THE SUBDIVISIONS OF THE VERTEBRATE BRAIN Olfactory lobes or ganglia, with their ventricles (rhinen- cephalon). Cerebrum «r cerebral lobes or lem’spheres (with the two lateral or first and second ventricles, forming the prosencephalon or prothalami). Optic thalami, with the third ventricle and conarium above and hypophysis (pituitary body) below { (Thalamencephalon pineal gland). Fore brain. NERVOUS SYSTEM OF VERTEBRATES. 373 Optic lob s, corpora bigemina or quadrigemina (mesen- cephalon). Crura cerebri. Optic ventricle or Iter a tertio ad quartum ventriculum. Mid brain. Cerebellum (with its ventricle and the pons varolii, form- Hind brain. ing the metencephalon), Medulla oblongata and fourth ventricle. The accompanying sketches represent the typical nervous system of an amphibian, which also resembles that of many fishes, and even the lower Aeptilia. The spinal cord (Fig. 368) usually extends through the whole length of , the spinal canal, except in the toads and frogs, birds and many mammals, - where it stops short of the end of its ¢7 canal. In those Vertebrates with *~ limbs, the cord enlarges where the nerves which supply them are sent off ; 4 these are the cervical or thoracic, and 4 t | lumbar enlargements, especially large in turtles and birds. The white and gray substance of the brain continues in the cord. As the most essential characteristic of Vertebrates is the internal skeleton (endoskeleton) we will enter more into detail in describing it, and afterwards notice the external skeleton (exo- ckeleton). oF, 20% ala ang. spina 4 above. B. from below. a, ol- In the embryos of higher Vertebrates for, lonees & corebral and in the adult lancelet, hag-fish and hemispheres; ¢, optic lobes; 5 d, cerebellum in the form of a Jamprey, the vertebral column is rep- lamella bridging over the ta 5 fourth ventricle (s) ; m, spinal resented by a rod-like axis (notochord cord; t, terminal cord.—After 3 3 s Gegenbaur. ‘or chorda dorsalis) which is composed of indifferent, or only partly organized cells, the substance of the chord resembling cartilage. These chordal cells secrete a membrane called the chordal sheath. The notochord 1s not 3874 ZOOLOGY. segmented. In all Vertebrates above the lamprey, the verte- bral column grows around the notochord, which finally Fig. 369.—Transverse section through the spinal cord of a calf. a, auterior, 3, posterior longitndinal fis-ure ; c, central canal; @, anterior, e, posterior cornua; J, substantia gelatinosa; g, anterior column of the white substauce ; 2, lateral, i, pos- terior column ; &, transverse commissures. —After Gegenbaur. Fig. 370.—Section through the vertebral column of Ammoceetes (lamprey). Ch, no- tochord; ¢s, chordal sheath ; m, spinal chord ; a, aorta; v, veins. Fig 371.—Section through the spinal column of a young salmon. Ch, notochord ; cs, chordal sheath; m, spinal chord; &, superior, 4’, inferior arch (rudimentary) ; a, aorta; v, veins.—After Gegenbaur. forms the central portion of the bodies of the vertebre, and in the higher Vertebrates is wholly effaced; the centra or LIMBS OF VERTEBRATES. 375 bodies of each vertebra of a lizard, bird or mammal being solid bone. Figs. 370 and 371 represent the relations of the notochord in an adult lamprey and a young fish. The vertebra of a bony fish or higher vertebrate consists of a body, with a dorsal or neural spine; a pair of oblique processes (zygapophyses) arching over and enclosing the spinal cord; and ¢ransverse processes, bending downwards, to which the ribs are articulated ; certain of the thoracic ribs uniting with the sternum or breast-bone 5.) 9. 97-7 3872, ae of a Vertebra (Figs. 372 and 373). with’ ‘its body (5), rib (7), breast-bone Vertebrax like those of fishes, ied Asians pievesan a ensuene which are hollow or concave at P™°°*s*°* each end, are said to be amphicewlous ; those hollow in front and convex behind procelous, as in most toads and frogs and crocodiles, and most existing lizards, and those convex in front and concave behind opisthocelous, as in the garpike, some Amphib- jans (the salamanders and cer- tain toads, Pipa and Bombinator). ee ee Vertebrates never have more buzzard (Butco vulgaris). ¢, centrum than two pairs of limbs, an an-: or body; s, superior spinvus pro- cess; ¢7, transverse process; io, terior and hinder pair ; the pecto- nitalam of the rib--After Geces, Tal pair of fing of fishes represent . Daur: the fore limbs of Amphibians and higher Vertebrates, and the arms of man; the two ventral fins represent the hind legs of higher Vertebrates, and the . legs of man. Lach pair of limbs is connected by ligaments: und muscles to a girdle or set of bones, called respectively the shoulder girdle and pelvic girdle, each girdle being con- nected by muscles to the vertebral column. The shoulder girdle consists of a clavicle (or collar-bone), scapula (or shoulder-blade), and coracoid bone, usually a process of the scapula. These bones differ greatly in the different classes, 376 ZOOLOGY. and are reduced to cartilaginous pieces in sharks. The pelvic girdle, or pelvis, consists of three bones, 7.e., one dorsal, the alium, and two ventral, the anterior of which is called pubis, and the posterior ischium. The limbs each consist of a single long bone, succeeded by two long bones, followed by two transverse rows of short wrist or ankle bones, and five series of long finger or toe bones, called phalanges. For example, in the fore limb of most Vertebrates, as in the arm of man, to the shoulder gir- dle, 7.e., at the point of junction of the three bones com- posing it, is articulated the humerus ; this is succeeded by Fie 375. Fig. 374.—Sternum and shoulder girdle of Frog (Rana temporaria). p, body of the sternum ; ac, scapula; sc’, stupra-scapula; co, coracoid hone, fused in the middle line with its fellow of the oppo~ite side (s) ; /, clavicle ; e, epis- ternum. The extreme shade: double portion below pis the xiphisternum. The cartilaginous parts are shaded.—After Gegenbaur. Fig. 375.—Fore-leg of a seal. S, scapula; H, humerus; O, olecranon or tip of elbow; &, radius; U, ulna; Po, pollex, or thumb. ig. 376.—Pelvis or pelvic bones on one side of a marsu piai oeeace) 62, ilium; a, situated on the pubic boue (pubis) indicates the acetabulum or concavity for the artic- ulation of the head of the femur; 63, ischium, consolidated with the pubis. The three bones thus consolidated form the os innominatum ; m, marsupial bones ar- ticulated to the pubic boues.—After Owen. the ulna and radius, the carpals, the metacarpals, and the fin- ger-bones or phalanges, the single row of phalanges forming a digit (finger or toe). To the point of union (acetabulum, Fig. 376, a) of the three pelvic bones is articulated the fe- ‘mur, or thigh; this is succeeded by the tibia and fibula (shank-bones), the tarsal (ankle-bones) and metatarsal bones, and the phalanges or bones forming the digits (toes). Figs. 378-380 represent the simplest form of the posterior limbs in the higher Vertebrates, that of the bird showing an COMPOSITION OF THE SKULL. 377 extreme modification in form. At first all limbs arise as little pads, in which the skeletons subsequently develop, and in early life the limbs of all Vertebrates above the fishes are much alike, the mod- ifications taking place shortly before birth. Ac- cording to Gegenbaur and others, the limbs of Vertebrates have been probably derived from the pectoral and ventral fins of fishes in which the fin-rays are irrela- tively repeated. * In the fins of fishes there is a simple system of leverage ; in the limbs of higher air-breathing pip a77—a, sk Vertebrates, formed by and é, its continuation (urostyle) ; 7, suprascap- ula; g, humerus; 2, fore-arm bones; i, wrist walking on land, @& COm-_ bones (carpals and metacarpals) ; d, ilium ; m, pound system of lever- fret pan of, ieee Cee ae geste ones or phalanges.—After Owen. age (Wyman). The head of all Vertebrates above the lancelet is supported by a more or less perfect cartilaginous or bone framework, the skull (cranium), or brain-box (Fig. 381). It is a contin- uation of the vertebral column, and protects the brain, besides forming the support of the jaws, tongue-bone {nyoid bone), and branchial arches. The series of lateral (visceral or branchial) arches varies, but there may be nine; the most anterior (if it be counted as the first one, Fig. 382, a, 6, c) is formed by what are called the labial carti- lages; next comes the mandibular arch (0, 7), which is suc- ceeded by the hyoid arch (II.) and the six branchial arches. In the embryos of all Vertebrates these visceral arches are * A modified form of this theory is advocated by Balfour and J. K. Thatcher, who attempt to show that the limbs with their girdles were derived from a series of similar simple parallel rays, and that they were ofiginally a specialization of the continuous lateral folds or fins of embryo fishes, and probably homologous with the lateral folds of the adult lancelet (Amphioxus). 3718 ZOOLOGY. well marked: of the slits or openings between them, the first is destined to form the mouth, the next pair of slits Fig. 378. Fie. 379, Fie. 380. Fig. 378,—Hind - of a larval Salamander. The dotted lines are drawn through the rays to which the different pieces belong. Fe, femur: 7, tibia; ¥, fibula; i, ¢, c, #, tarsal bones; é, os intermedium; ¢, tibiale; /, fibulare; c, centrale ; 1-5, the five tarsals, The first row of phalanges are called metatarsals (in the hand, meta. carpals). Fig. 379.—Bones of the foot of a Reptile (lizard) A, and an embryo bird, B. J, fe- mur; ¢, tibia; , fibula; ¢s, upper, ¢é. lower pieces of the tarsus; m, metatarsus ; LY, metatarsalia of the toes. = . Fig. 380.—Leg ot the Buzzard (Buteo vulgaris). a, femur; }, tibia; WY, fibula; ¢, tarso-metatarsus ; c’, the same piece isolated, and seen from in front; da’, a”, d’”, the four digits or toes.—After Gegenbaur, in the Amphibia and higher Vertebrates forms the ear-pass- ge, while the other slits may remain open in fishes, form- COMPOSITION OF THE SKULL. 379 ing gill-slits or spiracles, but are closed in the higher Verte- brates. Asa rule, the skull is symmetrical, exceptions being found in the flounders and the bones about the nose of cer- Fig. 381.-Skull of the Lion. 2, occipital condyle ; 7, Parietal bone and sagittal crest ; 8, paroccipital ; 27/, squamosal bone ; 27, zygomatic arch; 26, malar bone ; 11, frontal bone ; 12, post-orbital process ; 15, nasal bone; 21, maxillary bone ; 22, premaxillary bone ; 32, mandible ; 3, occipital crest ; c, canine teeth ; py, second pre- molar ; m, molar tooth.—After Owen. tain whales and porpoises. The base of the skull is perfo- rated for the exit of the nerves proceeding from the base of the brain, and the hinder bone (occipz) is perforated ( fora- men magnum) for the passage of the spinal cord from the medulla oblongata. It is probable that there is a general parallelism between the head of Insects and Vertebrates. While the head of Fig. 382.—Skull and visceral skeleton of a Selachian e s (diagram). occ, ope region; da, wall of the laby- winged insects, for rinth; eh, ethmoidal region; n, nasal pit ; @, first, d, ¢, i second labial cartilage ; 0, superior, 2, inferior portion example, consists of of the mandibular arch IL; IL, hyoid arch; ZZZ.- VII. . (1-6), branchial arches.—After Gegenbaur. a certain number of segments, homologous with those of the rest of the body, and with mouth-parts homologous with the limbs; so the skull is also segmented, and an expansion and continuation of the vertebral column. Gegenbaur even maintains that the various arches of the head are homologous with the limbs, 380 ZOOLOGY. On the other hand, while the brain of insects is a single pair of ganglia like those of the rest of the body, the differ- ent ganglia forming the brain of Vertebrates are concen- trated in the head alone; still the different pairs of nerves sent off from the base of the brain are homologous with the spinal nerves, sent off at intervals corresponding to each vertebra. There are two theories of the composition of the skull. That of Oken, Goethe, and of Owen, who believed that the skulls of the bony fishes and mammals were composed of three or four segments. It should be noticed that these views are based on an examination of highly specialized ver- tebrates. From a study, however, of the more generalized types of fishes (such as the sharks:, and the embryos of ver- tebrates belonging to different groups, the old vertebrate theory of the skull has been discarded, and the view of Ge- genbaur, confirmed by Salensky, is probably nearly the cor- rect one. As stated by Gegenbaur : 1. The skull is comparable to a portion of the vertebral column, which contains at least as many vertebral segments as there are branchial arches. This view is borne out by the following facts : a. The notochord, which forms the foundation of the vertebral column, passes through the cranium in the same Way as it passes through the vertebral column. 6. All the nerves which pass out of the base of the skull (or that portion traversed by the notochord) are homologous with the spinal nerves. c. The difference between the skull and vertebral col- umn consist of secondary adaptations to certain con- ditions, which are external tothe skull, and are partly due to the development of a brain. 2. The skull may be divided into two regions, a vertebral portion and an anterior evertebral portion, lying beyond the end of the notochord. 3. The number of vertebree which enter into the forma- tion of the skull are nine at least (according to Sulensky, in the sturgeon, seven) ; the exact number is immaterial. TEETH OF VERTEBRATES. 381 In the fancelet there ia no skull, or even the rudiments cf one (unless the semi-cartilaginous supports of the tentacles be regarded as such), hence the Vertebrates are divided into the skulless or acraniate (.{crania, represented by the lance- let alone) and the skulled or craniate (Craniota), the latter series comprising all forms from the hag-fish to man. In the Craniota the skulls may be, according to Gegenbaur, di- vided into two groups. In the hag and lamprey the noto- chord is continued into the base of a small cartilaginous capsule, enclosing the brain, and which represents the skull of higher Vertebrates (Craniota). This capsule behind is continuous with the spinal column. With the skull of the second form two jaws are developed, hence all the vertebrates above the hag and lamprey form a series (Gnathostomata) opposed to the former, or Cyclos- tomata. In the Gnathostomata there is a gradual modification and perfection of the skull. In the sharks it may be quite sim- ple and cartilaginous ; in the bony fishes it is highly special- ized, consisting of a large number of separate bones. In the Amphibians we first meet with askull consisting of few bones, easily comparable with those of mammals; in the reptiles and birds the ear-bones are external, forming the large quadrate-bone by which the lower jaw is articulated to the skull. A progress is seen in the mammals where the quadrate-bone becomes internal—one of the ear-bones (mal- leus). Now, also, the brain becoming much larger, evincing amuch higher grade of intellect, the skull is greatly en- larged to accommodate the great increase in size of the cerebrum and cerebellum, the perceptive and reasoning fac- ulties predominating over those regions of the brain and skull devoted to perceiving, grasping, and masticating the food. Though not properly forming part of the skeleton or de- veloped with it, we may here consider the teeth. The teeth of Vertebrates are formed from the modified epidermis and cutis, or dermis; the former secretes the enamel and the latter is changed into the pulp or dentine. The simplest form of tooth is conical. In the jawless hag there are no teeth in the lips, but a single median tooth on 382 ZOOLOGY. the palate and two rows of comb-like teeth on the tonguc. In the lamprey the edges of the circular mouth are provided with circular rows of conical horny teeth. The teeth of higher Vertebrates are derived from the cells of the mucous membrane of the mouth, which is formed of connective tis- sue as well as epithelium. The teeth of fishes are developed not only in one or several rows in the lip, but may also arm the bony projections into the mouth-cavity of the palate, yomer and parasphenoid bones and the hyoid and bran- chial arches. In the Amphibia teeth survive on the palatine and vomerine bones, more rarely on the parasphenoid ; among the reptiles, the snakes and lizards alone have teeth on the palatine and pterygoid bones, while in the crocodiles and in mammals the teeth are confined to the maxillary bones. In the geckos, snakes and the crocodiles, as well as the mam- mals, the teeth are inserted in sockets (alveoli) of the jaw. (Gegenbaur. ) In certain extinct birds (Odontornithes) there were teeth in the jaws, though all existing birds are toothless. It is said that rudimentary teeth were found by Geoffroy St. Hilaire in the jaws of a parrot. Blanchard afterwards found the germs of teeth there, though they never come through. Inthe Mam- mals the teeth are dif- Fig. 383.—Tecth of the Tasmanian devil. The ferentiated into inci- incisors are situated in front of the large conical 2 Seale canine teeth. 2, 3, premolars; m, 1-4. four molar sors, Canines, premo- Heh Aan Oe: lars and molars (Fig. 383). In descriptive anatomy the teeth are for convenience expressed by a formula, the number of teeth of the upper jaws being placed like the numerator of a fraction, and those of the lower jaw like the denominator, the initials of the names of the teeth being oe before the a thus ea a ee the dental formula of man is I; = SCALES, HAIRS, AND FEATHERS. 383 In the fishes, Amphibians and reptiles, the worn-out teeth are replaced by a succession of new ones ; in mammals (ex- cept cetaceans, where there is no change) there is but a single change, the first (milk) teeth being replaced by a second set of permanent teeth. The teeth of the lower Vertebrates are shed while swallowing the food. In the boa (Python) the teeth thus shed are found scattered along the intestinal canal and are discharged with the remnants of the food (Wyman). The dermal or exoskeleton consists of the scales of fishes, reptiles and certain mammals, such as the armadillo, the Fig. 884.—Vertical section through the skin of an embryonic shark. (,, corium or ‘dermis ; ¢,c, c, layers of the corium ; d, uppermost layer ; p, papilla; 2, epidermis ; , its layer of columnar cells; 0, euamel layer.—After Gegenbaur. feathers of birds and the hairs of mammals. Most scales arise from dermal papille (Fig. 384, »), and are covered over by a layer of enamel (Fig. 384, 0) developed from the epider- mis; so that the scales of sharks and rays, and turtles, arise from both the dermis and epidermis. A hair or feather is a modification of a scale ; the papilla is sunken in a pit of the dermis, the conical cap of epi- dermis arising from it ultimately forming the hair or feather. The plates of turtles, the scales of snakes and lizards, and feathers of birds are epidermal. In the horns of mammals, as of the rhinoceros, and the hoofs of the horse, the epi- dermal substance is penetrated by numerous long dermal papille. 384 ZOOLOGY. The head of the sturgeon, garpike, and of other ganoid fishes, is protected by solid dermal bones, and the shells of turtles are dermal structures. The color of the skin of Vertebrates is due to pigment- granules situated either in the epidermis or dermis, and in the chameleon they are contained in special sacs (chromatophores) which are under the control of the nervous system. The muscular system of Vertebrates arises from the middle germ- Se rs layer (mesoderm), and Fig. 385.—Placoid scale of dog-fish (vertical sec- -|~ tion siamminied). a, enamel layer ; 6, dentine of the 12 the germ the muscles. spine on the scale.—After Owen. in part avise from the primary segments indicated by the protovertebre, while in the adults of fishes and certain salamanders, the muscular system is distinctly segmented, corresponding to the seg- mentation of the ver- tebrul column, the four lateral trunk- muscles being divided ~ a into a number of seg- “GARIN ments by tendinous bands, which corre- spond in number to the vertebra (Gegen- baur). The eye in Verte- brates in its develop- mentalhistorybelongs to a different type of structure from that of any invertebrates, un Fig. 386.—Cyloid scale of roach, magnified, seen in less it be the larva] Section, A, und from the surface, B.—After Owen. Ascidians, for in both types the eye is said by Gegenbaur not. to be directly developed from the ectoderm, but from the ee —————— EYES AND EARS OF VERTEBRATES, 385- anterior portion of the central nervous system. ‘The differ- ence between the highly-developed eye of a cuttle-fish and a bony fish, for example, consists in the fact that the rods and cones (similar to those of the invertebrate eye) forming. a layer (the bacillar layer) behind the retina, are in the ver- tebrate eye turned away from, while in the invertebrates they are directed toward the opening of the eye. The ear of Vertebrates is at first a primitive otocyst, or ear-vesicle, which is gradually cut off and enclosed, forming a cavity of the skull. As we rise towards the mammals, the ear becomes more and more developed until the inner, middle, and outcr ear is formed ; the Eustachian tube being a modification of the first branchial cleft, forming the spiracle in the sharks (Sedachi?) and Ganoids. In the lancelet a head is scarcely more set apart from the rest of the body than in many invertebrates. In the fishes and Amphibians the head is not separated by a neck from. the trunk ; in reptiles the neck begins to mark off a head from the thorax, while in the birds and mammals the head is clearly demarked, the degrees of cephalization and trans- fer headward of those features subordinate to the intellec- tual wants of the animal becoming more striking as we ascend through the mammalian series to the apes, and finally man. The development of Vertebrates can scarcely be epitomized in a few lines. The mode of growth of Amphioxus is a general expression for that of all Vertebrates, for all develop from fertilized eggs, which undergo total or partial segmen- tation of the yolk, become three-layered sacs and assume the peculiar vertebrate characters, the development of the mam- mals differing from that of the other classes only in compar- atively unimportant features. The Vertebrates or Chordata are divided into three series or sub-branches: the Urochordata, the Acrania, and Crani- ota. The Urochordata are represented by the class 7und7- cata. The sub-branch Craniota is divided into six classes, the Marsipobranchs, fishes, amphibians, reptilia, birds, and miummals. 386 ZOOLOG ¥. Crass J.—Tuntcata (Asctdians, Sea Squirts). General Characters of Tunicates.—These animals were once regarded as mollusks, and in former editions of this book they were assigned a position among the worms, between the Brachiopods and the Nemertina. Recent advances in our knowledge of Ascidians on the one hand, and of the primitive features of the Vertebrates on the other, show quite conclusively that the Ascidians, par- ticularly the adult form Appendicularia, and the larve of those Ascidians which undergo a metamorphosis, have the fundamental characters of Amphioxus and the embryos of genuine Vertebrates, such as the lamprey. It will be remembered that these fundamental characters are the presence of a notocord, over which lies the central nervous system. No invertebrate 1s known to possess this dorsal position of the nervous system to the dorsal cord, unless we except Balanoglossus, which, as Mr. Bateson has shown, has a notocord lying under a central nervous cord. Tf the Jarva of this form was not like that of the worms and Echinoderms, presenting no vertebrate features, we might adopt Bateson’s view that Balanoglossus should be placed at or near the base of the Vertebrate series, in a group Pro- tuchordata. The result of admitting the Tunicates into the same branch or type as the Vertebrates has led to the proposal of a group Chordata, including the Tunicates and the genuine Vertebrates; but as Amphioxns seems to be a connecting- link between the Tunicates and the genuine Vertebrates, beginning with the hag-fish and the lamprey. we will, for convenience, retain the familiar word Vertebrata for all ani- mals having a notocord (either in the embryo, larval, or adult state) situated between a neural and an enteric cavity. Fig. 386° will show the close resemblance of the larval as- cidian to the embryo lamprey. Tt will be seen that even the larval Ascidian has an incipi- ent brain, consisting of two ganglia, from which arise a spinal nervous cord, with even spinal nerves. The intestine in the larval Ascidian is bent and ends in front, but in the adult tadpole-shaped Appendicularia the end of the intes- tine is ventral and opens directly outwards. POSITION OF THE ASOIDIANS. 387 While all Tunicates, except Appendicularia, are more or less degenerate, losing their vertebrate characters, in Appen- dicularia these are retained. ‘The heart is situated ventrally, occupying nearly the same relation as in Fig. 386’. Accord- ing to Claus,* “the elongated cerebral ganglion is divided by constrictions into three parts; it is connected with a cili- ated pit and an otolithic vesicle, and is prolonged into a nerve-cord of considerable size. The latter is continued into the tail, at the base‘of which it swells out into a gan- glion; in its further course it forms several small ganglia, ye ad BES ol - ‘ht sp Fig. 3862.—Diagram of larval] Ascidian. Letteringas in Fig. 386!. m, mouth; 7, digestive tract; sp, spiracles in the pharyngeal portion; ht, heart; e, eye; er, ear; br, brain; nc, nervous cord; 6’, b’’, mid-brain; cl, cerebellum; spn, spinal nerves; n, notocord; ol, nasal cavity; s, suckers (their homologues also occur in young garpikes and tadpoles). whence lateral nerves pass out. In consequence of a torsion of the axis of the tail, the originally dorsally-placed caudal nerve comes to have a lateral position. The segmentation of the nerve-cord in the tail (as shown by the ganglionic swellings) corresponds to the segmental divisions of the muscles, which recall the myotomes of Amphioxus. The large chorda-(urochord), which extends along the whole length ofthe tail, constitutes another point of resemblance to Amphioxus.” * Text-book of Zoology, English translation, ii., p. 100. B83 ZOOLOGY. Order 1. Ascidiacea.—As an example of Tunicates (Fig. 386°), we will now study the internal anatomy of Boltenia. On examining the test of this Ascidian, which is mounted on a long stalk, the oral or incurrent orifice is seen at the insertion of the stalk, and the atrial or excurrent orifice on the same side near the opposite end. On cutting open the thick test and throwing the flap over to the left, the deli- cate mantle or tunic is disclosed ; it extends a short distance into the stalk or peduncle. This thin hyaline mantle is crossed by two sets of narrow raised muscular bands ; the transverse fibres are arranged concentrically to the two ori- fices, so as to close or open them, the longitudinal ones curv- ing outward from the left side. Currents of sea-water laden with organic food pass into the oral orifice, which is surrounded by a circle of tentacles pointing inward, and thence into a capacious saccular bran- ehial chamber within the mantle, which contracts at the bottom, where the esophageal opening is situated. The -walls of this chamber, which is over an inch long in a good- sized specimen, and gathered into fringed folds, is sieve-like with ciliated perforations (compare Fig. 386’ e), making the walls like a lattice-work, the blood couising through the ves sels pessing between the meshes of the sieve-like waus. The cesophagus, which lies at the bottom of this branchial chamber, is also situated near the intestine passing over the anal end into the short stomach. The intestine is long, ‘passing up to the insertion of the stalk, where it is held in place by muscular threads extending into the stalk and attached to the mantle; it then suddenly bends back and passes straight down to the vent, which opens opposite to the atrial orifice ; the end of the intestine is in part revolute and provided with a fringe of about twenty filaments. The liver forms a broad and flat mass of a bright livid green, and consists of three flat lobes each composed of eight or nine lobules, with very short ducts enveloping the inner aspect of the intestine. The ovaries are two yellowish, large and long lobulated masses extending nearly the whole length of the body, while the right one is a little smaller, and situated in -the fold of the intestine. The atrium is that region of the STRUCTURE OF APPENDICULARIA. 389 body-cavity which lies between the end of the intestine and the atrial or excurrent orifice; into this atrial region the feces, eggs, etc., pass on their way to and out of the atrial orifice. The simplest form of Tunicate is Appendicularia, which is tadpole-shaped, bearing a general resemblance to the larva of an ordinary Ascidian, so that it may be properly called a larval form. The Appendicularia isa pelagic animal, usually about one-half of an inch in length, found floating at or near the surface when the ocean is calm, and occurring in all seas afew miles from land or in mid-ocean. It swims ‘by means of its large, long, broad, flat tail, the body being Fig. 3862.—Anatomy of Boltenia.—Drawn by J. 8. Kingsley from the author's dissections. oval or flask-shaped. In Appendicularia flabellum, as de- scribed by Huxley, the caudal appendage is three or four times as long as the body. The mouth leads into a large pharyngeal or branchial sac; a narrow cesophagus at the bottom of this sac leads to a spacious stomach, with two lobes, from the left one of which the intestine arises, curves and ends midway between the mouth and insertion of the tail. In the middle of the hemal side (that side in which the heart is situated and bearing the atrial opening) isa fold of the wall of the pharyngeal cavity called the endostyle, On each side of this endostyle is an oval ciliated aperture, 390 ZOOLOGY. corresponding to the numerous branchial slits in the other Fig. 38¢8, — Struc- ture of a compound Ascidian, Amare- cium. A, branchial sac; m, stomach ; k, intestine ; c, mouth ; o, testis ; 7 7’, effer- ent duct of the tes- tis; C, ovary; p’, egg in the body-cav- ity; p”’, eggs in the atrium; 7, anus; 0, shows the site of the heart; /, liver; e, openin-s in walis of branchial chamber, —From Macalis:er, Ascidians, but in Appendicularia each ora} aperture leads into a funnel-shaped atrial canal, the open end of which terminates. beside the rectum. The heart is a large pulsatile sec situated between the two lobes of the stomach. The nervous system is much more fully developed than in other Tunicates, and is constructed on the Vertebrate type, consisting first of a ganglion situated below the mouth on the side opposite the atrial opening and opposite the anterior end of the endostyle. This nerve-centre throws off nerves to the sides of the mouth, and from it posteriorly extends a long cord past the cesophagus to the base of the tail, thence it extends along one side of the axis of the tail (urochord), swelling at regular intervals into small ganglia, from which from two to five small nerves radiate. On the cephalic ganglion a round ear-vyesicle is attached. Behind the posterior turn of the digestive canal is the testis and ovary, the Appendicularia being hermaphrodite, as Fol claims, though the ovary is developed later than the testis. The Appendicularia has no test, but secretes a fibrous envelope, which is at first gelatinous, loosely surround- ing the whole body, and allowing the creature the freest motion within its cavity. The general structure of an Ascidian may perhaps be more readily comprehended by a study of acompound Ascidian (Lmarecium), which grows in white or flesh-colored masses on sea-weeds, ete. On removing an Ama- recium from the mass and placing it under the microscope, its structure can be- per- ceived. The body is long and slender, as seen in Fig. 386°. The mouth leads by the capacious bran- STRUCTURE OF ASCIDIANS. 391 chial sac (A) to the stomach, while the intestine (B) is flexed, directed upwards, ending at the bottom of the atrium not far from the atrial opening. The reproductive glands are situated behind or below the bend of the intestine, the eggs being fertilized as they pass into the atrium, and the heart lies in the bottom of the body-cavity, being directly opposed to the nerve-ganglion (not represented in the figure), which lies between the two openings. In the perfectly transparent Perophora, which grows on the piles of wharves on the coast of Southern New England, one individual after another buds out (as also in Clavellina) from a common creeping stalk like a stolon. In this form the circulation of the blood-disks in the branchial vessels and the action of the heart can be studied by placing living ani- mals in glasses under the microscope. The heart is a straight tube, open at each end, and situated close to the hinder end of the branchial sac. After beating for a number of times, throwing the blood with its corpuscles in one direction, the beatings or contractions are regularly reversed and the blood forced in an opposite direction. Renal organs are apparently represented in Phallusia by a peculiar tissue, consisting of innumerable spherical sacs containing a yellow concretionary matter. In Aolgula and Ascidia vitrea Van Beneden, an oval sac containing concre- tions of uric acid lies close to the ovary. In the forms already considered the plan of structure is complicated, owing to the difficulty of distinguishing an anterior or posterior, a dorsal or ventral aspect of the animal. In Salpa and Doliolum, however, the body is more or less barrel-shaped, the hoops of the barrel represented by the muscular bands which, at regular intervals, surround the body. The mouth is near the centre of the front end, the pharyngeal sac is very large, and the digestive tract makes less of a turn than in the ordinary Ascidians, while the atrial opening lies directly at the posterior opening. The heart is truly a dorsal vessel, and the nervous ganglion is situated on the opposite side of the body. This relation of the anatomical systems is most clearly shown in the genus Doliolum, and we have here a slight approach to the sym- 392 ZOOLOGY metrical relation of parts seen in the true worms, and which strongly suggest the conclusion that the Tunicates are mod- ified worms. This conclusion is strengthened by the fact that in Appendicularia the ventral nervous cord is gangli- onated at intervals, as in the Annelids, while the twisted digestive tract is much as seen in Polyzoa and Brachiopods. Furthermore, the branchial sac is strongly analogous to the pharyngeal or gill-sac of Balanoglossus, and this structure in the Ascidian and whale’s-tongue worm anticipates the pha- ryngeal or gill-sac of Amphiorus and vertebrate embryos. The simple Ascidians attain to a large siz2, Lscidia callosa being about ten centimetres in diameter, quite round, and in form and color bears a strong resemblance to a potate. lscudia gigas, dredged by the Challenger Expedition, is from thirty to forty centimetres in diameter, and has a ganglion nearly as large as a pea. is as extreme as that of Southern Greenland ; frogs have ulso been 478 ZOOLOGY. observed at the Yukon River in lat. 60° N., but the climate there is milder than that of Labrador. The common toad and a salamander (Plethodon glutinosa Baird ?) extend to Southern Labrador. Nearly 700 species of existing Batrachians are known, 101 of which are North American, and about 100 fossil forms have been described. There are five orders of Batrachians, Professor Cope’s classification being adopted in this work. Those Batrachians with persistent gills are sometimes called Perennibranchiates. Order 1. Trachystomata.—The sirens have a long eel-like body, with persistent gilis; there is no pelvis or hind limbs, and the weak, small fore legs are four or three-toed. The great siren, Siren lacertina Linn., is sometimes a metre in length, and has four toes in the fore leg; it lives in swamps and bayous from North Carolina and Southern Illinois to the Gulf of Mexico. A small siren with three toes and small gills is Psewdobranchus striatus Le Conte. It occurs in Georgia. Order 2. Proteida.—This group is represented by the Proteus of Austrian caves and the mud-puppy (-Vecturus) of the United States. These Batrachians have bushy gills, with gill-openings and well-developed teeth. In Proteus, ~which is blind, there are three toes in the fore feet and two in the hinder pair. In the mud-puppy, -Veeturus (formerly Menobranchus) Jatera/’s Baird, each foot is four-toed. The head and body are broad and flat, brown with darker spots. It has small eyes and is ubout half a metre (from 8 inches to 2 fcet) inlength. It inhabits the Mississippi Valley. extend- ing eastward into the lakes of Ccentral New York. The Proteus as well as the mud-puppy lay eggs. Order 3. Urodela.—The tailed Batrachians or Salaman- ders rarely have persistent gills, these organs being larval or transitory ; the body is still long and fish-like, the tail some- times with a caudal fin-like expansion as in the newts, but is usually rounded, and the four legs are always present. With only one or two vivipareus excepnons, most of them lav ergs in the water. The eggs of Zriton are laid singly on sub- merged leaves; those of Diemyctylus viridescens are laid SALAMANDERS. 479 singly on leaves of Myriophyllum, which adhere to the glu- tinous egg, concealing it. (Cope.) Those of Desmognathus are laid connected by a thread both on land and in water. ‘The common land salamander, or Plethodon erythronotum Baird, lays its eggs in summer in packets under damp stones, leaves, etc.; the young are born with gills, as is the ‘case with the viviparous Salamandra atra of the Alps. The possession of gills by land salamanders, which have no use for them, and which consequently drop off in a few days, leads us justly to infer that the land salamanders are the de- scendants of those which had aquatic larve. The lowest form of this order is the aquatic Congo-snake or Amphiuma means Linn., in which the body is large, very long, round and slender, with small rudimentary two-toed limbs; there are no gills, though spiracles survive. It lives in swamps and sluggish streams of the Southern States. A step higher in the Urodelous scale is the Menopoma, which is still aquatic, with large spiracles, but the body and feet are as in the true salamanders. The Menopoma Alleghani- ense Harlan, called the hellbender or big water lizard, is about half a metre (14-2 feet) in length, and inhabits the Mississippi Valley. Allied to the Amphiuma is the gigantic Japanese salamander, Cryptobranchus Japonicus Van der Hoeven, which is a metre in length. Allied in size to this form was the great fossil salimander of the German Tertiary formation, Andrias Scheuchzeri, the homo diluvit testis of Scheuchzer, thought by this author to be a fossil man. In the true salamanders the body is still taile 1, the eyes are rather large ; there are no spiracles ; they breathe exclusively by their lungs, except what respiration is carried on by the skin. The genus Amdblystoma comprises our largest salamanders ; they are terrestrial when adult, living in damp places and feeding on insects. The larve retain their gills to a period when they are as large or even larger than the parent. 'The most interesting of all the salamanders is the Ambdblystoma mavortium, whose larva is called the axolotl, and was origi- nally described as a perennibranchiate amphibian under the name of Siredon lichenoides Baird. This larva is larger than £50 ZOOLOGY, the adult, terrestrial form, sometimes being about a third of a metre (12 inchez) in length, the adult being twenty centim- etres (8 inches) long, forming an example of what occurs in the Amphibians and also certain insects, of the excess in size and bulk of the larva over the more condensed adult form. This law is also strikingly observed in the Pseudes (Fig. 437). This fact of prematuritive, accelerated, vegetative development of the larva over the adult is an epitome of what has happened in the life of this and other classes of animals. The fossil, earliest representatives of the Amphibians, as we shall see farther on, were enormous, mon- strous, larval, prem- ature forms com- Fig. 435.—Siredon or larval Salamander.—From pared. with their de- Tenney’s Zoology. scendants. The same law holds good in certain groups of Crustacea (trilobites), insects, fishes, reptiles and mammals. The axolotl or siredon abounds in the lakes of the Rocky Mountain plateau from Montana to Mexico, from an altitude of 4000 to 8000 or 9000 feet; the Mexican axolotl being of a different species, though closely allied to that of Colorado, Utah and Wyoming. The Mexicans use the animal as food. Late in the summer the siredons at Como Lake, Wyoming, where we have observed them, transform in large numbers into the adult stage, leaving the water and hiding under sticks, ete., on land. Still larger numbers remain in the. lake, and breed there, as I have received the egg: from Mr. William Carlin, of Como. Thousands of the fully-crowa siredons are washed ashore in the spring when the ice melts. They do not appear at the surface of the lake until the last of June, and disappear out of sizht early in September. The eggs are laid in masses. andare 2 millimetres in diameter. Mr. F. F. Hubbell has observed in Como Lake, July 234,. young siredons four to six centimetres (14-24 inches) in length, and Svptember 3d t, heart , th Tr, trachea; th, thyroid; Oe, esophagus: yas -bladder Od, ovi- ; Pa, pancreas: , u, ureter; K, kidney: Ov, ovary; G, gal DT. lung: A, air-sac: Li. liver: ‘l. cloaca; R. rectum: O17, rizht oviduct cut off vena porte; J, intestine-—Drawn by C.5 Minot. ry G duct: POISONOUS SNAKES. 499 The Salenoglyph poisonous snakes may always be recog- nized by their broad, flattened heads, and usually short thick bodies. The poison gland of the rattlesnake (Fig. 442, a) is a modified salivary gland. The two fangs are modifications of maxillary teeth, each of which has been, so to speak, pressed flat, with the edges bent towards each other, and soldered together, so as to form a hollow cylinder open at both ends, the poison duct leading into the basal opening. When the fangs strike into the flesh, the muscles closing the jaws press upon the poison gland, forcing the poison into the wound. The poison-fangs are largest in the most deadly species, as : the viper ( Vipera), the puff adder (Clotho), the rat- tlesnake, and fer- de-lance (Zrigono- cephalus), but are small in the asps or hooded snakes (Naja). The bite of the rattlesnake is intensely painful; it is best cured by Fra. 442.—Head of the rattlesnake : aa, poison gland . and its excretory duct: ¢, anterior temporal muscle ; f, sucking, freely lan- posterior temporal muscle; g, digustricns; ”, external % pterygoid muscle ; i, middle temporal muscle 3 g, arti- cing, and by cauter- eulo-inaxillary ligament which joins the aponeurotic ice ' capsule of the poison gland; 7, the cervical angular izing the wound, muscle ; ¢, vertebro-mandibular muscle ; u, costo- man- and drinkin g large dibular muscle.—After Duvernoy. quantities (at least a pint) of whiskey or brandy, sufficient ordinarily to produce insensibility. Deaths from the bite of rattlesnakes are not common, while in India it is estimated that several thousand people annually die from the bite of the cobra—20,000 dying each year from the bite of snakes and the attacks of wild beasts. The ‘‘rattle” of the rattle- snake is a horny appendage formed of buttonlike compart- ments ; the sound made by the rattle, which has been com- pared by some to the stridulation of a Carolina locust, or of the Cicada, is an alarm note, warning the intruder ; the rat- tle is sprung before the snake strikes. Allied to this snake 500 ZOOLOGY. is the copperhead (Ancistrodon contortriz Linn.) and the black mocassin (Ancistrodon piscivorus Linn.). In the water snakes the tails are laterally compressed, while the poison- fangs are small. These snakes are not much over a metre in length, and live far from land in the East Indian seas. The poisonous snakes stand lowest in the series; they are succeeded by the striped snake, milk adder, and by the boas, which attain a length of five metres; while the anaconda grows eight metres long. In time snakes reach back to the Eocene Tertiary period, when a great sea-snake (7itanophis), represented by several species, one six metres in length, haunted the coast of New Jersey, while in the western lake-deposits of the same age, forms allied to the existing boa-constrictor were not un- common. The snakes, then, appear to be a modern type compared with the lizards, turtles, and crocodiles. Order 2. Pythonomorpha.—This group includes a num- ber of colossal serpent-like forms, with paddle-like feet, which are regarded by Cope as the types of a distinct order, char- acterized by a complex suspensorium, by the absence of a sternum and sacrum, by the rootless teeth, recurved parie- tal bones, etc. They were fifty and sixty feet in length, and Mosasaurus maximus Cope, from New Jersey was still more colossal. They combined characters of the snakes, lizards, and plesio- saurs, and correspond in a degree to the descriptions of the mythical sea-serpent. The resemblance to the Ophidians is still farther strength- ened by the late discovery by Professor F. H. Snow, that one of the forms (Liodon) was covered above by small imbricated scales, like those of the snakes, rather than large ones, like those of lizards. The more abundant type is the Jfosa- saurus of the Cretaceous seas, which was a huge sea-serpent originally referred by Cuvier and Owen to the neighborhood of the lace-lizards (Varanide) ; Cope describes it as a long slender reptile, with a pair of powerful paddles in front, a moderately long neck, and flat- pointed head, with a long forked tongue. The very long tail was flat and deep, like that of a great eel, forming a powerful propeller. The ORDER OF LIZARDS. 501 arches of the vertebral column interlocked more extensively than in other reptiles except the snakes. They swam rapidly ‘through the water by rapid undulations of their bodies aided by the paddles. The skull was not so strong, though as light as that of the serpents. ‘‘ While the jaws were longer, the gape was not so extensive as in serpents of the higher groups, for the os quadratum, the suspensor of the lower jaw, though equally movable and fastened to widely spread supports, was much shorter than in them. But there was a remarkable -arrangement to obviate any inconvenience arising from these points. While the branches of the under jaw had no natural ‘connection, and possessed independent motion, as in all ser- pents, they had the additional peculiarity, not known else- where among Vertebrates (except with snakes), of a movable articulation a little behind the middle of each. Its direction being oblique, the flexure was outwards and a little down- wards, greatly expanding the width of the space between them, and allowing their tips to close a little. A loose flexi- ‘ble pouch-like throat could then receive the entire prey swallowed between the branches of the jaw ; the necessity of holding it long in the teeth, or of passing it between the short quadrate bones could not exist. Of course the glottis and tongue would be forwards.” The order became extinct -before the Tertiary Period. Order 3. Lacertilia. —The existing lizards or Saurians are the survivors or descendants of a multitude of forms, many colossal in size, which characterized the Permian and Meso- zoic periods; while the extinct forms of reptiles were in many cases synthetic types, with affinities to fishes, Am- phibians, and even birds. The group as now existing is well circumscribed. Most lizards have cylindrical bodies, usually covered with ‘small overlapping scales, with a long, slender tail, and general- ly two pairs of feet, the toes long and slender, and ending in claws. They run with great rapidity, and are active, agile ‘creatures, adorned with bright metallic colors, in some cases green or brown, simulating the tints of the vegetation or .soil on which they live; some are capable of changing their color at will, as in the chameleon and Anolis; this is due to 502 ZOOLOGY. the fact that the pigment cells or chromatophores are under the influence of the voluntary nerves. While the scales of the body are developed, as a rule, from. the epidermis, in the scink there are dermal scales (scutes), and such dermal plates in the head may unite with the bones of the skull. In most lizards, all except the Geckos, the yertebre are procelous, 7.¢., with a ball-and-socket joint, the vertebree being rounded in front, and concave behind. In the Geckos the vertebral column is fish-like, the notochord persisting except in the centre of each vertebra, which is bi- concave. In many lizards (Lacerta, Jguana and the Geckos), the middle of each caudal vertebra has a thin cartilaginous partition, and it is at this point that the tails of these liz- ards break off so easily when seized. In such cases the tail is renewed, but is more stumpy. The tail of the specimen of Sceloporus (Fig. 440) which we dissected is much shorter than in the normal animal, and must have grown out after having been lost. The throat is often distensible by the hyoid apparatus ; but the bones of the jaws are firm, the bones united in front. Both jaws are provided with teeth, while some have them developed on the palatine and pterygoid bones. The teeth are usually simple, sharp, conical, as in most lizards, includ- ing the Monitor, or they are flattened, blade-like, with ser- rated edges, as in the Jywanda, or as in’ Cyclodus they are broad, adapted for crushing the food. Most lizards prey on insects ; some live on plants. New teeth are usually devel- oped at the bases of the old ones. They are attached to the surface of its jaws; in certain extinct forms (Thecodonts) they are lodged in sockets. (Huxley.) The eyelids are well developed except in the Geckos, in which the lids are modified somewhat, as in the snakes, to form a transparent skin over the cornea of the eves. The tongue is free and long, sometimes forked; in the iguana it ends in a horny point. While the limbs are usually present, one or the other pair may in rare cases (in Psewdopus the fore feet are wanting ; in Chirotes the hind feet are absent) be absent, or as in 4m- phisbena and its allies the feet are entirely wanting, though HORNED TOADS. 503 the shoulder-girdle invariably remains, the pelvic-girdle in such cases disappearing; the pelvis being complete, how- ever, when there are hind limbs. The feet are usually five- toed. The internal anatomy of lizards has already been de- scribed and illustrated on p. 493. In the snake-like lizards (Anguis) the left lung is the smaller, and in Acontias and Typhline it is almost wanting. A urinary bladder, wanting in the snakes, is present in lizards. The lizard lays eggs in the sand or soil; those of the iguana are deposited in the hollows of trees. Certain lizards are. viviparous. There are between seven hundred and eight hundred species of existing lizards, most of which inhabit tropical or subtrop- ical countries ; eighty-two species of lizards inhabit America north of Mexico. The earliest lizards date back to the Per- mian formation in Texas, and in Europe to the Jurassic rocks. Reviewing some of the more interesting lizards in the as- cending order, we may, passing over the snake-like, limbless Amphisbena, and the limbless glass snake (Opheosaurus), first consider the chameleon of the Mediterranean shores, in which the éyes are movable with a circular eyelid, and with the five toes in two opposable groups adapted for grasping twigs of trees. It is remarkable for its power of changing its colors. The tongue of the chameleon (Fig. 443) is capable of extending five or six inches, and is covered with a sticky secretion for the capture of insects, as the crea- ture itself is very sluggish. The chameleon of our country is the Anolis of the Southern States, and is a long smooth- bodied lizard, which can change its color from a bright pea- green to a deep bronze-brown. The horned toads (Phrynosoma) are characteristic of the dry western plains; the body is broad, flattened, and armed with spines ; its coloration depends on that of the soil it in- habits. It will stand long fasts) When Phrynosoma Dou- glassit of the Northwestern Territories and States is about to moult, small dry vesicles appear on the back and sides, run- ning aiong the horizontal rows of pyramidal scales forming the margin of the abdomen. In a day or two the vesicles break and desquamation begins, which continues for eight or d04L ZOOLOGY. ten days. the skin finally separating from the spines of the head and the claws. (Hoffman.) Our most common lizard in the Middle and Southern Srates is Sceloporus undulatus Harlan (Fig. 440). It 13 common, running up trees. The iguanas are very large lz- ards inhabiting the West Indies and Central America; the head i: protected by numerous small shields, with a dorsal row of bristling spines. They are about three feet long, live in the lower branche: of trees, and are said to be excellent eat- ing. © % Minet. wards, to reunite posteriorly just in front of the retractor muscles, their union forming the single median descending aorta; 3d. The pulmonary aorta (pa), which soon divides into a branch for each lung. The left aorta gives off a branch (d) which persists as a mere cord, the remnant of the ductus arteriosus, which originally united the aorta with the pulmonary artery. The right aorta gives off an ¢nnominate branch, that soon divides, and from each division springs 510 ZOOLOGY. the carotis (car). and subclavian artery of the same side. The veins are two in number, as they enter the heart: 1st. The pulmonary veins (pv) unite to form a very short trunk emptying into the left auricle; while (2d) the two rene cave superiores unite with the cara inferior (V) to empty through the sinus venosus into the right auricle. The kidneys lie at the posterior end of the body against the vertebral column. In the figure they are concealed by the bladder and oviducts. (Minot.) There are about forty species of Chelonians in America north of Mexico. The lower forms of turtles are the marine species. Such is the great ‘sea-turtle (Sphargis coriacea Gray) of the Atlantic and Mediterranean, which is the largest of all existing turtles. and is sometimes eight feet long, weighing from eight hundred to twelve hundred pounds. Next to this species is the loggerhead turtle (Thalassochelys ciouand Fitzinger), which is sometimes seen asleep in mid- ocean. Still another is the hawk-bill or torteise-shell turtle (Eretmochelys imbricata Fitz.), the plates of whose shell is an article of commerce. The green-turtle of the West Indies weighs from two hundred to three hundred eas and is used for making delicious soups and steaks : being caught at night when laying its eggs on sundy ce All the foregoing s species have lar ce, flat, broad flippers or fin-like limbs, while in the pond and river turtles the feet are webbed, and ie toes costings, ak very a dereetons Poa e the common coe is dover with a hick le oe cu, It i is earateerass. voracious. living in shallow muddy water. throwing itself forward upon small animals forming its prey. The snap- ping-turtle (Chelydra serpentina Schweigger) sometimes becomes four feet long; its ferocity is well known ; the flesh makes an excellent soup. The terrapins belong to the genus Pxeudemys ; the pretty painted turtle (CArysemys picta Agassiz) is common in the Eastern States. while the Vanemys guttatus (Agassiz), or spotted tortoise. is black, spotted with orange. In the land tortoises the feet are short and stumpy. The Testudo Indica of India is three feet in length. The great land tortoises of THE ICHTHYOSAURS. 511 the Galapagos Islands, the Mascarine Islands (Mauritius and Rodriguez), and also of the Aldabra Islands, lying northwest of Madagascar, are in some cases colossal in size, the shells being nearly two metres (six feet) in length. The fierce Mas- carine species were contemporaries of the dodo and solitaire, and are now extinct. The bones of extinct similar species have been found in Malta and in one of the West Indian islands. The land tortoises are long-lived and often reach a great age. Certain tortoises of the Tertiary Period, as the Colossochelys of the Himalayas had a shell twelve feet long and six feet high. The turtles extend back in geological time to the Jurassic, a species of Compsemys being char- acteristic of the Upper Jurassic beds of the Rocky Moun- tains. (Marsh.) The eggs of turtles, as those of birds, are of large size ; they are buried in June in the sand and left to be hatched by the warmth of the sun. It is probable that turtles do not lay eggs until eleven to thirteen years of age. The develop- ment of turtles is much as in the chick. By the time the heart becomes three-chambered, the vertebre develop as far as the root of the tail, and the eyes are completely enclosed in their orbits. The shield begins to develop as lateral folds along the sides of the body, the narrow ribs extending to the edge of the shield. In the lower forms of turtles (the Chelonioide), the paddle-like feet are formed by the bones of the toe becoming very long, while the web is hardened by the development of densely packed scales, so that the foot is nearly as rigid as the blade of an oar. Order 5. Rhynchocephalia.—The only living represeata- tive of this order is the Sphenodon or Hatteria of New Zea- land ; a lizard-like form of simpler structure, however, than the lizards in general. This rare creature somewhat re- sembles an iguana in appearance, having a dorsal row of spines. It is nearly a metre (32 inches) in length. In this group the vertebra are biconcave ; the quadrate bone is im- movable, and there are other important characters based on a study of the living and fossil forms, the latter represented by the Triassic Rhynchosanrus and Hyperodapedon. Order 6. Ichthyopterygia.—This order is entirely extinct. 512 ZOOLOGY. The Ichthyosaurs were colossal reptiles from two to thirteen metres (six to forty feet) in length, swimming in the ocean by four paddle-like limbs consisting of six rows of digital bones Fig. 448.—Skull of Jchthyosaurus ; lateral view. Pmz, premaxillary bone ; Mz; maxillary; V, nasal; Fr, frontal; Prf, prefrontal; Pos, postfrontal ; Pa, parietal J, lachrymal; M, malar; Qj, quadratojugal; Q, quadrate; Pob, postorbital; Sq squamosal; D, dentary; Ang,angular; Art, articular; S. 17, subarticular; Pler plerygoid.—After Cope. the head was very large, the neck very short, and the orbits were enormous; the vertebree were remarkably short and bi- concave. They were carniv- orous, and powerful swir- mers, and common in the Ju- rassic seas of Europe; one- form existed in the Jurassic times in Wyoming. Order %. Theromorpha.— This order is divided into the Pelycosauria and Anomo- dontia. The beaked Saurians were somewhat lizard-like, but Fig. 419.—Posterior view of the skull of were synthetic types. combin- Ichthyoxauris; lettering as in Fig 443, . witn following additions ; Bo, basioce- ing the characters of the Ich- pital; Hco, Exoccipital ; Sup. 0, supra- occipital ; Opo, opisthotic ; Stap, suprae throzaurs, the turtles, the stapedial or hyomandibular.—A fter Cope. é ® Z men TANT NOPS Sphenodon, with those of liz- ards, Dinosaurians, and crocodiles. The skull was short, and in Dicynodon the jaws in front had the nipping, horny beak of a turtle, while from behind in the upper jaw pro- truded two long, curved, canine teeth. Dicynodon tigriceps Owen, had a skull about half a metre (20 inches) long, THE PLESIOSAURS. 513: Another form was still more like the turtles, the jaws being toothless and enclosed in a nipping, horny beak. In Lys- trosaurus (Fig. 450) the head was blunt, the jaws armed in front with stout teeth, and behind with canine teeth; and these animals, anticipating in their dentition the lions and tigers, were called by Owen Theriodonts (beast-toothed). These forms lived during the Permian and Triassic times. Order 8. Sauropterygia.—The Plesiosaurus is the type Pif Som Vv Prom u Eetp Q— = Re Prax me s GS A Fa Subar Fig. 450.—Skull of Lystrosaurus frontosus from Cape Colony. Profile. Lettering as in Fig. 443 and 444, with the following additions: Etvom, ethmovomerine ; Sph, spheno d; pro, Prootic; Pter, Pterygoid ; Col, Columella: Hetp, Ectopterygoid ; * Subart, subarticular bone.—From Cope. of this extinct order. The Plesiosaurs were somewhat like the Ichthyosaurs, swimming by paddle-like feet, but the neck was very long, and the head rather small. The largest true Plesiosaur was about nine metres in length. They abounded during the Jurassic and Cretaceous period. During the lat- ter period off the coast of New Jersey and in the seas of Kansas flourished huge Plesiosaurian reptiles, such as Hlas- mosaurus, Which had an enormous compressed tail. The §14 ZOOLOGY. vertebre of E. platyurus Cope, of the New Jersey misl- beds, had vertebra nearly as large as those of an elephant, while the creature was whale-like in bulk, the neck long and flexible, the paddles short. The skull was light, with a long, narrow, very flat muzzle It must have been the ter- ror of those times; it was about fifteen metres (45 feet) in length. (Cope.) Order 9. Croeodilia.—The crocodile, caiman, gavial, and alligator are the types of this well-known group. They pre- sent a decided step in advance of other reptiles, the heart approaching that of birds, in having the ventricle completely divided by a septum into two chambers ; the venous and arte- rial blood mingle outside of the heart, not in it, as in the foregoing living orders. The brain is also more like that of birds, the cerebellum being broader than in the other rep- tiles. The nostrils are capable of closing, so that crocodiles and - alligators draw their prey under the water and hold them there until they are drown- ed; but they are Fig. 451.—Head of the Florida Crocodile.—after obliged to drag them HSSOAgEE ashore in order to eat them. Theskin is covered with horny, epidermal scales. The conical teeth are lodged in sockets in the jaws. The vertebrae are concave in front and convex behind, or the reverse : the quadrate bone is immovable. The feet are partly webbed. The crecodiles and gavials appeared during the Jurassic pe- riod, but the early forms were marine and like gamals. the head being long and narrow in front, with biconcave verte- bre. They lav from twenty to thirty cylindrical eggs in the sand on river banks. The crocodiles are distributed through- out the tropics. even Australia; the gavials are mostly con- fined to India and Malavsia, and also Australia. The group is represented in the Southern States by the alligator (4. Mississinpiensis Daudin). It is nearly four metres (10-12 feet) long; while the Florida crocodile (C. acutus Cuvier. DINOSAURIAN REPTILES. 515 Fig. 451) in which the jaws are much narrower, is over four and a half metres (14 feet) long. It inhabits the rivers of Florida where it is very rare, and also the West Indies and South America. The cayman of Guiana belongs to a dis- tinct genus, Caiman, and is characteristic of the rivers of tropical South America. Order 10. Dinosauria.—We now come to reptiles which have more decided affinities as regards their skeleton (the only parts preserved to us) to the birds, especially the os- triches, than any reptiles yet mentioned ; while the Dino- saurs were genuine reptiles, in the pelvis and hind limbs, including the feet, they approached the birds. This is seen especially in the ischium, which is long, slender, and inclined backwards as in birds. In the hind limbs the resemblance to birds is seen ; among other points, in the ascending pro- cess of the astragalus, in the position of the farther (distal) end of the fibula, and in their having only three functional toes. The fore limbs were shorter and smaller than the hind extremities, sometimes remarkably so. Moreover, the limb-bones, vertebre, and their processes were sometimes hollow; the sacrum consisted of four or five consolidated vertebra, in this respect anticipating the birds and mam- mals. They walked with a free step, like quadrupeds, instead of crawling like reptiles; some walked on the hind legs alone, making a three-toed footprint, occasionally putting down the forefoot, like the kangaroo. The lar- gest Dinosaurs were the /guanodon, which was from ten to sixteen metres (30-50 feet) in length, and the Cama- rasaurus (Atlantosaurus) which was about twenty-seven metres (80 feet) in length. The Cetiosaurus had a length of from twenty to twenty-three metres (60-70 feet). The Aw- drosaurus stood on its ponderous hind legs, with a stature of over eight metres (25 feet). These were bulky, inoffensive, herbivorous monsters, able to rise up on their hind feet and browse on the tops of trees; their undue increase was prevented by carnivorous forms like Ledaps, which was an active, possibly warm-blooded Dinosaur, with light, hollow bones, large claws, and serrate, conical teeth. It stood six metres (18 feet) high, and could leap a distance of ten metres through the air. (Cope.) 516 ZOOLOGY. Still nearer the birds was the Compsognathus; it was only two thirds of a meter (2 feet) long, with a light head, toothed jaws, and a very long, slender neck ; the hind limbs were very large and disposed as in birds, the femur being shorter than the tibia; moreover, the fore legs were very small. “It is impossible,” says Huxley, ‘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 extraordi- nary resemblance.” The so-called bird tracks of the Triassic rocks of the valley of the Connecticut were all reptilian footprints, and without doubt made by Dinosaurs with the above-mentioned affinities to the birds. These bird-like, colossal lizards appeared in the Jura-Trias Period, and be- came extinct in late Cretaceous times. Order 11. Pterosauria.—The forms of this order, rep- resented by the Pterodactyles, would lead one to infer that the group was still more bird-like than the Dinosaurs, and See- ley has shown that they have as many and important points of similarity to that class as the preceding group. They are a sort of reptilian bats, forming links between reptiles and flying birds, as the Dinosaurs connect with the ostriches, and it is in the hand and foot, which in birds are the most characteristically ornithic, that they resemble the ornithic type. They also approach birds in their long heads and necks, the jaws with or without teeth, the short tail, in the skull which is more rounded and bird-like than in other reptiles, with large orbits, as also in the form of the brain ; while the jaws were probably, in part at least. encased in horny beaks. The shoulder girdle was bird-like, and the sternum was keeled, but the pelvis and limbs were like those of lizards, while the fore-feet were much larger than the hinder ones, and the ulnar finger was enormously long and probably supported a broad membrane, connecting the fore and hind lhmbs, as in bats; moreover, the limb bones were hollow, and air-cells were present, so that these winged lizards could fly like birds or bats. The jaws of the Pterosaurs were completely toothed; those of the CLASSIFICATION OF REPTILES. 51? Rhamphorhynchus had teeth in the back of the jaw, the ends of the jaws being toothless and probably encased in horny beaks, while in Péeranodon the jaws were toothless. They were of different size, some expanding only as much as a sparrow, others with a spread of about nine metres (27 fect). They were contemporaries of the Dinosaurs, several forms, discovered by Marsh, occurring in the Cretaceous beds of Kansas, Cuass VI. REPTILIA. Air-breathing Vertebrates, with limbs usually ending in claws ; limbs -sometimes absent, rarely paddle-shuped ; body scaled ; ribs well developed ; heart in the highest forms four-chambered ; cold blooded ; an incomplete -double circulation ; oviparous ; eggs large; embryo with an amnion and allantois ; no metamorphosis. ‘Order 1. Ophidia.—Body long, cylindrical, usually limbless ; no shoul- der girdle. (Eutzenia.) -Order 2. Pythonomorpha.—Extinct, snake-like, limbs paddle-shaped. (Mosasaurus. ) -Order 3, Lacertilia.—Body with a long tail; usually fourlimbs; mouth not dilatable, the bones of the jaw being firm. (Scelepsrus.) ‘Order 4. Chelonia.—Body enclosed in a thick shell, within which the head and limbs can be withdrawn. (Testudo.) Order 5. Rhynchocephalia.—Lizard-like ; vertebrae bi-concave, species mostly extinct. (Sphenodon.) Order 6. Ichthyopterygia.—Head large, orbits large; limbs paddle- shaped ; extinct forms. (Ichthyosaurus.) “Order 7. Theromorpha.—Mammal-like saurians with solid pelvis and shoulder-girdle, and with canines, or toothless and beaked. (Dicynodon.) Order 8. Sauropterygia.—Extinct colossal saurians, with long necks, head of moderate size. (Elasmosaurus.) ‘Order 9, Crocodilia,—Thick- scaled; heart four-chambered. (Croco- dilus.) ‘Order 10. Dinosauria.—Colossal extinct saurians, capable of rising and resting on the hind legs, and making three-toed tracks, (Hadrosaurus. ) ‘Order 11, Pterosauria.—Extinct flying saurians, with the fore limbs large and a very long ulnar finger; toothed or toothless. (Pterodactylus.) 618 ZOOLOGY, Cuass VII, Aves (Birds), General Characters of Birds.—We have met in the rep- tiles, especially in the fossil forms, many characters indicat- ing that birds are by no means so specialized or so well circumscribed a group as was formerly supposed. Such a relationship between the two classes has recently been still further exhibited by Mever’s discovery of Arche@opteryx mac- rura Owen of the Solenhofen slates of the Jurassic beds of Germany, and by Marsh’s discovery of birds with teeth and biconcave vertebre in the Cretaceous rocks of North Ameri- ca. On account, therefore, of the close relations between birds and reptiles, Huxley has placed these two classes in a series called Sauvropsida, which may be opposed to the Jch- thyopsida (Fishes and Batrachians) on the one hand, and the Mammalia on the other, by the following characters :— Sauropsida.—There are no mammary glands. There is an amnion and an allantois; the species are oviparous or ovyoviviparous, with reproductive organs and digestive canal opening into a common cloaca, and Wolffian bodies replaced functicnally by permanent kidneys. There is no corpus callosum, nor complete diaphragm. Respiration is effected by lungs, never by gills. The heart is three or four cham- bered, and there ure usually two or three aortic arches; in birds but one; there are red oval nucleated blood corpuscles. The bodies of the vertebre are ossified, but without terminal epiphyses. There is a single convex, occipital condyle, in connection with an ossified basi-occipital, The ramus of the mandible consists of several pieces, the articular one of which is connected with the skull by a quadrate bone. The ankle-joint is between the proximal and distal divisions of the tarsus. The skin usually developes scales or feathers. These important characters. derived from Huxley (as are many of those given beyond for the class ves), may remind the student of the actual affinities between birds and rep- tiles. The former are distinguished from other Sewropsida by the following peculiarities :— -lves.—The body is covered with feathers, a kind of der- mal outgrowth found in no other ammals. The fore limbs STRUCTURE OF BIRDS. 519 form wings, serviceable in nearly all cases for flight. There are never more than three digits in the hand, two of them usually much reduced, and none of them bearing claws (with rare exceptions); nor more than two separate carpal bones in adult recent birds ; nor any separate interclavicle 5. the clavicles are normally complete, and coalesce to form a. “‘merry - thought.” The sternum is large, and usually keeled (the only exception among recent forms being the struthious birds); it ossifies from two to five or more centres, and the ribs are attached to its sides. The skull articulates: with the spinal column by a single median convex condyle, developed in connection with a large ossified basi-occipital. The lower jaw consists of several pieces, articulated by a quadrate bone to the skull, and in all recent birds both jaws are toothless and encased in a horny beak. The bodies of at least some of the vertebrae of recent birds have sub-cyclin- drical, articular faces ; when these faces are spheroidal, they are opisthoccelian, but some fossil forms are amphiccelian. The proper sacral vertebre have no expanded ribs abutting against the ilia. The ilia are greatly prolonged forwards ;. the acetabulum is aring, not a cup; the ischia and pubes. are prolonged backwards; there is no ischial symphysis ; there may be a prepubis; a process of the astragalus early anchyloses with the tibia. The incomplete fibula does not reach the ankle-joint ; there are not more than four digits, the normal numbers of phalanges of which are 2, 3, 4, 5. The 1st metatarsal is incomplete above; the 2d, 3d and 4th anchylose together, and with the distal tarsal bone unite to. form a tarso-metatarsus.* The heart is completely four-cham-- bered ; there is but one aortic arch (the right), and but one pulmonic ‘trunk from the right ventricle ; the blood is red and hot. The large lungs are not free in the cavity of the thorax, but fixed and moulded to the walls of that cavity : and in all recent birds the larger air-passages of the lungs. terminate in air-sacs. More or fewer of the bones are usually hollow, and permeable to air from the lungs. There is at most a rudimentary diaphragm. The eggs are very large, in consequence of a copious supply of albuminous substance, in the form of yolk and white, and are enclosed in a hard * This structure is Ciagnostic of birds. 20 ZOOLOGY. a) ik ber 1s eo ee 5 S i 28) \ BAN x \ x ‘ X = mer 3130 29 28 27 BH 9 UM intnes 46 45 44.43 42 414039 38 87 36 35 34 33 32 Fig. 452.—Topography of a bird. 1. forehead (frons\: 2. lore; 3, eIrcamocnular region ; 4, crown (verter): 5, eye: 6, hind head «ipvf.: 7. nupe (nuchy > 3. hind neck (cerriz); 9, side of neck ; 10, interscapular recion : 11, d-rswm or bick proper, including 10; 12, noteum. or upper part of body preper, including 10 11 and 13; 433, rump (uropyqium): 14, upper tail coverts; 15, tail: 16, under tail coverts : 14, tarsus: 18, abdomen: 19. hind toe (Aalur) 5 0. gostrevm, incud ng 18 and 24: 21. outer or fourth toe ; 22. middle or third toe; 23, side of the body : 24, breast « pertie); 25, primaries ; 26, secondaries ; 27, tertiaries. Nos. 25. 26. 27 are all vemdiness WB, primary coverts ; 29. ada, or bastard wing ; 30. greater cov 31. median coverts 5 32, lesser coverts : 33, the “throat,” including 34, 87 and 38: 34. juquluviy. or lower throat : 35, auriculars; 36, malar region: 37, gia or miidie throat; 38. mentum or chin: 39, angle of commissure. or corner of movth; 4. ramns of under man- dible : 41, side of under mandible : 42. gonys; 43. ap-r. or tip of bill; 44. ‘omia. or cutting edges of the bill; 45, e«dmen, or ridge of up inandible, corresponding to Srnyas 46, side of upper mandible; 47, nostril; 48, pas across the bill a litde in ront of its face.—From Coues’s Key. STRUCTURE OF BIRDS. b21 calcareous shell ; there is an amnion and allantois, and no metamorphosis after hatching. The external form of birds is very persistent ; the different parts of the body have been named in terms of continual use in descriptive ornithology. Hence, without entering into ‘details, we reproduce from Coues’s ‘“‘ Key” his figure of the topography of a bird. The student, after a careful study of the external form, should prepare a skeleton of the common fowl, or examine one already at hand, and observe those characters peculiar to birds. The skullis formed of bones consolidated into a more roomy ‘brain-box than in any reptiles, unless it be the Pterosaurians. In the parrots the beak of the upper jaw is articulated (Fig. -453, 7) to the skull, so that the movement of the beak on the skull is unusually free. The -quadrate bone (Fig. 453, e) is usually movable on the skull; and in the parrots when the mouth opens the upper jaw rises, since when the mandible is low- ered, the maxillo-jugal rod . | ie or bar (Fi g. 453, d) aan the maior’ ‘bone ensheathed ice premaxilla (22) upwards and eil chistier with Hore a mates forwards. This is a constant fea- ace oniotie 90716. on max : i: om o, lachrymal bone ; 7, nostril, show- ture in recent birds, the degree ing also the articulation of the naso- of motion which this peculiar Premantimy hone: ¢ quadrate bones mechanism allows being variable. Owen. The form of a bird’s vertebre is peculiar to the class ; the articulation of the body (centrum) in all the vertebre in front of the sacrum being saddle-shaped. ‘In Strigops and a few other land birds; in the penguins, the terns, and some other aquatic birds, one or more vertebre in the dor- sal region are without the saddle-shaped articulation, and are either opisthoccelian, or imperfectly biconcave.” (Marsh.) In the fossil Lchthyornis, which had a powerful flight, the vertebre are bi-concave, as in fishes, and Amphibians, and a few reptiles ; but the third cervical shows an approach to the saddle-vertebre of all other birds. The saddle form renders the articulation strong and free, and especially adapted to motion in a vertical planc. (Marsh.) 522 ZOOLOG ¥. While the sternum of the cassowaries and other struthious birds (Ratite) is smooth, approaching that of reptiles, that of the higher living birds is keeled or carinate (Fig. 454, ers); hence these birds are called Cari- nate ; to this keel and neighboring parts the muscles which raise and lower the wings are attached. The fore limbs of birds (Fig. 455) are greatly modified to form the framework of the wings. In spreading and closing the wings, the bones of the forearm slide along each other in a peculiar manner. (Coues.) The ulna is usually thicker and longer than the radius, and there are only two carpal bones, one radial, the other ulnar, in adult recent birds. The hand in the Apteryz and Fig. 454.—Sternmmm cassowaries has but one complete digit, ea fom a Gone ; while in other birds there are three digits, ton es Geen which probably correspond to the first, ir second, and third fingers of the human hand. The wings are attached to a strong shoulder-girdle, which consists of the two collar bones, uniting to form the wish-bone, and of acoracoid bone and scapula. Fig. 455.--Right wing bones of ayoung Chicken. A, shoulder; B, elbow; C, wrist or carpus; D, tip of third finger; @, humerus; 0, ulna; ¢, radius; d, scapholunar bone ; ¢, cuneiform bone; f,g, epiphyses of metacarpal bones /. k, respectively ; 2, metacarpal and its digit 1.—From Coues’s Key. The pelvis of birds is remarkable for the long slender back- wardly projecting ischium and pubic bones; there is generally STRUCTURE OF BIRDS. 523 mo bony union of the two pubic bones, nor do the ischia unite with the sacrum or each other, except in Rhea. In the ostrich, the pubic bones are solidly united. The hind limbs (Fig. 456) are two, three, or four toed, the ostrich having but two digits ; in most four-toed birds, one toe (the hallux) is directed backwards, while in the parrots and trogons, etc., there are two toes in front and two toes behind, and in the swifts and certain other forms all four toes are turned forwards. The bones of the skeleton are dense and hard; both the long bones and the bones of the skull are commonly hollow, containing air; the air-sacs, in connection with the lungs, communicating with the hollows of the bone. In some birds which fly well, only the skull-bones have air- cells, while in the ostrich which is unable to fly, the bones have even a greater number of cavities than the gull. The body during flight is thus greatly lightened, and the bird can sustain itself in the air for many hours in succession. With all these characters, the most re- markable and diagnostic external feature is the presence of feathers; no reptile on the ‘one hand, or mammal on the other, is clothed with feathers, though the scales on the legs and feet of birds are like those of reptiles, and it should be borne in mind that feathers are fundamentally modified scales or hairs. The ordinary feathers are called penne or contour feathers ; as they determine by their arrangement the outline of the body. They are, like hairs, developed in sacs in the skin ; Fig. 456.—-Hind limb of a Hawk, Buteo vulgaris. a, femur; 8, tibia ; 0’, fibula; c, tarso-met- atarsus; ¢’, the same piece isolated, and seen from in front ; dad’, a/’d/”, the four toes.—After Gegen- baur, the quill is hollow, partly imbedded in the derm ; this merges into the shaft, leaving the outgrowths on each side called dards, which send off secondary processes called darbules. These tertiary processes (called barbules and hooklets) are com- monly serrated, and end in little hooks by which the bar- ules interlock. Down is formed of feathers with soft. 524 free barbs, called plumules. ZOOLOG ¥. Over the tail-bone (coccyr) are usually sebaceous glands, which secrete an oil, used by the gti 2 Fig. 457.—Brain of the Hen. A, from above, B, from below; a, olfactory bulbs; 0. cere- bral hemispheres; ¢, optic lobes; d. cerebel- lum; d’, its lateral parts; ¢, medulla.—After Carus, from Gegenbaur. bird in oiling and dress- ing or ‘*preening” its feathers. In some birds, especially in the males of the gallinaceous fowls, as the cock and turkey, the head and neck are orna- mented with naked folds of the skin called ‘* combs” and *‘ wattles.” The brain is much iarger than in the reptiles, the cerebral hemispheres being greatly increased in size, while the cerebellum is transversely furrowed, and is so large as to cover the whole of the me- dulla. The alimentary tract consists of an cesophagus as long as the neck; it dilates in the domestic fowl and other seed-eating birds, as well as in the raptorial birds, into a lateral sac called the crop (in- gluvies). The stomach is di- vided into two parts, the first, the proventriculus, which is glandular, secreting a digest- ive fluid; and the second, which corresponds to the pylo- ric end of the stomach in the mammals, is round, with mus- cular walls, especially develop- ed in seed-eating birds, and called the ‘‘ gizzard.” In the fow] the gizzard is lined with a firm horny layer, by which BC neenr rrr Fig. 458—Thymus (¢h) and thyroid (d: glands of a young hawk, Buteo tulgaris- a Europe; fr, trachea.—After Gegen- aur. the food is crushed and comminuted, thus taking the place- of teeth. The intestine (including the large and small intes~ ANATOMY OF THE PIGEON. 525 tine) is long and ends in a cloaca, which receives the ends: of the urinary canals and oviducts. Attention should be given to the trachea ; its bronchial branches, the larynx and the syrinz or lower larynx, which may be developed either at the end of the trachea, or at the junction of the trachea and bronchi, or in the bronchi alone. The thymus gland (Fig. 458, ¢) is very large and long, while the thyroid (f) is a small, oval mass situated at the beginning of the bronchi. The following account and drawings of the anatomy of the pigeon have been prepared from original dissections by Dr. C. 8. Minot. As pigeons are one of the most readily obtainable and convenient types of birds, the following description of the anatomy of a male is given as illustrative of the class, those peculiarities being especially noticed by which birds are distinguished from reptiles and mammals. Before dissecting a bird, it must be carefully plucked ; this operation is much facilitated by dipping the animal in boiling water for a few minutes. The limbs and muscles of one, best of the left, side are to be removed ; the powerful pectoral muscles cut off close to their attachment to the keel of the breast-bone, and the ribs then cut away, care being taken to avoid injuring any of the internal organs, most of which will now be displayed im situ nearly as shown in Fig. 459, which represents a dissection carried somewhat further. The skin (Fig. 459, #, from the neck) is characterized by the presence of numerous ridges which cross one another, so as to enclose quadrilateral spaces; at the intersections of the ridges are small pits in which the feathers are in- serted. The digestive canal begins in the horny bill with three openings, one the large gape or mouth, and two oblique , elongated nasal clefts (m7), through which respiration is or- dinarily alone effected. It then extends backward under- neath the base of the skull, where it splits into the cesopha- gus and trachea, two large tubes which run down the front of the neck, the csophagus on the right and the trachea. on the left. Just below the head the trachea lies, in its normal position, in front of the esophagus, though in most 526 ZOOLOGY, adult birds both tubes follow a symmetrical course, but ex- hibit a mock or secondary symmetry with regard to each other. The origin of the two canals is embraced by the hyoidean apparatus, one of the horns (cormua) of which ap- pears at Hy; the Apparatus is too complicated to be de- scribed here; it closely resembles that of reptiles, and is functionally connected with the rapid thrusting out of the tongue. In some birds. as. for example, the woodpeckers and humming-birds, the horns are so developed as to curve round the back of the cranium on to the top of the skull. (Fig. 474). The trachea (77) is composed of cartilaginous rings with intervening membranes, and an external sheath of connect- ive tissue, which has been removed at Tr. It extends into the thorax, and is of nearly uniform diameter throughout, except at its lower extremity. where, as shown in Fig. 459, D, it forms an enlargement, the syrinx or vocal chamber (Z), found only in birds, but wanting in the ostrich. ete. (Ratite;, storks, and certain birds of prey. The trachea terminates immediately behind the svrinx in two smaller Dranches. the bronchi (8B), each of which passes into the Jung (Zu) of the same side. The cartilaginous rings of the bronchi are incomplete, the walls being partly formed by an elastic membrane. The rings of the trachea are pe- culiarly modified in the syrinx, which is furnished with ex- ternal muscles and internal membranous expansions, serving to produce the voice ; the muscles are the sterno-tracheal, furculo- or claviculo-tracheal, and the proper muscles of the syrinx. A true larynx is present in the upper part of the trachea, but is wunessential to the formation of the voice. The trachea presents flexuosities in various birds, usually more marked in the male than in the female ; in swans there is a great band which extends into the hollow breast-bone, but the object of this disposition is unknown. The lungs (Fig. 459, Zw) are two large sacs. placed dor- sally in the anterior part of the body-cavity. but not suspend- ed freely in a short thoracic sac nor enclosed in a pleura, as in mammals ; they are composed of reddish spongy tissues, and are attached between the ribs by connective tissue. ANATOMY OF THE PIGEON. 527 Each lung has upon its outer and dorsal surface five trans- verse depressions, corresponding to as many ribs. The bronchi and pulmonary blood-vessels enter together the anterior third of the lungs, and follow one another in their ramifications, but the bronchus traverses the lungs, giving off numerous branches, and opens into the abdominal air- ‘sac, while upon the surface of the lungs there are small ‘openings communicating with the remaining air-sacs. These structures the student had best tear through and ‘altogether neglect in his first dissection. The air-sacs are thin-walled bags, nine in number: three near the clavicle, four in the thorax, and two in the abdomen ; their ramifi- cations extend even into the bones, most of which are ac- cordingly found to be hollow. This striking organization is one of the most characteristic peculiarities of birds, and ‘serves to lighten the body by filling very large spaces with air, besides fulfilling certain other less obvious functions. In many chameleons and some Geckos the lungs have di- verticula or offshoots, which foreshadow the air-sacs of birds. The alimentary canal consists of seven parts: the cs- -ophagus, crop, glandular and muscular stomachs, large and small intestines, and cloaca. The cesophagus extends about three fifths of the way down the right side of the neck, and ‘is approximately of the same diameter as the trachea, with xegard to which, as before mentioned, it lies symmetrically. It opens into the crop (Cr), a thin-walled sac, which fills the triangular space between the base of the neck and the keel of the sternum, and forms a large part of the curved outline of the breast. In the specimen figured, the left half -of the crop has been removed to show the irregular folds upon the inner surface, the deep lateral pouch and the three posterior longitudinal folds of one side, which serve to guide the food onward to the stomach. As showr in Fig. 459, D, the crop (Cr) ends just to the right of and above the trachea, in a dorsally-placed, narrow tube, tnat Teaches to the origin of the bronchi, and there gradually ex- pands into the glandular stomach, which cannot, however, -be seen in a general dissection, while the heart, lungs, and 528 ZOOLOGY. liver are still im situ. The muscular stomach or gizzard (St) of the main figure is represented very large, being distended with food; it is sometimes found much con- tracted ; it is not sharply separated from the glandular stomach, the two being in reality only the greatly modified anterior and posterior divisions of the same dilatation. The opening of the glandular stomach and the origin of the small intestine are near together upon the anterior border of the gizzard. The walls of this last organ are remarkable for the enormous development of the muscular layers, especially in the graminivorous birds, under which pigeons. are to be included ; the muscles radiate on each side from. a central tendinous space. The small intestine has nu- merous coils, in the first of which lies the pancreas (Pav), very much asin mammals. The large intestine (#) is rel- atively short; its commencement is marked by two small. diverticula, distinctive of birds.* These appendages are- well developed in some species, as, for instance, the Galli- nacee, While in the bustard they have been described as. three feet long. Gegenbaur considers the cesophagus, crop, and stomach to be derived from the forc-gut, the small in- testine from the mid-gut, and the large intestine from the- hind-gut of the embryo. The cloaca (CZ) is th: short and. widened termination of the alimentary canal, and further receives four ducts, the two ureters (U7), and in the male the two vasa deferentia (Vd), in the female the two ovi- ducts. The digestive canal has two glandular appendages, the pancreas (Pan) and the liver (Zi); the former, as in birds generally, is quite large, whitish, and sends out a pro- longation, which extends to the spleen ; it has two ducts. The liver (Zz) is very voluminous, dark reddish brown in color, and forms two lobes, which rest upon the apex of the heart and the gizzard, and conceal the glandular stomach. There is no gall-bladder, a somewhat unusual feature among birds, but there are two bile-ducts, the larger and shorter * Some snakes have a single diverticulum, as is said to be the case with herons. ANATOMY OF THE PIGEON. 529 opening into the upper part, while the longer duct, after uniting with that of the pancreas, opens into the lower part of the duodenum. The length of the neck in birds is never less than the height at which the body is carried from the ground ; the number of vertebre entering into its formation varies from 9 to 24(swan) ; in the pigeon there are twelve, accompanied by a corresponding number of spinal nerves, the branches of which may be observed immediately underneath the skin. The main mass of the neck is composed of the vertebral col- umn and muscles, the trachea and esophagus. On either side of the base of the neck, in close proximity to the trachea and carotid artery, is a small oval white body, the thyroid gland (7’r), at first developed as an evagination of the fore- gut, but afterward becoming a closed and ductless sac, which is found in the majority of vertebrates, but the use of which to the organism is entirely unknown. Above the thy- roid lie the carotid artery and jugular vein, the main vas- cular trunks of the head and neck. The right jugular vein is usually the largest. Along the side of the neck, above the trachea on the left and the esophagus on the right, lies the elongated thymus gland (7m), drawn somewhat dia- grammatically ; this gland forms part of the lymphatic sys- tem, and in minute structure resembles the spleen. The heart (#/) lies immediately below the lungs and against the sternum, with its apex between the two lobes of the liver pointing obliquely downward and backward ; it is enclosed in a thin membranous bag, the pericardium, which is filled with serous fluid and attached to the roots of the main vascular trunks. To study the heart, it must be excised, taking the greatest care to leave as inuch as possible of the vessels, especially the large veins behind, in connec- tion with it. Viewed from behind (Fig. 459, C), the heart is seen to be composed of four chambers, the two anterior ones, the auricles, being the smaller. The left auricle receives upon its dorsal side the opening of the united pulmonary veins (Pv), one from each lung ; the right auricle is larger than the left, and receives in its upper portion the right vena cava superior (Vsd); in its lower portion the left vena 530 ZOOLOGY. cava superior (Vs), just above which opens the vena cava inferior (Vi). The two larger and posterior chambers, the ventricles, form the apex of the heart, and give off the arterial trunks. Of the ventricles, the left (Te. s) is the largest, has the thickest walls, and alone extends to the apex of the heart; it gives off the aorta, a short trunk which divides into a right and left branch, from which spring the carotid arteries for the head and neck, and which continue as the subclavian or auxiliary arteries 1 and .1’ for the wings. From the hase of the right branch .1 arises the large aorta (10), which turns around the bronchus of the same side, and runs to the front and right of the vertebral column through the abdomen; forming the descending aorta which gives off arteries to the intercostal and lumbar regions and to the viscera, and terminates in acrural branch to each leg. The right ventricle (Ven. d) has much thinner walls than the left; from it arises the pulmonary aorta (Pa) which soon branches to each side. Birds are distinguished from reptiles by having a four- chambered heart and a single permanent aortic trunk ; from mammals by the persistence of the right instead of the left aortic arch to form the aorta. Each auricle com- municates with the ventricle of the same side: the con- necting orifices are furnished with valves. The right auriculo-ventricular valve is muscular in all birds, while the left is membranous. The uro-genital organs lie dorsally in the hinder part of the body-cavity. The dark reddish brown kidneys (A?) consist, as in most birds, each of three lobes, the posterior being the largest ; they lhe immediately behind the lungs. The ureters (Ur) are slightly curved, whitish tubes, which pass back from the kidneys and open into the dorsal side of the cloaca. The testicles (Ze) are two large oval whitish bodies, each situated immediately behind the lung and be- low the kidney of the same side. The vasa deferentia (Vd) arise from the anterior and inner surfaces of the testicles, have a flexuous course, and, after forming terminal enlarge- ments, open separately into the cloaca, in front of the ANATOMY OF THE PIGEON. 531 ureters. In neither sex in birds are the genital ducts pro- vided with accessory glands. As usual among birds, the head is approximately top- shaped. ‘The eyes are very large and much exposed, as be- comes evident upon dissecting off the skin as in the figure. The external ear isa mere circular opening, entirely covered during life by the feathers. The side of the cranium may be removed soas to expose the brain, with the large smooth cerebral hemispheres (C’), the convoluted cerebellum (C2), and the much smaller medulla (Md). To study the brain satisfactorily, it must be removed from its case. A view of it from the side is given in Fig. 459, A, and a view from above in the same figure at B. The medulla oblongata (M) appears as hardly more than the enlarged upper end of the spinal cord ; upon its dorsal surface there is a trian- gular depression IV, the fourth ventricle, which is par- tially concealed by the cerebellum (Cb), a large mass mark- ed by transverse ridges and imperfectly divided into three lobes, thus exhibiting, both in its size and its complication of structure, a great advance over the reptiles. The corpora quadrigemina or bigemina* (Q) project as two large lobes far out on the sides and down the base of the brain ; their posi- tion and great size are characteristic for the whole class. The optic thalamt, which intervene between the bigemina and the hemispheres, are relatively small ; they enclose the third ventricle and have a funnel-shaped downward exten- sion, to which the pituitary body is attached, as to a stalk. The cerebral hemispheres (He) form more than half of the whole brain ; their surfaces are entirely without convolu- tions, but each hemisphere has a small projection, the olfac- tory lobe (02), upon its anterior and inferior extremity. The cavities of the hemispheres or the lateral ventricles are very large and extend also into the olfactory lobes. The greatly thickened inferior walls of the hemispheres are termed the corpora striata. Birds differ from mammals in having only a rudimentary forniz and no corpus calloswin. The description of the cranial nerves is purposely omitted. * Also called the optic lobes, middle brain, and mesencephalon. 532 ZOOLOGY. Between the liver and the glandular stomacli lies the small, somewhat elongated, reddish brown spleen. In birds, as in most vertebrates, several spinal nerves unite to form a brachial plexus, part of which is shown at B, and which supplies the wings. Posteriorly, there is also formed a plexus, the lumbar, for the legs. The muscles of the limbs are much modified in accordance with the peculiar locomotion of birds. In connection with the power of flight, the sternum has a very large keel, to which are attached the pectoral muscles. The pectoralis major (Pe) is the most external ; it arises from the outer half of the keel and is inserted into the humerus, and effects the downward stroke of the wing. The second pectoral (pectoralis tertius of some authors and the homologue of the comparatively insignificant subclavius of human anat- omy) arises from the inner portion of the keel, runs forward and outward, and, tapering off, passes through a groove be- tween the coracoid and sternum, as over a pulley. to be in- serted into the humerus. The wing is raised by its action. In the ostrich, etc. (Ratite), the breast-bone has no keel, and the disposition of the muscles of the rudimentary wings therefore differs greatly from that here described. (Muinot.) The ovary may be distinguished hy the large incipient eggs forming the greater part of the mass. The right ovary is usually undeveloped, but when partly formed, as in some hawks, the eggs do not mature. The *‘ white”’ is deposited around the true egg in the upper part of the oviduct, while the shell is secreted from glands emptying into the lower part of the duct. The eggs of birds are enormous in proportion to those of other verte- brate animals, except the lizards. The egg of the .£pyornis, an extinct bird of Madagascar, is about a third of a metre (134 inches) in length, and as the egg is in reality a cell, this is the largest cell known. The development of the chick is better known than that of any other animal. It travels the same developmental path as other vertebrates in which an amnion and allantois are formed. About the sixth day of embryonic life the bird-characters begin to appear, the wings begin to differ from the legs, the crop and giz- 533 ANATOMY OF THE PIGEON. Fig. 459.—A natomy of the Pigeon, X KY W N NGS NK VA IN ANN AW ESIVy ARES CSS SSS He SRS A, B, brain; C, heart; D, syrinx and bronchi; E, skin.—Drawn by ©. 8. Minot. 534 ZOOLOGY. zard are indicated, and the beak begins to develop. By the ninth or tenth day the feathers originate in sacs in the skin, these sacs by the eleventh day appearing to the naked eye as feathers; the claws and scales of the legs and toes are marked out on the thirteenth day, and by this time the cartilaginous skeleton is completed, though the deposition of lime (ossification) begins on the eighth or ninth day by small deposits of bone in the shoulder-blade and limb-bones ; centres of ossification appearing in the head by the thir- teenth day. ‘* After the sixth day, muscular movements of the embryo probably begin, but they are slight until the fourteenth day, when the embryo chick changes its position, lying length- ways in the egg, with its beak touching the chorion and shell membrane, where they form the inner wall of the rapidly increasing air-chamber at the broad end. On the twentieth day or thereabouts, the beak is thrust through these membranes, and the bird begins to breathe the air contained in the chamber. Thereupon the pulmonary cir- culation becomes functionally active, and at the same time blood ceases to flow through the umbilical arteries. The allantois shrivels up, the umbilicus becomes completely closed, and the chick, piercing the shell at the broad end of the egg with repeated blows of its beak, casts off the dried remains of allantois, amnion, and chorion, and steps out into the world.”’ (Foster and Balfour.) Some young birds have, as in turtles and snakes, a tem- porary horny knob on the upper jaw, used to crack the shell before hatching. In birds which lay small eggs, with a comparatively small yolk, the young are brooded in nests and fed by the parent ; but in the hen and other gallina- ceous birds, in the wading birds and many swimmers, as ducks, where the yolk is more abundant, the young main- tain themselves directly on hatching. Following the business of reproduction is the process of moulting the old and weather-beaten feathers. This is often a critical period in a bird’s life. judging by the occasional mortality among domesticated and pet birds. The annual moulting begins at the close of the breeding season, though SONGS OF BIRDS. 535 some birds moult twice and thrice. The quill-feathers (rem- iges) are usually shed in pairs, but in the ducks (Anatide) they are shed at once, so that these birds do not at this time go on the wing, while the males put off the highly- colored plumage of the days of their courtship, and as- sume for several weeks a dull attire. In the ptarmigan both sexes not only moult after the breeding season is over into a gray suit, and then don a white winter suit, but also wear a third dress in the spring. In the northern hemisphere the males of many birds put on in spring bright, gay colors. Other parts are also shed ; for example, the thin, horny crests on the beak of a western pelican (Peli- canus erythrorhynchus), after the breeding season, are shed like the horns from the head of deer. Even the whole covering of the beak and other horny parts, like those about the eyes of the puffin, may also be regularly shed. The variations in the frequency, duration, and completeness of the process are endless. As a rule, male birds are larger and have brighter col- ors, with larger and more showy combs and wattles than the females, as seen in the domestic cock and hen; and the ornamentation is largely confined to the head and the tail, as seen especially in male humming-birds. Mr. Darwin has: adduced a multitude of examples in his Descent of Man, Vol. 2. Sometimes, however, both sexes are equally orna- mented, and in rare cases the female is more highly colored than the male; she is sometimes also larger, as in most birds of prey. There is little doubt that the bright colors of male birds render them more conspicuous and to be more readily chosen by the females as mates, for in birds, as in higher animals, the female may show a preference for or antipathy against certain males. Indeed, as Darwin remarks, when- ever the sexes of birds differ in beauty, in the power of sing- ing, or in producing what he calls ‘* instrumental music,’ it is almost invariably the male which excels the female. The songs of birds are doubtless in part sexual calls or love-notes, though birds also sing for pleasure. The notes of birds express their emotions of joy or alarm, and in some cases at least the notes of birds seem to convey intelligence. 536 ZOOLOGY. of the discovery of food to their young or their mates. They have an ear for music ; some species, as the mocking-bird, will imitate the notes of other birds. The songs of birds ean be set to music. Mr. X. Clark has published in the almerican Naturalist (Vol. 18, p. 21) the songs of a number of our birds. The singular antics, dances, mid-air evolu- tions, struts, and posturings of different birds, are without doubt the visible signs of emotions which in other birds find vent in vocal music. The nesting habits of birds are varied. Many birds, as the gulls, auks, etc., drop their eggs on bare ground or rocks ; as extremes in the series are the elaborate nests of the tailor-bird, and the hanging nest of the Baltimore oriole, while the woodpecker excavates holes in dead trees. Asa rule, birds build their nests concealed from sight ; in tropi- cal forests they hang them, in some cases, out of reach of pred- atory monkeys and reptiles. Birds may change their nesting habits sufficiently to prove that they have enough reasoning powers to meet the exigencies of their life. Parasitic birds, like the cuckoo and cow-birds, lay their eggs by stealth in the nest: of other birds. The duties of incubation are, as a rule, performed by the female, but in most Passerine birds and certain species of other groups, the males divide the work with the females, and in the ostrich and other Ratite the labor is mostly per- formed by the males. There are probably from 7000 to 8000 species of living birds ; Gray's ‘‘ Handlist ’? enumerates 11,162, but many of these are not good species. Of the whole number, about 700 distinct species or well-marked geographical races in- habit Notth America north of Mexico. The geographical distribution of birds is somewhat complicated by their mi- grations. While the larger number of species are tropical, arctic birds are abundant, though most of them are aquatic. In the United States there are three centres of distribution : (1) the Atlantic States and Mississippi Valley; (2) the Rocky Mountain plateau, and (3) the Pacific coast. The migrations of birds will be treated of near the close of this volume. FOSSIL BIRDS. 537 While in former times existing birds were divided into a large number of ‘‘ orders,” these are now known to be sub- divisions of the two sub-classes Ratite and Carinate, and probably in many cases should be honored only with the rank of sub-orders. The discovery of the Archwopteryx and of birds with teeth and biconcave vertebre has essentially mod- ified prevailing views as to the classification of birds. Sub-class 1, Saurure.—The oldest bird, geologically speaking, is the Archwopteryx (Fig. 460) of the Jurassic slates of Solenhofen, Germany. This was a bird about the size of a crow, the tail being 22 cent. (8-9 inches) long, but longer than the body, supported by many movable vertebrae Fig. 460.—Restoration of Archaopteryx macrura.—After Owen, from Nicholson. ‘and covered with feathers in distichous series, not in the shape of a fan. The jaw-bones were long, and contained conical teeth. The head, shoulder girdle, and fore limbs, with their three digits, were reptilian in form. (Vogt.) In these respects and in the long tail the creature served as a connecting link between the reptiles, such as the bird-like Compsognathus,and the existing birds. The hind legs and wings have the ordinary bird structure, though the metacar- pal bones were not co-ossified; the foot consisted of three digits. Sub-class 2. Odontornithes.—Still another connecting link between the reptiles and birds has been discovered by Marsh 538 ZOOLOGY. in the upper Cretaceous beds of this country. The remains of Ichthyornis indicate an aquatic bird about the size of a pigeon. The reptilian affinities are seen in the vertebre, which, unlike those of all other birds, are biconcave, and in the long, slender jaws, with stout, conical teeth held in sockets, as in the crocodiles. On the other hand, the wings were well developed, and the lezs were of the ordinary bird type, the metacarpal bones being co-ossified, while the ster- num was keeled. In asecond member of the group (Hes- perornis) the teeth were in grooves, the vertebre as in recent birds, the sternum without a keel, and the wings were rudi- mentary (Marsh). Sub-class 3. Ratit@.—This group. represented by the kiwi- kiwi, the moa, cassowary, and ostrich, is characterized by the smooth unkeeled sternum and the short tail; the wings are rudimentary and the hind legs strong, these birds (except Apteryz) being runners, and either of iarge or, as in the extinct forms, of colossal size. The simplest form is the ‘‘ kiwi-kiwi,’’ or Apteryx of New Zealand (Fig. 461), of which there are three or four species. It is of the size of a hen, witha long slender beak, the nostrils situated at the end of the upper jaw, while the body is covered with long hairy feathers. The female lays only a single large egg, which weighs one quarter as much as the bird itself, in a hole in the ground. It is a night bird, hiding by day under trees. The giant, ostrich-like, extinct birds of New Zealand, called moa, and represented by several species, chiefly of the genera Dinornais and Palapteryz (Fig. 461), were sup- posed to have been contemporaries of the Maoris or natives of New Zealand. While a fourth toe (halluz) is present in the .{pteryzx, the moa-bird has only three toes. The largest of the moas, Dinornits giganteus of Owen, stood nearly three metres (94 feet) in height, the tibia or shin-bone alone measuring nearly a metre (2 feet 10 inches) in length. These moa birds belong to three genera: Di- nornis with ten, Palapteryx with three, and Apftornis with a single species. Allied to the moa was a still larger bird, the Zpyornis CURSORIAL BIRDS. 539 maximus, of Madagascar, supposed by some to be the roc of the Arabian Nights’ Tales. Of this colossal bird, remains of the skull, some vertebra, and a tibia 64 cent. long, have been found. The single egg discovered is of the capacity of one hundred and fifty hens’ eggs. To this order belong the three-toed cassowaries of the East Indies and Australia, and the emeu of Australia ; both Fig. 461.—Moa, Palapteryx, with three Kiwi-kiwi birds.—After Hochstetter, from Tenney’s Zoology. of these birds are about 2 metres (5-7 fect) high. The South American ostrich (Rhea Americana) with three toes to each foot, is a smaller bird, standing 1-3 metres high, run- ning in small herds on the pampas. The two-toed ostrich (Struthio camelus Linn.), of the deserts of Africa and Arabia, now reared for the feathers of its wings and tail, so 540 ZOOLOGY. valuable as articles of commerce, is the largest bird now liv- ing, being 2-2-7 metres (6-8 feet) high. It can outrun a horse, and lives in flocks. It lays about thirty large white eggs in a nest in the sand; they are covered in the day- time by the hen or left exposed to the sun, while at night the male sits over and guards them. In Cape Colony, os- trich-culture has become an important business; in 1865 Fig. 462.—Great Auk.—From Coues’ Key. there were only eighty individuals on the ostrich farms ; in 1875 there were 32,247 ostriches, either free or in parks where Lucerne grass is cultivated as food for these useful birds. The South American ostrich is in Patagonia hunted for its feathers. During the Eocene Tertiary period a gi- gantic ostrich-like bird (Diatryma Cope), twice as large as DIVING BIRDS. 541 an ostrich, lived in Texas and New Mexico, part of a leg- bone having been found on the San Juan River. Sub-cluss 4. Carinate.—All other living birds belong to this group; they are remarkably homogeneous in form and structure, and the subdivisions may be regarded as orders. They are characterized by the keeled breast-bone or sternum—the wings, as a rule, being well developed. The diving birds (Pygopodes) are eminent as swimmers, and comprise the penguins, auks, puffins, grebes, and loons. The penguins are confined to the antarctic regions. They are large birds, and form a characteristic element in a Pata- gonian landscape. The bones are solid, not light and hol- low, as in other birds; the wings are small, paddle-like, with scale-like feathers; on shore they have an awkward gait. They lay but a single egg, and some species do not lay their egg on the rocks, but bear it about in a pouch- like abdominal fold. The penguins, however, differ so much from the other divers that they are now often ranked as a separate group of this grade, called Sphenisct. The guillemots and auks are characteristic arctic birds ranging from Labrador northward, and have great powers of flight. The gare fowl, or great auk (Alca impennis, Fig. 462), is nearly or quite extinct, being un- til lately confined to one or two inaccessible islets near Iceland, where it has been extinct since 1844, and to Labrador, though formerly it ranged from Cape Cod northward, a few survivors having lived on the Funks, an islet on the eastern coast of New- foundland, within perhaps thirty years. The loons are well known for Fig. 463.—Roseate Tern —From their large size and quickness in Te” 7001927 diving. They are migratory, laying two or three eggs in rushes near the water’s edge. The petrels, gulls, and terns (Fig. 463, roseate tern) rep- 542 ZOOLOGY. resent the group of long-winged swimmers (Longipennes). They have long, slender, compressed bills, long, sharp wings, immense powers of flight, and lay their eggs in rude nests on rocks or upon the ground. The most notable member of the group is the albatross (Diomedea exulans) of tne South- ern hemisphere. Its wings expand more than three metres (nearly ten feet). It lays a single egg 12 cm. long, and spends most of its life on the ocean far away from land. The sooty albatross (D. fuliginosa Lawrence, Fig. 464), is occasionally seen on our coast. Fig. 464.—Svoty Albatross.—From Tenney's Zoology. These birds are succeeded in the ascending series by the tropic-bird, frigate or man-of-war bird, the darter or snake- bird, the cormorants. pelicans, and gannets (Steqanopares), in which all four toes are fully webbed. the web reaching to the tips of the toes. The body, especially in the pelicans and gannets, is buoyed up more than in other birds by a large number of much subdivided air-cells under the subcutane- ous areolar tissue of the body. The pelican is remarkable for the large, loose pouch on the under jaw, capable of holding several quarts, or several SWIMMING BIRDS. 543 hundred small fishes. In the Hast Indies, pelicans are ‘tamed and used by the natives in fishing, as isthe cormorant in China, while in early times it was in England. The ducks and geese (Lamellirostres) have usually broad bills furnished with lamellate, teeth-like projections. The feet are palmated, adapted for swimming rapidly. In the mergansers the bill is narrow and more strongly toothed. The eider duck (Sommateria mollissima) which breeds from Labrador around northward to Scotland, plucks its down from its breast, building with it a large warm nest under low bushes on the sea-coast, where it lays three or four pale Fig. 465.—Summer Duck.—From Tenney’s Zoology. dull green eggs. The canvas-back (Fuligula vallisneria) feeds, as its specific name implies, on the wild celery ( Vai- lisneria) on the middle Atlantic coast in winter, whence it derives its delicious flavor. The summer duck (A1% sponsa, Fig. 465) breeds in trees. The original source of our do- mestic duck is the mallard, or Anas boschas. It is known to cross with various other species. Upward of fifty kinds of hybrid ducks are recorded, some of which have proved to be fertile (Coues). The black duck (Anas obscura) is abundant on the shores of Northeastern America, and is fre- 544 ZOOLOGY. quently brought into the market. The wild goose (Branta Canadensis) breeds in the North- ern United States and in British. America. While it usually breeds. on the shores of rivers, it has. been known in Colorado and Montana to nest in trees. Allied to it is the barnacle goose of Europe (Branta leucopsis), which very rarely occurs in this coun- Fig. 466.—Carolina Rail.—From try, The swans are characterized Rennes aoolets by their long necks, the trachea or wind-pipe being remarkably long, especially in the trum- peter swan, where it enters a cavity in the breast-bone, makes a turn and centers the lungs, after forming a large coil. To this group, or next to it, also belong the flamingoes, the American flamingo (Phenicopterus ruber) occur- ring on the Florida and Gulf coast. Its feathers are scarlet, its bill yellow, large and thick, while the legs and neck are of great length. It connects the swimming with the wading birds. The foregoing group forms a division called the Natatores or - swimming birds. We now come to the Gralla- tores or wading birds, which have long, naked legs, and therefore long necks, with usually remarkably long bills. They are divided into cranes, rails, etc. (Alectorides), the herons and their allies (Herodiones), and the shore-birds, snipes and plovers, or Limicole. The cranes, together with rails (Por- sana Carolina, Fig. 466) sometimes have lobate feet, the toes are often long, and in some forms, such as the coots and gallinules, there is an approach to the ducks. Fig. 467.—The * Giant” of Mauritius.—After Schiegel, WADING BIRDS. 545 Allied to the gallinules is the ‘ giant’ or Gallinula (Le- guatia) gigantea of Schlegel (Fig. 467), which formerly lived in the Mascarene Islands, having been observed as late as 1694. Itstood two metres (over six feet) high. With it was associated a large blue galli- nule—Porphyrio (Notornis ?) ceruiescens Selys—which was last seen on the Isle Bourbon between 1669 and 1672. It was incapable of flight, but ran with exceeding swiftness. The cranes are of great at stature, the legs and neck very eo. ie eens es Curlew.—From Jong, with the head sometimes curiously tufted. With the true herons are associated the night herons and the bitterns of the United States, the boat-billed heron of Central Am- erica, and the odd Baleniceps rex of Africa, which has an enormous head and broad, large bill. The herons are suc- ceeded by the singular spoon-bills represented by the rose- ate spoon-bill, and which, with the wood Ibis and other species of this group, adorn the swamps and bayous of the South Atlan- tic and Gulf States. The shore-birds, or the cur- lews (Numenius longirostris, Fig. 468), piover, sandpipes, peeps, snipes (Gallinago Wil- sonit, Fig. 469), woodcock, and stilt (Himantopus nigricollis, Fig. 470), are long-legged, long- billed birds, going in flocks by the seashore or river-banks, Fig. 469—American Snipe.—From sometimes living inland on low Temney’s 4eclogy- plains ; they are not, generally speaking, nest-builders, the eggs being laid in rude nests or hollows in the ground. They feed on worms, insects, and snails, either picking them up from the surface or boring for them in the mud or 546 ZOOLOGY. sand, or forcing the vermian food out of tneir holes by stamping on the ground. Connecting in some degree the waders and gallinaceous fow] are the bustards of the Old World, certain strange exotic birds, especially the horned screamers represented by a very rare bird, the Pala- medea cornuta Linn., which has sharp horns on the wings. The form of the gallina- ceous birds, formerly called Rasores, from their peculiar habit of scratching the ground for food, is readily recalled by a simple enumeration of the partridge, Oreortyx (0. pictus, Fig. 471), quail (Ortyx), ptarmigan (Lagopus, Fig. 472), pinnated grouse or prairie hen (Cupidonia cupido), sage-cock, Canada grouse or spruce partridge (Te- trao), and wild turkey (Meleagris), as well as the exotic forms, the pheasant of the Old World, the use- ful hen or barn-yard fowl, which is a descendant of Gallus Bankiva Tem- minck, of India. These are alliedtothe argus-pheasant and the peacock, the latter rivalling the humming- birds in its gorgeous plum- age. The guinea-hen is an African bird. To this Fig. 470.—Stilt.—From Tenney’s Zoology. : Fig. 471,-Plumed Partridge.—From Ten- group belongs the curious ney's Zoology. eye mound-bird (.Vegapodius), of Australia and New Guinea. It heaps up a large mass of GALLINACEOUS BIRDS. 547 rubbish, forming a hot-bed, in which its eggs arv left to hatch. The megapods, together with the Americaa guans and curassows (Cracide), form a sort of passage from the gallinaceous to the columbine birds. One of the most puz- zling forms for the systematic ornithologist to deal with is the hoasin of Guiana (Opisthocomus cristatus Iliger). in this bird the keel of the breast-bone is cut away in front, the wish-bone unites A with the coracoid bones, and also with the manubrium of the breast-bone, a thing of rare occurrence (Coues). In the tinamous of Central and South America the tail-feathers are, in some cases, entirely wanting, and the breast- bone and skull-bones have some anom- alous features. Most all gallinaceous birds have plump bodies, with short beaks and small rounded wings, not being good fliers. In some of their cranial characters they are so peculiar that Huxley makes them one of his « primary divisions — of Carinate. ‘ We now come to SEG birds ‘at 2 higher Fig. 472.—White-tailed Ptarmigan (Lagopus leucurus), type, in which the in (upper figure) summer and (ower figure) winter eo. and par fae plumage.—From Hayden’s Survey. the thigh are free from the body, the leg being usually feathered down to the tibio-tarsal joint ; the toes are usually on the same level, being fitted for grasping or perching. The doves are rapid fliers, but a notable exception is seen in their extinct ally the Dodo (Didus ineptus Linn.) of Mauritius, which became extinct on theisland of Mauritius in the seventeenth century, while the solitaire, Didus (Pe- S 548 ZOOLOGY. zophaps) solitarius Schlegel, inhabited the island of Ro- Griguez, having been exterminated about the same date (1681). These were clumsy, defenceless birds, incapable of fiight, and were destroyed by the domestic animals which accompanied the Portuguese voyagers to the Mascarene islands. The doves and their allies now commonly form a group, salled Calumbe. The birds of prey (Raptores), comprising the vultures, buzzards, falcons, hawks, eagles, and nocturnal owls, have a hooked and cered beak—z.e., with a waxy, dense mem- brane situated at the base of the upper mandible. The claws are large and sharp. The raptorial birds live either on birds and mammals, or fish, reptiles, batrachians, and insects. Of the vultures, the most notable for size is the condor of the Andes (Sarcorhampus gryphus), which has great powers of flight, its wings expanding nearly three metres (nine feet). The carrion crow and turkey buzzard (Cathartes atratus and C. aura Mlig.) are useful as scavengers, especially the former, which is vartiy domesticated in southern cities and towns ; they nest on the ground or in stumps, and are more or less social. The hald-headed eagle (Haliaétus leucocepha- lus) is dark-brown when young, and lefore shedding its youthful plumage is larger than the white-headed adult. It nests on inaccessible rocky points ; is the sworn enemy of the fish-hawk, and, like it, fond of fish, often wresting its living food from the talons of the hawk. This species is the emblem of our country. The osprey or fish-hawk (Pandion haliaétus) is two-thirds of a metre long, nests in tall trees, and is migratory. Among the hawks, the most notable are the falcons or hunting hawks, used during the Middle Ages in hunting the hare, ete.; in nature they chase their prey and kill it immediately, devouring it, and rejecting the bones and hair of the partly digested food in a ball from the mouth. The owl is a bird of the night ; its flight is noiseless, ow- ing to its soft plumage, the feathers having no after-shaft. It has large eyes and a hooked bill, giving the bird of Mi- nerva an air of consummate wisdom. Owls capture living BIRDS OF PREY. °° 549 mice and other small nocturnal animals, ejecting from the mouth a ball of the indigestible portions of their meal. The little burrowing owl of the western plains (Spheotyto cunicularia, var. hypogea) consorts with the prairie dogs and rattlesnakes, nesting in the holes when deserted. ‘Their rusty, dull hues assimilate them with the color of the soil they inhabit. Our largest owl is the great gray owl (Syr- nium cinereum) ; it isnearly ? metre (24 feet) in length, and Fig. 473.—Carolina Parroquet.—From Tenney’s Zoology. ‘is an inhabitant of Arctic America. A visitor in winter rom the Arctic regions is the snowy owl (Nyctea nivea), which is nearly 3 m., or two feet long. The great horned owl (Budo Virginianus) is about the same size as the snowy owl, but has two conspicuous ear-tufts, adding to its height and its general impressiveness as a bird of more than ordi- ‘nary sagacity. Of more intelligence and gifted with the power of speech 550 ZOOLOGY. are the parrots (Psittaci). The tongue is large, soft, and remarkably mobile, as the muscles at the base are more dis- tinctly developed than in other birds, and the lower larynx is complicated with three pairs of muscles; hence these birds are wonderful mimickers of the human voice, imi- tating the laughter or crying of babies, and repeating brief sentences, while some sing. In proportion to their capacity for talking, parrots command a very high market price. Their toes are in pairs, the bill is cered and very stout, adapted for cracking hard nuts. The wish-bone is sometimes rudimentary, and the sternum entire, uot notched. Parrots are monogamous, like the hawks, and nest in rocks or hollow trees. Our only parrot is the Carolina parroquet (Conurus Carolinensis Kuhl, Fig. 473), which is common in Florida. It for- merly extended to the Great Lakes and to New York, but is nearly exterminated. About three hundred and fifty species are scattered through tropical countries, Australia and South America being es- pecially favored by these gorgeous birds. The ground parrot of New Zealand does. not fly, all the others being good fliers. Fig. 474 —Skull of Ge- Parrots live to the age of eighty years. cinus viridis L., showing 5 a < the asymmetrical position The Picarie, « somewhat miscella- pray andl thee orreaon neous group of birds, comprising the through ne eu ofike Woodpeckers, the cuckoos, and allies, Sacer ey Taman, 2nd the swifts and humming-birds, con- nect the preceding groups with the Pas-. serine or singing birds. From the latter the Picarie com- monly differ in the form of the sternum, in the less developed vocal apparatus, there being no more than three pairs of separate muscles, so that the birds are not musical ; as well as in the nature of the toes and wing and tail feathers. The woodpeckers usually have pointed, stiff tail-feathers,. PERCHING BIRDS. 581 and the bill is straight and strong. The tongue is long, flat, horny, and barbed at the end, and can be usually darted out with great force, so that the bird can make holes in the bark of trees and draw out the larve of insects boring under the bark ; im tnis way these birds render us signal service. The tongue, as in all vertebrates, is supported by the hyoid apparatus, especially by two cartilaginous appendages to the hyoid bone, called ‘‘ the horns.’’ These in the woodpeckers, when fully developed, are curved into wide arches, each horn making a loop down the neck, and thence bending upward, sliding around the skull, and even down on the forehead. Through a peculiar muscular arrangement of the sheaths in which the horns slide, they can be retracted down on the occiput, and work as springs on the base of the tongue, fore- ing it out with great velocity. Lindahl has noticed in some European woodpeckers an asym- metric arrangement of the horns as indicated in Fig. 474. The second group, the Cuculi, comprise such forms as horn- bills, kingfishers, toucans, and cuckoos. These are succeeded by the Cypseli, embracing the hum- cise ming-birds, goatsuckers, swifts, nighthawk (Chordeiles Virginianus, Fig. 475), and whip- poorwill, which have long pointed wings, great powers of flight, small weak feet, and, in the humming-birds, long slender bills. The latter are peculiar to America, being chiefly confined to South and Central America, only one species (Zrochilus colubris Linn.) extending into the Eastern United States, though a dozen or more species oc- cur inthe Western United States, and very many in Mexico. The highest group of birds, those which sing, are the Passeres or perchers. In these birds the feet are adapted for 552 ZOOLOGY. grasping, one toe projecting backward, while the bill is horny, usually sharp—conical, according to Coues. Various as are the shape of the wings, they agree in having the great row of coyerts not longer than half the secondaries ; the pri- maries either nine or ten in number, and the secondaries more than six. The tail, extremely variable in shape, has twelve rectrices (with certain anomalous exceptions). There is but one common carotid artery, and the sternum is very uniform in shape. Their high physical irritability is co- ordinate with the rapidity of their respiration and circula- tion ; they consume the most oxygen and live the fastest of all birds (Coues). There are two groups of Passerine birds, differing in the structure of the lower larynx ; in the first (Clama- fores) the vocal organs are more or less rudimentary, the species not being singers, while in the second and higher division (Oscines) the lower larynx is so developed that most of the species ex- cel as singers. In the sing- . ing birds the vocal apparatus Fig. 416.—Kingbird.From Tenney’s (syrimz), or lower larynx, is Done situated next to the lungs at the end of the windpipe, with a muscular apparatus formed -of five or six pairs of muscles, whose action varies the tension of the vocal cords and narrows or widens the glottides, which are elastic folds of the mucous membrane. A fold of the tympanal membrane of the syrinx, called the membrana semilunaris, projects inward. Representatives of the Clamatores are the Acadian fly- catcher, the wood pewee, the pewee or pheebe-bird, and the kingbird (Fig. 476). The last, sometimes called the bee- ‘martin, Coues tells us, destroys a thousand noxious insects for every bee it eats. The lyre-bird (Fig. 477) is also a member of this group. SINGING BIRDS. 553 This bird, with tail feathers so strikingly developed (Fig. 477), is so peculiar among higher Passeres that it has been proposed to separate it, with certain probable allies, from all the rest. The Oscines are represented by a host of species. These birds stand at the head of their class ; and as they are mostly Fig. 477.—The Lyre-bird of Australia (Menura superba). of small size, it may be said of them that they excel in qual- ity, not quantity ; most of them sing, being highly wrought, exquisite winged gems. Among the most notable are the jays, including the magpie of the Rocky Mountains (Fig. 554 ZOOLOGY. 478), the crow, and blackbird, so useful a bird, notwith- standing its mischievous propensities; the oriole, whose Fig. 478.—Magpie.—From Tenney’s Zoology. Fig. 479.—Butcher-bird,—From Tenney’s Zoology. hanging nest, brilliant colors, and lively song render it one of our most interesting birds ; while the reed-bird of the SINGING BIRDS. 555 South or bobolink, as it is called in the North, wakes up the meadows with nis lively notes. The finches with their conical beaks are succeeded, in the ascending series, by the English sparrow, a bird useful in the cities in destroying canker-worms, but @ nuisance in the country. Our song-sparrow (Melospiza fasciata) is widely distributed, and everywhere commends itself by its pleasant notes. Quite opposed in its habits is the butcher-bird or shrike (Fig. 479), a quarrelsome, rapacious bird, which feeds on Tee A wioey ne Viteo.—from insects or small mammals, often impaling them on thorns or sharp twigs, and leaving them there. The group of vireos or greenlets (Fig. 480) are peculiar to America ; their bills are hooked, with a notch at base ; they are warblers. The wax- wing (Ampelis cedrorum, Fig. 481) is the type of an allied family. The swallows and martins are interesting from the change made in the nest- ing habits of the more com- mon species which rear their young in artificial nests or in barns, or under the eaves of buildings. Another group character- istic of North America is the warblers, Dendreca (D. virens, Fig. 482) being the representative genus. On the other hand, the larks are an Old World assemblage _Fig., 461 —Carolina Waxwing —Bram of birds, but few species i occurring in this country, while the wrens (Fig. 483) are mostly restricted to America. The smallest bird in the United States, except the hum- ming-bird, is the gold-crested kinglet (Regulus satrapa 556 ZOOLOGY. Lichtenstein), which is less than 9 cm. (32 inches) in length. Lastly come the bluebird, the melodious thrushes, and the #ig. 483.—Winter Wren.—From Coues’ Key. mocking-bird, while at the head of the class in this country stands the robin (Turdus miaratorius Linn.). OLASSIFICATION OF BIRDS. 55? Crass VII.—AVES, Feathered Vertebrates ; jaws encased in horny beaks in existing forms 2 the fore-limbs forming wings; warm-blooded ; heart four-chambered ; lungs with accessory atr-sacs ; the bones dense, hollow ; oviparous ; eggs very large, covered by a calcareous shell. Sub-class 1. Saurure.—Tail as long as the body; head and fore limbs reptilian ; with feathers, scales, and teeth. (Arcliweopteryx.*) Sub-class 2. Odontornithes.—Vertebre biconcave, or as usual; jaws slender, with teeth implanted in sockets or in grooves; meta- carpals co-ossified ; sternum keeled or unkeeled ; wings well developed. (Ichthyornis.) Sub-class 3. Ratite.—Sternum smooth ; wingsrudimentary. (Struthio) Sub-class 4. Carinate.—Sternum keeled ; wings well developed. (Tur- dus. Laboratory Work.—The student should prepare a skeleton of a hen oF any other bird, and compare it, and especially the skull and limbs, with those of a reptile and a mammal. In dissecting a pigeon or fowl, at- tention should be given to those points previously indicated in which birds diverge from reptiles on the one hand and mammals on the other. Crass VIIL—Mammaria (Mammals). General Characters of Mammals.—In the mammals, which begin with the duck-bill, a creature in some respects re- minding us of the birds, and end with man, we observe, as compared with birds, an increased complexity of struc- ture ; and in the nature of the work done by the different organs, we may see a constant tendency to a development of parts headward, so that the head becomes large in pro- portion to the body, the rain increases in size, and the fore- limbs finally become hands, ministering to the intellectual wants of the animal. Also, as we ascend the series, the body, from being horizontal, with limbs adapted for walking on all fours, becomes finally in the apes semi-erect, in man wholly so. The greatest step in advance over the reptiles and birds * Vogt believes that this is a bird-like reptile ; a more perfectly pre- served specimen having lately been found, showing that the head and fore part of the body were more reptilian than Owen supposed, 558 ZOOLOGY. is in the nature of the limbs, the structure of the head, the organs of special sense, together with the increased com- plexity of the teeth, and the size and complicated structure of the brain, particularly of the cerebrum and cerebellum. The more important (diagnostic) features of the mammals are the articulation of the lower jaw directly to the skull, the quadrate bone becoming one of the ear-bones (the mal- leus) ; there are two occipital condyles ; the teeth are differ- entiated into incisors, canines, premolars, and molars ; the body is covered with hair. The body-cavity is divided into two compartments (thorax and abdomen) by a large muscle, the diaphragm, so that the lungs are separated from the ab- dominal viscera. From the four-chambered heart the single aorta is reflected over the left bronchus ; the blood is warm, with non-nucleated corpuscles ; the circulation is com- plete, the blood being entirely received by the right auricle and transmitted by the right ventricle to the lungs for aéra- tion, whence it is afterward returned by the left ventricle through the system. The brain is much larger than in birds, the cerebral hemispheres forming the bulk of the brain, and gradually, in different members of the ascending ‘series, overarching and finally concealing from above the cerebellum. The cerebral hemispheres are more or less connected (and in nearly inverse ratio) by an anterior com- missure and a superior transverse commissure (corpus callo- sum), the latter more or less roofing in the lateral ventricles (Gill). Mammals are viviparous, the embryo developing from a minute egg, and the young after birth are fed by the mother with milk secreted in the mamme or mammary glands; hence the name of the class, Mammalia. Returning to the skeleton, which we may examine more in detail: the skull, as a brain-box, is much larger than in the reptiles and birds. The brain-cavity of Coryphodon and other extinct Tertiary mammals was exceedingly small, scarcely larger in proportion than in reptiles, and there is a progressive increase in size of the cavity of the skull in the more specialized descendants of this early Tertiary type, as seen in that of the horse, when compared with its Eocene progenitors. There is also a decided increase in the brain- STRUCTURE OF MAMMALS. 559 box of the monkey as compared with that of the lemur, and of apes as compared with monkeys, while in man the brain «capacity is twice that of the highest apes. The different regions of the vertebral column are better defined than in the birds and reptiles; this is seen in the cervical vertebre, the number of which is usually seven. The exceptions to this rule are few, there being six in one sloth (Cholepus), eight or nine in another sloth (Bradypus), and six in the American manatee. Behind the cervical is the dorsal region, consisting of from ten to twenty-four, usually thirteen, vertebre, and the lumbar region, which is composed of from two to nine, usually six or seven, vertebre, sand is marked off by the absence of movable ribs. The Fig. 484.—Skull of the Lion.—After Owen. shoulder-girdle is not solidly united to the dorsal vertebra, but loosely attached by mr les and tendons. The pelvis —1.e., that portion called the ilium—connects with a single, sometimes two, rarely three, vertebree of the sacral region, and the union of these vertebrae with one or more caudal vertebra forms an assemblage of consolidated vertebra, called the os sacrum, which in the sloths, or Edentates, comprises eight or nine vertebre. The number of caudal vertebre in the monkeys may amount to thirty, in the long-tailed manis (Fig. 501) to forty, while in other mammals there may be less than this number, there being four retained by man and the larger apes, while in some bats there are only three. 560 ZOULOGY. But it is in the limbs, and especially the feet, of mammals that the skeleton varies most, and always in accordance with the different habits of the creature. The limbs of mammals differ from those of the lower vertebrates in the fact stated by Gegenbaur, that the planes in which the angles of the limbs of either side are set are parallel to the vertical me- dian plane of the body, thus giving greater independence to the limbs, which now become supports for the body, since they raise it from the ground. Beside this, the angles be- tween the equivalent portions in each limb do not agree- with each other, as in the rep- tiles, but point in an opposite direction in the case of the fore and hind limbs respectively (Gegenbaur). As we ascend in the mammalian series, the limbs, particularly the fore-limbs, are variously modified. The limbs. of whales are paddle-like, though. the bones of the limbs are homo- Jogous with those of other mam- mals. The feet of the seal are webbed, forming flippers ; it can- not support itself on its limbs, but the fore-feet have consider- able motion of the radius on the ulna. In the dog the fore-limbs have but little motion of the ioe of the Thumbless radius on the ulna, but the cats (felide) have more of this rotary motion, enabling them to grasp with the fore-foot. This rotary motion of the fore-arm, involving the modification of the fore-foot into a hand, is seen in the thumbless mon- keys (Fig. 485), and in those provided with a thumb, in the- gorilla, and especially in man. The extreme of specializa- tion of all four limbs is seen in the horse, which has but: one digit, and walks on its single toe-nail. In the bat, the ulna and radius are fused together as one bone, and the last three fingers are greatly lengthened. The liberation of HAIR AND HORNS OF MAMMALS. 561 the limb from the body becomes more marked as we ap- proach man. In the seal, only the wrist protrudes from the skin, the limb of the otter slightly more; the horse’s leg does not protrude beyond the elbow, that of the monkey projects two thirds of its length, while in man the limbs become wholly free from the trunk (Wyman). The hairs originate in minute sacs which extend from the: epidermis into the cutis ; from the bottom of this inpushing of the epidermis grows up the shaft of the hair, which ig TY SS = CY Z A Fig. 486.—Diagram of the development of the nipple ; vertical section. a, periphery of the glandular area (6): gl, glands. A, form of the gland in Echidna; B, its form in most mammals; C, its form in some ungulates, as the cow, mare, etc.—After Gegenbaur. surrounded at the base by the cellular wall of the hair-sac forming the root-sheaths. The spines of the porcupine, the scales of the Manis, of the armadillo, of the tail of the rat, are modified hairs, all developing in the same manner. Many mammals, especially the ruminants, as the deer, ox, rhinoceros, etc., are armed with horns. There are two kinds, those which are solid and bony, as in the deer ; while in others, as the antelopes, sheep, goats, and oxen, the horns. are hollow, the horny case enveloping a bony core; hence 562 ZOOLOGY. they are sometimes called Cavicorns. In most horned mammals, the horns are persistent; in the deer they are dropped annually ; in the prong-horned antelope (Fig. 487) the horns are also shed annually. The mammary glands are modifications of the tegument- ary glands which are found in all vertebrates except fishes. In the duckbill and spiny ant-eater (Zchidna), these glands retain their simple elementary nature. In all others nip- ples are developed (Fig. 486). They correspond in general to the number of young in a litter. The dentition needs careful study in connection with the \ aap Fig. 487. — Hollow WE ws honk of the Prong \S Ss horned Antelope. Fig. 489.—Skull of a Porcupine.—After Owen. fossil remains of mammals, as the different orders are char- acterized in great part by the differences in the form and number of the teeth, which are intimately correlated with the structure of the digestive organs and the nature of the limbs ; thus while vertebre are useful in identifying or re- storing fossil reptiles, the teeth are especially serviceable in classifying fossil mammals. Some existing forms are en- tirely toothless, as the duckbill, where the teeth are repre- sented by horny plates, and the ant-eater (Fig. 488). While the sloths have no incisors, these are present and very large in the rodents, but the canines are absent (Fig. 489). THE HAR OF MAMMALS. : 563 In the elephant the upper incisors form the tusks, the cor- responding teeth of the lower jaw being absent. In many teeth, as those of the deer (Fig. 490), the crown of the molars is quite convex, with crescent-shaped enamel areas. The canines are large and sabre-shaped in the cat fam- ily, while in the pigs, especially the baby- roussa of Malaysia, the upper pair curve upward and backward to the forehead. The premolars and molars have two or pie, 490—Crown of three roots or fangs ; in none of the lower {h6iporm of & der vertebrates do the teeth have more than g7¢s¢ents.— After one root. The organs of sense are much developed, especially the ear. The quadrate bone of the reptiles and birds, which is Fig, 491.—Diagram of the labyrinth of the ear in J, the fish, 77, the bird, and Z/Z,a mammal. JU, utriculus; S, sacculus; US, utriculus and sacculus; C7, canalis reuniens ; &, recessus labyrinthi; UC, commencement of the cochlea, 0, Z, lagena; K, cceca sac at the apex; C, ccecal sac of the vestibulum of the cochlear canal.—After Wal- deyer, from Gegenbaur. large, external, and suspends the lower jaw to the skull, now becomes much changed, and forms the zygomatic process of the squamosal bone. The labyrinth of the ear, largest in fishes, is smallest in mammals. The cochlea 564 ZOOLOGY. (Fig. 491, C) is greatly developed in the mammalia, while the external ear now appears. This is a prolongation of the edges of the first branchial cleft of the embryo. There is, however, no external ear in the Monotremes (duckbill). It is also absent in whales, the Sirenians or sea-cows, in most seals, and is very small in the eared seals (Otaria). The eye of mammals is not essentially different from that of the lower vertebrates. The general anatomy of the soft parts of a mammal may be studied by dissecting a cat, with the aid of the following description and drawings prepared by Dr. C. 8. Minot: Fig. 492 illustrates the general anatomy of the cat; the skin and right half of the body-wall have been removed. The body-cavity is divided into an anterior and posterior division by a transverse arched partition, the diaphragm (D), composed of a thicker peripheral muscular portion and a thinner central tendinous part. Through the latter puss the great blood-vessels and the esophagus. The anterior chamber is the thorax or pleural cavity, and contains the respiratory organs and heart. To show these, the right lung has been removed. The heart (Hf) was en- closed in the thin-walled pericardial sac, which has been cut away. The great systemic veins enter from behind— t.e., dorsally ; from below the vena cava inferior, passing up through the diaphragm and uniting opposite the heart with the large vein, cavu superior, , from above, the two emptying into the right auricle. The csophagus (Oe) overlies the trachea (Zr). The aorta arises from the heart, and, curving upward and backward, runs to the left of both trachea and esophagus, as indicated by the dotied lines, and continues its backward course just below the vena uzygos, into the abdomen. The trachea gives off a bronchus to each lung (Zu). The lungs are sacculated elastic organs, with no main central cavity. They are separated dorsally by a thin median vertical membrane (Jf ), the mediastinum, the equivalent of the mesentery in the abdomen. Lying on the side of the vertebral column can be seen part of one of the two chains of sympathetic nervous ganglia (8). ANATOMY OF THE CAT. 565 The abdominal cavity contains the principal reproduc- tive, excretory, and digestive organs. ‘The csophagus ter- minates in the stomach almost immediately below the dia- phragm. The stomach (5S?) occupies a transverse position, its larger (cardiac) end, which receives the esophagus, lying ‘on the left, the smaller (pyloric) end on the right. The pylorus has a sphincter muscle which can completely close the orifice. The stomach is followed by the long intestines (Jn), most of which have been removed, leaving a short piece in front. The posterior portion of the intestine is somewhat dilated, is called the colon, and passes into the wide terminal rectum (fcc). The whole abdominal portion of the intestinal canal is suspended from the me- -dian dorsal line by a thin membrane, the mesentery, which forms several folds, the most striking of which is the omen- tum or grand epiploon (Om.). This fold, when in situ, hangs down from the stomach like an apron, covering over the intestines ventrally. Upon opening the walls of the abdomen, it is the first structure met with. It usually con- tains a great deal of fat. Its principal function is supposed to be to prevent the loss of heat. The omentum is present in -all mammals, but is least developed in Cetaceans, being most prominent in Carnivora and ruminants. Connected with the intestine are two glands, the liver (Zi) and pancreas. The liver is large and lies directly underneath the diaphragm. The elongated light-colored pancreas lies alongside the front end of the intestine (Jn), or so-called duodenum ; in its ‘microscopic structure it resembles the salivary glands. The spleen is closely connected with the stomach, and is of an elongated shape, as in the majority of the Mammalia mono- delphia. The kidneys (A) are large and oval, and lie on either side of the vertebral column; the aorta passes between them, giving off a renal branch to each gland. A deli- cate ureter (Urt) passes from each kidney obliquely across the rectum to the large flask-shaped bladder (B/). A ‘urethra (Ur) arises from the bladder posteriorly and 566 ZOOLOGY. opens in the female immediately below the anus, but in the male enters the penis. The ovary (Ov) is small and is placed near the open end of the oviduct or Fallopian tube, which can be seen in the figure extending alongside the rectum above the bladder. The two oviducts (Ovd) unite posteriorly to form the uterus Ut). ae 492, II., isa median longitudinal section of the brain. The spinal cord passes into the medulla oblongata (.), over which lies the large cerebellum (Cb), and the small corpora quadrigemina (Q). In front is the large cerebrum (C) and the small olfactory lobe (Z). Fig. 492, IIL, is a diagram of the eye (see explanation of the figure). By carrying the dissection further, the student will be able to examine the tongue with its papille ; the epiglottis at. the back of the mouth in front of the trachea ; the larynx, a peculiarly modified portion of the trachea in the neck, with two elastic bands stretched across its interior; the bands or vocal cords may be set in vibration by a blast of air from the lungs. The heart may also be dissected fur- ther to find the origin of the pulmonary vessels, and to. make out the four divisions or chambers. (AMinot.) The eggs of mammals are exceedingly minute, partly owing to the small quantity of yolk in them ; the eggs of the few which have been examined are about a quarter of a milli- metre (;4;—;}, inch) in diameter. In the duckbill the egg is large and with more yolk, like those of birds, being about. five millimetres in diameter. Mammals are divided into non-placentals and placentals, according as the embryos are surrounded or not with a placenta or ‘‘ after-birth.’”’ This organ is a development of the allantois, serving as a means chiefly of nutrition, being filled with blood-vessels leading from the walls of the womb of the parent, and also acting as an organ of respiration, and to carry off the effete pro- ducts by means of the maternal circulation. Mammals may be born helpless and only partly developed, as in the Marsupials ; or capaole of locomotion and sucking milk, as in the calf or colt; or helpless for many months, as in human infants. ‘The changes in the form of the body after birth are much less, on the whole, than in the birds, The sexes differ externally in size and ornamentation. 567 ANATOMY OF THE CAT. Fig. 492.—Anatomy of the Cat. D, diaphragm ; Ht, heart; Zu, lung; plc, pleural cavity; V, vena cave. superior; V7, vena Jugu- laris ; c’, branch of the external ; ¢”, branch of the internal carotid; 77, trachea ; S, sympathetic ganglia; Oe, esophagus; v.a, vena azygos ; M, mediastinum ; Ps, psoas muscle; Jn, intestine; Ai, kidney; Ov, ovary; G ¢, ureter; Ovd, oviduct; Sa, sacrum; Ree, rec- tum; U¢, uterus; Ur, urethra; Bl, bladder; Om, omentum; S¢, stomach ; Zi, liver. : ¥ig. 492, II.—Median longitudinal section of the brain. Jf, medulla oblongata; @, cerebellum ; Q, corpora quadrigemina ; p, pin- eal ee ; O, cerebrum or hemisphere ; Z, olfactory lobe ; c.a, anterior commissure ; op, optic nerve ; m.c, middle commissure ; ¢.c, cor- pus callosum. 3 . : Fig. 492, IIT.—Median vertical section of the eye, diagrammatic. 1, optic nerve ; A, posterior chamber, containing the vitreous hu- mor: 2, corpus ciliare ; 8, lens, partly covered in front by the pigmented iris ; 4, anterior chamber, containing the aqueous humor ; 5 cornea. The walls of the chamber A consist of three layers, represented by three lines, the outer the sclerotic ; the middle, the cho: yoid ; the inner, the retina.—Drawn by C. 8. Minot, 568 ZOOLOGY, Darwin calls attention to the fact that in mammals the male wins the female rather by the law of battle than by the dis- play of high colors and attractive ornaments. During the breeding season, desperate contests take place between the rival males; even the males of the timid hare will at such times fight until the weaker is killed ; so moles, squirrels, horses, male seals and male sperm-whales, whose heads are larger than in the female, and beavers, will fight desperately. It is a rule that the males of such animals as are provided with tusks or horns always fight for the possession of the female. It is so with bulls, deer, elephants, boars, and rams ; at the same time these are organs of defence by which the males protect their family, flock, or herd. On the other hand, in the female rhinoceros, some antelopes, the reindeer, as opposed to the other deer, some sheep and goats, etc., the horns are nearly as well developed as in the opposite sex. The modes of attack are various: the ram charges and butts with the base of his horus, the domestic bull gores and tosses any troublesome enemy, while the Italian buffalo ““is said never to use his horns; he gives a tremendous blow with his convex forehead, and then tramples on his fallen enemy with his knees.’’ Darwin also says that male quad- rupeds with tusks use them in a variety of ways; thus the boar “strikes laterally and upward, the musk-deer with serious effect downward,’’ while the walrus can strike either upward, downward, or sideways with equal dexterity. The males are usually larger when there is any difference in size ; this is seen in the eared seals, especially Callorhinus ursinus, in the ox, Indian buffalo, and the American bison, as well as the lion. The mane of the latter adds to its ap- pearance of greater weight and bulk, and Darwin says that the lion’s mane ‘‘ forms a good defence against the one danger to which he is liable—namely, the attacks of rival lions.”’ As regards distinctions in color, male ruminants are most liable to exhibit them. In the Derbyan eland the body is redder, the neck much blacker, and the white band separating these colors broader than in the females. In the Cape eland the male is slightly darker than the female. In the Indian black-buck the male is very dark, almost black, VOCAL ORGANS OF MAMMALS. 569 while the female is fawn-colored : male antelopes are blacker than the female. The Banteng bull is almost black, while the cow is of a bright dun. Among the lemurs the male of Lemur macaco is coal-black, while the female is reddish yel- low. The sexes of monkeys differ much in coloration. Cer- tain male seals, bats, rats, and squirrels have brighter colors: than in the opposite sex. On the other hand, the female: Khesus monkey is adorned with a brilliant red naked ring around the tail ; this is wanting in the male, which, how- ever, is larger, with larger canines, more bushy whiskers: and eyebrows ; and Darwin states that in monkeys the males. usually differ from the females in ‘‘ the development of the: beard, whiskers, and mane.”’ The vocal organs of mammals are, in general, constructed! on the same type. The larynx is formed by a modification of the uppermost ring of the trachea, called the cricotd car- tilage, to the anterior and dorsal edges of which two arytenoid cartilages are attached, while a V-shaped thyroid cartilage, open behind, is attached to its side. The vocal cords, which are modified folds of the mucous membrane lining the trachea, are stretched between the arytenoid and thyroid cartilages, the slit between them being called the glottis,. which is covered by the epiglotéis. Thus, in mammals the organs of voice are situated almost solely at the upper end of the trachea. In the whales the vocal chords are not de- veloped. The male gorilla, which has an exceedingly loud voice, as well as the adult male orang and the gibbon, is. provided with a laryngeal sac. In the howling monkey (Mycetes) of Brazil, the hyoid apparatus and larynx are re- markably modified, the body of the former being changed into a large bony drum or air-sac communicating with the larynx. The vocal organs are a third larger in the males than in the females. ‘‘ The males begin the dreadful con- cert, in which the females, with their less powerful voices, sometimes join, and which is often continued during many hours’? (Darwin). They apparently howl, as birds sing, for the simple pleasure of the thing. Apparently, the most musical mammal, man excepted, is a gibbon (Hylobates agilis), which can sing ‘‘ a complete and correct octave of 570 ZOOLOGY. musical notes’? (Martin ez Darwin). While quadrupeds use their voices as alarm calls, most of the sounds are pro- duced by the males, especially during the breeding season. Animals are mutually attracted or are individually pro- tected from the attacks of other species by odors. The scent-bags or odoriferous glands secreting a fluid differing in consistency in different animals, are situated near the base of the tail, as in the skunk, polecat, musk-deer, civet- cat and allies, or they may be developed in the side of the face, as in the male elephant, as well as sheep and goats. The odor is either of musk or some form of it. The shrew- mice, by reason of their odoriferous glands, are disliked and consequently not hunted by birds. Universal deference is paid to the skunk ; few dogs, and only those which are in- experienced or peculiarly gifted, attacking them. The males more usually emit a stronger odor than those of the opposite sex. Some mammals have a summer and a winter pelage. The hare, at the beginning of winter, doffs its summer coat for a suit of white. The hybernation, or winter-sleep, is a re- markable feature in the life of quadrupeds living in the north temperate zone, such as the bear, dormouse, and bats. During this period the temperature of their body falls, respiration and circulation are lowered in the one case or nearly ceases in the other, and life is sustained by the ab- sorption of fat, which accumulates on the under side of the neck in the so-called hybernation-glands. There are about 3500 species of mammals described, of which 2100 are living; of these 810 inhabit America north of Mexico. Mammals live all over the earth’s surface, but mostly in the tropical region, those of the arctic zones having been derived from the south since the end of the Tertiary period. The range in space of certain species is very great— ‘for example, the cougar, panther, or pumaranges from Brit- ish to South America (Chili). The mammalian fauna of the Tertiary deposits of the west was far more abundant than now, the remains of over five hundred species having been already discovered by Leidy, Cope, and Marsh in the few spots ex- amined. The earlier (Eocene) mammals were generalized ORIGIN OF DOMESTIC MAMMALS. 57L forms, combining in a remarkable degree characters more elaborated, and in great detail, in different, orders of living mammals, especially the Ungulates. For example, from the Eocene Coryphodon, a generalized ungulate animal, have probably been derived the ruminants, the tapirs, hog, hip- popotamus-like forms, the rhinoceros, and, finally, the horse. This inference is based on the fact that the bones. and teeth of Coryphodon present characters which are no. longer combined in any one species of mammals, but which are found worked out in detail in the members of the differ- ent orders referred to. Moreover, the early Tertiary mammals had brains much smaller than in any existing forms, and with only one ex- ception, without convolutions—showing that the develop- ment of the size of the brain and its convolutions, and con- sequently of the intellect, has kept pace with the successive: stages in the specialization shown in existing forms, and. which agree with the increasing complexity of the Ameri- can Continent and the subdivision of the western part of the continent into distinct basins, with separate mountain. systems and river-valleys. The result of all this apparent waste of generalized forms, and the survival of the few favored types now existing, has been the preservation of animals which have been domesticated by man, such as the dog, pig, horse, ox, camel, elephant, and of others useful as food or as intelligent servants ministering to his every-day wants. The earliest mammals were small insectivorous or gnaw- ing marsupials, none larger than a cat, and first appearing in Jurassic strata. The Mammalia are divided into three sub-classes—viz., the Ornithodelphia (duckbill and Echidna), the Didelphia or marsupials, and the Monodelphia, comprising all the higher mammals. Sub-class 1. Ornithodelphia.—The duckbill and spiny ant- eater (Fig. 493, Echidna hystrix) are the only representatives of the sub-class, of which there is but a single order, called Monotremes, and are distinguished by the following char- acters. The oviducts, vasa deferentia and ureters, open inte 572 ZOOLOGY. the cloaca, as in birds. The sternum is provided with a pecu- liar T-shaped bone, and there are important features in the Fig, 403.—Spiny Ant-cater (Mehidne hystrir).—Vrom Brehm's Thiorleben, brain separating them from the members of the higher sub- «lasses. Echidna lays large eggs, 2 cm. long, placing them DUCKBILL AND ECHIDNA. 573 in a mammary pouch, where the young hatch. The duck- bill also lays large eggs. The embryonic development is meroblastic, as in reptiles. ‘lhe toothless jaws are long and narrow in the #chidna, or broad and flat in the duckbill (Ornithorhynchus paradocus Blumenbach), where it is cov- ered by a leathery integument; the external ear is wanting. Fig. 494.—Skeleton of Echidna hystrix,—From Brehm’s Thierleben, In the aquatic duckbill the feet are webbed, with claws of moderate size. It is covered with a soft fur, and is ahout half a metre (17-22 inches) long. Its habits are like those of a muskrat, fre- quenting rivers and pools in Australia and Van Dieman’s Land, sleeping and breeding in holes extending from un- der the water up above its level into the banks, and with an outlet on shore. It lives on mollusks, worms, and water-insects. Young duckbills, five em. long, have been found in their nests. The spiny ant-eater (Figs. 493 and 494) is represented by three species, the Echidna hystrix Cuvier, of Aus- tralia, #. Lawesit Ramsay, from Port Moresby, New Guinea, also by a re- B& : cently discovered form inhabiting the sak ae 4 elevated portions of Northern New marsupial bones, 7 Guinea, and called by Gervais Acanthoglossus Brutjnii. In these singular animals the bill is long and slender, tooth- 63 574 ZOOLUGY, less, while the palate is armed with rows of strong, sharp spines ; the tongue is long and slender, like that of the ant- eater, while the body is armed with quills like those of a porcupine ; the claws are very large and strong, adapted for tearing open ant-hills. All the species are from one third to one half of a metre (12-19 inches) in length. Fig. 496.—Skeleton of the Kangaroo.—From Brehm’s Thierleben. Sub-class 2. Marsupialia.—These are singular forms, rep- resented by the opossum in this country, and the kangaroo, with a number of other forms, in Australia. They differ from all other mammals in having a pouch (marsupium) for the reception of the young immediately upon birth, where. MARSUPIALS. 575 they are attached to the nipples at the bottom of the pouch. This large pouch (absent in some opossums and in the Dasyuride) is supported by two long slender bones attached to the front edge of the pelvis and projecting forward (Fig. 495 m and Fig. 497). In Thylacinus, the Tasmanian wolf, these bones are car- tilaginous. In the opossum, the kangaroo, and probably most marsupials, the young remains in the pouch attached to the nipple, which ‘fills the mouth. ‘‘ To this it remains at- tached fora considerable period, the milk being forced down its throat by the contraction of the cremaster muscle. The danger of suffocation is avoided by the elongated and coni- cal form of the upper extremity of the larynx, which is em- braced by the soft palate, as in the Cetacea, and thus respi- ration goes on freely, while the milk passes, on each side of the laryngeal cone, into the esophagus” (Huxley). In the car- nivorous forms the brain is Jow in struc- ture, the olfactory lobes being very large, completely exposed, while the cerebral ‘ hemispheres are small te dy ot penis with the marsupial bones. and quite smooth. : The dentition of marsupials is characteristic, none having three incisor teeth upon each side, above and below, and none but the wombat (Phascolomys), with an equal num- ber of incisors in each jaw, there being usually more in the upper than in the under jaw. The lowest marsupial is the Tasmanian wol* (Thylacinus), which is rather smaller than the wolf. The Tasmanian devil (Dasyurus ursinus Geoffroy, Fig. 383) is a vicious, trouble- some creature, about the size of a badger. The opossums inhabit North and South America. They have a long tail and a plantigrade step—i.e., they walk on the sole of the whole foot. The Virginian opossum (Fig. 497, Didelphys Vir- 576 ZOOLOGY. giniana Shaw) lives chiefly in trees. Lawson says that ‘*the female doubtless breeds her young at her teats, for I have seen them stick fast thereto when they have been no Fig. 498.—The Kangurov (Afacropus),—Vrom Brelim’s Thierlehen, bigger than a small rasberry and seemingly inanimate. She has a paunch, or false belly, wherein she carries her young after they are from those teats, till they can shift for EDENTATE MAMMALS, 577 themselves. Their food is roots, poultry, or wild fruits. They have no hair on their tails, but a sort of a scale or hard crust, as the beavers have. If a cat has nine lives, this creature surely has nineteen ; for if you break every bone in their skin and mash their skull, leaving them for dead, you may come an hour after and they will be gone quite away, or perhaps you may meet them creeping away.”’ (“* Perfect Description of Virginia,’’ 1649.) There are squirrel-like flying marsupials (Petaurus), ‘marsupial rats, marsupial bears, and marsupial ant-eaters (Myrmecobius), but the most characteristic Australian ani- ‘mals are the different kinds of kangaroo (Macropus thetidis, Fig. 498). The largest species, M. giganteus Shaw, is 1-8 metres, or nearly six feet long. Kangaroos go in herds, and move by & succession of long leaps. All marsupials are stupid, low in intelligence, and, in the insectivorous and carnivorous forms, of vicious temper. With the exception of the opossums, all'are confined to Aus- tralia, New Zealand, and New Guinea. Sub-class 3. Monodelphia.—While in the marsupials the termination of the oviduct is double, in the present group it is always single, whence the name Monodelphia. The members of the group are also called placental Mammalia, because the young at birth are of considerable size and nearly perfect in development, being nourished until born ‘by a highly vascular mass or thick membrane ( placenta) supplied with arteries and veins, developed originally from the allantois, which is a temporary embryonic membrane. The brain, as a rule, presents an advance over that of any of the preceding mammals, the corpus -allosum being better developed, while the anterior commissures are all reduced. There are no marsupial bones, though in some Carnivora certain small cartilages appear to represent them. There are twelve orders, as follows : Order 1. Bruta or Hdentata.—These creatures, repre- sented by the sloths, ant-caters, pangolins, and armadillos, stand next above the non-placentals or marsupials, as the brain is but little better developed, the hemispheres in some 578 ZOOLOGY. forms being nearly smooth, while, in point of their general structure and intelligence, they stand at the foot of the sub- class. The teeth may be entirely undeveloped, as in the. common ant-eater, but when developed they are not encased. Tig. 499.—Skeleton of tue Ai, or Three-toed Sloth.—After Owen in enamel. In most Edentates the incisors are absent, but the lateral one may exist in the armadillo (Dasypus). The feet are formed for grasping or digging, and end in large straight or curved claws. They are either hairy or pro- SLOTHS AND THEIR ALLIES. 579 tected, as in the pangolins (Fig. 501) and armadillos (Fig. -502), with large thick scales. They feed on insects and de- cayed animal matter, or on leaves. They are of moderate size, though certain extinct forms were colossal in stature. The leaf-eating forms, viz., the sloths, differ from the other Bruta in the very long and slender limbs, the hinder pair theshorter. There are five teeth above and four below, which become sharp with use, like chisels; the stomach is said to be remarkably complex. In disposition these crea- tures are types of sluggishness ; they live in trees, being absolutely helpless on the ground, not being capable of walking on the bottom of the foot. Waterton says that, in climbing, the ai (Bradypus tridactylus, Figs. 499 and -500) uses its legs alternately ; that its hair ‘‘is thick and coarse at the ex- ‘tremity and gradually tapers to the root, where it becomes fine as a spider’s web. His fur has so much the hue of the moss which grows on the branches -of the trees, that it is very difficult to ‘make him out when he is at rest.” Only two Edentates now occur in the United States, but formerly colos- sal, sloth-like forms, with some resem- : ‘blance to the ant-eaters, ranged over | Fig. 500.— Ai, or Three. ‘the Southern and Middle States as far tude.— After Wood, from f . Waterton. north as Pennsylvania, their bones oc- ‘curring in aves. Such was the Megatherium, a gigantic, -sloth-like creature, which extended from Pennsylvania to the pampas of South America, and whose skeleton is over five metres (18 feet) long. With it was associated the Meg- _alonyz, first described by Thomas Jefferson ; it was as large as a bison, as was the Mylodon. ‘Thes> animals walked on the soles of the feet, could rise on their hind legs and partly support themselves by their thick tails, pulling down large ‘trees and feeding upon the leaves and smaller branches. Tn the ant-eaters the jaws are toothless, but very long, and ‘the tongue is of great length and very extensile ; the sub- 580 ZOOLOGY. maxillary glands are very large, so that the viscid salivary fluid is very abundant. They burrow into ant-holes, thrust- ing the tongue among the ants, which stick in multitudes to the viscid, writhing rod, and are withdrawn into the mouth. The pyloric end of the stomach is gizzard-like. The ant- eaters (Myrmecophaga) inhabit South America. The pangolins, or species of -Wanis, are mail-clad ant- eaters, the body and long tail being covered with large overlapping scales. When molested they roll up the body. In walking the hind feet rest on the soles, while the fore- feet are supported by the upper side of the long bent claws. > < SRA Fig. 501.—Pangolin (Manis (angi -auaatv) robbing white ant-nests —After Monteiro, The long-tailed pangolin of the West Coast of Africa (Fig. 501) tears open with its long claws the nests of the white ants. It is nearly 2 metre (28-30 inches) in length. The armadillos (Fig. 502) are small mammals covered with a carapace, consisting of from three to thirteen transverse rows of movable scales ; by rolling into a ball, these singu- lar creatures become thoroughly protected from their ene- mies. Dasypus novem-cinctus Linn. is much like the Peba armadillo, and extends from South America to Texas. The strange extinct armadillo-like @lyptodon of South Amer- ica, which was over two metres (8 feet) long, was covered THE ARMADILLO. 581 by a heavy, solid coat-of-mail consisting of polygonal plates soldered together immovably. The three following orders have by most authors been placed near the Primates (monkeys, etc.), but Owen, from ‘TaMO JAI 9 Seiqn ‘99 {(rayueqD0N ping) oy] Jo ywiod aq} ojs0ddo IN} JO [RpNwo ‘pO swUNIOVS ‘YY SUOTsaI IBquUIN] “7 tsaTvOs [eunteptda jo uae ey) Jo oulyNO ayy YIN morse [esiop ‘G ‘O[[Ipwure Bqog Jo uoJo[exS—e0g “SLA YsIq? Jo Inwes ‘og tuolsar —euyn ‘gg tsniautng ‘zg temdros ‘1g iemqy 81 Jaquinu 9q]3) suo! the characters afforded by the brain, has shown that they be- long at or near the bottom of the scale. Gill has shown that not only by the brain, but by other characters corre- lated with the low development of the brain, the Rodents, 582 ZOOLOGY. Insectivora, and bats should be associated with the Edentates in Bonaparte’s division (or, as Gill terms it, super-order) of Ineducabilia (which corresponds to Owen’s sub-class Lissencephaila,. In these four orders, then, the cerebrum is small, smooth, with none or few convolutions ; in front it does not cover the olfactory lobes, and behind leaves the cerebellum wholly or partly uncovered. On the other hand, in the super-order Educabilia, com- prising the following order: Cete, Sirenia, Proboscidia, Hy- racoidea, Toxodontia, Ungulata, Carnivora, and Primates, the brain has a relatively large cerebrum, behind overlap- ping much, or all, of the cerebellum, and in front much, or all, of the olfactory lobes (Gill}. The cerebrum is also con- yoluted ; the convolutions increasing in number and com- plexity, until we reach the apes and man, and accompanied by increasing intelligence and capability for mental im- provement. Other important characters are mentioned by Owen and by Gill in support of this arrangement. In the smooth small cerebrum, as well as in other re- spects, the Zneducabilia are related, together with the mar- supials and duckbill, to the birds and reptiles. In the cloaca, the convoluted trachea, the long, slender, beak-like, toothless jaws and the gizzard of the ant-eaters, the quills of the porcupine and hedge-hog, the proventriculus or crop of the dormouse and beaver, in the growing together of the three chief metatarsals of the jerboa, asin birds, in the keeled sternum and wings of the bats. there are points of resem- blances to birds. Owen, whom we have quoted, also adds the aptitude of the bats, insectivores and certain rodents “to fall, like reptiles, into a state of torpidity, associated with a corresponding faculty of the heart to circulate car- bonized or black blood.”’ However, there are points in which these orders are re- lated to the lemurs and monkeys. Order 2. Glires. (Rodentia.)—The rats, squirrels, por- cupine, and beaver are common examples of this extensive group. They differ from other orders in the large incisors, the dental formula of which is normally 3 ($ in Leporide@ and Lagomyide), and in the absence of canine teeth. The ORDER OF RODENTS. 583 condyles of the lower jaw are longitudinal, not received in spe- cial glenoid sockets, but gliding freely backwards and forwards in longitudinal furrows. The feet are adapted for walking and climbing or burrowing, the claws being well developed. A peculiarity in the incisors is that they grow out as fast as they are worn down ; this is due to the fact that the pulp is persistent ; the enamei in front causes them to wear away Fig. 503.—American Flying Squirrel (Sciuropterus volucella) behind so that they are chisel-shaped. The species are pro- lific, live mostly on vegetable food, and are of small size; the muskrat, beaver, and capybara being the largest mem- bers of the group. The flying squirrels (Fig. 503) take short flights by means of the expansion of the skin between the fore and hind legs. The Norway lemmings are notice- able for their remarkable migrations from the elevated 584 ZOOLOGY. plateaus of Scandinavia down and into the sea; the object and origin of which are inexplicable, and are not indicative of much intelligence. From this and their nest-building habits, rodents are, as a rule, not unlike birds ; and Owen, for these reasons, ascribes to them a low degree of intelligence. Granting that this is the case, an exception to this rule is seen in the social beavers, which evince a high, exceptional degree of intelligence. Beavers build a dam in a running stream so as to create an artificial pond as a refuge when at- tacked, as well as a subaquatic entrance to their lodges and to their burrows in the banks of the streams they inhabit. Bea- ver dams are built at first by a single pair or family, and are added to from year to year, and afterwards maintained for centuries by constant repairs. They are built of sticks and mud, usually curve up stream, with a sloping water-face. Beavers lay up stores of wood for winter use in the autumn; they can gnaw through trees eighteen inches in diameter; they work mostly at night. They often construct artificial canals for the transportation of the sticks of wood to their lodges. This, in the opinion of Mr. Morgan ‘‘is the highest act of Intelligence performed by beavers.” When ponds do not reach hard-wood trees or ground in which they can burrow for safety, they will build canals with dams, and so excavate them that they will hold the surface drainage. Morgan describes one canal about 161 metres (523 feet) long which “served to bring the occupants of the pond into easy con- nection, by water, with the trees that supplied them with food, as well as to relieve them from the tedious, and per- haps impossible, task of moving their cuttings five hundred feet over uneven ground, unassisted by any descent.” Bea- vers. In swimming, use their tail as a scull, and the hind teet being webbed, its propelling power while swimming is very great. They carry small stones and earth with their paws, holding them under the throat, and walking on their hind feet. They nse the tail in moving stones, working it under so as to “give it a throw forward.” Beavers are very social, working together and storing up wood in common. “A beaver family consists of a male and female, and their offspring of the first and second years, or more properly, HABITS OF THE BEAVER. 585 under two years old. The females bring forth their young from two to five at a time, in the month of May, and nurse them for a few weeks, after which the latter takes to bank.” They attain their full growth at two years and six months, and live from twelve to fifteen years. * : Allied to the beaver, Fie, 504.—Sewellel or Showt'l. Much reduced. but forming the type —From American Naturalist. of a distinct family, is the singular sewellel or showt’l An (Haplodon rufus Coues, Fig. 504) of the mountains of west- ern Oregon and Washington Territory. It is nearly as large * The American Beaver and his Works. By Lewis H. Morgan. 1868. 586 ZOOLOGY. as a muskrat, is nocturnal in its habits and, therefore, rarely seen, and burrows in the earth, feeding on roots. The lowest in intelligence are, perhaps, the hares, rep- resented by the common varying hare (Lepus 648 ZOOLOGY. 4g uP Fig. 541.—Five schematic figures showing the development of the fetal egg-mem- branes, where in all except the last the embryo is represented as if seen in longitudinal section. 1. Diagram of egg with zona pellucida, blastoderm & #), germinal disk, and) embryo. 2. Egg with the first traces of the yolk-sac (d) and amnion (Ks, 88, and am. 3. Egg with the amnion uniting and forming a sac ; the allantois (a/) budding ont. 4, Egg with the villi of the serous membrane (sz); the allantois larger; embryo with month and anal opening. 5, Egg in which the vascular layer of the allantois lies close to the serous layer and has grown into the villi of the same, constituting the true chorion (ch). Yolk-sac mach smaller, about to be drawn into the cavity of the amnion, DEVELOPMENT OF ANIMALS. 649 which precede the formation of the bones of the digits and ‘limbs. The primitive skull also arises from the mesoderm. Until the sixth day it would be impossible to say whether the embryo was that of a bird, reptile, or mammal, but now the characters peculiar to birds appear. The wings and legs manifest their bird-like characters, the crop and intestinal coeca are indicated, ‘‘ the stomach takes the form of a giz- zard, and the nose begins to develop into a beak, while the incipient bones of the skull arrange themselves after the avian type. . . . From the eleventh day onward, the embryo successively puts on characters which are not only avian, but even distinctive of the genus, species, and variety ”” (Balfour). By the ninth or tenth day the feathers originate in sacs in the skin, while the nails and scales begin to ap- pear on the thirteenth day, and at this time the various muscles of the body can be distinguished. Development is thus seen to be from the general to the special, from the simple to the complex ; the trunk is first indicated ; while the peripheral parts—i.e., the extremities, the digits, the skin, feathers or scales, or hair, whatever be the type of Vertebrate—are the last to be elaborated ; in other words, the characters of the branch, class, and order are the first to be evolved, those of the family, genus, and species the last. The development of the rabbit, guinea-pig, or any mam- mal, including even man, follows much the same order as in the chick, there being, however, a well-marked morula ; the differences are due to the fact that the embryo maminal d, yolk-skin ; a’, villi of the yolk-skin ; sh, serous membrane ; 82, villi of the serous Tmembrane ; ch, chorion (vascular layer of the allantois); chz, true villi of the chorion (arising from the projections of the chorion and the sac of the serous membrane); am, amnion ; ks, head-fold of the amnion ; ss, tail-fold of the amnion ; @h, cavity of the amnion; as, sheath of the amnion for the navel-string : a, the first beginning of the embryo arising from a thickening of the outer ee of the blastoderm a’; m, thickening forming the germ in the middle layer of the blastoderm (7/), which at first only reached as far as the germinal disk, and afterward forms the vascular layer of the yolk-sac (df) which connects with the intestino-muscular layer (darmfaserblatt); st, sinus terminalis ; dd, Tene a ae layer (darmdrusenblatt) arising out of a part of 2, the inner layer of the blastoderm (afterward the epithelium of the yolk- sac); kh, cavity of the blastoderm, which afterward becomes (ds) the cavity of the olk-sac ; dg, passage way of the yolk; a/, allantois; e, embryo; 7, original space Netween the amnion and chorion, filled with albuminous fluid ; o/, anterior body-wall in the region of the heart ; hh, cavity of the heart without the heart itself. In Figs. + and 8, the amnion is, for the sake of clearness, represented as situated too far away from the embryo ; so also the cavity of the heart is drawn too small and the embryo too large; since, except in Fig. 5, they are only drawn diagrammatically.—From Kol- liker’s ‘‘ Entwickelungsgeschichte des Menschen und der hiheren Thiere.”* 650 ZOOLOGY. develops in a specialized portion of the oviducts, the uterus or womb, and that the growing germ until birth is supplied not with yolk as food, but by the nourishment in the ma- ternal blood. In fact, while the eggs of reptiles and birds are enormous, it was not known with certainty until 1827 that mammals developed from eggs. The eggs of these an- imals are very minute, owing in part to the minute amount of yolk they contain ; that of man being less than a quarter of a millimetre (4, inch) in diameter. The mammalian embryo, nourished as it is through the maternal circulation, needs additional temporary organs 3. these are the chorion (Fig. 541, ch), formed from the vitelline membrane (present in birds as well as mammals), which sends off villi or processes extending into the walls of the womb. Besides this, in the higher or placental mammals, the pla- centa or after-birth is formed, which serves as an organ of respiration as well as to supply the embryo or fetus with nourishment, and to carry off its effete products by means of the maternal circulation. It is comparatively late in embryonic life that the mam- malian features appear; in the dog it is twenty-five days before it can be told whether the embryo is a mammal or not. All mammals may be said to pass through a morula and gastrula stage. In the next stage when the nervous chord and notochord arise, the mammalian germ is on the same footing with an Ascidian larva. In a succeeding stage, when the protovertebre appear, an Amphioxus stage is reached ; when a brain is formed, the level of the fishes is reached ; after the limbs bud out the young mammals may be said to assume the condition common to the embryos of all Amphibian and higher Vertebrates. When the allantois begins to appear the amphibian feature (the want of an allantois) is dropped. When the placenta has developed the avian characters are surpassed and the mammalian feat- ures assumed. Thus the development of the individual mammal is an epitome of that of the branch or type to which it belongs, and the successive steps in the degree of specialization of the individual mammal are also paralleled METAMORPHOSES OF ANIMALS. 651 by the geological succession of the representatives of the. different classes, as without much doubt lancelets (or at least acraniate, boneless forms) were the first Vertebrates to ap- pear, and we know that fishes appeared before Amphibians, that their type culminated before the reptiles held full sway in Mesozoic times, and that birds, after them mam- mals, and, last of all, man appeared, who crowns the series of vertebrate forms. Metamorphosis._While many animals are hatched like the chick with the form of the parent, others pass through a series of changes of form called metamorphoses ; these changes of form adapt the animal to changes in its sur- roundings, involving alterations in its mode of life—slight if the change of body-form is slight, thorough-going and radi- eal if its body becomes profoundly modified. As an exam- ple of a complete metamorphosis may be cited the life-his- tories of the jelly-fishes, the star-fish, sea-urchins, sea-cu- -ccumbers, the marine-worms, the mollusks, the crustaceans, insects, and the salamanders and toads and frogs, already de- scribed in the foregoing pages. If the student will read and ‘compare these different accounts, and then consider the striking differences between the complicated histories of cer- tain species, compared with the direct mode of growth of other species of the same order or family, or even of the same genus, the inquiry will arise, What is the purpose or use of such a series of changes? If he look carefully into the embryological changes of those species which are born or hatched with the form of the adult, he will see that their embryological history is, in point of fact, a condensed sum- mary of the changes undergone after hatching by their co- ‘species, which, to gain the same adult form, have been sub- jected by nature to a series of complicated, and, at first ‘sight, superfluous changes of form and environment. Most shrimps and crabs undergo a complicated metamor- phosis ; in the different changes of forms they lead different lives, and are subjected to different surroundings, the larvae, for the most part, being free-swimming and living near the surface of the water, while the parents are stationary. The barnacle, when very young, swims near the surface of the 652 ZOOLOGY, sea, afterward, as a pupa, becoming fixed to a rock ; the young oyster-spat swims freely about, finally becoming fixed to the bottom. ‘This change of life and of form undeubted- ly tends to prevent the extinction of the species, since, if at a given moment the parents were swept out of existence, the young living in a different station would continue to represent the species. ‘This law is seen to hold good among insects, where many species are represented in the winter- time by the egg ulone, others by the caterpillars, others by the chrysalis, while still others hybernate as imagines. Again, in the marine species, the free-swimming young are borne. about by ocean and tidal currents, and in this way what in adult life are the most sedentary forms become widely dis- tributed from coast to coast and sea to sea. On the other hand, the larval forms of fixed marine animals serve as food for fishes, especially young fishes and numerous inverte- brates, while their stationary parents afford subsistence for still other forms of life ; thus were it not for the metamor- phoses of animals, many species would become extinct sooner than they do, while the great overplus of larval forms gives to many other species of animals a hold on ex- istence. Metamorphosis among the invertebrate animals, espe- cially, is perhaps the rule and not the exception. Where ani- mals develop directly, as in certain insects, crustaceans, cer- tain salamanders, toads and frogs, this is due to some change in the environment; in the case of Amphibians, perhaps the want of water, or some other cause, there always being an adaptation in the case of the direct mode of de- velopment to the surroundings of the animal and the require- ments of its existence. Parthenogenesis, and Alternation of Generations.— Having traced the normal process of development of ani- mals, we may turn to certain unusual or abnormal modes of production. Asan example of what is known as‘ alternation. of generations,’’ may be cited the mode of development of the jelly-fish, such as the naked-eved meduse (Jfelicertwm and Campanularia), which at one time of life develop by budding, at another by eggs ; of the trematode worms, the adult forms ALTERNATION OF GENERATIONS. 653 of which lay eggs, while the redia or proscolex of the same worm produces cercarie by internal budding. Here also may be cited the cases of strobilation of the Aurelia, the tape-worm, the Nais, Syllis, and Autolycus, among Anne- lids. Thusamong Celenterates and worms, as well as some Crustacea, a large number of individuals are produced, not from eggs, but by budding. Similar occurrences take place among insects, as the Aphis or plant-louse, in which a virgin Aphis may bring forth in one season nine or ten generations of Aphides, so that one Aphis may become the .parent of millions of young. These young directly develop from eggs or buds which are never fertilized, hence the term parthenogenesis, or yirgin-reproduction, sometimes called agamogenesis (or birth without marriage). The bark-lice as well as the Aphides develop in this manner during the warm wea- ther ; but at the approach of cold both male and female Aphides and Coccide appear, the females laying fertilized eggs, the first spring brood thus being produced in the normal, usual manner. Still more like the production of young in the redia of the Trematode worms is the case of the larva of a small gall- gnat (Miastor), which during the colder part of the year from autumn to spring produces a series of successive generations of larve like itself, until in June the last brood develops into sexually mature flies, which lay fertilized eggs. While the larval Miaster produces young like itself, the pupa of another fly, Chironomus, also lays unfertilized eggs. A number of moths, including the silk-worm moth, are known to lay unfertilized eggs which produce caterpillars. Among the Hymenoptera, the currant saw-fly, certain gall- flies, several species of ants, wasps (Polistes), and the honey- bee, are known to produce fertile young from unfertilized eggs; in the casc of the ants and bees, the workers lay eggs which result in the production of males, while the fertilized eggs laid by the female ant or queen bee produce females or workers. Taking all these cases together, parthenogenesis is seen to be due to budding, or cell-division, or multiplication. Now, 654 ZOOLOGY. it will be remembered that the egg develops into an animal by cell-division, so that fundamentally parthenogenesis is due to cell-division, the fundamental mode of growth; hence, normal growth and parthenogenesis are but extremes of a single series. In thisconnection, it will be remembered that all the Protozoa reproduce by simple cell-division, that among them the sexes are not differentiated, that they do not reproduce by fertilized eggs; hence, so to speak, among Protozoa parthenogenesis is the normal mode of re- production ; and when it exists in higher animals it may possibly be a survival of the usual protozoan means of stocking the world with unicellular organisms, with which we know the waters teem. And this leads us to the teleol- ogy or explanation of the czuse why parthenogenesis has sur- vived here and there in the world cf luwer organizations ; it is plainly, when we look at the millions of Aphides, of bark-lice, the hundreds of thousands inmates of ant-hills and hee-hives, for the purpose of bringing immediately into existence great numbers of individuals, thus ensuring the success in life of certain species exposcd to great vicis- situdes in the struggle for existence. That this unusual mode of reproduction is all-important for the maintenance of the existence of most of the parasitic worms, is abundantly proved when we consider the strange events which make up the sum total of a fluke or tape-worm’s biography. With- out this faculty of the comparatively sudden production of large numbers of young by other than the slow, limited process of ovulation, the species would be stricken off the roll of animal life. Dimorphism and Polymorphism.—Involving the produc- tion of young among many-celled animals (Ifetazoa) by what is fundamentally a budding process, we have two sorts of individuals. When the organism is high or specialized enough to lay eggs which must be fertilized, we have a differentiation of the animal into two sexes, male and fe- male. Reproduction by budding involves the differentia- tion of the animal form into three kinds of individuals— i.e., males, feniales, and asexual individuals, among insects often called workers or neuters. These have usually, as in DIMORPHISM. 655 ants and bees, a distinct form so as to be readily recog- nized at first sight. Among the Celenterates and worms the forms reproducing by parthenogenesis are usually larval or immature, as if they were prematurely hurried into ex- istence, and their reproductive organs had been elaborated in advance of other systems of organs, for the hasty, sud- den production, so to speak, of large numbers of individu- als like themselves. In insects, as we have stated elsewhere,* dimorphism is intimately connected with agamic reproduction. Thus the summer wingless, asexual Aphis and the perfect winged autumnal Aphis may be called dimorphic forms, ‘The per- fect female may assume two forms, so much so as to be mis- taken for two distinct species. Thus, an oak gall-fly (Cy- nips quercus-spongifica) occurs in male and female broods in the spring, while the autumnal brood of females were de- scribed originally as a separate species under the name C. aciculata. Walsh considered the two sets of females as di- morphic forms, and that Cynips aciculata lays eggs which produce (. quercus spongifica. Among butterflies, dimor- phism occurs. Papilio memnon'has two kinds of females, one being tailless, like the tailless male, while Papilio Pam- mon is polymorphic, there being three kinds of females be- Sides the male. There are also four forms of Papilio Ajax, the three others being originally described as distinct species under the name of P. Marcellus, P. Telamonides, and P. Walshii. Our Papilio glaucus is now known to be a dark, dimorphic, climatic form of the common Papilio Turnus. ‘There are dimorphic males among certain beetles, as in the Golofa hastata Dejean, of Mexico, in which one set of males are large and have a very large erect horn on the prothorax, and in the other the body is much smaller, with a very short conical horn. Temperature is also associated with the production of polymorphic forms in the temperate regions of the earth, as seen in certain butterflies, southern forms being varieties * Guide to the Study of Insects, sixth edition, p. 52. 656 ZOOLOGY. of northern forms, and alpine “‘ species’? proving to be va- rieties or seasonal forms of lowland species. For example, Weismann states that the European butterflies, Lycaon amyn- tas and polysperchon, are respectively summer and spring broods. Anthocharis Simplonica is an alpine winter form of Anthocharis Belia, as is Pieris bryonie of Pieris napi. In this country, as Edwards has shown, two of the polymorphic forms of Papilio Ajax—i.e., Walshii and Telamonides—come from winter chrysalids, and P. marcellus from a second. brood of summer chrysalids. It thus appears that poly- morphism is intimately connected with the origin of species. Perhaps the most remarkable case of polymorphism is to be seen in the white ants (Zermites), where in one genus there- are two sorts of workers, two sorts of soldiers, and two kinds. of males and females, making eight sorts of individuals ; in the other genera there are six. Among true ants there are, besides the ordinary males, females, and workers, large-- headed workers. In the honey-ant (Myrmecocystus Mexi- canus), besides the usual workers, there are those with: enormous abdomens filled with honey. Other insects, es-. pecially certain grasshoppers, are dimorphic. Certain par- asitic Nematode worms are dimorphic; and among the- Celenterates, especially the Hydroids, there is a strong ten- dency to polymorphism. Individuality.—Perfect individuality among animals is. the rule, each individual being capable of maintaining an. independent existence ; but we have seen that there are many of the lower animals in which it is difficult to determine whether the different members of a colony are really in- dividuals or simply individualized organs. The student, in referring back to the account of the Por- tuguese man-of-war, will find it difficult to say whether the four kinds of members of the floating colony are organs or individuals, and he will probably agree with the view that it is hest to provisionally call them zooids or individualized organs ; for the feeders, the reproductive zooids, the digest- ive zooids, and the swimming float, or the swimming bells of the other Siphonophores, are highly specialized organs, and only differ from true individuals in lacking the power INDIVIDUALITY AND HYBRIDITY. 657 of free motion and of maintaining an independent existence. So with many other Celenterates and with the tapeworm, whose proglottides or segments are finally capable of sepa- rate existence. Among the higher invertebrates, even the different members of a colony of white or true ants lack a. certain amount of individuality, the workers performing labors upon which the maintenance of the very existence of the colony depends, so that there are different grades of in- dividuality, from examples like the Hydractinia and the. Siphonophores up to those insects which live socially ; and we see that the most perfect individuality exists in those animals which can most efficiently provide for their own sustenance and for the continuance of their species. Hybridity.—It is rare that two species, even of the same genus, can produce offspring ; when such cases occur. the result is called a hybrid. For example, the mule is a hybrid, being bred from a female horse and an ass; but the mule is not fertile, and hybrids are very rarely fertile. The In- dian dog and coyote are said by Coues to interbreed, and on the Upper Missouri we have seen dogs which had every appearance of being such hybrids. Dogs also cross with the fox (Darwin). The American bison is known to breed with the domestic cattle, and it seems to be a well-established fact that the hybrids are fertile. Fish readily hybridize. Darwin states that he knows of no thoroughly well-au- thenticated cases of perfectly fertile hybrid animals, though he adds, ‘‘I have reason to believe that the hybrids from Cervulus vaginalis and Reevesii and from Phasianus col- -chicus with P. torquatus are perfectly fertile.’’ The hare and rabbit are supposed to have fertile offspring ; the hy- brids of the common and Chinese geese (Anser cygnoides) are fertile. The crossed offspring from the Indian humped and common cattle interbreed. Caton has hybridized the Virginia deer with the Ceylon deer and the Acapulco deer ; “* the hybrids seem perfectly healthy and prolific.” Among insects over 100 cases of hybridity have occurred. Hybrids between the brown and polar bear, the leopard and jaguar, Equus onager and EL. hemippus, EF. burchelli with the com- mon horse, and with the common ass and Z. hemionus ; have been raised. CHAPTER XI. THE GEOGRAPHICAL DISTRIBUTION OF ANI- MALS. THE assemblage of animal life peopling any one locality or area is called its fawna, as the plants of a place consti- tute its flora. Where the physical geography—.e., the con- tour of the surface, the plains, valleys, and hills—is of iden- tical character and the climate the same, the fauna is much the same, but when these characteristics of soil and climate change, as in passing from lowlands to highlands, or from south to north, the assemblage of animals will be found to change in a corresponding ratio. And as there are no definite limits to any large area of the earth’s surface, the physical features of one area merging insensibly, as a rule, into adjoining districts, so adjoiing faune merge into one another, and a certain proportion of the species may range through two or more faunal areas. There are in nature causes tending to restrain animals within their faunal limits, and others tending to diffuse them, or to cause them to migrate from their specific cen- tres or centres of creation—namely, the point where the in- dividuals of a species are most abundant, and where, ac- cordingly, they are supposed to have originated. Barriers to the Spread of Animals from their Specific Centres._Among the most important are the oceans and their basins. The animals of the opposite sides of the Pa- cific Ocean are entirely unlike, no species being common to the two sides; while, of the immense numbers of animals peopling the coast of Brazil and the opposite coast of Af- rica, only two or three are known to be identical. Differ- ence in climate is also a great barrier, the animals of the GEOGRAPHICAL DISTRIBUTION. 659 tropics, as a whole, being unlike those of the temperate zones ; while arctic and antarctic animals have features in common. Mountains serve as most important barriers, re- straining animals within their limits; thus the basins be- tween or surrounded by continuous ranges of mountains harbor faune differing from those on the opposite sides of the mountains. For example, the majority of the animals of the Great Basin between the Rocky Mountains and the Sierra Nevada differ from those of the Pacific slope or the prairie lands lying east of the Rocky Mountains, as the meteorological and geological features are different. The Cordilleras of South America form a barrier to the diffusion westward of Brazilian animals. Still this fact is not to be taken too literally, as the mountains are divided by valleys and rivers, which afford means of communication and an interchange of specific forms; thus certain species of ani- mals of the Rocky Mountain plateau occur on each side of the range, as do those in the Alleghany district of the At- lantic coast. In the West Indian and especially the Hawa- iian Islands, where the species of land snails are very numer- ous, certain forms are restricted to the deep narrow valleys, being confined to very restricted areas. So also the cold Alpine summits of the White Mountains of New Hamp- shire, of the Rocky Mountains, of the Alps and Scandina- vian mountains harbor a few species either peculiar to those extremely limited tracts or found northward in the Arctic regions. Deserts may act much as inland seas to separate the ani- mals of the adjoining more fertile tracts, and they afford dwelling-places for animals which are incapable of living elsewhere. Desert faune have a general facies the world over, though the original elements out of which the faune have been made up may radically differ. The distribution of plants also has much to do with that of those animals which are dependent on them for food ; as a rule, the distribution of both plants and animals de- pends on the same physical causes. Large rivers sometimes act as barriers, but more often, perhaps, aid in the diffusion of the smaller forms, such as 660 ZOOLOGY. insects, mollusks, and crustaceans. Different systems of riv- ers have distinct sets of fluviatile animals ; for example, the fishes of the Ohio and Upper Mississippi and its tributaries differ from those of the Hudson River and the New England rivers, and the latter from those draining the Southern At- Jantic States. The fresh-water mussels, so abundant and characteristic of the waters of the Mississippi and its tribu- taries are confined to the region lying west of the Allegha- nies and east of the Great Plains. The fishes and mollusks of the rivers of the Pacific slope differ from those of the scanty waters of the Great Basin. Means of Dispersal._The most general are the alterna- tions of winter and summer, leading birds and mammals to migrate great distances to and from their breeding-places. -Ocean-currents are most important factors in the dispersal of many marine and some land animals. By means of such great currents as the Gulf Stream, tropical animals are borne ‘to temperate and even subarctic regions ; and, on the other hand, arctic and temperate animals are borne southward, and thus marine faune interdigitate and merge insensibly into one another. By this agency also new coral islands are peopled from the mainland, and peninsulas are colo- nized from adjoining continents or islands ; for example, the southern extremity of Florida has been visited by trop- ‘ical plants and animals borne by currents and winds from ‘the West Indies, thus lending a purely tropical aspect to the southern part, a semi-tropical fauna occupying the mid- dle and northern part of the State. Trade winds play an important part in scattering insects, and especially the minute forms of life ; whirlwinds and tornadoes catch up larger forms and transport them from stream to stream, pond to pond, and from lowlands to highlands, and even to Alpine summits, where may some- times be found, under loose stones, multitudes of insects which have been borne up from below by strong gales or ascending currents of air. The direction of the migrations of the Rocky Mountain locust seems to be mainly dependent on the direction of pre. vailing winds. Insects as well as birds are blown off-shore GEOGRAPHICAL DISTRIBUTION. 661 ‘sometimes for hundreds of miles, and in this apparently haphazard way islands are, in part at least, supplied with ‘their quota of animal life. Great rivers, like the Missouri, Mississippi, and the Ama- zons, afford means of transportation from one part of a con- tinent to another, from the interior to the seaboard, of which many fishes, insects, and especially fluviatile mollusks, avail themselves. Artificial means of crossing broad rivers are offered, to insects especially, by country-roads and bridges and railroad bridges, of which the potato-beetle and the -cabbage-butterfly have fully availed themselves. The Colo- rado beetle has advanced steadily eastward, suddenly ap- pearing in isolated points in New England, having appar- -ently been transported by through grain-cars from Chicago, ‘and has been carried to Europe in vessels. The European -cabbage-butterfly introduced into Quebec spread southward into Maine along the Grand Trunk Railroad, into New York along the railroads from Montreal to New York, and then along the railroads to Washington. Geological changes, such as the rise and submergence of ‘the edges of continents, and also the incoming and wane of ‘the glacial period, were still more general and fundamental means of the dispersal and rearrangement of faune. Division of the Earth into Faune.—When we go from Maine to California we shall find that the faunistic features -of the country radically change three times. Leaving the moist, temperate, forest-clad Atlantic region with its char- -acteristic animals, and entering on the broad, treeless, dry, elevated plateau of the Rocky Mountains, we shall notice that the Atlantic fauna has been replaced almost wholly by ‘anew and strange assemblage ; and when we descend the Pacific slope of the Sierra Nevadu, there will be found to be a second replacement, though much less marked than the first. Again, when we pass from Labrador to the Isthmus of Panama, we shall find several distinct faune, from an arctic one to a purely tropical one. If we pause at Wash- ington and analyze the fauna of that point, we shall see that it is made up mainly of animals common to the Middle Atlantic States, with an infusion of northern and southerr. 662 ZOOLOGY. forms. Indeed, at almost any point in temperate North America the fauna is found to consist of three elements— 1.€., mainly a temperate, with a certain percentage of boreat or subarctic and of southern or semi-tropical forms; and if the point be situated near some lofty range of mountains, a fourth element—i.e., a purely arctic or alpine feature—is superadded. The earth’s surface may then be mapped out into general and special divisions. First, a tropical, tem- perate, and arctic or circumpolar fauna or realm, and, sec- ondly, each continent may form asmaller subdivision or spe- cific centre—i.e., the Europeo-Asiatic, the African, the Aus- tralian, and the South and North American regions, for each of these continental divisions have been peopled with animals which have been from the earliest geological times the original possessors of the soil, though they may have adopted members of each other’s faune. Contfining ourselves to the North American Continent, let us examine the distribution of life on its surface. We shall have to throw out the arctic regions, which belong with the arctic regions of Europe and Asia, to a distinct circumpolar fauna or realm, and then map out the rest of the continent into five provinces—i.e., the Canadian, the Alleghanian, the Central or Rocky Mountains, the Pacific or Californian, and the Jfecican ; all of these provinces are bounded by natural geological limits and differ in tempera- ture and moisture. While the cougar, or Felis concolor, is common to each one of them, and the bison and black bear range throughout the Canadian, Alleghanian, and Central provinces, there is a certain percentage of animals which are confined to each province ; and on closer examination, each province, especially on the Atlantic and Pacific coasts, will be found capable of minuter subdivision into more lo- cal faune or faunule. It will also be found that the animals, especially the insects, of the Atlantic province have certain elements reminding us of Northeastern Asia, while on the Pacific slope—i.e., the Californian province, a few insects, shells, and crustacea, as well as the birds, remind us of European types, which are wholly wanting east of the Rocky Moun- tains. GHOGRAPHICAL DISTRIBUTION... 663 On inquiring into the origin of the North American fauna, in the light of the geological history of the conti- nent, we shall find, first, that immediately preceding the glacial period, Arctic America was peopled by a flora and fauna of which the larger proportion of the animals of the continent north of latitude 30° are probably the descend- ants ; and, second, that a number of species migrated north- ward from the South American Continent. Now, when the glacial period came in, the semi-tropical and warm tem- perate animals of the northern two-thirds of the continent were mostly swept out of existence ; a scanty arctic fauna took their place ; as the ice melted and retreated to its pres- ent limits, the present assemblage of temperate animals, mostly modified descendants of those originally driven south, migrated back again and colonized the region laid compara- tively. bare by the ice and cold of the glacial period. This is an illustration of the sweeping extinctions, recolonizations, and extended migrations of animals on our continent in former times, by which the existing relations of faune have been brought about. Parallel events have occurred on the Europeo-Asiatic Continent, and thus geological extinctions and widespread migrations and recolonizations have taken place ; and it is only in this way that the existing relations in the geographical distribution of animals as well as plants can be accounted for. It should also be observed that in the beginning of things the continents were built up from north to south— such has been at least the history of the North and South American and the Europeo-Asiatic and African Conti- nents; and thus it would appear that north of the equator, at least, animals slowly migrated southward, keeping pace, as it were, with the growth and southward extension of the grand land masses which appeared above the sea in the Pa- leozoic Age. Hence, scanty as are the arctic and temperate regions of the earth at the present time, in former ages these regions were as prolific in life as the tropics now are, the latter regions, now so vast, having all through the Tertiary and Quaternary ages been undisturbed by great geological revolutions, and meanwhile been colonized by emigrants driven down by the incoming cold of the glacial period. 664 ZOOLOGY. It appears, then, that each continent has had from the first its distinct assemblage of life, and thus opposing con- tinents, such as South America and Africa, have fundament- ally different faunze, because they have had a separate geo- logical history. Though the climate, moisture, and exteut of forests of Brazil and the West Coast of Africa may, for example. be nearly identical, the animals are of a different type. At the present day, Australian trees may be trans- planted to California, and flourish there, and camels from the Orient may breed in Southern California, because at the present day the climate and soil are so much alike in the two countries. Distribution of Marine Animals.—Nearly all that has been said thus far applies to land animals. Marine species are assorted into faunz which are nearly as well marked as terrestrial assemblages of species. The barriers restraining them within their faunal limits are the temperature of the water, this being modified more or less by the ocean-cur- rents. the nature of the shore, whether rocky or muddy or sandy, and the nature of the sea-bottom, whether also rocky, muddy, or sandy. Many marine animals live attached to rocks and stationary pebbles, others are found only in coarse or in fine sand, while the muddy bottoms of harbors, bays, and gulfs, or the soft, deep ooze of the ocean-depths harbor a different assemblage of mud-loving species. The temperature of the water is the most important agency now in operation in the limitation of marine animals. Thus there is a tropical, north and south temperate, an arctic and probably an antarctic zone, and these are, along the shores of the different continents, subdivided into distinct faune. For example, along the coast of Eastern North -\merica, the arctic or cireumpolar fauna extends from the polar regions to Labrador and Newfoundland ; a second, the Acadian, to Cape Cod; between Cape Cod and Cape Hatteras another assemblage (the Virginian) is found ; from Cape Hatteras to Southern Florida a fourth, and the Flor- idan peninsula belongs to the tropical regions. Along these different areas the water is of different temperatures. We also find a large proportion of cireumpolar animals in the GHOGRAPHICAL DISTRIBUTION. 665 Acadian fauna and a few in the Virginian fauna, as the Labrador or polar current passes down along the coast, bathing the New England coast north of Cape Cod, and even extending under the warm surface- water as far as New Jersey. On the other hand, the great volume of heated tropical water forming the Gulf Stream issuing from the Straits of Florida makes its influence most sensibly felt as far as Cape Hatteras, and in a diminished degree to Cape Cod, and even southern shells, etc., are found as outliers of more southern faune near Portland, Me., and Nova Scotia. As we descend from the shore into deep water, the tem- perature becomes lower and lower the decper we go, until we come toa stratum or zone of water about 32°-36° Fahr., where circumpolar or arctic life alone abounds. Wherever ‘deep abysses off the coast or at the bottom of bays or gulfs occur, the water is found to be colder than elsewhere ; just as when we ascend a mountain the air becomes colder, un- til at the Alpine summits we find an arctic temperature and fauna; thus, in the sea, increase of depth is paralleled by increase of height on land. Usually, off the coast of the United States, north of New ‘York, there is a distinct zone of life between high and low water, a second extending to the depth of about fifty fathoms, anda third to one hundred fathoms or over. Ata depth of from one or two hundred fathoms in the Northern Atlantic, and from five hundred to one thousand fathoms in the sub- tropical and tropical seas, down to the deepest parts of the ocean, now known in a few points to be about five miles in depth, the water is about 32° Fahr. and the animal life is polar in its nature. The water of the ocean all over the globe, as shown by the results of the ‘‘ Challenger’’ and other expeditions for the exploration of the sea at great depths, everywhere below a depth of one thousand fathoms, is of an arctic temperature, overlaid by the heated water of the tropics. The abysses or deeper parts of the ocean-bed support a nearly uniform assemblage of life, which may be called the deep-sea or abyssal fauna. The animals largely consist’of Echinoderms, notably Crinoids, with Coelenterates, mollusks, worms, and Crustacea, and it is an interesting fact 666 ZOOLOGY. that a few of the Echinoderms belong to genera which flour- ished in the Cretaceous Period ; so that in a sense the abys- sal fauna may be said to be an extension in time of the Cretaceous fauna; the physical features of the deeper parts of the sea having remained nearly the same, while the shallower parts have risen and fallen so as to undergo great changes, and have wrought corresponding changes in the life along the shores of the continents. The following tabular view of the chief zoological faunas of the earth, proposed by Mr. J. A. Allen, is based on a study of the mammals, but will primarily apply to most land animals. The arctic realm is most distinctly charac- terized by the distribution of marine invertebrates, where 1t becomes of primary value : I, Arctic realm, undivided. Il. North Temperate realm, with two regions, viz. : 1, American region, with four provinces, viz.: a. Boreal, b. Eastern. ce. Middle. d, Western. 2. Europzo-Asiatic region, also with four provinces, viz. : a. European. 6. Siberian. c. Mediterranean. d. Manchurian. III. American Tropical realm, with three regions, viz. : 1. Antillean. 2. Central American. 8. Brazilian, TV. Indo-African realm, with two regions, viz.: 1, African region, with three provinces, viz. ; a. Eastern. b. Western. e. Southern. GHOGRAPHICAL DISTRIBUTION. 667 2. Indian region, with two provinces, viz. : a. Continental. 6, Insular. V. South American Temperate realm, with two provinces, viz.: a. Andean, 6. Pampean. VI. Australian realm, with three regions, viz. : 1, Australian, with two provinces, viz. : a, Australian, b. Papuan. 2. Polynesian. 3. New Zealand, VII, Lemurian realm, undivided. VIII. Antarctic or South Circumpolar, undivided. Migrations of Animals.—Intimately connected with zoogeog- raphy are the migrations of animals, especially birds. Nearly all the birds of the United States which breed in the central and northern portions pass southward in the autumn, and winter in the Southern States or in Central America and the West Indies. Most of the birds which breed in Northern and Central Europe fly at the approach of cold weather into Southern Europe or across the Mediterranean into Northern Africa. The causes of this regular periodical migration are probably due, primarily, to the changes of the seasons and to the want of food in the colder portion of the year, and, secondarily, to the breeding habits of birds. The periodical migrations of fishes from deep to shoal water are connected with their breeding habits, the marine fish being in most cases compelled to spawn in rivers or in shoal-water. The migratory movements of fishes along the coast are probably connected with the presence or absence of their accustomed food. ; The partial, occasional migrations of locusts depend on the undue increase in the numbers of the insects, and the consequent lack of food, while the direction of the swarms is largely dependent on the general course and force of the winds, CHAPTER: x11, THE GEOLOGICAL SUCCESSION OF ANIMALS. THE different systems of rocks, from the Silurian to the Quaternary or present age, contain the fossil remains of ani- mals, which show that in the beginning the animals were, as a whole, unlike those now living, the later types becom- ing more and more like those now constituting the earth’s fauna. The oldest set of animals, the Paleozoic, comprised species of nearly all the branches of invertebrates, with a few fishes. A large proportion of these animals belonged either to simple or to what are called generalized types, though some were as specialized as any invertebrates now living. Progress upward has involved the disappearance of most of the generalized types, and their replacement by more or less highly specialized types. Thus the earliest corals were mostly of the Rugose type, which were succeeded by the more complicated recent forms ; the Brachiopods or shelled worms were replaced by mollusks ; the generalized trilobites gave way to the genuine specialized shrimps and crabs ; the existing generalized king-crab, with its affinities to spiders, has survived a number of stili more generalized or synthetic allies. The generalized sharks and ganoids abounded at a time when there were no bony fishes like the cod and her- ring. Nearly nine thousand species of bony fishes have appeared since the extinction of the earlier types of cartila- ginous and mail-clad fishes. The highly specialized horse was preceded by a number of more generalized species and genera, the oldest of which approached the tapir, one of the most generalized of mammals. The succession of forms leading up to the horse is paralleled by the succession of GHOLOGICAL SUCCESSION OF ANIMALS, 669 sea-urchins and of ammonites, the older being of simpler, more generalized forms, and the later with a greater specialization or elaboration of the different, especially ex- ternal, hard parts of the body. When we ascend to the Amphibians, the reptiles and the mammals, we shall find that there has been an elaboration or working out into great detail, of the parts most used by the animal, this differentiation being more and more marked as we approach the present time; and this has been in ac- cord with the building up of the continental masses, and the differentiation or specialization of the surface of the different continents into plains, plateaus, highlands, and mountain ranges, with their different climatic features, and the dividing up of the waters into mediterranean seas, friths, fiords, rivers, and lakes. Thus the extinction of successive faune all over the globe has been followed by the appearance of new sets of animals, each assemblage be- ing adapted to the new and improved condition of things. Having seen that the earlier forms of life were of a sim- pler form, though often combining the features of diverse classes and orders of animals which appeared afterward, so that Agassiz called them, in some cases, prophetic types, combining as they did characters which have been trans mitted to two or more later groups, and these specially elab- orated, so that such generalized or prophetic types serve as points of departure from which severai series of forms have arisen—having traced the law or principle underlying the geological succession of animals, we may inquire whether this has been paralleled by the development of any one of the members of a group. That this is the case has been proved by Hyatt, who shows that the development of the individual Ammonite is paralleled by that of the geological succession of the members of the order to which it belongs. Stalked Crinoids were the style in Paleozoic ages, while free Crinoids are more abundant at the present day ; and we have seen that in the individual development of the existing Antedon, the young is stalked at first, afterward becoming free. The young, bony fish has at first a cartilaginous skeleton and a heterocercal tail, these being characteristics 670 ZOOLOGY. of early fishes. The earlier Batrachians were tailed, the tailless toads and frogs in general appearing last, as the tadpole precedes the frog condition. Extinction of Species.—The laws governing the extinction of animals are obscure, but we know that geological extinc- tions must have been due to natural causes, since the earth has at different periods evidently undergone great changes, sufficient to account for the death of such species as were unable to withstand the oscillations and changes of climate. In Paleozoic times existed multitudes of animals which, judg- ing by their descendants of later times, belonged to old-fash- ioned, obsolete, useless types. They cumbered the ground, and were destroyed by the beneficent action of unerring natu- ral laws promoting the decay and extinction of antiquated forms, and the recreation, by the laws of transmission with modification, of new, improved types, useful in their day and generation as stepping-stones to a still higher, more improved stock. That the extinction was due to causes acting pri- marily from without, and secondarily from within by trans- mission force, seems demonstrated when we take into ac- count the destruction of life which we know took place during and at the close of the Glacial Period, when the earth was swept with glaciers, and afterward garnished with the vegetation and fresh life of the post-glacial times, and made ready for the abode of man. Thus the death of species by the action of laws that we can comprehend in- volves the recreation of new and improved animal forms by laws that we can at least in part, if not fully, understand. CHOAPTER AI, THE ORIGIN OF SPECIES. THE extinction of species was in some cases gradual, in others sudden, so in all probability as different assemblages of life became slowly extinct new forms as slowly originated from them by genetic descent and took their places. While here and there certain species, under favorable circumstances, suddenly appeared, if we could have been there to look on, it would perhaps have been as difficult to have observed the process as it is at the present day to observe the changes going on in the relation of existing faune. We know, however, that changes are going on in the world of life about us, that the balance of nature is being disturbed. The nature of the evidence tending to prove that species have originated through the agency of physical and biologi- cal laws is mainly circumstantial, there being comparatively few facts in demonstration of the theory, the direct act of transformation of one species into another under the eye of scientific experts having never been observed. Reasoning @ priori, we assume that organisms, both plant and animal, have been created by development from pre-existent forms because it agrees with the general course of nature. All the events in geology, as in physics and as- tronomy, being due to the operation of natural laws, it is reasonably supposed that the production of all the species of plants and animals from original simple forms, like the Monera or bacteria, have been the result of the action of natural law. The study of the early forms of life found in the Paleozoic strata ; the laws of the succession of types ; the correlation existing between the development of the indi- 672 ZOOLOGY. vidual and of the members of the class to which it belongs ; the parallelism between the formation and differentiation of the land-masses of the globe and the successive extinc- tions and creations of plants and animals—all these facts, notwithstanding the imperfections of the geological record, and the fact that many of the older forms of animals were nearly as much specialized as those now living ; tend strongly to prove that, on the whole, the world as it now exists has. been the result of progressive development, one form com- ing genetically from another ; the animal and plant worlds constituting two systems of blood relations, rather than sets of independent creations. When to more special studies of those species which live in extraordinary environments, such as cave-animals, para- sitic animals, brine-inhabiting animals, Alpine forms and certain deep-sea species, we add the study of rudimentary organs in adult aniinals, of temporary, deciduous organs in young or larval animals; when we compare the metamor- phoses of some species congeneric with others which undergo no transformations ; when we study the delicate balance ju nature as observed in the geographical distribution of ani- mals ; the harmony in nature between species and their en- vironment ; protective coloration and resemblance in form, the relations between carnivorous and herbivorous creatures, the struggle for existence between animals, we are forced to acknowledge that the operations of nature, as a whole, tend, on the one hand, to the origination of new forms and the preservation of those which are useful, or, in other words, arein harmony with their surroundings ; and, on the other hand, to the destruction of those which are incapaci- tated by changes in their environment for existence in what has been and now is a constantly changing, progressive world. Again, reasoning by induction, as an actual fact we know that species vary ; that hardly any two experts agree exactly as to the limitation of species ;* that varieties tend to break * As one of many examples, we may cite the fact that fifty-nine nom- inal species of the squirrels have been described as inhabiting tropical America, but lately the number has been reduced to twelve. THE ORIGIN OF SPECIES. 673 up into races, and that no two individuals of a race are ex- actly alike. Where the climate and soil remain the same, the species tends to remain fixed and stable ; remove the stability in the environment, or subject the individuals of a species to changes of soil and temperature, and expose it more than usual to the attacks of its natural enemies, it then begins to undergo a change. This is seen in those in- dividuals of a species which live on the borders of lowlands and highlands, of deserts and fertile tracts, of salt and brackish water, of shallow and deep water, and of polar and temperate zones, or to the influence of alternating cold and warm weather. When, as in some cases, climatic or other agencies suddenly change, we may have species and even genera suddenly appearing, as is known to be the case in the change of one genus to another of brine shrimps when the water changes from brackish to a brine, as worked out by Schmankevitch in Russia. The struggle for existence resulting in the survival of the fittest is a fact now generally observed. The cod may de- posit several millions of eggs, but of this immense number only one or a few pair of adults survive ; there are probably no more codfish now than two centuries since—indeed, not as many; the eggs are devoured by different animals, the young fish, as soon as hatched, form the food of larger fish, half-grown cod serve to supply the wants of larger animals, until finally the survivors may be to the original number of eggs as one to a million. The queen bee may, during her whole life, lay more than a million of eggs, the queen white ant may lay eighty thousand eggs a day, an Aphis may be the mother of a hundred young, those hundred may each produce their centesimal offspring until the result in one season, at the end of the tenth generation, amounts toa quintillion of plant-lice ; but most of these insects serve as food for other species, many die of disease and cold, until at the end of the season only one or several pairs survive to lay a few eggs, which represent the species in the winter-time. Lastly, the variation in domestic animals, the result of the subjection of the species to influences not felt in what we call a state of nature, is an indication that animals not 674 ZOOLOGY. exposed to human interference may vary when subjected to changes in their environment. Also the fact that man can, by careful selection, breed races of horses adapted for draught, speed, or the road ; races of cows for different qualities of milk ; beeves for meat ; races of sheep for pre-eminence in the quality of their wool or mutton, or races of doves or poultry for beauty, usefulness, or other qualities ; the fact that gentleness, and generally good mental qualities, can be made to replace viciousness in horses, cattle, dogs—all these and many other facts, in the art of breeding animals known to fanciers, indicate that nature has, through the past ages, by the operation of natural laws, evolved races and species of animals which have followed constantly improving lines of development, the outcome of which are creatures the best fitted to withstand the struggle for existence, the most use- ful in the scheme of nature, and the mest in harmony with the world about them. Progress, on the whole, therefore, has been beneficent, the best proof of which is the last product of evolution, man, the paragon of creation. CHAPTER XIV. PROTECTIVE RESEMBLANCE. CLosELy related to the foregoing subjects is the protective resemblance or ‘‘ mimicry’’ of natural objects by which spe- cies of animals are preserved from extinction. Animals may **mimic”’ or imitate, or be assimilated in shape or in color to natural objects, as stones, lichens, dry bushes, the bark of trees, or portions of leaves, or entire leaves, fresh or dried, and their stems, or so closely imitate other animals which enjoy an immunity from attack as to escape notice or attacks from their enemies, and thus prolong their own lives and that of their species. The animal is, as a rule, unconscious that it is thus pro- tected ; though there are examples, as in the case of the trap-door and other spiders, which cover their holes in such a way to avoid notice that it would appear as if they were semi-conscious or aware of what they were doing. In the first place, we know that animals may be deceived, as is proved by the various subterfuges employed by hunters in tolling or deceiving the larger quadrupeds, the use of decoy- -ducks, by which water-fowl are often thoroughly de- ceived and brought within reach of the gun. The disguises worn by animals, the exquisite adaptation of the colors of their fur or feathers to their surroundings, are part of the general harmony existing throughout nature. Desert animals are rusty or light-colored ; birds and insects and lizards, as well as frogs and tree-toads, which live among trees, are green; those which live among the trunks and larger branches of trees assimilate in color to the color of the bark. The cougar, which clings to the trunk of some 676 ZOOLOGY. tree, prepared to spring upon the deer passing underneath, 13 protected from observation by its brown neutral color, while the bars and lines of the tiger are said to resemble the lights and shades of the jungle grass in which it lies in wait for its prey. The prairie-dog, the deer, buffalo and ante- lope on the Western plains, are concealed by their resem- blance in color to the soil, or to the bushes on its surface. Among insects, the grasshoppers nearly always harmonize in color with the general hue of the fields in which they abound ; insects on light-colored sandy beaches are often pale, as if bleached out by the sun’srays. Alpine and arctic butterflies and moths, which have limited powers of flight, when nestling on lichen-covered rocks, are difficult to detect. Fig. 542 —A Katydid-like form resembling a leaf. Certain orthopterous insects resemble leaves; such are certain katydids (Fig. 542), and especially the famous leaf- insect, Phyllium siccifolium Linn. ‘Fig. 542), which strik- ingly resembles a green leaf. The stick-insects (Fig. 544 also would be easily mistaken for the twigs of trees or stalks of leaves, one species ‘Fig. 544) representing & moss-grown twig. The under sides of the wings of our native Grapta butterflies have the color of dead leaves. so that when they are at rest they resemble a withered dry leaf. The most perfect resemblance to a leaf with its stem is the Aallima butterfly when setting at rest with its wings folded over its PROTECTIVE RESEMBLANCE. 677 back. The caterpillars of the geometrid moths often won- derfully mimic the stems of the plants they feed upon, in color and markings, even to the warts and tubercles on their skin. As an example of possibly con- scious mimicry or effort at conceal- ing their nest from the search of their enemies, may be cited the trap- door spider observed by Moggridge in Southern Europe. This spider digs its hole among moss and small ferns, and after the trap-door is made the top is covered with growing Fig. 513.—Leaf insect (Pay- ferns, etc., transplanted by the spider, and the deception is so perfect that Mr. Moggridge found it difficult to detect the position of the closed trap, even when holding it in his hand. ium), Half natural size. Mimicry of other insects is of very frequent occurrence, certain flies resembling bees in appearance and the sounds or buzzing they make; the Syrphus flies closely imitate wasps. Fig. 545 illustrates case observed by Belt in Nicara- gua, where a wasp (Priocnemis) is mimicked by a hemipterous insect (Spiniger luteocornis Walker, the left-hand figure) in every part, even to its vibrating, brown, semi- transparent wings and its wasp-like motions. Here the bug is evidently protected by its resemblance to the wasp, for whose ferocity and sharp sting all unarmed insects have great respect. Some butterflies are distasteful to birds, and there are other but- Fig. 544.Stick insect. terflies which have no bad taste, but closely resemble in color such species as are passed over by birds. Thus, 678 ZOOLOGY, Danais archippus, a common large butterfly, is not eaten by birds on account of its pungent odor, which is disagree- able to them. Another butterfly, Limenitis disippys, @ smaller but similarly colored butterfly, which is inodorous, is supposed to be mistaken by the birds for the Danais, and thus escapes destruction. Belt says that in Central America stinging ants are not only closely copied in form and movermenis by spiders, but by species of Hemiptera and Coleoptera; as stinging anta are not usually eaten by birds, this disguise ig thought to protect the various forms which imitate them. Many highlv-colored caterpillars, which live exposed on the leaves of plants, are ust eaten by birds, owing to their bad taste. This and other bright-colored insects may be said Fig. 345.—_Wasp mimicked by a bug.—After Belt. to hang out danger- signals to warn off hungry birds. Mr. Belt, in his ‘* Naturalist in Nicaragua,” suggests that the skunk is an example of this kind. ‘‘Its white tail, laid back on its black body, makes it very conspicuous in the duzk when it roams about, so that it ig not likely to be pounced upon by any of the Carnivora mistaking it for other night-roaming animals.’” He also cite: the case of a very poisonous. beautifully banded coral snake (F7ops1. which is “marked a: conspcuouel as any noxious caterpillar with bright bands of black. yellow, and red.’’ This author alzo found that while the frogs in Nicaragua are dull or green- colored, feeding at night. and all preyed upon by snakes and birds, one little species of frog, dressed in a bright liv. PROTECTIVE RESEMBLANCE. 679 ery of red and blue, hops about in the day-time, and, as he proved by experiment, is thoroughly distasteful to fowls and ducks. We have seen that many animals resemble externally those above them in the scale of life ; in the synthetic or general- ized types from which the more specialized forms have prob- ably originated, there are characters which cause them to resemble more recent, new-fashioned types. It is possible that in many cases the older types, doomed as they were to destruction, have had their existence prolonged by their protective resemblance to modern types. For example, the Neuroptera as a group are geologically of high antiquity ; owing to geological extinction, but few species, compared with those of other orders, have survived ; and those which are now living often resemble members of higher, more recent orders. The inference is, then, that the mimickers have survived by reason of their resemblance to the more abundant forms which appeared, as the more old-fashioned types were waning or dying out. Certain Brazilian species of the lepidopterous family, Zygenide and Bombycide, mimic in form and coloration certain butterflies, especially the Heliconide, which abound in Brazil. The former groups are evidently the older geo- logically, as there are wide gaps between the genera; and the indications are that these butterfly-like moths have likewise, from their resemblance to the more abundant Helv- conide, been preserved. It thus appears that protective mimicry may be an important factor in the preservation of species, CHAPTER XV, INSTINCT AND REASON IN ANIMALS. We have seen that animals have organs of sense, of per- ception, in many cases nearly as highly developed as in man, and that in the mammalia the eyes, ears, organs of smell and touch differ but shghtly from those of our own species ; also that the brain and nervous system of the higher mam- mals closely approximate to those of man. We know that all animals are endowed with sufficient intelligence to meet the ordinary exigencies of life, and that some insects, birds, and mammals are able, on occasion, to meet extraordinary emergencies—in other words, to rise with the occasion. These occurrences indicate that what usually goes by the name of ‘*‘instinct’’ is more or less pliable, unstable ; that animals are ina limited degree free agents, with powers of choice. Moreover, those naturalists who observe most closely and patiently the habits of animals do not hesitate to state their belief that animals, and some more than others, possess reasoning powers which differ in degree rather than in kind from the purely intellectual acts of man. As a matter of not infrequent observation, animals exer- cise the power of choice, they select this or that kind of food, prefer this or that kind of odor, and have their likes and dislikes to certain persons, and all this aside from mere physical stimulation of the senses. Moreover, animals are subject to the passions, they show anger, even when not hungry or under the domination of the reproductive in- stincts ; their sounds express dissatisfaction or contentment. Indeed, many facts could be stated showing that animals INSTINCT AND REASON. 681 not only have feelings, intelligence, and volition, but are possibly, in a very slight degree, self-conscious. The fact that animals exercise discrimination in the selection of food, in the choice of a flower or object of one color in preference to unother, in perceiving likeness or unlikeness in two objects, indicates that they can exercise the power of intelligent discrimination, as has been said by Mr. G. H. Lewes :* ‘‘ When there is no alternative open to an action it is impulsive ; when there is, or originally was, an alter- native, the action is instinctive ; where there are alterna- tives which may still determine the action, and the choice is free, we call the action intelligent.’’ Indeed, animals have the principle of similarity strongly developed. It is the bond that holds together the social or- ganizations of such insects as live in colonies, and such fish, birds, or mammals as go in schools, flocks, or herds. Were it not for this mental quality some species would tend to die out. Animals possess memory, which consists in storing up in the mind the results of external impressions, so that they are enabled to perceive the points of resemblance or differ- ence between two objects, after having been out of sight of them for a greater or less length of time. Bain defines memory, acquisition or retention, as ‘‘ being the power of continuing in the mind impressions that are no longer stim- ulated by the same agent, and of recalling them afterward by purely mental forces.”’ With the aid of memory, birds make their migrations, bees and ants find their way back to their nests. As we have elsewhere said, ‘‘ No automaton could find its way back to a point from which it had once started, however well the machine had been originally wound up. Nor does the common notion of an inflexible instinct meet the case. Memory is often due to a repetition of certain experiences, and experiences lay the foundation for instinctive acts ; it ig the sum of these inherited experiences which make up the total which passes under the name of instinct.’’t * Article on Instinct in Nature, April 10th, 1873. + Half Hours with Insects, p. 374. 682 . ZOOLOGY. It would appear, then, that animals have in some slight degree what we call mind, with its threefold divisions of the sensibilities, intellect, and will. When we study animals in a state of domestication, especially the dog or horse, we know that they are capable of some degree of education, and that they transmit the new traits or habits which they have been taught to their offspring; so that what in the parents were newly acquired habits become in the descend- ants instinctive acts. We are thus led to suppose that the terse definition of instinct by Murphy, that it is ‘‘ the sum of inherited habits,’’ is in accordance with observed facts. Indeed, if animals have sufficient intelligence to meet the extraordinary emergencies of their lives, their daily, so- called instinctive acts, requiring a minimum expenditure of mental energy, may have originated in previous genera- tions, and this suggests that the instincts of the present generation may be the sum total of the inherited mental ex- periences of former generations. Descartes believed that animals are automata. Lamarck expressed the opinion that instincts were due to certain in- herent inclinations arising from habits impressed upon the organs of the animals concerned in producing them. Darwin does not attempt any definition of instinct ; but he suggests that ‘‘ several distinct mental actions are com- monly embraced by this term,’ and adds that “‘a little dose, as Pierre Huber expresses it, of judgment or reason often comes into play, even in animals low in the scale of nature.’? He indicates the points of resemblance between instincts and habits, shows that habitual action may become inherited, especially in animals under domestication ; and since habitual action does sometimes become inherited, he thinks it follows that ‘‘ the resemblance between what origi- nally was a habit and an instinct becomes so close as not to be distinguished.”” He concludes that, by natural selection, slight modifications of instinct which are in any way useful accumulate, and thus animals have slowly and gradu- ally, ‘‘ as small consequences of one general law,’’ acquired, through successive generations, their power of acting in- INSTINCT AND REASON. 683 stinctively, and that they were not suddenly or specially endowed with instincts. Rey. J. J. Murphy, in his work entitled ‘‘ Habit and In- telligence,’’ seems to regard instinct as the sum of inherited habits, remarking that “‘ reason differs from instinct only in being conscious. Instinct is unconscious reason, and reason is conscious instinct.”? This seems equivalent to saying that most of the instincts of the present generation of animals is unconscious automatism, but that in the begin- ning, in the ancestors of the present races, instincts were more plastic than now, such traits as were useful to the or- ganism being preserved and crystallized, as it were, into the instinctive acts of their lives. This does not exclude the idea that animals, while in most respects automata, occa- sionally perform acts which transcend instinct ; that they are still modified by circumstances, especially those species which in any way come in contact with man ; are still in a de- gree free agents, and have unconsciously learned, by success or failure, to adapt themselves to new surroundings. This view is strengthened by the fact that there is a marked de- gree of individuality among animals. Some individuals of the same species are much more intelligent than others, they act as leaders in different operations. Among dogs, horses, and other domestic animals, those of dull intellect are led or excelled by those of greater intelligence, and this indicates that they are not simply automata, but are also in a degree, or within their own sphere, free agents. BIBLIOGRAPHY," GENERAL ZOOLOGY. Elements of Comparative Anatomy. By Carl Gegenbaur. London, 1878. A Manual of the Anatomy of Vertebrated Animals. By T. H. Hux- ley. London, 1871. A Manual of the Anatomy of Invertebrated Animals. By T. H. Huxley. New York, 1878. Forms of Anima: Life. By George Rolleston. Oxford, 1870. Grundziige der Zoologie. Von C. Claus. Leipzig, 1876. Fourth edition, 1879. Handbuch der Zoologie. Band 1, Wirbelthiere, Mollusken und Mol- luscoiden, von J. Victor Carus, Leipzig, 1868-1875 ; Band 2, Arthropo- den, von A. Gerstaecker ; Raderthiere, Wiirmer, Echinodermen, Ccelen- teraten und Protozoen, von J. Victor Carus, Leipzig, 1863. Bronn’s Classen und Ordnungen der Thierreichs. Protozoa, Radiata, Crustacea, Amphibia. (Other partsincomplete.) Leipzig und Heidel. berg. ; Zoologie. Won L. K. Schmarda. 2, Auflage. Band 1, 2. Wien, 1877-78, The Anatomy of Vertebrates. By R. Owen. 38vols. London, 1868. A Key to the Birds of North America. By Elliott Coues. Boston, 1872. The Birds of North America. 3 vols. By 8S. F. Baird, T. M. Brewer, and R. Ridgway. Land Birds. Boston, 1874. Contributions to the Natural History of the United States. By L. Agassiz. 4 vols. Boston, 1857-1862. Mind in Nature. By H.J. Clark. New York, 1865. Manual of the Vertebrates of the Northern United States. By D. 8S. Jordan, Second edition. Chicago, 1878. Seaside Studies in Natural History. By E. C. Agassiz and Alexander Agassiz. Radiata. Boston, second edition, 1871. Introduction to Entomology. By W. Kirby and W. Spence. 4 vols. London, 1828. * Works used in the preparation of this volume, with the titles of others indispen- sable to the student. 686 ZOOLOGY. Manual of Entomology. By H. Burmeister. London, 1836. Guide to the Study of Insects. By A. S. Packard, Jr. Eighth edition. New York, 1883. Invertebrate Animals of Vineyard Sound. By A. E. Verrill. (Re- port U. S. Commissioner of Fish and Fisheries.) Washington, 1873. Invertebrata of Massachusetts. By A. A. Gould. Edited by W. G. Binney. Boston, 1870. First Book of Zoology. By E. 8. Morse. Second edition. New York, 1875. : Manual of the Mollusca. By 8. P. Woodward. Second edition. London, 1868. Corals and Coral Islands. By J. D. Dana. New York, 1872. Introduction to the Osteology of Mammalia. By W. H. Flower. London, 1870. . Elementary Text-book of Zoology. By C. Claus. Translated by A. Sedgwick. 2 vols , 8vo, London, 1884-5. Elementary Biology. By T. H. Huxley and H. N. Martin. New York, 1876. With tbe works and monographs of Dana, Wyman, Leidy, L. and A. Agassiz, H. J. Clark, Cope, Gill, Hyatt, Verrill, Scudder, Binney, Allen, Coues, Smith, Baird, Ridgway, Brewer, Dall, Cooper, Wilder, Riley, Uhler, Edwards, Grote, Le Conte, Hagen, Scammon, Stimpson, Jordan, Morse, Thomas, Gould, Bland, Prime, Tryon, Gabb, Packard, and others, and the standard works of Linneus, Cuvier, Yon Baer, Leuckart, Gegenbaur, Haeckel, St. Hilaire, Huxley, Mivart, Allman, Hincks, Shuckard, Westwood, P. J. and E. Van Beneden, Brandt, Ratzburg, Burmeister, Oscar Schmidt, Metschnikoff, Kowalevsky, Kupffer, and many others. The student should also consult the following serials : American Jour- nal of Science and Arts, New Haven, Conn. ; The American Naturalist, Philadelphia ; Nature, London; Quarterly Journal of Microscopical Science, London; Archiv fiir Naturgeschichte, Berlin; Annals and Magazine of Natural History, London ; Annales des Sciences Naturelles, Zoologie, Paris; Siebold und Kdlliker’s Zeitschrift, Canadian Ento- mologist, London, Canada; Psyche, Cambridge. Descriptions of North American animals and essays on their anatomy, physiology, and development are to be found in the Transactions and Proceedings of the following scientific societies: American Academy of Arts and Sciences, Boston ; American Philosophical Society, Phila- delphia ; Academy of Natural Sciences, Philadelphia ; Boston Society of Natural History ; Smithsonian Institution ; American Entomologi- cal Society, Philadelphia; Museum of Comparative Zoology. Cam- bridge, Mass. ; Essex Institute ; Peabody Academy of Science, Salem: Academy of Sciences, San Francisco, Cal. ; and other societies in Port- land, Me.; Buffalo, N. Y.; Davenport, Iowa; St. Louis, Mo., and Charleston, &. C.; New York and New Haven. BIBLIOGRAPHY. 687 HISTOLOGY. Handbook of Human and Comparative Histology. By 8. Stricker New York, 1872. And the monographs or essays of Leidy, Clark, and C. 8. Minot. PHYSIOLOGY. Treatise on Human Physiology. By J. C. Dalton. Philadelphia, Elementary Lessons in Physiology. By T. H. Huxley. Fourth edition. London, 1870. Text-Book of Physiology. By M. Foster. Jondon, 1877. The Human Body. By H. Newell Martin, N. Y., 1881. EMBRYOLOGY, Entwicklungsgeschichte der Thiere. Von Baer. Kdénigsberg, 1828. Entwicklungsgeschichte des Menschen. Von A, Kéolliker. zig, 1861. Elements of Embryology. By M. Fosterand F. M. Balfour. 1874. A treatise on Comparative Embryology. By F. M. Balfour. 1880. With the monographs of Wolff, Harvey, Barry, Coste, Pouchet, Von Baer, Remak, Bischoff, L. and A. Agassiz, Weismann, Metsch- nikoff, Huxley, Balfour, Parker, Packard, and others. Leip- ZOOGEOGRAPHY, The Geographical Distribution of Animals. By A. R. Wallace. 2 vols. New York, 1876. With the essays of Agassiz, Baird, Allen, Verrill, Ridgway, Gill, Packard, and others. EVOLUTION AND RELATION OF ANIMALS TO THEIR ENVIRONMENT. Philosophie Zoologique. 4J.B. de Lamarck. 8vo, 2 vols. 1809. On the Origin of Species. By Charles Darwin. New York, 1871. The Origin of Genera. By E, D. Cope. Philadelphia, 1861. Contributions to the Theory of Natural Selection. By A. R. Wal- lace. New York, 1870. On the Origin of Species. By T. H. Huxley. New York, 1863. With the essays of Cope, Hyatt, Wagner, Weismann, Haeckel, Kupffer, Palmén, Lubbock, Semper, Packard, and others. NATURAL HISTORY OF MAN. De Generis Humani Varietate Nativa. Von J. F. Blumenbach Editio 3. G6ttingen, 1795. 688 ZOOLOGY. Researches into the Physical History of Mankind. By J. CO. Prich- ard. London, 1851. Types of Mankind. By J. C. Nott and G. R. Gliddon. Philadel- phia, 1854. Natural History of the Varieties of Man. By R. G. Latham. Lon. don, 1850. , Races of Man. By Charles Pickering. London, 1863. Evidence as to Man’s Place in Nature. By T. H. Huxley. New York, 1863. Prehistoric Times. By Sir John Lubbock. London, 1872. Natural History of the Human Species. By H. Smith. Edinburgh, 1882. With the works and essays of Retzius, Wilson, Mortillet, Broca, Lartet, Von Baer, St. Hilaire, 8. Van der Kolk, Vrolik, Schaaffhausen, Riitimeyer, Busk, Morgan, Wyman, Squire, Davis, Schmerling, Wag ner, Vogt, Rolle, Quatrefages, Tylor, and others. GLOSSARY. AB-DO'MEN. In mammals the part of the trunk below or behind the thorax; in insects the third region of the body, or hind body. AB-ER'RANT. Departing from the regular or normal type. AB-O’RAL. Opposite the oral or mouth region. A-BRAN'CHI-ATE (Gr. a, without; bragchia, gills). Without bran- chie or gills. A-cU'M-NATE. Ending in a pro- longed point. Au-vs'o-Lus. koilos, hollow). Applied to vertebree which are doubly concave, or hollow at both ends. A-NAL'0-GY (Gr. analogia, propor- tion). The relation between organs which differ in struc- ture, but have a similar func- tion; as the wings of insects and birds. A-nas-To-mMo/siInG. Inosculating or running into each other like veins. AN-cHY-LOo’s1s. The growing to- gether of two bones so as to prevent motion between them. AN'NU-LATE. When a leg or an- tenna is surrounded by narrow rings of a different color. A'PLA-CEN-TAL. Referring to those mammals in which the embryos are destitute of a pla- centa. A'po vows. Footless. Ap’TE-RoUS (Gr. w, without; pte - on, wing). Destitute of wings. A-QUI'FE-ROUS (Lat. agua, water; JSero, I carry). Applied to the water-carrying or water-vascu- lay system of the sponges, etc. A-RACH'NI-DA (Gr. arachne, a spi- der). The class of Arthropods, 690 embracing the spiders, scor- pious, and mites. A’RE-O-LATE. Furnished with small areas; like a network. A-RIs' TATE, Furnished with a hair. AR-THRO’PO-DA (Gr. arthros, a joint; pous, podos, foot). Those Articulata with jointed feet, such as crabs, bees, etc. AR-TI-CU-La’TA (Lat.articulus, di- minutive of artus, a joint). Cuvier’s subkingdom of worms, crustacea, and insects. AR-TI-O-DAC'TY-LA (Gr. artios, even; daktulos, finger or toe). Those Ungulates with an even number of toes, as the ox. A-sEx’v-AL. Applied to animals, especially insects, in which the ovaries or reproductive organs are imperfectly developed; and which produce eggs or young by budding. AU-RE'LI-A. Old term for the pupa of an insect. AU’RI-CLE (Lat. auricula, a little ear). One of the cavities of the heart of mollusks and verte- brates. Az'y-Gos (a, without ; zugon, a yoke, a pair). An organ, such as a nerve or artery, situated in the middle line of a bilater- ally symmetrical animal, which has therefore no fellow. BZ-No'Po-Da (Gr. baino, to walk). The thoracic legs of insects. Bz'No-soME (Gr. baino, to walk; soma, body). The thorax of in- sects. Brrw. Divided into two parts; forked. GLOSSARY. Buias’T0-DERM (dlastos, a bud or sprout; derma, skin). The outer layer of the germ-cells of the embryo. Buias'To-PoRE. The mouth of the gastrula. BLAs'TO-SPHERE. The embryo when consisting of a single cell-layer. Bran'cui-a. A gill or respiratory organ of aquatic animals. Bran’cu1-au. Relating to the gills or branchie. Boc'cau. Relating to the mouth cavity; or rarely to the cheeks. Buu'Late. Blistered. CA-DU-CI-BRAN'CHI-ATE (Lat. ca- ducus, falling off; Gr. bragchia, gills). Applied to those Ba- trachia in which the gills be- come absorbed before adult life. CaL'ca-RA-TED, Armed with spurs. Ca'Ltyx. A little cup; often ap- lied to the body of a Crinoid. Cap'l-TaTE. Ending in a head or knob. CEN-TRUM. The body or central part of a vertebra. CE-PHALiIc. Relating to the cephalum or head. CE-PHAL'O-MERE. A cephalic seg- meut of an Arthropod. CE-PHAL’O-SoME. The head of in- sects, Arachnida and Myrio- poda. CrER-co’Ppo-pDA (Gr. cercos, tail; pous, podos, foot). The last pair of jointed abdominal appen- dages of insects; the ‘‘cerci.” Cue'La. The terminal portion of a limb with a movable lateral part, like the claw of acrab; as GLOSSARY. in the chelate maxilla of the scorpion. Cur-as’MA (Gr. chiasma, a cross- ing). The commissure of the optic nerves in most verte- brates. Cur'rrn (Gr. chiton, a tunic). The horny substance in the skin of insects, etc. CHYLE (Gir. chulos, juice). The milky fluid resulting from the action of the digestive fluids on the food or chyme. CuyMe (Gr. chumos, juice). The acid, partly fluid or partly digested food, produced by the action of the gastric juice on the food. Cit um (pl. célia). Microscopic filaments attached to cells, usually within the body, and moving usually rhythmical- ly. Cir’Rnus. A slender process on the body of worms. Cuo'a-ca (Lat. a sewer). The common duct or passage at the end of the intestine into which the oviducts and urinary ducts open, us in reptiles, birds, and monotreme mammals. Co‘cau. Ending blindly or in a cul-de sac. Ca'cum. A blind sac; usually applied to one or more append- ages of tne digestive canal. Caz-NEN’CHY-MA (Gr. Koinos, com- mon; chumos, chyme or juice). Applied in polyps to the coral mass containing the chymifer- ous or nutritive canals connect- ing the different polyps. Cou'Lo-PHORE. The sucker-like organ extended from the under 691 side of the abdomen of Podu- rans. Com-MIs’suRE. The nerves con- necting-two ganglia, Con-cou'o Rous. Of the same color as another part. Con'DYLE (Gr. kondulos, a knuckle). The articular sur- face of a bone, especially of the occiput. Cor'tr-cau. Relating to the cor- tex or inner skin; external, as opposed to medullary. Cos'tau (Lat. costa, a rib). lating to the ribs. Crip’RI FORM (Lat. eribrum, a sieve; forma, form). With perforations like those of a sieve. Crop.