Pie i eit . as Ps Pet Pre? 0k. Pe AS Ee eel iere Erg Pe irate thie. ioe LES CORNELL UNIVERSITY LIBRARY BOUGHT WITH THE INCOME OF THE SAGE ENDOWMENT FUND GIVEN IN 1891 BY HENRY WILLIAMS SAGE RETURN TO ALBERT R. MANN LIBRARY ITHACA, N. Y. Cornell University Library QL 45.014 1860 of the animal kingd iT Mh i By See Nf } | Ta oe: AL DON W.S.ORRL”| . a THE ANIMAL ona A SYSTEMATIC AND POPULAR DESCRIPTION OF THE HABITS, STRUCTURE, AND CLASSIFICATION OF ANIMALS, FROM THE LOWEST TO THE HIGHEST FORMS. ARRANGED ACCORDING TO THEIR ORGANISATION, sy BY aU ag! Ww. 8. DALLAS, FLS., Member of the Entomological Societies of London and Paris, and Corresponding Member of the Linnean Society of Lyons, .~-1 eo ~~ 3h OF &, | CANCELL.D | -LONDON AND GLASGOW: OCT. 12 4 RICHARD GRIFFIN AND COMPANY, : PUBLISHERS TO THE UNIVERSITY OF GLASGOW. 1860, TO DR. JOHN EDWARD GRAY, F.RS., KEEPER OF THE ZOOLOGICAL DEPARTMENT IN THE BRITISH MUSEUM, | | IN TESTIMONY OF PERSONAL ESTEEM AND RESPECT FOR HIS SCIENTIFIC ATTAINMENTS, Chis Book is Dedicated, BY HIS OBLIGED FRIEND, THE. AUTHOR. PREFACE. Tue Author's object in preparing the present work has been to furnish the student with a clear and intelligible arrangement of the Animal Kingdom, accompanied, as far as space would permit, by an account of the most interesting particulars of the structure and habits of animals. Considering the class of readers for whose perusal these pages are intended, he has thought it better to follow as closely as possible those views of classifi- cation which are now generally adopted, without, however, pretending that the arrange- ment can be regarded as permanent; indeed, the progress of science already threatens to produce several important modifications in the primary classification of the lower animals, some of which will be found referred to in different parts of this work. The Author has adopted the plan of commencing with the lowest forms of animal life, and working upwards through the long series of existence to the highest. The advantage of this plan is, that we commence with the study of the simplest organisms, and, advancing gradually from these to the more complex, do away with the necessity for a long chapter of generalities at the opening of the book, a great part of which would require repetition as we proceeded with our task. Considerable prominence has been given to the Vertebrated division of animals, the greater amount of individual character presented by these requiring that the habits of the species should be dwelt upon at some length. In this division the illustrations of the groups have been selected, as far as possible, from the British Fauna, and exotic species have been referred to principally when native examples were wanting. In conclusion, the Author must record a few of the principal works to which he has been indebted in carrying out his object. In the first rank of these he must place the excellent ‘‘ Zoologische Briefe”? of Professor Vogt, which has served him as a guide through several departments of the subject. Amongst the Invertebrated animals he has derived great assistance from the works of Dr. Johnston upon the “ British Sponges and Zoophytes;” from that of Professor Forbes upon the “ British Naked-eyed Meduse;” from Professor Milne Edwards’ great work on Crustacea; and Mr. Westwood’s “‘ Introduction iv PREFACE. to the Classification of Insects ;” as also from some of Dr. Gray’s papers on the Mollusca. The principal works on which the classification of the Vertebrata is founded, are Professor Miiller’s admirable paper on the Ganoid Fishes in the Transactions of the Berlin Academy of Sciences; Dr. Gray’s Catalogues of the Reptiles in the British Museum ; Mr. G. RB. Gray’s excellent work on the “ Genera of Birds ;” and Professor Wagner’s con- tinuation of Schreber’s “ Natural History of the Mammalia.” Besides these the excellent — works of Mr. Yarrell on “British Fishes and Birds ;” of Mr. Macgillivray on “ British Birds ;” and of Professor Bell on “ British Reptiles and Quadrupeds,” have been of the greatest service in working up the Natural History of the Vertebrata. It may be as well, im order to avoid the possibility of misleading the public, to add, that this Work, now presented in its complete form, is a portion of the Second and Third Volumes of Organic Nature in the Circle oF THE ScIENCES; 80 that those who possess that Work are already in possession of this Volume. March, 1856. Lavi CONTENTS. ON THE STUDY OF ANIMALS. ‘The Universality of Animal Existence. On Zoological Classification On the Primary Divisions of Aeinale che BuoHeaO, the Dinuees, a Anarernains, the Motiusca, and the VERTEBRATA . DIVISION I—THE PROTOZOA, Pace General Characteristics . . . . . 19 Divided into three Classes . . . . 20 Crass I.—The Ruioropa . . . . 20 Divided into two Orders— the Mownosomata, 205; and the Po- LYTHALAMIA . 6 « 6 «© # 6 « 28 Pace oes Bos we ot we oe 2 108 . . 194 wee ew « 196—208 Pacy Crass II.—The Porrera, or Sponges 24 Cuass III.—The Inrusonpm . . . . 30 Divided into two Orders—the Asromara, 218; and the Sroma- TODA ae ie) Ye i Sh a ty ea BB DIVISION II.—THE RADIATA. General Characteristics . . . . . 42 Divided into Five Classes . . . . 48 Crass I.—The Potypr. . . . 44 Divided into three ordens—tha Hyprowa, 229; the AsTEROIDa, 236; and the HenranrHorma. . 52 Cuass. II.—The DiscopHora . . . 65 Their Structure and Development, 66—70 Divided into two Orders—the Gym- NOPHTHALMATA, 255; and the Sru- GANOPHTHALMATA . ri » 7 Cuass 11].—The CrenopHora. . . 74 Consisting of only one Order, divided into two Families—the Beroide, and the Callianiride . . 4 Crass 1V.—The Srevonorpora. . . 76 Divided into two Orders—the CHon- DROGRADA, and the Puysocrapa . 47 Crass V.—The EcutropERMATA ge EG Their Structure and Development, 77—S0 Divided into four Orders, 81—the Crinomea, 82; the STELLERDDA, 83; the Ecuinma, 84; and the Horormurma,. . . .» .. . 86 DIVISION IIl—THE ARTICULATA. Their great diversity . . ... . 86 Divided into two Sub-divisions . . 86 SUB-DIVISION I.—VERMES. Comprehending four Classes . . . 86 Crass I.—The PraryeLmia Zs 86 Divided into three Biutiie ie CrsrorEA, 272; the TREMATODA, andthe PranarmA . . . - 89 Cuass I].—The Nematenmra . . . 91 viii CONTENTS. Pacy Divided into three Orders—the AcANTHOCEPHALA, the GorDIACEA, and the NemaTomppa. . . . . 91 Cuass III.—The ANNELIDA , . » 93 Divided into four Orders—The Sus- Torta, 95; the Sconecrna, 97; the Tupicota, 98; and the Er- RANTIA - 100 The GapHYREA, a doubtful eile of Annelides, including the genus Lipunculus , , ae oe OE Cuass IV.—The Rormgera. . . . 102 Divided into two Orders—the SzEs- smi1a, 103; and the Narantia. . 104 SUB-DIVISION II—ARTHROPODA (OR TRUE ARTICULATA). Their general Characteristics . . . 104 Divided into four Classes. . . . . 105 Cuass V.—The Crustacea » . « 106 Their Organization, Senses, and Metdmorphoses . . - 107—112 Divided into five principal Groups, or Sub-classes ee « » « OS Sub-Class I.—Crrraopopa : . 112 Divided into two Families—the Li papium and the Bananmz. . . 113 Sub-Class Il—Entomostraca . . . 113 Divided into four Orders—the Para- sita, 113; the Copzpona, 115 ; the Ostricopa, and the Poyttopopa. 117 Sub-Class III].—XyrHosura— Consisting of one Order, XypHo- sura, and one Genus, Lrrutus . 118 Sub-Class 1V.—EpRIoPHTALMATA— Divided into three Orders—the Lamoprropa, the AmpuHrropa, 119; andthe Isoropa . . . . 121 Sub-Class V—Poporatuatmata . . 121 Divided into two Orders—the Sro- mavopa, 123; and the Decaropa. 180 Pace Ciass VI.—The ARAcHNIDA « . BI Divided into two Sub-Classes . 183 Sub-Class T.—TRACHEARIA ‘ . 133 Divided into three Orders—the Poposomata, the Acarina, and the ApELARTAROsoMATA =... 186 Sub-Class 1].—Putmonarta. . . . 187 Consisting of two Orders . . . 188 Order Porymerosomata (Scorpions) 138 Order Dimzrosomata (Spiders) . . 188 Crass VII.—Myrrapopa (Centipedes) . 143 Divided into two Orders—the Cur- Lopopa, 149; and the Cumoagna- THA. we eB. S oe. . 145 Cuass VIIT.—The Insecta . . . . 146 Their General Organization. . . 147 Anatomy of their external Skele- WH « » ea i ee 2 AS Their Mouths, Limbs, and Wings, 151—154 Their Digestive Organs . . . . 155 Circulation and Respiration . 155 Metamorphoses . e 2 AT Divided into threé Sub- slisises . 168 Sub-Class I.—Ameranota. . - 159 Divided into three vil eienarttis Anoptura, 159; the Matnopnaca, and the Tuysanura . . . . . 160 Sub-Class 1I.— Hemierarora. . . 16] Divided into four Orders—the Ruyn- cHora, 163 ; the Paysopopa, 170; _the Orrworrera, 171; and the _ NEUROPTERA. “we « e « 1 Sub-Class III.—Merranoua . 186 Divided into various Orders and Sub-Orders—the ApHanrPTERA (Fleas) ee ew wm « 186 The Drerera (Flies) . . . . . 187 The Lermoprrznra, 196; the Hymr- NOPTERA . . + . 208 Srrepsirera (Bee- arasies) + 2 214 Cotnorrera (Beetles) . 2 . 215 DIVISION IV.—-THE MOLLUSCA. General Characteristics of Mollus- cous Animals. oe me om kw Shells of the Mollusca. oe ow « BEI Divided into two Sub-divisions . « « 239 ' CONTENTS. ix Page Pace SUB-DIVISION I—MOLLUSCOIDA. Cuass VI.—GasTEROPODA. . . » 252 Crass I.—Bryozoa . 233 Divided into two Sub-classes—the Divided into two digdena: tha Iy- Herrropopa, 253; and the Gas- r FUNDIBULATA, 233; and the Lo- teRopopa Proper . . . . . . 254 PHOPODA * 934 | Sub-class L—Herzropopa . 255 Crass I.—Tunicata | 285 Consists of three Families—the At- Divided into two Onis aoe lantide, the Firolide, and the piA, 237; and the Brenora . . 238 Sagittidee : 256 Sub-class II.—GastTERoropa . 256 SUB-DIVISION II—MOLLUSCA Divided into two great Orders—the PROPER. Brancurrera, 297; and the Put- Divided into the AcerHaLous and. MONIFERA . 263 the CrpwaLopHorous Mollusca; Order BrancHirera. oovediais of - and consisting of five great Sub-orders—the Opisthobranchi- Classes . . .. . 289, 240 ata, 257; and the Prosobranchiata 258 Crass IIL.—Lamenimrancamta . . 240 Order Purmonmrra, divided into Divided into two Orders—the Asi- two great Groups—the Opencu- pHonara, 243; and the Srpnonara 246 LATED and the INopERCULATED Crass IX.—ParioprancuiaTa . . 249 Pulmonifera . ao ee - 263 Consists of three principal Groups Crass VII.—Crrnaropopa . . ~ 264 or Families—the Craniide, the Divided into two Orders—the Tr- Terebratulide, and the Lingu- TRABRANCHIATA, 265; and the lide . > ce . 2 250 | Drprancuata . 267 Cuass V.—PrERopopA. . . . 250 General Remarks on Tavariebrasell Divided into two Orders—the Gym- wosomara; and the THecosomata 251 Animals, and on the Alternation of Generations cis aay ae » 270 —272 DIVISION V.—VERTEBRATA. General Characteristics of Vertebrata 273 The Nervous System 3% - + 274 Organs of the Senses . » 275 Alimentary Organs . + » 296 Cireulation . F . . 278 Divided into five Classes . . 260, 281 Ciass I—Fisues oa as . 282 General Characteristics . . . 283 Skeleton » 284 Fins, 265 ; Morraestirdtenncl Fishes, 286; Organs of Senses, 287; Ali- mentary Organs, 288; Circulation, 289 ; Respiration, 289 ; Reproduc- tion, . 2. 290 Divided into five Ontern mite Taw TocaRDIA, 292; the CrcLosromaTa, 292; the TeLgostia, 293; which last is divided again into six Sub- orders—Physostomata, 295 ; Ana- canthina, 305 ; Pharyngognatha, 309; Acanthoptera, 310; Lopho- branchia, 330; Pleetognatha, 331; —the Ganormea, 334, having two Sub-orders, the Holostea, 337, and the Chondrostea, 341; and the Seracum, 343, with two Sub- orders, the Holocephala, 346, and the Plagiostomata . Crass TL—Barracun . General Characteristics Development, 356 ; Respiration Divided into five Orders—the Lzpt- pora, 359; the Arona, 360; the Am- PHIPNEUSTA, 861; the URoDELA, 368; and the Anuna . Cuass IIT.—Reprimia 864 - 369 x CONTENTS, Pace General Characteristics , . , . 369 Skeleton, 370; Seales and Skin, 37]; Circulation, 373; Respiration. . 374 Divided into four Orders—the Orxi- p14, 376, with two Sub-orders—the Viperina, 879, and Colubrina, 382; the Sauru, or Lizards, 388; the Loricara, or Crocodiles, 402; and the Curtonta, or Tortoises . 407 Extinct Forms of Reptiles—the Pterodactyles, Ichthyosauri, and Plesiosauri . . . . . . 408—412 Crass IV—Aves . P - 413 General Characters . - 413 Structure of the Skull, Neck, and Trunk, 414; Sternnm, 415; Ex- tremities, 416; Feathers, 416; Bill, 419; Digestive Organs . . 421 Nervous System, 425; Reproduc- tion. . wie ie te LS - 427 Divided into eight Orders—the Na- TATORES, or Swimming Birds, 428; the GRALLATOREs, or Wading Birds, 478; the Cursores, or Running Birds, 471; the Ra- SoRES, or Scrapers, 475; the CotumBa, or Doves, 493; the Scansorgs, or Climbers, 500; the * PassErss, 519; divided into four Sub-orders—the Conirostres, 520; INDEX, Expnanarory anD REFERENTIAL. . . . . Paez the Dentirostres, 548; the Te- nuirostres, 583; and the Fissi- rostres, 598;—the RaproreEs, or Birds of Prey . . . ~ -616—646 Crass V.—Mammaria . . s+ - 647 General Characteristics . - . 647 Skeleton, 648—654; Digestive Or- gans, 655 ; Circulation and Respi- ration, 656; Nervous System, 657; Senses, 658; Reproduction, 659; Divided into two Sub- classes now ys se we 0 8 Sub-class J—ArtacentTaria, divided again into two Orders—Monorre- mata, 661; and Mansupmra. . . 663 Sub-Class II.—Puacenvartu. . . . 673 Divided into twelve Orders—the Crracea, 674, containing two Sub-Orders—the Cete, 676, and the Sirenia, 684; the Pacuyper- mara, 686; the SoLmuncuta, 695; the Rumantia, 698; the Epenrata, 723; the Roprentiu, 759; the Provnrrepia, 740; the Carnivora, 744; the Insrectrvona, 764; the Curoprera, or Bats, 764; the Quaprumana, 770; the Bimana, including only the hu- man species . 2... 1 1 UT . . - TO NATURAL HISTORY OF ANIMALS —o— In whatever direction we turn our eyes, we everywhere meet the varied forms of animal life. Earth, air, water, are all alike occupied by multitudes of living creatures, each fitted especially for the habitation assigned to it by nature, Every wood or meadow—nay, every tree or shrub, or tuft of grass,—has its inhabitants; even beneath the surface of the ground numbers of animals may be found fulfilling the purposes for which their species were called into existence. Myriads of birds dash through the air, supported on their feathered pinions, or solicit our attention by the charming song. which they pour forth from their resting places; whilst swarms of insects, with still lighter wings, dispute with them the empire of the air, The waters, whether salt or fresh, are also filled with living organisms; fishes of many forms and varied colours, and creatures of still more strange appearance, swim silently through their depths, and their shores are covered with a profusion of polypes, sponges, starfishes, and other animals. To whatever elevation we attain on the mountain sides, to whatever depth in the ocean we may sink the lead, everywhere shall we find traces of animal existence, everywhere find ourselves surrounded by living creatures, in a profusion and variety which may well excite our wonder and admiration. Nor are these phenomena confined to any one region of the earth ; on the contrary, the diversity of climate only adds to the variety of objects which the zoologist is called upon to contemplate. Thus the bold voyager of the inclement regions of the north, in losing sight of those productions of nature which met his eyes at home, finds, as it were, a new creation in his new abode—seals, by the hundred, basking in the scanty rays of the Arctic sun, or diving into the deep waters in search of their finny prey—the whale, rolling his vast bulk in the waves, and ever and anon driving high into the ait his curious fountain—water, be it remembered, strained from the myriads of small ani- mals which constitute the food of the leviathan. The air is peopled by innumerable 10 ZOOLOGICAL CLASSIFICATION. flights of marine birds; the sea by still more countless swarms of fishes; and the land affords a habitation to the elk and the reindeer, the arctic fox, and other creatures peculiar to those regions. If we turn our regards southwards, to the tropical regions of the earth, the abun- dance and variety of animated beings increases more and more. Here the colossal e'ephant, and the equally unwieldy rhinoceros, crash through primeval forests ; the lion and the tiger, and other predatory beasts, prowl through the thickcts, seeking for their prey ; on vast plains, countless herds of antelopes browse in fancied security, or dash swiftly away at the approach of danger; gigantic snakes lie coiled in horrid folds amongst the bushes, or hanging from the trees await their victims. The air and trees swarm with birds of gorgeous plumage, and insects of strange forms and brilliant colours. Nor are the waters less bountifully provided with inhabitants: every form with which we are acquainted in our own seas is here represented, but with still greater profusion and variety. : At night the ocean sparkles with a brilliancy which rivals the splendour even of a tropical sky ; and this phenomenon, which may be witnessed, although in an inferior degree, in more temperate climes, is due to the presence of vast multitudes of minute phosphorescent animals, whose very existence would frequeutlyeremain unknown but for their powers of illuminating the waves by night. And when we have exhausted the study of external nature, there is yet another world to which we may turn. Within our bodies, and those of every species of animal from the highest to uearly the very lowest, exist various forms of parasites, preying upon our substance or our food: creatures whose very existence and development are a mystery—a mystery, however, which, as far as it has yet been unrayelled, serves to raise our expectations as to what remains behind. ON ZOOLOGICAL CLASSIFICATION, When we consider the immense number of animals existing on the face of the earth, of which we have endeavoured, in the preceding section, to give some slight idea, we are soon convinced that an attempt to obtain a knowledge of each of them individually, and without any acquaintance-with their mutual relationships, would be a perfectly hopeless task. We are, in fact, compelled to call in the aid of some system of classifi- cation, which, by bringing together those animals which most resemble each other, and characterizing them by some common point of structure, may enable us to form a sort of general idea of the whole, and to remember more readily the peculiarities of each. Some such classification, rough and imperfect it may be, is, indeed, formed by every observant mind; and its terms find a place in ordinary language. Beasts, birds, and fishes, reptiles, and insects, are words familiar to every one, and convey to the minds of those to whom they are addressed a more or less definite idea, ceived notions of the hearer. ‘ Scientific zoological classification is, in point of fact, to a certain extent, coincident with this popular classification. The latter being the result of observation, the only foundation of natural history, must necessarily be more or less correct, according to the extent to which the different kinds of animals bring themselves under the notice of mankind ; thus we find that tolerably clear notions exist as to the differences between a‘beast, a bird, and a fish,—these being creatures that pass constantly under our eyes ; although, even with respect to these groups, we find some crroneous idvas to prevail. according to the precon- a ZOOLOGICAL CLASSIFICATION. 11 But with respect to insects, and other lower animals with which mankind at large are not familiar, the classification of ordinary language is by no means so precise; so that whilst, in the former cases, zoology can adopt the popular groups merely by sub- mitting them to a few modifications, in the latter, science is compelled to invent a system of her own. This scientific classification is not, however, a mere arbitrary arrangement, like that of the words in a dictionary, with the sole object of enabling us to find out all that is known of a given animal in the shortest possible period of time,—it has another and a higher purpose in view, that of showing the mutual relations of the various members of the animal kingdom, and tracing, in a manner, the steps taken by the Creator in the modification of the same type to suit the various conditions in which His creatures were to be placed. The knowledge of species constitutes the foundation of all zoological knowledge,— * without which we can never arrive at sound generalisations. The species, which forms the first step in classification, consists of an assemblage of individual animals which are supposed all to have descended from the same parents, and exhibit the closest possible resemblance in all parts of their structure. This definition, if definition it may be called, must not, however, be taken in the strictest sense which might be applied to the words; for in many cases we find that individuals undoubtedly belonging to the same species vary considerably amongst themselves, principally in colour and size. Variation is generally to be observed, however, in animals under the influence of domestication, the individuals of most species of wild animals resembling each other so closely that it would be difficult to overlook their specific identity. A test for the specific identity of animals, upon which much stress has been laid, is founded upon the supposed fact, that when two animals of different species breed toge- ther their offspring is always barren. This test is evidently applicable only when we can observe the animals alive; whilst, even under the most favourable circumstances, such observations would be very inconclusive, as hybrids, between undoubtedly dis- tinct species, have been frequently known to breed. We generally find that several species exhibit a considerable amount of resemblance one to another, agreeing perhaps in most points of importance, but differing in characters of minor value, such as colour, texture. and so forth. Such groups of species constitute the second upward step in classification—they are called genera. Thus the horse, the ass, and the zebra, although they may readily be distinguished from each other as species, present a very close resemblance in their general structure, and form a genus; the cat, the lion, the tiger, and the leopard are in the same case; as are also the dog, the wolf, the fox, and the jackal,_the animals may readily be distinguished as species, whilst the structure of their organs presents many common characters. The arrangement of the species of animals in genera, gives rise to the modern system of zoological nomenclature. This system is called the binomial system, from the circum- stance that, according to this method, every animal receives two names ; one belonging to itself exclusively, the other in common with all the other species of the genus in which it is included. For example, the genus Felis, or cat, includes the lion, tiger, leopard, and cat, as species; they all accordingly bear the generic name Felis, with the addition of a second name specially applied to each, serving to distinguish it from all other species of the genus ; thus the lion is called Felis Leo, the tiger Felis Tigris, the leopard Felis Leopardus, and the cat Felis Cattus, This method of nomenclature has at least this advantage over the plan of conferring only a single name upon each species that 12 THE PRIMARY DIVISIONS OF ANIMALS. when we hear for the first time the name of a newly discovered animal, if we are at all acquainted with the genus to which it belongs, the mere mention of the name puts us at once in possession of a considerable amount of information as to its structure, form, and habits. It was first adopted by the illustrious Linneus, the modern founder of Natural History, in the tenth edition of his “Systema Nature,” published in 1758. Proceeding with our ascending scale of classification, we find that the genera in their turn are united by some common characters of importance into Samilies, and these again into ¢ribes. The tribes combine to form orders; in some cases we meet with in- tervening steps, uniting the tribes belonging to one order into two or three subordinate groups. The orders in their turn group themselves into classes; and these lead us up to certain primary divisions which, when put together, constitute the Animaz Krnepom. But although this be the means by which zoologists have arrived at certain conclu- sions as to classification, it is by no means necessary, nor indeed would it be convenient, to follow the same course in communicating those conclusionsto the world; for this purpose we must commence at the opposite end of the scale—that is to say, with the largest groups. = We find, therefore, that all animals are formed upon certain plans or primary types, generally sufficiently distinct. But these primary types of animal structure present us each with well-marked subordinate types, in which, whilst the essential characters of the primary division are preserved, the general structure of the body undergoes more or less modification. These subordinate types become modified in their turn, so that we at last obtain a series of groups, each | characterized by some peculiarity of structure, gradually diminishing in comprehensiveness from the animal kingdom to the species. The characters of the primany divisions of the animal kingdom we now proceed to in- vestigate. ; On the Primary Divisions of Animals.—At the lowest point of the animal kingdom, approaching so cldsely to the lowest forms of plants as sometimes to leave us almost in doubt to which of the great divisions of organized nature they should be referred, we meet with a series of creatures in which the functions of organic life are performed by its simplest element—the coll. From this circumstance they have received from naturalists the denomination of unicellular animals, or Protozoa, These animals, in fact, consist entirely of elementary nucleated cells (see PrysroLoey), or of aggregations of such cells, in which each still retains to a certain extent an ex- istence independent of its fellows, and generally possesses the power, when separated from its attachments, not only of continuing its own life, but even of producing another compound structure similar to that from which it had been detached. These simple creatures possess no digestive cavity ; their food, when solid, being received into the sub- stance of the body, and there gradually assimilated. The nervous and vascular systems are equally deficient ; infact, the nucleus, which is an essential portion of the elementary cell, and one or more contractile vesicular spaces, are the only traces of internal organi- zation observable in the clear gelatinous substance of which they are composed. Reproduction is effected in general by the division of the substance of the animal ; the phenomena of sexuality, which we shall meet with in all the higher animals, are “here never witnessed. From these simple creatures we pass to a group of animals, the lowest members of which exhibit but little, if any, advance in point of organization, They do not, it is true, consist of isolated cells, or of aggregations of similar independent cells ; but in many instances their bodies and organs are constructed entirely of a gelatinous cellular THE PRIMARY DIVISIONS OF ANIMALS. 13 matter very like that of which the Protozoa are composed, and which appears to possess almost an equal power of retaining vitality in its smallest particles. As we advance in the group, however, we find the organization of its constituent animals growing more and more complicated, from the vital functions becoming more and more differentiated—that is to say, performed by organs specially devoted to each; until, from creatures roughly shaped out of a homo- geneous semi - gelati- nous mass, we gradu- ally arrive at animals furnished with distinct nervous and vascular systems, organs of mo- tion and reproduction. The most striking character of the ani- mals included in this group consists in the radiate arrangement of their organs (Fig. 1) round a central axis, which generally passes through the mouth, From this peculiarity they have been de- nominated by zoolo- gists radiated animals they constitute the di- vision Rapiata. This group includes those animals which were formerly supposed to approach very closely to plants, or indeed rather to partake of a sort of mixed nature intermediate between animals and vegetables, hence called zoophytes, or animal-plants ; and some authors make use of this name in preference to that of Radiata, to indicate the present group. The nervous system can only be recognised distinctly in the most highly organized \ # of these animals. In these it partakes of the radiate arrangement of the body (Fig. 2), the nerve distributed to each division of the body corresponding exactly with those of its neighbour, and arising from a separate centre. These centres are all placed in a circle round the mouth, and united by a cord which forms a complete ring, The sense of touch appears to be the only one which can with certainty be ascribed to these animals; this resides in the general integument, and is also frequently ' i exercised by special organs. Fig. 2.—Nervous system of All the Radiata possess a mouth and intestinal cavity ; Star-fish. but very few of them have a second opening for the dis- charge of fecal matters. They generally possess a more or less distinct vascular sys- tem; in some of the higher forms a sac-like heart occurs. Fig. 1.—Star-fish. 14 THE PRIMARY DIVISIONS OF ANIMALS, Sexual reproduction occurs in all the Radiata, and the sexes are generally on separate individuals. Propagation is also very commonly effected in this sub-kingdom by the formation of buds or gemmules; ana these either remain attached to the parent stock, which thus goes on increasing continually in size, or become free, and lead an independent existence. In the two preceding divisions of the animal kingdom we find the body formed upon two very different principles. In the first and lowest it may almost be said to be amor- phous, The organs, such as they are, follow no particular arrangement ; and in many cases it is impossible even to fix their relative position. In the second, however, a certain symmetry is observable; and this is the case also with the remaining groups, the charac- ters of which we have yet to lay before the reader. But this symmetry is of a very different kind; in the Radiata the parts of the body are all grouped round a common axis, every organ being merely a repetition of its fellows; whilst in those which must now pass under consideration, the organs of the body are arranged more or less distinctly in pairs on each side of the body, so as to produce what has been termed by zoologists a dilateral symmetry. In none do we find this mode of construction so completely exhibited as in the animals forming the third primary division of the animal kingdom, to which we must now direct attention. The most striking peculiarity of these animals, by which, in fact, they may generally be distinguished at the first glance from all othercrea- tures, is, that their bodies and limbs are composed more or less distinctly of segments or rings. From this, which is their most prominent character, they have been denominated articulated or annulose animals. They constitute the division AR- TICULATA. The joints or segments of which their bodies are composed, are formed essentially by a series of transverse folds in the integument of the animal. In many of the lower forms the skin still remains perfectly soft and flexible; but in by far the greater number these folds become transformed into a series of horny or crustaceous rings (Fig. 3), united to each other by a softer portion of the integument, so as to permit a greater or less degree of flexibility. The limbs, as well as the body, are constructed of rings of various forms ; and these, taken together may be regarded, to a certain extent, as a sort of external skeleton, ful- filling, as they do, most of the purposes of the skeleton in man, and the animals most related to him. Like this, it gives support to all the soft parts of the body, and furnishes points of attach- ment to the muscles; which again, by _ their action on the moveable pieces com- posing it, give rise to the various move- Fig. 4.—Crab (Thelphusa). ments of the creature. In many cases all the segments composing the body, with the ex- Fig. 3.—Centipede. THE PRIMARY DIVISIONS OF ANIMALS. 156 ception perhaps of those at the two extremities, are exactly similar; each presenting the same form and bearing the same organs as its neighbour. An instance of this may be seen in the Centipede, already figured ; and it is still more strikingly exemplified in many marine worms. Generally, however, the segments present marked differences of form and comparative size, and in the structure of their appendages; this is very distinctly observable in the insects and crabs (Figs. 3, 4). Every segment is supposed to be capable of bearing two pairs of appendages or mem- bers, one connected with the ventral, the other with the dorsal portion of the segment, Both pairs of members do in fact occur upon all, or a portion of the segments in some of these animals; but in general the ventral members alone are developed, and these only on certain segments. In the insects, in addition to three pairs of ventral members, or legs, we tind generally two pairs of dorsal appendages—the wings. Sometimes, as in the earthworm and leech, the limbs are entirely deficient, or only represented by a few bristles ; but, when present, their number is never less than six, The nervous system of the Articulata generally exhibits the tendency to segmentary . repetition, characteristic of the group, very distinctly. In its most characteristic form (Fig. 5), it consists of a Hou- ple nervous cord running down the middle of the ventral portion of the body, and uniting a series of knots or gang- lia which lie in its course ; these ganglia give rise to nerves which are distributed to the various organs. The more elongated the body, and the more similar the differ- ent segments of which it is composed, the more regularly do the ganglia follow one another; whilst, when the scg- ments become more or less amalgamated, the individual ganglia fuse in a corresponding degree into larger masses. This ventral cord originates from one or more cephali¢ ganglia of considerable size, situated in the head above the cesophagus, which give off two filaments to join the : first ventral ganglion, and thus form a nervous ring sur- RB Se preach rounding the cesophagus. From this the ventral cord takes its rise, In the lowest animals arranged in this division we have some difficulty in referring the nervous system to the articulate type; but when these animals present us with a distinct nervous system it consists of one or two ganglia situated in the neigh- bourhood of the csophagus, and giving off two thin branches which run down the body, : The majority of the Articulata possess the senses in tolerable perfection, The eyes in many cases present a highly complex structure, consisting of a great number of hex- agonal facets, each of which may be regarded as a distinct eye , this construction of the eyes is especially prevalent in insects, and is peculiar to the annulose division. When these eyes are wanting, and even when they are present, we frequently meet with simple eyes, which agree very closely in structure with the individual eyes, by the aggregation of which the compound visual organs are formed. taste, and smell, appear also to be possessed by a great many o: the organs by which these faculties are exercised can seldom The senses of hearing, f these creatures; but be indicated with any 16 THE PRIMARY DIVISIONS OF ANIMALS. degree of certainty. The sense of touch of course resides in the general integument ; but special organs of touch are also frequently developed. The mouth is nearly always furnished with several pairs of jaws, placed one behind the other, some serving for the prehension and others for the mastication of food. These jaws open laterally, so that the aperture of the mouth is vertical, or in the direction of the axis of the body. Most of the Articudata have whitish or colourless blood, The only exceptions are to be met with amongst the worms, some of which have red blood. In these, however, the colour of the blood is inherent in the fluid portion, and not due to the presence of red corpuscles (see Physiology). Their circulation is effected by means of a dorsal vessel, which carries the blood from behind forwards ; it returns to the posterior portion of the body, either through a proper vascular system, or by passing through interstices left in the tissues of the body. Sexual oviparous reproduction prevails throughout this division. The sexes are generally separate, although in some of the lower forms we meet with complete hermaphrodism. In the fourth great division of animals the bilateral type of structure is far from being so dis- tinct as in the Articulata, It is, however, still to be recognized in the general arrangement of the external organs, especially of those surrounding the head. These animals, of which the snail may be taken as a familiar example, are usually inclosed in a tough skin, to the inner surface of which the muscles are attached, and by its contraction and dilata- tion the movements of the animal are effected. With the exception of the cuttle fishes, in which a sort of cartilaginous support is present, none of these creatures possess anything which can be regarded as analogous to a skeleton; the body forms a soft mass, frequently varying greatly in’ form at the will of the creature. These pecu- arities have led zoologists to give them the name of molluscous, or soft-bodied animals; they consti- Fig. 6.—Nervous system of a Sepia. tute the division Moxtusca, In most of these animals the nervous system consists of a number of knots or gang- lia, scattered more or less irregularly through the body, united with each other by nervous filaments, and giving off finer filaments, the true nerves, to the various organs, THE PRIMARY DIVISIONS OF ANIMALS. 17 In the more highly organized Mollusca three or four of these ganglia are collected in the head, forming a cephalic mass, which represents a brain (Fig. 6); but even in its most condensed form the separate cephalic ganglia may still be recognized, forming a sort of ring through which the cesophagus passes. Some of the lower forms arranged with the molluscous animals by modern zoolo- gists, possess only a single ganglion, from which filaments are given off in all directions; and between this and the highly complicated structure represented in Ffg. 6, we meet with every conceivable gradation. As might be expected from the great differences displayed by the members of this great division of the animal kingdom, in regard to the degree of development of the nervous system, the senses are possessed by them in very various degrees of perfection. In some of the lowest forms the universal sense of touch appears to be the only one present; but as we ascend in the scale we meet with creatures more highly endowed in this respect. Tentacles, or special organs of touch, frequently occur, generally in the neighbourhood of the head; organs of sight, hearing, smell, and taste, make their appearance, until in the highest forms of molluscous animals we find the organs of the senses as highly developed as in many of those belonging to the highest division. The skin of these animals generally lies loosely about the body, so as to form a sort of cloak or mantle. The mantle frequently possesses the power of secreting a hard substance, well known as the shell, which serves for the protection of the creature (Fig. 7). It increases with the growth of the animal, and varies in form according to the species which inhabits it. The intestinal canal is very variable in its structure,but always presents two openings—a mouth and an anus; the liver frequently Fig. 7.—Pond Snail (Lymnea). attains a very great degree of development. The circulatory system is generally very highly organized; a heart, often divided into several compartments, with arteries and veins penetrating all parts of the body, existing in nearly all the Mollusca. The blood is colourless, or nearly so. The Mollusca are oviparous animals; the male and female organs are frequently in separate individuals, although many species are hermaphrodite. In the fifth and highest division of the animal kingdom we meet with a series of organs to which nothing similar occurs in the groups which have already passed under review. All these animals possess a nervous system, consisting essentially of a brain, inclosed within a bony case, the skull, beneath which the cesophagus passes, and a single cord of nervous matter, originating from the lower part of the brain, passing through a large hole in the base of the skull, and running down through a bony canal, formed by the vertebral column, of which the skull is, in fact, only the anterior portion. As this set of organs, the brain and the spinal cord, the skull and the vertebral column, whilst possessed by no other animals, is constantly present in these, its existence will always 18 THE PRIMARY DIVISIONS OF ANIMALS. serve to distinguish them from the rest of the animal kingdom. They are accordingly called vertebrate animals, and the division which they form, VERTEBRATA, Fig. 8.—Skeleton of the Dugong. These, however, are not the only characters possessed in common by vertebrate animals. The vertebral column forms only a portion of an internal bony framework or skeleton, which serves for the support of the soft portions of the body ; and by fur- nishing the necessary points of attachment for the muscles, assists in effecting the movements of the animal. This framework generally consists of the vertebral column, including the skull; the jaws, which are regarded as appendages of the vertebre, of which the skull is considered to be composed; the ribs, a series of bony arches, articulated at one extremity with the bones of the vertebral column, and at the other either attached to a central bony piece, the sternum, or lying perfectly free in the tissues of the body; and the Zimds, which are never more than four innumber. The jaws in these animals always separate in a vertical direction, so that the opening of the mouth is transverse. They all have red blood, and a muscular heart. Their reproduction is sexual, and the sexes are never united in the same individual. The animals constructed upon this type are the most highly organized of living beings. In no others is the nervous matter, the seat of sensation, intelligence, and volition, presented in so concentrated a form—in none are the senses so perfect, or the various functions of the animal economy so completely isolated. We thus see that animals are constructed upon five primary types or plans, of which all the varied forms presented by these creatures are but modifications, as though the Creator in designing the animal world had imposed upon himself, in the beginning, certain fixed rules, from which he would not swerve. In this manner we get five groups, each of which leads us a step higher than the others ; although it is by no means to be supposed that we have here that gradually ascending chain of beings so much talked of, in which every species, from the lowest to the highest, is supposed to form a link. It is merely in their most highly organized members that the mutual superiority or inferiority of these divisions can be recognized ; and, as a general rule, it may be said, at all events for the Radiata. Articulate. and Mollusca, that the highest members of each group are considerably more perfectly organized than the lower members of the others. The Protozoa and Vertebrata appear to be exceptions to this rule; for the most highly organized of the former can scarcely GENERAL CHARACTERS—THE PROTOZOA. 19 be regarded as superior even to the lowest forms of the other divisions; whilst the fishes, which constitute the lowest members of the vertebrate division, still appear to be more highly organized than the highest Mollusca. These five divisions may therefore stand as follow :— V. VERTEBRATA. IV. Moutusca. III. Arricunara, II. Raprata. I. Protozoa. Drvision I.—Prorozoa, General Characters.—This first division of the animal kingdom includes a number of creatures of a very low type of organization, which appear almost to occupy a sort of neutral ground between animals and vegetables. The bodies of these animals consist either of a simple elementary cell, with its con- tents, or of an aggregation of several of these cells; each, however, still appearing to retain its independent existence. They are generally of very minute size, and only to be observed with the microscope. It is in vain to seek in these creatures for any internal organs. They are entirely destitute of nervous and vascular systems ; and the highest form of alimentary apparatus which is to be found in them consists only of a mouth and a short cesophagus, In many of them, however, no trace of any alimentary canal is to be discerned, and these either live by imbibing fluids through their outer surface, or by the amalgamation of solid substances with the gelatinous mass of which they are composed. This gelatinous matter, which has been termed sarcode by M. Dujardin, frequently has vacant spaces like small bladders in various parts of its substance: these appear and disappear according to circumstances or the will of the animal. They have, nevertheless, been mistaken by Ehrenberg and other observers for so many stomachs, although no one has ever attempted to prove the existence of an intestinal canal uniting them. Almost all these creatures live in water: a few only inhabit the intestines of other animals, They generally present the appearance of a transparent gelatinous cell, in the midst of which a more ot less distinct mucléus is to be observed. In addition to this nucleus, one or more clear pulsating spaces may be distinguished in the interior of the cells. These appear in some degree to effect a sort of circulation of the soft substance of the body, and may, therefore, be regarded as the first shadowing forth of a circulatory system. Many of them approach very closely in their structure to the germs given off by some of the lowest forms of aquatic plants, which, singularly enongh, possess quite sufficient locomotive power to enable them to pass for animals when the observer is unable to trace their development ; indeed, many of them have been described as belonging to the present group. It is very probable, in fact, that a great number of the creatures, still included in this division by naturalists, will prove, on further investigation, to be vegetable organisms. The reproduction of these animals is generally effected by the division of the sub- stance of the creature itself. In some instances two of them combine to form a single celt; which afterwards splits up to allow the escape of a number of young cells. The division always commences in the nucleus above-mentioned. Some Protozoa are also propagated by the division of their substance in a different manner. A small bud shoots out from some portion of the body, which gradually 20 DIVISIONS OF THE PROTOZOA. becomes developed until it resembles its parent, when it is usually cast off to shift for itself, Many of these animals, simple as they may appear, have yet the faculty of pro- ducing a shelly covering for the support and protection of their gelatinous. bodies ; and these are not without their importance in the geological history of our planet. The chalk hills, whose cliffs are so characteristic of the south-eastern coast of this country, consist almost entirely of the shelly coats of innumerable multitudes of these minute I creatures, 3 : ‘i The sponges, perhaps the lowest forms in which animal existence is presented to our observation, are to be placed in this division, as they are also found to consist essentially of an aggregation of nucleated cells. It has often been considered doubtful whether these creatures are really animal organisms, as in many points, and especially in their mode of propagation, they very closely resemble the lowest forms of plants. Their true nature has long been a moot-point with naturalists; and by some zoo- logists they are altogether rejected from the animal kingdom, although the most recent researches, and especially those of M. Laurent, and of Mr. Carter, appear to establish their animal nature beyond a doubt. Division.—The Protozoa are divided into three classes, In the first, to which the name of Rurzoropa has been given, the body is composed entirely of the gelati- nous matter above mentioned. The surface is not furnished with cilia, motion being effected by the extension of portions of the substance into filaments or processes of various forms. These creatures are either solitary or aggregated. In the latter case the compound animal is inclosed in a chambered shell, each individual cell-body occu- pying its own chamber. The second class, including the sponges, consists entirely of associated cell animals ; the individual cells resembling those of the preceding class in their power of extending the substance of their bodies in all directions; but in this class they are united by a mucilaginous intercellular substance, and supported upon a horny framework, From the masses formed by these creatures being perforated in every part with minute orifices, they have received the denomination of PoriFERA. _ The animals constituting the third class of the Protozoa have been called Inrusorta, from the circumstance that they were originally discovered in infusions of vegetable matter exposed to the air for a short time. They are generally solitary unicellular animals, and differ from the Rhizopoda in having the outer surface of the body of a somewhat firmer consistence than the rest of their substance. They are usually fur- nished with a mouth, and their movements are effected by means of cilia, or of one or more long filiform appendages attached to one extremity of the body, Crass I.—Ruzzopopa. In the deposit formed at the bottom of fresh-water ponds, we may often meet with a singular minute gelatinous body, which constantly changes its form even under our eyes, and moves about in its native element by means of finger-like processes, which it appears to have the power of shooting out from any part of its substance, This shape- less gelatinous mass is an animal, the Amaba diffluens (Fig. 9), well known to micro- scopic obsérvers under the name of the Proteus, from the continual changes of shape which it presents to our notice. It consists entirely of the granular gelatinous matter already mentioned as sarcode, and appears to be nearly homogeneous in its texture 3 that THE RHIZOPODA. 21 is to say, the outer surface exhibits no signs of being bounded by any distinct mem- brane or layer of a firmer consistence than the rest of the body. ' With the exception of the pulsating clear space, which has already been referred to as appa- rently constituting the first traces of a circu- latory system, and the nucleus, which, as we have seen, is so essential a portion of the Pro- tozoan animal, no indications of any internal ‘organization are to be recognised in this creature ; for it possesses neither mouth nor intestinal canal. It is not to be supposed, however, that the animal keeps a perpetual fast, or that its food is entirely of a fluid nature. On the contrary, it appears to be, in its small way, of an exceedingly voracious . disposition, seizing upon any minute aquatic ani- ° Fig. 9.—Amwha, 380 diameters. mals or plants that may come in its way, and ap- propriating them to the nutrition of its own gelatinous person. The mode in which this tender aiid apparently helpless creature effects this object is very remarkable. The gela- tinous matter of which it is composed is capable, as we have seen, of extension in every direction ; accordingly, when the dmeda meets with anything that it regards as suitable for its support, the substance of the creature, as it, were, grows round the object until this is completely inclosed within the body, when it is gradually dissolved. The sub- stances swallowed, if such a term be admissible, by this hungry mass of jelly, are often so large, that the creature itself only seems to form a sort of gelatinous coat inclosing its prey; an instance of this is shown at d in the above figure. This curious animal presents us with the essential characters of the class Riizopoda in their simplest form. All the other members of the class resemble it in the texture of the body, and in the mode by which progression and nutrition are effected, however they may differ in other respects. In many cases, indeed in the majority, the creatures are inclosed in a shell or shield, from which the filamentous processes above described as the means by which motion is effected, are protruded through one or more holes pierced in the shell for this purpose. These processes themselves vary very considerably in form, being sometimes thick and finger-like, as in the Ameba; in other instances thinner, variously branched, and often most intricately anastomosed. The Rhizopoda are all aquatic animals. Some live in fresh water, but by far the greater number inhabit the sea. Although a few of them, like the Ameba, are solitary, the class consists principally of associated animals; that is to say, of masses of indi- viduals, forming, as it were, a common body, but each still retaining its independent existence, This difference of habit affords us the means of dividing this class into two orders. The first, the Monosomatia, contains those Rhizopoda which only consist of a single animal; they are either entirely naked or inclosed in a capsule with a single opening for the extrusion of the motor filaments. Of the naked forms, constituting the family Proteidz, we have already had an example in the Ameba; and the other members of the group present very similar characters. The solitary Rhizopoda, furnished with a horny shell or capsule, forming a more or 22 THE RHIZOPODA. less complete case for the animal, constitute the family Arcellide. The filamentous processes by which motion is effected are protruded from « single aperture. These filaments are often much branched; they may be seen under the microscope gradually extending themselves, like streams of very soft gelatinous matter, which divide and subdivide in every direction. In the genus Arcel/a, from which the family derives its name, the shell is somewhat of a bell-shape, with a very large round opening. In Englypha it is of an oval or flask-like form, with the opening at the smaller end. In this genus the shell appears as though formed of a sort of mosaic of small horny pieces. In Difiugia (Fig. 10), the shell is often glo- bular. The animals constituting the second order, the Polythalamia, are all inclosed in calcareous shells. These creatures are social; the shells consisting of @ series of distinct chambers, which sometimes communicate one with another, and sometimes appear to be completely closed up; each of them is supposed to contain a separate and probably independent animal. It gs not improbable, however, that the individual animals may be so connected with each other, through the medium of the openings communi- cating between the cells, as to constitute a common mass, with which each animal is partially amalgamated. In some instances each chamber of the common shell presents only a single external opening ; but, as a general rule, the substance of the shell is pierced, like a sieve, with numerous minute pores, through which very delicate filaments are protruded. All the Polythalamia inhabit the sea; and frequently occur in such great numbers that the fine calcareous sand which constitutes the sea-shore, in many places, consists almost entirely of their microscopic coats. At former periods of the earth’s history they existed in even greater profusion than at present ; and their fragile shells form the principal constituents of several very important geological formations. Thus the chalk appears to consist almost entirely of the shells of these animals, either in a perfect state, or worn and broken by the action of the waves; and they occur in great quantities in the marly and sandy strata of the tertiary epoch. The stone which is universally employed in Paris as a building stone is almost entirely composed of the fossil shells of an animal belonging to this order, the Miliola ; so that this great city, of which its inhabi- tants used to say that he who had not seen Paris had seen nothing, owes its architectural beauties, at all events, to these minute creatures, of which many thousands would scarcely weigh an ounce. Lamarck, the great French naturalist, in referring to this circumstance, observes—‘‘ We scarcely condescend to examine microscopic shells, from their insignificant size; but we cease to think them insignificant when we reflect that it is by means of the smallest objects that nature everywhere produces her most remark- able and astonishing phenomena. Whatever she may seem to lose in point of volume, in the production of living bodies, is amply made up by the number of the individuals which she multiplies, with admirable promptitude, to infinity. The remains of such minute animals have contributed much more to the mass of materials which compose the exterior crust of the globe, than the bones of elephants, hippopotami, and whales,” Fig. 10.—Difflugia Globulosa, 300 diameters, THE RHIZOPODA. 23 From the extremely elegant structure of the shells of these animals, M. Alcide @Orbigny, who was the first to call the attention of modern -naturalists to them, was led to regard them as microscopic forms of Cephalopodous Mollusca, as they presented at first sight a considerable resemblance, on a small scale, to the chambered shells formed by many of those creatures. By M. d’Orbigny, and many subsequent naturalists, they were accordingly arranged in the class of Cephalopoda, with animals possessing at least as high a degree of organization as some of the lower Vertebrata; and it was not until the year 1835 that the researches of M. Dujardin—since amply confirmed by other observers—showed that the creatures to which these shells owed their construction were very nearly allied to the dmeba. Nearly two thousand species of these microscopic shells have been described ; but it is probable that many of these will be found, on further investigation, to be only forms of the same animal in various stages of develop- ment. They have been divided into several families, characterized by the arrangement of the chambers constituting the shell. In one, the Stichostegide, the chambers are placed end to end in a row, so as to form a straight or but slightly curved shell (Fig. 11). In the second family, the Enadloste- gide, the chambers are arranged alternately in two or three parallel lines ; and as the construction of the shell is always commenced with a single small chamber, the whole necessarily acquires a more or less pyramidal form (Fig 12). The third family, the Helicostegide, presents us with some of the most beautiful forms that we meet with in these shells (Fig. 13). They commence by a small central chamber; and each of the sub- Fig. 11. Nodosaria. Fig. 12, Textularia, Fig. 13. Polystomella. sequent chambers, which are arranged in a spiral form so as to give the entire shell much the aspect of a minute flattened snail, is larger than the one preceding it. It is in this family that we find the nearest approach, in external form, to the large chambered shells of the Cephalopodous Mollusca, of which the Nautilus and the Argonaut are examples. The fourth family, the Entomostegide, stand in the same relation to the preceding, as the Enallostegide to the Stichostegide ; that is to say, the chambers are also arranged in a spiral form, but in a double series. A fifth family includes those shells in which the chambers are arranged round a common perpendicular axis in such a manner that each chamber occupies the entire length of the shell. The orifices of the chambers are placed 24 PORIFERA, OR SPONGES. i alternately at each end of the shell, and furnished with a curious tooth or process. The Miliola, already mentioned as constituting the Parisian building stone, will serve as an example of this family. It is probable, although by no means certain, that the animals whose fossil shells, termed Nummulites, are found in great quantities in the chalk and lower tertiary strata, are also to be regarded as members of this class. No living example of this form of animal has yet been met with; but in a fossil state whole mountains in the neighbour- hood of the Mediterranean consist almost entirely of their shells; and the Pyramids of Egypt, which have been reckoned amongst the wonders of the world from very remote ages, are chiefly built with a limestone that is almost entirely composed of Nummulites. In the time of Strabo it appears that the number of these fossils in the stones of the Pyramids had already attracted attention; and he tells us that the then commonly received opinion with regard to them was, that they were the petrified remains of the lentils which had been used as food by the workmen employed in the construction of these vast edifices. Herodotus also notices the occurrence of these fossils in the Pyramids, and gives the above explanation of their origin. Crass II.—Porirers, on Sronces, Although these animals are generally regarded, and perhaps justly, as standing on a sort of debateable ground between the animal and vegetable kingdoms, or at all events as occupying a frontier station in the former and approaching more closely to plants than any other animated beings, we have thought it better to defer the description of their singular structure and history until the completion of that of the Riizopoda; not that the Sponges are necessarily to be regarded as more highly organized than the animals belonging to that class; but because many points, in their structure and de- _ velopment, are rendered far more clear by a previous knowledge of such creatures as the Amebda and its allies. Sponge, in the state in which we usually see it, consists of a congeries of horny filaments, interlaced in every direction so as to form a most intricate network 2 of intercommunicating cells. According to some observers, these filaments are hollow, constituting, in fact, so many horny tubes; but the researches of Dujardin and of Mr. Bowerbank tend to prove that this view was erroneous, and that the threads of which sponge is composed are solid throughout. Imbedded in these threads, in the ma- jority of sponges, are a number of very minute needle-shaped siliceous or calcareous particles of various forms; these are called spicula (Fig. 14). In most cases, the spicula are simply of an acicular form, slender and cylindrical, and pointed at both ends. In other instances they have a small knob at one end, whilst the opposite extremity is pointed, giving them exactly the appear- ance of minute pins; in others again, we find one end transformed into a fork with Fig. 14.—Forms of Spicule. PORIFERA, OR SPONGES. ° 25 two or even three prongs; or the whole spiculum consists of three or four spines of equal length. In spite of their excessive minuteness, these spicula appear to be really small tubes, closed at both ends. for, according to Dr. Grant, to whose researches we are indebted for much valuable information upon the structure and physiology of these simple crea- tures, ‘“‘ when the spicula are examined through the microscope, after exposure to heat, we distinctly perceive a shut cavity within them, extending from the one point to the other; and on the inflated part of each spiculum we observe a ragged opening, as if a portion had been driven out by the expansion of some contained fluid. In those spi- culawhich had suffered little change of form by their incandescence, I have never failed to observe the same cavity within, extending from one end to the other, and a distinct open rent on their side, by which the contained matter has escaped before the usual globular distension had taken place.” This framework, with its contained spicula, is, however, only a sort of horny ske- leton, on which the true living portion of the sponge is supported. This consists of a coating of gelatinous matter, which is spread over all the fibres of the reticulated skeleton; its consistence is very like that of the white of an egg, and it runs freely away from the sponge when the latter is taken out of the water. But when examined under the microscope, this gelatinous coating is found to con- sist entirely of an immense number of aggregated sarcode-cells, exactly resembling the animal described under the name of Ameba, as the simplest type of the Rhizopoda, Like that curious creature, each of these cells appears to possess a perfectly independent existence ; each presents one or more contractile spaces; and even when detached from the mass of its fellows, enjoys the faculty of motion by the extension of its substance in various directions. Such, at least, is the case in the fresh-water sponges, or Syon- gille, the history of which has been most admirably detailed by Mr. H. J. Carter, of Bombay, from whose memoirs the follow- ing particulars, as tothe structure and development of these crea- tures, are principally derived :— “The sarcode cells above- mentioned are imbedded in an intercellular substance, to which the horny framework supporting the sponge appears to owe its origin. The cells, whilst still imbedded in this mucilaginous Fig. 16. substance, are constantly changing their form; and as when separated from the common mass they are seen to take nutritive substances into their bodies in the same manner as the Ameta, it is very probable that the same phenomena occur when the creatures are still in situ. : A glance at a piece of common sponge will show that its surface is everywhere perforated with an infinite number of minute holes, amongst which a considerable number of large openings are scattered. When a sponge is examined in a living state, a rapid stream of water may be observed issuing constantly from these larger orifices. This excurrent stream of water is rendered observable by the fact that it bears with it Section of a Living Sponge. 26 * PORIFERA, OR SPONGES. a number of minute particles from the interior of the sponge (Fig. 16). This water is imbibed through the minute pores distributed in such profusion over the entire surface of the sponge; after passing through these, and traversing the cavities formed in every direction by the reticulated structure of the mass, it is collected into canals, by which it is finally conducted to the larger openings of the surface. The primary objects of this continual flow of water through the substance of the sponge appear to be two-fold; first, the conveyance to the individual cells of which the living portion of the sponge consists, which may be regarded as so many stationary animalcules, the minute particles of nutritive matter necessary for their support and that of the general mass; and, secondly, the removal of fecal matter from the interior of the sponge. But nutrition and the removal of effete materials are not the only purposes to which it is applied—respiration, which, judging from analogy, is as necessary to the sponges as to other animals, must be effected by the medium of this current; and it also fulfils a very important part in the propagation of the species. : But although the imbibition and expulsion of water by the sponges has long been known, its cause long evaded the most persevering scrutiny of zoologists. By the older writers it was believed that the sponge possessed the power of sucking-in the water through the larger orifices, and expelling it, after the lapse of a certain time, through the same openings by which it had penetrated its substance. Thus Linneus says—‘“Spongia foraminibus respirat aquam.” Dr. Grant, however, a good many years since showed that the currents were continuous, and in one direction, although he failed to ascertain the means by which the motion of the fluid was produced. The opinion generally entertained, and indeed the only one by which this phenomenon could be at all accounted for, attributed the production of the current to the action of cilia; and this view has recently been confirmed by some interesting observations of Mr. Bowerbank’s, upon « very curious species of sponge, the Grantia compressa (Fig. 17), not uncommon upon some parts of our coasts. This little sponge consists of a sort of white bag, formed of a thin spongy tissue, suspended by a nar- row base, but exhibiting great variety in form. In its simplest state it is a small fusiform sac (a), with a single large opening at the apex; but when larger it acquires a more or less triangular pentagonal or hexagonal form, with a large opening at each of the angles. The general surface, as in all sponges, is perforated with innumerable minute pores, through which the water passes into the internal ca- vity, whence it is expelled through the larger openings. On cutting open this sponge, and examining it with a magnifying power of about 500 diameters, Mr. Bowerbank found its inner surface to consist of a number of angular cells, formed by triradiate spicula, and terminated by a sort of perforated diaphragm, through which Fig. 17.—Grautia compressa. PORIFERA, OR SPONFES. 27 the cilia could be seen in action. To obtain a transverse section of the substance of the sponge, he was compelled to tear it across as carefully as possible, and to examine the torn edges, when he found that a chamber extended from the diaphragm just mentioned to immediately within the incurrent orifices; this was lined with tesselated cells, many of which apparently bore very long ciliary organs, constantly waving to and fro, in spite of the rather rough treatment to which they had been subjected. The cells, when detached from the parent mass, still, in many cases, retain the organs by which this motion in the water is produced. In this state they bear a considerable resemblance to some infusorial animalcules furnished with a long filiform appendage. The propagation of the sponge is effected in various ways. In some cases, little ciliated gemmules are produced in the gelatinous mass coating the fibres of the sponge ; and after a certain period, becoming detached from the parent, are borne out through the large orifices by the action of the current already described. After this exclusion they swim about for some time, presenting a pretty close resemblance to some of the infusorial animalcules. But this life of freedom is not of very long duration ; the little gemmule selects its place of attachment, fixes itself, and gradually becomes developed into a perfect sponge. In the Spongilla, a somewhat different mode of reproduction occurs. Seed-like bodies are produced in the substance of the sponge, and always in the central or first- formed portion. These, in their earliest stages, consist of several cells, merely united together into a globular or ovoid mass, lying freely in cavities of the substance of the sponge. By degrees this mass of cells acquires a more definite form, and becomes enveloped in a capsule, on the surface of which, after a time, a finer crust of silicious spicula is developed (Fig. 18). The spicula vary in form in the different species of Spongilia; in that from which the annexed figures are derived, they are arranged perpendicularly to the surface of the capsule, and dilated at each end into a stellate disc (e); in others they have no such regular arrangement; they are more or less curved and pointed, and either smooth or spinous. The cells (4) inclosed within this silicious crust also undergo a con- siderable change in their progress towards maturity; they become nearly equal in size, and the granules con- tained in them (a), which originally resembled the granules of the ordinary a sponge-cell, acquire four or five times Fig. 18.—Development of Spongilla. this size. The capsule and silicious a, germs from eels Be cell sone germs; d, spi- * F culum; e, one of its terminal discs; f, spi ee Me nee g, capsule; h, cells 4, erciietion pes seed-like body may escape. ‘When the cells are pressed out of the cavity of the capsule under water, they soon sweli up and burst ; the germs contained in them becoming gradually diffused over the bottom of the vessel in which they are kept. These germs are of very minute size ; 28 PORIFERA, OR SPONGES. the largest of them not measuring more than 1-3000th of an inch in diameter. In form they present some resemblance to the corpuscles of the blood. In a few days the germs are found to have collected into separate groups, each inclosed in a mucilaginous substance. From these germs active animalcules are produced, exactly resembling the cells of which the gelatinous substance of the mature sponge is composed, and possessing the same power of locomotion by the extension of different parts of the body, even in a greater degree. These creatures, in fact, exhibit considerable activity; and during progression their bodies often assume the most fantastic forms. Their appetite also appears to be of the most voracious description. Of this Mr. Carter relates several curious instances ; in one case he “saw one of these proteans approach a gelatinous body, something like a sluggish or dead one of its own kind, and equal to itself in size ; and haying lengthened itself out so as to encircle it, send processes over and under it from both sides, which, uniting with each other, at last ended in a complete approxi- mation of the two opposite folds of the cell-wall, throughout their whole extent, and in the inclosure of the object within the duplicature, Even while the protean was thus spreading out its substance into a mere film, to surround so large an object, a tubular prolongation was sent out by it in another direction, to seize and inclose in the same way a large germ which was lying near it, After having secured both objects, the protean pursued its course rather more slowly than before, but still shooting out its dentiform processes with much activity. It took about three quarters of an hour to perform these two acts,” Not unfrequently combats take place between two of these singular creatures, when, if the size of the combatants be nearly equal, they merely twist about for a short time and then separate ; but if there be any great disparity in bulk, the larger one swallows up his antagonist without remorse. On one occasion Mr. Carter saw a large protean seize a small one with its finger-like processes, and pass it under its body, so that the little one lay between the body of its captor and the glass in which they were both inclosed. ‘For a moment,” says Mr. Carter, “the small protean remained in this position, when the cell-wall raised itself over it in the form of a dome, in which so- formed cavity the little protean began to crawl round and round to seek for an exit ; gradually, however, the cell-wall closed in beneath it in the manner of a sphincter, and it was carried up, as it were, into the interior of the cell, securely inclosed in a globular transparent cavity resembling a hyaline vesicle, but much larger.’ The gelatinous matter with which these groups of germs are invested appears to be identical with the intercellular substance of the mature sponge. After a time, threads of it begin to extend in straight lines on the surface of the glass, and connect the different masses of germ-cells. : The curious phenomena just described—indicating a much higher degree of vital power than we should at first sight be disposed to attribute to such an apparently inert masa as & sponge—are produced in a somewhat artificial manner; although there is every reason to believe that the same thing takes place naturally, and that at certain seasons the waters inhabited by the Spongille must swarm with germs escaped from their cells, and only seeking a suitable support on which to be developed into sponges. But it appears that the seed-like bodies possess yet another mode of development; for if one of them, when mature, be placed in water, it attaches itself to the surface of the vessel which contains it by means of a substance that issues through the opening in the capsule already mentioned. In this substance, when examined by the microscope, cells similar to those existing in the perfect sponge may be recognised, and the mass gradually PORIFERA, OR SPONGES. « 29 becomes developed into a compound creature resembling the parent from which it sprung. As might be expected from the structure of these animals, they manifest but little indication of any general sensibility. It has indeed been stated that a shock, by which the entire mass is simultaneously affected, will produce a very distinct effect upon it, Thus it is said that if a piece of the Syongilla be allowed to fall into water from the ‘height of a few inches, or otherwise exposed to the influence of a sudden shock, the prominent portions in which the vents are situated immediately contract very consi- derably, until the orifices are nearly closed. Other observers have declared that although no movement of contraction may be visible in a sponge, yet when the hand is laid upon it under water a peculiar tingling sensation is felt—due, they suppose, to some movement in the individual particles constituting its mass. This is rendered more probable by the consideration of the structure of the gelatinous coating of the sponge as already described. Sponges grow attached to almost everything which may serve them as a point of support, whether fixed or floating; some cover rocks, shells, and other submarine objects, with a close spongy incrustation; whilst others shoot up a branched stem into the water; and others again hang freely from the seaweeds floating in the ocean. Sometimes they select very unexpected objects on which to take up their abode, Thus, in one case recorded by Dr. Johnston in his “‘ Naturai History of British Sponges,” a specimen of the Halichondria oculata, a sponge not uncommon on some parts of the British coasts, was found growing from the back of a small live crab— a burden,” says the learned Doctor, ‘apparently as disproportionate as was that of Atlas,—and yet the creature has been seemingly little inconvenienced with its arboreous excrescence ; for it is big with spawn in a state nearly ready for laying! Indeed the protection and safety which the crab would derive from the sponge might more than compensate the hindrance thus opposed to its freedom and activity. When at rest its prey might seek without suspicion the shelter afforded amid the thick branches of the sponge, and become easy captives; while, when in motion, scarce an enemy could recognize it under such a guise, and the boldest might be startled at the sight of such a monster.” Not the least wonderful circumstance connected with the history of the sponges is the power possessed by certain species of boring into substances, the hardness of which might be considered as a sufficient protection against such apparently contemptible foes. Shells, both living and dead, coral, and even solid rocks, are attacked by these humble destroyers, gradually broken up, and, no doubt, finally reduced to such a state as to render substances which would otherwise remain dead and useless in the economy of nature available for the supply of the necessities of other living creatures. These boring sponges constitute the genus Cliona, and some allied genera. They are branched in their form, or consist of lobes united by delicate stems; they all bury themselves in shells or other calcareous objects, preserving their communication with the water by means of perforations in the outer wall of the shell. The mechanism by which a creature of so low a type of organization contrives to produce such remarkable effects is still doubtful, from the great difficulties which lie in the way of coming to any satisfactory conclusions upon the habits of an animal that works so completely in the dark as the Cliona—it will probably long remain so. Mr. Hancock, to whom we are indebted for a valuable memoir upon the boring sponges, published in the “Annals and Magazine of Natural History,” attributes their excavating power to the presence of 30 * INFUSORIA, a multitude of minute silicious crystalline particles adhering to the surface of the sponge; these he supposes to be set in motion by some means analogous to ciliary action. In whatever way this action may be produced, however, there can be no doubt that these sponges are constantly and silently affecting the disintegration of submarine calcareous bodies—the shelly coverings, it may be, of animals far higher in organization than they; nay, in many instances, they prove themselves formidable enemies even to living Mollusca, by boring completely through the shell. In this case the animal whose domicile is so unceremoniously invaded, has no alternative but to raise a wall of new shelly matter between himself and his unwelcome guest; and in this manner generally succeeds at last in barring him out. The sponges vary exceedingly in form; and even the same species often assumes shapes the most different without any apparent cause. The forms under which the common sponge occur must be familiar to all our readers; and we have already given an example, in the Grantia compressa (Fig. 17), of a very different and singular form. Other sponges are arborescent, or at all events more or less branched, like the Halichon- dria oculata (Fig. 18); whilst others are of a cup shape. Sponges occur in all seas, from the equator to the poles ; but it is in tropical climates that they attain their greatest development, and exist in the greatest abundance. Cuass III.—Inrusoria. General Characters.—In passing from the consideration of the preceding classes to that of the present group, we are not called upon to witness any very great advance in organization. Nevertheless, the differences between the two classes are all of a nature to show that the Infusoria certainly constitute a step in our progress towards the higher forms of animals, The microscopic creatures constituting this class consist, it is true, of the same granular gelatinous matter, or sarcode, which we have seen to constitute the entire substance of the Rhizopoda ; but this no longer presents itself in the form of a mere mass of jelly: each animal appears to be inclosed in a membrane, or layer of matter of a firmer texture than the rest of its substance ; and motion, which cannot be effected as in the preceding class by the mere extension of portions of this substance in any desired direction, is now produced by the action of special organs. These organs are of very various construction. In some families we meet with long, thread-like appendages, which the animal twitches about in the water. These organs are some- times single; in other instances the animal possesses two or more of them, From Ehrenberg they received the denomination of proboscis, although it does not appear that they are in any way connected with the process of nutrition; and this, with other opinions equally erroneous, published by the great microscopist of Berlin in his works upon these animals, have been adopted, without inquiry, by the generality of subse- quent writers on natural history. The most usual mode in which motion is effected in the Infusoria, is by means of cilia, The cilia are fine lappets or hairs, which exist either scattered or arranged in regular series over the whole surface of the body, or are collected in sonalenatin came bers round the orifice of the mouth. They are moveable at the will of the creature, and serve, according to circumstances, either as organs of locomotion, or for the preduvtian of whirlpools or eddies in the water, by means of which the minute particles on which the animal feeds are brought within its reach. In some of the most highly organised INFUSORIA. 31 creatures of this class these ciliary hairs become converted into moveable bristles and hooks, by means of which the animal is enabled to crawl upon fixed objects in the water, and even to execute distinct leaps. One striking difference between the animals of the present and those of the preceding classes is, that whilst in the latter by far the greater part of the animals are social in their habits, and in many cases seem almost to possess a sort of common existence, the Infusoria are aggregated together in only a few instances, and generally consist merely of a simple cell with its nucleus. Like the Rhizopoda, many of these animals are pro- vided with a shell or shield; this, however, is never of a calcareous nature, but gene- rally coriaceous or horny. In one family the animals are inclosed in silicious or flinty cases, of which great numbers are to be met with in a fossil state in the flints which occur in such quantities in the chalk hills. Ehrenberg, and after him many zoologists who accepted both his facts and opinions without sufficiently examining into their correctness, attributed to these minute organ- isms, which certainly stand in need of no fictitious interest to render their history attractive and wonderful, a structure much more complicated than that of many animals which stand far higher in the scale of organization. By these naturalists we are given to understand that a number of small clear spaces, which are to be observed in the substance of these creatures, are in reality so many stomachs. Some slight difficulty attached to this view, however, as the most persevering researches failed in detecting any evidence of an intestinal cana] uniting these cavities; and like many other con- clusions at which Ehrenberg arrived rather too hastily, this opinion of his, with regard to the functions of the vacuoles, or clear spaces observed in the bodies of the Infusoria, has been disproved on more careful investigation. Thus these vacuoles are seen in many of these creatures to pass round and round the body, along with the rest of its contents, in a manner that renders the existence of the intestinal canal, by means of which they were supposed by Ehrenberg and his followers to be connected into one digestive system, an utter impossibility. They are found, in fact, to consist simply of small globules of fluid; they exist in those Infusoria which are destitute of a mouth, as well as in those which possess that organ; and they may be seen to disappear gra- dually as the fluid which constitutes them is absorbed into the gelatinous mass of the body. Ehrenberg, however, was so convinced of the existence of this alimentary canal, and of the stomachal functions of the vacuoles, that he gave the name of Poly- gastrica, or many-stomached animals, to this class; and even divided them into orders, from the supposed structure of an intestine which no one has ever yet succeeded in discovering. The mode in which nutrition is effected in those Infusoria which possess a mouth will clearly show in what manner this mistake has arisen, These creatures feed upon small microscopic animals and plants, and probably upon such minute particles of decaying animal and vegetable matter as may be suspended in the water which they constantly inhabit. The mouth is situated either at the anterior extremity of the body, where it gene- rally forms a round opening, or at a greater or less distance from that extremity on the ventral surface ; when in this position it is generally in the form of an oval or twisted slit. It is usually bounded by ciliated lips, capable of protrusion and retraction at the will of the animal ; so that the mouth is frequently visible only during the act of eating. The cavity of the mouth is continued into a short esophagus, and both are always clothed with delicate cilia. The minute particles of which the food consists are col- 32 INFUSORIA. lected together by the action of the stream produced by the cilia of the oesophagus, until they form a small ball, which then passes through the end of the cesophagus into the yielding substance of the body. But when imbedded in the parenchyma these balls occupy no particular place, but, like the drops of fluid aliment, follow the general circulatory movement of the gelatinous mass. It will be readily understood how the imperfect observation of these facts led to the supposition that the minute balls of indigo or carmine, to be discerned within the bodies of Infusoria which had been fed upon these substances, were contained in permanent natural cavities, hollowed out for the reception of nutritive matter, and that the clear spaces were similar cavities or stomachs, which for some reason had not been charged with food; but as we find that these apparently vacant spaces not only disappear by the absorption of their fluid contents into the general substance of the animal, but also that not unfrequently two or more of them will run together so as to form a single vacuole, we have pretty certain proof that they are not bounded by membranous walls, and that although there can be no doubt of the occurrenee of the phenomena observed by Ehrenberg, the inferences which he drew from them, as to the complexity of the structure of these creatures, are quite untenable. In these animals, as in the Rhizopoda, we find, in addition to the dark nucleus, one or several clear spaces which expand and contract alternately. These pulsating spaces are usually round, and sometimes exist in such numbers as to constitute a sort of long vessel. In other cases these spaces appear in the form of a star, of which sometimes the rays and sometimes the central space disappear during contraction. Although the pulsating spaces always occupy a determinate position, they appear to be quite destitute of membranous walls, as they may be seen during violent contraction to divide into two or more parts, which afterwards, during their expansion, again become confluent. It seems probable that we have, in these pulsating spaces, the first rudiments of the circulating system which we shall see attain such a high development in many of the higher animals,—that fluids are collected in these vacuoles, and then driven again through the spongy substance of which the body consists. Some naturalists have indeed supposed that they may have a communication, by means of some very delicate vessels, with the water in which the animal swims, so that at each contraction fluids might be expelled from the body, whilst at each dilatation water would be drawn in. This idea is, however, as yet wholly unsupported by observation, from which all that we can learn is, that contractile organs do exist in these creatures ; and this, when we consider their minute size, is in itself a circumstance which may well serve to excite our wonder. But when we come to inquire into the means by which these minute creatures are propagated, and into the processes by which, in a very short space of time, water, in which no trace of animal life was to be discovered, becomes densely populated by them, we shall find our surprise and admiration greatly increased. It will be as well, however, to defer the consideration of this subject till we come to treat of one of the most interesting forms of these animals, the Vorticella, as this creature presents some of the most curious phenomena to be witnessed in the animal kingdom. In many Infusoria, and indeed principally in the very lowest and most doubtful members of the class, a bright red spot is observable near the anterior extremity. This has been described by Ehrenberg as an eye! But apart from the absurdity of attri- buting a distinct visual organ to creatures which have never for a moment been supposed to possess even @ trace of a nervous system, the structure of these red spots has no resemblance whatever to that of an eye; and as many of Ehrenberg’s eyed animalcules INFUSORIAs 33 have since his time been found to be only the spores of aquatic plants, and it is very probable that others will share the same fate as soon as their development shall have been further investigated, this notion of the existence of eyes, in the Infusoria, must be added to the many other instances of unsupported assumption which have unfortunately rendered the persevering labours of that zoologist far less beneficial to science than they might otherwise have been. Most of these animals inhabit water ; a few exist as parasites in the bodies of other animals, The aquatic species prefer clear to foul water, and are always to be met with in greatest profusion in places where Conferve and other forms of aquatic vegetation are abundant. They are produced in great abundance in certain vegetable infusions when exposed to the air; and this circumstance, discovered by Leeuwenhoek in 1676, has always been regarded as one of the principal evidences in favour of the doctrine of spontaneous generation—a doctrine which was at one time in considerable repute, and which is not without its supporters even in the present day. According to this theory an organic fundamental matter is everywhere distributed. Of this, it was supposed, the organs of the higher animals and plants consisted; and to this, if the theory were correct, they would return on the death and consequent decay of the organism. Itwas further supposed that this fundamental organic matter passessed the faculty of organiz- ing itself, under the simultaneous influence of air and moisture, so as to produce certain determinate forms of plants and animals, especially moulds and Infusoria; the animal or vegetable nature of the resulting creature, as well as its specific form, being dependent, said the theory, upon external circumstances. What these external cir- cumstances were, however, and in what manner their influence produced the infinite variety of form observable in these lowly organisms, the theory was unable to say. It was settled, however, that for the purpose of spontaneous generation three things were necessary—namely, the organic substance, water, and air. Later investigations, nevertheless, soon showed that there was some flaw in this theory, specious as it might appear; and although even our present knowledge is not sufficient to enable us to account with certainty, in all cases, for the appearance of animals in infusions, and in the interior of other creatures, a very simple experiment will serve to demonstrate the falsity of the theory of spontaneous generation. If an infusion be boiled and placed in an air-tight vessel, living organisms are never produced in it; but as soon as it is opened, and exposed to the air, the same creatures are produced in it as if it had never been boiled. It would appear from this that the access of air was the condition necessary for the spontaneous production of living organisms. But if the infusion be boiled in a flask to which no air can have access, except by passing through a vessel filled with sulphuric acid, or some other substance which, possessing no power of acting upon the air itself, is yet capable of destroying any organised bodies which might otherwise be borne in with the air, the apparatus may be allowed so stand for weeks or‘months, and the air contained in it constantly changed during the whole period without the production of asingle animal. But when the similar contents of another flask are treated in exactly the same manner, except that the renewing of the air is effected merely through an empty tube, without the intervention of any corrosive sub- stance, the infusion is soon filled with microscopic creatures of all kinds. This experi- ment proves clearly that the production of these minute organisms, in new situations, is due to their presence, or to that of their germs in the atmosphere, and that no new beings result from the mutual contact of organic matter, water, and pure air. Minute as these creature are, and some of them are said not to exceed the 1-20000th t 34 INFUSORIA. of an inch, whilst the giants of their race are not more than 1-50th of an inch in length, they are not without their importance in the economy of the world. By their prodigious numbers they amply compensate for their want of size. Every drop of water on the face of the globe appears to contain them in greater or less profusion; and this, coupled with their great fecundity (for it has been calculated that the progeny of some animalcules would amount to upwards of two hundred and sixty-eight millions in four weeks), may readily convince us of the vast quantity of food furnished by these creatures to others a little higher in the scale, which in their turn become the prey of larger animals. One of the many extraordinary facts, connected with the natural history of the Infusoria, is the power which many of these animals possess of retaining their vitality for a long time, when the water which they had been inhabiting has become dried up with the heat of summer. They will remain thus inclosed in the dry and hardened mud, which frequently, as we all know, becomes baked by the action of the suu into a condition in which the last thing we should suspect would be the presence of animal life, especially of such delicate organisms as these, until the return of wet weather recalls them from their dormant state to activity and enjoyment; or they may be taken up from the surface of the drying pool by the action of wind, and blown about in the atmosphere until they meet with some moisture, in which they may be developed, and may propagate their species. It is probable, in fact, that much of the dust which we so frequently see floating, apparently in the beams of the summer sun, consists of either the bodies or the germs of Infusoria. Divisions.—Tho classification of the Infusoria presents considerable difficulty, partly arising from their excessive minuteness, which renders the assistance of our best microscopes necessary to enable us even to see many of them, and partly from the impossibility of avoiding confusion from the intermixture of the germs of more highly organised animals, and some plants in various stages of development. The class of Infusoria, as circumscribed by Ehrenberg in his “ Infusionsthierehen,” published in 1838, included a curious mixture of heterogeneous elements. It was divided into two great groups, the Polygastrica and the Rotifera, with the latter of which we have nothing to do here ; the animals composing it belonging to a far higher type of organization, But even in the Folygastrica, avast number of species, and especially the whole families of Closterina, Bacillaria, and Volvocina, are found to be true plants; and after the rejection of these we find a considerable quantity of creatures, in which the possession of a moveable filiform appendage, and the existence of a red spot, are the only characters, on account of which they can be referred to the animal kindom. Many of these have been already found to be truly the active germs of Conferve; and it is probable that more extended investigations will, before long, show that many, about which we are still doubtful, are also to be referred to the vegetable kingdom. These species belong to Ehrenberg’s families Monadina and Crypiomonadina. Lastly, his family Vibriontna, including the well known ee/s of paste and vinegar, must be rejected altogether, as it includes a heterogeneous assemblage of microscopic plants and embryonic forms of worms. After the separation of these, the animals still referable to the class of Infusoria are sufficiently numerous and interesting. They may be divided into two orders, characterized by the presence or absence of a mouth in the animals composing them. The first order, the Astomata, or mouthless Infusoria, includes all those in which the mouth is wanting. They appear to be nourished entirely by the absorption of fluid INFUSORIA. 35 matter through their outer surface, and have never been seen to take solid food. The first family of this order, the Astaside, is distinguished by an extremely contractile body, generally of a green or red colour; most of them possess one or two red points. The animals belonging to one of the genera of this family (Hnglena, Fig. 19), which are generally of a green or red colour, fre- quently cause the water they inhabit to appear of one of these colours, in consequence of their sudden appearance in myriads. It is not improbable, however, that some of the creatures included in this group may prove to be vegetable organisms. : The family Dinobryide very closely re- Fig, 19,—Englena viridis, 350 diameter in vari- soo bles the preceding ; but the animalcules Te eres of which it is composed are furnished with a horny case, within which they can retract themselves at pleasure. ; In another family, the Peridinida, the animals are also furnished with a horny or silicious shell or carapace; but in these the shell has a transverse or oblique slit (Fig. 20) furnished with a circlet of cilia; it is also fre- quently produced into very remarkable horn-like pro- cesses. Motion in these ani- mals is effected not only by means of these cilia, but also by the aid of a filiform ap- pendage, which can be pro- truded from a particular spot in the carapace. The sili- cious coats of these creatures are found in great profusion in the flints of our chalk hills, The fourth family of the j astomatous Infusoria, the Opalinide, consists entirely Fie. 20.—Peridinium, 300 diameter. c é a a, Filiform a: dage. b, carapace. ¢, fringe of cilia. of animals which have hither- : Bepecre a Renee ee to only been found living as parasites in the intestines of frogs and of some worms. The bodies of these creatures are colourless, and of a perfectly glassy transparency, so that their structure may be studied with the greatest ease ; and there can be no doubt as to the complete absence of anything like a buccal orifice. Their motions are effected entirely by means of cilia, which are arranged in oblique lines upon their flat oval bodies. From these simple creatures we turn now to the consideration of the far more numerous and interesting forms of Infusorial animalcules, in which the presence of a mouth indicates a higher degree of organization and a more extended sphere of action. They form the order Stomatoda, The first family of this order, the Monadide, consists of roundish or oval animalcules, whose minute size renders their examination difficult even with our very best glasses. Their motions are generally produced by means of filiform appendages, of which each animal possesses one or more. Some of them c 36 THE GENUS VORTICELLA. measure only 1-20000th of an inch inlength; and it has been calculated that a cupful of water may easily contain a number of these animalcules considerably larger than that of the entire human population of the earth. Such an assertion as this may well raise our astonishment to the highest pitch, when we consider that each of these living atoms possesses a mouth well furnished with cilia, through which it is able to intro- duce into its substance particles of solid matter of a size so small that, until collected by these little creatures, our highest magnifying powers will fail to reveal their existence. We now come to a family which includes some of the most beautiful of the infuso- rial animalcules, and in which we meet with phenomena more curious than any we have yet witnessed, and perhaps as wonderful as any that will be presented to our notice, when studying the natural history of the higher classes of animals. This is the family of the Vorticellide, or bell-animaleules. The animals of which it is composed are characterized by the possession of a fringe of rather long cilia, surrounding the anterior extremity, which can be exserted and drawn in at the pleasure of the creature ; by the vibration of these cilia the little animal, which usually has somewhat the appearance of a miniature wine-glass supported upon a very long stalk, can produce a sort of vortex in the water, by which smaller animals and minute floating particles of alimentary matter are drawn into the mouth. Some of these little ereatures are furnished with a horny case for the protection of their delicate bodies, whilst others are quite naked. The genus Vorticella, from which the name given to the family is derived, consists of animals of the latter description. Each of these little creatures is placed at the top of along flexible stalk, the other extremity of which is attached to some object, such as the stem or leaves of an aquatic plant. This stem, slender as it is, is nevertheless a hollow tube, through the entire length of which runs a muscular thread of still more minute diameter. When in activity, and secure from danger, the little Vorticella stretches his stalk to the utmost, whilst its fringe of cilia is constantly drawing to its mouth any luckless animalcule that may come within the influence of the vortex it creates; but at the least alarm the cilia vanish, and the stalk, with the rapidity of lightning, draws itself up into a little spiral coil. But the Vorticella is not wholly condemned to pass a sort of vegetable existence, rooted, as it were, to a single spot by its slender stalk; its Creator has foreseen the probable arrival of a period in its exis- tence when the power of locomotion would become necessary, and this necessity is provided for in a manner calculated to excite our highest admiration, At the lower extremity of the body of the animal, at the point of its junction with the stalk, a new fringe of cilia is developed ; and when this is fully formed the Vorticella quits its stalk, and casts itself freely upon its world of waters. The development of this locomotive fringe of cilia, and the subsequent acquisition of the power of swimming by the Vor- ticella, is generally connected with the propagation of the species, which, in this and some of the allied genera, ane a series of most curious and complicated phenomena. In these, as in all other avon, the simplest mode in which propagation is effected, is by the division of the individual into two or more parts. This division, ag we have already stated when speaking of the Protozoa in general, commences in the nucleus, which, in the Vorticella, ia of a band-like form. Before and during this division of the nucleus the body of the creature acquires a considerable increase in breadth. A constriction afterwards makes its appearance in the middle, which, THE GENUS VORTICELLZ. 37 continually increasing in depth, at last divides the body of the animal into two halves, each of whieh is now found to constitute a perfect Vorticella. Only one of these, however, is to remain in quiet possession of the original stalk ; the other, consequently, develops « fringe of cilia at its lower extremity, detaches itself, and swims away to seek a new home. Having fixed upon a convenient spot for its purpose, it attaches itself, by the hinder part of its body, to the place it has selected; the cilia then disappear, and a new stalk is gradually developed, until the new animal exactly resembles that from which it sprang. The Vorticella also possess another means of propagation which is denied to all the other Infusoria, with. the exception of a few nearly allied genera, although we shall meet with it again in other classes of animals. This mode of reproduction is called germmation. It consists in the production of a sort of bud, which gradually acquires the form and structure of the perfect animal.. In the Vorticella, these buds, when mature, quit the parent stem after developing a circlet of cilia at the lower extremity, and fix themselves in a new habitation in exactly the same manner as the individuals produced by the division of the bell. It might be thought that animals endowed by nature with the power of increasing their numbers by the continual division of their very substance, would stand in no need of any further provision for the continuance of their species; that these means of reproduction would amply suffice to enable them to fulfil the scriptural injunction to “increase and multiply, and replenish the earth.” We find, however, that other and more complicated contrivances are employed for the same end; so that we need not wonder at the great rapidity with which these creatures multiply in situations fayour- able to their development. At an earlier or later period of their existence, the Vorticelle withdraw the disc surrounded by cilia which 2 1 “y SN 58) (CI forms the anterior portion of their bodies; and con- Fig. 21. Development of Vorticella, tracting themselves into a ball, secrete a gelatinous covering which gradually solidifies, and forms a sort of capsule, within which the animal is completely in- closed. Occasionally, this process, by which the Vorti- celle is said to become encysted, takes place, whilst the creature is still attached to its stalk ; but more commonly the circlet of cilia, already mentioned, is first developed at the posterior portion of its body, and the Vorticella becomes encysted whilst swimming freely through the water. Even when the animalcule undergoes this change, whilst still supported on the stalk, the latter soon disappears, leaving the encysted Vorticella free. The body of the animal (Fig. 21, 1) now appears almost homogeneous in its structure, but still contains the nucleus unchanged, and also incloses a small round cavity filled with fluid, which represents the contractile space of the original Vorticella, but no longer exhibits the pulsations characteristic of that organ in the active animal. At this point the history of the creature becomes still more complicated. Sometimes its further progress commences by the breaking up of the nucleus into a number of minute 38 THE GENUS VORTICELLZ. oval discs (Fig. 21, 2), which swim about in the thin gelatinous mass into which the substance of the parent has become dissolved. The body of the parent animal inclosed within the cyst now becomes apparently divided into separate little sacs or bags (Fig. 21, 8), some of which gradually acquire a considerable increase in size, and at length break through the walls of the cyst. After a time one of these projections of the internal substance bursts at the apex; and through the opening thus formed the gelatinous contents of the cyst, with the included embryos, are suddenly shot out into the water (Fig. 21, 4), there to become diffused, and give rise to a new generation of Vorticelle. But this is only one of the phases of the development of these encysted Vorticella ; another and w still more remarkable one remains behind. In other cases, instead of producing a number of little ac- tive embryos in its interior, the encysted Vorticella extends sometimes in one direction, some- times in another (Fig. 22, 1), atthe same time protruding from all parts of its surface a number of slender filaments, terminated by minute knobs, similar to the pro- cesses by means of which we have seen motion produced in the Rhyzopoda. Sometimes a portion of the creature is thrust out, so as to form a new stalk (Fig. 22, 2), by which it attaches itself to objects in the water. Fig. 22.—Acineta-forms of Vorticella. SRBRee reproductive forms of a, nucleus; b, young Vorticella; c, retracted anterior the Vorticelle have long been gira; d, contractile space; ¢, posterior ciliary fringe. known to microscopic ob- servers, and several of them were described by Ehrenberg as belonging to very various genera. From the name Acimeta, given by that author to one of these genera, they are now denominated the Acineta-forms. Two of thém are represented in Fig. 22; the first closely resembles the p.Entila'buds: in various stages; tentacles cf mode of development of these the polype. ‘ small Meduse, The polype-stages 3. Free Medusa of the genus Sarsia. of these animals resemble the Tubularian and Sertularian polypes, From these circumstances, some zoologists have proposed the removal of the whole of the Hydroid polypes into the present class, of which many of them are certainly only stages of development. Opinions are still so much divided, however, as to the true affinities of these animals, that we have preferred leaving the Hydroid polypes in their old position to placing them where few of our readers would think of looking for them, These facts have led to the establishment of the theory of the “ alternation of gene- rations.” Steenstrup, who was the first naturalist to put forward this idea, as a “general fact dependent on a law,” defines it as follows:—“Tne fundamental ilea expressed by the words Alternation of generations,” is “the remarkable and till now inexplicable phenomenon of an animal producing an offspring, which at no time resem- bles its parent; but which, on the other hand, itself brings forth a progeny which returns in its form and nature to the parent animal, so that the maternal animal does not meet with its resemblance in its own brood, but in its descendants of the second, third, or fourth degree of generation. And this always takes place in the different animals which exhibit the phenomena in a determinate generation, or with the inter- vention of a determinate number of generations. This remarkable precedence of cne or more generations, whose function it is, as it were, to prepare the way for the later succeeding generation of animals destined to attain a higher degree of perfection, and which are developed into the form of the mother, and propagate the species by means of ova, can, I believe, be demonstrated in not a few instances in the animal kingdom.” Whilst admitting the general correctness of these ideas, which he considers have “given a strong impulse in the right direction to Invertebrate Zoolugy,” Professor + = : 70. THE MEDUSA. Forbes says, “the assumption of definite regularity in the alternations is a secondary _ ‘and non-essential one, and true, probably, when disturbing conditions are not at work.. But numerous observations ... show that under peculiar circumstances, in what may. be called unnatural situations, the polype generations may go on continnally producing polype generations; and those uf Sars and myself, on the other hand, that a Medusa generation may go on producing Medusa generations ; although, under normal condi- tions in each instance, there is every reason to suppose that zoophytic and Medusa forms would have regularly alternated.” At least four British species of Meduse (two of Lizia and two of Sarsia) have the power of producing young animals by direct gemmation, and their development from a zuophytic furm has. not yet. been observed. In Lizzia and Sarsia gemmifera the buds are produced from the stomachal peduncles ; but in the other species of Sarsia (S. prolifera) they originate from the bulbs at the base of the tentacles, where they may be seen attached in all stages of development. ‘ What strange and wondrous changes!” says Professor Forbes, after detailing his observations upon the last-mentioncd minute Medusa. ‘‘ Fancy an elephant, with a number. of little elephants sprouting from his shoulders and thighs, bunches of tusked monsters hanging, epaulette-fashion, from his flanks, in every stage of advancement! Here a young pachyderm, al- most amorphous; there one more advanced, but all ears and eyes; on :he right shoulder,a youthful Chuny, with head, trunk, toes, no legs, and ashape- less.body; on the left, an infant better grown and struggling to get away, but, his tail not. suffici- ently organized as yet: to : permit of liberty and free. Fig. 54.—Development of Sarsia. action! The comparison. 1. Sarsia gemmifera. a, the peduncle, with buds in various stages of seems grotesque and ab- development. 2. The base of the tentacle of Sursiu prolifera. a, d: b _ tentacle; 5, ocellus; ¢c.c, young buds; d,anearly mature bud, S474; but it. really ex- presses what we have " heen describing as actually occurring among our naked-eyed Medusew. It.is true that, ' the latter are minute; but wonders,are not the less wonderful for being packed into, small compass.” Wonderfully, beautiful as are these creatures in form and colour, the. amount of solid matter contained in their tissues is incredibly small. The greater part of their ' substance appears to consist. of a fluid, differing little, if at all, from the sea-water in: which the animal swims; and when this is drained away, so extreme is the tenuity, of the membranes which contained it, that the dried residue of a “jelly fish,” weighing. | two pounds, which was examined by, Professor Owen, weighed. only thirty grains. ' Yet these creatures are capable of executing movements with considerable vivacity,— their dise contracts and. dilates alternately by the action of a. band of what must be | regarded as a muscular tissue,—their tentacles are capable of seizing upon and de- stroying, by a subtle venom, auimals of far more.complicated structure than themselves, and their delicate stomachs have the power of, speedily digesting the victim. In fact, TUL GYMNOPHTHALMATA, 71 in spite of the extreme delicacy of their texture, the Meduse are amongst the most voracious inhabitants of the ocean. Small fishes, and Crustacea, and all the infinite multitude of minute marine creatures, are seized and paralyzed by their deadly arms; and as the mouth and stomach are capable of almost indefinite dilatation, the size of their prey often appears exceedingly disproportionate. Of the voracity of one of the most delicate and beautiful of the small Medusw inhabiting the British shores, the Sarsia tubulosa, a little creature of the size and shape of a very small child’s thimble, Professor Forbes speaks of as follows :—“ Being kept in a jar of salt water with small Crustacea, they devoured these animals, so much more highly organized than them- selves, voraciously; apparently enjoying the destruction of the unfortunate members of the upper classes with a truly democratic relish. One of them even attacked and commenced the swallowing of a Lizzia octopunctata, quite as good a Medusa as itself. An animal which can pout out its mouth twice the length of its body, and stretch its stomach to corresponding dimensions, must, indeed, be ‘a triton among the minnows,’ and a very terrific one too.” Mr. Peach has described, in the “ Annals of Natural History,” a case in which a’specimen of Thaumantias lucifera had seized the head of a Sagitta, a very active molluscous animal, and suffered itself to be terned completely inside out rather than let go its hold. ‘Divisions.—Much still remains to be done to the subordinate classification of these animals. Prof. Forbes divides the Medusa into two great divisions, which we shall adopt asorders. In the first of these, the ocelli, or eye-like spots, surrounding the margin of the dise are naked (Fig. 55, 1); whilst in the others ‘these or- gans are protected by more or less -complicated membranous hoods or lobed coverings (Fig. 55, 2). ‘Hence the former are called Gymnophthalmata (or naked-eyed), the latter Stegan- ophthalmata (or covered-eyed), In the former the ocelli, when present, are always placed on ‘ the bulbs at the base of the _ Fig. 55.—Ocelli of Medusee. tentacles, and frequently also 1, Sarsia tubulosa. 2. Pelagia panopyra. on the interstices between these. In the second group, on the contrary, they are always placed between the marginal tentacles. Orprr I.—GymMNoPuTHALMATA. ‘General Characters.—In addition to the simplicity in the structure of the ocelli, we find that it is characterized by a similar simplicity in the ‘arrangement of the vascular system. The vessels running from the stomach to the margin of the disc are either perfectly simple, forming so many straight bands, dividing the body of the animal into from four to eight perpendicular segments, or merely branched at some distance from ‘their origin; each branch, however, running directly to the margin without uniting in any way with its fellows. The disc in some ‘species is considerably depressed ; in 72 THE GYMNOPHTHALMATA, others, and indeed in the majority, it is more globular, or even somewhat cylindrical in its form. The tentacles and ocelli are often very numerous, although no more than four of each exist in some species. The animals of this order are further characterized by their mode of reproduction, as they are all, as far as we know at present, produced by actual gemmation from Tubularian and Sertularian poly pes. Divisions.—Professor Forbes, in his work upon the British species of this order, to which we are so largely indebted, divides this group into six families, characterized principally by the number and position of the vessels and ovaries. The first of these, the Sarside, includes, together with several other genera, the Sarsie and Lizzie, already mentioned as producing young Medusw by gem- mation from their central peduncle and from the base of the marginal tentacles. In these the ova- ries are imbedded in the substance of the peduncle. They have four simple vessels, and generally only four tentacles, each bearing an ocellus at their base. In Lizzia, the margin of the umbrella bears eight bulbs, each containing an ocellus; of these, four are larger than the others, and to each of these three tentacles are attached; the other four 56.—Modeeria formosa. bear two tentacles each. In Modceria, although there are but four tentacles, an additional ocellus is placed between each pair. The Modeeria formosa, of which we have given a figure, is one of the most charming of these charming little creatures. In the second family, the Geryonide, the vessels are also simple and four in number; but the ovaries, of which there are also four, instead of being imbedded in the peduncle are placed in the course of the vessels on the sub- umbrella. The tentacles vary greatly in num- ber. In some species there are only four of these organs, each bearing an ocellus; in others the number of both organs is increased, until in the Thaumantias pilosella, of which a magni- fied figure is here given, there are about a j hundred principal extensible tentacles, spring- a ing from ocelliferous bulbs ; whilst in each of NTT} the intervals between these, six or seven shorter Fig. 57.—Thaumantias pilosella. fibres or secondary tentacles are placed. Different species of Thaumantias are most important agents in producing the luminosity of the European seas. The third family,. Circeide, includes only a single genus, of which the few species are scattered over very distant parts of the world. One is found on the coast of Kamtschatka, two on the Africau coasts, and a fourth has been discovered by Professor Forbes off the Shetland Isles. In this there are eight radiating vessels, and eight small ovaries placed on the sub-umbrella in the course of the vessels, THE STEGANOPTHALMATA. 713 In the Zquoride, amongst which are included some of the largest species of naked- eyed Medusz, the vessels are simple and generally numerous (never less than eight); and the ovaries are linear, and placed on the course of the ves- sels on the sub-umbrella. Two British species of this family are described and figured by Professor Forbes; but the species are more numerous in warmer latitudes. The Meduss, composing the fifth family (the Oceanide, Fig. 58), are amongst the most delicate and beautiful of the class, They consist of alittle conical or globular glassy body, within which a variously coloured peduncle may be seen. The lower margin is fringed with tentacles which vary greatly both in num- ber and colour. They possess four simple vessels; and the ovaries are placed in the upper part of the stomachal peduncle, in the form of convoluted membranous tubes, which render themselves noticeable through the clear. substance of the animal by their brilliant colour, In Turris, one of the genera of this family, the tentacles are exceedingly numerous; whilst in another genus (Saphenia), their number is reduced to two. The sixth family, Wilistde, is distinguished from all the rest by the branched form of the radiating vessels. These ara six in number. After running some little distance from the centre of the sub-umbrella, they fork ; and each of the branches again forks before reaching the margin ; so that the marginal vessel receives the terminations of twenty-four radiating ves- sels, From the point of junction of each of these, a tentacle takes its rise. There are six ovaries placed round the base of Fig. 58. the stomach, Oceania episcopalis. Orver II.—SrecanorHraaLMata, General Characters.—The Meduse of this order are distinguished from those belonging to the preceding by several other characters besides those already described. The vessels, instead of running straight from the centre to the circumference of the disc, are variously branched, and their branches unite, more or less, with each other before reaching the margin. The margin of the disc is divided into eight principal segments | by a similar number of notches, in each of which an ocellus is placed. The intervals between these notches are also frequently notched once, twice, or even more frequently ; and from these points the tentacles generally take their rise. The generative organs are attached to the base of the peduncle, where this exists, or placed around the base of central tentacles where the peduncle is wanting. But few observations have been made upon the development of these animals; those whose progress has been traced are found to be produced by the spontaneous transverse division of a Hydraform polype, which itself has arisen from the egg of the parent Medusa (Fig. 52, p. 252). Many of these animals attain a gigantic stature, when compared with the minute and delicate creatures of the preceding order; the Rhizostoma Cuvieri, a British species, measuring two feet, or even more, in diameter; whilst some of the inhabitants of tropical seas are said to attain a still larger size. In calm weather they often swim, close to the surface of the sea, in such multitudes as to impede the motion of a boat through the water. Such a fleet as this, seen with the sun shining strongly upon them, is a magnificent 74 THE CTENOPHORA. spectacle, from the beautiful iridescence with which the sunlight is reflected to the eye of the beholder. With the approach of night this scene of beauty only gives place to another; for these Mcduse are as luminous in the dark as their smaller brethren. Divisions,—This order includes two families. The Meduside have a central mouth, - surrounded by four tentacles, and the remainder of their organs arranged in fours, or multiples of four. The margin of the disc is also generally furnished with tentacles. Several of these inhabit the British seas. The Medusa aurita, already figured (p. 250), the Pelagia cyanella, of which the annexed (Fig. 59) a f f/ U A a Fig. 59.—Pelagia cyanella. Fig. 60.—kuizostoma. is a representation, and the Cyan@a capillata, the account of whose urticating powers we have given in the words of Professor Forbes, may serve as examples, In the second family, the Rhizostomide, there is no apparent mouth, and the animal is said to derive its nourishment by a species of absorption through numerous minute canals which permeate the stomachal peduncle and tentacles. The latter are usually branched, so as to be apparently rather numerous at the extremities. The margin is never furnished with tentacles. One species of this family, the Rhizostoma Cuvieri (Fig. 60), is found on the British coasts. Cuass III.—Crenornora. General Characters.— We now come to a class of animals, the real nature of which is still to be made out. They are gelatinous transparent‘creatures, generally of an oval form, enabled to swim freely by the action of variously arranged rows of cilia. The body of these animals has so much more of the bilateral thanof the radiate type in the arrangement of its parts, that their place amongst the Radiata has been disputed; and M. Vogt has placed them in the neighbourhood of the Bryozoa, or Molluscoid Zoophytes, as low forms of Mollusca. The radiate arrangement of the bands of cilia in most cases, and still more the presence of urticating organs in the tentacles, may justify our retaining them for the present in this position. The cilia in the bands are arranged in transverse lines, and the cilia of each line are frequently united at the base, so as to form minute lodes, which are moved rapidly to and fro, and thus enable the creature to swim backwards and forwards, or in any other direction, at pleasure. Numerous and minute as these organs are, each of them appears T THE CTENOPHORA. 75 to be individually under the control of the animal, When in action they produce the most beautiful iridescent colours, so that it is easy to detect the means by which the creature varies its course,—now paddling with one, and now with another, of its mimic wheels. The mouth lezds sometimes immediately, sometimes through a narrow canal, into a large stomach, which opens again into a funnel-shaped cavity at the opposite extremity of the axis of the body. In the neighbourhood of the mouth there is gene- rally a pair of -very long, branched tentacles, capable, however, of being contracted to an extraordinary extent; these, when contracted, are usually received into a pair of cavities or sheathes, placed close to the stomach, where they lie coiled up, until again wanted for the capture of prey. The rudiment of a nervous system, consisting of a single ganglion, giving off a few branches in various directions, is said to exist in these animals; and a sort of vascular system, apparently for the conveyance of water, rising from the anal funnel, runs along the course of the bands of cilia.. The vessels are lined with a ciliated epithelium, and are probably to be regarded as respiratory organs. The mode of reproduction of the Cteno- phora is still enycloped in mystery. They are supposed to be hermaphro- dites, and ova have been found in the neighbourhood of the aquiferous ves- sels; but where these are produced is not yet asccrtained. These singular. animals form ‘but one order, which is: divided into two families. The Berotda, which form the first family, may almost be said to possess no true stomach, the body being so formed as to inclose a great cavity, of which the hinder portion serves as a digestive organ. When the animals — Fig. 61.—Beroé Panctata. have much food in this cavity, they constrict the middle of the body so as to prevent any of it from escaping. The body is oval or roundish, with eight rows of cilia running from end to end of the body (Fig. 61). The mouth is large and opens and shuts with facility ; it is generally held open when the creature is in motion. The tentacles are wanting in this family. The Callianiride are distinguished from the preceding family by the small size of the stomach and mouth, and by its possession of filamentous ten- tacles. The little Cydippe, already figured (p. 228, Fig, 28), which is common in the British seas, is a ; good example of this group. The most singular of Fig. 62.—Cestum Veneris. these animals is the Cestum Veneris, or girdle of Venus (Fig. 62), which inhabits the Mediterranean, and which at first sight would be RAAAAA MAR WAN Aer PPP PLY 76 THE SIPHONOPHORA, ETC. taken for anything rather than a near relation of the little globular Cydippe. In this curious creature the sides of the body are produced into a long ribbon, which some- times attains the length of four or five feet; the mouth and digestive organs being, however, confined to their original position in the middle of the body. This animal is one of the most beautiful inhabitants of the ocean. When in motion its waving cilia, which are placed along all the margins of the body, glitter with all the tints of the rainbow ; and at night it appears like a long waving flame in the water. Crass TV.—SrpHonoPHorRa. The Siphonophora form another group of animals, of which we have still much to learn before their true natue and relations can be ascertained; and it is probable that, as our knowledge of them increases, it will be found impossible to include them all in the same class. They are divided into two orders—the Chondrograda and Physograda. Orvrr I.—CHonpRocrapa. These animals are called Chondrograda from the circumstance that the circular or oval disc, of which their body is composed, is supported upon a somewhat cartilaginous plate, which sometimes even contains a calcareous deposit; the lower surface of this dise is furnished with cirri, many of which are tubular. The cartilaginous plate is somewhat cellular in its texture, and the cells are filled with air, which assists the animal in floating on the surface of the water. In the middle of the lower surface of the disc there is a larger tubular, tentacle-like organ, which has been taken for the mouth by some observers; by others, for the orifice of the aquiferous system. This central opening is surrounded by many smaller ones, the offices of which are as uncertain as those of the principal tube. Many of these creatures are exceedingly beautiful, blue being their pre- yailing colour. In Porpita, one species of which is found in the Mediterranean, the disc is sur- rounded by a beautiful fringe of. tentacles ; but the most remark- able structure is presented by the Velella (Fig. 68), in which an oblique upright crest is de- veloped upon the upper surface of the disc, serving as a sort of sail to waft the little mariner i from place to place. One spe- Fig. 63.—Velella. cies of this genus is found on the coasts of Ireland. Orper II.—Puysocrapa, The characteristic of the animals forming this order is, that they are furnished with a vesicular organ containing air, which serves as a float to buoy them up in the water. They are divided into two families. In the first, the Physalide, the animals are com- posed of large vesicular gelatinous bodies, bearing on their lower surface a quantity of -yermiform tentacles and suckers, intermixed with filiform tentacles of great length, TH DIPHYIDA. 7 The float consists of two bladders, placed one within the other; the inner one is com- pletely closed, and filled with air; the outer possesses a crest at its upper part, which serves, like the sail of Velella, for its propulsion whilst floating at the surface of the water. The tentacles can also be retracted within this outer bladder at the yleasure of the animal. The best known of these animals is the Physalia atlantica, which has received from our sailors the name of the Portuguese Man-of-War. They swim in great crowds at the surface of the water, and possess a very strong urticating power. The animals forming the second family, the Diphyide, are compound creatures, whose structure has always been a fertile source of discussion amongst naturalists. They have recently formed the subject of several excellent papers from the pen of Mr. Huxley, who considers them to be nearly allied to the common fresh-water polype (Hydra), whose singular history has already been described. In their simplest form they consist of two transparent pieces, one or both of which contains a cavity, by the contraction of which they are propelled through the water. The union between these pieces is very slight ; and, when detached, each piece moves independently for a considerable time. From this circumstance they have been regarded as two distinct animals, which, however, are always found inserted into the cavity of the other. They have been divided into numerous ’ genera; the characters of which are principally derived from the form of the component pieces, They frequently, howédver, assume a much more complicated appearance. The larger or | including individual produces, from the bottom of its cavity, a | slender stalk, which is continually increasing in length, and ' from which new polypes are produced at the portion nearest | the original polype. In this manner a chain of polypes is formed, each presenting a considerable resemblance to its original parent, and each also exerting a certain degree of | independent movement; although the superior power of the large | parent animal always determines the direction in which the whole mass shall move through the water. In some of these animals (as Stephanomia), the complication becomes most extra- ordinary ; but it would be impossible, in our confined space, to | give an intelligible description of the varied and wonderful i forms of these animals, which are to be met with in most Fig. 64.—D iphyes, seas, although they are most abundant in those of warm climates, Crass V.—EcuinopErmata, General Characters.—The Echinodermata, the fifth and highest class of animals included by naturalists in the Radiate division, exhibit a considerable advance in com- plexity of structure over the simple gelatinous creatures which we have hitherto had under consideration. They are at once distinguished from these by the structure of their skin, which, instead of the delicate membranous texture, so characteristic of the other Radiata, presents a more or less leathery consistency, and always contains a . larger or smaller amount of a calcareous deposit, which frequently increases to such an extent as to form a complete shell or crust inclosing all the soft parts of the animal. The skin is also destitute of the curious urticating organs (thread cells) which are so constantly present in all the other animals of this division, The amount of the calca- 78 THE ECHINODERMATA. reous deposit in the skin varies greatly in the different animals composing the class. In some (as the Holotiurie) it forms small irregular grains, scattered, not very plen- tifully, through the substance of the skin; in others, as the Star-fishes (Stellerida), it constitutes plates of various forms, fitting closely to one another, but only connected by the agency of the true skin; so that although the body is completely encased in a suit of caleareous armour, every part of it still retains considerable flexibility. In others again, as the Sea-eggs or Sea-urchins (Zchinida), these plates are positively united together, forming a continuous shell, within which all the organs of the animal are inclosed. Upon most of these calcareous plates tubercles are to be seen, which serve for the articulation of moveable spines, often of considerable size. These assist the animal in its motions; and it is from their almost universal presence that ‘the name of the class (Echinodermata,—echinos a spine, and derma skin) is derived. In their form the Echinodermata vary greatly. They generally present a radiate arrangement of their parts, with great distinctness; some, of which the well-known Star-fish of our coasts may be taken as an example, actually assuming the form of star. In the globular Sea-eggs, also, the same stellate structure may be observed; but it appears to be almost lost in the worm-like Holothurie (Fig), in which, however, the tentacular crown, surrounding the anterior extremity, still presents a radiate appearance. The organs of motion are very similar throughout the class; they consist of a mul- titude of minute feet,’ called ambulacra, which are protruded through a number of perforations left for this purpose in particular plates (hence called ambulacral plates), or through the interstices of the calcareous pieces composing the covering of the animal. The structure of these minute organs is very interesting. In their most perfect form they are vermiform tubes, furnished at their extremity with a distinct sucking disc, which is stretched to its proper furm by a small calcareous ring. ‘The tube communi- cates through ‘its aperture with a small vesicle containing fluid, situated within the shell; and it is by the contraction of this, and the consequent propulsion of the fluid into the cavity of the tube, that the extension of the ambulacrum is effected. The walls of these little feet are all composed of two muscular coats, an inner longitudinal and an outer circular one; and it is ‘by the action of these that the ambulacra are enabled to move about in the water in search of some object to which to attach themselves. The longitudinal muscular coat also serves to contract the organ a3 s00n as the relaxation of the vesicle allows the fluid to flow back from the cavity of the tube, when, if ‘the terminal suckers are attached to any fixed object, the body of the animal is of course drawn in the direction of the contraction. The combined action of a number of ambulacra is, however, necessary to move an animal of a-size so out of all proportion to its diminutive legs as an ordinary Star-fish or Sea-egg. One of these creatures in motion is a most interesting sight. The little guckers are extended in every direction, often to such an extent that they appear only like thin semi-transparent hairs, At length one fixes, then another and another, until at last a number of them, all contracting together, drag their unwieldy owner a step forward. By means of these organs both the Star-fishes and the Urchins can creep up the surface of glass with great facility ; and so firmly do they adhere, that the animal may be broken away, leaving his limbs sticking to the glass. "The existence of a nervous system in the Echinodermata is generally admitted by zoologists. Itis said to consist of a serics of ganglia, or knots of nervous matter sur- rounding the esophagus, united by a nervous ring, and giving of a set of nerves to THE ECHINODERMATA. 79 each ray of the body (Fig 2). The presence of special organs of sense is very doubtful. The sense of touch is evidently exercised by the ambulacra, which are also employed in seizing prey. Some red spots, which occur at the extremities of the arms of Star-fishes, and on the upper surface of Sea-eggs, have been called eyes by some observers, but apparently with but little ground. In their digestive organs the Echinodermata exhibit a very decided superiority over the other Radiata. They all possess a distinct intestinal canal, generally with two openings, one for the reception of food, the other for the discharge of fecal matter. The relative position of these apertures varies greatly in the different groups. In the worm-like forms (Holothuri), and some Sea-urchins, they. are placed at opposite extre- mities of the axis of the body; in the other groups both open on the lower surface. The arrangement of the intestine is also subject to great variation. In the Holothurie it is bent. twice upon itself into a form somewhat resembling the letter 8 ; in the Star- ~ 8 f Fig. 65.—Anatomy of Echinus. a, mouth, surrounded: by the teeth and jaws, c,c; b, esophagus; s, stomach, or first portion of the. intestine; d, intestinal tube; é, ovary; f, f, ambulacral vesicles; g, g, shell. fishes the mouth opens directly. into a large stomach, surrounded with smaller sacs, which are often branched, and in some cases extend far into the arms; whilst in the Sea-eggs the intestine is very long, and wound round in the body (Fig. 65). Some of the latter animals are furnished with an exceedingly complicated masticating apparatus, which has often been described under the name of the “lantern of Aristotle.” It consists of.a.curious framework of V-shaped calcareous pieces, bearing, at their anterior extremity, five hard triangular teeth, The animals possessing this apparatus feed principally upon vegetable matter, whilst those which are destitute of hasticating organs derive most of their nourishment from minute Crustacea and the other marine animals of which the shells are often found in great numbers in their intestines. All the Echinodermata are furnished with very distinct. organs.of circulation, con- 80 THE ECHINODERMATA. sisting of a heart or corresponding organ, and a complicated system of vessels. Respir - tion is effected, in some cases, by means of branchie; in others, by the introduction of water into the general cavity of the body. ‘They are also furnished with peculiar canals, serving for the conveyance of water to different parts of the body,—especially to the vesicles at the base of the ambulacra. The sexes, contrary to the rule which we have seen to prevail in the lower Radiata, are always separate. The ova, when impregnated, become converted into ciliated embryos, which, breaking through the egg-shell, swim freely about in the water. ‘Ihe changes which these undergo in their progress towards maturity are exceedingly remarkable ; and although our space forbids us from describing these with any minute-. ness, a short account of them is nccessary to complete the natural history of the Eeho- dermata, The metamorphosis in question has been most fully observed in Star-fishes and Sea-urchins; and it is to these that we must direct our attention. The ciliated embryo, after its exclusion from the egg-shell, is of a globular form; this is converted into an irregular hexahedron, which gradually increases in height until it forms a four- sided pyramid. In the centre of the base of this pyramid is scen an opening,—the mouth,—which leads intv a stomachal sac. It also contains four or more slender calcareous supports, running from one extremity to the other, and projecting at the base in the four-pointed spines. ‘The Jittle aniinal still moves by the action of cilia which are particularly numerous along the course of the calcareous supports. At a later period of its development the larva acquires a still more pyramidal form; and the processes of the calcareous supports are surrounded by lobes bearing the cilia. In this state it was long regarded as a distinct animal, and described _ under the name of Pluteus. But the most remarkable part of this metamorphosis consists in the fact that this larva does not become actually converted into the perfect Echinoderm, but that the latter sprouts, as it were, from this embryunic form, of which scarcely a trace remains in the mature animal. This is effected in the Ophiure by the following process :—Small sacs first make their appearance in the interior of the larva, surrounding the mouth; these gradually grow out of its substance, unite, and thus represent the disc of the Star-fish. After a short time the new animal forms a mouth for itself; having hitherto derived its nourishment through the mouth of the larva. ‘The arms now begin to sprout ; and soon afterwards the first commencement of the calcare- ous skeleton makes its appearance, in the form of little reticular grains, in the substance of the young animal. The further development goes on in the same manner, until at last the larva is cast off altogether, and the young Ophiura presents the form of its parent, It still, however, possesses cilia, by means of which it swims about for a time; but these afterwards disappear. The only part of the larva that remains in the perfect animal is the intestine, which, of course, is greatly modified. The pomt at which the connection was broken off between the larva and its developed bud is always marked by a plate of a peculiar character. The £Lchinodermata are found in all seas, creeping slowly along the bottom by means of their curious little feet. In earlier periods of the world’s history they appear to have been still more numerous and diversified in form than in the present day; one entire order, which played a most important part in the earlier stages of the formation of our planet, being now all but extinct, Divisions.—The Echinodermata are divided into four orders. In two of these the body is more or less flattened or discoid in its form, and usually furnished with five or more arms. These in the first order, the Crinoidea, are slender, and formed of complete THE CRINOIDEA. 81 calcareous rings or cylinders,—whilst in the second, the Stellerida, the calcareous covering of the arms is composed of separate plates. In the third order, the Echinida, the calcareous plates have become united into a regular shell; and the fourth includes the worm-like forms, the Holothurida. Onprr I.—Crrmormza. General Characters.—The Crinoidea, or Sea-lilies—so called from the resem- blance which many of them present to flowers (Fig. 66)—were exceedingly abundant in former ages of the world; and their remains often form the great bulk of large masses of rock. During the whole or a part of their existence, these animals are attached to submarine bodies by a longer or shorter stalk, composed of calcareous rings similar to those of which the arms are composed. The body is of a cup shape, its lower convex surface—to the centre of which the stalk is attached—being composed of calcareous plates, whilst the upper dise is closed by coriaceous skin. In the centre of this is the opening of the mouth, and to one side the anus. The arms spring from the edges of the cup. They are either five or ten in number at their origins, although often branched higher up, formed of cylindrical or bead-like calcare- ous joints, furnished with slender jointed appendages, or cirri, one on each side of every joint; and, as the whole of these organs are exceedingly flexible, they are of the greatest importance to the animal in the capture of its prey. Divisions.—An exception to this general structure is pre- ; = sented by the Cystocrinide—a fossil family which only occurs ‘Fig 68.—Encrinus. in some of the oldest formations. In these the body is round or oval, and entirely composed of numerous calcareous plates. They were attached by a short flexible stalk, tne mouth was situated at the centre of the upper part, which projects a little from the general surface, with the anal opening a little to one side of it. The family Encrinida, or the Sea-lilies, includes an immense number of fossil forms (Fig. 66); and one or two are still to be found in the West Indian seas. These animals were all supported upon a long stalk, at the extremity of which they floated in the waters of those ancient seas, spreading their long arms in every direction in search of the small animals which constituted their food. Each cf these arms, again, was feathered with a double series of similarly jointed appendages ; so that the number of separate calcareous pieces forming the skeleton of one of these animals was most enormous. _ It has been calculated that one species, the Pentacrinus Briareus, must have been composed of at least one hundred and fifty thousand joints; and “‘as each joint,” according to Dr. Carpen- ter, ‘‘ was furnished with at least two bundles of muscular fibre—one for its contrac- tion, the other for its extension—we have three hundred thousand such in the body of asingle Pentacrinus—an amount of muscular apparatus far exceeding any that has been elsewhere observed in the Animal Creation.” A furrow runs along the inside of the arms, covered with a continuation of the skin of the disc; and from this the ambulacra are protruded, as in other Echinodermata. The third family, the Comatulide, or Hair-stars, includes a considerable number of animals, which bear a great resemblance, both in form and structure, to the Encrinide, They are, however, only furnished with a stalk during their young state, and on arriving 82 THE STELLERIDA. at maturity they quit their attachment, and craw] about freely at the bottom of the water, in the same manner as other Star-fishes. The body is flattened, and covered with separate calcareous plates; the lower, or ventral surface, bearsthe mouth and anus; and the ten slender arms are often branched to such an extent as to appear very numerous, They are furnished throughout their length with slender jointed cirri, similar to those of the Encrinide, by the assistance of which, and the short ambulacra, the Hair-stars are enabled to grasp any object firmly, and creep about on submarine plants with great ease. In their young state, the Comatule exactly resemble the animals of the preceding Fig. 67.—Comatula. Fig. 68.—Young of Comatula (Described as Pentacrinus Europzus). family, being supported upon a long flexible stalk, formed of calcareous cylinders. So close is this resemblance, that when first discovered the young of Comatule was described as a Pentacrinus. Thesé animals are tolerably numerous in the seas of the present day, where they constitute, in fact,.the principal representatives of their order. In the earliest ages of the world, their place was taken by the fixed Encrinide ; and the free Comatule do not make their appearance in dny formation earlier than the Jurassic strata. Orver IJ.—Strexierma. General Characters.—The second order, the Stel/erida, is composed of animals with a fiattened and more or less pentagonal body, usually bearing five arms of variable length, which, however, are not distinctly separated from the body, as in the Crinoidea, and into which processes of the stomach are usually continued. The mouth opens in the centre of the lower surface of the disc ; and the anus, when present, is always situated onthe back. In the neighbourhood of the mouth of the animals of this and the following order, some curious prehensile organs are always to be found, which, from the peculiarity of their structure and actions, have been regarded as inde- pendent parasitic organisms, and described.as such under the name of Pedicellarie, They stand upon little tubercles, and consist of a long calcareous stalk, which bears at: its. extremity a singular forceps of three or four pieces. These are continually opening and © closing, apparently for the capture of floating particles of food ; and, singularly enough, they continue their movements even after the death of the animal. The skin is coria- THE ECHINIDA. 83 ceous, and'the calcareous matter is deposited in it in separate plates, which allow con- siderable flexibility to the whole body; along the lower surface of each arm runs a very distinct furrow, from which the ambulacra are protruded. The true Star-fishes do not occur in the earliest fussilliferous formations. They first make their appearance in the Muschelkalk, and continue increasing in numbers in the more recent strata. In our present seas they are exceedingly numerous, both in species and individuals ; so much so, in fact, that some species, on the coast of Normandy, are commonly used’as manure. Divisions.—The Stellerida are usually divided into three families, The first, the Euryatide,* or Gorgon’s Head, present a considerable resemblance to the animals of the preceding order; the arms being distinctly separated from the body, and the internal organs entirely confined to the disc, which is of a roundish form. The anus is want- ing; the arms have no furrow on their under surface, are always much branched, and usually furnished with cirri, producing the confused and tangled appearance which has caused them to be compared to the Gorgon’s head, with its snaky locks. These animals are principally found in the tropical seas, although some species exist even in the icy waters of the Arctic regions. They are all rare. In the sccond family, the Ophivrida, so called from the resemblance of their arms to serpents’ tails (Gr. Ophis a snake, owra a tail), the body forms a roundish or somewhat pentagonal disc, furnished with five long simple arms, which, like the branched organs of the preceding family, have no furrow for the protrusion of the ambulacra. The Ophiuride are exceedingly plentiful in all our seas, and their remains occur in all the more recent marine strata of the earth’s crust. We come now to the family (the Asteride) of which the. common Star-fish (Fig. 1), so abundant on our coasts, is an example. In,this family the arms appear to be merely prolongations of the disc; they are usually five in number, and the plates from which the ambulacra are exserted are placed in deep furrows, which run along the lower sur- face of the arms. In some species the. arms are very short; and in others the animal forms a flat pentagonal disc, with five ambulacral furrows excavated in its lower sur- face. In the centre of this the mouth is situated, and the ramifications of the stomach extend to a greater or less distance into the arms, Most of the species of this family possess an anal aperture ; but this is wanting in some. Orper II].—Ecurmima, General Characters.—In this order the development of caleareous matter in the skin attains its maximum. The plates, instead of being distinct, as in the Star-fishes, are firmly.attached to each other, forming a convex shell, more or less complete, which prevents all flexion of the body of the animal. This shell presents two openings, a mouth and an anus; the latter is generally situated at the top of the shell, opposite to the mouth, and is surrounded by moveable plates. The division of the animal into five parts is as distinct here as in the Star-fishes, notwithstanding the total absence of.arms; the holes through which the little sucking feet are protruded being arranged upon five rows of plates, which usually run from the centre of the top of the shell to the angles of the oral opening; or, when they are confined, as is sometimes the case, to the dorsal surface, they form a distinct five-rayed star surrounding the apex of the shell. The mode in which the capacity of the shell is increased, is exceedingly curious and interest- ing. Itisentirely covered by a skin of greater or less thickness ; and, it appears, that, * From Euryale, one of the Gorgons, 84 THE ECHINIDA. in spite of the close proximity of the edges of the plates, there is yet room for the passage of a minute layer of skin through all their interstices. It is in this that the deposition of calcareous matter takes place, so that, instead of adding fresh matter to the shell only at the oral aperture, as in the Mollusca, the animal increases the size of its domicile in proportion to its growth, by continual additions to the edge of every plate of which it is composed. New plates are also often added in the neighbourhood of the superior orifice. Next to this peculiarity in the form of the shell, the most striking character of the Echinida consists in the numerous spines, frequently of large size, with which the shell is covered. These are articulated to the numerous tubercles presented by the sur- face of the shell; the base of the spines being hollowed for the reception of the convex surface of the tubercle. In consequence of this mode of attachment, the spines possess a considerable power of movement; and, for this purpose, they are furnished with bands of a muscular nature,—and in some species they are even attached to the tubercles by a round ligament inserted into the base of the spine and the apex of the tubercle, and resembling in many respects the ligament of the hip-jointin man, These spines appear to be used as locomotive organs; they also serve to bury their owner in the sand when circumstances require this concealment ; and some species appear, by the same means, to excavate hollows even in hard rocks. Divisions.—The Echinida are divided into four very distinct families. In the first, the Sea-eggs (Cidaride), the body is nearly globular (Fig. 69), with the mouth n the middle of the under surface, surrounded by a naked or warty skin. The anus lies in the middle of the dorsal surface opposite the mouth, surrounded by a rosette of curious plates, which form the orifices of the generative apparatus. It is in this family that the masticatory apparatus attains its highest development, presenting the complicated form represented in Fig. 65. The ambulacral- spaces run from the mouth to the anus ; and the intervening plates are covered with tu- percles and spines, the latter of which are sometimes several inches in length, and as thick as a man’s finger. These animals inhabit the seas of all parts of the world; and some Fig. 69.—Shell of Echinus, or Sea-urchin; on the might side, SPectes are used as food, even covered with spines; on the left the spines removed. on the European coasts of the Mediterranean. The animals of the second family, the C/ypeastridz, have the body of a somewhat discoid form; the shell is very thick, and covered with small tubercles, from which short, thin, hair-like spines take their rise. The mouth is situated in the middle of the lower surface, and is armed with a masticatory apparatus less complicated in its struc- ture than that of the preceding family; but the anus, instead of being placed on the back of the shell, opens on its lower surface a little behind the mouth. The apex of THE HOLOTHURIDA. 85 the shell is occupied by the genital plates; and the rows of ambulacra form a five-rayed star surrounding these on the dorsal surface of the shell. The Cassidulide, forming the third family, are of a roundish or oval form, generally convex, and covered with very fine spines. The mouth is placed in the middle of the lower surface, with the anus behind it, sometimes on the margin, But these animals are especially distinguished from the two preceding families by the total absence of any masticatory apparatus in the mouth. This is equally deficient in the fourth family, the Spatangide,—sluggish animals, which are usually found imbedded in sand, and with their intestines full of the same savoury and nourishing substance: taken in, no doubt, for the sake of the minute particles of organic matter which it might have contained. They are usually of a heart-like form, with the mouth at the anterior margin of the lower surface, and the anal orifice on its posterior margin. The ambulacra are generally confined to the dorsal surface, where they form four or five rays, and the surface of the shell is covered with fine hair- like spines, amongst which a few of larger size may be distinguished. Orper IV.—Hoxornvuripa. General Characters.—In the fourth and last order the body acquires a worm- like form, thus apparently leading us towards the lower groups of the next division. The radiate structure is in fact scarcely recognisable in these animals, except in the arrangement of the tentacula which surround the mouth. The body is always more or less elongated, with the mouth at one end and the anal opening at the other; the calcareous deposit in the skin is reduced to scattered granules; and in one family the ambulacra are entirely wanting. Divisions.—This order is divided into two families. The first, the Synaptida, are characterized by the total absence of ambulacra, the motions of the animals being assisted by peculiar anchor-like processes of the calcareous grains, which projeet from the skin, and roughen the surface of the animal. In the Holothuride (Fig. 70), on the con- trary, the ambulacra, although short, ex- actly resemble those of the other Echinoder- mata in their struc- ture and action. The mouth is surrounded by a ring of calcareous plates, serving for the attachment of the longitudinal muscles, by which the contractions of the body are effected. These animals inhabit the seas of most parts of the world. Some of them are eaten even by European popu- lations; and the Trepang (Holothuria edulis) is an article of luxury amongst the Chinese. This animal, which is very abundant on the north coast of New Holland, is collected Fig. 70.—Holothuria. 86 THE ARTICULATA. there by the Malays in large quantities, dried and packed up in bags for the Chinese market. The Malays and Chinese meet at the Island of Macassar, where the principal trade in this delicacy is carried on; and the quantity annually brought to that place by the fishermen is said,to amount to upwards of four hundred tons, The price varies according to quality, from eight dollars to one hundred and fifteen dollars per pecul (133]bs.) The Echinodermata conclude the series of animals generally termed Radiata by zoologists ; but it is probable that further researches will show the necessity for great modifications in this part of zoological classification. There appears to be little to connect the hard-skinned Echinoderms with the delicate gelatinous animals composing the other four classes ; and Mr. Huxley has already proposed to form these into a sepa- rate group, denominated, from the constant presence of thread cells, Nematophora, The Echinodermata would then be regarded as aberrant forms of the articulate division ; a view to which the study of their metamorphosis lends considerable support, Drvision ITI.—Anrticunats. Great as is the diversity of form and structure presented by the Radiata, the animals forming the present division perhaps exceed them in this respect. So great is | this diversity, in fact, that it is almost impossible to give any common characters which shall positively include the whole ; and some of the most eminent modern zoologists have proposed the establishment of a separate division to include the lower forms. By this means, however, the difficulty is lessened rather than got rid of altogether; for, although a tolerably coherent group is thus obtained for the higher forms, the lower ones still vary to such an extent, that a very loose character is necessary to enable them | to be united in a single group. We shall, however, adopt these sub-divisions, as they may tend to render this part of our subject more intelligible. The general characters of the division have already been given at sufficient length (p. 198), Susprvision I.—VERMEs. General Characters.—The animals of the first sub-division, the Vermes or Hel- mintha, are usually of a very elongated form; and in the higher groups, the division of the body into a number of segments is very distinct; whilst in some of the lower forms this general characteristic of the articulate series is quite unrecognizable. The segments, when present, are generally mere repetitions one of another; and the appendages with which they: are frequently furnished follow the same rule, The nervous system, which, in the parasitic groups (Zntozon), is, as might be expected, in a very rudimentary condition, gradually increases in complexity ; until in the Anne- lida or true worms, it consists, as in the most highly endowed Articulata, of a ventral series of ganglia, united by nervous cords, and communicating with a nervous mass of considerable size (brain) situated in the head. In proportion to this gradual elevation ' of the nervous system is the development of the different organs of the body. This is especially remarkable in the case of the lateral appendages, which are entirely wanting in the lower groups; but in the Annelida they make their appearance often in a very com- Iplicatedform, such as branchial and natatory plates, and jointed bristles serving as feet, In none, however, do they present the peculiar structure of the limbs possessed by the other Articulata the construction of which will be described in the proper place, * THE PLATYELMIA. 87 Divisions.—The Vermes may be divided into four classes, which are generally distinguishable by theit external appearance. Of these, the first two are for the most part parasitic, living in the interior of other animals, few of which, in fact, are exempt from the visits of these unwelcome guests. Of these, the first, the Flat-worms (Platy- elmia) have the body flattened, and generally more or less ovate and leaf-like ; these present the greatest divergence from the articulate type. In the second, the Nematelmia, or Round-worms, the body is usually elongated and cylindrical, and the division into segments is often indicated by annulations of the skin. The other two classes are composed principally of aquatic animals. A few are terrestrial in their habits, but none are parasitic. One of these, the Rotifera, or Wheel Animalcules, includes a number of minute creatures furnished with a pair of ciliated organs at their anterior extremity ; whilst the Annelida, or true worms, have the body distinctly divided into segments, generally furnished with lateral appendages, and with a well developed nervous system. The blood, in this last class, is also generally of a red colour. Cuass I.—PuaryEuora, General Characters.—The study of the Entozoa, or internal parasites, from the nature of their habitations, is perhaps not one of the most attractive branches of Zoology; yet few animals can present a better claim to our notice, from the circumstance that many of them find their natural residence in our own bodies, and in those of our domestic animals, where they often do us a great amount of injury. ‘ They have a still stronger claim to the attention of the scientific zoologist, from the number of points connected with their natural history, which still remain to be cleared up, and from the wonderful nature of those portions of the history of their development, which have been revealed by the recent researches of some of our most eminent naturalists. By far the greater number of the Platyelmia pass the whole or the greater portion of their existence inclosed within the bodies of other animals, of which few are without species of these parasites peculiar to themselves. Some species, however, live in the water, where they swim about freely by means of cilia. ‘They all, however, have the body much flattened, and usually of a more or less ovate form, without any traces of segmentation ; the only exception to this rule being presented by the Tupe-worms, in which, as is well known, the body is of great length, and composed of a multitude of similar joints. We shall see, however, on studying the development of these animals, that the exception is more appatent than real ; for it appears that the Tape-worm may be regarded as a compound animal, each joint being capable of a certain amount of independent existence. The nervous system consists of a pair of ganglia situated in the anterior extremity of the body, and giving off two slender filaments, which run down each side of the body. No special organs of sense have been found in the parasitic species ; but those which live free in the water have several dark spots, each containing a distinct lens, placed close to the central ganglia, and these are considered to be true eyes. With the exception of the cilia of the aquatic forms, no organs of motion are to be met with in the Platyelmia, The parasitic species are generally furnished with hooks or suckers for maintaining themselves in their position; but their movements are almost entirely con- fined to a muscular contraction and dilatation of the body. Divisions.—The Fat-worms are divided into three orders, of which two are com- posed of parasitic, and one of free-swimming animals, They may be regarded as sorming two groups or sub-classes, of which the second is distinguished by the pos- 88 THB CESTOIDRA, session of cilia; the othors being destitute af these organs, Tho two parasitic andors are the Cestoides, or Thpe-rwerms, with long, usually jointed bodies; and the Thematoda, with short, elliptical, or discoid forms. Onvan [.—Crstomra. General Characters,—Tho genoral appearanee of tho animals belonging to the onder Cestoides is well shown in the annexed figure, which representa the cammon Tapo- worm of the human intestines. The body is composed of numerous joints or segments, each oxaotly resembling each other; these are often several hundreds in number, and the animal sometimes attains a longth of upwards of ten trot, ‘The skin is exceedingly soft and tender, and tho musoular system posseases very little onergy ; ao that the m ill ro Mae) <] Fig. 71.—Toonia Soltum. The common Tape-worm, movements of the animal are confined within very narrow limits, Its anterior extro- mity is formed by a small hoad, furnished with hooks and suckers, by means of which the animal anchors itself to the intestines of its victim ; it also contains the rudimonta of tho nervous centre, the filamonts given off by which only run through a fow of the first segments. The animal appears to possoas no mouth or digestive organs; so that it must derive its nourishment ontirely by absorption through the alin, On each sido of the body runs a long vesscl, passing through all the segmonts; those are united at each articulation of the body by a transvorse vossel. Each segment containa both male and fomale sexual organs; and whon thoso havo arrived at maturity, the segmont is onst off to seck a new placo in which its ova may be dovelopod. For this purposo the joints, when onst off, aro endowod with a considerablo power of motion, and will live for several days whon placed in favourablo ciroumstanovs, In some oagcs they have boon observed to develop poouliar organs, which they do not posaosa in their compound condition. The orifloos of the soxual organs aro placed at one side of oach segmont, and those apertures aro placed alternately on both sidos of tho body of tho animal. The development of those animals prosents somo of the most vomarkablo phonomena that havo yot beon discovered in tho natural history of animals, Some curiona para- sitio worms aro found, not in the intoatinos, but in tho solid tisauca of many horbivorous animals, which, from tho structure of tho hoad, havo always boon rangod in tho neighbourhood of tho Tape-worms, although thoir bodies, instoad of boing drawn out to an enormous longth and divided into numorous sogmonts, aro composed almoat entirely of a simple bag of fluid, Somo of these parasites aro simplo,—that is to say, tho ano boars only a ainglo head ; THE CESTOID WORMS. 89 in other cases they develop a multitude of these organs. sometimes from the internal, sometimes from the external surface of their walls. These worms were long regarded as forming a distinct order of parasitic animals; but recent experiments have shown, that when they are administered to particular carnivorous animals with their food, the vesicle of fluid is cast off, the head attaches itself, and gradually develops the long jointed body of a true Tenia. The observations were first made upon the Cystic worms which inhabit the liver of the mouse and rat; these, when given to cats, were found to produce in their intestines Teenias of the species usually infesting those animals. Experiments have since been instituted upon Cystic worms from different species of herbivorous ani- mals, and these all produce Tape-worms of different kinds when introduced into the bodies of carni- vorous animals. The administration of mature Fig. er ee sepments of Tape-worms to the herbivorous species, has also been found invariably to produce a development in the tissues of their organs of the corresponding Cystic worms; so that we may consider it a well-established fact, that the ova of the Cestoid worms are not, as a general rule, developed in the same species of animal which is infested by the mature Tenia. But, it may be asked, how does the embryc Tenia find its way from the stomach of its host, through the various tissues of its body, until it reaches the particular organ in which its development is to be carried on? This subject is still enveloped in a certain amount of obscurity; but some recent researches of Professor Van Beneden appear to throw a little light upon it. That zoologist observed that the embryos of a Tenia found in the intestines of the common frog, were furnished with six spinous organs, of which two were straight, and the other four slightly hooked at the extremity. By an action of the four-hooked spines, very similar to that of the arms of a man when swimming, the little creatures were enabled to push themselves through the broken tissues of their parent ; the two straight spines assisting to pierce a passage, and, no doubt, maintaining them in their position whilst the hooks were brought up for a fresh stroke. In this manner, as Professor Van Beneden observes, they would have no difficulty in penetrating any tissues, or in reaching any part of the body of the animals appointed for their further development. Professor Van Beneden appears to consider that the history of the Cestoid worms affords another instance of an “alternation of generations” analogous to that of the Meduse, referred to at page 252. In this view the Cystic worm (Scolex V. B.) corres- ponds with the simple Hydraform polype; the compound animal known as the Tape- worm (Strobile V.B.), with the elongated polype in process of division ; and the mature, separate segment ( proglottis), with the perfect sexual Medusa. An exception to this general rule appears, however, to be presented by the tape- worm of the human subject; at least, it is not easy to understand how the Cystic worms could withstand the heat usually employed in cooking our animal food. Recent experiments have shown that the administration of adult proglottides of Tenta solium to pigs, produces a great development of the Cysticercus cellulose (Fig. 72); but in what manner this parasite can be introduced into the human organism is still unknown. The Cysticercus cellulose is also found in the tissues of the human body. a 90 THE TREMATODA. Two species of Cestoid worms inhabit the human intestines—the Tanta solium and the Bothriocephalus latus. The former is the ordinary Tape-worm, the second occurs only in particular countries,—in Holland, Poland, and Switzerland. In the Cystic form some of these worms do great injury to domestic animals; one of the most noxious is the so-called Cenurus cerebralis, inhabiting the brains of sheep. Many other inter- esting facts are connected with the history of these animals; but our space forbids us from entering into further details. -Ornver II.—Trematopa, ‘General Characters.—These animals, which are all parasitic, present some re- semblance to the individual segments of which the Cestoid worms are composed. They are usually of an elliptical or oval form, and very flat; the skin is soft, but usually contains a number of calcareous granules. The whole body is very contractile. At one or both of its extremities it is furnished with suckers to.enable it to adhere firmly to its host, and -at “its anterior extremity with a mouth. At.a ‘little distance from the mouth the narrow intestinal canal usually divides into two, which mostly terminate in blind extremities; in some cases, however, the two intestines meet towards the hinder part, so as to form a complete circle. All these animals are hermaphrodites, and the history of: their development presents many points of almost equal interest with those exhibited by the Oestoid worms. ‘ Divisions.—Thcy form three families, In the first, the Distomide, the animals possess two suckers, of which the anterior contains the mouth. Of these the Fluke (Distoma hepaticum), which infests the livers of sheep, is a well-known example. ' Other species live in the intestines, the brain, and even the eyes, of other animals, The animals of the second family, the Tristomida, are furnished with three suckers ; two small ones at the anterior extremity, between which the mouth is situated, and a larger one at the hinder extremity. These worms principally infest the gills of fishes, as do also those of the third family, the Polystomida, characterized by the presence of several suckers at the hinder extremity of the body, whilst the anterior extremity is either entirely destitute of those organs, or only possesses a small one, in which the mouth is situated. This family includes the singular Diplozoon paradoxum—an animal which appears to be compounded, like the Siamese twins, of two perfect individuals, each containing precisely the same organs. Orpver III.—PLanaripa, This order indludes'‘most of the free Platyelmia, These animals are of an oval or elliptical form, and very commonly furnished with an extensible proboscis, springing from the ventral surface, and leading into a large digestive cavity, which gives off numerous ramifications into'the substance of the body, but possesses no anal opening. These animals are of a:gelatinous consistency, -and enjoy such a power of self-contrac- tion that they can reduce.their-whole substance to the form of a lump of jelly, in which condition they occasionally force themselves rather disagreeably upon the notice of incautious water-cress eaters, They inhabit both salt and fresh water, where they swim about rapidly by an undulating movement of the body, in the manner of a Jeech and creep with-great ease upon stones and aquatic plants, They are generally of anal size, but exceedingly voracious. Like the polypes, which they resemble in their gelatinous nature, they appear to be capable of almost: endless increase, by the way THE PLANARIDA. 91 which might be expected to lead to their destruction. Sir John Dalyell, in his observa- tions on these animals, speaking of the black Planaria (Planaria nigra), says that “ it is privileged to multiply its species in proportion to the violence offered to its otherwise delicate frame. It may almost be called immortal under the edge of the knife. Innumerable sections of the body all become complete and perfect animals. If the head be cut off, a new head replaces it ; if the tail be severed, a new tail is acquired.” Still more remarkable was an instance of spontaneous separation of the head of one of these animals, which took place under the eyes of the same observer. In South America, Dr. Darwin observed some terrestrial animals which approached the Planarie very closely in their characters; they lived amongst rotten wood, upon which'they appeared to feed, and were marked on the back with stripes of bright colours, The family of Nemertide, or Ribbon-worms, must be referred to in this place, as it probably forms the type of a fourth order of Platyelmia. It is composed of animals with elongated ribbon-like bodies, possessing 4a protrusible proboscis, a distinct nervous system, and a digestive canal with a distinct anus. As far as we know at present, the sexes are on distinct individuals. Amongst these one species, the Borlasia, inhabiting the coasts of France and England, attains a length of upwards of fifteen feet, This tremen- dous worm remains coiled up during the day under stones, going about at night in search of prey. The Turbellaride also—a family of minute worms inhabiting both salt and fresh water—appear to belong to this order. Like the preceding animals, they possess an intestinal canal with two openings, and the sexes appear to be separate. The classifi- . cation of these creatures is still, however, involved in great obscurity; and much still remains to be done before it can be brought to a satisfactory condition. ca ‘Crass II;—NEMaTEUMIA. General Characters.—The atiimals belonging to this class are of a more or less ‘elongated, cylinirical form, with the skin much thicker and stronger than that of the ‘preceding parasitic worms, ‘and generally wrinkled in such a manner as to give the body an annulated appearance. The nervous system, in the higher forms, consists — of'a pair of ganglia, situated in the anterior extremity, and united by a slender nervous ‘ring, which surrounds the esophagus; from these, two filaments take their rise, and run through the whole length of the body. In the lower orders no undoubted nervous ‘system has’yet been recognised. As far as our present knowledge goes, the Rownd- worms are unisexual ; the males, which occur far more rarely than the females, are always smaller than the latter, and usually present distinct copulative organs. Nosuch extraordinary metamorphosis as that which we ‘have seen to prevail amongst the flat “worms occurs in'the development of these creatures, which, however, are as yet but | ‘imperfectly known. They not only inhabit the intestines of other animals, but many | ‘species are also to be met with in the interior of completely closed organs, to which , ‘they must have obtained access in their earliest stages. Divisions.—The Nematelmia form three very distinct orders,—the Acanthocephala, which possess a proboscis armed with a formidable apparatus of hooks, but are apparently . destitute of an alimentary canal; the Gordiacea, long thread-like worms, with an intestinal canal, but without an anus; and the Nematoidea, in which’a perfect intestinal canal exists, 92 THE NEMATELMIA. Orprr I.—AcAaNTHOCEPHALA, This order, which includes only a single genus, is composed of parasitic worms often of considerable size, which find their habitation in the intestines of various animals, especially fishes. One species in particular, the largest in the order, is common in the intestines of swine, where it sometimes attains a length of eighteen inches. The body is thick, and divided into rings by a series of transverse wrinkles; the head is armed with rows of reversed spines, which not only serve to fix the animal in its abode, but also enable it to bore through the intestines of its unfortunate victim, who sometimes falls a sacrifice to this propensity of his uninvited guest. These creatures appear to possess no alimentary canal; their nourishment is entirely obtained by absorption through the skin, beneath which is a curious areolar structure, which is probably subservient to this purpose. : Oxver IJ.—Gorpiacra. The Gordiacea, or Hair worms, are at once distinguishable by the extraordinary length of their bodies (Fig. 73), which frequently present a close resemblance to a horse- hair; so close, indeed, that in former times the popular belief ascribed their origin to the introduction of horse-hairs into the water in which they are found. These animals live as parasites in the . = bodies of various species of insects, to Fig. 73.—Gordius Aquaticus. which their size is often so dispropor- a, tail. tionate, that when the worm is coiled up within the cavity of an insect’s body, scarcely any space is left forthe internal organs of its unfortunate host. Dr. Baird has recently described a species of Gordius from the common violet Ground Beetle (Carabus violaceus), an insect scarcely an inch in length, the worm being upwards of eleven inches; whilst other species, of which the victims are unknown, attain a length of about three feet. When mature they quit the bodies of the insects, at whose expense they have been nourished, and seek some piece of water or moist situation, where they deposit their ova in long chains. At this period they sometimes suddculy make their appearance in vast numbers in particular spots, giving rise to reports of worm rains. It seems probable that the evolution of the young proceeds to a certain distance in the situations where the eggs are deposited; but when, or in what manner, they afterwards obtain access to their destined victims, is still unknown. One of the most singular circumstances connected with their history is, that if, by any chance, on breaking out of their insect-home they find that dry weather has produced a state of things incompatible with their notions of comfort, they quietly allow them- selves to be dried up, when they become perfectly hard and brittle ; but, strange to say, the moment a shower of rain comes to refresh the earth with its moisture, the dormant Gordii immediately recover their activity, and start off in search of a suitable place in which the great object of their visit to solid earth may be effected. Oxpre III.—Nemaromera, With the exception of one family, all the worms included in the order Nematoidea are parasitic in the bodies, and principally in the intestines of other animals ; they are, in fact, amongst the most common and the most injurious of Entozoa. In the form of THE NEMATOID WORMS. 93 | their bodies they frequently resemble the common Garden-worm, although some are much more elongated, and often taper to a very fine point at one end; the skin is more or less wrinkled, giving them an annulated appearance. These are unmistakably the highest forms of intestinal worms; they present « distinct nervous system, an ali- mentary canal, furnished with a mouth and an anal opening, and distinct sexual organs. The history of the development of these animals is but imperfectly known. It appears probable that in many cases a different situation is required for the evolution of the young, to that inhabited by the mature animals; for at certain periods the latter, appa- rently impelled by some wandering instinct, quit the intestines, either by allowing themselves to be carried out along with discharged matters, or by actually boring through the walls of their habitation into the tissues beyond them. The object in the latter cases appears to be the deposition of their eggs in the blood-vessels of their host; at least, a species found in the frog deposits its ova in this situation, The young animals appear to be carried by the circulation to some position suitable for their development, when they inclose themselves in a minute capsule or cyst amongst the tissues of the body, and remain at rest for some time. On breaking out of this capsule they find their way to the intestines, where they remain until their instincts prompt them to imitate the example of their parents. This order includes the common Ascaris, or Round-worm of the human subject, as well as the little Thread-worms (Oryuris) which are often so troublesome to children. These are rarely injurious, unless present in great numbers. Far different is the case, however, with the Strongylus gigas, a worm sometimes attaining a length of two or three feet, and the thickness of a man’s little finger, which usually inhabits the Kidneys of swine, but sometimes finds its way into the same organ in man. This tremendous worm, by destroying the organ in which it has taken up its abode, is said not unfre- quently to cause the death of its host. This order also includes the dreaded Guinea-worm (Filaria medinensis), which appears to occur in most parts of tropical Africa. This worm lives in the cellular tissue beneath the skin, and between the muscles of man, confining its attacks Principally, though not exclusively, to the lower extremities, where it often produces considerable pain. It is said occasionally to attain a length of twenty or thirty feet ; but its average length is five or six. It is extracted by winding it very slowly upon some object, an operation in which great care is said to be necessary, as if the worm be broken its fluids produce a very painful effect. When arrived at maturity, the Filaria comes to the surface, where it breaks to pieces and sets free the innumerable young with which it is crammed. In this order we also place the Anguillulida, the so-called Eels of paste and vinegar. These are minute, thread-like worms, exhibiting distinct digestive and generative organs, which occur often in great numbers in putrefying substances. Cuass III.—ANNELIDA. General Characters.—The Annelida, in general, present a more complicated organization than any of the preceding animals; the division of the body into segments is usually distinctly recognizable, and the segments are almost universally furnished with external appendages, which are sometimes jointed. The majority live in water, or in damp situations; a very few only are parasitic in their habits. The head in most of these animals is distinctly marked, and furnished with organs of sense, such as eyes, tentacles, and in some instances auditory vesicles, containing 94 THER ANNELIDA. otolithes, The nervous system, in the higher forms, exhibits the articulate type of structure very distinotly ; it usually consists of a scries of ganglia running along the ventral portion of the animal, and united by a pair of slendor filamonts, by which thoy also communicate with the central mass, or brain, which is inclosed in tho head; this is composed of two ganglia, united by a ring surrounding the wsophagua, In tho lower forms the nervous system approaches that of the preceding classes, The lateral appendages, which sorve principally as organs of motion, aro vory Dorsal arch Dorsal onr Ventral member = Ventral arch =YVentral oar Fig. 74.—Tranavorse section of an Annelido (Amphinome). variablo in their structure and arrangement, somotimes ocourring on all tho sogments of the body, sometimes only on the anterior or on tho middle sogmonts; somotimos four and sometimes two in number on each sogmont, Thoy usually consist of lobes of skin, furnished with bundlos of bristles of very various forms, and with jointed cirri or tontaclos (Fig. 74); they also commonly bear the respiratory organs, or branchie (Fig. 75). In somo Annelida, as the Loechos, no traco of oxternal organs is to bo soon ; whilst in othors, na the Earth-worms, thoy aro reduced to a fow bristlos, which assist the animal in its progress through the earth. It is to bo 7 observed, however, that even in tho highest dmnelida the Fig. 75.—Foot and bran- jointed cirri are always oasily distinguishable from tho limbs chia of Eunice. of tho sccond section of the Artrowlata, 3, branchin; 0, clrrhus; ie ; aS % 7 t, bristle tuft; #, ventra Tho digestivo apparatus consists of a straight intestine, oirrhus. running through tho body from ono oxtromity to the other, The mouth is usually armed with jaws, and tho opposito oxtromity of tho intestinal canal always terminatos in an anal opening. Tho vascular systom is also very distinctly developed, and the nutritivo fluid is usually of a red colour, somotimes groon or yellow. The sexes are usually distinct, although a fow—as the Loochos and Earth-worms— are hermaphrodites ; but oven in these self-imprognation docs not take place. Somo Annelida appear to propagate also by spontaneous division; and many of thom can ro- produce parts lost by accidental injury. Divisions.—Tho Annelida may bo divided into two groups, charactorized by tho ‘presence or absence of external respiratory organs, The abranchiate Annclides includo two orders,—the Suctoria, or Loeches, characterizod by the posscasion of a sucking diso at the posterior, and usually also at tho anterior extromity; and tho Scolecina, or Earth- THE SUCTORIAL ANNELIDA. 95 worms, in which these suckers are wanting, but which are furnished with a double row of bristles along the under surface of the body. The branchiferous group is also divided into two orders,—the Tudicola, the animals composing which form a tube for their habitation, and the Errantia, which enjoy no such protection. Orpver I,—Sucrori, General Characters.—The animals belonging to this order, of which the common medicinal Leech (Fig. 76) is a familiar example, are characterized by the total deficiency of any lateral appendages ; their motions being effected by undulations of the body whilst swimming, or by the alternate attachment of the sucking discs with which the two extremities of their bodies are usually furnished. They all appear to live by sucking the blood of other animals; and, for this purpose, the mouth of the Leech is furnished with an apparatus. of horny teeth, by which they bite through the skin. In the common Leech three of these teeth exist, arranged in a triangular, or rather tri- radiate form, a structure which accounts for the peculiar appearance of leech bites in the human skin (Fig. 76, a). Each of these teeth has a minutely serrated, edge (Fig. 77), which, when worked back- x wards and forwards in contact with the skin, soon saws it through, v\ é when the teeth are retracted, and the blood is then pumped from ‘y the wound by the alternate dilatation and contraction of the muscular cesophagus. In the Clepsinide this structure disappears, giving way Fig. 77—Tooth of to a protrusible proboscis. The intestine is of very large size, and Wie Leech usually extends on each side into short blind sacs or processes, the distension of which, during the act of suction, must necessarily increase its capacity. Respiration appears to be performed by a system of aquiferous canals, lined with cilia, which open exterually, by a series of minute orifices, on each side of the body. The vascular system is wel! developed. Nearly all these animals are hermaphrodite. The deposition of the eggs is attended with some very singular circumstances. At the period of oviposition, a peculiar gelatinous band is produced round the anterior part of the body near the orifice of the generative organs, which is situated in this part. The Leeeh lays its eggs in this gelatinous matter; and when all are deposited it withdraws its Fig. 76.—The Common Leech (Sanguisuga Officinalis). _ body from the band, which then closes up, and forms a complete capsule, within which ' the eggs are inclosed. It appears, from a statement of M. Frémond, that (in addition . to these capsules, or cocoons, as they are called, containing a number of ova) the Leech also sometimes produces a “‘compound egg, formed of a transparent membrane, full of a . liquid, in which little globules soon begin to appear; these globules are, in fact, so many germs of Leeches, and during development take the form of little worms, which soon leave the egg by an opercular hole at its extremity.” The nervous system in the Suctoria is usually well developed ; and the anterior sucking disc bears a row of eight or ten eyes, which, however, appear to be of very imperfect construction. 96 THE LEECHES. Divisions.—This order is divided into three families, The first, the Malacobdel- lide, presents many points of resemblance to the Trematode worms; the mouth is unarmed, the substance of the body semi-transparent, the nervous system composed of a single ganglion and filament on each side of the body; and there is a single sucking disc at the posterior extremity. These worms live parasitically within the mantie of various marine bivalve Mollusca. In the Clepsinida, the body is of a leech-like form, but very much narrowed in front, and the mouth is furnished with a protrusible proboscis. These animals live in fresh water, where they may often be seen creeping upon aquatic plants. They prey upon the water snails (Lymnee). To the third family, the true Leeches (Hirudinide), the common medicinal Leeches belong. Two species of Leech are commonly used in medicine,—the Sanguisuga offci- nalis, a native of the South of Europe, and the 8. medicinalis, which is found princi- pallyin the northern countries of the same continent, and occurs, but rarely, in England. Most of the Leeches used in England are imported from Hamburgh ; but the pools and marshes in which the animals are collected are situated at a great distance from that emporium of the trade, in the thinly populated countries of eastern Europe,—Hungary, Bohemia, and Russia. The supply in these countries, however, appears to be nearly exhausted, and much of our supplies are now derived from regions still further to the east. The animals are caught by means of baits put into the water, or by the fishermen wading into the pools with naked legs. The importance of the Leech in medicine is well known; but few, perhaps, are aware of the enormous consumption of these Annelides that really takes place. Some idea of this may be formed, however, from the fact mentioned by Dr. Pereira, that some years ago “four principal dealers in London imported, on the average, 600,000 monthly, or 7,200,000 annually!” The annual con- sumption in Paris has been estimated at 3,000,000, and that of the whole of France at no less than 100,000,000. No other creature, so low in the scale of organization, gives rise to so extensive a commerce as this. The Leeches are sometimes imported in bags, but more frequently in small tubs, closed with stout canvas, to allow the passage of air. Each of these tubs contains about 2,000 Leeches. But if the medicinal Leech puts forward a strong claim to our attention, on the ground of the services which it renders to mankind, there are others which force themselves upon our notice from the very opposite consideration. These are principally confined to hot countries, where, however, they are often great pests. In Egypt, during the invasion of that country by Napoleon, the French soldiers were often exposed to great torment from the numbers of Leeches infesting the pools. When the men, fatigued with their march under the burning sun, rushed eagerly to drink, these bloodthirsty animals would fix themselves to the interior of the mouth or nostrils, producing intolerable annoyance to men already half-maddened by vexation and fatigue. A still more remarkable instance is afforded by the small Leeches which infest Ceylon. These animals are about an inch and a half in length. They live principally in the forests, amongst the dead leaves, in damp places; but often make their appearance in other parts of the island during wet weather. Wherever they occur, however, they seem always to be on the look-out for blood; and some instinct tells them that, even under the clothes of Europeans, this wished-for delicacy is to be obtained. The incau- tious invader of their domain soon feels a peculiar sensation of moisture about his legs ; and, on examining into the cause, he finds, to his dismay, that they are bathed in blood; oy THE SIPUNCULUS. 97 should he, by chance, wear white trousers, he may perhaps receive the first horrifying intelligence of what is going on, by the sudden appearance of red stripes upon his nether habiliment. If the traveller, made wise by experience, should resort to the expedient of tying his trousers round his boots, or (which is said to to be the best course) his boots over his trousers, the little blood-suckers will mount still higher in search of their manorial rights; and an unpleasant dabbled sensation about the neck soon shows that the enemy has succeeded in scaling the citadel. The legs of horses, passing through the districts infested by these pests, are frequently completely covered with blood in consequence of their attacks. Some species of this family, forming the genus Piscicola, live as parasites upon various fresh-water fishes; whilst those of the genus Branchiobdella, which are quite destitute of eyes, inhabit the branchie of some Crustacea. This appears to be the proper place to allude to some singular marine animals | which have been placed, by some zoologists, amongst the Echinodermata, by others amongst the Annelida. These are the species of the genus Sipunculus and its allies, which constitute an order of animals for which the name of Gephyrea has been pro- posed, in allusion to the apparent connection which they establish between the Echino- dermata and the articulate series. Their bodies are cylindrical, and rather thick, covered with a tough skin, in which a few bristles are sometimes inserted, but which neither contains calcareous particles nor the tubular sucking feet of the true Echinoderms. Their habits are very similar to those of the common lob-worms, and like these they are much sought after as baits by the fisherman. They live in the sand, where they move about, much in the same way that the common garden worm does in moist soil; they are destitute of eyes and other organs of sense, and the mouth is armed with a curious proboscis. Some species, as the Sipunculus Bernhardus, here represented (Fig. 78), seek protection by inclosing their bodies in the abandoned dwelling of some univalve Mollusc ; whilst others, for the same purpose, actually hollow them- selves caves in the substance of stones and corals. One of these, to which M. Valenciennes has recently given the name of Sipunculus cochlearius, is remark- able for a habit of forming a small spiral cell in the stony substance of two very different species of coral, This animal is probably troubled with a tender skin, and, in order to prevent abrasion by the rough walls of his coral home, he lines it with a smooth vitreous matter, producing an appearance which has so deceived zoologists, that they have supposed that the ‘Fig. 78.—Sipunculus Bernhardus. corals had built their structure around some small shell, and hence, confounding the two species, described them both under the common name of Madrepora cochlea. Orper II.—Scozecma. General Characters.—Of this order we have several well-known examples in the Earth-worms so common in our gardens and fields. The bodies of these animals are of a cylindrical form, somewhat pointed at the anterior extremity, and usually a little 98 THE LUMBRICID, flattened at the tail, The skin is tough, and divided into numerous segments by transverse wrinkles, and the organs of motion are reduced to tho form of a double row of bristles, ramming down the lower surface of the body, which, instuad of being placed, as in the following orders, upon prominent lobes of the skin, aro usually capable of being retracted within small hollows when not in use. The mouth is unarmed, and tho intestine runs straight. through the body. The vascular system: consists of two longi- tudinal vessels running along the ventral and dorsal regions of the body, and united by numerous branches. ‘The blood is red. Like the Leeches, these worm s aro furnished with ciliated canals, which have been supposed to servo as organs of respiration; but their real destination appears to be still uncertain, Like the leeches, also, they are all hermaphrodites. Divisions.—This order contains two families—the Lumbricide or Barth-worms, and the Naidide. The former are too well known to require much description ; they possess no distinct head, and are quite destitute of eyes; their bristles are hovked, and placed in little tufts in pits on the lower surface, whence they can be exsorted when the animal requircs their assistance. They live in holes in moist carth, and are said to be predacious animals, although popular belicf charges them with the destruction of the roots of plants. Mr. Darwin has asserted that, even if these worms do some damago to vegetation, by feeding upon the tender roots of young plants, yet they amply com- pensate for this by the sort of tillage which they givo to the soil in constantly passing through it. It is generally supposed that the Earth-worm may be propagated by division; but this scarcely appears to be the case, It is said, however, that if it be divided across tho middle, the part bearing the head will develop a new tail, although the tail will soon die; and that, if the head be cut off, the body will form a new head; but it appears that both portions never survive this mutilation, This power of reproduction of lust parts is carried to a much greater extent in the Natdide, which even propogate by a kind of gemmation. These animals live princi- pally in the mud of fresh-water ponds and rivera, In their form they resemble tho common Earth-worm; but their bodies are furnished, besides the ventral bundles of bristles, with a series of long spines on each side. ‘They generally have two distinct eyes, and the mouth is sometimes armed with a long proboscis, Oxnver T&—-Tvsicors, General Characters.—The worms belonging to this order, which commences the series of branchiferous Annelida, are all marine, and are distinguished by their invariable habit of forming a tube or case, within which the soft parts of the animal can be entirely retracted. This tube is usually attached to stones or other submarine bodics, It is often composed of various forvign materials, such as sand, small stones, and the debris of shells, lined internally with a smooth coating of hardened mucus ; in others it is of a leathery or horny consistency ; and in some it is composed, like the shells of tho Mollusca, of calcareous matter secreted by the animal. These animals frequently livo together in societies, winding their tubes into a mass which often attains a considerable size; others are more solitary in their habits. They retain their position in their habita- tions by means of appendages very similar to those of the free worms, and furnished, like these, with tufts of bristles and spines; the latter, in the tubicolar Annclides, are usually hooked ; so that, by applying them to the walls of its domicile, the animal ig enabled to oppose a considerable resistance to any effurt to draw it out of its hole, THE TUBICOLAR ANNELIDA. 99 In these, as in the preceding Annelida, no distinct head can be recognised, and the eyes are cither entirely wanting or very rudimentary. The mouth also is generally unarmed, The anterior extremity is always furnished with tentacles, which serve both as organs of touch and for the capture of prey. The nervous system is well- developed, although the longitudinal filaments generally run down the sides of the body, instead of being united by ganglia in the middle line. The branchiz are usually con- fined to the head, where they appear as branched organs in the midst of the tentacles ; they sometimes also occur on some of the segments of the body. All these worms are unisexual, They deposit their eggs in a mass of mucus, which usually clings to the tube of the parent animal. The young Zerebella, on the first breaking out of the egg, is a small globular embryo, thickly covered with cilia, By degrees this elongates into an oval form, and the cilia collect in a band round its middle. The lengthening process continues, and in a little time a pair of small eyes make their appearance in the head, whilst a new set of cilia are developed at the caudal extremity. Still the little animal con- tinues elongating ; the cilia are reduced to a little band, like a cravat, round its neck, and a patch on the back, whilst the body exhibits traces of annulation, and single bristles begin to sprout from its sides. At last the cilia disappear altogether; the members acquire sufficient development to enable the young Terebella to creep along the bottom of the water. It selects a spot for its perma- nent abode, fixes itself, builds its house, and becomes,. after its brief “Wanderjahr,” a quiet, home-staying denizen of the deep. Divisions.—In the best mown family of this order, the Sabellide, the branvhie are placed on the head, where they form a circle of plumes (Fig. 79) or a tuft of branched ' organs. Of the tentacles, one is usually much thickened, so as to form a sort of plug, which closes the aperture of the tube when the animal is retracted. The Serpule, which form irregularly twisted calcareous tubes, often grow together in large masses, generally attached to shells and similar objects; whilst those genera which, like Terebella (Fig. 80), build their residences of sand and stones, appear to prefer a life of single blessedness. The curious little spiral shells, often seen upon the fronds of : sea-weeds are formed by an animal belonging to this Fig. 79.—a Groupof Serpule. family (Spirorbis). tog The Hermellide, some of which live amongst the oyster-beds, and often do much Fig. 80.—Lerebella, mischief by the increase of their masses of tubes, also belong to this order. 100 THE ANNELIDA ERRANTIA. Ornprr JY.—ERRantTis. General Characters.—We now come to the last and highest order of the Annelida, comprising those animals in which the external appendages of the body attain their highest development, whilst the power of free locomotion indicates the possession of a higher degree of general intelligence than would be necessary for the sedentary animals of the last order. It must be confessed, however, that in their struc- ture, and especially in their development, they display a a very close relationship to those animals; the history m. ayy of the development of the young in the two orders 6 Vi " being so very similar, that one description will serve ™~ “we for both. The head of these worms is distinctly marked, and the mouth is generally furnished with jaws of some Fig. 81.—Head and Trunk of Gly- kind, which are not unfrequently placed at the ex- een a apres tremity of a protrusibleproboscis(Fig.81), Thegeneral opening of the mouth; m m, structure of the lateral appendages and branchie has Jaws. already been explained at p. 284; but the parts of which these are composed frequently exhibit the most extraordinary forms. Like the Tubicola, all these worms are unisexual ; the ova are usually deposited upon stones or aquatic plants; but, in some instances, the mother carries them about enveloped in a slimy matter. Divisions.— Amongst the numerous families into which this order has been divided, the one which approaches most closely, both in structure and habits, with the lower worms, is that of the Arenicolide, including the common Lo}-worm, so much used Fig. 82.—Arenicola Piscatorum. by sea fishermen as a bait. This animal is found on all sandy parts of the coast, where it bores into the sand left wet by the retiring tide; its head is large and rounded, quite destitute of eyes or tentacula, and furnished with a short unarmed pro- boccis. The feet are very small, and confined to the anterior part of the body ; whilst the branchial tufts, which are of considerable size, are placed on each side of the middle segments, The family of Aphroditide, some species of which are known as Sea- mice, includes some marine animals of great beauty. In these worms the body is generally broad, or ovate, the head small, and furnished with very short tentacula; the feet large, with immense tufts of bristles and spines, often of the most remarkable forms, and exhibiting the most bril- liant metallic colours. Each of these hairs (Fig. 83) is retractile within a horny sheath, which serves to protect the soft Fig. 83.—Aphrodita hispida. THE ANNELIDA ERRANTIA. 101 parts of the animal from injury by its own weapons. The most remarkable peculiarity of these animals is, that their dorsal surface is entirely or partially covered by a double series of large membranous scales attached to the alternate segments, between which the beautiful bristles of the feet make their appearance. These animals generally inhabit deepish water ; but numbers of them are often thrown upon our coasts after a storm. The family of Nereide includes some elongated and distinctly annulated worms, which possess a well-developed head (Fig. 84), furnished with tentacles and eyes, and a mouth with a proboscis, which is sometimes unarmed, sometimes furnished with two or four teeth, The cirri or tentacles attached to the feet are often of considerable length, Fig. 84.—Nereis, with its head and some of the anterior segments, and sometimes even annulated (Fig. 85). The animals frequently present the appear- ance strongly resembling that of the more elongated Myriapoda. The branchial tufts are but slightly developed. In the next family, the Eunicide, on the contrary, these organs (Fig. 75) are of considerable size, and the mouth is armed with from seven to nine toothed jaws. This family includes some species of large size: the SP eee serene nae weeny grows to four or five feet; and others, found in the Southern Ocean, are said to attain double that length. Zoologists also place in this order a curious terrestrial Annelide, found in the West Indies by the Rev. Lansdown Guilding, and described by him under the name of Feripatus (Fig. 86). In its general appearance it exhibits a most striking resem- blance to the well-known Juli, or Millepedes; the body is distinctly annulated, the head well marked, and furnished with two jointed tentacles and eyes. Along each side of the body runs a series of soft feet, which, however, aoe traces of annulation; and these, as in the other free Annelida, are terminated by tufts of bristles, This curious genus forms the family Peripatide. The order of Annelida Erran- tia also includes another family, which appears to possess a Fig. 86.—Peripatus. striking affinity to the following class, the Rotifera. This is the family of the 102 THE ROTIFERA. Polyophthalmide, consisting of cylindrical worms, furnished with bristle-like, feet, somewhat resembling those of the Scolecina. Each segment of the body is said to bear a pair of eyes, whence the name given to the genus and family to which these creatures belong, The most remarkable character presented by these animals is the structure of the head, which bears a pair of lobes covered with cilia, which, like the similar organs of the Rotifera, can be retracted and protruded at pleasure. From these, we pass naturally to the last class of this subdivision of the Articulata, the Crass IV.—Rorirera. General Characters.—This interesting class of microscopic aquatic animals, included amongst the Infusoria by Ehrenberg, is now generally admitted to belong to the Articu- late division. They are animals of very diverse forms, but are always characterized by the | possession of ciliated organs at the anterior extremity (Fig. 87), by means of which they produce a vortex in the water, which carries to their mouths any minute animals or plants which may be floating in their neighbourhood. The skin exhibits distinct indications of trans- verse wrinkles or folds, by the agency of which the animals are enabled to contract themselves to an extraordinary extent, so that they often acquire an almost globular shape. In some cases, however, the skin becomes horny, or asmall quantity of silicious matter is fixed in it. In either cage the skin then forms a sort of carapace, within which the little animal can retreat in case of danger. Many of them pass: their lives fixed in one place like polypes, whilst others enjoy the power of swimming freely about. The free species are all furnished with some means of fixing themselves when about to feed. In some cases the tail terminates in a sort of sucker ; in others, in a pair of minute forceps, by which the little creature attaches itself to eis a eel eo ectet, . wil e wheels expanded ; ith th its resting place. ‘wheels folded up and aren cies the As might be expected from their minute size, peas oe Spolss i he wheels; ; é a % -! 3 @, mast few of them exceeding a line in length, and ratus 3 e, calvary glands ; 77, intestinal i * canal; g, its dilated termination - some being no more than sooth of an inch, the glandular apparatie ereeoa ding’ Pa nervous system in these animals has not been _¢, young ones nearly complete ; k, eges; made out very distinctly. It appears certain, » tail, however, that a pair of ganglia always exists in the neighbourhood of the head, and, that from these a little filament runs down each side of the body. The head also possesses from one to four eyes, usually indicated by their red colour; these, as usual, disappear in the sedentary forms; although their young, which are endowed with the powers of, locomotion, possess them. ; _ The structure of the alimentary canal is wonderfully complex, considering the THE ROTIFERA. 103 minute size of the creature possessing it. Within the mouth is a wide hollow, at the bottom of which the entrance to the gullet is seen; this is armed with a singular apparatus of teeth, set in motion by muscular action, and ready to seize upon any particles of food that may be carried into the mouth by the external vortex. The water introduced is sometimes carried off by a minute canal, situated close under the head; in other cases it is allowed to find its way out as it can. The teeth, in some Rotifera, are in the form of acute spines,—these are predaceous animals, and exhibit as much ferocity, in their way, as can be shown by creatures infinitely their superiors in size; in others they constitute small horny plates, furnished with transverse ribs; and these are usually vegetable feeders. Close to this apparatus are « pair of glandular bodies, which, apparently, discharge their secretions into the cesophagus at that point ; these are regarded as salivary glands. From these the intestinal canal extends through the body, inclosed in a thick granular mass, till it nearly reaches the caudal extremity, at which point the anal opening is usually situated. The Rotifera appear to be perfect self-impregnating hermaphrodites, and the ova in most of them appear to be developed within the body of the parent, until the principal organs of the young animal are quite recognizable. Their powers of reproduction are most extraordinary. Ehrenberg relates that in three days the progeny of a single specimen of Hydatina senta (Fig. 88), which he had isolated, amounted to no less than twenty individuals; a rate of increase which in ten days would give upwards of a million of specimens. That author adds, that “if two instead of four were produced daily by each individual, a million would be called into ex- istence in twenty days; and on the twenty-fourth day we should have 16,777,216 animalcules.” But wonderful as is the fecundity of these animals, when placed in fayour- able circumstances, not less so is their power of resisting the action of drought, which might otherwise, by drying up the water of their habitations, involve the whole or the greater part of their species in destruction. It is found, however, that these little creatures may be dried completely and repeatedly, until their bodies are so brittle that the slightest touch would crush them, and that on the return of moisture they will again spring into ex- _—Fig. 88. —Hydatina Senta. istence, unfold their little wheels, and give rise to a fresh u, rows of cilia; 5, muscles of generation. the jaws; c, stomach; d, en- eee ' larged termination of the in- Divisions.—The Rotifera form two orders, the testine; e, anus; f, salivary Sessilia and the Natantia, the names of which speak for £12048; 9 ovaria; f, dorsal themselves. Onvrr I.—Sxssiz1a, In the sessile Rotifera the body is continued into a longish stalk, which is attached, by its hinder extremity, to some aquatic plant or other object. The rotatory organ, in these animals, has generally a disc-like form, with the margin more or less notched. This order includes two families, the Floscularide, which have bent spiniform teeth at 104 TILE ARTHROPODA. he orifice of the csophagus; and the Meyalotrochida, in which that organ is armed with ribbed plates for the trituration of the food. Orver II.—Narantia, In this order, which, as its name implies, includes the free swimming species, the caudal extremity terminates either in a sucker-like organ, or in a small pair of forceps, by means of which the animals are enabled to fix themselves at pleasure, so as to set their rotatory organs in action, ‘These are also divided into two families, the Polytrochu in which the rotatory organs take the form of several lobes surrounding the anterior extremity of the body; and the Zygotrocha, which possess only a pair of ciliated pro- cesses placed on each side of the mouth. Susprviston I].—ArtrHroropa, on TRUE ARTICULATA. General Characters.—We now come to the second subdivision of the Articulata, in which the division of the body into segments appears with great distinctness, This single subdivision contains a greater number of species than all the rest of the animal kingdom put together; and as the number of individuals of each species is usually enormous, the part assigned to them, in the economy of nature, is, in spite of their gene- rally insignificant size, by no means an unimportant one. They swarm in every situation, and in every part of the earth, The plants and trees of every region nourish myriads of insects; the waters are everywhere alive with them, Their existence and its effects force themselves upon our notice in whatever direction we turn; vegetation is kept in check by their ravages; our own persons and the bodies of our domestic animals are not exempt from their attacks; whilst, as if to make up for any evils they may inflict upon our race, multitudes are constantly at work in the removal of decaying matters, which, if left to the natural progress of decomposition, would contaminate the air with their pestilential effluvia. Nor are they without some species that are of direct service to mankind. Many species of Crustacea are reckoned delicate articles of food ; the Silk-worm, the Honey-bee, and the Cochineal insect, furnish us with valuable pro- ducts; and many others contribute more or less to the comfort or the luxury of mankind. The principal general characteristic of these animals, and that which serves at once to distinguish them from those of the preceding subdivision, consists in the division of the body and limbs into numerous distinct rings or segments, moveably articulated together, and thus forming a sort of external skeleton, which not only protects the internal soft parts, but, by giving firm points of attachment to the muscles, enables their movements to be executed with much greater rapidity and precision than those of the vermiform classes. In a few species (the Myriapoda, see Fig. 3) these segments (with the exception of those at the two extremities), like the indistinct rings of the Annelida, are mere repetitions of one another, each segment being of the same form, and bearing the same organs, as its neighbour; but the complete articulation of the segments both of the body and limbs in these animals precludes all risk of their being confounded with the members of the lower class. In the majority of the Arthropoda, however, some of the segments are always developed differently from the others, generally giving rise to adivision of the body into three principal regions, the head, thorax, and abdomen; the appendages sometimes occurring along the whole series of segments ; sometimes being confined to particular regions of the body. THE ARTHROPODA, 105 As might be expected, from their increased capacity for motion and enjoyment, the amount of intelligence possessed by these animals is much greater than in any of the groups to which our attention has hitherto been directed; and the nervous system, of course, exhibits a corresponding advance. The general conformation of these organs has already been described (page 199, Fig. 5); and we have seen that, in the highest forms of worms, this structure is distinctly recognizable; but in the present group centralization takes place to a much greater extent, and the modifications of the original type are sometimes very considerable. As a general rule, it may be observed that, in proportion as the different segments of the body resemble each other, the nervous system approaches the original type; but that it deviates more and more from the typical structure in proportion as some of the segments preponderate over the rest. The appendages of the segments forming the head are converted into masticating organs ; and the number of those, of course, varies with the number of segments which may be supposed to form that region of the body. As these are merely metamorphosed limbs, and indeed generally exhibit their relationship to the organs of motion in their articulated structure, it is evident that, like the true limbs, they will be placed in pairs, one on each side of the middle line of the body ; hence their action is always horizontal, and the opening of the mouth may be considered to be vertical. The head is also usually furnished with one or more pairs of jointed organs, called antenne, which evidently act as organs of sense, and probably have different functions in different groups. Their structure often furnishes important characters for the discrimination of the minor groups into which these animals are divided. Except in a single class (the Insects,) the segmentary appendages are developed only on the ventral surface; but in these other appendages they are also articulated to the back, forming the wings with which, as is well known, those animals are provided. -Divisions.—Numerous as these animals are, they may be divided into four classes, and these are generally very easily distinguishable. The first, the Crustacea (Fig. 89), possess antenne, and are furnished with jointed appendages on all the regions of the body. Their respiration is aquatic. Some of them : p only exhibit the distinguishing characteristics of the class in their earlier stages. The second class Fig. 89.—Sandhopper (Talitrus). containing the Spiders (Arachnida, Fig. 90), is j . characterized by the absence of antennmw, by the ‘ Fig. 90.—Mygale. possession of four pairs of limbs attached to the - mas anterior portion of the body, which consists of the head and thorax fused together. 106 _THE CRUSTACEA. The third class, the Myriapoda (see Fig. 3), contains air-breathing animals furnished with antenne, with appendages on all the segments of the body; whilst the fourth, containing the innumerable hosts of Insects (Insecta, Fig. 91), is characterized by its Fig. 91.—Stag Beetle. aérial respiration; by the division of the body into three very distinct regions (of | which the middle one, the thorax, bears three pairs of jointed legs, and usually two | pairs of wings); and by the possession of a single pair of jointed antenna. Cuass V.—CrusTAcEa. General Characters.—If this class included only the ordinary well-known forms, such as the Crab and Lobster (Fig. 92), and their allies, there would be little difficulty in giving it an exact character, which should apply to every member of which it is composed ; but many of the lower forms cannot be said strictly to come under even the brief definition given above, although, in the earlier stages of their development they agreé so exactly with some of the most highly organized animals belonging to the class, that it is impossible not to admit them into the same category. Our description of the class, as a whole, must consequently be liable to many exceptions. The form of the body in these animals is excessively variable; it is usually some- what spindle-shaped, and divided into a series of distinct rings, articulated together, and allowing of a considerable amount of movement. These segments are sometimes of nearly equal size, and furnished with nearly similar appendages throughout (Fig. 89). Sometimes a few of the segments acquire a greater degree of development than the rest, and the organs of motion are confined to these, whilst the appendages of the other segments are reduced to a more or less rudimentary condition ; and in the higher forms the anterior segments become fused into a single mass, called the cephalothoraz (Fig. 92), which bears the mouth and organs of motion. The skin is generally hardened by a calcareous secretion, constituting a complete cutaneous skeleton, within which all the soft parts of the body are inclosed; the segments are united by 4 thin membrane which gives flexibility to the whole armour. As the animal has no power of adding to THE CRUSTACEA. 107 the size of this shell to make room for its increasing growth, it casts off its old coat Fig. 92.—Spiny Lobster (Palinurus). at stated periods, and secretes a new deposit of calcareous matter over its entire surface. The form of the attidulated appendages varies exceedingly. The first segment of the head, which is occasionally distinct from the rest, is sometimes provided with a pair of moveable stalks, on the summit of which the eyes are situated ; the second and third segments bear the antenne, of which two pair are usually present. These organs generally consist of a long tapering series of short joints, supported upon two or three large articulations, similar to those of the limbs, which enable them to move freely in every direction. The appendages of the following segments are generally formed into masticating organs. They often, however, gradually approach the true limbs in their structure; and the hindmost pair or two are generally denominated foot-jaws by zoologists. 108 THE CRUSTACEA. ; In the common Cray-fish (Figs. 93, 94) six pairs of these appendages are present, of which the three last are considered as foot-jaws. These are followed by the legs, the true organs of motion, which are also attached to the under surface of the thoracic SS Sren) Fig. 94. Fig. 93,—Cray-Fieh : @ and 8, antennw; ¢, eyes; d, organ of hearing ; e, external foot-j ; pair of thoracic members 3 9, fifth pair of thoracic members 3A,al dominal falee-lege; i, ian Jj, anus. Fig. 94.—Masticatory Apparatus, composed of six pairs of appendages : a, mandibles; & and e, first and second pairs of maxille; @ e f, three pairs of foot-jaws, graduall ain r Piece H A Pp jaws, gr Y approaching the form of segments, or of the cephalothorax in the Crabs and their allies, The number of these varies, of course, with the number of thoracic segments. In the Cray-fish and Lobster (already figured), there are five pairs of these organs, the anterior pair being often de- veloped into large pincers ; and the true feet are often followed by a series of rudimentary abdominal members, which sometimes serve to protect the ova, when these are carried under the tail, and sometimes bear external branchiez. By means of these limbs many of the Crustacea are enabled to run with great swiftness, whilst others have the extremities flattened so as to form fin-like organs. Many bury themselves with great rapidity in the sand, by the action of the feet, at the approach of danger; and the species furnished with pincers make use of these often-formidable weapons both to seize their prey and to attack their enemies. The nervous system of the Crustacea always consists of a series of ganglia running along the ventral surface of the body, united to each other, and to a cephalic ganglion SENSES OF CRUSTACEA. 109 or brain, by a pair of nervous filaments, and giving off nerves to the various organs in their neighbourhood. The development of these ganglia, however, often varies greatly in different segments; for, although in the more uniformly articulated forms the ganglia are nearly equal in size, those in which the thoracic segments are amalgamated have the whole of the nervous centres of these segments fused into a single mass, from which nerves are given off in every direction (Fig. 95). The cephalic ganglion is always situated above the cesophagus, and furnishes nerves to the organs of the senses. These are the eyes, the antennz, and in many cases organs of smell and hear- ing. The eyes present very different de- grees of development in the different i orders of Crustacea. The lower forms possess only simple eyes, containing a single lens, surrounded by a mass of = pigment, and receiving a single nervous Fig. 95-—Nervous eystem of Crab (faia). filament. Many of the lower Crustacea ea, upper part of the shell laid open; a, antennez; y, possess only one of these organs, which Cee ae eae ean eee vomite raere. is then placed in the middle of the head. nerves; ¢, thoracic ganglionic mass; np, nerves of In others « number of these eyes are eae sce brought together at a single oie but each eye is still distinctly recognisable, furnished with its own lens, surrounded by its own pigment spot, and receiving its own branch of the optic nerve. In the highest Crusta- cea the visual organs become true facetted compound eyes, similar to those of insects ; and these are often supported upon a footstalk, which is sometimes of considerable length (Fig. 98). The organs of hearing (which are probably common to all the Crustacea, although they have Fig. 96.—Podophthalmus. been investigated principally in the highest order) are situated close to the base of the long external antenne. In the Cray-fish (Fig. 93), they have the form of a cylindrical hollow process, which is closed internally by a thin membrane, or dram. Behind this is a vesicle filled with fiuid, which receives the termination of a particular nerve. The organs of smell, which have been observed principally upon the Crabs, are in the form of cavities situated at the base of the inner pair of antenn#, and lined with a mucous membrane. The external orifice of these cavities is surrounded by fine bristles—no doubt to exclude in- 110 ANATOMY OF CRUSTACEA. jurious particles from the interior. The antennz appear to be principally organs of touch ; in many cases they are employed as natatory organs. The digestive canal in the Crustacea generally exhibits a high degree of develop- ment. It runs from the mouth to the posterior extremity of the body, and consists of a very short cesophagus, opening into a large stomach, which is often armed with rows KOA a \ 4 NN i Fig. 97.—Anatomy of a Crab; the greater part of the carapace having been removed. Pp, portion of its lining membrane; c, heart; as, opthalmic artery; aa, abdominal artery; }. branchie in their natural position; 61, branchiw turned back to show their vessels; 7, lower portion of the shell; f, appendage of the foot-jaw; e, stomach; m, muscles of the stomach; Fo, liver. of teeth; from this an intestine runs to the anal opening, The liver is generally of large size. The respiratory organs consist of branchiw of various forms, sometimes attached to the abdominal members, sometimes inclosed within a cavity on each side of the cephalo- thorax, in and out of which the water passes by two openings. Circulation is effected by means of a regular system of vessels; the heart consists of a single contractile cavity, situated in the middle line of the back; the arteries, in the higher forms at least, are closed tubes; but the venous blood passes back through spaces left between the organs of the body, until it reaches peculiar cavities situated at the bases of the legs (Fig. 98), whence it passes into the branchie, and thence, when aérated by contact with the water, through proper vessels to the heart. With the exception of a single order, the Crustacea are all unisexual animals. Their reproduction always takes place by ova, which are generally attached to the tail of the female for some time after exclusion. Indeed, in some species, the eggs are hatched in this position, and the young continue for a certain period to shelter themselves beneath the body of the mother. Their development presents many curious phenomena, In some species the young leave the egg in very nearly the same form that they are to METAMORPHOSIS OF CRUSTACEA. 111 retain through life; whilst in others, nearly allied to these, the young animal at its first coming into the world has a form so totally distinct from that which it is destined to.assume, that nothing but absolute observation could lead to a suspicion of its true parentage (Fig. 99). So different, in fact, is the appearance of the young of many of Fig. 98.—Verticai section of a Crustacean, showing the course of the blood. c, heart; s, venous sinus; va, vessels conducting the venous blood to the gills; ve, vessels which collect the aérated blood from the capillaries of the gills; Fig. 99.—Early form of Crab vb, branchiocardac vessels ; f, carapace; st, sternum. (Zoea). the Crustacea from that of the mature animals, that before the connexion between them was discovered several species, and even genera, were established upon these embryonic forms. It is singular that this metamorphosis takes place amongst both the highest and the lowest members of the Crustacea; and that some of the latter, in which, in the mature state, most, if not all, the ordinary characteristics of the class completely disappear; yet, in their earlier stages of development, exhibit the most perfect resemblance to the most highly endowed of their relatives. Divisions.—The immense number and variety of Crustaceous animals necessi- tates, as might be expected, a corresponding multiplicity of subordinate divisions. Five principal groups, or sub-classes, may be recognised. Of these, the first, the Cirrhopoda, is coraposed of animals, which, until the history of their development was known, were always ranged by naturalists amongst the Mollusca. When mature, they are always attached to submarine bodies. Their bodies are inclosed in a shell composed of several calcareous plates, from an opening in which they protrude a bundle of arti- culated cirri. The Entomostraca, forming thé second sub-class, are generally of small size, covered with a delicate skin, and usually protected by a broad shield or a sort of bivalve shell, The branchiz, when present, are attached to the feet, which, with the antennx, are generaily furnished with bristles, that render them efficient organs of locomotion. Many of them, when full grown, attach themselves, as parasites, to the bodies of other aquatic animals ; and these frequently lose all resemblance to the other members of the class. The satienals of the third sub-class, the Xyphosura, are covered with a hard calcareous carapace, and the tail forms a long, sword-shaped spine. The mouth is furnished with no jaws, and the operation of mastication is performed by the basal joints of the true feet. The fourth sub-class, the Podophthalmata, is at once distin- 112 CIRRHOPODA—BARNACLES, . of the Barnacle. guished by the pedunculated eyes and amalgamated thoracic segments of the animals composing it; whilst those of the fifth, the Edriophthalmata, on the contrary, have the eyes sessile, and the thoracic segments distinct. These sub-clssses are again divided into orders, to which we must advert as briefly as possible. Svus-Ciass anp Onper I.—Crruoropa. General Characters.—The first sub-class includes only a single order. They are all marine animals, which, when mature, attach themselves to rocks or other sub- marine objects ; the common Barnacle, perhaps the best known example of the order, generally selecting floating objects for this purpose, and frequently covering the bottoms of ships to such an extent as even to impede their progress through the water. The bodies of these ani- mals are soft, and inclosed in a case composed of several calcareous plates; they formed part of the group of multivalve shells of the older conchologists. The limbs are converted into a tuft of jointed cirri, which can be protruded through an opening in the sort of mantle which lines the interior of the shell. The cirri are . twelve in number, and beset with bristles. aa Mig. 100-— Shell When the animal is alive they may be seenin Fig. 101. s body, of the continual motion, exserted and retracted every os moment in search of prey. The intestinal canal is complete, furnished with a mouth and an anal opening; and the nervous system exhibits the usual series of ganglia, which we have seen to be characteristic of the arti- culate type. The head is marked only by the posi- tion of the mouth, which is armed with a pair of jaws; but all traces of any of the organs that we are accustomed to see at this part of the body have completely disappeared, In their very earliest days, however, these crea- tures are by no means s0 ill provided; they are then furnished with eyes, antennz, and limbs, and are as active as any of the minute denizens of the sea. It is only after a certain period of wandering that they fix upon a place of rest, — fix themselves, and become = res- pectable house- holders. All these animals are hermaphro- dites; but, according to the researches of Mr. Darwin, active individuals, which he calls complementary males, are produced at certain periods, to assist in the impregnation of the ova of the hermaphrodite individuals, Fig. 102.—Young of Cirrhopoda, BARNACLES. 113 Divisions.—The Cirrhopoda are divided into two families. In the first, the Lepadide, or Barnacles (Fig. 103), the animals are attached to their resting-place by a flexible stalk, which possesses great contractile power. The shell is usually composed of two triangular pieces on each: side, and is closed by another elongated piece at the back, so that the whole consists of five pieces. The young of the Barnacles usually present the appearance represented in Fig. 1026. The second family, the Balanida, or Sea Acorns (Fig. 104), includes the sessile Fig. 104.—Balanus. Fig. 105.—Shell. of Balanus. species, whose curious little habitations may constantly be met with upon the rocks of the sea-shore, and not unfrequently upon many species of marine shells. The shell (Fig. 105) forms a short tube, usually composed of six segments firmly united together. The lower part of this tube is firmly fixed to the object on which the Balanus has taken up its abode; whilst the superior orifice is closed by a moveable roof, composed of from two to four valves, between which the little tenant of this curious domicile can protrude his delicate cirri in search of nourishment. In their young state the Balanide resemble the following group, the Extomostraca (Fig. 102). Sus-Cxiass II.—Enromostraca, General Characters.—The Extomostraca, in general, present the characters of the class of which they form a part much more distinctly than the Cirrhopoda, although many of them, in their mature or reproductive state, diverge immensely from the typical form of the class. They are generally, especially in their earlier stages, provided with distinctly articulated limbs and antenne, which are usually furnished with bristles, and employed as natatory organs. Orver II.—Parasirta. General Chaxacters.—This order is composed. of numerous small animals, which, in theiryoung state, are furnished with distinct jointed limbs, antennz, and eyes,—organs which either disappear completely, or become greatly modified as the animal approaches maturity, when it attaches iteelf to fishes or other aquatic animals, and passes the 114 PARASITIC CRUSTACEA. remainder of its existence as a parasite. In their mature state, the Parasita often present the most extraordinary forms; and in their appearance and habits they bear so little zesemblance to the other Crustacea, that it was not until the history of their development was investigated, that their intimate connexion with that class of arti- culate animals was ascertained. Until very recently, zoologists considered them to be nearly allied to the Platyelmia, in conjunction with some of which they were formed into a class called Epizoa (Gr. epi upon, zoon animal), from their habits of external parasitism. They are very common on the bodies of fishes, generally attacking the branchia, but not unfrequently attaching themselves to the soft skin under the fins, or to the eyes, to the great inconvenience of their unfortunate victim. Divisions.—These animals form several families, to some of which we shall briefly refer. The; family Lerneide exhibits the greatest amount of degradation in its mature state. The animals composing it consist of a more or less elongated sac-like body (Fig. 106), bearing, at its anterior extremity, a proboscis, through which they suck the juices of their victim, and a pair of modified legs, by which they maintain their position upon its surface. They also frequently possess a pair of foot-jaws, which, however, are no longer connected with the mouth, but serve as additional prehensile organs. The a Fig, 106. Fig. 107. Fig. 108. Fig. 109. Fig. 106.—Female Lernea. a, proboscis; 5, thoracic segment, bearing the legs, c, whi i at their extremities by a sucker, Si d, abdomen ; ¢, ovisacs. 5 8% ¢ which are united Fig. 107.—Young of Lernwa, ‘ Fig. 108.—Caligus. cou eesti Fig. 109.—Under side of Caligus, a, carapace; b, antenne ; c, sucker; de, jaws; fg h, foot- : 4, a forked central appendage ; 3 kim, legs; Ny second segment 3 D, abdomen ; geting f ie proboscis is usually buried in. the substance of the unfortunate host, whose delicate vessels are wounded by:a pair: of pointed organs which it contains. The young of the CYCLOPS. 115 Lerneide (Fig. 107) are exactly like’ those of the next order of Entomostraca, the Copepoda. In the Dichelestide the body is more distinctly annulated, and the anterior segment bears four antennz, of which one pair is slender and thread-like, whilst the others are stout, and furnished with a claw-like extremity, serving as a prehensile organ. In the Caligide (Figs. 108, 109) the structure is much more complicated; the body is divided into two parts, of which the anterior, which is by far the largest, and is covered by an oval carapace, bears two pairs of antenna, a sucker, three pairs of foot-jaws, and four pairs of thoracic legs—three formed for swimming, and one for walking. The abdomen consists of a small lobe at the apex of the second segment, It bears a pair of small fin-like appendages; and from each side of its base springs 4 long tube, which apparently serves as an ovisac. In the Argulide, one species of which, the Argulus foliaceus (Fig. 110), is very common upon various fresh-water fishes, the body is of much the same general form as in the Caligide, and the anterior segment is in like manner covered by a large carapace. The second pair of foot-jaws is here converted into a pair of curious sucking discs (Fig. 110, 2), by which the creature adheres to any object. Between these the jointed rostrum takes its rise. The four pair of thoracic legs are fringed with bristles, and converted into powerful natatory wie. 110,Ar, gulus Foliaceus. organs, by means of which the drgulus swims about with J, the animal magmitied; 2, great rapidity. Unlike the other parasites, it does not eaten {anerlor remain constantly attached to its victim, but only adheres 4, natural length. : to it while actually engaged in sucking. It possesses no ovisacs, and the eggs are deposited upon aquatic plants. Orver III.—Corrropa. These animals present the closest affinity with those of the preceding ordcr, par- ticularly in their earlier stages. They are minute animals, with the body divided into distinct segments, of which the anterior (forming the cephalothorax) bear two pairs of antennze, one or two eyes, the mouth, with its jaws, and two pairs of foot-jaws. The five following segments bear a similar number of pairs of feet, furnished with bristles, Fig. 111.—Larva of the Cyclops. Fig. 112.—Cyelops, and adapted for swimming; and the remainder, constituting the abdomen, form a sort of jointed tail, terminated by a tuft of bristles. They appear to possess no distinct respiratory organs; and the ova are carried in sac-like organs attached to the abdomen of the mother. These animals occur in countless swarms in all waters, whether salt or fresh ; and, minute as they are, one species is said to constitue the principal food of the Antarctic Whale. : 116 OSTRACODA—PHYLLOPODA. The best known form is the genus Cyclops (Fig. 112), specimens of which may be found in every stagnant pool; it is the type of the family Cyclopide, characterised by the possession of asingle eye. In the Cetochilide there are two of these organs. Orver IV.—Ostracopa. General Characters.—In this order, composed of animals generally of very minute size, the body, which strongly resembles that of the Copepoda, is always inclosed in a little bivalve shell, the feet and antenne being protruded between the lower edges of the valves, These little shells so closely resemble those of minute bivalve Mollusca, . : that those of some of the larger Wien Gaels species have actually been described by conchologists as the coverings of animals belonging to that class. The antenne are often curiously branched; and the hinder extremity is usually produced into a sort of tail, which is seen in constant action when the animal is in motion. Divisions.—This order forms two families—the Cypride, in which the body is entirely inclosed within the shell, of which the genus Cypris (Fig. 118) is an example ; and the Daphniade, in which the head is protruded beyond the shell. In the Polyphemus (Fig. 114), belonging to this group, the head, which is large, is almost entirely occupied by an enormous eye, giving the creature a most singular appearance. Fig. 114.—Polyphemus Stag- norum. Orper V.—PHYLLopopa. General Characters.—In this order we meet with animals generally of larger size than those comprised in the preceding groups. They consist of a considerable number of segments, furnished with fuliaceous feet, serving both as natatory and respiratory organs. Sume of them are covered by a carapace or a bivalve shell, whilst others are destitute of this protection. ‘he head is usually quite distinct from the following segment, and bears two large eyes and two pairs of antennw, which are often of very singular forms, The mouth is furnished with jaws. Divisions.—This order is divided into two families. In the first, the Apodide, the body is protected by a ca- rapace, which often takes the form of a bivalve shell. The animals are frequently of con- siderable size; and the number of feet in the typical genus Apus (Fig. 116), is as great as sixty pairs. A singular cir- cumstance, connected with this animal, is that it sometimes makes its appearance in great Fig. 115.—Limnadia. numbers in ponds that have ; been dry for some time, as soon as they are filled up by heavy rains. In the g-nus dpus the carapace is one piece, completely inclosing all the anterior portion of the animal. In the Limnadie (Fig. 115), also belonging to this family, it forms a sort of bivalve shell. Fig.t 16, Apus Montagu. ‘TRILOBITES. 117 The second family includes the naked species, or those which are not provided with a carapace. They are called Branchipodide, from the name of the typical genus, Branchipus (Fig. 117), an animal which is often found after heavy rains in cart ruts and other small pools, Another species, the Artemia salina (Fig. 118) inhabits a still more curious situation, namely, the salt pans SB3ssu6 at Lymington, where it is usually found in those pans in which the evaporation of the water has proceeded to a considerable extent. Fig. 117.—Branchipus Stagnalis. This is also, probably, the proper position for a singular order of fossil Crustacea, the well-known Trilobites (Trilobita), of which vast numbers occur in some of the earlier strata of the earth’s crust. Their general form is well shown in the an- nexed figure of Calymene Blumenbachii; they posses- sed well formed, compound, facetted eyes, which are frequently well preserved in the fossil state. The body is usually divided into three regions, of which the first and last are commonly in Fig. 118.—Artemia Salina, in different the form of semicircular stages of growth. Fig. 119. — Calymene plates, whilst the middle Blumeubuchit. portion exhibits distinct segmentation, and by its flexibility enabled the animal to double itself up in the manner of the common Woodlouse. These animals are now quite extinct, although during the period of the deposition of those ancient strata in which their remains are found, they were almost the only representatives of the class Crustacea. Susprvisron III.—Xypuosura. This subdivision includes only a single order : Orper XyPHosuRa, The order Xyphoswra consists only of a single genus, the Limuli, or King-Crabs (Fig. 120), which, from the locality inhabited by the commonest species, are frequently termed Molucca Crabs, They are amongst the largest of crustaceous animals, sometimes measuring as much as two feet in length. The body of these animals is composed of two divisions—an anterior, crescent-shaped piece (c, Fig. 120), or carapace, inclosing the cephalothorax with its organs; and a posterior, somewhat hexagonal piece, formed by the coalescence of the abdominal segments. From the posterior extremity of this second division of the body projects a long, spine-like tail, which exhibits no trace of segmentation. The upper surface of the body is very convex; the lower surface, on the contrary, is very concave in the middle, forming a hollow, in which the feet are lodged. The upper surface of the carapace is marked by three ridges (see Fig. 120); the middle terminates anteriorly in a small tubercle, on each side of which is a minute simple eye ; but the creature is also turnished with true compound facetted eyes, placed T 113 KING CRABS. one on each side, on the outside of the two lateral ridges. Three sides of the abdominal plate are confined within the posterior margin of the carapace; of the others, two are notched and furnished with moveable plumose spines, and the caudal spine is capable of motion in every direction. The mouth, which is situated near the middle of the lower surface, is completely destitute of true jaws; but the basal joints of the five pairs a Fig. 120.—Limulus. Fig. 121.—Under surface of Limulus. of legs (4, Fig. 121), which are attached close to the buccal aperture, are armed with horny spines, forming very efficient organs of mastication, whilst their extremities, being converted into prehensile claws, are employed in the conveyance of food to the mouth. Immediately in front of the mouth are placed a pair of short jointed antenne (e, Fig. 121), which also bear a small pair of forceps at their extremity. The concavity of the abdominal plate is occupied by six pairs of fin-shaped abdomi- nal feet (ab, Fig. 121), of which five pairs are furnished with branchie, whilst the first pair, which is destitute of those organs, forms a sort of cover for the rest. The anal opening is situated close to the base of the caudal spine. These singular animals, which appear to be most nearly allied to the Phyllopodous ‘Entomostraca—but which also in many points, especially in the structure of their eyes, approach the true Crabs—are found in a very limited area; they occur only on the shores of tropical Asia, the Asiatic Islands, and on the western coasts of tropical America.’ The young closely resemble their parents, except that, at their first escape from the egg, they possess only two pairs of branchial fect, and are quite destitute of a tail. WHALE LOUSE. 119 Sus-crass [Y.—EpRiopHTHALMATA, General Characters—The animals belonging to this sub-class have the head distinct from the thoracic segments, which are also separate, and never amalgamated into a single mass (the so-called cephalothoraz), which occurs s0 generally in the other Crustacea. The head always bears a pair of eyes, which are never pedunculated ; they usually consist of a number of simple eyes crowded together into one spot, although some species possess regular compound eyes. The mouth is furnished with jaws, and with a single pair of foot-jaws; and these are usually followed by seven pairs of legs, to which the branchial organs are attached. Divisions,—The Ldriophihalmata form three orders, characterized principally by the structure of the feet and abdomen. In the first, the Lemodipoda, the abdomen is rudimentary, or in the form of a minute tubercle without appendages; in the Amphi- poda, the abdomen is well developed, and furnished with limbs, but the branchial organs are confined to the thoracic legs; whilst in the Jsopoda the abdominal legs appear to be she organs of respiration. Orprer Lzmopreopa, General Characters.—These animals are at once distinguishable by their rudi- mentary abdomen, which usually forms a very inconspicuous part of their bodies. The head is small, furnished with four antenna, and usually bears the first pair of legs; the mouth is armed with well-developed jaws, and with a pair of foot-jaws bearing long palpi. Of the seven pairs of legs usually present, two are sometimes wanting—their places being taken by small tubercles or vesicles connected with the process of respiration ; this change usually takes place on the third and fourth segments, and similar vesicles also occur on the second and third. The legs of the first and second pairs are terminated by a raptorial grasping organ similar to that of the well- known Mantis, or Praying insect; the others are usually armed with sharp moveable hooks. The ova are received into a sort of pouch, formed of several leaves, which are attached to the footless segments. : Divisions-—This curious little order includes only two families. The Cyamide, or Whale-lice (Fig. 122), which infest the different species of cetaceous Mammalia, form Fig. 122,—Caprella Phasma. Fig. 123.—Whale-Louse (Cyamus Balaenarum.) the first of these. They have a broad body, with a small head, and a pair of large jointed antenne. The other antenne, and the first pair of legs, are very small; but the second pair are of large size, and very powerful. The legs of the third and fourth segments are converted into long tubular branchial vesicles ; but those of the last three segments resemble the second pair in their strength, and in the sharpness of 120 AMPHIPODA. their claws. These animals often infest the whales in such vast numbers that their victim may be recognized at a distance by the whitish tint of his skin. In the second family, the Caprellide, all the proportions of the body are reversed ; instead of being broad and flat, it is long, slender, and nearly cylindrical, and the limbs undergo a corresponding extension in the same direction. The antennw are frequently of considerable length; and the two first pairs of feet exhibit a striking resemblance to those of the Mantis. One genus has all the segments furnished with legs; in another (Fig. 123), the third and fourth bear small vesicular organs in place of limbs. Orpvrer AMPHIPODA. General Characters.—This order also consists of animals mostly of small size, none of them exceeding two inches in length. They usually live free in the water or burrow in sand; a few species are parasitic on fishes. The head is completely separated from the first thoracic segments, and usually bears four antenne, which are sometimes of considerable length. The mouth is furnished with jaws and a pair of foot-jaws, The thorax consists of six or seven segments, each bearing a pair of legs, which are usually furnished with leaf-like branchial appendages, at their bases. In the females of some species the legs also bear peculiar appendages, which serve to keep the eggs under the body. The abdomen is well-developed, and furnished with limbs of various forms, sometimes adapted for swimming, sometimes for leaping—a movement in which some of the Amphipoda display great agility. They always lie upon their sides in swimming. Divisions.—This order also includes two families—the Hyperide and the Gam- maride. The first is characterised principally by the small size of the foot-jaws, which are not furnished with palpi or similar organs. The legs are usually unequal in size; and one or two pairs are often remarkably large, and converted into powerful prehensile organs, The Gammaride are characterised by the large size of the foot-jaws, which cover the whole mouth. The common Tolitrus locusta, or Sand-hopper (Fig. 89}, which may be met with in thousands upon the sands of our shores, is a well-known example of this family, Although its length is not much more than half an inch, it can leap several inchesinto the air, and the facility with which it escapes pursuit by burrowing into the soft wet sand, is truly wonderful. Another species, Gammarus pulex (Fig, 124), is found commonly in fresh water, and is scareely inferior to its marine relative in agility. The Coryphium longicorne (Fig. 124), remarkable for its long antenns, is not less so for its singular habits. It is found at Rochelle, where it burrows in the sand, and Fig. 124. Fig. 125. Fig. 124.—Gammarus Pulex. Fig. 125.—Coryphium Longicorne; a, terminal segment of the tail. wages constant war with all other marine creatures of moderate size that come in its way. To discover their prey, they beat about in the mud with their large antenna, The comparatively gigantic size of many of the Annelida does not protect them from THE ISOPODA. 121 attack ; a suitable number of the little warriors make common cause against the enemy, who soon succumbs to their united efforts. Onper Isoropa. General Characters.—This order includes the greater part of the Edriophthalmata, and the animals composing it exhibit a great variety of form and structure. The body is sometimes of an oval, sometimes of an elongated form, convex above and flat beneath ; the head (Fig. 126 c) is small, distinctly separated from the first thoracic segment, and bears a pair of round eyes, usually formed of a collection of simple eyes, but some- times truly compound. The antennz are often of considerable length, and the jaws arc well-developed. The thorax consists of seven segments (¢!—2?), each of which bears a pair of feet (v—pp); these are usually similar in form, nearly equal in size, and furnished, in the female, with basal plates fur the pro- tection of the eggs. They never bear branchial plates as in the preceding orders, The abdomen (ad) is well- formed, and consists of six segments, which are often, however, more or less amalgamated together. The abdominal legs are furnished with a pair of large oval plates, of which the inner is of a soft consistence, and acts as a branchial organ; the sixth pair, however, usually forms a sort of cover, which can be folded over the others for their protection. In the air-breathing species, of which the common Woodlouse (Fig. 126) is an example, the branchial plates of the hinder abdomi- nal legs are quite rudimentary, whilst those of the Fig. 126.—Woodlouse (Oniscus). anterior ones are well-developed. Into these the air obtains access by small apertures at their base. Divisions.—This order is remarkable, from its presenting, in its lowest forms, animals as thoroughly parasitic in their habits as the Crustacea of the Entomostracous order Parasita ; whilst atthe opposite extremity of the scale, the air-breathing Isopoda appear to make a very close approach to the Myriapoda. M. Milne Edwards has divided the Isopoda into three sections, denominated, from their habits, Cursorial, Nata- torial, and Sedentary Isopods. The latter comprises those species which are fitted for a strictly parasitic existence, being furnished only with clinging feet. We include only a single family in this section, the Bopyride, which live in the branchial cavity of Shrimps. The females of these animals are scarcely more recognizable as Crustaceans than the Cirrhopodous Barnacles or Acorn shells. They are of an irregularly oval form, furnished with fourteen feet, but quite destitute of eyes. The males are about a sixth part of the size of the females, and present very much the form of an elongated Wood- louse ; but the feet are very short, and the abdominal segments are amalgamated into a single plate. The Natatorial Isovoda have the last pair of abdominal feet, terminated by horizon- tal plates, which form, with the extremity of the abdomen, a regular caudal fin. This section includes two families. Of these the Cymothoide (Fig. 127) are parasitic upon fishes, apparently having an especiai predilection for their tails. They have small heads, with short antenne; and the legs are short, and terminated by hooks. In the second family, the Spheromide, the body is usually oval and very convex, sometiaes nearly hemispherical ; the head is large, with four longish antenne, and the feet are slender, 122 THE PODOPHTHALMATA. and fitted only for walking. The five first abdominal segnients are fused together ; but : the last is free and of large size, forming, with the lateral fins, a powerful natatorial organ. These animals all live in the sea, especially on rocky coasts. Like the Woodlice they are able to roll themselves up into a ball. The Cursorial, or walking Isopods, are distinguished from the preceding by the absence of the fin-like expansion of the posterior extremity of the body. The first family, the Idotheide, is dis- tinguished by the development of the posterior abdominal feet into a pair of flat appendages, which can be made to cover the branchi- ferous feet completely. These animals all live in the sea; they are of an elongated form, atid the outer antenna are usually of great length. The second family, the Aseliide, resembles the preceding in many respects, but the appendages of the last abdo- Fig. 127.—Anilocrus. minal segnient are styliform. One species of this family, the Limnoria terebrans, a little creature about the sixth of an inch in length, is exceed- ingly destructive to wood-work immersed in the sea, It bores into timber in every direction, apparently for the purpose of feeding upon it, and has often produced great alarm by its ravages. Some species of this family also live in fresh water. The last family, the Oniscide, including the well-known Oxzscus, or Woodlouse (Fig. 126), and many similar animals, is characterized by the adaptation of its members to a terrestrial existence. The outer antennz alone are visible, the inner pair being usually very minute. The body is generally oval, with the rings very distinct ; and the legs are formed exclusively for walking. Nearly all these Fig- 128.—armadillo ‘ 2 ha 7 pustulatus. animals live on land, in damp places, under stones, dead leaves, and moss; some of them are not uncommon in cellars. When alarmed, they roll themselves up into « ball (Fig. 128), presenting nothing but the smooth, convex surface of their scaly armour to their enemy. Susciass V.—PopoPHTHALMATA. General Characters.—The animals forming this sub-c.ass are distinguished by many peculiarities from those of the preceding sections, and undoubtedly present the characteristics of their class in the greatest perfection. They are easily recognized by the position of the compound eyes at the extremity of a pair of moveable stalks (Fig. 129 y), which are often of considerable length (Fig. 96). The head and thorax are generally amalgamated into a single piece, called the cephalothorax, which bears the antenney, the eyes, the mouth with its jaws (Fig. 94), and the feet (Fig. 129 »); of the latter organs five pairs are usually present, besides one or more pairs of foot-jaws, The remaining segments are generally quite distinct, forming a jointed abdomen, which is fréquently terminated by a fan-like caudal fin (x), The abdominal legs are sometimes organized for swimming; but rarely, as in some members of the pre- ceding sub-class, bear respiratory appendages, the branchie: being usually inclosed within a cavity on each side of the cephalothorax, as already described. Divisions,—The Podophthalmeta, or stalk-eyed Crustacea, may be readily divided into two orders, characterized by the structure of their respiratory apparatus. In the THE STOMAPODA. 123 first, the Stomapodu, the branchie#, when visible, hang freely from the abdomen as pm bY py Jp n Fig. 129.—Prawn. as, antenne of the first pair; ai, antenne of the second pair; 7, laminar appendage covering its base; *, rostrum, or frontal prolongation of the carapace; y, eyes; pm, external foot-jaw ; p*, first thoracic member; p+, second thoracic member ; fp, false legs, or swimming members of the abdomen ; 1, tail-fin. filiform organs, at the base of the abdominal feet; whilst in the second, the Decapoda, they are always inclosed in cavities of the cephalothorax. Onprr Sromapopa. General Characters,— This order is composed of some singular animals, which appear to have relations with all the other groups of Crustacea, and, of course, exhibit a corresponding diversity of structure amongst themselves. The thoracic eegments are sometimes completely covered by the carapace; whilst, in other forms, the carapace only covers one or two seg- ments. The segment bearing the eyes and antenne is always distinct. The mouth is furnished with jaws, and usually with a single pair of foot-jaws; these are followed by seven or eight pairs of true feet, of which the anterior P, Ps b pa pa g a an aber aN pre- Fig. 130.—Squilla. ensile organs, whilstthe pos- y, eyes; a, antenna; i el Py, first pair of le i terior are usually organized legs; ps, three last’ pairs of thotaere: it anee pues a for swimming. The prehen- Pro-legs; 5, gills; g, fin-like members, sile feet are never terminated by nipping claws, like those of the Lobster. The abdominal feet are usually leaf-like organs; they bear, attached to their bases, tufts of branched filaments, which act as 124 THE STOMAPODA. respiratory organs; these, however, are sometimes altogether wanting, and are very rarely attached to the thoracic legs. 3 Divisions.—The Stomapoda form three families. The Phyllosomide are animals of an extraordinarily flattened form, with the shell thin and transparent; the body is apparently divided into two parts,—a longish or oval ccphalothorax, bearing the eyes, which are supported upon long slender stalks, the short antennz, and the mouth; and a second piece, composed of the thoracic segments, which bears seven or eight pairs of long slender feet on its margins. The abdomen is very small. These animals are oceanic in their habits, and are generally found in the southern seas. In the second family, the Sguzllide, the body is elongated, and bears a considerable resemblance to the well-known insect, the Mantis; hence the typical genus Sguilla (Fig. 130) is fre- quently called the ‘Sea Mantis.” Some of them attain the length of a foot or more ; but their average size is about three or four inches. The eyes are mounted on short foot stalks. The antennz are of moderate length, and the outer pair have an oval plate at the base. The carapace is small, and leaves three segments of the thorax uncovered ; these bear three pairs of swimming feet. The mouth is furnished with distinct jaws, and with five pairs of large foot-jaws. The second pair, especially, are of extraordinary size, forming large raptorial organs; whilst the others are furnished with a large vesicular joint, against which the terminal claw can be applied in the same manner as the last joint of the anterior pair. All these feet are so arranged that their extre- mities can be easily brought in contact with the mouth, so as to hold the prey in a convenient position for the action of the jaws. The abdomen is furnished with six pairs of feet, of which the last pair are formed into fin-like organs, which, with the extremity of the powerful abdomen, constitute an excellent natatory organ. The other abdominal feet bear the branchig, which consist of bundles of branched or plumose filamentous organs. The third family, the Myside, forms a distinct step towards the following order ; the animals composing it presenting, in fact, so close a resemblance to the true Shrimps, that by many authors they have been placed with them. In the form of the body they exactly resemble the Shrimps; the thoracic seg- ments being completely inclosed in a carapace, and the abdomen bowed and furnished at its extremity with a caudal fin of five plates. The thoracic feet vary in number. They are usually furnished with long, jointed appendages, which appear like so many addi- tional limbs. The branchie are sometimes attached to the abdominal legs, sometimes to the thoracic legs, and sometimes they are wanting altogether; but they are never inclosed, as in the following order, within Fig. 131.—Mysis Vulgaris, about the carapace. These animals have received the name twice the natural length. of ‘Opossum Shrimps,” from the curious pouch, efor formed of plates attached to the abdominal legs, in which the female protects both her eggs and young, until the latter have attained a considerable development, They occur but sparingly in the European seas, but swarm in profusion in some parts of the world, especially in the Arctic Ocean, where they are said to constitute an important portion of the diet of the whale. THE MACRURA. 125 Orpen DecaPopa, The general characteristics of the animals of this order have been already so fully described, that we need only say here, that it includes all those stalk-cyed Crustacea, in which the whole of the thoracic segments are united with those of the head into a single mass (the cephalothorax), incased in a common shell, with no traces of segmentary division (the carapace), and which have the branchial organs inclosed within a cavity on each side of the cephalothorax. The true thoracic legs are almost always ten in number; whence the name of the order. It includes an immense number of species, generally of considerable size, when compared with the other Crustacea ; and these vary so greatly in their form as to have given rise to the establishment of three distinct sub- orders, characterised principally by the degree of development of the abdominal region. Sus-orper I.—Macrvura, General Characters.—In this order, including the Long-tailed Decapod Crustacea, the abdomen is largely developed, generally longer than the cephalothorax, capable of being extended backwards, and furnished at the extremity with a fan-shaped caudal fin, which is of great service to the animal in the operation of swimming. The first five segments of the abdomen are furnished with laminar or cylindrical legs, to which the ova are attached by a sticky matter after expulsion from the ovaries. The two last segments with broad plates, which, with a similar plate at the extremity of the last segment, form the five-fold tail fin. The antennz—the outer pair especially— are usually of considerable size, sometimes even exceeding the body in length, and the feet are often terminated by a pair of nipping claws, of which those of the anterior pair are sometimes of great size and power. The Macrura undergo but little change in their progress to maturity; the young, on first escaping from the egg, usually presenting a very close resemblance to their parents. Divisions.—The Crangonide, including the well-known Shrimps and Prawns (Fig. 129), form the first family of the Macrura. They are distinguished by the possession of a large oval or triangular appendage (Fig. 129 2), which covers the base of the first joint of the outer antenne. In their general appearance they all present a considerable resemblance to the common Shrimp, which is too well known to need description, They all inhabit salt water, and generally occur in numbers together, on sandy coasts; and in spite of their small size, they are everywhere in great request as articles of food. The second family, the Astacide, to which the common Lobster belongs, is distinguished from the preceding by the small size of the appendage at the base of the outer antenne, besides many other differences in form and structure. The anterior pair of feet is always much larger than the others, and armed with power- ful nippers. Some of these animals live in fresh water. These are of smaller size than the marine species, but are also eaten in great numbers by the inhabitants of the neigh- bourhoods where they occur. The Astacus Juviatilis, or Cray fish, is very com- mon in our rivers; and may be seen for sale, boiled as red as a Lobster, in many inland towns. In the remaining Macrura, the base of the outer antenne is not covered by a move- able plate; but the animals generally exhibit a very close resemblance in form to the Astacide. In the Thalassinide the shell is of a somewhat horny consistence ; the breast is very narrow, and the anterior nipping claws of large size. The last family, including perhaps the largest Crustacea, is that of the Palinuride, of which the Spiny Lobster 126 THE ANOMURA, is an example. These are powerful animals, with very hard shells. The breast is broad, the outer antennz usually very long, and the anterior feet are rarely fur- nished with nippers, and these, when present, are small. All these animals inhabit the sea, where they usually frequent deepish water, not far from the shore. Many of them are used as food in various countries. The Palinurus, or Spiny Lobster, often weighs as much as twelve or fifteen pounds. It was in great esteem amongst the ancient Romans, who denominated it Locusta, Suz-orper I].—Anomoura. General Characters.—The second sub-order of the Decapod Crustacea includes a number of animals which appear to hold an intermediate position between the Long- tailed forms just described and those in which the abdominal segments are least developed—the third sub-order Brachyura. They partake, to a great extent, of the characters of both groups, sometimes approaching one, sometimes the other ; so that it becomes almost equally difficult either to distribute them amongst the Long and Short- tailed forms, or to find characters by which they may be distinguished from the other two groups. They are distinguished from the Macrura principally by the form of the abdomen, which scarcely ever possesses the fan-like fin so characteristic of those animals, and never bears natatory feet ; whilst they differ from the Brachyura in nearly always having appendages attached to the last abdominal segment but one, which are wanting in the latter sub-order. The abdomen is sometimes bent under the body like the tail of a crab, sometimes extended backwards in a line with the body. The inner pair of antennz is generally of moderate size, and the outer pair of considerable length. The three first pairs of feet are always well-formed, and the anterior pair are generally furnished with powerful nippers. The fourth and fifth pairs are generally small, and frequently rudi- mentary. In the latter case they are sometimes attached to the back. The development of the young appears to resemble that of the Brachyura; the newly hatched young, as far as yet observed, being very like that of the common Crab. : Divisions.—In the first family of this sub-order, the eguride, or Hermit Crabs, the abdominal portion is quite soft, forming a sort of cylirdrical fleshy mass behind the shelly cephalothorax. The latter bears well-developed feet, of which the anterior pair is usually converted into formidable nippers. As the comfort of the animal would be materially interfered with were this soft, worm-like appendage constantly exposed to be grabbed at by every passing fish who might take a fancy to it, he usually seeks some shelter for his tail, and the habitation selected is generally the shell of some univalve Mollusk. Into this spiral home the Hermit Crab is coiled, and retains himself in this position by means of a sucker at the extremity of his tail, assisted by two or three rudimentary feet, which are developed upon the abdominal sac; and so firmly does he adhere to his castle, that he will allow himself to be torn to pieces rather than let go his hold. By protruding his body, with its three pairs of legs, from the orifice of the shell, the little Hermit is enabled to walk with ease upon the sandy beach in search of his prey; but the moment danger threatens him, he disappears again into his cell, the orifice of which is then occupied by one of his claws, which is always larger than the other, As the Crab does not possess the same power of adding to the size of the domicile that was enjoyed by the original tenant, he is compelled, from time to time, to hange his residence for one a little larger, and often appears almost as difficult to please as a human householder in the same predicament. Often they may be seen crawling THE ANOMURA. 127 about amongst the empty shells just thrown upon the beach, trying one after another, until they meet with one uniting all the conditions requisite for Crustacean comfort; but, until this great object of their search is attained, always returning to their old house after each unsuccessful trial. It is said, indeed, that when two of them happen simultaneously to cast a longing eye upon some particularly suitable residence, they often engage in a fierce battle for the possession of the coveted object, which the victor carries off in triumph. _ Several species of Hermit Crabs inhabit our shores, and may be frequently found in the pools left by the retiring tide, by any one who will take the trouble to look for them, A curious species belonging to this family, the Birgus Jatro, inhabiting the Isle of France, which protects its soft body in holes in the earth at the roots of trees, is said to feed upon cocoa-nuts, and even to climb up the trees in the night to nip off the fruit. In the Hippide (Fig. 133), the fleshy abdomen disappears, and its place is taken by a jointed tail, furnished with a pair of moveable appendages attached to the last point but one. This tail is sometimes extended behind, but generally bent under Fig. 132.—Remipes Testudinarius, Fig. 183.—Hippa. the breast (Fig. 132), as in the ‘true crabs, and never terminated by a fan-like fin. These animals generally live in the sand, where they bury themselves with great facility by means of their flattened feet. The family Porcellanide includes some small Crabs, which, from their beautifully smooth texture, have received the name of Porcelain Crabs. In their form they resemble the ‘true Crabs, and like these their anterior feet are converted into powerful nippers: but their tails, although bent under their body, are furnished with a small fan-like fin. The outer antenne are very long, and the fifth pair of feet are rudimentary. Like the preceding family they generally live buried in the sand. In the remaining families of the Anomura, the tail is destitute of terminal appendages, and the form gradually approaches that of the true Crabs. In the Raninide, the four hinder pairs of legs are nearly equal in size, and flattened so as to form natatory organs. In the Homotida, the three middle pairs are long and cylindrical, whilst the fifth are much shorter, furnished with a prehensile claw, and placed quite at the back of the animal, or concealed under the carapace; the inner antenna also are of considerable length; and in the Dromiide, which make the nearest approach to the Brachyura the fifth and sometimes the fourth and fifth pairs of legs, are altered in form as in the pre- ceding family ; but the inner antenna are short, and capable of oe concealed in small pits situated at the front of ‘the head, i q £128 THE BRACHYURA. Sus-orper III.—Bracuyvura, General Characters.—In the Brachyura, of which the common edible Crabs may serve as examples, the abdomen is always converted into a short, jointed tail, quite destitute of terminal appendages, and bent round so as to fold closely under the breast (Fig. 184). The cephalothorax is usually of a more or less rounded form, generally broader than long, and often produced in front into a point, The upper sur- face is entirely covered by a single plate (the carapace). The eyes and the inner an- tenn, the latter of which are very short, can be entirely concealed within small cavi- ties of the forehead. The outer antenne are never of any great length, and the anterior feet are always coaverted into nippers. ‘The four other pairs of legs are generally terminated only by single Fig. 134.—Carcinus Meenas (Common amalledible Crab), upper Claws. ‘They are sometimes sive, and under side of the body with the limbs cut short; flattened to assist the animals a, lateral antenna; 5, intermediate antenna; c, eye; d, : : : outer foot-jaw ; e, f, 9, hy é, base of the five pairs of legs; 22 Swimming; but, as a gene- k, tail; /, sternum. ral rule, the feet are formed exclusively for running. This is performed, not forwards, as in most other animals, but with a curious sidelong gait; and the aspect of a Crab, when making his escape from danger, with his claws extended, and every limb in the most rapid though awkward motion, is often very droll. The tail of the female Crab is always much broader than that of the male, and bears four pairs of filiform appendages on the side which is applied to the breast. To these the eggs are attached, so as to be protected by the horny plates of the tail, until the young animals are developed. These, on first coming out of the egg, are active little fellows, with long tails, which, after their first moulting, acquire a singular spine on the middle of the back, whilst a similar spine is developed, at the front of the head (Fig. 99, p. 295). These were described, when first discovered, under the generic name of Zoea. At a later period the eyes become pedunculated, the legs acquire somewhat of their mature form, the nipping claws of the anterior pair are developed, and the spines disappear. In this form the young animals have received the name of Megalops. It is to be observed, however, and this constitutes one of the most singular facts in the history of these animals, that this metamorphosis is by no means universal amongst the Bachyura,—the young of some species, like those of the Macrura, nearly resembling their parents from the moment of their leaving the egg ; whilst those of others, nearly allied to these, undergo a regular series of changes before arriving at their mature form. Divisions.—Professor Milne Edwards divides the Brachyura into four families, The first family, the Ozystomata, have the carapace orbicular, and arched in front ; and the openings for the passage of water to and from the branchial cavities are placed THE BRACHYURA. 129 close together in front of the mouth. The anterior claws are often of very large size, and curiously compressed ; so that they can be applied to the sides of the cephalothorax so closely as to be invisible from above. The other legs vary greatly in their develop- ment, being sometimes long and stout, sometimes short and weak; sometimes formed exclusively for walking, and sometimes more or less flattened to form natatory organs, In the genus Dorippe, the fourth and fifth pairs of legs are reduced in size, placed quite at the back of the animal, and terminated by curious prehensile hooks, In the second, the Oxyrhyncha, Maiade, or Sea-Spiders, the carapace is more or less SEEN Fig. 135.—Spider Crab (Maia). narrowed in front, forming a projecting beak or rostrum (Fig. 135) ; the legs are long and hairy ; the back usually covered with spines and hairs, whence the name of Sea- Spiders, or Spider-Crabs, by which these animals are commonly known. These Crabs generally live in deep water, and rarely ap- proach the shore. Of the third family, the Cyclometopa, or Cancerida, the common edible Crab (Cancer Pagurus, Fig. 136), may serve as an example. In this family the shell is regularly rounded in front, and narrowed behind ; the legs are of moderate length, the claws large, and often unequal in size. The common Crab is too well known to need description. It inhabits deep water, and is captured in large quan- tities, by sinking baskets, pots, or nets, ‘ baited with carrion, in places which it is known to frequent. The small edible Crab (Carcinus Manas, Fig. 134) is also well Fig. 136.—Cancer Pagurus. 130 THE BRACHYURA. Imown, It is to be met with, in profusion, on all our shores. It is less esteemed than the larger spevies, and is principally consumed by the poorer classes. Many other species are eaten in different parts of the world. Some, of which the Long-stalked Crab (Podophthalmus, Fig. 96) is an example, have the posterior pair of feet converted into paddles. In the Catometopa, or Ocypodide, forming the fourth family, the carapace is usually quadrilateral, sometimes oval, with the front generally transverse and knotted. The abdomen of the male does not occupy the whole space between the hind legs. This group is represented in the British seas by the little Pea Crabs (Pinnotheres), which shelter themselves within the shells of many of the bivalve Mollusca, especially the common Mussel. The ancients were acquainted with one species of Pinnotheres, which inhabits the shell of the Pinna, a common Mediterranean Mollusk. They believed that the connexion between the Crab and the Mollusk was one of mutual advantage; and that the former, in return for the protection afforded to him by the shell of his host, not only gave him timely notice of any approaching danger, but also procured him his food. The most remarkable members of this family are the Land Crabs of tropical climates, which are furnished with a peculiar apparatus of leaflets, for re- taining moisture in the interior of their branchial cavities. Many of these ani- mals live upon the sides of mountains, at a great distance from the sea, which, however, they regularly visit once a year, for the purpose of depositing their eggs. They generally select moist lo- calities for their terrestrial residence. Here they excavate considerable bur- Fig. 137.—Land Crab (Gecarcinus). rows, in which they conceal themselves during the day, roaming about at night in search of food. But some, such as the Gecar cint (Fig. 137), are said to inhabit dry woods. The Cardisoma carnifex, which usually inhabits the Mangrove swamps of the West Indian Islands, lives principally upon the fruit of a species of Annona, which. grows in those places, But nothing comes amiss to it. Those individuals whose residence is in the neighbourhood of the cemeteries are said to burrow down to get at the dead bodies; and Dr. Duchassaing tells us, that the West Indian burial grounds are pierced in every direction by the burrows of these animals. Nevertheless the Cardisoma is regarded as a luxurious article of food by the West Indians; who, however, take care only to eat those which live in the Mangrove swamps, as far as possible from the cemeteries. They are caught in box rat-traps, baited with a piece of their favourite fruit; and after their capture they are usually kept some time, and fattened with broken victuals, Another group of Land Crabs, the Gelasimt, axe distinguished by the large size of one of their claws, which they hold up in a menacing attitude as they retreat from any object that has inspired them with alarm. From the beckoning action of this claw, the Gelasimi have received the name of Calling-Crabs. They make great use of it also in forming their burrows, bringing up small pinches of sand or earth every now and then, and scattering these waste mate- rials to a considerable distance round their hole, so as to avoid the presence of an THE ARACHNIDA, 131 unsightly heap at the entrance to its domicile. The Thelphuse (Fig. 4, p. 198) are also Land Crabs, although some of the species inhabit fresh water. Cuass VI.—AnacHnma. General Characters.-—The animals forming the class Arachnida, which includes the Spiders and their allies, are amongst those which are viewed with disgust and aversion by the generality of mankind. Confounded, in the popular mind, with the Reptiles, they of course come in for their share of the bad reputation of those creatures, and some of them, no doubt, not without reason; but on a closer examination we find that, however unattractive they may be in appearance, they present much that is interesting both in their structure and habits. They are distinguished from the other Arthropoda by their aérial respiration, their possession of four pairs of legs attached to the anterior division of the body, and the total absence of antenne. The body is usually covered with a softish skin, which, however, sometimes attains a horny consistency. In the lower forms the division of the body into separate regions is quite unrecognizable, and the whole forms a roundish or oval mass, which does not even present traces of segmentation. In the higher groups the body is composed of two principal divisions, of which the anterior, as in the Crus- tacea, consists of the thoracic segments, amalgamated with those of the head, and forming together a mass called the cephalothorax. In the highest forms the division of the thorax into separate segments becomes apparent; but the anterior segment is still amalgamated with the head. The structure of the abdomen varies greatly. In some cases it forms a soft round mass without any traces of segmentation; whilst in others, as the Scorpions, it is produced into a long flexible jointed tail. Fig. 139, Fig. 138.—Section of the Cephalothorax of a Mygale, showing the arrangement of the nerrow system. ct, cephalothorax; m, mandible ; g, moveable hook which terminates it; 5, mouth; @, esophagus ; é, stomach ; ab, origin of abdomen ; ¢, cephalic ganglion; ¢, ganglionic mass of __ the thorax ; ca, cords which unite it to the abdominal ganglia 3 20, optic nerve ; y, eyes. Fig. 139.—Buccal apparatus of a Spider. , sternum; J, labrum ; ma, maxille; p, maxillary palpi; m, mandibles; g, hook terminating the mandibles. In most of the Arachnida the cephalothorax is armed in front with a pair of powerful jaws, terminated by a distinct claw-like joint (Fig. 189); these are usually per- forated, and convey a poison into the wounds inflicted by them, which, although it rarely produces disagreeable effects upon the human subject, appears to be very speedily 132 THE ARACHNIDA. -fatal-to the small animals upon which.the Spiders prey. These jaws are considered to be the representatives of the antenne of the other Arthropoda. Below them is the opening of the mouth, which is furnished with jaws of a different construction, called maxtlle (Fig. 189), bearing on their outer surface long jointed organs, called palpi, which often attain an enormous development, and are furnished with a pair of pincers at their extremity. In many of the lower forms the mouth is converted into a sucking ‘proboscis. The legs are usually formed of the same parts as those of Insects; a rounded hip- joint (cova) attaches the limb to the sternum; the thigh is united with this by a small moveable joint called the trochanter ; the joint following this is the shin (tibia), at the extremity of which is the foot (tarsus), usually composed of two joints. The nervous system in the higher groups is well developed, consisting of a large nervous mass situated in the lower part of the cephalothorax (Figs. 138 and 140), communicating with a brain, or supra-cesophagral ganglion by a band of nervous matter which embraces the cesophagus; and of one or more ganglia placed in the abdomen and united with the thoracic mass by a pair of filaments. In the Spiders there is usually.only a single et poab po s an . ae Fig. 140.—Anatomy of Mygale. et, cephalothorax opened below, and giving attachment to the limbs, whose first jointe are exhibited; pa, legs of the first pair; p, palpi; m, mandibles; ab, abdomen ; ¢, thoracic nervous mass; a, abdominal ganglia; po, respiratory sacs; 8, stigmata ; i, leaf-like folds in the interior of one of these laid open; ov, ovaria ;. or, orifice of oviducts ; ma, muscles of the abdomen; an, anus; /, spinnerets. ventral ganglion; but the Scorpions have one of these nervous knots in each segment of the abdomen. The eyes are situated on the upper surface of the front of the cephalothorax (Fig. 138); they vary in number from two to eight, and are of the kind called ocelli, or simple eyes. Other organs of sense have not been © recognized. 7 Respiration is effected by means of air-tubes (frachee), or by peculiar modifications of those organs which, in their most perfect form, have received the name of pulmonary sacs. The blood is set in motion by the contraction of a dorsal vessel (Fig. 141), which propels the nutritive fluid from behind forwards, and gives off numerous minute arteries; no veins have been discovered. The intestine is sometimes a simple canal, running in a tolerably straight direction from one extremity of the body to the other; but in most cases the oesophagus leads into a sac-like stomach, furnished with nume- THE PODOSOMATA. 133 rous blind processes, which are sometimes confined to the cavity of the body, but frequently send branches into the legs. The Arachnida are all unisexual, and all lay eggs, with the exception of the Scorpions and a few Mites, in which the ova are retained within the oviducts until they are hatched, so that the animals produce living young. In the majority of the Arachnida, the young, on escaping from the egg, present the same general form that they are to retain through life; but amongst the lower forms, such as the Mites, the young are often comparatively imperfect, some- times possessing fewer legs than the perfect animal, and sometimes having the same number of those organs, but in a less developed condition. Divisions.—The Arachnida may be divided into two large groups or subclasses, in accordance with differences in the structure of their respiratory apparatus. In one of these sections the animals (when respiratory organs have Fig. 141.—Heart of a Spider. been detected) breathe by means of air-tubes, or trachew, coe ae and the eyes are never more than four in number; these _ proceeding from its ante- form the subclass Zrachearia, In the second section the fisry vein’) Pulmo- respiratory organs take the form of pulmonary sacs, and the animals are hence called Pulmonaria; they possess six or eight eyes. The first of these subclasses includes three orders—the Podosomata, which appear to possess no special breathing apparatus, and which are distinguished from all other Arachnida by their marine habitation ; the Acarina, or Monomerosomata, in which the body is usually composed entirely of a single mass; and the Adelarthrosomata, which have the abdomen more or less distinctly annulated. Supciass I. — TracwEart. Orvrr J.—Poposomara. This order is composed of a few singular spider-like creatures, which have been shifted about by different authors, backwards and forwards, between the Crustacea and the Arachnida. They are all marine; some of them, like the Nymphon (Fig. 142), being found amongst stones and sea-weeds on the beach, or amongst rocks and corals in deep water; whilst others, such as the Pyenogonum (Fig. 143), attach them- selves parasitically to Fishes and other marine animals ; Fig. 143.—Pyenogonum Fig. 142. —Nymphon Grossipes, and under side of its beak. the species figured Balenarum. lives upon whales. The body is composed of four segments, amalgamated into a regular cephalothorax, and 134 THE ACARINA. each segment bears a pair of long jointed legs. In front of this mass is a short rostrum, which is sometimes accompanied by a pair of palpiform jaws; and between these and the first pair of feet, the females of some species possess a pair of false feet (Fig. 142), to which the eggs are attached. The stomach gives off long processes, which sometimes run almost to the extremity of the legs; but no circulatory or respiratory organs have yet been recognized. The nervous system is very imperfectly developed. The young, on first leaving the egg, possess only four short legs, furnished with long filaments; their metamorphosis has not been observed. These animals form two families: the Pyenogonide, which are parasitic in their habits, and have the palpi obsolete; and the Nymphonide, which craw] about slowly amongst the stones and weeds of their aquatic home, and are furnished with distinct palpi. Orper IT.—Acarina, on MonoMERosomAtTA, General Characters.—Nearly all the animals that we include in this order—of which the common Mites are the best known examples—are recognisable at the first glance by the form of the body, which usually constitutes a roundish or oval mass, without any trace of segmentation. They are mostly parasitic animals, furnished with a proboscis containing a pair of sharp spines, which serve for wounding their prey, and bearing a palpus on each side. The intestine is always furnished with lateral processes, which are often recognisable externally by their effect upon the colour of the animal. The proboscis is jointed and retractile. Sometimes it is furnished with a swollen base, which has been taken for a head. The eyes, which are often wanting in the parasitic forms, are two in number when present, and are placed on each side of the anterior portion of the body. The respiratory organs consist of trachesw or air tubes, similar to those of insects; these arise from a pair of lateral openings, and ramify through the body. Their structure will be described when we come to treat of the insects, in which the trachez are presented in their most characteristic form. The Acarina are generally oviparous animals; but a few bear living young. The young generally possess only three pairs of feet; the fourth pair not making their appearance until after the first moult. Divisions.—We must refer very briefly to the numerous families into which this order is divided. The three first of these groups, like the earlier families of the Crus- tacea, are composed of animals in which the characters even of the class are almost entirely lost by degradation ; and although their general structure appears to indicate this as their proper position, they have been placed in very different situations Fig. 144.—Linguatula Temoides. by some zoologists. The first of these, the Linguatulida, containing - the Linguatule (Fig. 144), curious worm-like animals, found in the frontal sinuses and lungs of various Mammalia, and in the lungs of some Reptiles, has generally been placed amongst the intestinal worms; but recent investigations have shown that the - young of these creatures greatly resemble the dcari in the form of their body, and that they are furnished, whilst still in the egg, with four short, jointed legs. The creature resembles a jointed worm, with no traces of external organs, except two pairs of hooks THE ACARINA. 135 placed close to the mouth, which serve to maintain the animal in its position. The second family, the Simoneide, also includes parasitic animals; but these select a more singular habitation than the Linguatule. They are minute, soft creatures, furnished with four pairs of legs, which frequently take up their abode in the follicles of the human skin; they are vulgarly denominated “ maggots in the skin.” In the structure of the mouth these creatures agree with the Mites ; their bodies, when young, are much elongated, but gradually shorten as they approach maturity. They never exhibit any appearance of segmentation. The species found on man, Simonea folli- eulorum, usually confines its attacks to the face, and appears to be particularly partial to the nose. The third of these doubtful Acarine families, is that of the Macrobiotide—microscopic animals which have usually been associated with the Infusoria, and especially with the Rotifera, They are known as Sloth or Bear-ani- malcules, and they are to be found in moss or in fresh water. Their bodies are usually of an elongated oval form, furnished with four pairs of legs, of which the hinder are placed at the extremity of the body. The mouth is furnished with a short rostrum, armed with a pair of sharp, moveable spines. The feet generally bear four claws. No trace of a circulatory or respiratory apparatus has been found in these creatures; and in one genus only do any indications of annulation present themselves. The most singular fact, connected with these curious little creatures, is their power, although inhabitants of water or moist situations, of retaining their vitality for an indefinite period of perfect drought and returning to life the moment Fig. 145.—Maerobiotus Rufel- andi, seen from the back. a, armature of mouth; b, eye; & slomaely ; @, ovary ; e, hind feet. they are again moistened. The most fruitful locality in which to search for them is Fig. 146. Fig. 147. Fig. 146.—Acarus domesticus, or Cheese-Mite, magnified. Fig. 147.—Sarcoptes Scabiei, or Acarus of the Jtch. one in which we should scarcely suspect the exist- ence of anything animated —namely, amongst the sandy dust that collects in the gut- ters on the roofs of houses. Here, however, they may generally be met with, not unfrequently associated with other animalcules, in which, as we have already seen, the same resuscitation also takes place. Of the family of True Mites (Acaride) some are active in their habits, like the common Cheese Mite (Fig. 146); others are parasitic upon or beneath the skins of man 4 136 THE ADELARTHROSOMATA. and other animals, Of the latter, one species is well-known by its effects; this is the Sarcoptes Scabiei (Fig. 147), which produces the disgusting complaint so common amongst dirty people, known as the itch. The Izodide, forming another family, are furnished with a powerful rostrum, armed with recurved spines (Fig. 148), with which they pierce the skin of the unfortunate animals upon whose blood they live. So firmly does this anchor- like organ retain its hold, that if the parasite be pulled away it usually carries a portion of the skin of its victim with it. These creatures live upon a great variety of animals. The dog is very liable to their attacks, and many species attach themselves exclusively to S serpents and other reptiles. The animal known as the Harvest 4 \ Bug, which is often so troublesome in summer and autumn, also (Vy belongs to this group. The Gamaside, which are furnished with | a sucking apparatus very similar to that of the Izodide, usually 2 attach themselves to the bodies of beetles ; and the common Dung- ee aiene al beetles (Geotrupes) may often be found with the lower surface its Rostrum. nearly covered with them. In the preceding families—most of which are parasitic in their habits—the eyes are usually wanting. The remainder, which generally lead a more active life, are always furnished with these organs. One family, the Hydrachnida, or Water-mites, inhabit the water, where they - swim about with considerable rapidity by means of their fringed legs (Fig. 149). In their young state, they attach themselves parasitically to aquatic insects; they then possess only six legs, and pass through a quiescent or pupa state before acquiring the fourth pair. The Oribatide —which, unlike the other Acarina, live upon vegetable matter, principally the leaves of mosses —are covered with a hard and very brittle skin, and have the mouth adapted for biting. The Fig. 149.—a, Hydrachna Globulus ; 6, Baellide, which live amongst damp moss, have ™*#nified; ¢ young larva; d, pupa. the body divided apparently into two parts by a constriction, and the rostrum and palpi very ong; whilst the Trombidiide, of which the little Scarlet Mite so often seen in gardens is an example, have the palpi converted into little raptorial organs. Orver ITI.—ApELARTHROSOMATA. General Characters,—The animals composing this order have the abdomen united to the cephalothorax by its whole breadth, and the body sometimes presents a regular oval outline, as in the Mites; but the abdomen, on close examination, is always found to be more or less distinctly annulated. The mouth is armed with jaws like those of the Spiders; and the palpi are generally of great length, and converted into nipping claws (chelicera), like those of the Scorpion, to which some of these crea- tures bear no very distant resemblance. Like the Mites, they respire by means of trachew, which open by two or four openings on the lower surface of the body. HARVEST SPIDERS, 137 Divisions.—These animals form three families. In the first, the Phalangide, of which the Harvest-men, or Harvest Spiders (Fig. 150) of our gardens and fields are well-known examples, the division of the abdomen into segments is. often indistinct; the antennal jaws are large and furnished with a didactyle claw; the palpi are of moderate length, and the legs in general immoderately long. Propped upon these stilt-like limbs, the Pha- langia stalk about amongst plants in search of insect prey, and they seem to be very voracious animals, Some exotic forms belonging to this family are remarkable for the extraordinary shape of their abdomens, which project into Fig. 150.—Harvest Spider (Phalangium). angles and spines of all imaginable forms. The Cheliferide, forming the second family, are at once distinguishable by the form of their palpi, which are very long, and terminated by strong . nippers, like those of the Scorpion. These animals, in fact, -\. resemble little Scorpions that have lost their tails (Fig. 151). Like the preceding, they are predaceous in their habits, and often get into houses in search of food. They are frequently found amongst old books, which they visit, no doubt, in pursuit of the minute insects sometimes to be met with in such situations. They occasionally attack the common House-fly, and run quickly in every direction, Fig. 151.—Chelifer. backwards, forwards, and. sideways, like little crabs. Their appearance, with their little claws extended, is very curious. The last family, the Sofpugide, includes several spider-like animals, some of which enjoy a most unenviable reputation. The antennal jaws and palpi are of very large size; the latter being longer than s the three anterior pairs of legs. They live principally in the sandy deserts of the old world, where the common species (Ga- leodes araneoides, Fig. 152), which attains the length of about two inches, is said to be Fig. 152.—Galeodes. a great torment to the camels. They run with great swiftness, and are very voracious, sometimes even attacking small birds and lizards. When threatened, they retreat with their head and formidable nippers raised in an attitude of defiance; and their bite is said, by the natives of the regions they inhabit, to be extremely venomous. Suzn-crass I].—Puitmonaria, The pulmonary sacs, the presence of which is the leading characteristic of these animals, are to be regarded merely as modifications of the tracheary structure presented by the other Arachnida. Like the trachex, they open by stigmata, or small apertures in the lower surface of the animal; but these, instead of leading into a tuft of little tubes radiating amongst the organs of the body, admit the air into a small closed sac, con- 138 THE SCORPION. taining a packet of minute plates, laid side by side like the leaves of a book (Fig. 140). These animals possess six or more eyes, placed on the anterior portion of the cephalo- thorax (Fig. 153), They are always ocelli or simple eyes, each fur- 0° nished with its own separate nervous filament. °o000 The Pulmonaria form two orders—the Polymerosomata or Pedipalpi, in which the abdomen is distinctly annulated and attached to the Fig. 158.— Eyes cephalothorax by its whole breadth; and the Dimerosomata, or true of Spider. Siders, in which that region of the body presents no signs of segmen- tation, and is connected with the preceding segment by a narrow peduncle. Orver IV.—PepreauPi on PoLYMEROSOMATA, General Characters.—The principal distinctions existing between these animals and the true Spiders, which constitute the following order, are the great development of the palpi, which always form large arm-like prehensile organs, often terminated by a pair of nippers, and the distinctiy annulated structure of the abdomen. The skin is always hard and horny; and the abdomen is attached to the back of the cephalothorax by its entire breadth. Divisions.—This order includes only two families, and the species in these are not particularly numerous; but few of the Arachnida are more renowned than these, from the universal dread inspired by the venomous powers of their best known representatives, the Scorpions. These form the family Scor- pionide, characterized by their elongated tail-like abdomen (Fig. 154), armed at its extre- mity with a sort of hooked claw, which, when the crea- tures are in motion, is always carried over the back in a most threatening attitude. This claw-like organ is the sting, of the formidable nature of which such extraordinary accounts are given by the natives of those tropical regions to which, fortunately for Europeans, the largest and most dangerous species are confined. The poison glands are situated close to the base of this organ, and their ducts run to its point, so that when the creature strikes with its weapon, a small portion of the venom is instilled into the wound. Whether this venom is ever fatal to human life, appears still to be a matter of dispute ; but the effects of the Scorpion’s sting are, doubtless, very disagreeable ; it often produces great and painful swelling of the part wounded, accompanied in many cases with vomiting and other symptoms. Moreover, the venom of some species is said to be rapidly fatal to man; and an African genus has received its name (Androctonus, manslayer) from its evil reputation in this respect. As to the effects of this poison upon smaller animals there can be no doubt; as the Scorpions destroy: their prey, which consists principally of insects, by holding them in their claws, and stinging them to death. Some of the larger species also capture small lizards and other animals, which they destroy in the same manner. The Scorpions have four pairs of stigmata and pulmonary sacs placed upon the first Fig. 154.— Scorpion. SPIDERS, 139 four segments of the abdomen. Behind the last pair of legs, a pair of curious comb-like organs is placed, the office of which is not known; but the aperture of the generative organs is situated between them. The female Scorpion exhibits the greatest care for her young, carrying them upon her back for some days after they are hatched, and attending to them closely for about a month, after which they are able to take care of themselves. They generally live on the ground under stones and in dark places, coming out at night in search of prey; but they frequently find their way into the interior of houses, where they are sometimes so numerous, that in some places it is said that scarcely an article of furniture can be moved without the greatest danger of being stung by some concealed Scorpion, irritated at this unexpected intrusion on his privacy. The animals forming the second family, the Thelyphonida, present an appearance in some degree intermediate between the Scorpions and the true Spiders. The abdomen is short and rounded, but distinctly annulated; the cephalo- thorax forms a single mass; the palpi are very long and stout; but, instead of the pincers of the Scorpion, they are terminated by a moveable claw, capable of being applied to the inside of the preceding joint, and thus forming a prehen- sile organ. The structure of the anterior pair of feet is very remarkable; they are much thinner than the other three pairs, and the tarsi are formed of a great number of joints; so that the limbs are converted into long flexible organs of touch, f which probably fulfil the office of antennz. Many of them Fig. 155.—Phrynus_reni- are large animals, of a somewhat forbidding appearance, formis (reduced). which, like the Scorpions, can run in every direction. They are almost confined to tropical countries, inhabiting principally the hottest parts of Asia and America. OrpEer V.—DImMERosomATa. General Characters.—The general appearance of the animals forming this order must be familiar to all our readers. The body consists of two distinct portions, of which the anterior, or cephalothorax, is usually of an oval form, and covered with a plate of a somewhat horny consistence; whilst the posterior (the abdomen) generally forms a soft, roundish mass, without any traces of segmentation, and which is attached to the base of the cephalothorax by a narrow peduncle. On its anterior portion the cephalothorax bears six or eight simple eyes (Figs. 138 and 153), which are usually situated on a slight eminence. Below and in front of these are seen the large mandibles (Figs. 138, 189), which serve the Spiders for the destruction of their prey, below which is the opening of the mouth, furnished with a pair of masti- cating jaws, or maxille. From each of these springs a long, jointed palpus (Fig. 139), which in some instances appears to be converted into a supplementary leg. These organs occupy the front of the cephalothorax. Its lower surface bears four pairs of jointed legs, furnished at their extremities with claws, which are often of a very singular, comb-like structure. : The pulmonary sacs, which are contained in the abdomen (Fig. 140), are either two or four in number, opening by stigmata in the lower surface of the abdomen, Besides these respiratory organs the majority exhibit an aperture at the extremity of the abdo- men, from which four flat trachem arise, and ramify through the organs of the body. But the most remarkable organs, perceptible on the abdomen of spiders, are the spinnerets (Fig. 140 f), by means of which these animals spin their curious and often 140 WEBS OF SPIDERS. beautiful webs, which have attracted the attention and excited the admiration of man- kind ‘in all ages. These spinnerets are little teat-like organs, placed close to the extremity of the abdomen, on its lower surface. They are sometimes four, sometimes six in number; and may usually be recognised by the naked eye. Each of them bears at its-apex a multitude of minute tubes, of which as many as a thousand are present in some species ; so that the delicate thread, by which these creatures suspend themselves in the air, must frequently be composed of at least four thousand slender filaments. The substance of which the threads are composed is secreted by glandular organs, situated in the abdomen, close to the base of the spinnerets. It is a viscid fluid, which speedily hardens on exposure to the air. The spider usually commences its thread by applying the spinnerets to some fixed object; to this the glutinous secretion attaches itself, when the movements of the creature are sufficient to draw out the materials necessary for the continuation of the thread. The hind feet are always applied to the thread at a short distance from the spinnerets, probably in order to bring the numerous filaments into contact before their hardening has proceeded too far to allow of their adhesion. This power of spinning threads is of the greatest importance to all these animals, as it not only serves many of them for the construction of dwellings, and of nets for the capture of prey, but appears to be constantly employed in securing them from falls whilst in motion, or in descending in a direct line from an elevated position to some object below them. Many of them have the faculty of emitting threads, one end of which floats freely in the air, until it meets with some object to which it adheres. By this means spiders often form natural bridges, by which they can pass over brooks and ditches. Some species avail themselves of the same power to take long flights in the air, where they often attain great altitudes. Those spiders, whose instinct prompts them to employ their spinning powers in regular weaving operations, manifest this in various ways. Some—of which the common garden Spider (Epeira diadema, Fig. 156) is an excellent example—construct a beautiful net, composed of stout radiating lines, intersected at tolerably regular intervals by circular filaments. It appears that the latter are beset by an immense number of viscid globules, which doubtless assist greatly in entangling any insect that is so unfortunate as to come in contact with the web of the destroyer. The mode ir which the creature forms this elegant structure—its readiness to rush out of its concealment the moment some hapless fly has become entangled in its meshes—the rapidity with which it shrouds its victim in a silken coat—and the care with which it repairs any damage done to its net—are all so exceedingly interesting, that we regret that our space will not permit us to dwell at length upon these points. The nets of some of the large tropical Spiders are said to be of strength sufficient even to capture small birds. Other species—such as the common House- spider (Aranea [Tegenaria] domestica, Fig. 158)—weave a close cloth-like web, usually placed in obscure corners; this is furnished with a sort of funnel-shaped cell, within which the Spider lies in wait for his prey. Others again employ their silk merely to line the holes and crevices which form their ordinary places of abode; and some of these exhibit great ingenuity in the construction of their nests. Another purpose, to which this secretion is applied by all Spiders, is the formation of little silky cases, or cocoons, for the reception of the eggs, which a few species carry about with them. Attempts have been made to employ this silk, which differs considerably in its texture from that of which the nets are constructed, for industrial purposes ; but hitherto with very little success. The Spiders are all predaceous animals, and generally of an exceedingly fierce and THE HOUSE SPIDER. 141 sanguinary disposition, They prey with avidity upon insects and other articulated animals of smaller size than themselves; but, unless in self-defence, they do not appear to turn their weapons against the higher animals. Nevertheless, the gigantic species of Mygale, which inhabit tropical countries, have received the name of Bird- spiders, from a belief that they frequently attack and devour small birds; and Madame Merian, in her book on the Insects of Surinam, has given us a most striking representation Fig. 156.—Epeira diadema. Fig. 157,—Theridion Malmignatta. of a Mygale in the act of devouring a small bird, which he has, to use the lady’s own expression, “ torn from its nest.” It is to be feared, however, that in this in- stance, as in some others, that enthusiastic natural- ist was misled by Indian tales; for, fromallthatwe “shyy know of the Spiders of the genus Mygale, they are strictly terrestrial in their habits, and generally seek their food upon the sur- face of the ground. Divisions.—We di- vide the Spiders into three families, distinguished at once by differences in their structure and ha- bits. Those of the first family,the Araneide, have the eyes in two rows, one behind the other, the ter- minal claw of the man- dibles directed inwards, Fig. 158.—Aranea (Tegenaria) domestica. and the palpi, although often long, never converted into foot-like organs. They 142 DIVING AND HUNTING SPIDERS, usually possess six spinnerets and only a single pair of pulmonary sacs. All these Spiders spin themselves a dwelling-place, which is also generally connected with a net for the capture of prey. Perhaps the best known of these is the Epeira diadema (Fig. 156), whose threads often force themselves upon our attention in a very disagreeable manner. This species forms one of the most beautiful of what are called geometrical webs; many of the others form a somewhat similar structure, although without. dis- playing the same wonderful regularity. Of these the Malmignatte (Theridion Malmig- natta, Fig. 157), a Spider much dreaded in the south of Europe, is an example. Our common House Spider (Aranea domestica, Fig. 158) is another well-known species, offending the eyes of the housewife as it constantly does by weaving its dusky web in all dark corners. One of the most remarkable members of this family is the Argyroneta aquatica, or Diving Spider (Fig. 159), which weavesitself acuriouslittle bell-shaped dwelling at the bottom of the water, to which it retires to devour its prey. As, not~- withstanding its aquatic habits, this animal, like the rest of its order, is fitted only for aérial respiration, it takes care to fill its miniature dome with air, which it carries down with it from the surface amongst the hairs with which its body is thickly clothed; a process very closely resembling that by which the earliest diving-bells were supplied with air. The second family, the Lycoside, agrees in the structure of its jaws and palpi, and in the number of its spinnerets, with the Araneide, but the eyes are arranged in three rows. Unlike the Araneide, the animals of this family never construct regular webs for the capture of prey; their utmost exertion of instinct, in this direction, consisting in laying a few threads in the neighbourhood of their dwelling-place. They generally live under stones, in holes in the earth, or in old walls, sometimes lining their habita- tions with a silken tapestry ; and some, which live upon trees, weave themselves a silken nest amongst the leaves or on the branches, They all take their prey by force ; some of them running it down by swiftness of foot, whilst others spring suddenly upon their unwary victim. Perhaps the most celebrated of these Spiders is the Tarantula (Lycosa tarantula) of southern Europe, whose bite is supposed by the natives of Italy to cause death, unless the patient be relieved by music and violent dancing. Some of these Spiders can run in any direction, A common example is the Salticus scenicus, a small species banded with black and white, which may frequently be met with on garden walls. Most of the European species are small; but in hot climates they attain a size scarcely inferior to those giants of the order which form the third family, the Mygalide In these (Fig. 90) the palpi are of great length, terminated by a claw. The last joint also has a regular sole, like that of the feet. The mandibles are of very large size, and their terminal. claw is directed downwards (Fig. 138) ; the pulmonary sacs are four in number (Fig. 140) ; and the abdomen bears four spinnerets at the apex. Some of these Spiders attain such a large size that their extended legs occupy a circle of six or seven inches in diameter; and it is to these that the practice of bird-catching already alluded to has been ascribed. Species occur on the shores of the Mediterranean ; but Fig. 159.—Diving Spider (Argyroneta aquatica). THE MYRIAPODA. 143 they are, for the most part, confined to tropical countries, They resemble the Lycoside in their habits, generally living on the ground, in holes, or under stones. Some of them form long twisted burrows for themselves, which they line with silk; and these burrrows sometimes extend as much as two feet below the surface of the ground. Some, like the Ctenize, close the mouth of their subterranean residence with a most ingeniously- constructed trap-door (Fig. 160), which the in- habitant closes with the utmost pertinacity when any attempt is made to invade the privacy of his domicile. Hence the Ctenize—of which several species are found in the south of Europe, and on the shores of the Mediterranean—are generally known as Trap-door Spiders. The bite of the large tropical species is said to be very dangerous. Fig. 160.—Nest of Cteniza. Crass VII.—Myrtiapopa. General Characters.—The small class of Myriapoda, of which « characteristic example has already been figured (Fig. 3), is in its general characters very clusely allied to the insects, although in some respects it appears to approach the Crustacea, especially the air-breathing Isopods (Oniscide), In the mature state their bodies are generally elongated, and composed of numerous segments, of which only the first and last exhibit any difference in structure from the rest; the articulations of the body being generally exactly similar, and bearing each one or two pairs of jointed legs. ‘The head always bears a pair of jointed antennz, very similar to those of many insects; and behind the insertion of these, on each side, is a variable number of simple eyes, which, however, are sometimes wanting. The mouth, in its general structure, bears a considerable resemblance to that of the masticating insects, being furnished with jaws, palpi, and an upper and lower lip. Besides these organs, it is armed below with a pair of powerful hooked jaws, which are perforated at their extremity apparently for the emission of a venomous fluid. These are the principal agents in seizing prey. The succeeding rings, which admit of no division into thorax and abdomen, are each furnished with one or two legs on each side; and close to the insertion of the feet, the stigmata, through which the air passes into the tracher, are situated. It is remarkable that, in those species which possess two pair of feet on each ring, each ring also bears a pair of stigmata; whilst in those which have the rings furnished with only a single pair of members the stigmata occur on alternate rings. Hence Latreille, and after him several naturalists, have considered that in the latter case the rings are only half segments, two of which go to form the equivalent of the segment of the double- footed forms. The trachew ramify through the organs of the body in exactly the same manner as those of insects. In their internal anatomy they also exhibit a great resemblance to the insects. Their nervous system consists of a series of ganglia running along the ventral portion of the body, and usually united by a double thread; and the circulation is effected by a long cylindrical dorsal vessel, the structure of which will be explained under the following class. The Myriapoda are all unisexual animals. The orifices of the generative apparatus are frequently situated at the anterior portion of the body. In some Myriapoda the 144 CENTIPEDES, young, on first escaping from the egg, possess nearly all the characters of their parents, although the number of segments and limbs is always less, and increases at each change of skin; but some, as the Zui, undergo a sort of metamorphosis (Fig. 161), coming from the egg either quite desti- tute of feet, or furnished with only three pairs of these organs; and it is not until after several moultings that they attain the same number of legs Fig. 161.—Transformations of Iulus. u,b,c,suc- as their parents. This process appears cessive stages. to occupy a considerable period; and, according to the observations of Pro- fessor Savi, the Juli occupy two years in their development before the sexual organs make their appearance. This metamorphosis, such as it is, indicates the close alliance of these creatures with the insects; and many authors either include them in the class Insecta, or, retaining them in a separate class, associate with them some of the apterous insects which present the closest resemblance with them in their earlier stages. Divisions.—The Myriapoda form two orders—the Chilopoda and the Chilognatha, which may be readily distinguished by the structure of the antennz ; those of the former never being composed of less than fourteen joints, whilst those of the second order always consist of seven articulations. OrpzeR J.—Cuinoropa. General Characters.—These animals are usually of a flattened form, with the rings protected both above and below by a more or less flattened horny plate, and each ring bears only a single pair of feet, those of the hinder ring being directed backwards in the form of a pair of jointed tails. The antenne are long and always composed of at least fourteen joints. The structure of the mouth has already been described. These creatures usually live in the earth or under stones. They run with consi- derable swiftness in pursuit of their prey, and can even progress backwards by the assistance of their tail-like hind legs, which at other times are dragged helplessly behind them. Their food consists of insects, which they seize with the powerful jaw- like organs attached to the lower lip; and these organs are supposed to inject a poison into the wound they inflict. The bite of some of the large tropical species is said to be exceedingly painful, and even more injurious than that of the Scorpion ; although the application of ammonia to the wound speedily relieves the pain of the bite. Divisions.—The Chilopoda are divided into three families—the Cermatiide, the Scolopendride, and the Geophilide. The Cermatiide have the body rather short, with its upper surface covered by eight plates, its ventral surface by fifteen; the legs are very long, and terminated by feet composed of numerous joints. These animals are all exotic, and generally of small size, They conceal themselves amongst the beams and joists of houses. The Scolopendride, well known. as Centipedes (see Fig. 3), have the body long and divided into an equal number of segments on both surfaces, with the legs rather short, but stout and well adapted for active motion. This family includes all the most powerful and predacious species, those of hot climates certainly attaining a length of twelve inches; and, if we are to believe some travellers, still more gigantic species are to be met with in particularly favourable situations. Thus Ulloa states that specimens MILLEPEDES. 145 2. have been seen in Carthagena exceeding three feet in length and five inches in breadth, the bite of which is said to be mortal; but these dimensions are so far above those of any Centipedes that have ever been brought to Europe, that we may be pardoned for receiving them with some little incredu- lity. Our British species, of which one of the commonest, the Lithobius forci- patus, is here represented (Fig. 162), -are of comparatively small size, rarely exceeding. two inches in length; but even these, when seized, will turnand ——~“ : ; attempt to fix their jaws into the skin Fig. 162.—a, eee foreipatus s 6, Geophilus of their captor. The Geophilide, of which a common British species is figured above (Fig. 162), are distinguished by their very elongated and almost thread-like bodies, composed of numerous segments, and bearing a great but variable number of feet. Some species are phosphorescent in the dark. One of these, the Geophilus electricus, is not unfre- quently met with in the neighbourhood of London, Orver II.—Cuioenaraa. General Characters.—In the Chilognatha the body is generally of a convex form, composed of numerous horny arches, below which an immense multitude of little feet may be seen, whence the name of Millepedes, or thousand-legs, by which these animals are commonly known, is derived. Each segment of the body bears two pairs of limbs, with the exception of the hindmost segment, which is destitute of those organs. The antenne are short, and composed only of seven joints; and the powerful biting jaws of the Chéilopoda are reduced to a rudimentary condition,—the other organs of the mouth also undergoing considerable modifications. As might be expected from this difference in the structure of the mouth, the food of these animals differs greatly from that of the predaceous members of the preceding order; and the Chilognatha are found to feed principally upon vegetable matters, generally when in a state of decay. In accordance with this change of habit, the movements of the creatures, notwith- standing their immense number of legs, are always very slow, and they generally endeavour to escape danger by rolling themselves up into a ball (Fig. 165). They are to be met with constantly in damp moss, and a few live under the bark of trees. Divisions.—The first of the four families into which the Chilognatha are divided contains only a single minute, but very curious, creature, which is often found in great abundance under the bark of old trees. It is about a sixth of an inch in length, com- posed of eight segments, exclusive of the head and tail. On each side of the body there are nine tufts of little curved hairs; and the extremity of the body is furnished with a tuft of longer straight hairs. This animal is the Polywenus lagurus ; it forms the type of the family Polyxenide. : ‘ In the second family, the Poly- desmida, the form of the body ap- proaches that of the Scolopendride in the preceding order, being flattened . " and rather soft; but in other respects Hig: 168.-—Folydeemus: the animals resemble the Iulide. One species, the Polydesmus complanatus (Fig, 163), is an inhabitant of Britain. 146 INSECTS. In the Julide (Iudus, Fig. 164), the body is elongated, and nearly of a cylindrical form, bearing no inconsidera- bleresemblance toathick worm, in which the skin has become horny and di- vided into nu- merous segments. These animals are constantly to be found in damp moss, and sometimes crawling upon trunks of trees. When alarmed they coil themselves up in a spiral form (Fig. 165), with the feet entirely con- cealed, Their march is very slow, and, from the shortness of their Fig. 165.—Iulus, with the body 1¢88% appears more like a gliding coiled up, and the front of the motion than a walk. oe theantenn® = The Glomeride, forming the fourth Fig. 166.—Glomeris family, have a short oval body, marguiata. closely resembling that of the Woodlouse, which they also resemble in their habit of rolling themselves into a perfect ball when in danger. The body is convex above and concave beneath, where it is furnished with a row of small scales on each side. These animals live under stones. Fig. 164.—Iulus. Cuass VIII.—Insrcta. General Characters.—We come now to the last and highest class of articulated animals, including the innumerable host of trueinsects—creatures which, in whatever light we view them, always present many points of the highest interest to our observation. Whether we consider the history of their curious transformations, their extraordinary and often beautiful forms and colours, their wonderful instincts, and the close approach to reason exhibited by some of them, their effects upon our persons and property, or the extraordinary means by which nature avails herself of the instincts of some species to put a check upon the ravages of others—we always meet with much to command our admiring attention; sufficient, in fact, to render the study of insects one of the most attractive pages of the book of Nature. Entomology has this additional recommendation, that it is one of those branches of Zoology that may be pursued in any situation. Insects abound everywhere ; and wherever they occur their habits may be observed, and their structure investigated. We regret, therefore, that our limits forbid us from giving more than a very bare outline of their history. Insects, in their perfect state, are distinguished from the other articulate animals by the possession of six legs and two antenne, and by the division of the body into three distinct regions, the head, thorax, and abdomen (see Fig. 167), of which the second bears the organs of motion. They respire by trachew, are generally furnished with wings, and almost always undergo a series of transformations (the metamorphosis) before arriving at their mature and reproductive form. Like the other Arthropoda, the bodies of insects are composed of distinct rings or segments, and these are generally of a horny consistency, united to each other by a STRUCTURE OF INSECTS—EYES, 147 membranous skin which gives flexibility to the whole, In some cases, however, the skin is of a softer texture; but even in these it presents sufficient firmness for the attachment of the muscles, and the tubes composing the limbs are generally of a harder Antenne _ Head. Ist pair of Lega ““""--"—-~~" = resatansecetseniensts Scent 1G b lst pair of Wings Thorax, 2nd pair of Legs e xX 2nd pair of Wings 8rd pair of Legs Abdomen, Targus + --~--.--—--.A (i Fig. 167.—Anatomy of the external Skeleton of an Insect. consistence than the rest of the integument, The number of segments of which the body of an insect is normally composed is thirteen ; but some of them are occasionally amalgamated together, or concealed by the others, so as to make it appear that fewer segments are present. The first segment, or the head, is composed of a single piece, which bears the eyes the antennm, and the organs of the mouth. The eyes (Fig. 168), which are amongst the most wonderful objects in na- ture, are almost always of the kind called compound; that is to say, they consist of a multi- tude of little hexagonal facets, brought close together on each side of the head, each furnished with a cornea, a lens, a coating of pigment, and a nervous fila- Fig. 168.—Head and Eyes of the Bee. ment, The number of these @a, antenne ; 6, ocelli; A, facets enlarged; B, the same * ‘s 4 with hairs growing between them. little eyes is sometimes most extraordinary, The eye of the common ‘House-fly has 4,000 of them; that of a K ‘148 ANTENNZ AND MOUTH OF INSECTS. ‘Dragon-fly more than 12,000; of a Butterfly observed by Puget, 17,325; and that of a small species of Beetle (Mordella) no less than 25,000. In addition to these compound eyes, many insects also possess two or three ocelli, or simple eyes (Fig. 168), placed on the head between the large compound organs ; these appear to be very similar in their structure to the individual eyes of which the compound eyes are composed. The antenne are usually attached to the front of the head, between the eyes. They are exceedingly variable in their form, and probably vary considerably in function, although their general office appears to be that of organs of touch. In some instances, however, their conformation appears to indicate that they are the organs of some special sense ; and the functions of smell and hearing have been attributed to them by different observers. In their most ordinary and simple form, they are more or less filiform Fig. 169.—Antenne of various Insects, organs, composed of a very variable number of joints. Sometimes they are thickened at the base; sometimes at the apex. In some cases the whole or part of the joints are furnished with one or more processes, bristles, or hairs, giving the entire organ a comb- like or feathered appearance; in others the terminal joints are converted into broad plates, folded together like the leaves of a book. These, and several other forms, are represented in the annexed figure (Fig. 169); and we shall meet with a still greater variety as we proceed. : The structure of the mouth in insects exhibits very remark- able modifications; and these are of the utmost importance in the classification of these creatures. In some insects the mouth is formed exclusively for biting ; in others, as exclusively for suction; whilst in others is j Bens again it is fitted for the per- | formance of both these actions; Fig. 170.—Head of Cockroach. 5nd the form of its constituent a a, labrum; 6, mandibles; ¢, maxille; d, maxillary palpi; parts of course undergoes cor- Fig. 171.—Parts of the Mouth vbr e, tongue; jae palpi ; g, responding changes,—but the of Carabus. antenns ; 2, compound eyes; «ot 3 labrum ; 4, mandibles ; #, ocelli. ” same organs really exist in all, % maxille ; 4, labiuma,” - modified in appearance, indeed, so as sometimes to be scarcely recognizable. . MOUTHS OF INSECTS. 149 In the masticating or biting insects, the mouth (Figs. 170, 171), consists of six separate organs; an upper lip (/abrum, a) attached to the lower part of the front of the head ; a pair of horny, curved, biting jaws (mandibles, 6), which are usually armed with teeth; a pair of chewing jaws (mazilla, c), generally composed of four pieces, and bearing either one or two pairs of jointed palpi; and a lower lip (Zabiwm, d), which closes the mouth from beneath, and also bears a-single pair of palpi (Fig. 170, ¢). Onits inner surface it is furnished with a membranous or fleshy organ, to which'the name of the tongue has been given. Amongst the Bees the organs of the mouth take another form, which, whilst it leaves a portion of them fitted for biting, converts the remainder into genuine suctorial .-. Lateral Lobes ot the Tongue Fig. 172.—Head of Anthophora. Fig. 173,—Parts of the Mouth separated. organs (Figs. 172, 173). The parts thus modified are the maxille and labium; the former (Fig. 173, c) become greatly elongated, forming a sort of jointed sheath which incloses the elongated tongue (Fig. 173 @), constituting a tubular organ piles which the fluid nourishment of these crea- tures can be sucked up. The mandibles and labrum (Fig. 173, a, 6) retain their ordinary form, and the former are constantly em- ployed in the numerous ingenious operations which these industrious creatures perform. The suctorial mouth presents three principal forms. In the But- terflies and their allies, the sucto- rial organ consists of a long trunk, which, when at rest, is coiled up Fig, 174.—Mouth of Sphinx. * * H, head; e, eye; a, antenne; mz, maxilla; mp, maxil- im i spiral form beneath the head lary ‘palpi; i, \abrum; u, labium ; ly, labial palpi ; (Fig. 174). This spiral trunk is m, mandibles. composed of the terminal portion of the maxilla, which are more or less elongated, and 150 MOUTHS OF INSECTS. form two long wrinkled tubes, adhering together along their inner surfaces, and forming a double tubular organ, through which their possessor sucks the juices of flowers. The maxillary palpi are generally of very small size, and only to be detected by dissection ; but the labium, although very small, usually bears a pair of very large, hairy palpi, which form the cushions between which the trunk is coiled up when at rest. The mandibles and labrum are also present, although in a very rudimentary condition, and always concealed under the hairs with which the heads of Butterflies are clothed. This structure of the mouth, which is characteristic of the order Lepidoptera, will be easily understood by reference to the annexed figures (Fig. 174), in which the organs are represented separate. , In another form of suctorial mouth, which is characteristic of the order RAynchota, including the Bugs and their allies, the mouth is furnished with a jointed rostrum, formed by the coalescence of the labial palpi (Fig. 175 a); this is in fact a tube, split down the front, and inclosing four bristle- like organs (Fig. 175 4c), which are in reality only the modified mandibles and maxille. By means of these bristles, which ere sharp at the point, the Rhynchota wound the tissues of the animals or plants upon the juices of which they feed. The labrum is generally rather elongated, and serves to close the basal joint of the rostrum. Whenin the tube, the bristles are pressed very close together, and two of them generally e ae he adhere in such a manner as to lead to the Fig. 175.—Buccal ree of an Hemipterous appearance of their number being only three ; (6); they are inserted into the head by broad bases (c), to which muscles are attached; and by the action of these they are exserted and retracted. A third form of suctorial apparatus is presented by the Diptera, or two-winged flies, of which the common House Fly is a familiar example. These possess a proboscis (Fig. 176), generally of a fleshy texture; this is composed of the lower lip, is usually bent up- wards at a short distance from its base, and terminated by a broad flap (the representative of the labial palpi), which is constantly used as an organ of touch. The upper sur- ; : ‘ face of this proboscis, which forms a ° °Y*Ss % ovelli; are mine ip) saaille; #9, Tae tube, is opened below the knee-like ol bend, to give issue to the true buccal organs, the mandibles, maxille, and labrum, which in many of these animals acquire the form of bristles or lancets, and are employed in piercing the skins of other animals and sucking their biood. The maxille are generally furnished with a pair of palpi, consisting of from one to five joints; and when, as is Fig. 176.—Proboscis of a Dipterous Insect (Tabanus). LIMBS OF INSECTS. 151 sometimes the case, the maxille, with the other internal organs, are reduced to a rudi- mentary condition, the maxillary palpi are inserted upon the stalk of the labium at or near the bend. All these types of structure undergo great modifications in different groups of insects; and these differences furnish some of the most important characters for the classification of these animals, The second division of the body of insects is always composed of three segments, although these are frequently amalgamated together in such a manner as to be almost undistinguishable, The three segments together form the thorax (see Fig. 167); but they are individually distinguished by names indicative of their position in the body, the first being called the prothoraz, the second the mesothorax, and the third the metathorax. They vary greatly in their comparative size, and in the amount of their surface visible on the upper part of the body. In some insects all the segments are equally uncovered, whilst in others only the prothorax is visible when the wings are closed; and every intermediate form may be met with. The thoracic segments always bear the organs of motion, which, in most insects, consist of six legs and four wings. The form of these organs is very various; but their general construction is always similar. The centre of the lower surface of the thorax, or breast, is occupied by a narrow piece called the sternum, which frequently projects as a ridge externally, and generally gives off an internal process for the insertion of muscles. On each side of this are the sockets for the legs, of which each segment of the thorax bears a pair. The first joint of the legs, called the coxa (or hip), is sometimes immoveably attached to the thorax, sometimes articulated with it by a sort of ball and socket joint. This is followed by a second piece, the ¢rochanter, which unites the long thigh (femur) to the coxa; this varies greatly in its form, being some- — times ring-shaped, sometimes forming a triangular piece applied against the base of the thigh. The thighs are generally of a rounded form, frequently thickened in the middle or towards the extremity ; they are often, especially the hinder pair, of very large size, and armed with spines of greater or less magnitude. The shanks (or tibie),. which are articulated by a sort of hinge-joint to the extremities of the thighs, are generally about equal to these in length, but thinner, and frequently more or less flat- tened or angular, and furnished with numerous spines or bristles. At the extremity of the tibia comes the tarsus, or foot, which sometimes consists of one, but generally of from three to five joints. The lower surface of these feet is generally flattened and converted into a sort of sole, covered with very close set hair; and the apex of the last joint is almost always fur- nished .with a pair of claws, often beautifully toothed, and in many cases accompanied by a pair of soft mem- branous organs, called pulvilli, which are very distinct in the common fiy. These adhere, like sucking-cups, to any object against which they may be ap- plied, and thus enable their possessors to walk securely even in a reversed position. The legs and their component parts undergo an infinity of modifications in the different groups of insects; always, however, in exact coincidence with the habits of the creatures,—in leaping insects, such as the Grasshopper and the Locust (Fig. 177), the hinder legs are much lengthened and the Fig. 177.—Locust. 152 LIMBS OF INSECTS—WINGS. thighs very thick, forming powerful jumping organs. In many aquatic species (Dyticus and Notonecta) the legs are flattened and fringed with hairs to enable these animals to swim rapidly through the water. In the Mole Cricket (Fig. 178), the fore- Fig. 178.—Mole Cricket (Gryllotalpa). legs become modified to suit the creature to its burrowing habits; whilst in the Mantis, or praying insect (Fig. 179), these limbs are converted into most formidable prehensile organs, with which these insects, reputed so pious by the inhabitants of the countries where they are found, most remorselessly mangle the bodies of their insect prey. Many other modifications of these organs occur; and as these modifications are of great Fig. 179.—Mantis religiosa. importance in the classification of insects, we frequently in the sequel. The wings, of which there are never more = : vo Fig. 180.—Callichroma Moschata. the folding wings of many insects is effected. shall have occasion to refer to them than two pairs, are attached to the second and third thoracic segments. They are generally of a membranous texture; but, notwithstanding the delicacy which they often exhibit, each wing is found to consist of a double membrane, between which a variable number of veins, or ners vures, ramify in different directions. These serve to keep the wings ex- tended; and the characters afforded by their arrangement are often of the greatest importance. These nervures appear to be horny tubes, accompanied by vessels; and it is probably by the injection of fluid into the latter that the extension of WINGS OF INSECTS. 153 In some insects the four wings are all of a similar texture, and alike available in flight ; whilst in others, the anterior pair acquire a firmer consistence, forming a sort of case, within which the large membranous posterior wings can be folded up in repose. In the Beetles (Fig. 180), the anterior wings generally acquire a horny consistency, and constitute a regular hard shell, covering the back of the abdomen and the wings when the insect is at rest: these are called elytra. In the Grasshoppers and Locusts, and some other insects, on the contrary, the anterior wings, although much stronger than the posterior, are still flexible, and possess only a parchment-like texture, in which the neryures may be distinctly recognized ; whilst in the Bugs, the basal portion of the elytron, is generally horny, and the apical portion membranous. The wings are generally more or less clothed with minute hairs; these, in the Butterflies and allied insects, usually acquire the form of flattened scales, to which, as is well known, the beautiful colours of those insects are due. Although the wings of insects are generally four in number, the hinder pair is very frequently absent; and, in fact, one whole order of insects is characterized by the possession of only one pair of wings. In these (Fig. 181) a pair of small knobbed filaments, which stand on the sides of the thorax behind the wings, and which are called hadderes or balancers, have been regarded as the representatives of the hind wings. Of the abdomen in general but little can be said. It consists normally of nine seg- ments; but some of these are generally con- cealed by the others, so that the abdomen appears to be composed of a smaller number of articulations. In some instances the segments are attached edge to edge, when the abdomen exhibits little or no flexibility ; in other cases, each segment slides at its base within the one preceding it, so that the whole is capable of bending to a certain distance in some directions. The orifice of the generative organs is situated at the extremity of the abdomen, which, in the male, is often furnished with peculiar organs for grasping the abdomen of the female during copulation, and in the female with instruments of very various structure, adapted for placing the eggs in the situation most proper for their development. These exquisitely beautiful contrivances will be described hereafter under the ‘different groups of which they are characteristic. The apex of the abdomen is also sometimes furnished with appendages not connected with the generative organs ; these are sometimes long filiform tails, sometimes bristle-like organs, by means of which the insect effects considerable leaps. In the Cockroaches, and some other insects, they form stout-jointed bristles, resembling short antennz. In the Earwigs they constitute a powerful pair of forceps, often of great length ; whilst the aphides are furnished with a pair of tubular appendages from which a sweet juice exudes, The intestinal canal always forms a tube of variable width (Fig. 182), formed of three membranous layers, running from one extremity of the body to the other, com- mencing behind the mouth in a narrow esophagus, and usually terminating posteriorly in a somewhat dilated cavity, the cloaca, which also receives the termination of the internal generative organs. The cesophagus leads first into a membranous, and usually Fig. 181.—Conops. 154 DIGESTIVE CANAL OF INSECTS. folded stomach, the crop; from this, in the masticating insects, the food passes into a second stomach, which, from its being furnished with horny plates and other organs for the comminution of the food, has received the name of gizzard. Behind this is the CRE eS 2 a Fig. 182.—Digestive Apparatus of Beetle. harynx ; b, esophagus; ¢, crop; @, giz- ota ae chylifie stomach ; t small intes- tine; g, rectum; h, biliary vessels. true stomach, in which the process of chylification goes on. This is often covered with little villi, or furnished with glandular organs, which appear to secrete a gastric juice of some kind. The remainder of the canal forms the intestine, which is usually of a tubular form, and is very variable in length, sometimes running to the anal opening with but little deviation ; whilst in other cases it forms several convolutions in the anterior of the abdomen. The length of the intestinal canal varies greatly. In the carnivorous and suctorial species it is usually short—not more than twice the length of the body—whilst in the vegetable-feeding insects it is much longer, sometimes attaining a length equal to eight times that of the body. The oesophagus is usually furnished with tubular salivary glands, and in the suc- torial insects also frequently with a bladder-like organ, the sucking stomach, by the dilatation of which the animals are enabled to suck up their fluid nutri- ment. Behind the stomach the intestine receives the mouths of several long tubu- lar organs, which are usually considered to secrete a matter analogous to bile; whilst the anus is frequently furnished with similar glands, producing an acrid and often offensive secretion. As insects possess no system of absor- bent vessels like those of the higher animals, the portion of the food to be assimilated passes through the walls of the stomach into the cavity of the body, when it mixes with the blood bathing the surface of the organs, and thus comes into the general circulation. The circulation is effected by very simple means, The heart is a tubular organ running along the back of the insect, and hence called the dorsal vessel—(a in the diagram Fig. 183). This is formed of a series of sacs opening one into the other, from behind forwards, in such a manner that the folds formed by the junction of the sacs serve as valves to prevent the reflux of the blood. The blood enters this vessel from the cavity of the body by a series of valvular openings, when it is gradually driven forwards by the successive contraction CIRCULATION AND RESPIRATION OF INSECTS. 155 of the divisions of the vessel, until it escapes in the neighbourhood of the head. It appears, however, that after this it is no longer confined within vessels, as neither Fig. 183.—Circulation in Insects. (The arrows indicate the course of the blood). atreries nor veins have been detected in the bodies of insects, but that it gradually passes back through the spaces left between the internal organs, until it again reaches the heart. During this return it comes in contact with the respiratory organs, which, in this class of animals, consist of an infinity of minute tubes, which ramify in every direction through the body. These are composed of a mem- branous outer coat, which is kept constantly distended by a minute cartilaginous filament coiled up in a spiral form (Fig. 184), The air penetrates into them by a number of openings, called stigmata or spiracles, placed on each side of the body. There is usually one pair to each segment, with the exception of the head, and terminal segments of the abdomen. The spiracles are furnished with a muscular appa- ratus, by which the insect can close the aperture at pleasure. They © ; are frequently situated on the membrane uniting contiguous seg- aie nee ments. The most general form of the nervous system in insects is that already described and figured at page 199, Fig. 5, although many of these animals exhibit a striking departure from this general rule. In some the whole of the ganglia of the body appear to be condensed into one or two masses, from the hindmost of which the abdominal nerves radiate in all directions, whilst others present various intermediate stages between this and the normal form. The brain consists of a nervous mass, placed above the cesophagus; and from this the nerves of the principal organs of sense, the eyes and antennae, are given off. Below the esophagus is another ganglion, united with the supra-cesophagral ganglia by a pair of nervous threads, which form a collar surrounding the esophagus. From the lower portion of this ring the filaments are given off which unite the ganglia of the body with those of the head; and these filaments, with their ganglia, always run along the lower portion of the body immediately within the skin 156 TRANSFORMATIONS OF INSECTS. of the belly; the alimentary canal occupying the space above them, and this again being surmounted by the dorsal vessel. Of the organs of sense in these animals we have already spoken. Their marvellous instincts will be described hereafter. Insects are all unisexual animals. Hermaphrodism, where it occurs, is quite exceptional in its nature, and very rarely gives rise to individuals capable of propa- gation. The different sexes are sometimes undistinguishable by external characters, except that the females are usually larger and broader than the males; but in most instances the structure of the apex of the abdomen at once indicates the sex, and, inde- pendently of characters derived from this part of the body, other organs, especially the antennz and tarsi, often present very great differences in the two sexes. Their repro- duction is also essentially oviparous, although some species are ovo-viviparous—that is to say, the eggs are hatched and the young developed to a greater or less extent within the body of the parent ; and a few (the Aphides) are truly viviparous at certain periods, the young being produced apparently by a sort of internal gemmation. In their regular development from the egg, insects in general pass through a certain series of changes, which together constitute what is called the metamorphosis, the young animal on emerging from the egg generally exhibiting an ap- pearance very different from that which it is ultimately destined to assume. The degree of this me- tamorphosis is, however, very different in different groups of insects. In its most complete form, as exemplified in the Butterflies (Fig. 185), Moths, Beetles, and many other insects, the meta- morphosis takes place in three very distinct stages. In the first, which is called the larva state, the insect has the form of a grub, sometimes furnished with feet, sometimes destitute of those organs. Different forms of insects in this state are popularly known as caterpillars, grubs, and mag- gots. During this period of its existence the whole business of the insect is eating, which it ' usually does most voraciously, ; ; . changing its skin repeatedly to det) apo er nara ree J ureta nae allow for the rapid increase in its bulk; and after remaining in this form for a certain time, which varies greatly in different species, it passes to the second period of its existence, in which it is denominated a pupa. In this condition the insect is perfectly quiescent, neither eating nor moving. It is sometimes completely inclosed in a horny case, in which the position of the limbs of the future insect is indicated by ridges and prominences, sometimes covered with a case of a softer TRANSFORMATIONS OF INSECTS. 157 consistence, which fits closely round the limbs, as well as the body, thus leaving | the former a certain amount of freedom. Pup of this description are sometimes inclosed within the dried larva skin, which then forms a horny case for the protection of its tender and helpless inmate. After lying in this manner, with scarcely a sign of life for a longer or shorter period, the insect, arrived at maturity, bursts from its prison in the full enjoyment of all its faculties. It is then said to be in the émago or perfect state. This metamorphosis is one of the most remarkable phenomena in the history of insects, and was long regarded as perhaps the most marvellous thing in nature; although recent researches have shown that the history of many of the lower animals presents us with circumstances equally if not still more wonderful. Nevertheless the meta- morphosis of the higher insects is 4 phenomenon which cannot fail to arrest our attention. To see the same animal appearing first as a soft worm-like creature, crawling slowly along, and devouring everything that comes in its way, and then, after an inter- mediate period of death-like repose, emerging from its quiescent state, furnished with wings, adorned with brilliant colours, and confined in its choice of food to the most delicate fluids of the vegetable kingdom, is a spectacle that must be regarded with the highest interest ; especially when we remember that these dissimilar creatures are all composed of the same elements, and that the principal organs of the adult animal were in a manner shadowed out in all its previous stages. But although the majority of the class Insecta undergo a complete metamorphosis of this description, there are many in which the only transformation consists in a series of changes of skin, without any interval of rest; the larva, which from the first presents a certain degree of resemblance to its parent, gradually acquiring those organs which it originally wanted. In this metamorphosis, which is called incomplete, the principal difference between the larva and the imago consists in the absence of wings (Fig. 186), which first make their appearancein the foom =A of thick lobes, inclosed in cases, SITY Aas in the course of the last changes Ces . of the skin. The joints of the antenne and tarsi are also seme- times fewer in number; and the ocelli, or simple eyes, are gene- ally: cg Mie tov tis, when Fig. 186.—Transformations of the Great Green Grasshopper present in the perfect insect. In (Gryllus Viridissimus). a, Larva; 6, Pupa; x, wing- some insects, such asthe Dragon- _—‘obes;_ ©, Imago. flies, the May-flies (Fig. 187), and some others, the larve, which are aquatic, present a greater difference from the perfect insect than in the cases above referred to ; although the pupa is active and continues to feed until the time of its arrival at the imago state. We may therefore call this a sub-complete metamorphosis. Lastly, a few insects, which possess no wings in the perfect state, undergo no change, except in size, from the time of their emergence from the egg, to that of their reaching maturity. 158 CLASSIFICATION OF INSECTS, Divisions.—In accordance with these peculiarities of the metamorphosis, the class of insects may be divided into three sub-classes. In one, the animals are apterous in all stages, and undergo no change of form; these are called Insecta Ametabola. In a second, the larve present a more or less close re- semblance to the perfect insects, but possess no wings, which make their appearance in the form of lobes or tubercles on the back of the pupa. The latter is Fig. 187.—May-fly (Ephemera vulgata) : Larva, Pupa, and generally active, and continues Imago. to eat, but in some cases is quiescent; these are the Insecta Hemimetabola. In the third sub-class the metamorphosis is complete; the larva, pupa, and imago states constituting three distinct phases of life ; the second being always quiescent. These are the Insecta Metabola. Some entomologists, amongst whom we may mention Professor Burmeister, of Halle, deny the existence of the first of these groups, distributing the insects which form it amongst the orders of the second sub-class; whilst Mr. Westwood arranges the Ametabola with the Myriapoda in a class distinct from the Ptilota, or winged insects; but we have not considered ourselves justified in adopting either of these views. These sub-classes are further divided into orders principally from characters derived from the structure of the mouth and wings. Of these the Ametabola include three,— the Anoplura, or Lice, possessing a suctorial mouth ; the Mallophaga, or Bird-lice, with biting oral organs, but without caudal appendages; and the Thysanura, or Spring-tails, with mandibulate mouths, and with two or more bristles attached to the caudal extre- mity. The Hemimetabola include three principal orders, of which one, the Rhynchota, including the Bugs and Cicadz, is characterised by the possession of a jointed suctorial rostrum, whilst the other two are mandibulate, In one of these, the Orthoptera, the wings are unequal; the posterior membranous pair being the largest, and folded up in repose beneath the anterior pair, which are generally coriaceous in their texture. A second, the Neuroptera, has the wings generally equal in size and similar in consistence. Some of these have quiescent pupe. A fourth small order, the Phy- sopoda, consisting of minute insects nearly allied to the Orthoptera, is characterised by the possession of four narrow flat wings, without nervures, but furnished with a fringe of fine hairs. The third sub-class, the Metabola, is divided into six orders, of which three have the mouth completely suctorial; whilst in the others some of the oral organs are always formed for biting. Ot the suctorial Metabola, the Aphaniptera (a little order including only the Fleas) have the thoracic segments distinctly separated, and the wings represented only by two horny plates on each side of the body. In the two other suctorial orders the segments of the thorax are more or less com- pletely fused into a mass. Of these, the Diptera, or Flies, are distinguished by their short proboscis, and by the possession of only a single pair of wings; the position of the hinder pair being occupied by kmobbed filiform organs; whilst the Lepi- COMMON LICE. 159 doptera, including the well- known Butterflies and Moths, are furnished with spiral trunk, and with four large scaly wings (Fig. 185). Of the mandibulate orders of this section, the Hymenoptera are characterized by their four more or less membranous veined wings, of which the posterior pair are always the smallest; whilst the Coleoptera, or Beetles, are distinguished by the horny consistency of their anterior wings, which serve merely as cases for the protection of the delicate mem- branous hinder pair. A third mandibulate order, the curious Strepsiptera, or Bee- parasites, apparently allied to the Coleoptera, have the anterior wings reduced to a rudimentary condition, forming a pair of singularly twisted appendages placed on the mesothorax; whilst the hinder wings are of large size, and fold up like a fan during repose. The females are apterous. Sus-crass J.—AMETABOLA. Orpen I.—Anoriura. Neither the habits nor the appearance of the insects forming the present order are such as to render them particularly attractive objects. Small as they are, perhaps no other insects inspire so much disgust as Lice ; being generally regarded as the con- comitants of dirty habits. They have a flattened and semi-transparent body, with a distinctly separated head, which bears a pair of short five-jointed antenne and one or two simple eyes on each side, and is furnished beneath with a soft retractile pro- boscis, within which are four bristle-like organs, the analogues of the mandibles and maxille. There is rarely any distinction between the thoracic and abdominal Fig. 188.—a, the Common Louse; 5, magni- segments, except that the former are a ee Tepe apnea Sn See furnished with three pairs of stout legs, terminated either by a strong hook or by a pair of clasping claws (Fig. 188). These animals are all parasitic upon mammiferous animals, of which almost every species has its peculiar louse, whilst some of them harbour three or four distinct species of these parasites. Four species inhabit the human subject, three of them being of ordinary occurrence, whilst the fourth, the Pediculus tabescentium, has only been occasionally observed, but always in vast numbers, either causing or accompanying a complaint under which the patient appears gradually to waste away. Several instances are recorded in ancient authors of death being caused by this disease, which is termed phthiriasis (from the Greek phtheir, a louse) ; and although, in some of these cases, the mischief appears rather to be attributable to mites, allied to the Sarcoptes scabiei (page 319, Fig. 147), yet the occurrence of vast quantities of Pediculi upon an old woman, which was observed some years since at Bonn, would seem to show that true Lice may have been the aggressors in some of the fatal cases on record. These insects generally infest those parts of their hosts which are most thickly covered with hair, amongst which they creep about with ease by means of their grasping claws. They attach their eggs, which are of a pear shape, to the hairs, and 160 BIRD LICE—SPRING-TAILS. the young are excluded in a few days. They undergo no metamorphosis, and are soon capable of reproduction; so that their numbers rapidly increase, when proper measures for their eradication are neglected. Burmeister arranges the Anoplura with the Rhynchota. Orper II.—MALioPHaca. General Characters.—This small order is composed of insects bearing a general resemblance to the Lice, with which, in fact, they are arranged by many authors; whilst Burmeister, whose system admits no orders of apterous insects, places them with the Orthoptera in his order Gymnognatha, They differ from the Anoplura, in having the mouth always formed for biting, being furnished with a pair of hooked mandibles, and distinct upper and lower lips, and sometimes with a slender pair of palpigerous maxille. This difference in structure is accompanied by a corresponding difference in habits. Instead of sucking the blood of the animals on which they are parasitic, the Malophaga devour the most delicate portions of their hair or feathers; frequently attacking these organs at the moment of their sprouting through the skin. They are especially common upon birds, few of them being free from such parasites; and some species also infest quadrupeds. As nearly every species of bird has at least one of these parasites peculiar to itself, their numbers, as might be expected, are by no means small, and they have been formed into numerous genera. Burmeister divides them into two families—the Philopteride, with filiform antennz, and without maxillary palpi, and the Liotheide, with maxillary palpi and clavate antenne. _ Orpen III.—Tuysanvra, General Characters.—This order includes a small number of ' mandibulate insects, referred by Burmeister, like those of the preceding order, to the neighbourhood of the Orthoptera. They are distinguished from the other Ametabola by the possession of caudal appendages, by means of which most of them are enabled to execute consi- derable springs. The body is clothed with hairs or scales. The head is sometimes free, sometimes concealed beneath the prothoracic segment. The eyes, in some species, are compound; but the majority are only furnished with a group of simple eyes on each side of the head; and the mouth is composed of an upper and lower lip, a pair of man- dibles, and a pair of maxille ; the lower lip and maxille being usually furnished with palpi. Divisions.—They form two families—the Poduride, or Spring-tails, and the Lepismide. In the former the caudal appendage has the form of a forked tail (Podura, Fig. 189), which is bent under the animal when not in use, and by its sudden extension causes the animal to spring, often to a great distance in comparison with its size. The head is distinct; the antenne short, and generally four-jointed ; the simple eyes six or eight on each side; and the palpi very short, and composed only of a single joint. The body is covered with numerous minute scales, often of a beautiful silvery or pearly lustre, and curiously striated, which are frequently employed as test objects for the microscope. The insects usually live in moist places, under leaves, in considerable numbers. Some species may be found jumping about on the surface of the water, whilst others are met with in profusion upon snow and ice. Fig. 189.—Podura. THE RYNCHOTA. 161 The Lepismide (Machilis, Fig. 190), have a spindle-shaped body, usually covered with silvery scales, and furnished along the sides of the abdomen : with a series of appendages or false feet, besides several long, jointed, bristle-like organs at its extremity. The head is concealed under the prothorax: the eyes are usually com- pound, and frequently occupy the whole of the head; the antennes are very long, and composed of numerous joints; and the maxillary palpi, which consist of from five’ to seven joints, are very conspicuous. These insects generally inhabit moist places under stones» in woods, and similar localities. The most common species, Lepisma Saccharina, is frequently found about houses, espe- cially in sash frames, They are very active, and many of them jump well; but they generally conceal themselves during the day, and seek their food, which appears to consist of vegetable matter, by night. Svus-crass I].—Hemmetapona, The majority of the insects of this sub-class are active in all stages of their existence; and, as a general rule, the prin- cipal differences between the larva at its exclusion from the egg, and the perfect insect, consist in its smaller size, and in the absence of wings. In the last order of this section, the Neuroptera, the difference between the larva and the perfect insect becomés greater, and in some of these insects the pupa stage is passed in a quiescent state; but in these the pupe still retain the power of motion. Fig. 190.—Machilis, Orprer IV.—Ruyncnora. Generai Characters.—The order Rhynchota, corresponding with the Hemiptera of Latreille, is distinguished from the other insects with an imperfect metamorphosis, by the possession of a suctorial mouth. This consists of a more or less flexible jointed rostrum, composed of the labial palpi, which forms a sheath within which four bristles, the analogues of the mandibles and maxille, are contained and protected from injury. By means of these bristles the insect wounds the plants or animals upon the juices of which it feeds, and the fluid nutriment is then sucked up by the action of an inflated appendage of the cesophagus. The head always bears a pair of compound eyes, and usually either two or three ocelli. Most of these insects possess four wings, which vary considerably in their structure. The segments of the thorax are usually distinctly separated. The legs are generally formed for walking ; but the anterior pair are sometimes converted into raptorial organs; and in the aquatic species the hinder legs are generally flattened, and fringed with bristles, to render them efficient organs of natation. Divisions.—The order Riynchota may be divided into two sub-orders, which, in fact, have frequently been regarded as distinct orders, especially by English entomolo- gists. In the first, the Homoptera, the anterior wings are usually of similar consistence throughout, and the mouth is turned backwards, so that the rostrum springs from the base of the head, and, in some instances, apparently from the breast. In the seconp 162 COCHINEAL INSECTS. sub-order, the Heteroptera, the anterior wings are almost always of a horny consistence from the base to the middle, or even further; the remainder of the wing being mem- branous, and the line of demarcation between the two parts perfectly distinct; in these the rostrum springs from the anterior portion of the head. Sus-orper I.—Homorrera. The Homoptera form three great groups or tribes. The first, the Coccina, is com- posed of numerous minute insects, of which the history is still very imperfectly known, Of these the tarsi have only one joint. The males are furnished with two wings, with a few straight nervures; they are destitute of: a rostrum, and pass their pupa stage in a state of repose. The females are destitute of wings, possess a rostrum, and appear to undergo no metamorphosis whatever. These curious little creatures, whose history is so singular that, some authors have proposed the formation of a separate order for their reception, are principally inhabitants of the warmer regions of the earth, although many species are found in our own country, where some of them are well known to gardeners under the name of “the bug,” from the injury they do to many plants, especially in hot-houses, Nothing can well be more dissimilar in appearance than the two sexes of these singular insects (Fig. 191). The females usually form a mere fleshy mass, often nearly destitute of limbs, and remaining attached to one spot upon the branches of the plant infested e them, from which they continue to suck nutriment, by the agency of their rostrum, until they attain a consider- able size. The males, on the contrary, are generally very minute and really elegant creatures, furnished with a single pair of filmy wings; the only representatives of the hinder wings being a pair of organs somewhat similar to the halteres of the Dip- tera. Hence some entomologists have put forward the opinion that the males of the Coccina are, in reality, dipterous parasites ; but this view is quite untenable. The abdomen of the male is generally furnished Fig. 191.—Cochineal Insect Consus cacti}. with a pair of long filaments, In some A, male; C, female. instances the females retain their limbs and power of motion through life. The larve of these insects are minute, oval creatures, resembling little Woodlice, which creep freely about the plants they inhabit, and live without any apparent change through the winter,—at least this is the case in one British species (the Coccus aceris), as observed both by Mr. Westwood and the author. In the spring the females become remarkable by their increased size ; they attach themselves to the branches of the sycamores, on which they live, and gradually swell until they resemble fleshy excrescences, about the size of asmall pea. At the same time the males change to the pupa state beneath the skin of the larva, which then resemble little oval scales attached to the bark, In the month of May the males acquire their full development, and when nearly ready for exclusion their little white tails may be seen projecting from beneath the grayish case formed by the skin of the larva. They emerge back- wards, so that the wings are pulled up over their heads, and immediately on leaving COCHINZAL INSECTS. 163: their case they seek the female. After the impregnation of their disproportionate partners, the great end of their existence, the males disappear ; but the females continue growing for some time, and at last lay their eggs in’ the midst of a mass of white cottony matter, between the bark of the tree and the lower surface of their own bodies. The latter at length become nothing but dry convex shells, beneath which the young are hatched. The development.of the other species of the order is very similar. Nor is the singularity of their natural history the only. claim that these insects. have upon our attention. Lowly as they maybe, in point of-organization, there are few insects that exceed them in commercial importance. The finest red dyes known to our manufacturers are. derived from these creatures. The Lecanium Ilicis, which inhabits the Ivee or ever-green oak of the countries round the Mediterranean, was. employed for this purpose by the ancient Greeks and Romans, as it is still by the Arabs; and until the introduction of the Mexican cochineal, another species, the Porphyrophora polonica, which lives on the roots of the Scleranthus perrennis in, Central Europe, was much used for the same purpose. The Mexican cochineal, which has driven the others out of the field, is-also a species belonging to this group, the Coccus cacti (Fig. 191), which lives as a parasite upon the Nopal,.or Cactus opuntia—a plant very common in Central America. The commercial importance of this insect is shown by the fact, that'in 1850 no less than 2,514,512 Ibs. of cochineal were. imported into Great Britain alone; and as about 70,000 insects are supposed. to be contained in a pound of this substance, we may form some idea of the: numbers annually destroyed. For many years the cultivation of cochineal was entirely confined to Mexico; but the insect has lately been introduced into Spain and the French possessions in Africa, with some prospect of success, A fourth species, of great importance, is the lac insect (Coceus: acca), an inhabitant of the East Indies, where it feeds upon the Banian-tree (Ficus religiosa), and some other trees. To this insect we are indebted, not only for the dye-stuffs known as Jac-dye and lac-lake, of which upwards of 18,000 cwts. were imported in 1850, but also for the well-known. substance called shell-lac, so much used in the preparation of sealing-wax and varnishes. In all these cases it is only the female insects that yield the colouring matter. In one genus of Coccina' (Dorthesta), several species of which are found in this country, the female—which, although apterous, is active in all stages—is completely covered with a snow-white secretion, which gives it more the appearance of a little: plaster-cast than anything else. In a second tribe, the: Phytophthiria, or Plantzlice, both sexes are either wingless or furnished with four distinctly. veined wings. The rostrum springs apparently from the breast, and the tarsi are. two-jointed and furnished with two claws. The greater part of this tribe is composed of the. Aphides, or Plant-lice (Fig. 192), whose extraordinary history renders them one of the most ‘interesting groups of insects. These creatures mustbe well. known to everyone. They: are all small animals, witha more or less flask-shaped body, furnished with six feet and a-pair of antenne, and usually with a pair of short tubes close to the extremity of the abdomen, from which a clear sweet secretion exudes. Both Fig. 192.—Aphis Rose. sexes are sometimes winged, sometimes apterous; and the individuals of the- same species: are often winged and apterous at different periods of the year. They all live upon plants, the juices of which they suck; and when they occur in great numbers, often, cause great damage to vegetation. Gardeners L 164 APHIDES. and farmers are well aware of this. Many plants are liable to be attacked by vast swarms of € 5 resemble the Rhynchophora ; but their pig. 2¢9—1, 2, Tomicus typographus, 3, 4, Hy- heads are broad and flat, not distinctly pur pus ipiniperds, (naire fize and mugnified), rostrated, and the antenne are inserted eer ese beneath the lateral margins of the head. Although these insects are of small size, 220 HETEROMEROUS BEETLES. the damage which they occasion in forests is often enormous. The Scolytus destructor, a common British speeies, destroys great numbers of elm-trees ; but the ravages of some other species, in the pine-forests of Germany, are almost incredible. Of these the commonest are the Tomicus typo- graphus and the Hylurgus piniperda (Fig. 269). The former receives its name of the Typographic Beetle from the circumstance that the ‘burrows formed by it,in feeding upon the soft wood, immediately -within the bark, often present a Fig. 270.—Track of Tomicus typographus. ‘rude resemblance to printe’l cha- .racters (Fig. 270). The devastations of these apparently contemptible foes are sometimes.so formidable, in the pine-forests of Germany, that prayers for their restriction are offered up in the churches ; and we are told that, in the year 1783, at least'a million and a half of trees were destroyed by these insects in the Hartz forest alone. - Szetion ITI].—Herrromera, Nearly all the insects of this section of the Coleoptera have four joints in the posterior tarsi; whilst the other four feet are composed of five joints. They are divided by Mr. Westwood into two tribes—the Trachelia, in which the head forms a distinct neck behind the eyes, and the Atrachelia, whick possess no distinct neck, the head being immersed up to the eyes in, the thorax. The Trachelia are generally active diurnal insects, frequently adorned with gay colours. Their bodies are often soft, the elytra flexible, and sometimes much shorter than the abdomen.. To this tribe = ~ belongs the Blister-fly (Lytta Ce ees . a vesicatoria, Fig. 271), the im- Ws eww \ ° portant medicinal uses of which are so well known. ~ ~~ ———<_ \ ee. é EEE ESSE WWE 5 These insects are common in OP en the south of Europe, and Fig. 271.—Lytta vesicatoria. specimens have occasionally been met with in England ; they feed principally upon the ash. Many other insects belonging to this tribe also contain a substance which has the effect of raising blisters when applied to the skin ; and these are employéd in their native countries in place of the Lytta vesicatoria, The species of Meloe, several of which are found in- Britain, possess this property; which, however, seems in all cases to increase in intensity in proportion to the heat of the country in which the insects live. The species of Mele are soft, sluggish Beetles, with short elytra and no wings, which may be found crawling about amongst the grass, in warm sandy places, in the early summer. The young larva, on first leaving the egg, closely E CHURCHYARD BEETLE—PENTAMEROUS BEETLES. 221 resemble those of the Strepsiptera already described (see p. 398); and as they attach themselves in the same way to wild bees, it is supposed that they are afterwards parasitic upon the bee larve. Hence some entomologists regard the Strepsiptera as a group of Coleoptera nearly allied to these. The curious Ripiphorus paradozus—a small Beetle also belonging to this group—is parasitic in the nests of the common Wasp; and many other species appear to be parasitic in their larva state. One of the most beautiful of the British species is the scarlet Pyrochroa rubens, which is found about hedge- banks in the neighbourhood of London. In the Salpingide, which appear to connect this group with the preceding, the front of the head is produced into a short snout. The Atrachelia are generally black, or of dull colours, nocturnal in their habits, and slow in their motions, usually crawling upon the ground in obscure situations. A few are found upon trees and plants ; and these, in their structure, evidently approach the pre- ceding tribe. A very good example of this group is furnished by the common Blaps mortisaga (Fig. 272), which bears the not particularly inviting English name of the Churchyard Beetle. These insects are generally found in dark and dirty places about houses, in cellars and similar situations. Another species is the Tenebrio molitor, of which the larva, found in flower, meal, &c., is well known as the Meal- worm, Other species live under the bark of trees, and ,. in decaying vegetable matter; but comparatively few are ai i found in this country. Secrion IV.—PEentTamera, It is in this section that we find the greatest variation in the number of joints in the tarsi. A great number of the insects of which it is composed would require to be distributed amongst the preceding sections, if we allowed none but truly Pentamerous beetles to be arranged here; these, however, are exceptions to the general rule, and the - majority of the insccts placed in this section have tarsi composed of five distinct joints. As the number of Pentamerous Beetles is very great, and they exhibit a corresponding diversity of structure and habit, their subordinate divisions are, of course, very nume- rous. They may, however, be divided into eight principal tribes, of which six have the outer lobe of the maxille of the usual form, whilst in the other two it is jointed and palpiform (see Fig. 171, c). Of the former, the Serricornia are principally distinguished by the structure of their antennez, which are usually rather elongated, filiform, or tapering towards the extremity, and serrated or pectinated. The penultimate joint of the tarsi is often bilobed. In some of these insects, forming the sub-tribe Malacodermata, the body is usually soft, and the insects, in their general form, present a considerable resemblance to many of the first group of Heteromera. They are further distinguished from the Sternoxia, forming the second sub-tribe, by having the prosternum of the ordinary form, and not produced into a spine posteriorly. Many of these, such as the insects well known to children as Soldiers and Sailors (Telephori), are predaceous in their habits, whilst others are wood-borers, and some feed on dry animal substances. Of the wood-boring species, one, the Lymexylon navale, infests oak timber, to which it frequently does incredible mischief in dockyards. It is common in the north of Europe, but appears to be rare 222 DEATH-WATCH—GLOW-WORM. in England. Other species, which also bore into timber in their larva state, are well known by the name of the “ Death Watch” (Anobium, Fig. 273), from their habit of making a ticking noise by knocking with their jaws against the woodwork upon which they are standing. They are little creatures, which often do great damage to furniture in houses. When touched, they contract their legs and counterfeit death,—a piece of mimicry which they are said to keep up even when exposed ‘to uw heat sufficient to Fig. 273.—Anobium striatum, natural Fig. 274.—Glow-wormi (Lampyris noctiluca), size and magnified. mate and female, roast them. To this group also belongs the Glow-worm (Lampyris, Fig. 274), whose lamp has so often been the theme of the poet’s song. The female alone is lumi- nous. It is a flat, grayish-brown creature, quite destitute of wings. The male, on the contrary, is active, and flies well; and the luminosity of the female appears to be intended to attract her volatile companion. The larve of some species of the genus Clerus live parasitically in the nests of Bees and Wasps, feeding upon their larve. In the Sternoxia the prosternum is produced in front into a lobe, and behind into a spine, which is received in a small cavity of the mesosternum. By the assistance of this apparatus (the spine being drawn out of its groove and then suddenly brought into it again) many of these insects (the Elaterid@) are enabled to execute considerable springs, when laid upon their backs. The larvae of some species are wood-borers; those of others live in rotten wood; and some inhabit the ground, feeding upon the roots of plants. One of the latter is well known to agriculturists as the Wire-worm. Some of these insects are luminous in the dark, They are the Fire-flies of tropical countries. The light is emitted from two large oval spots on the thorax. Others are remarkable for the metallic splendour of their colours; of these (Buprestid@) very few are found in Europe; but the exotic species are numerous, and often attain a large size. The vast tribe of the Lamellicorn Beetles (Lamellicornia) is characterized by having the antenne terminated by a club, composed of several leaf-like joints, laid together like the leaves of a book. This tribe includes an immense number of species, some of which are amongst the largest and most splendid of insects. In the Stag Beetle (Lucanus cervus, Fig. 91), the leaves are short and distinct, rendering the club pecti- nated; whilst in the common Cockchafer (Melolontha vulgaris) they are of considerable length, especially in the male, and fold up like the leaves of a fan. These insects fly well, but heavily, with a loud whirring noise; but they generally crawl slowly. The larve are thick fleshy grubs (Fig. 275), furnished with a distinct head, and with six jointed feet, and have the hinder part bent down. They live in very various situations, in dung, in decaying vegetable matter, and in the earth, feeding upon roots, They usually pass several years in the larva state, and change to the pupa in the interior of ROSE BEETLE—SACRED BEETLE. 223 a sort of cocoon, formed of particles of the surrounding materials, agglutinated together by a sticky secretion (Fig. 275). Many of the perfect insects are found in the same situations as their larve, espe- cially in the case of the Dung- feeding species. Of those which live in rotten wood, many, like the beautiful Rose-chafer of our own country (Fig. 275), and its still more splendid foreign allies, frequent flowers in their perfect state; and the common Cockcha- fer, the larva of which feeds upon, and often does great mischief to, the roots of plants, lives entirely upon leaves, after it has under- gone its last change. Many of the Dung-beetles, amongst which the Sacred Beetle of the Egyptians (Fig. 276), holds a prominent place, are re- ‘markable for inclosing their eggs in a small pellet of dung, which they then roll along with their hind legs, until they drop it into a hole which they have dug for its reception. Others, like the common Geotrupide and Aphodiide of our own country, are contented with depositing their eggs in the midst of a plentiful supply of food. The forms of some of these insects are extremely curious ; Fig. 275.—Larva, Pupa, and Imago of the Rose-beetle (Cetonia aurata). Fig. 276.—Scarabeus gyptiorum. Fig. 277.—Dynastes Hercules (reduced). and many of the larger tropical species are furnished with enormous horns on the head and thorax, which give them a singular appearance. The Dynastes Hercules (Fig. 277) is one of the most remarkable of these. It is a native of Brazil, and is one of the largest Beetles ; sometimes attaining a length of five inches. The classification of the insects which we refer to the four following tribes, and the ar- rangement of the latter, are still in a most unsatisfactory state; and almost every writer upon this branch of Entomology puts forth views different from those of his predecessors. 224 CARRION-EATING BEETLES. In the Helocera, which appear to make the nearest approach, both in structure and habits, to the Lamellicorn Beetles, the antennz are terminated by a knob, composed of several joints, which are sometimes pressed closely together, and sometimes loosely con- nected, so as to give the club a serrated appearance. They are further distinguished by their flattened contractile limbs, each portion of which folds closely upon its neighbour ; the whole, when thus reduced to the smallest compass, being received in cavities of the lower surface of the body. This position is always assumed by these Beetles when alarmed ; and, from this assumption of a death-like attitude, some of the commonest species have received the name of Mime Beetles. These insects, both in the larva and perfect states, are commonly found in cow-dung; a few also inhabit rotten wood; some are to be met with under the bark of trees, and a few in carrion. This tribe includes two groups :—the Histeride, smallish insects, generally of a black colour, with geniculated antennae, and the elytra rather shorter than the body, which is usually of a square form; and the Byrrhide, with straight antenne, and the elytra as long as the abdomen. The latter are of a round or oval form, whence they have received the name of Pill-beetles. The next tribe, the Necrophaga, includes an immense number of small and moderate sized insects, which live for the most part, both in the larva and perfect states, in decomposing animal and vegetable substances. A good many are also found under the bark of trees, and in Fungi, Like the preceding insects, these have clavate antennz, but their legs are not contractile, The nearest approach to the preceding tribe is made by the Dermestide, small Beetles, clothed, like the Byrrhide, with minute hairs, which often do great damage to skins and furs, and other dry animal matter. The commonest species, Dermestes lardarius, has received its specific name on account of the fondness exhibited by its curious larva for bacon. The largest and most interesting insects belonging to this tribe, are those of the family Silphide, which includes the Burying Beetles (Necrophori, Fig. 278) and their allies, The Burying Beetles are prompted by their instinct to bury any small animals, or pieces of carrion, as a provision for their young. In many cases several of them set to work together, getting under the animal to be buried, and digging the earth out with Fig. 278.—Burying Beetle (Necrophorus). Fig. 279.—Hydrophilus Caraboides, their feet. In this way they will quickly bury animals many times their size, such as mice and small birds. These insects:are not uncommon. They run and fly well; and some of them are adorned with bright orange-coloured bands; but they diffuse a most abominable odour, arising probably from the nature of their food. _The insects of another small tribe, called Philhydrida, from their generally aquatic habits, also have clavate antenne, but these are usually very short, whilst the maxil- lary palpi are of great length, and often longer than the antennw. Most of these insects live constantly in the water; and their legs are generally more or less flattened, to render them efficient as natatory organs (Fig. 279). One of the largest British Beetles, BRACHELYTRA—WATER BEETLES. 225 the Hydrois piceus, which isnot uncommon in ponds in some localities, belongs to this tribe. It also includes a group of small hemispherical Beetles (the Spheridiide), which constantly inhabit dung. The aquatic species are carnivorous in their habits, and the larger ones will often attack young frogs and fishes. We now come to a group, the location of which has given much trouble to entomo- logists, as, although it is undoubtedly nearly allied to the Necrophaga, its introduction in the neighbourhood of that tribe always appers to interrupt some natural affinities. The active predaceous habits of some of the larger species, of which the Goérius olens (Fig. 280) is a very common example, seem also to point to an alliance with the true carnivorous Beetles; and, on the whole, this is perhaps the most natural position for these insects. They are cha- racterized by their generally filiform antenne, and by tke shortness of their elytra, which always leave a con- siderable portion of the abdo- men uncovered. The name Brachelytra, given to the tribe, refers to this character. The wings, however, are usually ample, and the insects fly well. They are generally of an elongated form; and the abdomen, which is horny on both surfaces, possesses great mobility. It assists in tucking the wings under the elytra after flight; and the insects generally raise it when alarmed or angry. This attitude has obtained, for the insects figured above, the appropriate name of Cocktails. The derivation of their other vulgar denomination, Devi?s Coach-horses, is not so clear. The larve are very similar to the perfect insects, both in appearance and habits. Many of them feed in carrion ; others in rotten wood, and other decaying vegetable matters. The number of joints in the tarsi varies greatly, but five is the prevalent number. In the two following tribes, which close the series of Coleopterous insects, the outer lobe of the maxille is jointed and palpiform, so that these insects appear to have six palpi. They are pre-eminently carnivorous and rapacious in their habits. The former, constituting the tribe Hydradephaga, are characterized by their some- what flattened oval body, and by having the legs, especially the hinder pair, compressed and fringed with bristles, so as to become powerful paddles. Many of these insects are of considerable size, the Dyticus marginalis (Fig. 281), a species very common in ponds, attaining a length of more than an inch; whilst many foreign species are much larger. The larva is of an elongated form, tapering towards the tail, which bears a pair of tubular ciliated appendages, which the creature applies to the surface of the water to obtain a supply of air for its respiration. It is as predaceous as its parent, seizing upon other aquatic larvee with its long curved mandibles, and quickly sucking the juices out of the body of its victim. These mandibles are perforated throughout, and it is through these tubes that the larva sucks its nourishment. When about to change to the pupa state, the larva burrows into the bank of its native pond, and there undergoes its transformations. The well-known Gyrini, or Whirligigs—little black Beetles, which may be seen describing circles upon the surface of any piece of water— Fig. 280.—Goérius olens. 226 GROUND BEETLES. are also placed in this tribe, although their claim to such a position is rather doubtful. Fig. 281.—Dyticus marginalis, A, larva; B, perfect insect. Fig. 282.—Carabus. The insects of the last tribe, the Geodephaga, resemble those of the preceding group in their carnivorous propensities, and in the structure of their mouths; but their legs are always constructed for terrestrial progression. They are exceedingly active, and often beautiful insects; generally nocturnal in their habits, concealing themselves during the day under stones and in holes in the ground. The larve are elongated, flattened, and usually covered with a horny integument. In their predaceous habits they resemble the perfect insects. The insects of one family, the Cicindelide, which have received the name of Tiger- beetles, from their eminently predaceous propensities, are more diurnal in their habits than the rest of the tribe ; the common English species, Cicindela campestris (Fig. 283), may be found flying and running about with great agility in the hottest sunshine. This insect is of a beautiful green colour, with whitish spots; and its mouth is armed with a most formidable pair of sharp, toothed jaws. The larve are of a singular form; they live in holes in the ground, maintaining themselves by means of a pair of hooks placed on the enlarged eighth segment of their body, at such a height that their heads exactly occupy the mouth of the hole. Here they lie in wait for their prey, which consists of other larva; and the moment one of these approaches their den, they rush upon it with the greatest ferocity, and bear it off in their jaws. Fig. 283.—Cicindela campestris. ——_+——- DIVISION IV.—MOLLUSCA. General Characters.—The Moxtvuscovs division of animals consists of crea- tures whose bodies are universally of a soft consistence. They are inclosed within a soft, flexible skin, called the mantle, which possesses great contractile power ; and their le MOLLUSCA, 227 motions ave principally ‘performed: by the extension and’ contraction of part of their substance, The symmetrical arrangement of all the organs on each side of a central line, so remarkable in the preceding division, here almost disappears, or is only recog- nizable in the position of the organs of sense attached to the head. The nervous system consists either of a single ganglion, giving off filaments to the various organs of the body, or of several ganglia, placed’ somewhat irregularly in different parts of the body, communicating by nervous threads with a larger mass placed in the head, or in the neighbourhood of the cesophagus. This mass consists of several ganglia, of which the more important, constituting the brain, are placed above the esophagus. These are | ‘generally accompanied by other ganglia placedvbelow that organ, which are united by filaments with the supracesophageal ganglia, or brain ; thus forming a ring sttrrounding the esophagus, ‘The supracesophageal ganglia furnish the nerves to the special organs of sense placed upon the head, The ganglia belonging to the different organs of the body: communicate with the ring surrounding the esophagus. x Most of the Mollusca possess special organs of touch, in the shape of tentacles, arms, or lobes, situated on the head or in the neighbourhood of the mouth, or of cirri upon other parts of the body. In addition to these organs, the skin, which is always soft, appears to possess great sensibility. The tentdeles of the Mollusca are; either two or four in number ;' they are capable of being completely retracted. into the head by a process very similar to the turning in of the finger of a glove, and are again exserted by reversing the process. The eyes, when present, are two in number, sometimes placed immediately on the head, sometimes supported at the extrémity, or on the sides, of the tentacles. In the highest class the vieual organs attain a perfection equal to that exhibited by the fishes,—the lowest class of vertebrated animals, In some of the lower Mollusca.small coloured points are met with, sometimes singly in the neighbourhood of the brain, sometimes in considerable numbers on the edges of the mantle. These, from their structure and appearance, have received the denomination of ocelli, and have been regarded as rudimentary eyés,—za determination which, althougk it may be correct in some instances, is very doubtful in others. It is remarkable, also, that many species, which are quite destitute of eyes when arrived at their mature form, are furnished with those organs at their first issuing from the egg. Auditory organs appear to be possessed by nearly all the DMol- dusea. They usually consist of small vesicles placed close to the cephalic ganglia, containing’ a clear fluid and a small calcareous concretion (otolithe), which is sometimes of a roundish, sometimes of a crystalline figure, and is in u perpetual state of vibration. The senses of smell and taste also appear to be exercised, to a certain extent, by most of these animals; but whether any organs specially devoted to these functions really exist, must still be considered doubtful. The movements of the Mollusca are generally executed by means of a muscular organ, called the foot, which varies greatly in its form, in accordance with the habits of the creature. The foot consists of a mass of muscular’ fibres, ranning in various p directions, by the contraction of which its movements are effected. Fig. 284.— Conus In a great number of Mollusca. the foot. forms a flat disc (Fig. hepraiens, 284), which adheres to any substance to which it may be applied, and thus, ‘by the alternate’ contraction and dilation of: its different. parts, enables its possessor to craw] P 228 MOTIONS OF MOLLUSCA. slowly along. In others, the foot is bent upon itself, so that its sudden extension causes the animal to perform a considerable leap. The foot is also the agent by means of which the burrowing species bury themselves in the sand or mud; and in the species whose instincts lead them to bore into the solid rock, it is also called into requisition: its sur- face in these cases being covered with minute silicious particles, which assist greatly in the enlargement of its owner’s stony dwelling. But Fig, 285.—Pinna, with its byssus. although most Mollusca possess a greater or less power of motion, others are confined to a single-spot, during all but the earliest period of their existence. These have no occasion for a foot, and in them this Fig. 286.—Octopus Hawaiensis. organ is either wholly undeveloped (as in the oyster), or serves merely to support a glandular organ, from which a silky matter (called tho dyssus) is secreted, which serves STRUCTURE OF MOLLUSCA, 229 to attach the animal to submarine objects. This modification occurs in the common Mussel (Mytilus edulis) ; but it is still more remarkable in the Pinne (Fig. 285), in which the silky matter is of a very fine texture, and so abundant that it is woven into small articles of wearing apparel, such as gloves and stockings. In the highest class of Mollusca, the Cephalopoda, the mouth is surrounded by a variable number of arms (Fig. 286), which not only serve as organs of motion, but for the capture of prey. To render these efficient prehensile organs, they are covered on the inner surface with numerous cup-like sucking organs. The intestinal canal in the Mollusca presents almost every variety of form, from @ simple cavity to a complicated intestine. It is, however, always furnished with two openings, a mouth and an anus, the latter being frequently situated on the side of the body, not far from the anterior extremity. The liver is always’of great size, generally enveloping all the other intestines, The circulation of the blood is effected by means of a distinct heart, which usually communicates with a regular vascular system; but, in some instances, the circulation takes place in a system of sinuses or cavities amongst the organs of the body. In the former case the heart is often composed of two or more chambers, from which large arteries arise to convey the blood to the various organs, It is again collected in the veins, through which it passes to the neighbourhood of the respiratory organs, where it is aérated by contact with the surrounding medium, and then passes to the heart. As most Mollusca are aquatic in their habits, their respiration is almost always effected Cd ce ve as} ay Tee Ll, Mt = | TIN nein SSNS Ami 1 t ' ' 1s oe av asc vv Fig. 287.—Organs of circulation and respiration in the Cuttle Fish (Sepia). ¢, heart; as, superior artery; a, ventral artery, with its branches av; ve, principal vein, or vena cava; cb, branchial hearts; 67, branchis ; vb, br . aca é vein; ab, branchial arteries ; v0, ve teal Nn ‘anchial vein; du, bulb of branchial by means of branchiw (Fig. 287). These are usually composed of a series of minute ' lamina, or of broad plates, over which the water flows. They are sometimes attached to the surface of the body but generally inclosed within the mantle, or placed in a 230: SHELLS OF MOLLUSCA. cavity: in its:interior, called the branchial or respiratory chamber. The water necessary for respiration is sometimes drawn into. this cavity, and again expelled by muscular contraction. In this.case its recoil: frequently serves to drive the animal slowly through the water, and some species swim with great rapidity in this manner. In other cases, the inner walls of the canals, through which the water passes, are lined with a by the action of which a constant.current is kept up. Not. ey these 1 Fig. 288.—Psammobia, with long siphons. 5 canals are drawn out into tubes (Fig. 288), called siphons, which are often of _ great, length in the burrowing species. ‘The air-breathing species, of which the common Snails and Slugs are well-known’ ! éxamples, are furnished with a pulmonary sac or lung, into which the air penetrates ;. and where it comes-in contact with the blood oontainad i in the numerous vessels with | which the walls of the sac are supplied. Many of these animals live in water; but | they are compelled to come to the surface to breathe ; and all of'them appear to require a moist atmosphere. Most of the Mollusca are protected by a hard calcareous covering? or shell, which is secreted by the mantle, and is gradually increased'in size, in proportion to the growth | of the animal. In many this is composed of a single piece (Fig. 289), which is usually ' a spiral tube, gradually i increasing in sige towards the open extremity, from which the . animal protrudes itself when in action. Shells of this description are called univalves, ' In others the shell is composed of two pieces, or valves (Fig. 290), attached to each other 1. Pig, 989.—Univalve Shell (Trochus). Fig. 290,—Bivalve suell (Pectunculus).. at:one- pont by a hinge, which is-usually furnished with an elastic ligament, serving to” open the,valves; when the tension of peculiar muscles, whose office it is to keep the | shell closed, plan’ This‘is denominated a divalve shell:. These differences in the- STRUCTURE AND FORMATION OF SHELL. 231: o : asmall but singular group of Mollusca, nearly : allied to the univalve Limpets, have an oval ~ ' shell composed of eight moveable plates, which ' Woodlice; and they have been regarded as stracture of the shell correspond with differences in the conformation of the: animals. The bivalve Mollusca exhibit no traces,of any-distinct head; whilst, in the univalves, this part of the body is well-marked, and usually furnished with ‘special organs of sense (tentaoula, eyes, &c.) Heh casa Uy oe Biel pa te & Poa ine ae . The older naturalists also recognised a group of multivalve shells, or shells composed , ofseveral valves. The majority of these belonged tothe Cirrhopod order of Crustacea (page 296), which were regarded, as Mollusca bythe earlier, observers. The Pholades, however, which in other respects. are true bivalve Mollusca, are furnished with a pair of accessory plates in the neighbourhood of the hinge; whilst the Chitons (Fig. 291), AMAA KG ih (( (CK ‘ \ i Vi Vi HH i i Hh WT give them a great resemblance to enormous HM forming a sort of transition towards the Arti- culated Division. , Fig, 291.—Chiton (side view). - Many Mollusca are not furnished with a shell, or have only a small calcareous plate inclosed within the mantle, These are called naked Mollusca ; but it is remarkable that ' most of them are provided with a small shell at their first quitting the egg. In the shell-bearing or testaceous Mollusca, this embryonic shell, which often differs greatly in : shape and texture from the shell of the mature animal, forms the commencement of the latter, additions being constantly made to its free edge by the secretion of calcareous matter at the edge of the mantle.. é Shell consists principally of carbonate of lime, with a small quantity of animal matter. The calcareous matter is deposited in the cells of the edge of the mantle, which are in contact with the free margin of the shell. In these it gradually increases | in quantity, until they harden, and become attached to the previous shell formation. , In this manner, as the animal continues growing, these attached portions of the mantle | are thrown off, and left behind; and it is usually only at the margin of the shell that | the deposition of new shelly matter is effected. The delicate membranous part of ‘the’ | mantle, which lines the interior of that part of the shell inhabited by the animal, has, however, the’ power of secreting a thin layer of shelly matter upon the inner surface. This is frequently of a pearly lustre; and in many bivalves a new layer of this substance is deposited at the same time that the size of the shell is increased by additions to its margins,—for, it must be observed, that the formation-of new shell is not constantly going on, but appears to be subject to periodical interruptions, indicated by lines on the surface of the shell; these are called lines of growth, In many cases the margin of the mantle, instead of being even, presents lobes or tubercles, which | produce corresponding’ irregularities, ribs, tubercles, or spines, on the surface of the shell (Fig. 292). In this manner, as the spines and other projections are usually formed at the mouth of the shell, at the close of each.period of growth, the surface of the shell becomes more or less covered with a series: of these prominences, each of which indicates the conclusion of a period of increase. When these spines stand in the way of the further growth of the shell the creature is able to remove them, probably by the action of some solvent fluid. The shell is almost always coated with a layer of animal matter (the epidermis), of greater or less thickness. It is of a horny consistence, and serves to protect the shell from the action of the carbonic acid, which is often dissolved in great quantity, espe- 232 REPRODUCTION OF THE MOLLUSCA. cially in fresh water, It is in fresh-water shells that this layer of epidermis attains its greatest development, and the colours of these are generally due to it, In many places, however, the epidermis is an insufficient protection against the corroding action of the water, which often eats deeply into the substance of the shells of the Mollusca which make it their habitation. Sexual reproduction prevails amongst the Mollusca; and it is only in the lowest forms that we meet with gemmiparous pro- pagation, The sexes are gene- rally on separate individuals; but hermaphrodism is not un- common. Nearly all these ani- mals are also truly oviparous, although « few produce living offspring ; the ova being retained in the oviduct until the exclu- sion of the young animals. The eggs vary greatly inform. They are sometimes, as in the Land- snails, laid separately, each in- closed in a shell of variable con- sistence ; but in most cases they are agglutinated together into a mass, which sometimes takes the form of a ribbon, attached by one of its edges to some sub- marine body. In some marine species the eggs are inclosed in leathery ‘capsules, which are often united to form a large mass. Each capsule contains numerous eggs. The young Mollusk, whilst still in the egg, is almost always furnished with a delicate, pellucid shell, even when it is ultimately to be naked. In this case the embryonic shell is cast soon after the young animal makes its escape from the egg. The young of the sedentary species, also, are active at this stage of their existence, swimming freely about in the water, until they select some spot in which to take up their permanent abode, Divisions.—Although these are the general characteristics of the Fig. 293.—Fgg of animals belonging to the Molluscous division, those forming the two eae first classes, the Bryozoa and the Tunicata, and especially the former, differ from the other Mollusca in so many respects, that they have been formed into a separate subdivision, the Molluscoids. They are distinguished from the true Mollusca, by the very low development of the nervous system, which is composed only of a single ganglion, placed in the neighbourhood of the wsophagus, and giving off nerves in various directions. Of these two classes, the Bryozoa are characterized by the presence of tentacular organs in the neighbourhood of the mouth, whilst the Tunicata are desti« tute of such organs, Fig. 292.—Murex. THE BRYOZOA, OR MOLLUSCOID POLYPES. 233 Sus-prviston I.—Motiuscomwa. Crass I,—Bryozoa, General Characters,—The class of Bryozoa is composed of small animals, which always grow together upon a common stock, in the same manner as the compound Polypes, with which they were formerly arranged. Each animal resides in a separate cell, within which it can usually retract itself entirely; the cells are sometimes soft and flexible, sometimes horny, and sometimes calcareous. They frequently stand upon short footstalks, rising from a tubular stock, which creeps over the surface of stones and aquatic plants, in the same way as the horny stems of many of the hydroid polypes. In other cases the cells are sessile, forming a crust upon submarine objects, whilst in others the colony is attached only by its base, with the opposite extremity floating freely in the water. In these the stock is more or less branched, and often leaf- like. The cells are in general partially free; but in some of the stony species they form a calcareous mass, presenting some resemblance to the true Corals, from which, however, they may always be distinguished by the absence of the calcareous partitions which the latter invariably exhibit. In some species the cells are closed by a cover when the animal is withdrawn ; but this protection is generally wanting ; and in the species with flexible cells, the complete retraction of the animal draws in the edges of the cell, which then close the aperture entirely. The interior of the cell is lined by the skin of the animal, and the cavity of the body is filled with fluid, in which the intestinal canal floats freely. It also contains the muscles by which the animal protrudes and retracts itself. The fluid, which is perfectly clear and transparent, is kept in constant motion by the action of cilia, with which the inner surface of the cavity, and the outer surface of the intestine, are covered; and this movement, which extends into the tube of the common stock, is interesting to the naturalist, as it is apparently equivalent to a true circulation of the blood. The most characteristic peculiarity of the Bryozoa is their possession of ciliated tentacula placed at the anterior extremity of the body. By the action of the cilia a sort of vortex is produced in the water, by which the minute animals that constitute the food of the creature are carried down into the mouth, which is placed between them. These tentacles probably serve also as respiratory organs, as they communicate at their bases with the general cavity ; and the fluid with which this is filled appears to circulate in the tentacles by ciliary action. The mouth leads into a muscular ceso- phagus, below which, nearly at the bottom of the cavity of the body, the stomach is situated. The intestine springs from the upper part of the stomach, near the point where the cesophagus enters, and leads to an anal opening, situated just below the tentacula, These parts are well shown in the engraving (Fig. 294), which affords a good illustration of the subject. The colonies of the Bryozoa are, of course, increased by gemmiparous reproduction ; but the establishment of new colonies takes place by the ordinary mode of propagation by ova, and it is somewhat singular that in these sedentary animals the sexes are frequently, if not always, on separate individuals. The sexual organs are attached 23£ APS ae ea BRYOZOA. 8) 8 a either to the surface of the intestine or to the inner wall of the cavity of the body. They are seen at the bottom of the stomach in the cen- tral individual of the group figured (Fig. 294). The contents of these organs (ova and sperma= tozoa) appear to be set ” free in the cavity of the ‘body, where they are carried from place to place by the currents of the nutritive fluid, and in this manner come in contact. The impreg- . nated eggs escape ‘into the water through a minute aperture’ placed close to the anus. The ° : & embryo breaks out of the Fig. 294.—Plumatella. egg in the form of a, cili- ated animalcule, which swims about for some The individual on the left is completely retracted within its cell; that 4:4 : in the middle is seen from behind, and that on the right from the time without change. side. It then becomes cup- shaped,.and.by degrees tentacles make their appearance at its upper margin, when the little creature fixes a, @ group of the natural size; 5, three individuals magnified ; ¢, anus. itself by its lower extremity, and becomes a simple Bryozoon. The changes which | the Bryozoon undergoes, are curious, It soon begins to form buds af its base, or gives off a creeping stem from which these arise at intervals; and in this manner a new aolony is.formed. In some cases the development of the embryo presents very remark- able phenomena. A ciliated embryo i is produced in each egg ; and in the interior of this, whilst still inclosed in the egg, two little Bryozoa, furnished with tentacula, make their appearance. The embryo then makes its escape, swims about for a time, and then | attaches itself, when the little creatures inclosed in it break out, and lay the foundation of a new colony. Divisions.—The Bryozoa form two very distinct ade In the Infundibutata, the animals, which are all marine, are characterized by having the tentacles placed in a circle round the mouth (Fig. 295) ; whilst in the Lophepoda, which inhabit fresh water, these organs are situated upon two arms given off from the sides of the body (Fig. 294), Orper I.—Inrunpreunata. The common Flustre, or Sea-mats, so abundant on our shores, are well known examples of this order. They are flat and foliaceous in their form, presenting a consi- derable resemblance in-appearance to pale brown sea-weeds, with which they are in fact generally confounded by sea-side visitors, But when carefully examined, these " Jeaf-like bodies will be found to consist of a multitude of small horny cella, opening at SEA MATS. 235 the surface; and from each of these, when the polypidom is placed alive in a vessel of sea-water, thie little creatures may be séen protruding their’ tentacles. Many nomty led species grow upon the fronds of sea-weeds, over which’ they spread like a thin coating of ‘gauze, composed of similar cells, opening of course only on one side. Others -are found incrusting stones’ and other submarine bodies with a cellular calcareous mass. In many ‘species the cells are arranged so as to form a more or less thread-like, branching polypidom ; whilst others are fur- nished. with a creeping root, from which the ¢ells rise by stems of greater or less length. Some of the marine Bryozoa possess singular organs, the use of. which has not yet been satisfactorily: made out. These are attached to the polypidom, and from their close resemblance in form to the head of a bird, have received the name of Avicularia, They consist of a larger upper and a smaller lower piece; the latter being moveably articulated to its fellow; and the whole is frequently attached to the polypidom by a short footstalk. These organs are constantly in motion, and at the same time the two pieces frequently separate and close again, with a snapping move- ment, exactly like that: of a bird’s bill. Orver II.—Loryoropa. In this order, composed of inhabitants of fresh water, the Fis-295.--Bowerbankia. tentacles, which are more numerous than in the preceding, “'gyach} ay enue,” ae are placed upon » pair of long arms, which spring from the : sides of the upper extremity of the animal, and usually describe somewhat the form of a horse-shoe (Fig. 294). Their cells are usually of a leathery texture, nearly transparent, and usually spring from a rootstock of similar consistence, which creeps along upon the surface of stones or aquatic plants, in which situations these animals are not uncommon. In some species, however, the polypidom floats freely in the water (Cristatelia), and is of a gelatinous consistency ; in these the animals composing each eolony are usually three or four in number. Crass II.—Tountcata. General Characters.—The animals forming the class Tunicata, generally present the appearance of shapeless gelatinous masses. They are composed of two tunics; an outer, the-mantle; and an inner tunic, which lines ‘a large respiratory cavity. These tunics are continuous at the extremities of the body, where there are large openings; and the animal thus constitutes a tube, furnished with double walls, which are usually separated by a considerable space (Fig. 296). In the numerous compound Tunicata we find a modification of this structure. The animals forming one of these colonies are usually united by their mantles, which form a more or less gelatinous mass, in which the individual animals appear to.be imbedded. In many of these the body, or at all events the respiratory chamber, is bent round; so that the incurrent and excurrent orifices are brought to the same extremity of the body. In others the posterior apertures of several animals lead into a common canal. 236 THE TUNICATA. The outer tunic, which is composed wholly or in great part of a substance apparently identical with the woody fibre of plants, is usually of a tough or somewhat cartilaginous texture. The inner tunic is frequently furnished with a variable number of muscular bands, by means of which the internal cavity is contracted so as to expel the water which has entered for the purpose of respiration. The space between these tunics is occupied by a system of sinuses, through which the blood circulates, The water usually enters the respiratory chamber by the anterior orifice, and is then expelled by the posterior, In the free-swimming species this expulsion of the water constitutes the only means of locomotion possessed by the animal, which progresses slowly in the direction opposed to the stream of water. The ‘respiratory function appears to be performed to a great extent by the lining membrane of the respiratory chamber ; but the animals are also furnished with true branchie, which present two Pp Fig. 296.—Salpa. a, anterior orifice; , posterior orifice; J intestinal sac; c, heart; 6r, branchial chamber; m, mauscular bands; », ganglion. different forms. In the Salpe (Fig. 296), the branchia constitutes a flat or roundish band running through the respiratory chamber, furnished with cilia on its sides; in the other Zunicata, the branchial cavity contains a loose network formed of ciliated filaments, crossing each other at right angles. The intestinal canal is situated near the posterior part of the cavity of the body, opening by a simple mouth from the upper part of that cavity, The mouth leads into a winding intestine, which again opens by another aperture into the respiratory chamber. : The heart is usually placed in the neighbourhood of the digestive organs; it is ofa somewhat tubular form, and the blood is set in motion by a gradual contraction of its walls from one end to the other. In their circulation, if circulation it may be called, the Turicata exhibit a remarkable difference from all other animals. The blood does not circulate always in the same direction ; but after a certain number of pulsations in one direction the heart rests for a time, when its contractions commence anew in the oppo- gite direction, so that the blood really ebbs and flows. The nervous system consists of a single large ganglion, placed towards the anterior ' part of the animal, at its lower surface. Close to this is placed a vesicle containing otolithes, and therefore probably an auditory organ; although, from the presence ASCIDIANS. 237 of pigment spots upon the otolithes, it has been regarded as an eye by many observers. The Twnicata are all hermaphrodites; and it appears probable that some of them, at: any rate, are self-impregnating. The male and female organs have been detected in many species at the posterior extremity of the body, near the digestive system; but the former have been described as a liver. Besides sexual reproduction, however, many of these animals propagate by gemmation, some forming compound colonies, whilst others exhibit a regular “ alternation of generations.” Divisions.—The Tunicata have been divided into two orders, characterised by differences in the form of their respiratory apparatus. The Ascidie have the branchial organ composed of a network of square meshes; whilst in the Biphora it consists of a band running through the branchial chamber. Onper J.—Ascm1z, General Characters.—This order consists entirely of animals which are either attached by the base to submarine objects, or united together in various ways ; sometimes by the coalescence of their mantles, so as to form a gelatinous mass, and sometimes by means of a sort of common stalk, very similar to the polypidom of the Bryozoa. The efferent orifice of the branchial chamber accordingly, in almost every case, opens in the same direction as the inhalent orifice, either by the canal being bent round within the body of each animal, or by its communicating internally with a common canal of larger size, serving for several individuals, The young of the fixed Ascidians, when first produced from the egg, are furnished with a long tail, which gives them very much the appearance of minute Tadpoles. Ry means of this they swim about freely in the water, until the time arrives for them to attach themselves. The tail then gradually disappears; the internal organs make their appearance, and the animal soon acquires the form of its parent, In some of the compound Ascidians, however, « somewhat different process has been observed, The tailed embryo is formed in the egg, but this loses the tail whilst still inclosed. Several embryos surrounding a common canal are then formed in the substance of the original embryo, which thus constitutes the nucleus from which a new colony is produced by gemmation, Divisions.—The Ascidians form four great groups, or large families. In the com- pound Ascidians, or Botryl- lide (Fig. 297), the animals are united together by the coalescence of their mantles, so as to form a leathery or gelatinous mass, usually at- Roses tached to stones or sea-weeds; Fig, 297.— in this the separate animals Botryllus. are imbedded, generally ar- ranged in a more or less distinctly stellate form, round a common efferent canal. & Many of them are adorned with beautiful f colours, Fig. 298.—Perophora. The second family, the Clavellinide, * common stem; e, stomach; é, intestine; contains the social Ascidians, or those in TEE) aeia ee ene which the bodies of the animals are united, not by the mutual adherence of their outer 238 PYROSOMA. tunics, but by means of a sort of ereeping-stem which runs-along the surface of sub- marine objects, and gives rise at intervals to short footstalks, at the extremity of which the animals are supported (Fig. 298). “The separate “animals are produced by gem- mation from the creeping stems, which run in various -directions from the base of the original founder of the colony. The family of simple Ascidians, Ascidéide, is composed of animals which live separately, attached by the base to submarine bodies. They usually form shapeless masses of a cartilaginous ‘texture, often ‘of considerable size, which occur in great abundance in shallow water. A few species are eaten in some countries, The incur- rent and excurrent apertures are both situated on the upper surface of the animal, and the former is fringed-with tentacles, which appear to prevent the ingress of injurious matters into the respiratory cavity. The fourth family, the Pyrosomatide, appears to form a distinct transition from the Ascidia to the following order. In the structure of the respiratory organs they agree with the former; and like the majority of these they are compound animals; but the branchial chamber runs straight through the body, with the openings at opposite: extremities; as in the Salpe, with which they also agree closely, in the general é arrangement of their organs. The colonies of these singular creatures are in the form of a carti- laginous tube, open at one end. In the walls of this tube, formed by the: coalescence of the mantles of the animals composing it, the bodies of the Ascidians are separately imbedded; the branchial chamber of each passing completely through the wall from its outer to its inner surface. These animals are found in the seas of warm climates, where they float along in an upright position, but apparently possess no actual locomotive power. Like all the Tunicata they are luminous in the dark, and, in fact, appear to possess this faculty i in-a greater degree than any other members of the class, Their cylindrical form, upright: Fig, 299.—Pyro- position, and considerable size (they often attain more than a foot “soma (reduced). in length), render them exceedingly beautiful objects at night; and | they have been described as resembling little columns of fire. Oxper II.—Brenora, This order includes a group of free-swimming animals, usually of a glassy transpa- rency, the bodies of which may be compared to a tube, furnished with two openings, one for the entrance and the other for the exit of water. The walls of this tube are composed of a distinct outer and inner tunic, the latter furnished with bands of muscles, by the contraction of which the water is forced out of the cavity of the body, producing a recoil, which drives the creature in the opposite direction, The internal structure of these animals has already been described. They are distinguished from those of the other order by the bandlike form of the branchia. The intestines form a small mass above the posterior portion of the branchial cavity (Fig. 296) ; this is usually of a reddish or yellowish colour, and emits a phosphorescent light in the dark ; it is called the nucleus. The reproduction of these animals is attended with some very remarkable circum- stances, which were, indeed, the first facts accurately observed.in favour of what, for want of a better term, we must still denominate “the alternation of generations.’’ ‘Two forms of Salpe have-long been known and regarded as, at all events, specifically THE SALPZ. 239 distinct from each other. In one of these the individual animals are united together by their sides into a sort of chain, the movement of which through the water is effected by the simultaneous expulsion of water from the respiratory chambers of all the animals of which it is composed. In the other form the animals.are always solitary ; and these differ so much in their external appearance, and even in some points of internal anatomy,—such as the number of muscular bands in the inner tunic,—from isolated individuals of the social forma, that it is not at all surprising that they were long considered as distinct species. Accurate observations, however, commencing with those of Chamisso, published in 1819, have shown that each species of Salpa possesses individuals of these two forms. The associated forms are furnished with genuine reproductive organs, and produce a single young Sélpa of the solitary form; and this again produces, by internal gemmation, a chain or series of young animals of the form of its parent. The processes by which these different results are produced are exceed- ingly curious and interesting. The solitary Salpw exhibit at the hinder extremity, close to the heart, and connected with that organ, a single vessel, divided down the middle by a longitudinal partition. Through this the blood circulates, passing up on one side of the partition and down on the other. Upon the outer surface of this, which is called the gemmiferous tube by Mr. Huxley, the associated Salye are produced, making their appearance at first as mere buds, but gradualiy increasing in development with age ; and those at the hinder extremity of the tube being much further advanced than | those nearer the heart, When mature, these young animals quit the body of the | parent by an aperture in the posterior extremity of the outer tunic, sometimes singly, at others in a united chain, in which the animals adhere to each other with a very variable degree of force. Hach of these animais possesses both male and female organs, the latter furnishing, apparently, but a single ovum. It seems very doubtful, however, | whether the animals are self-impregnating, as Mr. Huxley remarks, that in the species examined by him the male organs did not appear to have arrived at their full develop- ment when the formation of the embryo had commenced, which, indeed, takes place | before the associated Salpa leaves the body of its parent. It is singular that these animals. are not oviparous, but truly, viviparous; the embryo being suspended | within the branchial cayity of its parent, and connected with the circulatory system of the latter by a distinct vessel, through which the blood may be seen to pass, the embryo also exhibiting a distinct circulation of its own ; phenomena so closély in ‘accordance | with those presented by the Mammalia, or truly viviparous Vertebrata, that naturalists have applied the name of placenta.to the vascular connexion between the parent Salpa and its young, As the young Salpa increases in. size and perfection, its connexion with its parent is gradually narrowed, until at. last. i breaks away altogether, and swims off as a free and perfect being. The Salpa are found in all seas, but most plentifully in those of frépicel. climates, which are often filled with them in such numbers that the voyager sails for days through maszes of these little gelatinous creatures. At night they are. exceedingly luminous ; and the chains of the associated forms especially are said to present a beautiful appear- ance. Svz-prviston II,—Morxvsca Proper. Divisions.—In the great sub-division of the true Mollusca, of which the. general structure has already been sufficiently explained, we may distinguish five great classes, of, which two are unprovided with any distinct head (Acephala), whilst the remainder present a head furnished with organs of sense (eyes, tentacles, &c.) Of the former, which are 240 CLASSIFICATION OF THE MOLLUSCA. always furnished with a bi-valve shell, the Palliobranchiata are distinguished by having no special breathing apparatus or gill, and by the presence of a pair of ciliated and usually spiral arms attached to the sides of the mouth (Fig. 301), the action of which carries the particles of food towards that aperture ; whilst in the Lamellibranchiata, or ordinary bi- valve Mollusca, these arms are wanting, and the respiratory function is performed by lamina gills. The Cephalophorous Mollusca are divided into classes by characters derived in a preat measure from the form and position of the organs of motion. Thus the Pteropoda are small Mollusks, which swim freely on the high sea by means of a pair of fin-like Fig. 301.—Lingula anatina, Fig. 300.—Creseis subulata. showing the ciliated arms. expansions attached to the sides of the body, at or near the head (Fig. 800). The Gas- teropoda are furnished with a fleshy foot, by the agency of which they creep slowly. along (Fig. 284) ; whilst the Cephalopoda (Fig. 286) have a circle of arms surrounding the head, with which they not only crawl upon submarine objects, but also seize their rey. a Crass IIT.—LAMELLIBRANCHIATA, General Characters.—The Lamellibranchiate, or ordinary Bivalve Molusca, are usually inclosed within a bilobed mantle, which, however, in some instances, is entirely closed, with the exception of apertures left for the admission of the water required for the respiratory process, and for the protrusion of the foot (Fig. 302). In all cases, however, the two sides of the mantle produce a calcareous shell, which is always composed essentially of two valves ; although, in some instances, they undergo such modifications“as to render the recognition of their original structure almost unre- cognizable. The two lobes of the mantle are always united at the upper part, where they are also attached to the sac inclosing the body of the Mollusk. At this part, also, the two valves of the shell are attached to each other by a sort of hinge, almost always furnished with teeth, which fit into corresponding cavities in the opposite valve, and are usually provided with an elastic ligament, which unites the two valves along the ANATOMY OF LAMELLIBRANCHIATE MOLLUSCA. 241 hinge-margin, and with an internal cartilage. The office of these elastic bodies is to am f € @ Wl ' a" I) al NS “nl ne a i i } - lenynay i Gores t Mis oO Fig. 302.—Anatomy of a bivalve Mollusk (Mactra). a, shell-muscles; 6, ganglia; c, heart; d, liver; e, mouth; f, labial tentacles; g, foot; h, stomach ; #, intestine; 4, anus; m, mantle; 2, branchiw; 0, base of inhalent siphon; Pp, base of exhalent siphon. open the shell, when the tension of certain muscles, hereafter to be described, is relaxed. The external ligament, being placed in such a manner that when the shell is closed its elastic fibres are doubled, always tends to recover a more extended position ; whilst the internal car- tilage, which is lodged in pits within the hinge-margin, is compressed by the closing of the shell, and of course assists in Fig. 803.—Pholadomya alba. opening the valves, as soon as the pressure, under which it is confined, is reduced below its elastic force. 242 STRUCTURE OF BIVALVE SHELLS, Each valve of the shell is usually of a very oblique, broadly-conical form, running up to an obtuse point, called the wmbo or beak (Fig. 303).. This is the first formed part of the shell; and as the principal additions to the size of the valves are made by the . free margins of the mantle, it always retains its position close to the hinge. The shell — often assumes a somewhat spiral appearance, especially at this part ; and in some cases one or both valves exhibit the tendency to form a spire still more distinctly. The position of the umbones generally indicates that of the different parts of the shell in relation to those of the animal. Thus the umbones almost invariably reach the hinge- margin in front of the ligament (see Fig. 303) ; so that the portion of the shell towards which they tend is the anterior ; the opposite portion the posterior region. The latter is generally the largest. The interior of the shell is marked by impressions indicating the points of insertion of the muscles (Fig. 304). Of these, the principal are the impressions of the adductor | Fig. 304.—Right and left valves of Amphidesma, showing the impressions of the adductor muscles, the pallial line, and the pallial sinus. muscles (Fig. 302, a), which are usually two in number, one placed in the posterior, the other in the anterior part of the’ shell, the former being generally the largest. These muscles are attached to the interior of both valves, which they close by their contrac- tion. A linear impression, running. from one of these impressions to the other, and called the pallial line, marks the position of the muscular margin of the mantle. It is generally more or less parallel to the margin of the shell; but in those species which possess retractile respiratory siphons, it is more or less: indénted at its posterior portion, forming what is called the pallial sinus; and the depth of this indentation’ indicates the length of the retractile siphons. The margins of the shells often fit each other exactly, | go that when the valves are closed no space is left; but in many cases the valves: are | separated at one or both ends (Fig. 304). The shell is then said to gape. ‘ When we look at the animal inclosed in this shell, we'find that, although it cer- | tainly possesses no distinct head, .its mouth is easily discernible (Fig. 302), and'is always turned towards that part of the shell which we have described'as the front: This being the-anterior portion of the body, it follows that the mantle lobes and valves are placed upon its sides; whilst we shall find that the contrary: prevails amongst the Palliobran- | chiata, in which the valves are placed upon the upper and lower surfaces of the animal. » Of the greatest importance-to the existence of the animal is the power of. introducing a stream of water into‘the cavity of the mantle. This not only serves for: the respira- tory process, but also conveys to the creature those minute particles of organic matter | of which its food consists..In thespecies with a closed mantle two apertures:are seen at the posterior portion ; of these, one serves for the admission, the other forthe expulsion of ANATOMY OF BIVALVE MOLLUSCA. 243 the water. Ina great number of Mollusks the margins of the apertures are continued into tubes or siphons (Fig. 302), which in the burrowing species are often of great length (see Fig. 288). In some cases the two siphons are united so as to appear like a double tube. The branchie usually consist of a pair of lamin placed on each side of the body, and permeated from edge to edge by minute tubes. The walls of these tubes are composed of minutely reticulated blood-vessels ; which, according to Messrs. Alder and Hancock, pro- duce a texture resembling that of a sieve, through which the water passes into the tubes by which the gill-laminz are pertaeated. These communicate at the base of the gill with an anal chamber placed at the base of the exhalent siphon, through which the water, which has passed over the gills, and served for the purpose of respiration, is conveyed out of the body. The interior of the siphons, the surface of the gills, and that of the mantle, are all covered with cilia; and itis by the action of these microscopic organs that this important current of water is produced. But the sieve-like structure of the gill-laming, assisted by the cilia with which they are clothed, has another office to per- form besides that of respiration: they filter the water, collecting in grooves upon their surface all the minute floating particles which it contained. These are carried by the ciliary action to the edge of the branchial lamine, which is grooved, and thence conveyed to the mouth.* The mouth is furnished with one or two pair of labial tentacles (Fig. 302), but is not armed with teeth. The intestine is convoluted, and passes through the heart. The anus opens into the base of the exhalent siphon. The liver is always voluminous. The foot, when present, is usually of a tongue-like form ; it varies greatly in size, and is often wanting, especially in attached shells. In some cases it gives rise to a byssus, by which the animal fixes itself (see page 412). Most of the bivalve Mollusca are furnished with auditory vesicles, inclosing oto- lithes. They are generally placed close to the ganglion of the foot. A few also possess eye-like organs, placed round the margins of the mantle. They are sometimes very numerous. The sexes are separate; the eggs are received amongst the branchie of the parent, and retained there until the young have attained a considerable development. The Lamellibranchiata are all aquatic animals, and by far the greater part of them inhabit the sea. A few, however, are found in fresh water. Divisions.—The classification of the bivalve Mollusca, here adopted, is founded partly upon that lately given by Dr. Gray, in the Annals of Natural History (May 1854). That gentleman divides the Lamellibranchiate Mollusca into two prin- cipal groups, or orders (sub-classes, Gray), distinguished by the presence or absence of respiratory siphons. In the Asiphonata (Asiphonophora, Gray), the mantle lobes are free for the greater part of their extent, or only united at the back so as to inclose a separate exhalent aperture. In the Siphonata (Siphonophora, Gray), on the contrary, the mantle lobes are more or less united; and the respiratory orifices are both distinctly separated, and frequently produced into long siphons. Orprr I.—AsreHonata,. The Asiphonate order of bivalve Mollusca includes some of the most important of these animals; the common Oyster and the edible Mussel, as also the Pearl Oyster, belonging to it. The first is the type of the tribe Ostracea, characterized by having a * For further particulars, asto the structure and action of the branchiz in the bivalve Mollusca, the reader may refer to the admirable memoir of Messrs, Alder and Hancock, in the Annals and Mag, of Nat. Hist. for Nov., 1851. 244 THE OYS6TERS. more or less orbicular shell, of which the valves are unequal. The animal reposes on, or adheres by, the more convex of its valves. The mantle of the animal is open throughout, The foot is sometimes entirely absent; when present, it is small, and usually furnished with a byssus. There is only a single adductor muscle. The common Oyster (Ostrea edulis), which has always been a great favourite with epicures, both ancient and modern, is found in great abundance in many parts of our seas. They live in vast communities, called “ oyster banks,” each individual being attached, by its left or convex valve, to rocks, or other submarine objects. They spawn in May and June. The fry, called “spat” by the fishermen, consists of whitish gelatinous masses, in which the young Oysters may be discerned. These soon fix themselves by the shell to some object. They then grow rapidly ; but they are said to occupy four years in attaining their full growth. The “native” Oysters are obtained from artificial oyster banks, formed by transporting the fry to shallow tanks, where their food being present in great abundance, they thrive and acquire a finer flayour. Many other species of the genus Ostrea are eaten in different parts of the world. In some places Oysters grow in such abundance, attached to one another in masses, that they have been found as effectual in preventing the inroads of the sea as the coral reefs of the Pacific Islands. One of the most singular species is the Ostrea crista-galli, or Cock’s-comb Oyster (Fig. 305), inhabiting the Indian Ocean. The Oysters possess no foot; but in the singular genus Anomia, which is nearly allied to them, a small foot makes its appearance, and takes the form Fig. 805.—Cock’s-comb Oyster. of a , which passes through an aperture in one eee terete of fais aa thus attaches the creature. In the well-known and often elegant Pectens, or Scallop-shells (Fig. 306), the foot Fig. $06.—Pecten opercularis. Fig. 307.—Pearl Oyster (Meleagrina margaritifera). is distinct but small, and is sometimes furnished with a byssus. These animals are very abundant in some localities; and some of the larger species, such as the Lecten PEARL OYSTERS. 245 maximus and P, opercularis (Fig. 306) of our own shores, are regarded as excellent eating. Another species was worn by pilgrims to the Holy Land; it has received the name of Pecten Jacobeus, from its having been adopted in the middle ages as the dis- tinctive cognisance of St. James of Spain. The free edge of the mantle in the Pectens is furnished with numerous bright ocelli, The tribe of Aviculacea is rendered important by its including the Pearl Oyster amongst its members. The foot in this tribe is small, and produces a byssus, by which the animal attaches itself firmly to submarine objects. The mantle lobes are free; the shell usually oblique and somewhat triangular, with the valves unequal, and the hinge usually without teeth. Most of the shells of this tribe are pearly in the interior; and as the true pearls are merely morbid growths, they may all produce pearls of various qualities. The forma- tion of pearls is caused by the introduction of irritating substances, such as grains of sand, between the mantle and the shell. The irritation causes the animal to cover the obnoxious object with layers of pearl, which generally attach the foreign body to the interior of the shell. The Chinese produce pearls artificially by placing substances in the position just described ; and we have seen some shells, to the interior of which small metal images were attached in this manner by the pearly secretion. The Pearl Oyster (Meleagrina margaritifera, Fig. 307) furnishes the finest pearls; and the shells are also imported in vast quantities ; the inner layers, known as “ mother of pearl,’ being used for a great number of ornamental purposes. The Pearl Oyster is found in various parts of the Indian and Pacific Oceans, at a depth of about twelve fathoms, whence they are taken by divers. The most celebrated fisheries, known to the ancients, were those of the Persian Gulfand Ceylon. The um- 7 bones of the Aviculacea are furnished with dilated lateral plates called ears; these are comparatively small in the Pearl Oyster, but in the curious “ Hammer Oyster” (Malleus vulgaris, Fig. 308), an inhabitant of the Indian Ocean and the shores of Australia, these appendages attain a great length, and give the shell very much the appearance of a hammer or pickaxe. The Pixne, already referred ee to (p. 412), also belong to this tribe. Fig. 308.—Hammer Oyster (Malleus vulgaris), In the Arcacea the valves of the shell are nearly equal, usually thick, and fur. Fig. 309,—~Arca auriculata. nished with a long row of similar teeth at the hinge (Fig. 309). The adductor muscles 246 MUSSELS—FRESH-WATER MUSSELS. are two in number, and the foot is large and often furnished with a byssus, and the mantle lobes are free all round. The Frigoniacea, which are closely allied to these, have the foot long and bent, serving for leaping, and the hinge furnished with but few teeth. In the Mytilacea, of which the common Mussel (Mytilus edulis) is a well-known type, the mantle lobes are more or less united, having two siphonal apertures. The foot is furnished with a byssus, by which the animal attaches itself, and the shell is closed by two adductor muscles, of which the anterior is very small. The valves of the shell are equal, generally of an elongated oval form, covered with a thick epidermis, and usually pearly inside. The common Mussel, although greatly inferior to the Oyster, is consumed in great quantities as an article of food. The annual consumption in Edinburgh and Leith alone is calculated at 400 bushels, each of which is supposed to contain 1000 muscles. The consumption for baits is still more enormous; as many 2s between thirty and forty millions being employed in this manner in the Frith of Forth. At certain periods Mussels appear to have a deleterious effect upon persons eating them ; but the cause of this has not yet been satisfactorily made out. Most of the Mytilacea conceal themselyes by burrowing into various substances. The Lithodomé perforate solid rock, corals and shells. Some species make use of the byssus to spin themselves a sort of nest. They are generally marine; but the common Mussel may be found in fresh water; and a singular shell, the Dretssena polymorpha, which has recently been intro- duced into this country from the neighbourhood of the Black Sea, is always an inha- bitant of fresh water. The Unionacea are all inhabitants of fresh water. They have an equivalve shell, covered with a smooth epidermis, and lined with pearly matter. The margins of the mantle are free, for the greater part of their extent, united between the respiratory apertures. The foot is very large, and the adductor muscles are twoin number. Several species of this tribe are found in this country; one of the commonest being the Unio Fig. 310.—Unio Pictorum, pictorum (Fig. 810), so called from its shell having been formerly much used by painters for holding their colours. All the species furnish pearls of inferior quality ; and one species, the U. margaritiferus, an inhabitant of the mountain streams of this country, is still collected for the sake of the pearls which it contains. The American species are very numerous. Orver II.—SrpHonata. The first tribe, the Chamacea, includes some of the largest of molluscous animals; CLAM-SHELLS—COCKLES 247 the animal of the Zriducna gigas (or Clam-shell), weighing sometimes as much as twenty pounds, whilst its valves occasionally attain the enormous weight of five hundred pounds. Smaller specimens are very common as garden ornaments. Another well known species is the Hippopus maculatus (Fig. 311), which is frequently employed in the manufacture of ornamental articles. The shell in the Chamacea is very thick, usually attached, and the hinge has one or two teeth. The mantle is closed, with separate siphonal openings, but with the siphons obsolete, the foot very small; and there are two adductor muscles. In some fossil species the valves are spiral. The recent species inhabit the seas of warm climates. Fig. 811.—Hippopus maculatus, Fig. 312.—Cardium Junonez. The Cardiacea have a thick, closed, equivalve shell, with the umbones usually bent round, so that the shell, when seen from either extremity, presents a more or less cordate appearance (Fig. 312). The hinge teeth are strong, from one to three in each valve; and there are usually one or two smaller teeth on each side of the hinge. The mantle lobes are closed, the foot large and strong, and the siphons usually short, although in some species they are as long as in ‘the following tribe, and the pallial line in these cases presents a slight sinuosity. The animal possesses two adductor muscles. Many of these shells (of which the common Cockle, Cardiwm edule, is a well known example), are elegantly marked with radiating ribs, running from the umbones to the free margins; and in some cases the ribs are ornamented with spires of various and singular forms. They are generally active animals, springing to a considerable height by means of the strong, bent foot. They usually conceal themselves by burrowing in the sand or mud. Ina few species the foot forms a creeping disc. The common Cockle is eaten, and in some localities forms an important article of food; but it has but little to recommend it. The Veneracea,, forming the first tribe of the bivalve Mollusks, with elongated siphons and a distinct pallial sinus, resemble the Cardiacea in the form of the shell and general structure. The foot is usually compressed, broad, and somewhat triangular, serving principally as an instrument for burrowing. The Veneracea are distinguished from the following tribe by having the respiratory siphons separate ; at all events, for the greater part of their length. This group includes many exceedingly elegant shells, the exotic species especially being often adorned with a most charming variety of 248 BORING BIVALVES. colour. Some species are also ornamented with spines (Fig. 313). They generally f conceal themselves by burrowing, sometimes into the sand and mud of the sea-bottom, and sometimes into solid rock. The principal agent in these operations is the foot. The Pholadacea are distinguished from the preceding tribe by having the siphonal tubes united through the whole or the greater part of their length (Fig. 314). Like the Veneracea, they are all burrowing animals, and the majority select hard substances, such as rock, wood, &c., for the construction of their burrows. The shells ate usually of an elongated form, gaping at one or both ends. They are closed by two Fig. 313.—Cytherea spinosa, Fig. 314.—Panopza australis, adductor muscles. The foot is large and powerful, and the mantle i is closed. The type of the group is the genus Pholas, spe- cimens of which are common in the chalk rocks of the south of England. They are furnished with accessory plates on the back for the protection of the dorsal muscles. Another shell belonging to this tribe is the Solen, or Razor-shell, which burrows to a con- siderable depth in the sand. They are drawn from their burrows by means of a bent iron, and are said to be very good eating. One of the most cele- brated species is the Teredo navalis, or Ship-worm, an animal which at- tains a length of one or two feet, and often does immense damage by burrowing into Fig. 315.—Aspergillum vaginiferum. a, the shell complete ; 4, the perforated disc, THE PALLIOBRANCHIATE MOLLUSCA. 249 timber, In the years 1731 and 1782, it excited great alarm in Holland by boring into the piles which assist in protecting that country from the inroads of the sea. It is a soft, cylindrical, and somewhat worm-like animal, furnished with a pair of small shells at its anterior extremity. A still more singular animal, belonging to this tribe, is the Aspergillum, or Watering-pot shell (Fig. 315), which is inclosed in a calcareous tube, in the anterior part of which the two minute valves are imbedded. The anterior extremity of the tube is closed by a singular perforated disc (Fig. 315, 4), and the opposite end is usually ornamented with several ruffle-like bands. Crass TV.—PaLLioBRaNcHIATA. General Characters.—The animals of this class are distinguished from the Lamellibranchiate Mollusca by the absence of any special branchial apparatus, the respiratory function being performed by the mantle, which is traversed by numerous blood-vessels. They are also characterized by the possession of a pair of long, ciliated, and usually spiral arms, the analogues of the labial tentacles of the ordinary bivalves. The action of the cilia with which these are clothed produces a current in the water, that carries the particles of food to the mouth, which is situated close to their base. From the presence of these organs the class is often termed Brachiopoda, The valves, instead of being placed on each side of the body of the animal, are situated above and below it; so that they are called dorsal and ventral, instead of right and deft, valves. The central valve is usually larger than the dorsal, and projects beyond it at the beak, where it is generally perforated to allow the passage of a mus- cular or tendinous peduncle, by which the animal attaches itself (Fig. 316 a). In some cases the peduncle is wanting, and the shell is then fixed by the beak. The connexion of the valves is effected by a pair of teeth, springing from the ven- tral valve, and locking into corresponding cavities in the dorsal valve. There is no ligament, and the valves of the shell are opened and closed by appro- priate muscles. The arms are frequently supported upon a cal- a as careous framework or skeleton (Fig. 316 3), attached Fig. 316.—Terebratula australis. to the interior of the dorsal valve; this usually 4, shell closed, showing aperture forms two loops, springing from the neighbourhood Pe Sea Tere mine ErameeOs of the hinge. The arms appear to be extensible in some instances ; but in others they are attached to the internal framework, and only the extremity is free. The body of the animal only occupies a small portion of the cavity of the shell close to the hinge; it is inclosed within a strong membranous partition, in the centre of which the mouth is seen. The intestine is convoluted, and the liver is large and granular. All the Palliobranchiata appear to possess two hearts, each composed of an auricle and a ventricle, situated in the neighbourhood of the cesophagus; they are also furnished with a complex system of vessels, which conveys the bluod to the organs of the body, and to the mantle, where it is exposed to the influence of the water. The structure of the shell is very peculiar. It consists of flattened prismatic cells, arranged in an oblique direction as regards the surfaces of the shell; the substance of the shell is traversed by small canals, through which little processes of the outer layer of the mantle pass. These animals are all marine; they are found attached by the peduncle, which 250 THE PTEROPODA. passes ‘through the aperture in the ventral valve, suspended from rocks, corals, and other. submarine objects. The fossil species are exceedingly numerous, especially in the older strata, in some of which they are the principal representatives of the Mol- luscous type of structure, Divisions.—The greater number of the species of this class are fossil; but a good many are still found in our seas. We may distinguish three principal groups or families. In the'first, the Craniide, the ventral valve of the shell is usually adherent, without the intervention of a peduncle, and the hinge is destitute of teeth. The interior of the valves has a broad granulated border, and the disc is marked with four deep muscular impressions (Fig. 317). In the second group, the Zerebratulide, the beak of the ventral valve is pierced with a hole for the passage of the peduncle (Fig. 316), and the valves are united by a hinge. This family includes the greater part of the species, both of recent and fossil Palliobranchiata. In the third group, that of the Lingulide, the animal is attached by a peduncle ; but this, instead of passing through an aperture in one of the valves, issues from the interior of the shell between the umbones. The valves are nearly equal, horny, and Fig. 317.—Crania per- sonata. Fig. 318.—Lingula anatina. flexible ; and the peduncle is very long. The best known species, the Lingula anatina (Fig. 318), is found in the Eastern Ocean. Cuass V.—Preropopa. General Characters.—The singular little animals included in this group present many points of resemblance with those of the following class, especially in their young state. Hence several naturalists have united these animals with the Gasteropoda in a single class, denominated Cephalophora, or head-bearers ; but as the Pteropods differ greatly from the other Cephalophorous Mollusca, we have preferred leaving them as an independent group. - They are all of small size, and furnished with a pair of broad flattened fins at the sides of the head, by means of which they swim with tolerable rapidity through the open sea. They are inhabitants of the ocean, and rarely venture near the shore, except when driven from their favourite haunts by high winds; on the high sea they often abound in such profusion as to colour the surface for miles together, The claim of many of these animals to the distinction of possessing a head, is perhaps a debatable point ; for a considerable number present scarcely any traces either of eyes or tentacles on the anterior extremity of the body. In other cases, however, these organs, especially the latter, are perceptible. The ganglia are placed below the cesophagus, the supra-cesophagral ganglia being represented by a slender ring; they THE PTEROPODA—WHALE’S FOOD, 251 all possess auditory vesicles, containing otolithes. The mouth is generally unarmed, sometimes furnished with sucking tentacles, but the esophagus is muscular, and the tongue frequently armed with teeth. The intestine is convoluted, and the anus usually opens on the right side near the neck. The circulatory system is very incomplete ; the heart is composed of two cavities, and the respiratory organs are either external or inclosed within a cavity of the mantle. The foot, which is such an important organ in the following class, is here either entirely wanting, or, if present, forms only 2 little lobe between the bases of the fins. Divisions.—We distinguish two orders of Péeropoda, charac- terized by the presence or absence of a shell. Orvrr I.—Gymnosomata. The animals of this order are distinguished by the absence of a shell, and the distinct separation of the head from the body. The skin is of a firmer texture than in the following order, where it is protected by a shell. The species of the genus Clio (Fig. 319), belonging to this order, are found principally in the Arctic and Antarctic Seas, where they vecur in prodigious numbers. So great, in fact, is their abundance, that although they do not exceed an ee in inch in length, they furnish one of the principal sources of the nourishment of the gigantic Whales. They are usually of a beautiful blue or violet colour, tinged with red. Orver IJ.—Tuxcosomata. The Thecosomata are always inclosed in a shell, which is usually very delicate, and of a glassy transparency. It varies greatly in shape, its simplest form being triangular Fig. 320. Fig. 321. Fig. 322. Fig. 320.—Shell of Cleodora pyramidata. Fig. 821.—Hyalea. Fig. 322.—Eurybia Gaudichaudii. (Fig. 320), or rather pyramidal; but the basal portion is often somewhat globular, and 252 STRUCTURE OF THE GASTEROPODOUS MOLLUSCA. adorned with two or three projecting angles or spines (Fig. 321), The head is less distinctly separated from the body than in the Gymnosomate ; the foot is obsolete, and the respiratory organs are inclosed within a cavity of the mantle. Some of the most beautiful and best known species belong to the genus Hyalea (Fig. 321), so called from the glassy tex- ture of their shells, In Eurybia (Fig. 322) the animal and shell are sub-globular in shape, without points proceeding from the latter. In a few genera the shells acquire a spiral form; thus in Limacina (Fig. 323), a genus of minute Mollusks found in the Arctic and Antarctic Seas, the shell resembles that of a little Nautilus in its form ; whilst in Spérialis, it forms a little pointed spire, furnished with a minute glassy operculum. eRe Fig. $23,—Limacina rostralis. Cuass VI.—Gasreropopa. General Characters.—The most striking characteristic of the Gusteropoda con- sists in the structure of the locomotive organ. This, which is well shown in the common Snails, consists of a broad, muscular, disc-like foot, attached to the ventral surface (whence the name), upon which the animal creeps slowly along with a sort of gliding motion. This form of foot is presented by nearly all the animals referred to this class; although, in a few species, it is so greatly modified, that at the first glance it would not be taken for the same organ. The head is always distinct, usually furnished with tentacles and eyes. The opening of the mouth is placed in its lower surface ; it is often furnished with a protrusible proboscis, and armed with one or two teeth or jaws inserted in its upper part. The lower part of the mouth and cesophagus is occupied by the tongue, a long ribbon-shaped organ, sometimes longer than the whole body, covered on its upper surface with an immense number of minute silicious teeth, which are employed, with the assistance of the upper jaws, in dividing the food. The arrangement and form of these lingual teeth, as they are called, are very constant in the different groups; they have been lately employed as valuable characters in the classification of these animals. The lingual ribbon is rolled up posteriorly ; and it is supposed that it is unrolled and brought forward by degrees, in order that new teeth may take the place of those that have been abraded by use. The intestinal canal is usually simple and membranous. In some species, however, the stomach has thickened walls, furnished internally with horny ridges or teeth. The intestine winds amongst the other viscera, and the anus is situated on the right side of the anterior part of the body. The liver is very voluminous, and usually envelops the other intestines; and nearly all the Gasteropoda possess salivary glands in the neighbourhood of the mouth. Respiration is generally effected by means of branchie, placed sometimes on the surface of the body, but more commonly in a special cavity in the back of the mantle, the aperture of which is situated over the neck. The margins of this aperture are often produced into a siphon, which projects over the head of the animal; the water, after traversing the gills, passes off by a separate aperture, situated on the right side of the body: and this is also siphonste in some instances. The branchie are plumose or branched organs. As a general rule, only those of the right side are developed; but in STRUCTURE OF GASTEROPODA. 283 some cases the animals are symmetrical in this respect. In the Land-snails, and a few fresh-water Mollusks, the respiratory function is performed by a pulmonary sac, Fig. 324 —Anatomy of Turbo Pies. hollowed out in the right side of the body near the neck, and opening externally at that point by an aperture which the animal can open or close at pleasure. The heart consists of two chambers, and is generally placed in the neighbourhood of the branchiz. The blood leaves the heart by a large artery, which generally soon divides into two branches, one rumning to the head and anterior part of the body, the other to the posterior organs. On its return the blood does not appear to be confined within true veins ; it flows through the interstices of the organs, and is at last collected into particular canals, by which it is conveyed to the respiratory organs, whence it passes again to the heart. The nervous system varies greatly in development, and in the arrangement of ifs parts; but in all, the centre is formed by an esophageal ring or collar, composed of 254 SHELLS OF THE GASTEROPODA. stalks; and of a pair of auditory vesicles, containing otolithes, generally placed near the base of the tentacles, and either immediately in contact with the brain, or connected with it by a short nerve. No special organs of smell or taste have been detected in the Gasteropoda, although we may infer, from the discrimination exercised by the animals in the choice of their food, that they are not destitute of these senses. The general form of the body, in the Gasteropoda, is very characteristic of the class. From the great preponderance of one side of the body over the other, the whole acquires, during growth, a spiral form; and it is only in some naked species, and in those which have branchiw equally developed on both sides, that we find the body symmetrical. The shell with which the animals are furnished, and which, as in the other Mollusca, is secreted by the edge of the mantle, partakes of this form. It is almost always composed of a single piece (univalve), and usually forms a conical tube, twisted pirally (Fig. 289). This tube, however, is rarely perfect, the inner wall of each whorl as the convolutions of the spire are termed) being usually formed by the surface of the preceding whorl, which the animal covers with a thin coating of shelly matter. In the majority of these shells the spire takes an oblique direction, so that the shell has a pointed apex, and goes on increasing in breadth towards the lower extremity (Fig. 325). In some, however, the whorls are rolled one upon another in the same plane, producing a discoid shell (Fig. 826) ; and we meet with every possible gradation of form between the extremes of obliquity and flatness. In Scalaria, the tube of the shell is perfect, although the whorls are closely applied to each other; but in Vermetus and some others, the shell forms a simple more or less contorted tube. The same thing occurs in monstrous varieties of regularly spiral shells; and a few species which inhabit « spiral shell until they attain a certain size, afterwards add to it by form- ing a straight tube of the diameter of the aperture. As the right side of the Gastero- poda is almost always the largest, the convexity of the Fig. 325.—-Pirena. Fig. 326.—Ampullaria. spire is, of course, turned in this direction, and the shells follow the same rule, These normal shells are called dextral; in a few species, however, and in some monstrosities of dextral species, the spire turns in the opposite direction: these are called sinistral shells. In the truly spiral shells, the progressive winding of the tube produces a more or less distinct central axis, or pillar, called the columella, which runs from the base to the apex of the shell, and forms the inner margin of the aperture from which the animal protrudes when in motion. This pillar is usually hollow, and terminates at the base of the shell by a small opening, called the umbilicus. The margins of the aperture are called the lips; the outer lip (labrum) forms the convexity of the shell; the inner lip (Jabiwm) is usually formed by the columella, and is hence denominated the columellar lip. ‘The two lips are sometimes con- SHELLS AND OPERCULA OF GASTEROPODA. 255 tinuous, but more commonly separated by a notch, which is often, in the siphonated species, produced into a canal. The junction of the outer lip with the preceding whorl is also frequently marked with a notch, for the reception of the excurrent siphon. The outer lip is frequently reflexed, or furnished with spines or tubercles; its margin is sometimes turned inwards, and both lips are not unfrequently furnished with teeth or other projections on the inside, Tho last whorl of the shell is called the body whorl, from its receiving the body of the animal when retracted. The remaining whorls form the spire; and the impressed line which separates the whorls is the suture, A great number of the Gasteropoda close the aperture of their shell with a small horny or calcarcous plate, called the operculum, which is attached to the hinder part of the foot, and is drawn into the mouth of the shell by the contraction of the animal. It is seen in the young animal whilst still in the egg; and this forms the nucleus of all subsequent growth. It varies greatly in its form, being sometimes composed of con- centric layers, sometimes spiral, sometimes oval or sub-circular, with the nucleus placed a@ Fig. 328.—Forms of opercula, u, spiral (Turbo) ; b, lamellar, with marginal nucleus (Murez) ; ¢, appendiculate (Werita). at one side, or at the extremity; sometimes irregular in form, or furnished with appendages (see Fig. 328). Most of the Gasteropoda are strictly oviparous animals; but a few are ovo-viviparous ; the eggs being retained in the oviducts until the exclusion of the young, and even until these have attained a considerable development. The sexes are generally on separate individuals, but a considerable number are hermaphrodites ; these, however, require mutual impregnation to fertilize the ova. The orifices of the generative organs are usually situated on the right side of the body, in the neighbourhood of the anus. The mode in which the ova are deposited, and their arrangement, have already been briefly referred to (see page 416). The young Mollusk is always provided with a shell whilst in the egg; this, however, is cast off, soon after hatching, by most of the naked species. The young of the air-breathing species resemble their parents in every respect except size; but those of the branchiferous species are furnished with a pair of fin-like expan- sions, resembling those of the Pteropoda, by means of which they swim freely through the water. Divisions.—The Gasteropoda may be divided into two sub-classes, the Heteropoda and the Gasteropoda proper ; the former including only a single order, whilst the latter are divided into two great orders, called Branchifera and Pulmonifera, from the nature of their respective respiratory organs. Svup-cLass AND OrpER J.—HzETERopopa. General Characters.—The animals of this group, the Nucleobranchiata of some authors, are all inhabitants of the ocean, where they swim about rapidly, the whole structure of their bodies being adapted particularly to this mode of existence. The foot, when present, is converted into a broad, flattened, fin-like organ (Fig. 328), furnished 256 THE HETEROPODOUS MOLLUSCA. with a small sucker, by which the animals adhere to floating sea-weeds. The whole body is usually compressed ; and it is by the fin-like action of the tail that the crea- tures swim, The head is distinct, and usually furnished with a pair of tentacles and eyes; the mouth is gene- rally furnished with along proboscis. In the typical forms, the intestines, with the heart and generative organs, are collected into a mass on the back of the animal; this is inclosed in a shell, round the interior of which the comb-like Fig. 329.—Carinaria. ee ae oe of a transparent gelatinous texture; they swim with the back downwards, and appear to feed upon minute marine animals. Divisions.—In the Atlantide (Fig. 330), the shell is spiral, and large enough to contain the whole animal when contracted ; and the gills are contained in a regular branchial cavity. They often possess a delicate operculum. The Firolide are either entirely naked, or furnished with a small, conical, keeled shell, which incloses the intestinal nucleus (Fig. 329). The Firole are destitute of a shell. The Sagittide form a third small family, whose title to Sousa 4 this position is, however, by no means certain. They are Fig. 330.—Atlanta Kerandreni, little, fish-like animals, furnished with one or two pairs of fin-like organs on the body, and with a broad and usually bilobed caudal fin (Fig. 331). The head is distinct, and the mouth armed with several Fig. 331.—Sagitta. pairs of lateral hook-like jaws. They are of small size, and swim with great rapidity. They have hitherto been found principally in the North Sea and in the Mediterranean. The name of Sagitta, given to these animals, refers to their arrow-like appearance. Sus-crass II].—GastTeRoPopA PROPER. In the true Gasteropoda, which exhibit the structure of the foot, and the general structure of the body, already described as characteristic of the class, we distinguish two great orders,—the Branchifera, furnished with gills, and the Pulmonifera, which respire by pulmonary sacs. Besides this important difference in structure, the branchi- ferous Gasteropoda pass through a distinct larval state ; usually issuing’ from the egg in a very different form from that they are ultimately to assume, as already described at page 439. The pulmoniferous species undergo no metamorphosis. NUDIBRANCHIATA MOLLUSCA. 257 Orprr IJ.—BrancuIFrera. The general characters of this group are given above. It is divided into two sub- orders, characterized by the position of the branchiz. Sup-orper I,—OpisTHoBRANCHIATA, General Characters.—In the animals forming this sub-order, the branchie are not generally inclosed within a cavity of the mantle, but more or less exposed on the back or sides of the animal, generally towards the posterior portion; and the auricle of the heart, which receives the blood from the gills, is placed behind the ventricle. All these animals are hermaphrodites ; few of them are inclosed in a shell; some have an internal shell, but the majority are naked. Divisions.— This sub-order includes two principal groups. In the first, the Tectibranchiata, the animals are generally furnished with a shell, and the branchie are covered either by the shell or the mantle. The Bullide, or bubble-shells, have a delicate cylindrical or globose shell, which is more or less inclosed within the mantle; the head is flat, with broad tentacular lobes; the foot is large, and often furnished with lateral lobes, which the animal is said to use in swimming; the gill is single, placed on the right side of the back, and concealed by the shell. They are carnivorous in their habits, and are furnished with a gizzard, in the walls of which several calcareous plates are imbedded. In the Aplysiade the shell is either absent or rudimentary. The animal is slug-like in its form; the head is distinct, and furnished with tentacles and eyes, and the sides of the mantle are very large, and reflected upwards, so as to cover the back and branchial plume. The tentacles are turned back like ears; whence the name of sea-hares com- monly applied to these animals. They live upon sea-weeds, from which they derive their principal nourishment, although they also feed upon animal substances. When alarmed or molested, they emit a violet or reddish fluid from the mantle, which was long supposed to be of a poisonous nature; although, according to recent observations, it is quite harmless, : The Pleurobranchide are also usually furnished with a shell, which, however, is often concealed by the mantle; the foot is usually very large, and the feather-like gill is concealed between a fold of the mantle and the foot. The shell is sometimes limpet- like in its shape; one of them, inhabiting the Indian and Chinese Seas, is commonly known as the Umbrella shell. The Phyllidide are nearly allied to these, but have no shell, and the branchie are placed on both sides of the body, beneath a fold of the mantle. In the second great group, the Nudibranchiata, the animals are shell-less, and the branchie are placed on the back or along the sides of the body, without any covering. These animals are also hermaphrodites. These elegant and delicate little creatures, which are often adorned with the most pleasing colours, are generally found near the coasts, crawling upon sea-weeds. They are very carnivorous in their habits, feeding prin- cipally upon zoophytes. A most admirable monograph of the British species, by Messrs, Alder and Hancock, has been published by the Ray Society. The Nudibranchiate Mollusks are distributed into three families. In the Holidide, the branchiw are arranged along each side of the back, which is also furnished with peculiar appendages, into which processes of the liver and stomach pass, and the tentacles are not retractile. 258 TOOTH-SHELLS. These animals generally resemble little slugs, with tufts of filaments along the sides Fig. 332.—Eolis. (Fig. 332); but some species present a very singular appearance, having the body very slender, and the gill tufts supported at the extremities of lateral foot- stalks (Fig. 333). The Tritoniide often resemble the preceding in ap- pearance, but they are destitute of the coecal prolongations of the in- testines, and have the tentacles sheathed and retractile. The Doride are generally of a broader form and larger size than the animals of the pre- ceding families, from which they are distinguished by having the branchie placed in a circle on the back, generally towards the hinder parts. The branchie are elegant, arborescent organs; the foot is much smaller than the mantle. Fig. 333.—Glaucus Fig. 334,—Doris. Forsteri. Sun-orpEer IT.—ProsoBRaNcHiATa. General Characters.—This sub-order is far more extensive than the preceding, and the characters by which it is circumscribed are far more distinct, All the animals referred to this group possess a shell, within which they can usually retract themselves entirely at pleasure, and this is almost always of a spiral form; the mantle forms an arched chamber, immediately over the neck, in which the branchiz are situated, together with the orifices of the alimentary and generative organs; and, as a necessary consequence of this anterior position of the gills, the blood flows back towards the heart, and the auricle of the latter organ is placed in front of the ventricle. The sexes are almost always distinct, and nearly all the species are marine. _ Divisions.—The Prosobranchiata may be divided into three principal groups. In the first, the Cirrhobranchiata, including only a single family, the Dentaliide, or tooth-shells, the animal is so anomalous in its form that it was placed by Cuvier and other observers amongst the Annelides, The _ ° shell is tubular, gradually tapering from one end to the te wn the pa other, and gently curved throughout its whole length, so as rior part of the mantle to have the appearance of a miniature Elephant’s tusk (Fig. feted Geant, with 336) ; hence the commonest species (Dentalium entalis) is popu- _ the head between them ;, larly denominated the Elephant’s tooth. It has an aperture By ROSE SADE STI: at each end, that at the narrower extremity being very small. The animal (Fig. 335) in- habiting this shell is of a cylindrical form, inclosed in a sac-like mantle, from the anterior extremity of which the tip of the foot is protruded. The head is situated at the middle LIMPITS—CHITONS. 259 of the upper part of the body, and on each side of it are the symmetrical cirrus-like branchiw. The anus opens at the posterior part of the body. The Dentaliide are Fig. 336.—Dentalium, with foot protruded. carnivorous, feeding upon minute marine animals. They live in sand or mud, in which they bury themselves by means of the foot. A good many species are known, of which several inhabit the British seas. ‘ In the Cyclobranchiata the branchie are ususually placed all round the body, in the space between the margin of the foot and the mantle, although in some species they are situated in a cavity over the neck. The Patellide, or Limpets, may be considered as the types of this group; they are inclosed in a conical shell (Fig. 337), the interior of Fig. 337.—Limpet (Patella). Fig. 338.—Chiton. which is entirely occupied by the animal; the foot is very large, and by means of it the Limpet fixes its little residence so firmly to rocks and other objects, that it is not to be detached without great difficulty. They feed on vegetable matters, and occur in great abundance in many situations; they are often used as food by the poorer classes, and are also collected in great numbers for baits. The Chitonide resemble the Limpets in the situation of their branchie ; but these organs only run round the posterior part of the body. The shell in the Chitons (Fig. 338) is composed of eight calcareous plates, overlapping one another at the edges, and united by a strong leathery mantie, which forms a border all round the shell. They adhere to rocks like the Limpets. Our British species are all small; but many tropical species attain a considerable size, and of these the muscular foot is often eaten by the natives of the countries in which they occur. The Pectinibranchiata exhibit the characters of the sub-order in their greatest per- fection; the branchie are usually single, and inclosed in a cavity over the neck of the animal, The Calyptreide have a Limpet-like shell, which is usually somewhat spiral at the apex, and frequently furnished with a-sort of shelf of shelly matter in the interior. They appear to pass a perfectly sedentary life, attached to stones and rocks, to the irregularities in the surface of which their shells usually adapt themselves. In the Haliotide the spiral conformation of the shell goes a little further, and there is a per- foration or notch for the passage of the anal siphon at the posterior margin. In the 260 SEA SNAILS. common Ear-shells these perforations are arranged in a row along the back of the shell The animal ‘has a short muzzle and two branchial plumes.. The Fissurellida, which are nearly allied to these, have a shell closely resembling that of the Limpet in form, but perforated at the apex for the passage of the anal current. The family Janthinide contains a few species of oceanic Mollusca, which possess a shell almost exactly resembling that of a common Land-snail; it is of a delicate texture, deep violet at the base, and with the spire white. The animal has two branchial plumes, a muzzle-shaped head, with tentacles, but without eyes, and a very small foot, which, however, secretes a remarkable structure, considered to be the analogue of the operculum, It consists of a large raft, composed of numerous horny vesicles filled with air, to the under surface of which the animal attaches its eggs, and thus floats about at the surface of the water, being supported by the buoyancy of the float. The Ianthinide are carnivorous animals; they often occur in vast numbers in the Atlantic, and are sometimes driven by stress of weather upon the southern shores of our island. In the Naticide the shell, which is globular, composed of few whorls, and opening with an entire aperture, is partially inclosed in the mantle; the foot is very large, furnished in front with a broad lobe, which conceals the head, and behind which the tentacles rise. The mouth has a long retractile proboscis, and the animals are carni- yorous in their habits. They are all marine. In the Zurbinide, the shell is more or less conical or pyramidal, generally with a distinct umbilicus (Fig. 289), and the aperture is closed by a spiral operculum (Fig. 328 a). The animal has a short muzzle ; the tentacles are long and slender, with the eyes supported upon short footstalks at their bases; the sides are frequently furnished with tentacular cirri, and the branchial plume is single. The shells arg generally pearly in the interior. These animals are very numerous, and widely aidhibated ; they are all marine, and feed on vegetable substances. The pyramidal Trochz, or top-shells, are very common on all our coasts. Nearly allied to the Turbinide are the Neritide, a small family of Mollusks, fur- nished with a thick and somewhat globose shell, with a small spire (Fig. 339), and the margins of the aperture turned in and toothed. The eolumellar lip has a pro- jecting plate, behind which the inner walls of the spire are removed; so that the inte- rior of the shell presents a simple cavity. The animals have a broad foot, a broad muzzle, and very long tentacles, at the base of which the eyes are placed upon short footstalks. Most of them are marine; but one genus, the Neritina, inhabits fresh . water. The mouth of the shell is closed by an appendiculate operculum (Fig. 328 a). In the large family of Turritellide, the shell exhibits a great variety of form, being sometimes semi-globular, with a short spire, or even discoid, and sometimes much elongated and tapering gradually to the apex. The aperture is entire, and closed by an eperculum, which is usually horny and spiral. The animal has long slender tentacles, which usually bear the eyes on their outer surface, at or near the base. The head is generally short and broad, without a proboscis, and the rows of teeth on the lingual ribbon are arranged in rows of seven. Fig. 339.—Nerita polita. CLAW SHELLS. 261 Most of these animals are marine, but several genera are found in fresh water; of | these the Paludina vwipara, which is common in Britain, is, as its name implies, vivi-’ parous, the young being hatched and retained within the oviduct until they have attained a considerable development. The Ampullarie are furnished with a long siphon. They also inhabit fresh waters, and often possess beautiful shells (Fig. 326). The common Periwinkle (Littorina littorea) also belongs to this family. In the genus Vermetus and its allies, the whorls of the spire are separated for the greater part of their length, giving the shell the appearance of a twisted tube; from this circum- stance they were referred to the Annelides before the animal was known. The Cerithiide have an elongated spiral shell, with the outer margin of the aper- ture more or less dilated, and the base produced into a slight siphonal canal (Fig. 340). The aperture is closed by a horny, spiral operculum. The animal has a short muzzle, and long, slender tentacles, having the eyes on the outside, at a short distance from the base. In the Aporrhais pes pelecani, the margin of the aperture is much dilated, and the siphonal canal very distinct, forming a transition to the next family. : The animals of the following families are all carnivorous in their habits ; they have spiral shells, with the aperture notched, or produced into a canal at the anterior extre- mity. They are all furnished with a retractile proboscis. Fig. 340.—Cerithium granulosum. Fig. 341.—Strombus, The Strombide have the outer lip of the shell much expanded, and notched in the neighbourhood of the siphonal canal- the operculum is elongated, and toothed along the outer margin. The foot is narrow, and ill adapted for creeping; but the animals are active, and leap well. The proboscis is long and thick; the eyes large, and supported upon long stout footstalks, from the sides of which the short tentacles take their rise. The operculum is borne upon a curious process of the foot (see Fig. 341). The dilated margin of the aperture is often singularly toothed, or furnished with large . Spines, as in the well-known Scorpion-shells (Pteroceras). The Strombide feed princi- pally upon carrion, and many of them are of large size. 262 WHELKS—CONES. In the vast family of Muricide, the outer margin of the shell is not notched near the canal ; the canal itself is sometimes produced in a line with the axis of the shell, and sometimes reflexed. The animal has a long proboscis, with which it bores through the shells of other Mol/usca, shortish tentacles, which sometimes bear the eyes, and a broad foot adapted for crawling. The Muricide are all marine, predatory animals. Their shells are generally ornamented with spines (Fig. 292), which often assume the most singular forms. Many of the exotic species are of exceedingly beautiful colours, and some are of considerable value. The large Helmet-shells (Cassis) are much employed in the manufacture of cameos; some of the species, such as the Whelks (Buccinum), are eaten ; and it is supposed that the celebrated purple dye of the ancients was obtained from some Mollusk belonging to this family. In the nearly-allied family, Volutide, which also contains many elegantly-marked shells (Fig. 342), the outer margin of the aperture is not reflexed, the canal is reduced to a notch, and the inner lip is plaited. The shell is more or less enveloped in the mantle; the foot is broad, and bears no operculum. These animals resemble the Muricide in their habits; they are found principally in the tropical seas. The beautiful animals, forming the family Conde, are nearly allied to the preceding. Their shells are of a reversed eonical form, becoming broader towards the apex, the spire being often quite flat ; the aperture is long and narrow, and the operculum is very small. Fig. 342.—Voluta undulata. Fig. 844.—Adult Cypraea. The teeth on the lingual ribbon are arranged in pairs. These are exceedingly predatory animals, which are said to bite severely when touched. Many of the shell sare exceed COWRIES—SNAILS. 263° ingly elegant, and some of the rare species have realised almost fabulous prices. Inthe Cypreide, one species of which, the Cyprea tigris (Fig. 343), is so common that it must be familiar to every one, the shell presents a very different appearance at different ages. In the young state it is distinctly spiral, with a plain outer lip; but as it increases in age, the whorls are brought into the same plane, and in course of time the spire is usually entirely concealed. At the same time the outer lip becomes thickened, turned in and dentated, producing the appearance shown at Fig. 344. The animal greatly resembles that of the Volutidae; but the mantle usually covers nearly the whole of the shell, and deposits upon its surface the enamel which contributes so much to the beau- tiful appearance of these shells. The Cypreide are found in great abundance in the seas of the tropical parts of the world; many of them are much sought after by collectors, and several of the smaller species are applied to ornamental purposes by the natives of the countries where they are found. The Cyprea moneta, or Money-cowry, stands in lieu of coin with the negroes of Western Africa ; and other species are made use of in the same way amongst uncivilized people. Oxper II].—Putmonirera. The Pu!moniferous, or air-breathing Mollusca, including the land snails and their allies, are distinguished, as we have already stated, not only by the structure of their respiratory organs, but also by their young being hatched in a form closely resembling that of the parents. Divisions.—They are divided into two great groups, the operculated and the tnoperculated Pulmonifera. The operculated species form only a single family, the Cyclostomide, composed of snail-like animals, with thin spiral shells, of which the margins are usually reflexed allround. They have only two tentacles, with the eyes inserted in their basal portion. The Cyclostomide, also, differ from the majority of the Pulmonifera, in being unisexual. Of the inoperculated section, the common land snails may be taken as the type. They form the family Helicide, characterized by their ample external shell, within which the animal can retract itself entirely, and by their possession of four tentacles, upon the summits of the longest of which the eyes are situated. Thisis a very extensive family of herbivorous Mollusks, which are found in great abundance in all parts of the world. The Limacide, or Slugs, resemble the snails in the form of the body, in the number and structure of the tentacles, and in their habits; but their shell is very small or rudi- mentary, and usually concealed in the interior of the mantle. The little family Oncidiide consists of small, slug-like animals (Fig. 345), covered with a leathery q j mantle, but quite destitute of a shell. The head is furnished with either two or four tentacles. They are generally found in marshy place upon aquatic plants; but some of them inhabit the sea-coast, within reach of the waves. They are mostly inhabitants of warm climates. In the Limneide, or Pond Snails (Fig. 7), the shell is ample ; but the,tentacles are only two in number, with the eyes sessile near their bases. The shell is thin and horny, with the aperture simple ; whilst in the Auriculide, which frequently inhabit the sea-shore, the Fig, 345. —Onei- shell is much stronger, with the margins of the aperture thickened dium, and notched. In these the tentacles are also two; but the eyes are situated on the head. 264 STRUCTURE OF THE CEPHALOPODA. Crass VII.—Crruaropopa. General Characters.—In thcir structure and habits the animals forming this class present a considerable-advance upon the other Mol/usca—an advance so great, in fact, that by several zoologists they have been regarded as forming a distinct primary division of the animal kingdom, ‘This view is supported by the presence of a rudi- mentary cartilaginous cephalic skeleton in these animals, and also by a peculiarity in the development of the embryo, which is not effected as in the other Mollusca. Their most striking character is afforded by the locomotive organs, which consist of a circle of tentacles, or arms, arranged round the head, and furnished on their inner surface with numerous sucking-cups, which enable the animal to take a firm grasp of any object (Fig. 286). By means of these arms the Cephalopoda creep along the bottom of the sea with the head and mouth downwards; they also serve for the capture of prey—these animals being very carnivorous in their habits. They also swim rapidly by the expulsion of the water from the branchial chamber. The branchie in the Cephalopoda are placed on both sides of the body, which is short, thick, symmetrical, and not rolled in a spiral form. The shell is often spiral; but the portion inhabited by the animal is divided from the rest by a transverse partition; so that, by the successive growth of the animal, the shell acquires a chambered structure. The body is inclosed in a sac-like mantle, which is open in front on the ventral surface for the passage of water into the branchial chamber ; this is again expelled, by muscular action, through a separate siphon, placed a little in advance of the incurrent orifice. The gills (Fig. 287) arc plumose organs, formed of numerous laminw attached to the sides of a central stalk, through which the blood passes to them. At the base of each gill is a pulsating cavity, which drives the blood through these organs; and this fluid is received in another cavity on its return from the gills, and by the contraction of this is driven into the central heart. The mouth is armed with a pair of powerful horny jaws, presenting a considerable resemblance to the oenk of a parrot, within which is a fleshy tongue, part of which is covered with recurved spines. The intestines are convoluted, and the anus opens into the exhalent siphon; the liver and salivary glands are very large. In the development of the nervous system (Fig. 6), the Cephalopoda exhibit a great advance upon the other Mollusca, The cephalic portion is very large, and composed of several ganglia, closely united together ; the oesophagus, as usual, passes through the ring formed by the subcesophageal ganglia. The brain is surrounded by a cartilaginous ring, the first indication of an internal skeleton, which also usually gives off processes for the support ofthe eyes. The latter organs are of large size, placed on the sides of | the head, and resemble those of fishes in many respects. ‘The auditory vesicles, with their otolithes, are also imbedded in the cartilaginous ring.. Two small cavities, in the neighbourhood of the eyes, are supposed to be organs of smell; and, as we have already seen that the tongue is a fleshy organ, it appears probable that the Cephalopoda possess all the senses in a state of considerable perfection. The skin is generally thick and leathery, but covered with a delicate cuticle, in which numerous cells of different colours (chromatophora) are inclosed. The- animal possesses the power of altering the position of these cells; so that the tint of the skin is constantly changing; this effect continues even for some hours after death, and furnishes the inhabitants of those countries, where the Cuttle-fishes are eaten, an excg]- lent means of judging of the freshness of the fishmonger’s commodities. STRUCTURE AND DEVELOPMENT OF THE CEPHALOPODA. 265 A peculiar organ possessed by many Cephalopoda is the ink-bag, a small pyriform sac inclosed in the visceral cavity, which secretes a dark brown fluid ; it communicates by a duct with the exhalent siphon, and through this its contents may be discharged into the water, which is thus discolourcd for a considerable extent. When attacked, the animals constantly employ this artifice to facilitate their escape, the inky secretion producing a thick cloud in the water, under cover of which the Cuttle-fish rapidly retreats to a safe distance from the object which has excited his apprehensions. ‘his fluid was formerly employed in the arts, and gives its name to the well-known colour denominated sepia (Sepia, a Cuttle fish) ; but a considerable portion, if not the whole, of the article sold under this name is now derived from other sources. It is remarkable that the ink-bags of Cuttle fishes are often found preserved in a fossil state, although the remainder of the animal is reduced to an almost unrecognizable form. The Cephalopoda are all unisexual animals; their ova are usually of large size. The sexes are generally very similar in appearance; but in some species males of a very peculiar form have been observed, which, at their first disco- very, were regarded as parasitic worms, and described under the generic name of Hectocotylus. They are worm-like creatures, furnished with a double row of sucking-cups, which give them a close resem- “Dlance to a detached arm of a perfect animal. On the surface opposite to these suckers they are provided with filamentous branchie in some species; but these are wanting in others. They are generally _ found adhering to the siphon of the female, but sometimes attach Fig. Sate themselves to the arms of their partner, upon which they creep about _ with yeik sac. rapidly by the assistance of their suckers.* We have already stated that a difference exists between the Cephalopoda and the other Mollusca in the mode of development of the embryo. In the latter, the entire yelk becomes converted into an embryo; in the Cephalopoda, on the contrary, the first rudiments of the young animal make their appearance at a particular portion of the surface of the yclk, so that the development of the embryo takes place exterior to this body, which gradually disappears as the young Cephalopod approaches maturity. Divisions.—The Cephalopoda are divided into two orders, characterised by the number of their branchial plumes, of which there are either one or two on each side. Orper I.—TErRABRANCHIATA, General Characters,—This order, which includes a vast number of fossil forms (Ammonites, &c.), is represented in our seas only by the Nautili, of which a few species still inhabit the seas of tropical regions. They are all inclosed in a shell, divided by transverse partitions into a number of chambers (Fig. 347), gradually increasing in size towards the mouth of the shell, where a considerable space is left for the habitation of the animal. As the latter grows, and increases the size of its shell in the usual manner, by additions to the mouth, it, at the same time, cuts off a portion of the space it formerly occupied by a fresh partition; thus adding another chamber to its residence. The partitions are traversed, either in the centre or close to the wall of the shell, by apertures, through which passes a vascular siphuncle, commu- nicating with the chamber in which the heart lies, The remainder of the chambers is filled with air. In the recent Neutili, and in many fossil species, more or less allied to + According to the observations of H. Miiller, the Hectocotylus of the Argonaut is developed in the place of one of the arms of the male. 266 THE NAUTILUS. ‘hese, the partitions are of a plain, cup-like form, with the concavity directed towards the mouth of the shell; but in many fossil forms (such as the Ammonites, Fig. 348, and their allies) the partitions are folded towards the edges into various singular forms; and as the thin shells of these creatures are often entirely abraded, so that the fossil is merely a cast of the interior, these patterns are frequently very distinctly visible, and their varia- tions then afford excellent characters for the discrimination of the species. The animal inhabiting this curious and beautiful shell was long almost unknown, and our knowledge of its structure has only been very recently obtained. It is completely retractile within the mantle; its head is sur- Fig. 347.—Section of Nautilus, with the animal. rounded by a great number of tenta- Puen renee cles, which are retractile within sheathes; and instead of being furnished, as in the ordinary Cephalopoda, with sucking- cups, are slighly annulated (Fig. 8347 2). The branchie are four in number, placed two on each side of the body. The animal of the Nautilus, the only one with which we can now be acquainted, usually creeps, mouth downwards, along the bottom of the sea; it is sometimes, how- Fig. 348.—Ammonites nodosus, ever, dislodged from this situation by storms, when it has been seen to float on the surface in a reversed position, with the tentacles expanded. An opinion has very AMMONITES. e 267 generally prevailed that this was, in reality, the favourite position of the Nautilus, and that its chambered shell was intended to give it the buoyancy necessary for this purpose. This, however, is contradicted by observation ; and it appears that the empty chambers only serve to approximate the specific gravity of the animal as nearly as possible to that of the medium it inhabits. Divisions.—The Tvtrabranchiate Cephalopoda form two families,—the Nautilide and the Ammonitide, The former, which includes the only living representatives of the order, is distinguished by the simple structure of the partitions of the shell, and by the central position of the siphuncle, The shell is sometimes spiral, as in the Nautilus (Fig. 347); but then always consists of but few turns; sometimes perfectly straight (Orthoceras), or merely twisted at the apex ina crosier-like form (Lituites, Fig. 349). In the Ammonitide the partitions are bent or folded into various forms, and the siphuncle runs along the outer wall of the shell, which is usually spiral, and composed of numerous whorls. Of the genus Ammonites (Fig. 348), upwards of five hundred species are known, and many of these are of great size. In some cases, the shells, although spirally twisted, have the whorls separate; in Fig. 350.—Turrilites. Breynii. other instances (Baculites) they are perfectly straight. The genus Ptychoceras has a straight shell, doubled in the middle, with the two parts closely applied ; whilst in Turrilites (Fig. 350), we have a regular screw-like shell, resembling that of Turritella, amongst the Gasteropoda. Onper IT.—Drprancurata, General Characters.—This order, which includes a great number of living as weli as fossil species, is distinguished from the preceding not only by the possession of only two branchie, but also by the general structure of the body, which is adapted especially for swimming rapidiy through the water, al- though the animals are able to creep, with the head down- wards, upon the bottom of the sea. The shell is almost always internal, frequently rudi- mentary; and when external is never chambered. The arms are only eight or ten in number, furnished with sucking dises; and the body is usually provided with a pair of fins. Divisions.—The Dibranchiata are divided into two principal sections, characterized by the number of their arms. The Decapoda have ten of these organs, of which two (called tentacles) are usually Fig. 351 —Spirula_Peronii, with its shell. 268 CUTTLE FISHES. much longer than their fellows, retractile, of a cylindrical form, flattened and provided with suckers at the extremity. Of these, the Spiraide appear to make the nearest approach to the animals of the preceding order, as they are furnished with a chambered shell (Fig. 351), which, however, is almost entirely concealed within the body. ‘hese animals inhabit the seas of the warm parts of the world, apparently in great abundance, as their shells are cast upon the shore in profusion; nevertheless the structure and habits of the animal are almost unknown. In the remaining families the shell is entirely inclosedl, In the Sepiide it forms a broad calcareous plate, terminating in an imperfectly chambered apex. The shell of one species, the Sepia officinalis, is the well-known Cuttle-fish bone of the shops; it was formerly employed in medicine, but is now principally used as pounce. The bodies of these animals are usually of a somewhat ovate form, and the fins run along the whole length of the sides of the body (Fig. 352). In the Loligide (Culamaries or Sguids), which are nearly allied to the preceding, the body is almost always of an elongated form, and the fins are broad, and confined to the Fig. 353. Pen of Ony- choteuthis. Fig. 352.—Sepia Hieredda, Fig. 354.— Chiroteuthis Bonellii. apex of the body. The shell is represented by a horny plate (Fig. 353), which, from its consisting of a central shaft and two lateral expansions, has received the name of the pen. These animals are exceedingly active, and swim well. Their arms are frequently of considerable length, the tentacular arms especially, which in the genus Chiroteuthis (Fig. 354) attain no lesa than six times the length of the body. They are found com- monly in all seas. The common British species (Loligo vulgaris) is often thrown upon the beach after high winds; and this and other species are much employed as baits in various fisheries. BELEMNITES—OCTOPODS. 269 In the fossil family Belemnitida, the structure of the internal shell is far more complicated. In its general form (Fig. 355) it resembles the pen of the Calamaries, forming a broad corneous plate, which terminates posteriorly in a regularly chambered conical shell (the phragmocone), which is furnished £f) with a distinct siphuncle. At its lower extremity, the phragmocone is Y/fl inserted into the base of a firm, solid, cylindrical sheath, which evidently (iy serves to protect the phragmocone from injury when swimming backwards. From this provision it has been concluded that the Belemnites lived in the neighbourhood of the shores, where they would be in constant danger of coming into collision with fixed objects. From impressions of these soft animals, which have been preserved in some fine grained strata, it appears that they closely resembled the Loligide in form; their arms were furnished with rows of sharp hooks. The Octopoda are distinguished by the possession of only eight arms, without the retractile tentacular arms of the true Cuttle-fishes; they are but rarely furnished with fins. The Octopodide are naked animals, with scarcely any trace even of an internal shell. The arms are united at the base by a broad membrane, which appears to be of great service to the ' animals in swimming. They are exceedingly active and voracious, preying Fig. 355. with avidity upon Crustacea and fishes, To this family belongs the common Belemnite. “poulpe” of the Mediterranean (Fig. 356), which is a regular article of food in the south of Europe. The Octopodide not unfrequently attain a considerable size, M. Sander Rang mentions one, which he saw, of the size of a large cask. The tales of navigators attribute still larger dimensions to some of these animals, which have been said to possess arms of thirty, or even sixty, feet in length. From the same authorities it would appear that these giants have a mischievous and very disagreeable Fig. 356.—Poulpe (Octopus vulgaris). propensity for embracing any passing boat, with their enormous arms, and dragging it down into the deep. To ridicule this idea, Denys.de Montfort has represented one of 270 THE ARGONAUT, these monsters in the act of ingulfing a three-master, an arm being twisted roun each of the masts, and reaching nearly to the top! The Kraken of Scandinavian superstition appears to be a still more exaggerated representation of one of these animals. Its existence was gravely alleged by Pontoppidan as the cause of the occa- sional disappearance of islands! The Argonautide are furnished with an external shell, the texture of which has obtained for it the name of the Paper Nautilus. These animals are remarkable for having two of the arms dilated into broad plates, by the expansion of which, when floating at the surface with its shell reversed, the ancients, and many of the moderns, have supposed that the Argonaut sailed gently along in his fragile boat, on the surface of the summer sea. This notion, consecrated as it is by poetical usage, proves to be entirely incorrect. The Argonaut uses its dilated arms to grasp its shell, whilst swimming backwards, like the other Cephalopods, by the expulsion of water from its branchial chamber (Fig. 357) ; these organs also appear to secrete the shell, which is not attached to the body of the animal, The male Argonaut is not provided with a shell. Fig. 357.—Argonauta Argo swimming. We have thus traced, as fully as our space would permit, the leading characteristics of the vast and varied series of Invertebrate animals, Throughout the classification adopted we have endeavoured to represent, as nearly as possible, the generally- received views upon this branch of Natural History, deeming that in a work of this nature, intended for popular instruction, it would be more serviceable to furnish the reader with an intelligible account of the views generally admitted, than to run the risk of communicating erroneous notions by adopting the new and imperfectly deve- loped views which must necessarily prevail during the transition state of any depart- ment of science. For this reason we have retained the division of Radiated animals, although, as we have already stated (page 270), the views of naturalists regarding these creatures are in a very unsettled state. The study of these animals is attended with great difficulties. The very nature of many of them is but little known; and we cannot expect that any satisfactory results will be attained until our knowledge of their structure, and especially of their development, shall have made a vast advance. As it is, however, the classification of the lower animals has made a great advance of late years. The division Radiata of Cuvier included a heterogeneous assemblage of animals; and, in fact, with that Zoologist and his successors, served as a repository for anything that could not easily be placed elsewhere. Since the days of Cuvier many of these creatures have been referred to more suitable positions. The entire series of intestinal worms, as well as the Rotifera, have been removed to the Articulata, and the Bryozoa to the Mollusca; whilst the entire division of the Protozoa is a dismemberment of the Cuvierian Radiata. The animals still left in the Radiate ALTERNATION OF GENERATIONS. 271 division are the Acalepha, the Polypes (except the Bryozoa), and the Echinodermata of Cuvier; but the differences between the last-named class and the other Radiata are exceedingly great, An apparently advantageous alteration in the classification of these animals has been proposed by Leuckart and Huxley. These Zoologists separate the Cuvierian Acalephe and Polypes from the Echinodermata, thus forming with them agroup which the former denominates Celenterata, from the structure of the alimentary organs; the latter, Nematophora, from the presence of thread-cells in the skin. According to Leuckart, this group may be divided into three classes, one of which is composed of the Hydroid Polypes, the Discophora and the Siphonophora ; the second of the Asteroid and Helian- thoid Polypes; whilst the third includes the Ctenophora. The Echinodermata must then be regarded as very aberrant forms of the Helminthoid section of the Articulated division; this at least is Mr. Huxley’s view; Professor Leuckart has not told us what he proposes to do with the remainder of the Radiata. Of the unicellular constitution of the Protozoa, considerable doubts are now being raised; and it seems difficult to reconcile the varied functions performed by these microscopic creatures, with their supposed simplicity of structure. Hitherto, however, authors have generally confined themselves to the expression of doubt; and no satis- factory theory with regard to the constitution of these living atoms has yet been put forward. There are two phenomena, or rather two modifications of the same phenomenon, to which we must refer in this place, as they are exhibited by members of all the Inverte- brate groups of animals. These are gemmation, and the so-called “ alternation of generations ;” the latter being only a peculiar modification of the former. In ordinary gemmation, the original individual produces buds which gradually assume the form of their parent, and are then either thrown off, to lead an independent existence (as in the Hydra), or retained in more or less intimate connexion with the parent (as in the compound Polypes and Bryozoa). We have here, then, an “alterna- tion,” not of “generations,” but of “reproductions;” the ovum producing a single animal, which produces others exactly resembling itself by a division of its own sub- stance ; and all these are equally capable of both sexual and gemmiparous reproduction. The process by which the “ alternation of generations” is effected, differs in nothing from ordinary gemmation; but the reswit of the process is somewhat different. In the cases to which this name has been applied, the individuals produced by gem- miparity differ more or less from their immediate parents; the functions of sexual repro- duction are confined to them, and the ova which they produce give rise to gemmiparous individuals. There is consequently no such thing in nature as an “alternation of generations ;” and the phenomenon which has been so denominated consists simply in. an alternation of gemmiparous and sexual reproduction, in which the offspring of the former process differs more or less from that of the latter. The observation of these phenomena has introduced considerable difficulty into the realization of the idea of an individual animal. We cannot regard every independent animal form as an individual animal, since we know that many of them occur as successive phases in the development of particular species; and on the other hand, it is by no means easy to conceive that these active, independent beings, are merely com- ponent parts, or organs, of a composite individual. Yet this appears to be the only satisfactory mode of explaining the phenomena in question ; and we must therefore regard the whole of the forms produced from a single ovum, until the progeny of that 272 ALTERNATION OF GENERATIONS. ovum produce ova in their turn, as so many manifestations of the life of an individual animal. The sum of these manifestations, therefore, makes up the life of the animal. It has been proposed to employ the term zooid, to indicate the separate manifestations which, when put together, constitute the zoon, or animal individual. The German naturalists have applied the term nurses (ammen) to the gemmiparous zooids. This view may perhaps be rendered clearer by a comparison of the phenomena with those of the metamorphosis of insects. In the latter the egg produces a sex-less indi- vidual (/arva), which undergoes certain changes before attaining its reproductive form; but during the whole of these transformations it still retains its perfect individuality. But if each larva gave rise to one or more sexual forms by gemmation, we should have a case of “alternate generation ;” and this really takes place in the Aphides (p. 348), if we may regard the viviparous specimens as gemmiparous larval fornis. These phenomena present very different degrees of complication in different species of animals, Thus the individual Salpa (p. 423) consists of two zooids, one oviparous, the other gemmiparous; the Meduse exhibit a greater complication, the polypes produced from their ova often producing other polypes by ordinary gemmation, from which sexual Meduse again take their rise (see pp. 252, 253). The Cestoid worms also consist of two sets of zooids; the embryo is a cystic worm, always furnished with a head, and often producing several heads by gemmation; each head afterwards produces a series of sexual zooids by gemmation, which together form the ordinary Tape-worm (see p. 272. In some Zrematode worms the individual consists of three zooids: the free-swimming embryo (1) produces a sac-like body (2) by internal gemmation ; and this in like manner gives rise to a number of germs, which are converted directly into the sexual zooid (3). In the Aphides, as many as eleven consecutive series of gemmiparous zooids have been observed to intervene between two periods of sexual reproduction. We trust that these remarks, brief as they are, may suffice to furnish the reader with a tolerably clear notion of some of the most interesting phenomena in the Natural History of the lower animals,—phenomena, the correct comprehension of which is of the greatest importance to the student of Zoology. cONUS, VERTEBRATA—GENERAL CHARACTERS. 273 GEEKY BABOON. CRESTED HERON. 4 DIVISION V.—VERTEBRATA. General Characters.—In the preceding volume we have traced the general characters and classification of the four great groups of Invertebrate Animals; there remains only the fifth and highest division of the Animal Kingdom, the VerTeBRata, including perhaps fewer species than some of the preceding divisions, but calling for a greater share of our attention, both from its numbering amongst its members our own species and those which most closely approach us in organization and intelligence, and from the circumstance that nearly all our domestic animals, and the majority of those which are in any way useful to the human race, belong to its ranks. The most essential character of this great and important division of the Animal Kingdom, consists in their possession of a bony or cartilaginous internal skeleton, serving partly for the protection and support of the internal organs, and partly for the attachment of the muscles by which motion is effected. The admirable paper by Professor Owen “On the Principal Forms of the Skeleton,” in a preceding volume, will preclude the necessity of our dwelling upon the structure of this set of organs at any great length; but the proper comprehension of this portion of our subject requires that we should furnish the reader with a short account of the general principles upon which the bony framework of Vertebrate animals is constructed. Of this, the most essential and persistent portion is that called the spine or vertebral column. It forms the centre of the whole skeleton, and serves to connect all the other parts of the structure, which are, in fact, merely to be regarded as its appendages. It is never wanting in any animal of this division, although in some of the lowest species 274 STRUCTURE OF THE VERTEBRAL COLUMN, (the only ones, in fact, whose title to a position amongst Vertebrated animals has ever been disputed) it forms merely a semi-cartilaginous cord (the chorda dorsalis), present- ing a considerable resemblance to the earliest form of the vertebral column in the embryos of the higher Vertebrata. In the. majority of these animals, however, the spinal column consists of a number of segments (vertebre) united together in such a manner as to allow of a greater or less degree of flexibility (Fig. 1), and giving rise to various appendages, of which some serve for the support and protection of the most important organs, whilst others assist in the motions of the animal. Each vertebra (Fig. 2) is composed of a centre or body (a), a short more or less cylindrical bone, which is articulated to its fellows on either side in various modes —sometimes by a regular ball and socket joint, some- times by the interposition of plates of fibro-cartilage between the flattened end-surfaces, or by the insertion of bags of fluid into cavities left in the same situation. From the Gere upper surface of the body of eack vertebra springs a bony ; arch (4), composed essentially of several bones, which are usually com- pletely united together, and to the centre of the vertebra. The apertures thus formed in the vertebre constitute a sort of bony tube, through Fig. 1s verte: which the central axis of the nervous system passes, and is thus pro- ” tected from external injury. From this circumstance the arches formed by the superior appendages of the vertebral centre are denominated the neural arches (Gr. neuron, a nerve). The number of pieces of which the spine is composed, which, although variable, is always considerable, confers a great amount of flexibility upon the entire column; whilst from the shortness thus acquired by the individual joints, the flexure of the whole is effected without any of those sudden bendings which might injure the delicate and important organ that passes through their apertures. With the addition of a few bony processes, which serve either for the attachment of muscles for the movement of the spine, or to control its flexion, either by their actual contact or by furnishing points of attachment for ligaments, we have the vertebra of the human anatomist. But the vertebral segment of the philosophical anatomist includes much more than this: it is completed by a second arch, formed of several bones, which incloses a space beneath the body of the vertebra; and this, from its protecting the principal organs of the circulatory system, is denominated the hemal arch, The degree of development of this inferior arch is very variable. It is often imperfect—that is to say, the bones of which its two sides are composed are frequently not united at their extremities; and in many cases this arch appears to be entirely wanting. Of this second arch, the best examples are to be found in the ris, the long curved bones which inclose the cavity of the chest in most vertebrated animals, usually articulated by a moveable joint to their corresponding vertebra, and frequently united at their extremities to a central piece, the sternum, which completes the hemal arch. At its posterior extremity the vertebral column is usually produced into series of gradually diminishing vertebra, of greater or less length as compared with the body. ‘These constitute the tail, which in fishes and whales forms the principal organ of locomotion. At its anterior extremity the vertebral column terminates in a bony case, the skull or cranium, of which the cavity incloses the brain, or centre of the nervous system ‘ THE SKULL AND BONES OF THE LIMBS. 275 the spinal cord, which, as we have already said, runs through the tube formed by the apertures of the spinal column, communicating with this central nervous mass by a corresponding opening in the base of the skull. Below and in front of this bony case ce and jaws of the animal; and the whole may be are several bones, forming the fa considered as constituting the skeleton of the head. It is difficult at first sight to refer these irregular and complicated bones to the same type of structure as the vertebrae forming the spine; but the researches of several illustrious naturalists, amongst whom none perhaps have contributed more to the result than our countryman Professor Owen, have now placed it beyond a doubt that the cranium is composed of the neural arches of several vertebrae, and that the bones of the face are the heemal arches of some of these. According to the views of Professor Owen, the skull is composed of four neural arches, of which one (nasa?) includes the bones forming the nose; the second (frontal) is formed principally by the frontal bones ; the third (parietal) includes the parietal ‘bones, the alisphenoids and the mastoids; and the fourth and hindmost (occipital) the occipital bones, which form only a single bone in many Vertebrata. The centres of these vertebre form the floor of the cerebral chamber ; that of the occipital vertebra constitutes the lower boundary of the large aperture, through which the spinal cord communicates with the brain. The bones of the face, the upper and lower jaws, are the hzemal arches of the first two of these vertebrae; and the corresponding arch of the third vertebra, is the hyoid bone, which supports the tongue and assists in its move- ments, The hemal arch of the fourth cranial vertebra is composed of certain bones of very variable form, which support the anterior limbs; and although these, in many Vertebrata, are removed to a considerable distance from the head, in the Fishes and some other members of the group they are actually articulated to the hinder part of the skull; and as, in all cases, they are evidently identical organs, analogy forbids us from giving them different derivations. The fore-limbs of the Vertebrata are regarded as appendages of this heamal arch, and the hind limbs as similar appendages of another bony arch (the pelvis), which is firmly attached to one or more vertebree at the posterior extremity of the trunk. The majority of the Vertebrata possess two pairs of these organs; but the hinder pair is deficient ina considerable number of fishes, in the whales and some other animals, whilst the serpents and some fishes are totally deprived of limbs. In none, however, does the number of these organs exceed four. The structure of the limbs is essentially the same in all yer- tebrated animals; and it is entirely by the modification of this typical structure that those multifarious and beautiful contrivances which adapt these creatures tq such various spheres of action are obtained. It is, indeed, in the modifications which these parts undergo, whilst still retaining their primitive character, that the natural theolo- gian finds the most striking of those imstances of design in creation upon which he loves to dwell; and it is upon these also that the zoologist depends, to a great extent, for the means of classifying and characterizing the numerous members of this important group. ‘ i The conformation of the bones of all the limbs is very similar. They commence by a bone, usually of an elongated, cylindrical form, which articulates by one extremity with the supporting bony arch; this is the bone of the arm or thigh (umerus or femur). At its free extremity, this bone furnishes a point of articulation for a pair of parallel bones, forming the fore-arm and the shank of the leg; in the anterior extremity these are denominated the radius and ulna; in the binder limb they bear the names of tibia and fibula. They are frequently united at the two extremities, or even amalga- 276 NERVOUS SYSTEM. mated, throughout their length, into a single flattened bone, which, however, generally exhibits distinct traces of its original composition. When separate they also usually possess a considerable amount of independent motion; the wna and the tibia being firmly articulated to the extremity of the preceding bone; whilst the radius and fibula, which have less to do with the formation of this articulation, are capable of rotating to a greater or less extent round their more immoveable fellow. At the extremity of the bones of the fore-arm and shank, the first of those of the hand and foot are articulated (the carpal and tarsal bones). These consist of a variable number of short bones, form- ing the wrist and the base of the foot with the heel. Beyond these come the metacarpal and metatarsal bones; these, five in number in many Vertebrata, are arranged in a transverse series, articulating by their bases with the carpals and tarsals. Their num- ber, however, is often greatly reduced, in many cases only one of them remaining. They are followed by the phalanges, or bones of the fingers and toes, of which each metacarpal or metatarsal bone appears normally to bear three; like the preceding bones, they are often reduced to a single series. We need not refer in this place to the manifold changes which these parts undergo to adapt them for the varied necessities of the animals composing this great division. These have been admirably described by Professor Owen in the paper already referred to; and we shall have occasion, in the sequel, to notice most of them in characterizing the different groups into which these animals are divided. An essential distinction from the articulated series of animals is to be found in the mode in which the jaws of the Vertebrata open. In the Articulata, the jaws always separate laterally, so that the opening of the mouth is in the same direction as the axis of the body. In the Vertebrata, on the contrary, the jaws open vertically, and the oral aperture is consequently horizontal, or transverse to the general axis. The muscles of vertebrate animals are also placed on the outside of the bony skeleton ; whilst, in the Articulata, the external skeleton forms a series of rings, to the interior of which the muscles are attached ; even in those Vertebrata in which the skin is covered with bony or horny plates, forming a dermo-skeleton, which may be regarded, to a certain extent, as analogous with the external skeleton of the Articulata, all the more important muscles still find their points of attachment on the true skeleton, the general structure of which we have just been describing. In the majority of the Vertebrata, the outer integument is composed of a flexible skin, of which the surface is usually covered with scales, feathers, or hairs. : -In the structure of the nervous system, the Vertebrata present a great advance upon all the animals of the Invertebrate groups. The centre of this system is far more con- centrated in its form, and exhibits a far greater preponderance over the other parts. It forms what is called the cerebro-spinal axis, and is composed of the brain, a mass of nervous matter inclosed within the cavity of the skull, and of a cord of similar matter which runs down the canal formed by the neural arches of the vertebral column (Fig. 3). From the latter the nerves are given off, the ultimate branches of which are distributed to the various organs of the body. ' The brain, the seat of intelligence and volition, varies greatly in its development in the different members of this division, In man (Fig. 3), and many of the higher Vertebrata, it attains a great preponderance over the remainder of the nervous system ; and thé anterior portion, especially the cerebrum, or true brain, which is universally regarded as the organ of the mind, acquires a great development. In the lower forms, such as the fishes, on the contrary, the brain is small; and, in many cases, its bulk is made up principally of those parts which are subservient to the organs of special sense. NERVOUS SYSTEM AND ORGANS OF SENSE. 277 These are always present in the Vertebrata; and, indeed, with but few exceptions, all these animals possess organs of sight, hearing, smell, and taste, in u state of con- a 6 siderable perfection, With one exception, auditory organs are possessed by all Vertebrata. In the lower forms, they are indeed of very simple construction, and completely inclosed within the head, with no communication with the external world, so that it is difficult to imagine that they can furnish their possessor with any distinct perception of sounds. By degrees, however, their structure becomes more perfect, and they, at the same time, approach the surface of the head, where they acquire an opening which facilitates their reception of external impressions, and which is often furnished with a funnel-like external ear, by which the sonorous vibrations are conducted to the internal organs. Eyes are wanting in a greater number of these creatures ; but, as a general rule, the visual organs are present in great perfection. In the Fishes, the cavity of the nose is completely closed posteriorly ; but in all other Vertebrata there is a free passage through this organ, either into the mouth or the pharynx. In some forms, in which the sense of smell appears to be very imperfect, the nasal cavity forms mere sacs, or simple tubes, for the passage of air to the lungs; whilst in those which possess this sense in a state of greater perfection, the surface of this cavity is increased by a complicated arrangement of bony cells, clothed with mucous membrane, and richly provided with nerves. The sense of taste, is exercised by the tongue; but this organ is often of a hard-and horny consistency, or modified in other ways so as to render its gustatory powers very doubtful; it is some- times capable of considerable movement, but frequently im- moveably attached to the floor of the mouth. The alimentary organs are very similar throughout the group. The mouth is generally furnished with teeth, which are sometimes confined to the jaws, sometimes distributed over all the other bones which assist in the formation of the oral cavity. In the Birds, the Tortoises, and a few other Vertebrate animals, the teeth are entirely wanting. In the former, the jaws are covered with horny plates, which serve Fig. 3.—Cerebro-spinal axis of Man; a, cerebrum; 0, anterior lobe; ce, middle lobe; d, posterior lobe ; e, cerebellum; jf’, medulla oblongata ; #, spinal cord. instead of teeth for the division of the food. In some of the lowest Fishes, even the jaws are absent. From the mouth a membranous tube, the esophagus, leads to a dilated portion of the alimentary canal, the stomach, in which the process of digestion commences ; fram this the food passes into « tube of variable width, the intestine, in which the principal absorption of alimentary matters takes place (See Puysiotocy). This leads’ to a posterior aperture, the anus, through which the refuse of the digestive process is discharged. The different parts of the intestinal canal have received different names from anatomists. The opening leading from the stomach into the intestine is deno- minated the pylorus ; the part of the intestine immediately following this is called the duodenum; this is succeeded by the small intestines, which are coiled together in a 278 ALIMENTARY ORGANS. voluminous mass in the cavity of the belly, and terminate in the large intestine, which is continued, under the names of the eolon and rectum, to the anal opening | (Fig. 4). The large Fi intestine frequently / y--- Cisophagus “~~~ Panereas 3 5 & terminates in one or more blind extre- i mities (ceca), which j project beyond the : point at which the ee small intestine en- “Spleen ters it. Various glandular organs oc- cur in the course ES Colon of the alimentary “h canal, Of these, the \ \ \ Gall-Bladder -«__, Large Intestines ...._...! «Smallintestine salivary glands are situated in the neigh- sae pourhood of the aes j mouth, into which Appendix of ___ they pour their se- cretion during the the Cecum mastication of food ; they are wanting in ‘ \ the Fishes and some, ff g \ other aquatic ani- SmallIntestine Rectum ‘ mals. The diver, the : eae largest. of all the Fig. 4.—Digestive apparatus of Man. glandular organs of the body, is placed close to the stomach, and pours its secretion, the bile, into that portion of the intestine denominated the duodenum, which also receives the saliva-like secretion of another glandular organ, the pancreas, situated in its immediate neighbourhood. The latter organ is wanting in some fishes. The spleen, a glandular organ peculiar to the Vertebrata, is also wanting in some fishes; it is contained, like the preceding, in the abdominal cavity; but its functions are not yet clearly ascertained. The blood in the Vertebrata (with but a single exception) is always of a red colour. This is due to the presence in the blood of a multitude of minute red particles (globules, corpuscles) of 4 round or oval form, the fluid portion being colourless. In this par-, ticular, the animals of this division differ from all the Invertebrata, in which any per- ceptible coloration of the blood is inherent in that fluid itself, and not due to the sus- pension of coloured particles in an otherwise colourless fluid. The circulatory system also exhibits a completeness which we do not meet with in the Invertebrata ; the heart, with the single exception of the Amphioxus, is always muscular, and the blood is carried to. and from that organ in a complete system of vessels,—never, as in the majority of invertebrate animals, passing through mere cavities hollowed out in the other tissues of the body. x €IRCULATION IN VERTEBRATA. 279 The structure and arrangement of the circulatory system present considerable variations, principally in accordance with the conformation of the respiratory organs. | In the aquatic forms, respiration is effected by the agency of gills, which usually take the form of vascular bands, supported upon bony or cartilaginous processes of the hyoid bone, and bearing an apparatus of minute lamina, or tufts of filaments, permeated by capillary vessels, through which the blood passes, and is thus exposed to the action of the surrounding medium. The water required for respiration is taken in by the mouth, and passes out through openings at the posterior part of that cavity, whence it passes over the branchial apparatus. In the Fishes, which present us with this form of respiratory apparatus, the heart consists only of two cavities, of which one | receives the blood on its return from the organs of the body, whilst the other drives it through the gills, thence to be distributed to the various organs by the arteries. The air-breathing Vertebrata are all furnished with Jungs, cellular or spongy organs inelosed in the cavity of the chest, into which the air passes by the mouth, or nasal passages, and is returned by the same route. The cellular textare of the interior of the : lungs is permeated in every part by capillary blood vessels; and it is in these that the blood comes in contact with the air, and receives its revivifying influence. But the blood, in these animals, instead of passing from the lungs direetly into’ the arteries, returns again to the heart, and is driven out from this into the arteries. In conse- quence of this arrangement, the heart acquires a more complicated structure than in Fishes; the recipient chamber (auricle) becomes doubled, and, in the higher forms, the expellent chamber (ventricle) is also divided into two cavities by a longitudinal par- tition, so as to form, as it were, two hearts, one subservient to the respiratory process, the other to the general circulation. In addition to the proper blood-vessels, we meet in the bodies of vertebrate animals with a system of absorbent vessels, connected with the sanguiferous system, some of which convey the products of digestion from the walls of the intestinal canal into the circulation; whilst others, which ramify through all the organs of the body, take up a clear fluid, called 7ymph, and carry it to the same destination, The former of these vessels are denominated Jacteals, from the milky appearance of the fluid contained in them ; the latter dymphaties, from the nature of their contents. Both sets of vessels terminate in a common trunk, the ¢horacie duct, which discharges its contents into one of the principal veins in the neighbourhood of the heart. The nitrogenous waste substances are got rid of by the agency of the urinary organs, of which the kidneys are the most important; their secretion sometimes passes off by a particular opening; but is usually discharged into the hinder part of the intestinal canal, and evacuated through the anal aperture with the foecal matters. The reproduction of the Vertebrata is always sexual, and the sexes are invariably on separate individuals. No authentic instance of “hermaphrodism has ever been recorded amongst these creatures; and all the supposed cases of the occurrence of this pheno- menon have originated in the imperfect observation of peculiar malformations. The majority of the Vertebrata are oviparous animals, producing perfect eggs, which contain all the materials necessary for the development of the embryo. A few retain the eggs in the oviducts until the young are ready to be hatched, and these are frequently denominated ovo-viviparous ; whilst one class, the Mammalia, is composed of truly viviparous animals, in which the embryo early acquires a vascular connection with the mother, and thus, deriving its nourishment from her blood, continues its development to a far greater extent hen could haye been effected by means of the materials contained in the impregnated ovum. 280 CLASSIFICATION—FISHES—BATRACHIA—REPTILES. The development of the embryo always takes place from a given spot on the surface of the yelk, and never, as in many invertebrate animals, by the conversion of the entire yelk into an embryo. At first the embryo forms a slight elevation at the surface of the yelk sac; this gradually increases in size, and forms a sort of disc, embracing a larger or smaller portion of the yelk, with a slightly elevated line running along its dorsal surface. In this the rudiments of the spinal cord and vertebral column soon make their appearance, followed by the heart and circulatory system. The yelk sac is gradually absorbed into the body of the embryo, with the alimentary canal of which it stands in connection; but in many cases it forms a distinct sac dependent from the belly of the young animal, and persistent after this is excluded from the egg.’ Divisions.—We divide the Vertebrata into five classes, of which the first four are composed of oviparous animals. Of these, the first includes the vast group of Fishes p (Pisces), animalsadapted exclusively. for an aquatic life, respiring by means of gills, and furnished with a heart with only two cavities. Their cx- * tremities are converted into fins, and their motions are principally effected by lateral strokes of the. Fig. 5.—Cod-fish. expanded tail, They are cold-blooded animals, and their skins are either naked or covered with scales. The nose is usually imperforate posteriorly. The second class, the Parawcia, 4 is formed by some singular animals, which are furnished with gills for aquatic respiration, during the whole or part of their existence, although they always ultimately - acquire lungs and the power of aérial respiration. The nasal cavities open into the mouth; the heart is formed of three chambers ; the blood is cold; and the skin usually _ naked. When ma- ture, these animals are usually fur- nished with four true feet. The other two classes of ovi- parous Vertebrata never possess gills at any period of Fig. 7.—Tadpole, or Young _ their existence. Batrachian. In one, the class of Reptiles (Reprrtza), the blood is cold, and the heart composed: Fig. 6.—Hyla, or Tree-Frog. Fig. 8.—Crecodile. CLASSIFICATION—BIRDS—MAMMALIA. 281 of only three cavitics—one ventricle and two auricles; the limbs, when present Fig. 9.—Great Tern, or Sea-Swallow (Sterna Hirundo). are adapted for terrestrial motion, and the skin is covered with scales or bony plates, The fourth class, the Birds (Avzs), is composed of warm-blooded animals, in which the heart consists of four chambers; the limbs are always present, the anterior pair being adapted for flight, the pos- terior for terrestrial pro gression, and the skin is clothed with feathers. The fifth and last class is composed of the truly viviparous Vertebrata, in which the young are nourished for a consider- able time after birth by a peculiar .secretion (milk), furnished by particular glands in the mother. Hence this class is de. nominated MamMaLia, They resemble the Birds in their warm blood, and in the structure of the heart ; but their limbs are almost always formed for terrestrial progression, and their bodies usually clothed with hair. Fig. 10.—Lemur, with its young. ? 282 THE CLASS OF FISHES. Cuass I.—Pisczs, on Fisuzs, General Characters.—The animals of this class, as already stated, are exclu- sively aquatic, and all the particulars of their structure indicate an adaptation to this mode of existence. The head is large, and set upon the trunk without the intervention of any distinct neck; the body is usually of a spindle-shape, tapering gradually towards the posterior extremity ; and the surface is usually smooth, without any irre- gularities which might impede the motions of the creature in its native element. In its general form the body is usually rounded, or slightly compressed at the sides; - sometimes this flattening proceeds to a much greater extent, so that the animal presents the appearance of a broad band or oval disc, of which the edges correspond with the dorsal and ventral surfaces ; in other cases the flattening takes place from above, down- ‘wards, producing a disc-like body, of which the upper and lower surfaces are dorsal and ventral. Locomotion is always effected principally by lateral strokes of the hinder extremity, accompanied, in the elongated species, by an undulating motion of the whole body. In accordance with this arrangement, the great bulk of the body of a fish is made up of powerful longitudinal muscles, whose office is the flexion of the spine. The skeleton exhibits a great diversity. In the lowest form of animal referred to this class, which has been described by some naturalists as an Annelide, and regarded by others as a transition form connecting the Annelida with the Fishes, the only trace of the vertebrate internal skeleton consists in a semi-gelatinous cord (the chorda dorsalis), which runs through the body of the animal, and supports the central axis of the nervous system, presenting, in “fact, a great analogy with the earliest form in which the skeleton presents itself in the embryonic states of other Vertebrata. In the Lampreys, the development of the skeleton makes a little step in advance ; the chorda dorsalis acquires a firmer or somewhat cartilaginous consistence, and, in some cases, ex- hibits slight indications of the segmentation of the vertebral column. In these animals, Fig. 11.—skeleton of the Perch. also, the brain. is inclosed within a cartilaginous skull. As we advance, we find the skeleton gradually acquiring greater firmness, becoming first cartilaginous and after- wards bony. In some cases, however, the centre of the vertebral column retains almost its original consistency, when the peripheral parts have arrived at the state of cartilage, In nearly all fishes which have the vertebral column in a bony or cartilaginous con- SKELETON OF FISHES. 283 dition, and formed of distinct vertebrae, the bodies of the latter are hollowed out, both before and behind, into conical cavities, the apices of which usually meet in the middle of the vertebra. These cavities are filled with a gelatinous matter, the remains of the embryonic chorda dorsalis. Only a single fish is known in which the ossification of the centres of the vertebre proceeds further than this; this is the Lepidosteus, or Bony Pike of America, in which each vertebra is furnished with an anterior convex, and a posterior concave, articulating surface. The superior or neural arches of the vertebrze usually terminate in very long spinous processes. The inferior, or hemal arches, exhibit a similar structure in the caudal region of the body, where they form a bony canal for the passage of the principal vessels, and, in a few instances, the same conformation extends into the abdominal region; but here we generally find a series of processes extending laterally from the bodies of the vertebre, bearing ribs which inclose the abdominal cavity. The lower extremity of the ribs is always free, as there is no sternum for their attachment. The structure of the skull, in Fishes, partakes of the variable charaeter of the rest of the skeleton. In the lowest forms it is a nearly membranous expansion of the soft cord which here takes the place of the vertebral column, which gradually acquires cartilaginous supports. In the higher Fishes, with cartilaginous skeletons—such as the Sharks and Rays—the skull is a cartilaginous case, formed of asingle piece; but in the bony fishes this becomes ossified from numerous centres, and the skull in these is usually of a very complicated construction. In most cases, however, the primitive cartilaginous skull is more or less persistent, so that in some instances the bony plates may be removed after the head has been boiled, leaving the brain for the most part still inclosed in its cartilaginous covering. The skull of a bony fish (Fig. 12) is of very complicated structure; the number of bones of which it is composed A ee being very considerable. The : 1 principal bones forming the cranium are the occipitals, the im--- sphenoids, the ethmoid, the pa- m.. tietals, the frontals, and the tem- : porals ; the basi-occipital bone, forming the lower boundary of the aperture through which the spinal cord quits the skull, exhi- bits on its posterior surface the Fig. 12.—Bones of the head of the Pike. : : 5 ¢, cranium ; or, orbit; m, nasal cavities; im, intermaxillar conical cavity which has already bone ; m, superior 1 ‘maxillary Done ; é, lateral partition. separating gills from mouth; p, io, op, ae of operculum, been described as characteristic or giil-cover. of the body of the piscind verte- bra, and articulates in the usual way with the first vertebra of the spinal column. The general form of the head is that of a pyramid with the base directed backwards ; the orbits are placed on the sides, and the nasal apertures a little in front of them. The upper jaw is formed of the maxillary and intermaxillary bones, of which the latter usually bear teeth, and form the actual margin of the mouth ; whilst the former, as a general rule, are unarmed, and lie concealed in the flesh behind the inter- maxillaries. “These are bent back at an angle at their interior portion, so that they consist, in fact, of two branches, of which one serves, as just described, to form the biting edge of the mouth, whilst the other is received in a groove at the end of the nose, 284 SKELETON OF FISHES, in which it can move freely in those fishes which have a protrusible mouth. The palate is formed of three bones: the palatine bone, which is usually armed with teeth; the transverse bone, by which the palate is generally articulated to the cranium; and the pterygoid bone. The vomer also assists in the formation of the roof of the mouth, and is usually armed with teeth. The two sides of the lower jaw are usually firmly united at the anterior extremity, but rarely joined by ossification, ach side is composed of several pieces, usually threc, but sometimes four or more in number. . Of these only one—the anterior—is furnished with teeth; the basal bone articulates with a sort of bony partition, formed of several: bones immoveably articulated, which are also firmly attached tothe skull in several places. The opercula, or gill covers, are also dependent from these bones. These are usually composed of four bony plates, of which the first:—the preoperculum—is a somewhat crescent-shaped piece, extending from the cranium to the articulation of the lower. jaw (Fig. 12); whilst the others, which are distinguished by particular names descrip- tive of their relative position, are moveably articulated to the preoperculum, and serve to close the branchial aperture. The relative size of these plates, their forms, and general structure, furnish the zoologist with excellent characters for the discrimination of genera and species. Below these bones e we find the hyoid arch, which attains agreat development in fishes, and serves to support, not only the tongue, but also the respiratory ap- paratus (Fig. 12). From the front of this arch a peculiar bone (the lingual or glossohyal) pene- trates to the apex of the tongue, where it is frequently co- vered with teeth. Behind this the hyoid bone forms two branches, each of which is at- r | | | + SS in hag Z ZI = Ip Ginn a--~-------: | rel ; ‘ : i co ca aboh Fig. 13.—Bones of the head of the Perch, after the removal of the jaws, lateral partition, and operculum, on one side, to show the interior of the tached to the pre- operculum of its own side by a small bone called the styloid or stylohyal. To the side of each branch a variable mouth, and the hyoid apparatus; c, cranium; or, orbit; v, vomer (armed with teeth); im, intermaxillary; dp, teeth implanted on the palatine arch; mi, lower jaw; J, lingual bone; 8, lateral branches of the hyoid apparatus; s, process for the attachment of these to the lateral partition; 7, r, branchio-stegal rays; a, branchial arches; ph, superior pharyngeal bones ; ar, articular surface by which the lateral partition is attached; o to A, bony framework supporting the pectoral fin, p; 0 and o', scapula divided into two pieces ; A, humerus; ab, bone of the fore-arm ; ca, bone of the carpus; co, coracoid bone. number of slender-curved bones is articulated; these are called branchio-stegal; they support a membrane called the branchio-stegal membrane, whose office is to close the FINS OF FISHES. 285 gill-slit from beneath. Behind these, supported at one extremity upon the hyoid bone and articulated at the other to the bones of the cranium, are four pairs of bony arches, formed of two pieces in the cartilaginous fishes, but usually consisting of four in the bony species. On the outside these arches bear the branchial laminz, but their inner surface is usually armed with spines or teeth. They articulate with the cranium by small bones called the superior pharyngeals, which, like all the other bones in the neighbourhood of the mouth, are often armed with teeth. The surface presented by Fishes to the surrounding element is greatly increased by the peculiar organs called:jins. These are of two kinds. Some placed in pairs on the lower surface of the body are the analogues of the limbs of the higher vertebrated animals ; whilst the others, situated single on the median line of the body, are to be regarded as _ appendages or developments of the cutaneous system. The former never exceed four in number ; but one or both pairs are frequently absent. These organs have received different names in accordance with their position on the body (Fig. 14). Of the two pair of fins corresponding with the limbs of other Vertebrata, one pair has received the name of yectoral fins, from their being situated on the breast immediately behind the branchial aperture; they are the analogues of the anterior members. The representatives of the hind limbs of other vertebrated animals are denominated ventral fins, their normal position being These Fig. 14.—Bearded Mullet, showing position of fins; p, pectoral fin; v, ventral. fin; d1, first dorsal; @2, second dorsal; ¢, caudal; a, anal; 0, opening of gill-covers. on the belly, close to the anus. fins, however, are liable to great changes of position, being often advanced close under the pectoral fins, or even sometimes placed before these, quite on the throat of the animal The single or median fins are rather variable in number. The dorsal surface usually bears one or more of these’ organs, called dorsal jins; similar fins occur on the ventral surface behind the anus, called anal fins; and the extremity of the tail is almost always furnished with a broad expansion, the caudal jin, which is the pincipal agent in progression. In some fishes the median fins are continuous round the whole posterior portion of the body ; and this is the condition in which these organs first make their appearance during the develop- ment of the embryo in all Fishes, the subsequent changes which take place in the arrangement of the parts being due to the unequal development of the bony rays which support and stretch the membrane of which the fins are composed. The struc- _ ture and arrangement of the rays varies greatly in the different groups of Fish, and will be referred to hereafter. The pectoral fin in all fishes consists essentially of the same parts as the anterior _limb of any other vertebrated animal. . Concealed within the skin, immediately behind the branchial openings, we find a bony circle composed of several pieces, representing the shoulder blade, with the coracoid bone and clavicle (see Fig. 13); this supports the bones of the arm, which are usually very short, and bear @ series of carpal bones at their extremity ; the latter support a number of short cylindrical joints, from which the rays of the fin take their rise. The internal supports of the ventral fins never present such a close resemblance to the pelvis of the higher Vertebrata as do those of 286 SCALES. the pectorals to the scapular arch. When situated in their normal position in the abdomen, they always consist of cartilaginous or bony pieces lying freely in the muscles and quite unconnected with the vertebral column ; but when the fins are advanced from this position to the neighbourhood of the pectorals, their internal supports are attached to the scapular arch of the latter members. The skin of the animals of this class is almost wits protected by a covering of scales, which are sometimes of a horny and sometimes of a bony texture. Very few fishes are destitute of this scaly covering, which, however, is very variable in its distribution—its component parts being sometimes placed so close that one scale lies over the other like the tiles upon the roof of a house, sometimes fitted together exactly by their edges, and sometimes seattered irregularly over the surface of the skin. The differences in the form and structure of the scales is of great importance in the classifi- cation of Fishes ; and Professor Agassiz even considers that they stand in such intimate relation with the general organization of the animals, that he has proposed to employ them as primary characters for dividing this great group into orders. This system has only been partially adopted by succeeding naturalists—as, although it is admitted on all hands that it has been of great service, especially in facilitating the study of fossil Fishes, there can be no doubt that it has the defect common to all systems founded upon characters derived from a single set of organs—that of separating nearly allied animals, and bringing others which have no mutual affinity into close juxtaposition. The most ordinary form is the thin horny scale, such as we meet with upon most of the common eatable fish. These consist of small horny plates, generally of a more or less oval form, which lie one over another, exactly like tiles, and are usually arranged in such a manner that each scale, being partially covered by two scales of the preceding row, only exhibits a somewhat triangular portion of its own surface. These scales are peculiar to the osseous fishes. They are found to consist of two layers, of which the lower is of a horny texture, whilst the upper resembles enamel. The scales are usually marked with concentric and radiating lines, of which the former appear to belong to the outer and the latter to the inner layer. In some Fishes they present a smooth outline—these are the Cycloidet (Gr. kuklos, w circle) of Agassiz; whilst in others, forming the order Ctencidei (Gr. kteis, a comb) of the same author, the hinder margins of the seales are set with spines. Another form of scale, exhibited by very few living species, although the Fishes of which it is characteristic were at one time almost the only representatives of the Verte- brata existing on our planet, is composed of a hard bony substance, covered with a coating of enamel, which often resembles the enamel of the teeth in structure. These scales are much thicker and larger than the horny scales, and are usually of a rhomboidal form, arranged side by side without overlapping, although, in a few instances, they resemble ‘the horny scales in arrangement. The Fishes furnished with this bony armour are called Ganotdei (Gr. ganos, splendour) by Agassiz. In » third form the bony matter and enamel is distributed more or less irregularly over the surface of the skin ; some- times, as in the Sharks, projecting from all parts in the form of small grains, and some- times, as in the Rays, forming larger discoid organs, from the centre of which acute spines, resembling teeth in their structure, frequently project. These are the Placoidet (Gr. plax, a plate) of Agassiz. A line of peculiar scales, each of which is furnished with a minute tube, may be observed.running along the sides of most fishes; it is called the lateral line, and its peculiarities are of considerable importance in the discrimination of genera and species. NELVOUS SYSTEM OF FISHES. 287 The little tubes lead into a canal which follows the course of the lateral line, and which has been generally considered as subservient to the production of the slimy matter with which the surface of Fishes is usually so plentifully indued. It seems probable, how- ever, that this slime is, in reality, the representative of the outermost layer of the skin, and that the so-called mucous ducts are connected with the exercise of some special sense, as they communicate with a very singular apparatus, of tubes inclosed in the bones of the head, and furnished with a peculiar arrangement of nerves. The colours of fishes are due to the presence of coloured fatty matters in the skin ; but the beautiful metallic tints displayed by so many of them are produced by numerous microscopic plates, apparently of a horny nature, which are distributed over the surface. ' In their nervous system, fishes. exhibit a striking inferiority to the generality of A B vertebrate animals. The cranial cavity is small, but even this is only partially occupied by the brain, which is of very small size when com- pared with the body, or even with the other parts of the nervous system. It is distinctly divided into three parts, of which the anterior, representing the cerebral hemispheres of the higher Vertebrata, is usually small; whilst the middle division, from which the optic nerves take their rise, generally forms a considerable portion of the brain. In the Sharks, however, the general perfection of which contrasts strongly with the cartilaginous nature of their skeleton, the cerebral hemispheres generally predominate over the other parts of the brain (Fig. 15, B) ; uate 1 eins a ene ie ie i EB: and from this and other circumstances, t cse hemispheres ; op, middle brain, giving rise fishes appear to be entitled to take the first rank to optic nerves; ce, cerebellum sp, spinal in the class, although zoologists generally, look- ing only at the imperfect ossification of their skelotons, have assigned them a very different position. The olfactory lobes constitute an interior prolongation of the brain, and are usually of very large size. The organs of the special senses are, as usual, situated upon the head. The nose is usually formed by a double cavity lined with a folded membrane ; each cavity opens on the snout by one or two apertures; but, except in one or two instances, there is no communication between the interior of the nasal cavity and the mouth, or pharynx. The eyes are large and flat, usually placed on the sides of the head, and furnished with six muscles for their movement, The auditory organ is completely inclosed within the bones of the head, and usually consists of a sac containing two otolithes, and a vesti- bule supporting three semicircular canals. In the Sharks, and their allies, we also find traces of a communication between the internal ear and the outer world. The sense of taste is probably by no means acute in fishes ; and as their scaly covering must neces- sarily render their general surface rather insensible to external impressions, they are often furnished with special tactile organs, in the shape of filaments, surrounding the mouth (Fig. 14), or detached from the pectoral fins, which probably assist them in their search for prey. A few fishes are furnished with a peculiar apparatus, which confers upon them the 288 ALIMENTARY ORGANS OF FISHES. singular power of communicating an electric shock to any animal with which they come in contact. The apparatus consists, in all cases, of a mass of gelatinous columns, separated by membranous partitions, which are richly furnished, both with vessels and nerves. The only fishes by which this curious property is undoubtedly possessed, are the Gymnotus, or Electric Eel of South America, the fishes of the genus Torpedo, and the Malapterurus and Mormyrus of the Nile. : The structure of:the alimentary canal is often very complicated. There is scarcely a bone that assists in the formation of the oral cavity that is not ofien furnished with teeth, although these organs are usually developed upon particular bones, The upper jaw generally bears two parallel rows of teeth (Fig. 13), one attached to the intermaxillary bones, and the other to the palatine bones; the vomer also is commonly armed with teeth. The teeth in the lower part of the mouth are usually confined to the lower jaw and lingual bone. Besides these, the branchial arches and the superior and inferior pharyngeal bones are almost always furnished with tecth, forming a sort of trap at the entrance of the oesophagus. The tecth are not inserted into sockets as in man and many other Vertebrata; they are merely attached to the surface of the bone upon which they are supported. In some cases, they are simply imbedded in the skin of the mouth; in others they are attached by means of ligamentous filaments, and these are frequently moveable. In most fishcs the tecth are constantly changing during the life of the animal, the older ones falling out to give place to others which are developed in their neighbourhood. They vary greatly, both in their external form and in their internal structure. The simplest form is that of a cone; but they are frequently compressed so as to constitute cutting organs, or widened into grinders. The conical teeth are often minute, and set very close together, so as to form a velvet-like surface. The cesophagus is usually very muscular, and the stomach large. The pyloric aperture is generally furnished with a membranous valve; and behind the pylorus there are, in most bony fishes, a variable number (from one to sixty) of blind appendages, or ceca (called the pyloric appendages, or cca), which are considered to be the representatives of the pancreas, which, in fact, occupies their place in the cartila- ginous fishes. From this point the intestine is more or less convoluted in the abdo- minal cavity, until it terminates at the anus; in some Fishes the colon is furnished with a spiral arrangement of valves, serving to increase its surface. The anal aperture is usually placed at the posterior portion of the abdomen; but in many cases it is removed further forward, and sometimes even opens close under the throat. ‘Che liver is usually of great size; it is almost always furnished with a gall bladder, and the gall-ducts open into the intestine, close behind:the pyloric aperture. The spleen is also invariably present. Almost all Fishes are predaceous animals, attacking and destroying indiscrimi- nately all the weaker inhabitants of the waters, such as Insects, Worms, Crustacea, and Mollusca, and preying with avidity upon the smaller individuals of their own class, Many of them are excessively voracious, seizing upon everything that comes in their way: these are always furnished with a formidable apparatus of teeth ; others, which are not provided with such powerful offensive weapons, confine their depredations to the smaller and. more helpless aquatic animals. Very few feed upon vegetable matters. p The respiration in all fishes is aquatic, and we meet with no instance of true lungs in any members of the class. Many species, however, possess a large sac-like organ, cqntaining air, which, as it is often connected with the asophagus.by a tube, _ CIRCULATION IN FISHES. 289 must be regarded as to a certain extent analogous to the lungs of air-breathing Verte- brata. This sac, which is known as the atr-bladder, has, however, nothing to do with respiration ; it receives blood from the arteries and returns it into the veins, and the ere Fig. 16.—Circulatory System of Fish. a, branchial artery; 3, arterial bulb; c, ventricle; d, auricle; e, venous sinus; jf, vena porta, liver, &.; g, intestine; h, vena cava; i, vessels of the gills; k, dorsal artery; J, kid. neys; %m, dorsal artery or aorta. air which it incloses is, probably derived from this fluid. Its office is to lessen the specific gravity of the fish, and it is furnished with 4 muscular apparatus, often of very curious construction, by means of which its capacity may be changed, so as to render the animal heavier or lighter than the surrounding medium. The mechanism by which respiration is effected is as follows :—The gills are composed of a number of membranous lamine, furnished with minute blood-vessels, and supported upon bony or cartila- ginous arches, which surround the pharynx. These arches are separated from each other by slits; and the water which is drawn into the pharynx by a movement of deglutition, passes off through these slits, and escapes by the opercular aperture. These organs are fitted exclusively for aquatic respiration. Unless the gill-lamine are surrounded by moisture, and, as it were, suspended in the surrounding medium, the majority of fishes soon die, from the clogging of those delicate organs and the rapid desiccation of their surface. Some species, however, are furnished with a special ap- paratus to keep their breathing organs moist when in the air; and a few others, which have no such provision, appear to be very little affected by a temporary absence from their native element. With but a single exception, ali fishes possess a muscular heart, which is situated under the throat, usually within the angle formed by the two sides of the scapular arch (Fig. 16). It is composed of two cavities,—an auricle, which receives the blood on its return from the body, and a ventricle, which drives it again into the system. The blood, on leaving the ventricle, passes through a main artery, which is usually bulbous at the base, and, in many fishes, is covered in the same part with a powerful muscular coat, and furnished with a valvular ap- paratus. From the continuation of this arterial bulb, which runs forward, the branchial vessels are given off on each side; these conduct the blood, which is still in the venous state, into the gills, where, in passing through the numerous capillary vessels with which the sur- face of those organs is covered, it comes in contact with the water, and undergoes that change which it is the object of respiration to produce in the blood. After passing through this network of minute vessels the blood is again collected in larger vessels, and T 290 REPRODUCTION OF FISHES. | conveyed to the aorta, or principal artery, which runs down the whole length of the body immediately below the vertebral column, giving off branches to the various organs | during its passage. After passing through the capillary vessels of the body the blood is | again collected in the veins, which convey it into a great vein running up towards the heart, called the vena cava. In its course towards the heart a portion of the venous blood is, however, diverted into a peculiar system of veins, called the system of the vena porta, which ramifies through the substance of the liver ; the kidneys are also supplied with venous blood. Thus the heart in Fishes acts both as a systemic and a respiratory heart, a single contraction of the ventricle serving to propel the blood not only through | the vessels and capillaries of the respiratory apparatus, but also through those of the general circulation ; whilst a portion of the fluid also passes Wrungh the capillaries of the liver and scidieys. The last-mentioned organs are usually of very large size, and lie in the immediate neighbourhood of the vertebral column, The ureters are much branched at their origin, but afterwards unite to form a single canal, which often assumes the form of a bladder ; and the secretion is discharged sometimes into the rectum and sometimes by separate apertures situated close behind the anus. These animals are all essentially oviparous. The ovaries, well known under the name of oe, are generally of large size, and, when fuily distended with ova, occupy a considerable portion of the abdominal cavity, which they often distend to a great extent. The number of ova contained in the ovaries of a single fish is often enormous. In most fishes the mature ova are carried out by means of an oviduct, which opens either into the last portion of the intestine or by a separate aperture immediately behind the anus. In a few the oviduct is ‘wanting, and the ova, when ready to be deposited, break through the walls of the ovaries into the abdominal cavity, whence they escape by one or more apertures. The male organs occupy the same position as those of the female; they are commonly Imown as the soft roe. The mode in which their contents are evacuated presents much the same differences as in the female, As a general rule, the products of these organs are discharged at once into the water; the fish usually resorting in crowds to the same spot for the purpose of spawning, so as to. secure the. impregnation of the ova. This is evidently the object of the curious instinct which prompts so many fishes to undertake migrations in vast shoals, and often to great distances. The Herring, the Pilchard, and the Mackerel are examples of fishes which perform considerable journeys in search of a proper place in which to deposit their spawn. The Salmon is also very remarkable in this respect, from the pertinacity with which it continues:its course from the sea, in which it habitually resides, in order to deposit its ova in the small streams near the sources of rivers. The spawning appears to take place only once a year. Many fishes, however, are what is called ovo-viviparous; that is to say, the ova are retained within the oviduct until the complete evolution of the embryo. The mode in which the impregnation of the ova is effected in these cases is not exactly known. Fishes appear always to select shallow water for the deposition of their ova; but, beyond this, they do not generally exhibit any care for their offspring. A few, how- ever, form a sort of nest for the protection of their eggs and young; and in some instances, the male remains as a guard over the fry until they have acquired sufficient | strength and agility to venture forth into the world. The little Sticklebacks (Gasterosteus), so common in all our ponds, furnish an interesting example of the exercise of this instinct. CLASSIFICATION OF FISHES. 291 Divisions.—The classification of Fishes has always presented considerable difficulties to the naturalist. Linnaus, who placed the cartilaginous fish amongst the Amphibia, divided the bony fishes into orders according to the position of the ventral fins; Cuvier founded his primary groups upon characters derived from the consistence of the skeleton (cartilaginous or bony), subdividing these into orders in accordance with the characters presented by the fins and gills; and Professor Agassiz afterwards proposed the system to which we have already referred, founded upon the structure of the scales. The arrangement here followed is nearly identical with that proposed by Professor Miiller in his valuable memoir on the Ganoid Fishes, published in the “ Transactions of the Berlin Academy” for 1844, in which, by combining the systems of Cuvier and Agassiz, and making such alterations as his own extensive acquaintance with the animals suggested to him, he has succeeded in arranging the members of this difficult class in a far more satisfactory manner than any of his predecessors. We divide the class of Fishes into five great orders.* In the first, the Leptocardia, the heart is entirely absent, and the circulation is effected by the pulsations of the great vessels, The vertebral column is represented by a gelatinous band supporting the spinal | cord, and the latter exhibits scarcely any traces of cerebral organs at its anterior extremity. The fishes of the other four orders have a distinct muscular heart, com- posed of two chambers. In the first and second, the aperture leading from the ventricle into the artery is furnished with two valves, and the base of the artery is destitute of a muscular coating ; in the others the valves at the entrance of the artery are wanting ; but the inner surface of the latter is furnished with numerous valves, and its outer surface is clothed with a muscular coating. Of the former, the Cyclostomata are further distinguished by their cartilaginous skeleton, their sac-like branchiee, opening by a ‘series of apertures along the sides behind the head, and their round sucking mouth without jaws; whilst the Zeleostia have a well-developed bony skeleton, a2 mouth furnished with jaws, and free branchial organs concealed under an operculum. The Ganoidea, forming the first order of fishes with a muscular arterial bulb, resemble the Teleostia, in having free branchim, covered by an operculum. The skeleton in this order is sometimes bony, sometimes cartilaginous; and the skull is more or less covered with bony dermal plates. In the second order, the Selachia, the skeleton is always cartilaginous, the gills are fixed, the water used in respiration passing off through a series of openings, corresponding in number to the gills, and the head is never covered by bony plates. In accordance with the views of Professor Owen, and many other naturalists, we have removed the Selachia (including the Sharks and Rays) to the head of the class, a position to which they are undoubtedly entitled, on account of the evident approach which they make, inmany important particulars, to the higher groups of the Vertebrata. This alteration has also necessitated the removal of the Ganoid fishes, which in any system must occupy a position intermediate between the Telvostia, or bony, and the Selachia, or cartilaginous fishes. Professor Miiller includes a sixth group (the Dipnoi) in the present class, for the reception of the Protopterus and Lepidosiren—singular animals, which appear to partake almost equally of the characters of this and the following class. It has, in fact, long been a matter of dispute in which of these great groups these curious creatures should be placed; and we have preferred arranging them amongst the Batrachia, as they agree with those animals in possessing lungs and a pervious nasal cavity. * Sub-classes of Miiller. 292 LAMPREYS. Onver I.—LeEptocarptia. This order includes only a single small fish, which rarely attains a length of two inches, but which presents so many remarkable characters that its title to a place in the vertebrate division of the Animal Kingdom has been disputed by some authors. This is the Amphioxus lanceolatus, a little, slender, transparent creature, which is found on sandy coasts in various parts of the world. Its body is of an elongated lanceolate form, with a narrow membranous border, running along the whole of the dorsal and a part of the ventral surface, and expanding at the caudal extremity into a lancet-shaped fin; which, however, is traversed by the tail itself. The vertebral cohimn is repre- sented by a gelatinous cord (chorda ‘dorsalis), which supports the axis of the nervous system ; the latter terminates anteriorly by a rounded extremity, without any signs of abrain. The head bears a pair of eyes, which are connected with the end ‘of the nervous axis by short filaments ; and between these is a small ciliated pit, apparently the first rudiment of an dhfaobuy organ. . . The mouth is placed at the front of the head, where it forms an oval opening, quite destitute of jaws, but surrounded by a number of cartilaginous points ; the oral cavity leads into a large branchial sac, at the hinder extremity of which is the entrance of the intestinal canal. By the action of cilia, with which these cavities are lined, currents are produced in the water ; and the water thus carried into the branchial sac, passing off through numerous slits in its walls into the general cavity of the body, whence it escapes by an opening in the ventral surface. The circulation of the blood is effected entirely by the contractile power of the arteries ; no trace of a muscular heart is to be detected in the transparent body of the creature. The blood itself, unlike that of all other Vertebrata, is perfectly colourless. Onver II.—Cyciostomata. General Characters.—The Cyclostomata still retain a good deal of the embryo- nic character so characteristic of the preceding order, although in their gencral organi- zation they exhibit a very great advance. They are of an elongated, cylindric, and somewhat worm-like form (Fig. 17), the skin is tough and quite destitute of scales, the pectoral and ventral fins are wanting, and the continuous fin, which runs round the posterior extremity of the body, contains scarcely any rays. The skeleton is cartilaginous, and con- sists simply of a dorsal cord and of a rudimentary skull, without any trace of ribs or other appendages. The mouth is destitute of jaws, and usually forms a cir- cular sucking cup, supported by a curious cartilage. The inner surface of the mouth is often armed with teeth. The branchie are in the form of little sacs, on the inner surface of which the blood-vessels ramify. These usually open externally by separate orifices. The circulation of the blood in the Cyclostomata is effected, as in all the remaining fishes, by means of a muscular heart, composed of two chambers. The orifice through which the blood passes from the ventricle into the branchial artery, is provided with a pair of semilunar valves, and the base of this vessel is not furnished with a muscular coat. Fig. 17.— Lamprey. LAMPREYS. 293 Divisions.—This order contains only two families. In the Myzxinide, the mouth is furnished with a number of cirri or tentacles, the lip bears a single tooth, and the tongue is sometimes armed with a few teeth. The eyes are completely concealed, and the nasal cavity opens into the mouth. These fishes appear to eat their way into the bodies of other fishes, in which they are often found by the fisherman. The best known species is the Myzxine glutinosa, called the Hag by the British fishermen. It was described by Linnus as a parasitic worm, and receives its specific name “ glutinosa’”’ from the immense quantity of mucus which it can give off from its skin, and which is said to be so great that if put into a vessel of water, it will, in a very short period, convert the whole of it into a glutinous mass, capable of being drawn out into threads, In the second family, the Petromyzonide, the mouth has the form ‘of a circular funnel, formed either of one or two lips. They are always destitute of cirti, but the inside of the mouth is usually armed with numerous teeth (Fig. 18). The nasal cavities never lead into the mouth, the eyes are usually well-formed, and there are generally seven branchial sacs, which open directly by a corresponding number of apertures along the sides of the body, whilst they communicate inter- nally with the pharynx by the intervention of a common canal. This family includes the various species of Lampreys, Z which generally inhabit fresh water, although some species pig, 18.—Mouth of the are found in the sea. They commonly adhere to stones in Lamprey. the water by means of their funnel-shaped mouth ; and are said also to attach themselves, by the same means, to the bodies of other fishes so as to feed at leisure upon their sub- stance, This statement, however, is very doubtful; and it appears more probable that the Lampreys derive their nourishment entirely from small aquatic animals. The Sea Lamprey (Petromyzon marinus) attains a length of three or four feet. It } quits the sea early in the spring, and proceeds up the larger ‘rivers for the purpose of [ spawning ; it is at this period that it is generally taken. In former days the Lamprey was regarded as a great delicacy ; and one of our English kings is said to have died in consequence of indulging too freely in a dish of these fish. ‘They have gone somewhat out of repute in the present day; but great numbers of the River Lamprey (P. fluviatilis) are'still taken in some parts of Germany, where they abound, packed in jars with vinegar, spices, and bay leaves, and exported to other countries. Some epicures have resorted to the ingenious expedient of drowning Lampreys in wine; a process which is sup- posed to give them a very superior flavour. Formerly the River Lamprey was very abundant in the Thames, and its capture formed a most important part of the business of the Thames fishermen. They were sold in great quantities to the Dutch, to be em- ployed as bait in the Turbot and Cod fisheries. Mr. Yarrell states that as many as four hundred thousand of these fish have been sold for this purpose in one season. Orver IT].—Trxzostia, General Characters.—The fishes of this order, which corresponds almost exactly with Cuvier’s great section of Osseous Fishes, must be regarded as the types of the class. They are all furnished with a perfect ,bony skeleton (Fig. 11), the structure of which has already: been described (page 10). “The skull is always of a very compli- cated structure, and composed of numerous bones; the gills are supported upon free bony arches, and the water passes away from them by a single aperture, protected by a 294 BONY FISHES. bony operculum or gillcover. The mouth is always formed by a pair of regular jaws, and usually armed with teeth. The arterial bulb, situated immediately in front of the ventricle of the heart . (Fig. 16), is always composed of the thickened walls of the vessel, and is never pro- vided with a muscular coat.. The only valves in this vessel are a pair placed at the point where it communicates with the heart. Maity of these Fishes have a perfectly naked skin, but the majority are covered with scales of various forms. These are generally of a horny consistency, and exhibit the two principal types of form already described (p. 14), as cycloid and etenoid. In some cases, however’, the surface of the body is covered with bony scales and plates, which sometimes unite so as to form a complete suit of bony armour, presenting a considerable resemblance to that of the Ganoid Fish, amongst which the fishes thus protected were actually placed by Agassiz. : We have already stated that, besides the pectoral and ventral fins, the represen- _ tatives of the anterior and posterior limbs, fishes are furnished with a series of perpen- dicular fins placed on the median line of the body, and denominated, according to their position, the dorsal, caudal, and anal fins (see p. 13, Fig. 14). The folds of skin of which these, as well as the pectoral and ventral fins, are composed, are extended by means of an appatatus of rays, which present themselves under two very distinct forms in the bony fishes—namely, as spines and soft rays. The former are simple, bony spines, tapering gradually to a point, They are generally stiff, and project, more or less, beyond the membranous part of the fin, so that, in some instanccs, they become dangerous weapons. The soft rays are also usually composed of bony matter; but instead of being composed of a single piece, like the spines, they are divided transversely into numerous short joints, and are also constantly dividing and subdividing longitudinally as they diverge from their point of insertion; so that, starting from the body as a single jointed ray, ' they become split up before reaching the margin of the fin into a bundle of smaller but similarly jointed branches. The soft rays are of universal occurrence throughout ' the series of bony fishes; the spiny rays occur in a great number, but are often absent. The spiny rays are to be found in all the fins except the caudal; they always occupy the anterior part of the fin, the remainder being composed of softrays. In some fishes, with two dorsal fins (such as the Perch, Figs. 11 and 22), the first dorsal is often entirely supported by spiny rays ; but in these cases we must consider the whole of the dorsal appendages as constituting one large fin. In some Fishes one or more of the spinous rays are completely separated from the fins, These are generally employed as weapons of offence and defence. The rays of the pectoral and ventral fins are, of course, articulated to the bones — 3 : ~ eee representing the anterior and posterior a ae roe TP ie torigifibae woes members, which, in fishes, are usually at te : entirely concealed within the skin. The | rays of the median or perpendicular fins articulate with a series of bones (Fig. 19), which are plunged into the median line of the body between the great longitudinal masses of muscles, and which, from their extremities passing in between the spinous processes of the vertebral column, have been denominated interspinous bones. Small SOFT-FINNED FISHES. 295 muscles, attached at one extremity to the interspinous bones, and at the other to the fin-rays, enable the fish to raise or depress the fin at pleasure. In some fishes a small, thick fin, without true rays, occurs behind the true dorsal fin; this is called the adipose fin. Divisions.—This order includes a vast majority of the living species of Fish ; and as the characters by which the genera and species are distinguished from each other are often by no means strongly marked, there are few groups of animals which present greater difficulties to the student than this. Itis divided into numerous families, which may, however, be distributed under six sub-orders, although these are some- times rather imperfectly defined. Sup-orpER I.—PHysosToMATa. General Charasters.—The fishes belonging to this group are usually furnished with a complete series of fins, which are always composed entirely of soft raya, with the exception of the first ray in the dorsal, anal, and pectoral fins, which are sometimes spinous. ‘he ventral fins are sometimes wanting; when present, they are always abdominal in position,—that is to say, they are situated on the ventral region, behind the pectorals. There is never more than one rayed dorsal fin; but behind this there is oceasionally a second adipose fin. The skin is sometimes naked, and sometimes more or less covered with bony plates; in most cases, however, it is thickly clothed with scales, which always exhibit the cycloid character. The air-bladder is always connected with the pharynx by a sort of duct,—a most important character, as it only occurs in these fishes amongst all the Zeleostia. -The Physostomata are exceedingly numerous, and inhabit both salt and fresh waters. They include amongst them some of the most important of the Fishes that are sought for by man as food; and also the only species of this order which possess electrical powers. 2% Divisions.—Professor Miiller divides the Physostomata into two principal groups, . the Apoda, in which the ventral fins are deficient, and the Addominalia, in which they | are piaced on the belly. The former—of which the common Eel is an example—are always soft-finned fishes, of an elon- gated, “snake-like form, which often want both pairs of members, and in which the median fins usually present the same embryonic form as in the Cyelostomata, except that they are supported by distinct rays. The head is covered with a thick skin, which leaves only a small branchial opening. Within this is a large sac, from which a second sac is given off; and it is to this arrangement that these fishes are indebted for their power of sup- porting a long separation from their native ele- ment. They live both in the sea and in fresh water, where they swim along with an undulating movement of the body; they aro exceedingly voracious animals. The Apodal Physostomata form three families. Of these, the best known are the Murenida, or Eels, of which several species are eaten in this and other countrics. They have the branchial apertures placed at the sides of the head, the intestine SSE ‘ Fig. 20.—Gymnotus electricus. 296 THE ELECTRICAL EEL. ‘without pyloric appendages, and the reproductive organs without efferent ducts. Many species of Hels constantly inhabit the ocean, whilst others usually live in fresh water, but migrate to the sea at particular periods, it is supposed to deposit their spawn. It isa very general belief that Eels are viviparous: but this is quite a mistake; and the opinion has, no doubt, taken its rise from the passage of intestinal worms through the anus. The marine species attain a large size, the common Conger of our coasts measuring sometimes as much as ten feet in length. In the Gymnotide, the maxillary bones take part in the formation of the margin of the upper jaw, ‘which is not the case in the Murenide. The branchial apparatus is situated as in the preceding family ; the intestine is furnished with pyloric appendages ; and the generative organs with efferent ducts. The dorsal fin is entirely wanting ; but the anal fin is very long, running from the anus, which is situated near the throat, to the hinder extremity of the body. 7 The most remarkable fish of this family is the Electrical Eel (Gymnotus Electricus, Fig. 20), which frequents the ponds and marshy places of South America. This fish possesses a most wonderful power of communicating an electrical shock to anything with which it comes in contact; and this is said to be sufficiently strong to knock down a man, and deprive him of the use of a limb for some hours. The Electrical Eels attain a length of five or six feet ; and, as the apparatus from which the electricity is evolved extends throughout the greater part of its body, it may readily be imagined that the discharge of such a battery must be a formidable affair. The apparatus is composed of four longitudinal bundles, placed one on each side of the dorsal and one on each side of the ventral region of the body. These bundles are composed of a multi- tude of horizontal parallel plates, which are intersected by transverse vertical plates, the quadrangular canals thus formed being filled with a gelatinous matter. The whole apparatus is liberally supplied with nerves, and may be considered’ to represent an exceedingly complicated galvanic battery. So powerful, in fact, is the current of electricity evolved by it that it can decompose chemical compounds, and magnetize steel needles. It appears that the anterior portion of the apparatus is positive, and the posterior negative ; and that those parts of it only which are in contact with an object are implicated in the production of the current. Nevertheless, it is said that the animal can make use of it in benumbing small fishes at some distance from it in the water. The Indians of South America, when they wish to capture this fish, commence their operations by driving a number of horses and mules into the ponds inhabited by them; the eels, alarmed at the disturbance, immediately attack the intruders upon their quiet domain, usually applying their entire length to the bellies of the unfortunate quadrupeds, and thus giving the full effect of the whole electrical apparatus. Some of the horses soon become disabled, and falling down in the water, are drowned; the others, being driven back by the shouts and whips of the Indians, continue the conflict until the powers of the Gymnoti are, for the time, exhausted. These then endeavour, in their turn, to escape from the scene of warfare, and for this purpose approach the shore, where another enemy awaits them: the Indians, armed with harpoons attached to long cords, strike at all that come within reach, and by jerking them rapidly out of the water, so as to keep the cord from getting wet, contrive to secure their booty without receiving any shock. Several other species of this family are found in the waters of ‘South America, but none of them appear to possess electrical properties. Mr. Wallace ‘found ten species in the small streams near the sources of the Rio Negro and Orinoco; he says that they are all eaten, but that, owing to the number of forked bones which THE HERRINGS. 297 they contain, they are but little esteemed. The Indians informed him that a rostrated species, common in those rivers, has a very singular and ingenious manner of obtaining its nourishment. They stated that its principal food consisted of ants and white ants, insects which are exceedingly abundant in those regions, and that, to procure them, it approached the shore and laid its tail upon the ground. The ants, attracted by the slimy matter with which this tempting morsel is covered, soon crawl thickly upon it, when the fish suddenly dives into the water, leaving its prey struggling on the surface, | from which it can pick them off at its leisure. The third family is that of the Symbranchide, in which the branchial apertures, « instead of being placed at the sides of the head, as in the two preceding families, unite to form a single opening, often divided by a longitudinal partition, in the throat. They are all inhabitants of tropical countries, and live in fresh water. Of the abdominal Physostomata, the first family contains only a single little blind fish, which is found in the subterranean caves of North America., The head is broad and rounded; the eyes completely covered by an opaque skin, or entirely absent; and the anus is situated on the throat in front of the pectoral fins. The young are brought forth alive. It forms the family Amblyopside. The fishes of the second family, the Clupeida, are always covered with large thin scales ; the mouth is wide, and both the maxillary and intermaxillary bones assist in the formation of the margin of the upper jaw. The dorsal fin is single, and there is no adipose fin. Most of them are furnished with pyloric cceca and air-bladders. This family includes some of the most important of all fishes, in an economical point of view. Of these the best known and most valuable is the Herring '(Clupea Harengus), which occurs in vast abundance upon our coasts, between the months of July and November, and, during this period, gives employment to multitudes of fisher- men and whole fleets of vessels. It has long been a generally received opinion that the Herring, when it disappears from the immediate neighbourhood of our coasts, undertakes a long migration to the Arctic Seas, where it is said to find an abundant nourishment in the vast swarms of minute Crustacea with which the waters of those seas are known to abound. This notion appears to rest principally upon the authority of Pennant, who particularly described the supposed line of migration, and states that the mass of Herrings, on their way_southwards towards their spawning grounds, meets its first obstruction at the Shetland Isles, which divide the army into two paris, of which one passes down the eastern and the other down the western shores of our islands. Unfortunately for this theory, however, it appears that the Herring, if not wholly unknown, is at least an exceedingly rare fish in the Arctic Seas, whilst, on the other hand, specimens may be taken at all seasons in the neighbourhood of the European coasts. ; From the statements of scveral observers, it appears certain that the Herrings inhabit the European seas at all seasons, keeping in deep water during the winter and spring months, and that the appearance of the vast shoals at particular epochs, which has given rise to the idea of their performing a long migration, is due only to their - seeking the shallow waters for the deposition of their spawn. During their migrations for this purpose they swim close to the surface of the water; and so enormous are the crowds of fish which thus, animated by a common impulse, swim together in the same direction, that the sea for miles exhibits a silvery appearance, from the glittering of their brilliant scales. The principal seat of the Herring fishery in this country is at Yarmouth, in 298 THE HERRING, PILCHARD, AND SPRAT. Norfolk; but it is also carried on at many other points of the coast. Some idea of its importance may be formed from the fact that, independently of the consumption in the fresh state, upwards of half a million of barrels of Herrings have been cured in this country in a year, and that in 1849 more than three hundred thousand barrels of these fishes were exported, valued at upwards of £320,000. The fishery is carried on principally at night. Several other species of the genus C/upea, are also of great importance as articles of food. Amongst these the Pilchard (Clupea Pilchardus), a fish which closely resembles the Herring, but is of a somewhat smaller size, probably holds the first rank. The Pilchard is found in the greatest abundance on the coasts of Cornwall, which it approaches in vast shoals about the beginning of July. It is taken, like the Herring, principally at night, by inclosing the shoal within a large perpendicular net, called a sean, of which one edge is supported at the surface of the water by means of cork buoys, whilst the other is carried to the bottom by leaden weights. According to Dr. Macculloch, “a single scan has been known to inclose at once as many as 4,200 hogs- heads (1200 tons) of fish! But this was the greatest quantity ever taken, and it is but seldom that as many as 1200 hogsheads are caught at atime.” From this prison the fish are removed at low water by means of a small net, technically denominated a tuck net; and, as they must not be carried to the shore in greater quantities than can ‘be managed by those who are engaged in curing them, it often requires several days to secure the whole of the fish captured by a successful “take.” The average annual produce of the Cornish Pilchard fisheries is said to be about 21,000 hogsheads, con- taining the enormous number of 60,000,000 fish ; and in particularly good seasons this quantity has been almost doubled. The Sprat (Clwpea Sprattus) is another species, which, although much smaller than the Herring, and by no means of the same commercial importance, yet, by its great abundance at particular seasons, furnishes an acceptable supply of cheap and agreeable food. The sprat-fishing commences in November ; and the fish are often taken in such vast quantities as to overstock the market; so that the fishermen are frequently com- pelled to sell them to the farmers, to be employed as manure. The White-bait (Clupea alba), in such great repute with London epicures, is another member of this genus. It was formerly regarded as the fry of some other fish, probably the Shad (C. alosa), a much larger species, which inhabits the same waters. There appears, however, to be no doubt that the White-bait is a distinct species, and that both it and the Shad are marine fish, which ascend our rivers for the purpose of depositing their spawn. The contrary opinion formerly prevailed; and there are still laws in existence prohibiting the capture of White-bait under pain of severe penalties. In the Mediterranean, the place of the Herring is taken by the Sardine (C. sardina), a fish which closely resembles the Pilchard; but is rather smaller in size. It is also taken in great abundance on the coasts of Brittany; and its flesh is regarded asa most delicate article of food. Another species of this family, very common in the Mediterrancan, and which is also found in considerable abundance in the English Channel, and on the coasts of ¥rance and Holland, is the Anchovy (Exgraulis encrasicolus), a small silvery fish, of about four or five inches in length. It is prepared for use after removing the head and intestines, and constitutes a well known condiment. The fishes of the third family, the Scopelide, present a considerable resemblance to the Salmons, and, like these, are furnished with a small adipose second dorsal fin. THE SALMON. 299 They differ, however, in the structure of their upper jaw, of which the biting edge is entirely composed of the intermaxillary bones. They are sometimes naked, sometimes covered with large, brilliant scales; the air bladder is usually wanting, andthe pylorus furnished with coeca, The Scopelide are found principally in salt water. Afew occur in the Mediterranean, but most of them inhabit the Tropical Seas. Some—such as Sternoptyz—present very singular forms. The great family of Salmonide, which includes some of the most esteemed of our ordinary edible fishes, agrces with the preceding in some respects, especially in the presence of an adipose dorsal fin; but the maxillary bone assists in the formation of the edge of the upper jaw, and the air bladder is always present. The pylorus is furnished with numerous coca; the skin is covered with cycloid scales. The Salmonide differ from most other bony fishes in the structure of the ovaries in the females. These organs form closed sacs, destitute of any oviduct, and the ova escape into the cavity of the body, whence they pass through an opening behind the anus. | ‘The fishes of this family in general furnish a highly-prized article of food. They are generally inhabitants of the fresh waters of the northern partsof the world, a few only, like the Salmon, passing a portion of their existence in the sea, and ascend- ing into the rivers during the spawning season. They are exceedingly active and voracious fishes, gencrally of a slender form, and adorned with brilliant colours, or elegantly spotted. They are usually of small or moderate size,—our common salmon being one of the largest species. This fish (the Salmo salar, Fig, 21), which is too well known to need description, inhabits the waters of Europe in great abundance; it usually attains a length of three or four feet, and a weight of twenty or thirty pounds. Larger individuals, weighing as much as fifty pounds, are occasionally taken ; and about thirty years ago, a Salmon of the extraordinary weight of eighty-three pounds was exhibited at a fishmonger’s shop in London. _ The ordinary weight of the Salmon brought to market, however, does not exceed ten or twelve pounds. During the summer, the Salmon usually in- habits the sea, but quits the salt-water in the course of the autumn, and commencesits ; journey up the rivers, in which it deposits its spawn. For this purpose it always endeavours to reach the small streams near the sources of the rivers; and in the attain- ment of this object there appear to be no obstacles which its perseverance and activity do not enable it to surmount, Cataracts and weirs of ten or twelve feet in height are cleared at a single leap ; and if unsuccessful in its first attempts at passing the barrier which opposes its upward progress, the fish trics again and again until success rewards its efforts. Arrived at its spawning ground, the Salmon prepares a furrow for the reception of its eggs, and these, when deposited, are carefully covered over with the gravel of the bottom of the stream. The fish remain in the rivers during the winter months, and commence their downward course with the first floods of spring. It has been observed that on quitting and veturning to the sea, they always remain for some days in the brackish water near the mouths of the rivers, apparently to accustom them- selves gradually to the change ; and it is said that during this interval they get rid of the parasites adhering to them ;—those which adhere to them in the fresh water being destroyed by contact with the salt clement, and vice versa, It is a generally received opinion that the Salmon always returns to the river in which it was spawned, and it is undoubtedly certain that fish purposely marked have been taken repeatedly on their way up their native rivers. Mr. Yarrell considers, however, that these statements are by no means to be received as expressing a positive certainty, for there is no doubt that some of 300 THE SALMON AND TROUT, > = Fig. 21.—Trour (Salmo fario), and Satmon (Salmo salar). the marked fish have been taken ascending rivers in the neighbourhood of that in which they were spawned. It,is, nevertheless, singular and unaccountable that after wander- ing for miles along the coast, so many of these fish should be able to find their way back to their native streams, the extent of their excursions being abundantly proved by the numbers which are taken in bays along the coast, at a distance from any considerable Salmon river. Itis said that, the stomachs of Salmon taken in fresh water are never found to contain any food, and hence many people have concluded that the fish do not feed at all during their sojourn in the rivers. It is certain that during their stay in fresh water the. fish fall off: greatly in condition, and that they are in their greatest perfection at the period of their commencing their ascent. In the sea they appear to feed principally ;upon small Crustacea, the remains of which are usually found in their stomachs, accompanied by a reddish matter which has been described as the spawn of an Echinus. “The young Salmon remain in the rivers until they attain about a foot in length, when they.descend to the sea. The principal European Salmon fisheries are at the mouths of the larger rivers in the British Islands; and of these the Tweed, the Tay, and the Severn fisheries are the most important. -The Thames was formerly much famed for Salmon, but in consequence THE SALMON AND TROUT. 301 Fig. 22.—Gray ine (Thymallus vulgaris), and Percu (Perca fluviatilis.) of the increasing impurity of the water, this fish has now become scarce in that river. A considerable number of Salmon are also taken on the Norwegian coast. Another species of Salmon (Salmo Rossii) is found in great abundance in the Arctic Sea, at the mouths of the rivers which fall into that ocean from the northern portion of the American continent. This fish occurs in such vast shoals, according to Dr. Richardson, its discoverer, that during one of the arctic expeditions as many as 3,378 were obtained at one haulofasmallscan. It is of a more slender form than the common Salmon; the under jaw is very long and projects considerably in front of the upper, and the scales are small, and separated from each other by a bare space of skin. The sides are adorned with numerous bright crimson spots. Several other species agree with the Salmon, in choosing the sea as their habitual residence, and ascending the rivers at. the spawning time; of these a well-known British species is the Salmon Trout (S. trutta). Of those which are confined to fresh water, one of the best known is the common Trout (S. fario, Fig. 21), which frequents most of the rivers and lakes of Europe, and is one of the fish most prized by the angler ; its caution rendering it very shy of taking a bait, whilst its great strength and activity make it by no means an easy task to land a good Trout when hooked. The 302 TUE PIKE. Trout is shorter and stouter than the Salmon; the colour of its back is a yellowish brown, passing to yellow on the sides, and silvery on tho belly; the back is spotted with reddish brown, and the sides with bright red. Several nearly allied species are found in the rivers and lakes of Europe, especially in mountainous countries. Of these, we need only mention the Char (8. salvelinus) and the Grayling (Thymallus vulgaris, Fig, 22), both of which occur in our own country. The Smelt (Osmerus eperlanus)also belongs to this family. Itis a small, semi-transparent, silyery.fish, which | resembles the salmon in its habits, keeping about the mouths of large rivers, which it ascends for the purpose of spawning. Close to the Salmonide Professor Miller places a small family, the Galaxiide, which he has established for the reception of a single gonus of fishes (Galazias), placed by Cuvier amongst the Esocide, or Pikes. They agree with the Salmons in their general structure, and in the mode in which the ova are excluded, and are distinguished prin- cipally by the absence of the adipose fin, and the want of scales. In the Esocide, the biting edge of the upper jaw is formed as in the Salmonida, both by the maxillary and intermaxillary bones; but the adipose fin and'the pyloric cceca ‘are wanting. The mouth is furnished with a most formidable apparatus of teeth ; almost all the bones which assist in the formation of that cavity being thus armed. All the known fishes of this family inhabit fresh waters, and only occur in tem- perate climates. They are of an elongated form, clothed with cycloid scales, and furnished with powerful fins, their whole conformation being eminently adapted for that rapid.motion through their native element, without which their yoracious propen- sities would stand but a poor chance of gratification. The only fish now placed in this family are the true Pikes (Zsoces), and a few small fishes forming the genus Umbra, of which one species isfound in the rivers of Austria. The Pikes, of which the common Pike (Hsov Jucius), of this country may be taken as an example, are amongst the most voracious of fresh-water fishes, seizing and devouring objects which at first sight would appear far too large even for their capacious mouths. Numerous anecdotes are related of the voracity of the Pike. No fish that they can swallow are safe fora moment in their neighbourhood, although it is said that the spiny back fin of the Perch often saves him from being gorged. Young Ducks are frequently dragged under by Pike ; and an instance is related of one of these fish having seized the head of a swan as the bird was in the act of dipping. Salter states that he has frequently known Pike seize upon the plummet with which some quiet bottom-fisher was taking the depth of his water; and in one case he succeeded in landing a fish of about two ‘pounds that had snapped at this indigestible bait. The Pike, when full grown, is a large fish, often attaining a weight of thirty or forty pounds; and individuals of double this weight have occasionally been taken. Its longevity is also very remarkable, if we may place implicit faith in a statement of Gesner, that a Pike was taken in the year 1497, in Suabia, with a ring attached to it, on which was an inscription, to the effect that the fish had been put into the lake in which it was found, bythe Emperor Frederick II., in the year 1230, or two hundred and sixty-seven years before its final capture. This patriarch of the lake is said to have measured nineteen feet in length, and its skeleton was long preserved at Manheim. Cuvier placed several other genera in this family, but these have been removed to other groups, with the exception of the genus Salanz, the position of which is still very doubtful. : Nearly allied to the Pikes is a small family of fishes, the Mormyrida, the members THE CARP. 303 of which have hitherto only been found in the Nile, and, according to Cuvier, in the Senegal. They resemble the Esocide in the form of the body and the position of the fins, and the maxillary bones assist in the formation of the edge of the upper jaw, but | the intermaxillary bones are completely united in front, so as to form a single bone, ; without any trace of suture—a structure which does not occur in any other fishes. The mouth is small, the arrangement of the teeth varies, and the pylorus is furnished with two coeca. The air-bladder is simple. The skin of the body is covered with scales, but the head is clothed with a thick, naked skin, which incloses the opercula, and | _only leaves a small perpendicular branchial aperture, presenting a considerable resemblance to a spiracle. The sides of the tail are thickened,. and contain a small electrical organ. The Mormyri of the Nile are reckoned amougst the best fish produced by that river. The great family of Cyprinide, or Carps, which includes the greater number of the fresh-water fishes of temperate climates, is distinguished by its small mouth and tooth- less jaws, of which the upper is entirely composed of the intermaxillary bones. To make up for the want of teeth in the mouth, the inferior pharyngeal bones are armed ' with very powerful teeth, which work against a singular process of the lower part of the skull, covered with horny plates. The body is usually compressed, and always clothed with scales, sometimes of very large, sometimes of very small size; the head is small; the dorsal fin is single, and there is no adipose fin, but in some cases the dorsal and anal fins have a single toothed spinous ray. The air-bladder is usually divided by a constriction into two parts, and communicates with the labyrinth of the ear by a series of small bones; the intestine is destitute of cceca. The fishes of this family are found in great abundance in all the fresh waters of Europe. Many of them are much sought after by anglers; but rather for the sake of sport than for the goodness of their flesh, which is usually watery and insipid. In former times, however, when the transportation of marine productions, in a fresh state, to great distances from the coast was attended with greater difficulties than in the present day, these fish were regarded as of some importance, especially as a change ' from the salt fish diet to which many good Catholics were condemned during Lent. The Cyprinide feed principally upon aquatic plants and worms; but a few of them seem occasionally to prey upon small fishes. One of the finest and best of the European species is the Carp (Cyprinus carpio), to the breeding of which in ponds great attention is still paid in many places, although in this country the abundant supply of sea fish has rather thrown it out of favour, except amongst anglers. Another fish belonging to this (family, which is a great favourite with the disciples of Walton, although its flesh is far inferior to that of the Carp, is the Barbel (Barbus vulgaris), It is one of the largest species, measuring sometimes as much as three feet in length, and is exceedingly abundant in all the larger rivers of this country. Its name appears to refer to the great length of the tentacles surrounding the mouth, which it possesses in com- mon with several other species of Cyprinide. These tentacles are also very long in the Loaches (Cobitzs), a group of small fishes belonging to this family. Many Cyprinide are distinguished by the beautiful silvery hue of their bodies ; they form the genus Lewciseus, of which the Roach (LZ. rutilus), the Dace (L. vulgaris), the Chab (Z. cephahis), and the Bleak (L. alburnus) are species well known to anglers. The scales of these fish, and especially those of the Bleak, are said to be employed in the manufacture of artificial pearls. The beautiful gold and silver Ash (Cyprinus auratus) of China, which are now completely naturalized in this country, also belong to this family. 204 THE SILURIDE. Nearly allied to the Cyprinide are two small families, the Peciliide and the Chara- cinide, The fishes of the former of these families resemble the Carps so closely in their general form and in the position of their fins, that they were formerly included with them in the same family. They differ from the Cyprinide, however, in having both jaws armed with numerous small teeth; the large pharyngeal tecth and the cranial plate of the Carps are replaced by teeth of the same form as those of the mouth ; and the air-bladder is simple, and presents no traces of the series of bones communicating with the ear. They are all small, scaly fish, inhabiting the fresh waters of warm climates. In some of them the oviduct is dilated into a sac, in which the eggs are retained until the young are hatched, so that the fish brings forth living young. In some curious little fish belonging to this family, forming the genus Anableps, the cornea and iris of each eye are divided into two parts by transverse bands, which give the creature the appearance of having four eyes, although all the inner portions of the eye are single. The best known species is the Anadbleps tetrophthalmus, or Four-eyed Loach, « native of the rivers of Guiana. The Characinide appear to be intermediate between the Cyprinide and Salmonide, with the latter of which they were placed by Cuvier. Like these, they have usually a small adipose fin on the back behind the true dorsal fin ; the upper jaw is composed of the maxillary and intermaxillary bones, and the jaws are usually furnished with teeth ; and the pyloric cceca are numerous ; but the ovaries are provided with continuous ovi- ducts, and the air-bladder is divided into two parts, and communicates by a series of bones with the auditory organs. These fishes are found in the rivers and lakes of tropical countries, where some of them attain a considerable size. A few are very voracious ; the Serrasalmones of the South American rivers are said to seize upon water- fowl, and even to attack men when bathing in the rivers. This sub-order is closed by the curious family Siluride, including fresh-water fishes, usually of considerable size, of which the skin is cither naked or more or less covered with bony plates, especially about the head. The mouth is usually furnished with teeth, and always surrounded by tentacles ; the edge of the upper jaw is formed entirely by the intermaxillary bones, and the opercula are formed only of three pieces. All the fishes of this family possess an air-bladder, which is connected with the ear by a series of small bones. The first ray of the pectoral fins is usually converted into a strong spine, which constitutes a formidable weapon; and the wounds inflicted by this have often been considered venomous, although apparently without any sufficient foundation. The dorsal fin is often very large; but in some species the rayed dorsal is entirely deficient, and its place is supplied by an adipose fin. These fishes are, for the most part, confined to the rivers and lakes of tropical climates; only a single species (Silurus glanis) is found in the European waters, but this often attains a length of from six to eight feet, and weighs several hundred-weight. They swim slowly, and appear to take their prey by concealing themselves in the mud and lying in wait for the approach of any unlucky fish—a proceeding which is greatly favoured by their dark colour. A species inhabiting the rivers of Africa, especially the Nile and the Senegal, the Malapterurus electricus, which attains a length of twelve or fifteen inches, is remarkable from its possessing electrical properties, although in a comparatively slight degree. Some nearly allied species inhabiting South America, which have the whole body covered with an armour of bony plates, and in which the air-bladder, with its series of bones, is entirely wanting, have been formed into a distinct family under the name of Loricariida. THE ANACANTHINA, OR SPINELESS FISHES. 305 Sus-Orper II.—ANAcaNnTHINA. General Characters.—The sub-order of Anacanthina, or spineless fishes, presents a considerable resemblance to the preceding group; the fins are entirely supported upon soft rays, and even the single spine, which occasionally occurs in some of the fins of the Physostomatous fishes, is wanting here. Like the Physostomata, these fishes are also divisible into two groups, characterized by the presence or absence of the ¥entral fins ; but these organs, when present, are always placed on the chest or throat, and supportéd by the same bony arch which bears the:pectoral fins. They also present an important difference in the structure of the air-bladder, which, instead of communicating with the oesophagus by a duct, as is the case in the Physostomata, is here completely closed; and, as a general rule, the duct, which exists in the embryo, has entirely disappeared, so that there is no connection between the anterior part of the air-bladder and the cesophagus. The inferior pharyngeal bones are always separated. Divisions.—The Anacanthina constitute four families, of which two are destitute of ventral fins (Apoda), whilst the others have these organs placed in the neighbourhood of the pectorals (Sudbrachiata). The apodal species usually agree very closely with the Eels, not only in the absence of the ventral, and sometimes of the pectoral fins, but also in the general form of the body, which is elongated, and often serpentiform ; they may, however, always be distinguished from the apodal Physostomata by the greater freedom of the opercular apparatus, which is never inclosed in a thick skin, as in the eels. The first family, the Ammodytide, is further distinguished from the Eels by the form of the caudal fin, which is well developed, distinct from the dorsal and anal, and con- siderably forked at the extremity. The skin is naked, but of a beautiful silvery lustre ; the dorsal fin commences a little behind the head, and runs nearly to the root of the caudal fin; the anal fin extends about a third, or one half, the length of the body ; and both the dorsal and anal are supported upon soft, but simple rays. There are two British species, which are much used by the fishermen as baits for other fish. They are known by the names of Sand-lances, or Sand-eels, from their habit of burying themselves in the sand, to a depth of six or seven inches, during the ebb of the tide, generally selecting for this purpose those parts of the beach which are left dry at low water; itis in this position that they are generally taken by the fishermen, who rake them out by means of iron hooks and rakes. The largest British species (Ammodytes Tobianus) usuaily measures about a foot in length; the smaller one (4. Zancea) only five or six inches. In the Ophidiide the ee]-iike form makes its appearance with still greater distinct- ness: as in the Eels, the median fins 2te continuous, forming a border round the hinder extremity of the body ; the caudal fin is rownded or pointed, but never forked, and the pectoral fins are sometimes wanting. The body is gc™etimes naked, sometimes covered with minute scales imbedded in the skin ; the anus is situaic’ Sometimes in the middle of the body, sometimes under the throat; and the air-bladder is asw2V8 present, and quite destitute of a duct. These are generally small fishes, inhabiting ony the sea; several species are found in the Mediterranean, and two or three have occurred upon the British coasts. The Subbrachiate Anacanthina, or those with ventral fins attached to the breast or throat, include two families of fishes which are of the greatest importance as articles of food—the Gadide, or Cod family, and the Pleuronectida, or Flat-fishes. po 306 THE COD, Tn the former the body is of an elongated spindle-shape (Fig. 5), produced behind into a long tail; the skin is usually furnished with very small soft scales, which are entirely inclosed in separate sacs ; the median fins are of vety latge size, and usually divided into several portions; the mouth is wide, furnished with numerous sinall téeth, and the margin of the upper jaw ia entirely formed by the intermaxillary toned. The lower jaw igfrequently farnished with a single citris, or beard, beneath its extremity, and the nose sometimes bears one or two pairs of similat appendages ; the ventral fihs, also, are sometimes reduced to a single ray, so as to acquire the appearance, as they no doubt perform the office, of cirri; and these in some species (such as the Forked Hake —Phycis furcatus—of our own coasts) are of considerable length, and give off a branch from about their middle, which is sometimes longer than the main stalk. The Gadide aré active and exceedingly voracious fishes, feeding indisctiminately upon almost all the smaller aquatic animals. Mr. Yartell states, that “Mr. Couch has taken thirty-five crabs, none less than the size of a half-crown piece, ftom the stomach of one Cod.” They are nearly all marine; their flesh is exceedingly firm and well- flavoured ; and as many of the species occur in the greatest profusion, their importance, in furnishing an abundant supply of agrecable and nutritious food to the human zace, is almost incalculable. The principal species found in our markets are the Cod (Morrhua vulgaris), the Haddock (If. aglefinus), the Whiting (Merlangus vulgaris), and the Ling (Lota mova) ; but many others are taken on various parts of the coast, although they rarély find their way to London. These fishes are all taken by hook and line, baited with common Mollusca, such as limpets, whelks, &c., or with pieces of fish. For the deep-sea fishing very long lines are used; these are fixed to the bdttom by means of a small anchor, the other end being supported by a budy, and the hooks are placed at the extremities of short lines, usually about six fect in length, attached at intervals to the main line. The long lines are usually left for about six hours, or for a whole tide, when they are taken up and examined. In the interval the fishermen are not idle ; they carry on the work of destructio# by means of hand-lines, of which each man manages a pair. In this manner an immense quantity of these and other valuable fish are taken at almost all parts of the British coasts. Mr. Yarrell states, that “from four hundred to five hundred and fifty cod-fish have been catight on the banks of New- foundland in ten or eleven hours by one man,” and mentions that he was informed br, a master of fishing-vessels for the London market, “ that eight men, fishing unzer his: orders off the Doggerbank, in twenty-five fathoms water, have taken ei Sty score cod in one day.” Besides the consumption in a fresh state, several species + this family are commonly preserved by drying, either with or without salt * of these, the most important are Cod, Haddock, and Ling. In spite of the enormous consum” oti constantly going on, the numbers of these fish do not appear to decrease: ~ 4 this, perhaps, is the less to be wondered at, when we consider that the re of a single female Cod has been found to contain no fewer than evwy in the spring; they are full of roe, and in their greatest perfection during the early winter months. a parts of the world; the common Cod is distributed from Iceland ‘to the ‘coasts of Spain, without entering thé, Mediterranean, and most of the other species abound especially in 3 : é nine ni cas ‘of ova, Their general spawning time appears to be the winter, or very | The species of Gadide appear to be principally confined to the seas of the northern northern latitudes, One species, the Burbot (Lota vidgaris), nearly allied to the Ling, © THE FLAT-FISHES. 307 is found in the rivers and lakes of several countries of Europe and Asia, It is of an elongated form, and presents considerable resemblance to the Eel in its habits, from which circumstance it is called the Eelpout in some places. It inhabits a few English rivers, but is not generally known, although its flesh is said to be most excellent. The family of Pleuronectide, or Flatfish, which concludes the present sub-order, consists of numerous fishes, which, in their general appearance, are remarkably different from those of the preceding groups, and indeed from all other fishes. They have a broad, flat body, margined almost throughout by long dorsal and anal fins; the head is — singularly twisted, so that the eyes are both brought to one side of the body, and this, which is always uppermost, is usually of a dark colour, and often spotted, whilst the opposite side is always white. These surfaces are often regarded as the back and belly of the fish, but incorrectly ; the gill openings and the paired fins being situated on both surfaces, the pectorals a little behind the apertures of the gills, and the ven- trals in front of these on the throat (Fig. 23). The abdominal cavity is very small, and the anus opens under the throat, so that, as remarked by Professor Vogt, the whole body is nothing but an exceedingly compressed, disc-like tail. The mouth is small, and armed with small teeth, and in most species the skin is covered with ctenoid scales. The Flatfishes swim with the.dark side uppermost, and-with a sort of undulating motion of the whole body ; they generally keep close to the bottom of the water, where they feed upon small fishes, mollusca, worms, crustacea, &c. Some species attain a large size; the Holibut (Hippoglossus vulgaris) is said sometimes to weigh as much as five tyandeed pounds; and a specimen measuring “seven feet. six inches inlength, three feet six inches in breadth, and weighing three hundred and twenty pounds, was taken (in April, 1828) off the Tile of Man, and sent to Edinburgh market ”—(Yarrell). The Turbot (Rhombus maximus), which is regarded as the finest fish of this family, does not appear to reach quite such gigantic dimensions; the largest recorded by Mr. Yarrell weighed one hundred and ninety pounds, and measured six feet across. These fish are caught either by means of hooks and lines or by the trawl-net ; the for- mer method is employed. during the warmer months of theyear. The species most esteemed are the Turbot and the Sole (Solea vulgaris) ; but several others, although inferior in the quality of their flesh, are of great importance, as they are caught in such numbers that they can be sold at.a very cheap rate. Of these the best known are the Plaice (Platessa vulgaris, Fig. 23), the Brill (Rhombus vulgaris), and the Flounder (Platessa,flesus). All the Pleuronectide are inhabitants of the sea, although they sometimes ascend the brackish waters of tidal rivers; and the Flounder.even appears capable of thriving in perfectly fresh water. They are rather voracious fishes; and, in spite of their singular form, are often very active in their habits. They conclude the sub-order Anacanthina. Fig. 23.—The Plaice (Platessa vulgaris). 308 FLYING-FISHES. Sus-Orver IJI.—PHaryNncoGnatua. General Characters.—This sub-order includes an assemblage of fishes which undoubtedly present a very great diversity of form, and in which we not only meet with species in which all the fins are supported upon soft rays, but also with others which possess spinous rays as strong and well developed as those of any fishes belonging to the remaining groups. The principal character which serves to unite the Pharyngognatha is derived from the structure of the inferior pharyngeal bones, which, in all the fishes of this sub-order, are completely coalescent, so as to form a single bone, which is usually armed with teeth. So complete is the union in most cases, that no trace of the original separation of the bones can be discovered. In other respects, it must be confessed that the fishes referred to this order present but few characters in common; the fins, as already stated, are sometimes entirely composed of soft rays (Malacopterygii, Miiller), sometimes partially spinous (Acanthopterygii, Miller) ; the ventral fins are sometimes placed on the belly, sometimes on the chest or throat, and the scales are cyloid in some species, ctenoid in others. The air-bladder is always completely closed. Divisions.—Professor Miiller divides the Pharyngognatha into two groups, for which he adopts the names of Malacopterygii and Acanthopterygit, proposed by Cuvier for his primary divisions of osseous fishes. The former group, including the soft- finned species, contains only a single small family, the Scomberesocide, so called from the mingled resemblance which the fishes composing it appear to bear to the Scomberes, or Mackerels, and the Esoces, or Pikes. They are usually of an elongated form, and clothed with cycloid scales. The dorsal and anal fins are placed far back, and a series of small fins often inter- venes between these and thecaudalfin; the ventral fins are placed on the ab- domen, and the pectorals usually removed far back, and often of considerable size. In the true Flying- fishes (Exocetus), which Fig. 24.—Belone vulgaris. belong to this family, the pectoral fins attain a great length, and possess sufficient force to serve the fishes as wings, upon which these creatures can rise from the water, aud support themselves in the air for a considcrable space. One species of flying fish, the Exocetus exiliens, inhabits the Mediterranean, and has been found dead on the south coast of England ; a second smaller species is found in the ocean, especially in the tropical parts of the world. The flying fishes exhibit a good deal of the form of the Herring, and, like it, are covered with tolerably large scales; but in the typical species of the family the body is very long, and the texture of the surface resembles that of the Mackerel. These also present the conformation of the jaws which has led to their comparison with the Pike, and even to their being included amongst the Esocide by many ichthyologists. The jaws are much produced, forming a slender snout, not unlike that of the Gangetic THE GARFISH—THE WRASSES. 309 Crocodile, and are often armed with strong teeth. In the genus Hemiramphus the lower jaw only is produced in this manner ; hence these fishes have received the name of the Under Swordyish. The fishes of this family inhabit the sca exclusively ; and several species are taken on our coasts, where they are commonly known by the names of Garfish, Sea-pike, Sea- needle, &c. The commonest species, Belone vulgaris (Fig. 24) is sometimes called the Mackerel-guide, from its generally preceding the shoals of Mackerel when they visit the shallows for the purpose of spawning; it is also denominated Green-bone in some places. It, and its allies, are but little esteemed as food, although they may occasionally be seen even in the shops of the London fishmongers. The Acanthopterygious, or spiny-finned division of this sub-order, is characterized by the possession of a single long dorsal fin, of which the anterior portion is spinous, the posterior supported only on soft rays. Near the extremity of each of the spinous rays there is usually a small membranous appendage ; and the ventral fins are generally placed upon the breast or throat. Most of them are handsome fishes, frequently most beautifully variegated with brilliant colours; and some are remarkable for the eccen- tricity of their forms. They form three families. The Chromide are characterized by their fleshy lips, and by their interrupted lateral line, the anterior portion of which terminates about the middle of the. body, whilst the posterior portion commences where this disappears, but at some distance below it. The greater part of the dorsal fin is spinous, and the spines are usually furnished with membranous appendages ; the head and body are covered with ctenoid scales; the edge of the preoperculum is almost always smooth ; the inferior pharyngeals are united by w suture; and the laminw of the fourth branchial arch are of equal length. The ‘ stomach has a coecum, but the pyloric cceca are wanting. The Chromide generally inhabit the fresh waters of warm climates. One small species is caught in great quantities in the Mediterranean ; and another, which inhabits the Nile, and attains a length of two feet, is regarded as one of the best fishes to be found in Egypt. The Pomacentrida resemble the Chromide in their general form, and, like these, are principally found in hot climates; but they are exclusively inhabitants of the sea. They have the ctenoid scales and interrupted lateral line of the fishes of the preceding ‘family, but are destitute of the fleshy lips, and of the appendages to the spiny rays of the dorsal fin, The inferior pharyngeal bones, also, are completely fused together ; the ‘fourth branchial arch has two rows of unequal lamine; and the preoperculum is usually toothed, or even armed with spines. The stomach is furnished with a cecum, and the intestines with pyloric appendages. In the third family, the Ladride, the fleshy lips again make their appearance, and the body is clothed with large cycloid scales; the lateral line is uninterrupted. The mouth is protrusible, and armed with formidable teeth in the jaws; the palate is unarmed, but the lower pharyngeal bones, which, as in the preceding family, are com- pletely coalescent, are furnished with broad grinders. In some species (such as those of the genus Scarus), the jaws are formed into a sort of beak, which is covered with a modification of the teeth, giving them in some cases a very close resemblance to the beak of a parrot, whence some of these fishes are denominated Parrot-fishes. The fourth branchial arch has only a single series of laming, the stomach is simple, and the pyloric cceca are wanting. . The Labride are distributed in the seas of most parts of the world; they are gene- 310 THE WRASSES rally of moderate size, of a stout and somewhat compressed form, and in many instanees adorned with the moat beautiful colours. Some of our British species scarcely yield in this respect to those of the tropical seas. They are known by different names on different parts of the coast —Wrasse, Rock-fish, &c. In some places they are ealled Old Wives, and the French give them a simi- lar mame. The species here figured, the Za- brus maculatus, or Ballan Wrasse (Fig. 25), is a common British species, which attains a length of about eighteen inches, and varies greatly in its colour; being sometimes blue or green, spotted with orange, sometimes entirely of different shades of the latter colour. One of the most beautiful species is the Blue-striped Urasse (ZL. variegatus), of which the general colour is orange, becoming reddish on the back, yellow on the belly ; the sides are striped with blue; the anterior portion of the dorsal fin is blue, edged with orange, and the hinder part orange, with {blue spots. The remaining fins are orange, with blue edges. The Labride generally keep amongst rocks, where they conceal themselves under the seaweed, and feed upon the crustaceous animals which they find in abundance in such situations. Most of them bite very readily, and are often captured by baits intended for other and more valuable fish ; for the Wrasses, although so splendid in their external appearance, are regarded as but indifferent food. When caught, they are generally cut up and used as bait for other fishes. In the British Seas they spawn in April, and the young are often to be seen in profusion about the rocks during the summer. Some of the Mediterranean species are said to spawn twice in the year. Fig, 25.—Labrus maculatus. Suz-orper IV.—AcanrHorrera. General Characters.—This sub-order includes those of the Acanthopterygii, or Spiny-finned Fishes of Cuvier, which have the inferior pharyngeal bones distinctly separated. The rays of the first dorsal fin are always spinous, and the first rays of the remaining fins (with the exception of the caudal) are often of the same structure. The membranous portion of the first dorsal fin is sometimes wholly or partially deficient, when the spinous rays stand freely on the back, and constitute formidable defensive weapons. The ventral fins are almost always situated in the neighbourhood of the pectorals on the breast or throat; the bones forming the upper jaw are free and moveable, and the air-bladder, when present, is completely closed. Divisions.—The number of fishes belonging to this sub-order, which may be regarded as the most typical of the class, is exceedingly great, greater perhaps than in any other of the equivalent groups; the families, also, as might be expected, are rather numerous, and present a considerable diversity of structure. The first of these is rendered remarkable by the form assumed by the heads of the THE AULOSTOMIDE, OR SEA SNIPES. 311 and the second soft dorsal fishes composing it,—the bones of the face and some of those of the head being drawn out into a longish tube, at the extremity of which is the opening of the mouth, which is very small, and composed of the usual maxillary and mandibular bones (Fig. 26). Hence the names of Sea Snipes, Trumpet Fishes, Bellows Fishes, &c., applied to these animals; and the scientific name of the family, Awlostomide, alse refers to the game peculiarity of structure. The skin ig sometimes naked, and sometimes clothed with small ctenoid scales, and in one genus (Amphisyle) the hack is covered with large scaly plates. : In one genus the spiny fin-rays are entirely wanting, and the yentral fins are always placed upon the belly, indicating a certain approach to the Physos- toma. The first dorsal fin is sometimes repre- sented only by a series of small spines running along the back of the animal, is placed far back, close to the tail; in other cases (Fig. 26), the first ray of the dorsal is produced into a long spine, which is generally placed on the back of the Fig. 26.—Sea Snipe (Centriseus scolopaz). animal, but in the genus Amphisyle, already referred to, this spine forms the actual | hinder extremity of the animal, projecting backwards in the same line as the axis of the body, and haying the second dorsal and the true caudal fin in front of it, on the lower surface of the fish. i These fishes are, for the most part, inhabitants of the seas of warm climates. The species figured -above, the Centriscus seolopax, is found in the Mediterranean, the most northern locality regularly inhabited by any fish of this family, although a single specimen has been cast ashore on the coast of Cornwall. It is about four or five inches long, reddish on the hack and sides, and silvery on the belly, with more or less ) of a. golden tinge. In others, principally inhabiting the eastern seas, the body is elongated and cylindrical; one of these, the Fistularia tabacaria, attains a length of three feet. The second family of spiny-finned fishes, the Triglide, or Cataphracta, is charac- terized by having the series of dermal bones which occupy the lower portion of the orbit (the %nfra-orbitals) greatly expanded and coalescent, forming bony plates which cover ithe cheeks and articulate with the preoperculum. ‘The head is also usually more or less armed with spines and other angular prominences, or furnished with mem- branous appendages, which not unfrequently give these fishes a most singular appear- ance. The fins are generally greatly developed ; the dorsal is sometimes separated into two distinct fins, and sometimes forms a single continuous fin, of which the anterior | portion is spinous, the posterior soft. In some cases, as in the common Sticklebacks (Gasterosteus), the membranous portion of the first or spinous dorsal is wanting, and the rays form a more or less numerous series of acute spines on the back of the fish. ‘The pectoral fins are always of large size, sometimes remarkably developed, as in the genus Dactyloptera (Fig. 27), where they attain such a length as to enable the animal | to support itself in the air fora. short time. Hence these fishes are commonly known 312 THE GURNARDS. as flying fish; one species is common in the Mediterranean. In the common Gurnards (Trigla), which we so often see in the fishmongers’ shops, the pectoral fins are also of considerable size, and the three first rays of each are destitute of membrane, and separated from the rest of the fin, so as to form cirri or Fig. 27.-Dnoryloplarn Meat tentacles. The ventral fins . . Yyloptera Mediterranea. are usually of small or mo- derate size, and placed on the breast beneath the pectorals; in the Sticklebacks, they are replaced by a single strong spine on each side, which constitutes a powerful offensive weapon for these pugnacious little creatures. The skin is rarely naked, usually covered with small ctenoid scales. In the Stickle- backs, and some other genera, the scales are replaced by bony plates (Fig. 28). The majority of these fishes are inhabitants of the sea; only a few species of the genera Gasterosteus, or Sticklebacks, and Cottus, or Bull-heads, being found in fresh water. The best known species are the Gurnards (Zrigle), of which several species are taken round the British coasts. Of these the commonestisthe Sapphirine Gurnard (7. Airundo), which may often be seen in the shops with its broad pectoral fins skewered in a most ludicrous manner over its large angular head. It is the largest of the British species, occasionally measuring two feet in length, and its flesh is considered to be very good. The Gurnards generally inhabit deep water, from which they are’ taken by the trawl net; they may also be caught by line fishing. The Bull-hcads (Cottus), of which several species inhabit the European seas, and one of which is found commonly in our fresh waters, are remarkable for the large size of their heads, which are frequently armed with spines in a most formidable manner. A nearly allied species, the Aspidophorus europaeus (Fig. 28), is completely covered with bony plates. The Sea Scorpions (Scor- peng) and some allied ) genera, perhaps present Fig. 28.—The armed Bull-head (Aspidophorus europeus). the most singular appear- ance of any fishes, their heads being not only armed with spines and angular projec- tions of the most remarkable form, but also frequently furnished with curious membranous lobes and filaments. But the most interesting species of this family, as regards their habits, are the Sticklebacks, of which several are found abundantly in our fresh waters. They are small fishes, measuring from two to three inches in length. ‘The sides are more or less covered with bony plates; and those parts of the skin which are not thus protected, are quite free from scales. These little creatures present almost’ the nly’ known instance amongst fishes in which the parents take any ‘farther care of their ‘offspring than that of depositing their ova in a suitable place, the young fry’ being ‘usually left to shift for themselves as scon as they TUE STICKLEBACKS. 313 are excluded. The Stickleback, on the contrary, seems to approach the birds in the attention which it pays to the protection of its young from danger. About the time of oviposition, the male takes possession of some particular spot in the pond which he inhabits, and this he defends with the greatest pertinacity, attack- ing all intruders on his domain with great fury, and endeavouring to wound them with the ventral spines. According to an observer quoted by Mr. Yarrell, he even sometimes succeeds in ripping up and destroying his opponent by means of these formidable weapons. The object of all this exertion soon becomes apparent; the fish begins to collect small fragments of vegetable matter, with which he forms a sort of nest. In this the female deposits her spawn, and it seems not improbable that during the operation of nest-building, the male fish endues the materials of his nest with the milt, as he is observed to pass frequently over the nest whilst in progress, apparently exuding a glutinous matter at each time of his so doing. Be this as it may, after the deposition of the ova, the male still keeps watch over his treasure, attacking all intruders with the same ferocity as before. Nor does his care cease when the young fry are evolved: he still continues to watch, and carries back any incautious straggler to the security of the nest. It is very singular that in every case it is the male that takes upon himself all the duties of nidification.* The Gasterosteus spinachia, or Fifteen-spined Stickleback, a marine species which is not uncommon round our coasts, also forms a nest for its ova. The common Stickle- back (@. trachwrus), which has three spines on the back, and bony plates along the whole length of its sides, is found both in salt and fresh water. It is found in the sluggish streams and pools of the Lincolnshire fens in such vast quantities that it is occasionally employed as manure; and Pennant tells us that at Spalding, in that county, a man has been known to make as much as four shillings a day by selling Sticklebacks at a halfpenny a bushel. The vast family of the Perches, or Percide, of which the common Perch may be taken as the type, is distinguished from the preceding by the free- dom and small size of the infra- orbital bones in the fishes of which it is composed. The mouth is large, and the jaws, vomer, and palatine bones are armed with numerous small teeth, amongst which «a few longer fangs are often present. The head is generally free from those angles and spines which give so many of the Cataphracta such , . : a esha appearance, but the i a a edges of the opercula and preenerealy are usually toothed or even armed with spines; and if either of these bones be smooth at the margin the other is always toothed. The fins are well-developed ; the dorsal fin is sometimes continuous (Fig. 29), sometimes divided into two parts; the ventrals are placed either on the breast or throat. The skin is clothed » Very interesting accounts of the habits of the Stickleback during the breeding season, by Mr. Hancock and Mr. Warrington, will be found in ‘¢ The Annals of Natural History,” for October, 1852. 314 THE PERCHES. with ctenoid scales, the free surface of which is often beset with spiny processes. The ra rays are generally seven in number, sometimes more, but very rarely ewer. The Percidew are generally handsome fishes, often of considerable size and of beautiful colours. They abound in the seas of all parts of the world; and some species also, like the common Perch, are inhabitants of fresh water. The Perch (Perea fluviatilis, Figs, 11 and 22), which is the best known species of the family, is a very common denizen of almost every piece of clear fresh water. It is one of the best and handsomest of our fresh-water fishes. Its body is broad and compressed; the back haa two dorsal fins, of which the anterior is supported upon stiff, sharp, spinous rays, which are said to serve as a defence even against the voracity of the Pike. The colour of the upper part of the body is greenish-brown, gradually passing to a golden yellowish-white on the belly ; and the sides are adorned with from five ta seven broad blackish bands; the doraal and pectoral fins are brownish, and the ventral, anal, and caudal fins of a bright vermilion colour, which adds greatly to the liveliness of the fish’s appearance. The Perch does not usually attain a large size, one of three or four pounds being considered a heavy fish ; but a few instances of the capture of Perch twice this weight are on record, and Pennant mentions his having heard of a specimen, taken in the Serpentine, which weighed nine pounds. As the Perch bites freely, it is much sought after, especially by young anglers ; and its flesh when taken is exceedingly good. Like the other spegies of the family, it is an exceedingly voracious fish, feeding indiscriminately upon any animal it can master, especially worms, insects, and small fishes. It is very tenacious of life, and will live for a considerable time out of the water. Mr, Yarrell states that in Catholic countries it is a common practice to bring the Perch to market alive, when, if not sold, they are returned to the ponds from which they were taken, to remain there until they are again wanted. Another fresh water species, the Sander (Lucioperca sandra), is common in Germany and the east of Europe. It is of a much more elongated form than the Perch, and attains a length of three or four feet; its flesh is considered excellent. A small species, nearly resembling the Perch in its general form, but having a continuous dorsal fin, is found in almost all the rivers of this country. This is the Ruffe (Acerina vulgaris) ; it rarely exceeds seven or eight inches in length, but its flesh is sald ta be yery good, Of the marine species very few are found in the British seas. The best known of these is the Basse (Labraw Iupus), sometimes called the Sea Perch, which is found in considerable abundance round the gouthern coasts of our islands. It is usually from twelve to eighteen inches in length, but it is said occasionally to attain a much larger size. Itis highly esteemed as an article of food. The Bass is exceedingly abundant in the Mediterranean, which is also inhabited by several other fishes of this family, some of them of large size. We have separated from the Percide of Professor Mijller the three following small families, as they appear to possess characters of sufficient value to justify such a proceeding. The Trachinide, known in England as the Weevers, have two dorsal fins, of which the anterior is small but very strongly spinous; the ventral fins are situated in front of the pectorals on the throat; and instead of the rough ctenoid seales of the true Perches, the skin is covered with smooth cycloid scales. They are generally of an elongated form, with a broad head, on which the eyes are placed in such a manner as to look more or less upwards’; in fact one genus has received the name of Uranoscopus, or Star- THE RED MULLET. 315 gazer, from this circumstance. The second dorsal and anal fins are of nearly equal length, and occupy the greater part of the upper and lower surfaces of the body; the anus is thrown very far forwards. They have no air-bladder. The strong spines with which the first dorsal fin and the opercula of these fishes are armed, enable them to inflict severe wounds upon those who handle them incautiously, and the effects of these wounds are so exceedingly painful, that there is a general belief amongst the fishermen that the species possess some venomous property. Two species are found in the British seas, the largest of which, the Trachinus draco, attains a length of twelve or eighteen inches. They appear to prefer deep water, and are very voracious in their habits. They live for a considerable time after being taken out of the water; and the flesh, at least that of the larger, species, is highly esteemed. A second small family, which is still included with the Percide by many authors, is composed of the Mullets (Muiiide). They agree with the Perches in the position of their fins; but the opereular bones are entirely unarmed, and the branchiostegal mem- brane has only four rays. The scales are very large, and readily fall off; their hinder margins have scarcely any indications of the ctenoid structure. In most of the species the under jaw is furnished with cirri. A well-known example of this group is the common Red Mullet (Mrdlus surmulletus) , which ‘is often taken in considerable plenty off the British coasts. The Mullet, although comparatively a small fish, is in high esteem; its flesh is white, firm, well- flavoured, and easy of digestion. Amongst the epicures of ancient Rome its reputation stood very high, and large sums were often paid by them for particularly fine fish. Thus a Mullet of six pounds is said to have produced a sum equal to £48 sterling, and a larger one as much as £64; whilst no less than £240 were given for three large Mullets, which were procured on the same occasion, for a repast of more than usual magnificence—(Yarrell). The Romans also kept Mullets in glass vases; but thesc appear to have been specimens of the smaller species, the Mudlus barbatus (Fig. 14), which is of a still more beautiful colour than the common Mullet of our shops. Both species are abundant in the Mediterranean, and occur also in the British seas, although here the Wf. barbatus is far from being common. The third of these groups, which were referred by Miiller and Cuvier to the Perches, is the family of Sphyrenide, of which a few species are found in the Mediterranean, although the greater number live in the seas of tropical climates. The fishes of this family are of an elongated form, somewhat resembling the Pikes (Esocide), with which Linneus placed those species with which he was acquainted; in the form of the head and jaws, and the formidable nature of the teeth, they also somewhat remind one of those soft-finued fishes. They are, however, furnished with two dorsal fins, separated by a considerable interval, of which the anterior is strongly spinous; and the air-bladder is completely closed. They differ from the Percide in having the ventral fins placed on the belly, at a considerable distance behind the pectorals, the margins of the opercula and preopercula perfectly smooth, and the scales, which cover not only the body but also the sides of the head, of the description called cycloid. The Sphyrzenide are all exceedingly predaccous fishes, and some of them attain a considerable size. The best known species, the Sphyrena vulgaris, which appears to be tolerably common in the Mediterranean, often measures as much as three feet in length, and is a handsome, silvery fish, with a bronzed or bluish back. It is said that the fluid 316 THE MAIGRES. called “essence d’orient,” used in the manufacture of artificial pearls, is prepared from the scales of this fish, together with the minute silvery particles of its air-bladder. A species inhabiting the seas of tropical America, the S. Barracuda, grows to a much larger size, and is almost as much dreaded as the shark by the inhabitants of those countries. Its flesh is said to.be exceedingly good, and not unlike that of the pike; it is eaten both salted andfresh, At certain times, however, it is found to be unwhole- some ; and this quality is said to be derived from its feeding at those periods upon the fruit of the manchineel-tree, although this appears to be exceedingly improbable. The symptoms produced by eating it when thus out of condition are sickness, nausea, and violent pains in the joints; the latter are said to have lasted for five-and-twenty years, accompanied by a loss of hair and of the nails. It is asserted that the poisonous individuals may be recognised by the bitterness of the liver, and by the flowing of a white fluid from them when cut; when salted, they are said to lose their injurious properties. i _ The Scienide are also nearly allied to the Perches, with which they agree in the arrangement of their fins, and in having the opercula and preopercula dentated; but the vomer and palatine bones, which in the Percide are always armed with teeth, are toothless in these fishes. Some of the bones of the head are inflated and cavernous, giving a more or less convex appearance to the forehead; the mouth is large, and the jaws are usually armed with powerful fangs, interspersed amongst the smaller teeth. The body is always covered with ctenoid scales, which, as in the Sphyrenide, fre- quently extend over the head. The air-bladder is of very singular construction ; it is completely closed, and furnished with numerous cecal appendages, which are often branched, and sometimes surround it in such a manner as to give it the appearance of a fringed bag. This peculiar form of the air-bladder is very striking in the Maigre (Sciena aguila), as figured by Cuvier and Valenciennes, and by Mr. Yarrell, The Scizendice are large and powerful rapacious fishes. The species just referred to is common in the Mediterranean, and occurs occasionally on our own coasts, where specimens upwards of five feet in length have been taken. In the Mediterranean, it often grows to six feet. Its flesh is considered pretty good, and was in great repute with the Roman epicures. The Maigres swim in small shoals, uttering a peculiar grunting noise, which is said to be audible even when the fishes are at a considerable depth. When taken, their strength often renders their struggles very inconvenient in the boats, as they are said to be capable of knocking over their captors. To avoid such a disagreeable interruption to their labours, the fishermen usually knock them on the head as ‘soon as they are got into the boat. The bones of the ear in the Scianide are usually larger than in most other fishes, and, in former days, extraordinary pro- perties were attributed to them; they were said to prevent and ‘cure the colic, and for this reason were often honoured with a gold setting, and suspended from the neck. It was necessary, however, that the colic-stone, as it was called, should have been presented to the wearer, otherwise it was of no efficacy. Numerous species of this family inhabit the seas of the warmer regions, and many of them furnish excellent food. The Sparide, in their general form, and in their toothless palates, present a great similarity to the fishes of the preceding family ; but the bones of their opercula are not toothed or spinous, and the forehead does not exhibit the inflated appearance charao- teristic of the Seienide. The ctenoid structure of the scales is very indistinct in this THE SPARIDZ. 317 family ; the scales, as in the preceding family, cover the sides of the head, but never extend over any portion of the fins. The body is usually broad and much compressed, with a single long dorsal fin, of which the anterior portion is supported upon strong spinous rays; the ventral fins are placed on the breast under the pectorals. The teeth are sometimes in the form of acute fangs, of which some are often of considerable size, whilst in other species they are broad and rounded, constituting a powerful grinding apparatus, with which the fishes thus provided crush the hard shells of the Mollusca, on which they principally feed. The Sparide are all inhabitants of the sea, and most of them are found in warm climates, although the Mediterranean possesses several species; and a few are not unknown on our own coasts. They are divisible into two groups, which, in fact, were regarded as distinct families by Cuvier. In one of these groups (the Ienides), the mouth is protrusible, the pedicles of the intermaxillary bones being very long, so as to give the upper jaw a considerable power of motion. Some species are very abundant in the Mediterranean; but their flesh is very little esteemed. A West Indian species (Gerres rhombeus) is said occasionally to find its way to the coast of Cornwall, accom- panying pieces of wood covered with barnacles, which are conveyed across the ocean by the currents. In the other group (the true Sparides), the upper jaw is firmly attached to the head, and not protrusible; of these, several species are occasionally taken off the British coasts. .Some of them attain a length of upwards of two feet ; and several are highly prized as food in the countries bordering the Mediterranean, where they occur in great abun- dance. They appear to be voracious fishes, feed- ing on Mollusca, Crus- tacea, and small fishes; but some of them vary this diet by devouring sca-weeds, which they tear from the rocks. The great family of the Chetodontide is distinguished from the preceding groups by the exceedingly compressed form of the body, and by the singular manner in which the soft parts of the perpendicular fins are clothed with scales, often to such an extent that the boundary between the body and fin is quite undiscoverable (Fig. 31). The fishes of this family are generally of a discoid form, like many of the common flat fishes, but the eyes are placed on each side of the head, both sides of the body are similarly coloured, and the fishes swim upright in the water. The mouth is usually small, and furnished with bristle-like teeth ; in a few species it is larger, and armed with cutting teeth, or fangs. The whole body, including the sides of the head, and the base of the median fins, are covered with ctenoid scales; the dorsal fin is single, with a few, usually short, spinous rays at its anterior part; the first soft rays of the dorsal and anal fins are sometimes produced into long filaments, or the fins themselves are very long, and pointed anteriorly, gradually decreasing in depth towards the hinder part of Fig. 30.—Pagrus vulgaris. 318 THE CHTODONS. the body, so that the whole fish assumes the form of a‘crescent, with the tail projecting from the centre of the concavity. The ventral fins are placed under the pectorals. The Cheetodontide are generally of small or moderate size, and most of them are inhabitants of the tropical seas. They are remarkable for the exceeding magnificent ‘colours with which they are generally adorned, and which are ren- dered still more pleasing to the ‘eye by the broad black bands which, in most cases, traverse the body from the dorsal to the ventral margin. One of these bands pénerally passes down the region of the eye. The flesh of these ‘fishes is said to be exceedingly delicate and well flavoured. Only a single species (the Brama Raii) inhabits'the British seas, where it is by no means common, although in the Mediterranean it occurs in great abundance. It's said occasionally to mea- -sure two feet six inchesin length ; but the largest specimen seen by Mr. Yarrell did not exceed sixteen inches. Its flesh is highly esteemed. A singular species, the Chelmon rostratus, Fig. 31.—Heniochus monocerus. inhabiting the Chinese seas, has the jaws very much prolonged, forming a sort of beak, but so inclosed in ‘the skin that only a small opening is left at its extremity for the mouth. This fish is said to exhibit a very curious instinct ; it ‘projects a drop of water from its mouth at any insect that it perceives within reach of such a missile, ‘so’as to bring it down into the water, where, of course, it falls an éasy ‘prey to its dexterous assailant. The Chinese keep these ‘fishes in basins, and amuse'themselves by watching their efforts to bring down a -fly suspended over them by a ‘thread. A Javanese species, the Toxotes jaculutor, which has @ wide motith, with the lower jaw considerably pro- longed, exhibits the same singular instinct; it is said to ‘throw the water to a height of three or four fect,.and rarely to miss its aim. The family Teuthide, includes a small nuntber of ‘fishes, which are all inhabitants of the seas of ‘hot climates, and which are remarkable for having the sides of ‘the tail armed either with several ‘sharp prickles, or with a large curved spine (Fig. 32). They are of'a broad compressed ‘form, with -a single dorsal fin, in front of which there is often a free spine. The body is covered Wwith ctenoid scales, which, ‘however, do not extend over any part of the‘fins; and'the jaws are‘furnished with a single series of cutting teeth. THE SURGEON-FISH—THE MACKERELS. 319 The Teuthids are herbivorous fishes, feeding upon sea-weeds. The species with spinous tails, if incautiously handled, inflict severe wounds upon their captors ; and the common .West Indian , speciés (Acanthurus chi- vurgus) has received the name of the surgeon from this circumstance. The next four fami- lies were included | by Cuvier in a'single group. They are all composed of active fishes, with power- ful fins and smooth bodies, usually covered with small scalés, which are often concealed in the skin; the opercula are unarmed. The pyloric cceca are numerous. 4 In the great family of the Séomberide, or Mackerels, many of which are of such great importance as food, the skin is sometimes quite naked, sometimes more or less clothed with cycloid scales, and the tail, which is slender and furnished with a powerful, usually forked fin, is almost always marked with scaly ridges. The fishes of this family have sometimes one, sometimés two dorsal fins; in some cases the spinous rays of the first dorsal are very short and destitute of membranie;* in others the fin is ‘well- developed, and the rays are furnished with long filamentous appendages (Fig. 33). The second dorsal and the anal also exhibit a ‘considérable diversity of structure; the i zs spinous portion of the anal fin Sp is frequently separated from the soft part; and the latter, both in the anal and second dorsal, may either form an en- tire fin, or give rise to a series of small fins, running along the upper and lower surfaces of the tail, a structure whichis readily seen in the common Mackerel. The tecth are generally con- fined to the jaws; they are almost always acute, and often of large size. The fishes of this family are all marine, and usually predaceous in their habits. In the form of their bodies they i present two distinct types which might perhaps be regarded as sufficient for their division into two families. In one, the Zenides, the body is short, bro#d and compressed, presenting a ‘good deal of resemblance in form to the Cheetddontidee, with which thése fishes ‘also agree in the considerably development ef the ‘pérpendicular fins, which are often furnished with Fig. 32.—A canthurus phlebotomus. = = ‘Fig. 38.—Blepharis, 320 THE DOREE. filamentous processes (Fig. 33). The mouth is usually protrusible, and the teeth small and weak. Of this group the commonest species is the Doree, or John Dory (Zeus Faber, Fig, 34), which is taken abundantly on our southern coasts, and which was regarded by the epicure Quin as such a delicacy, that it was worth the trouble of a journey from Bath to Plymouth, and back again, in order to eat Doree boiled in sea-water. The origin of the English name of this fish has frequently exercised the ingenuity of zoological ety- mologists ; but the most rational derivation appears to be from the French dorée, or jaune dorée, which refers to the golden yellow colour of the fish when fresh. Roman Catholic legends point to it as the fish from which St. Peter took the tribute-money; the black marks on its sides being ascribed to the pressure of the Apostle’s fingers. Hence it is known in several countries of Europe as St. Peter's Fish, although the Haddock, which also exhibits a blackish mark on each side of the body, is considered by many to dispute its title to this honour. The Doree sometimes attains a weight of ten or twelve pounds; but the ordinary weight of those brought to the London market is between four and six. Two other species of this section of the family are occasionally taken in the British seas, although they are apparently rare. ,One of these, the Opah, or King-fish (Lampris guttatus), appears to be distributed over nearly the whole globe, as, according to Mr. Yarrell, it has not only been taken in the European seas, but is also said to occur on the west coast of Africa, and appears to be well known both in China and Japan. In the latter empire the Opah is sacred to the Japanese Neptune. It is a magnificent fish; the back and sides are of a fine green, with purple and gold reflec- tions, fading into yellowish green on the belly, and covered with numerous round whitish spots; the fins are of a fine vermilion colour. Mr. Yarrell tells that a person, looking at a specimen of this fish, observed “that it looked like one of Neptune’s lords dressed for a court day.” The second division of the family, the Scomberides, includes a great number of exceedingly valuable fishes, which present more or less resemblance to the common Mackerel. The body, instead of being compressed, is elongated and spindle-shaped, or occasionally almost cylindrical; the mouth is large, not protrusible, and fre- quently armed with large teeth. The type of this section is the common Mackerel (Scomber Scomber), a fish which is too well known to need any description. The Mackerels usually spawn during the months of May and June; andit is when approaching the shores in vast shoals for this purpose that they are principally taken. The most common mode in which the fishing is carried on is by means of long nets, called drifé nets, which often extend for nearly a mile in length, descending into the water to a depth of about twenty feet. These nets are let down into the water at nightfall, and Fig. 84.—The Doree (Zeus Faber). THE MACKEREL AND TUNNY. 321 left in position all night, suspended to a stout rope, which is supported at one extremity by a large buoy, and at the other attached to the fishing-boat. The meshes of the net are just large enough to allow the fish to pass through as far as the pectoral fins; so that when they have advanced thus far they are held suspended in the net, without the power of escaping, either by retracing their course or pressing the thick part of their bodies through the obstacle. In the morning the nets are hauled in, and the fish detached from them, and in this manner vast quantities of Mackerel are taken. The Mackerel is also captured by surrounding the shoals with a large deep net, called a seine, which is afterwards closed at the bottom, or hauled to the shore; and a considerable number are taken with hook and line. It is a voracious fish, feeding principally upon small fishes and the fry of larger species. The ordinary size of those brought to market is from fourteen to sixteen inches, with a weight of from one-and-a-half to two pounds ; but they are said oczasionally to attain a length of twenty inches. The Tunny (Zhynnus vulgaris), a fish belonging to this family, which is very abundant in the Mediterranean, grows nearly to twenty feet in length, and weighs sometimes as much as ten hundredweights. Like the Mackerel, this large fish approaches the shores in large shoals for the purpose of spawning, when it is captured by means of a large net, called a mandrague. This is composed of nets arranged in a funnel-like form, so that the fish, entering the wide mouth, are gradually led up to a narrow prison, when they are destroyed by spears and harpoons. Professor Vogt, who has given a most animated description of the Tunny fishery, states that these nets extend a quarter of a mile, and cost as much as thirty thousand francs. The flesh of the Tunny is highly prized by the inhabitants of the coun- tries bordering the Mediterranean, where its cap- ture has been an important object since the most remote antiquity. Several allied species are also ‘Fig. 85.—Tunny (Thynnus vulgaris). found in that sea, amongst which the most celebrated is the Bonito (Thynnus pelamys), which rivals the Dorado in its perpetual chase of the Flying-fish. One of the most remarkable fishes of this family is the Pilot-fish (Nazcrates ductor), which receives its name from its habit of accompanying ships for weeks together; the ancients even asserted that it pointed out the proper course to the mariner when he was at a loss how to proceed, leaving him when he had arrived in sight of the desired haven. It appears probable, however, that the Pilot-fish only attends the voyager for the sake of the nu- merous pieces of food which are constantly being thrown overboard ; and a community of feeling in this respect may, perhaps, account for the frequent association of the Pilot-fish and the Shark. It is, however, a general opinion amongst navigators that the Pilot-fish really attends upon the Shark as a guide; and an instance has been related in which two of them led a Shark toa baited hook that had been thrown out for him. Another observer, however, quoted by Dr. Hamiiton Smith, in “Griffith’s Animal Kingdom,” states that he repeatedly saw a Shark, which was inclined to swallow a bait put out for him, pre- Fig. 36.—Pilot Fish (Naucrates ductor). ax 322 THE PILOT-FISH, SWORD-FISH, AND DORADO. vented from doing so by one or other of four Pilot-fishes which accompanied him; and that when at length the Shark had swallowed the tempting morsel and was being hauled out of the water, one of his diminutive friends clung to his side for some little time. Colonel Hamilton Smith also states that he had witnessed u similar circum- stance. The Pilot-fish attains a length of about a foot. It is somewhat of the form of the Mackerel, of a silvery gray colour, bluish on the back, and adorned with five dark blue bands, which go round the whole body. Its flesh is said to be very good. Nearly allied to'the Mackerels are the Sword-fishes, Xiphiide, which are rendered remarkable by the prolongation of the upper jaw into a long, spear-like weapon. They are also characterized by the structure of the branchie, the lamine of each branchial arch being united so as to form a band-like organ, in which the separation of the laminz is only indicated by superficial marks. This structure occurs in no other bony fishes. In the form of the body they resemble the Mackerels; the spinous dorsal fin commences close to the neck, where it is high and sickle-shaped, and runs thence nearly to the tail, where it is followed by a small soft fin; the anal fin exhibits a very similar construction, although it is much shorter. The ventral fins are wanting, or _ represented only by 4 pair of spinous rays, situated on the throat; the caudal is deeply forked, and the sides of the tail have large ridges. The common Sword-fish (Xiphias gladius) is found not uncommonly in the Medi- terranean, and occurs sometimes in our own seas. It is a large fish, attaining a length of fifteen, or even twenty feet, and is most predaceous in its habits, employing its long bony spear for the destruction of the larger fishes. Its activity and strength are very great; and it has been known to strike at ships passing through the water, and to bury its weapon in their timbers. Cuvier states that a parasitic crustacean buries itself in the flesh of the Sword-fish, and torments it to such an extent that it will sometimes rush upon the shore; the same cause of irritation may, perhaps, have something to do with its suicidal attacks upon such a very unequal antagonist as a ship, The common Sword-fish is the only European species of this family ; but the seas of tropical climates contain several others. Their flesh is said to be exceedingly good, especially when young. In the Coryphenide the body is much compressed, with a broad dorsal fin running along the whole of the back ; all the rays of this fin are almost equally flexible, although those of the anterior portion are not articulated. The ventral fins are frequently wanting ; when present they are usually very small and placed under the pectorals, although sometimes situated on the throat. The abdominal cavity is small, so that the anal opening is placed far forwards, and theanal fin usnally occupies a considerable portion of the ventral surface, sometimes extending forwards to the level of the pectorals. The dorsal and anal fins are generally very high; and in one genus (Pteraclis) they attain such a development as to make the lateral surface of the whole fish at least three times as great as that of the body. The tail fin also is very large, and usually deeply forked. The mouth is of moderate size, and armed with acute teeth. The Coryphenide are all inhabitants of the salt water, and generally occur only in the seas of warm climates. The only European sea in which they are found is the Medi- terranean, which possesses several species. Amongst these the best known is the Dorado (Corypehna hippurus), sometimes called the Dolphin, a fish adorned with the most beautiful metallic tints, and which is alsoremarkable for the swiftness of its course, and for the continual war of destruction which it wages with the Flying-fish, . THE RIBBON-FISHES. 323 It attains a length of about five feet; the head is large, and the body tapers gradually ; from this to the tail, The back is bluish, the belly yellow, and the whole surface spotted with a-darker blue. When in the water it presents a splendid golden lustre which, however, rapidly vanishes when it is taken out of its native element. The fourth and last of the families, formed by modern authors at the expense of the Guvierian Scomberoides, is that of the Notacanthide, in which the body is much elongated, and more or less Kel-like in its form, and has its hinder extremity usually | surrounded by the same continuous fin that is. characteristic of the Eels. The spinous portion of the dorsal fin is.destitute of membrane, so that the rays form a.series of spines running along the back; the second or soft dorsal is frequently wanting altogether. A further point of resemblance to the Eels is presented by the pectoral fins, which are attached to the spinal column at some distance behind the head; the ventral fins are sometimes wanting, and when present are situated on the abdomen. The whole sur- face is covered with small cycloid scales, and the front of the upper jaw is usually pro- duced into a sort of beak. Most of the species of this family occur in the tropical regions; but one, the Notacanthus nasus, is found in the Arctic Ocean. Some of them live in fresh water. 7 In the exceedingly elongated form of their bodies, the fishes of the next family, the Cepolide, or Ribbon-fishes, present a considerable resemblance to the Notacanthide, . but their bodies are much compressed, so as to acquire a ribbon-like form. The dorsal | fin, which always commences close to or upon the head, is completely furnished with membrane ; and the caudal, when present, is usually quite distinct from the other per- pendicular fins. ‘The position of the caudal fin in some of these fishes is very peculiar ; instead of being placed at the extremity of the body as in most fishes, it is set on at aright angle, forming a fan-like organ extending upwards from the extremity of the tail. The ventral fins are sometimes altogether deficient ; when present they are placed under the pectorals, and are sometimes of small, sometimes of large size, and occasionally | represented by one or more long spines. The body is covered with very small scales. These singular fishes are all inhabitants of the sea; several species have been taken on our own coasts, al- though they are of rare occurrence. Several of them attain a considerable length; the one here figured, Gymnetrus Bank- sit (Fig. 37), having been found as much as twelve feet long. With this extraordinary length its greatest thickness was two inches and three quarters. It is of a beau- Fig. 87.—Gymnetrus Banksii. tiful silvery colour, with a few blackish streaks and spots. Some of the species, although rarely met with, appear to have a very wide geographical distribution ;- the Lepidopus argyreus, or Scabbard- fish, is found on the English coasts and at the Cape of Good Hope; and the Trichivrus lepturus inhabits the seas of both America and the Old World. _Scarcely anything is known of the habits of the fishes of this family. 324 MULLETS. The family Mugitide, of which the Grey Mullet is a typical example, includes only a few fishes, with a more or less cylindrical or spindle-shaped body, covered with large scales, which, although in reality ctenoid in their structure, lose their den- ticulations so easily that they often appear to be cycloid. The head, which is some- what flattened above, is covered with similar scales, or with polygonal plates; the mouth is rather small, and furnished with excessively fine teeth, which are sometimes almost imperceptible. In their appearance, these fishes present a good deal of resem- blance to some of the more elongated Cyprinide, but are easily distinguishable from these by the distinct, spinous, first dorsal fin, which is rarely supported upon more than four rays, and is separated from the second dorsal by a considerable interval. The ventral fins are placed on the abdomen, a little behind the pectorals. The pharyngeal bones are very large; the stomach is furnished with a sort of fleshy gizzard, and the intestine with a few pyloric coca. The Mugilide generally inhabit salt water, keeping by preference about the mouths of rivers, which they usually ascend and descend with the ebb and flow of the tide, Our common Grey Mullet (Mugil capito) is regarded as a very delicate fish, and the county of Sussex is especially celebrated for it. It is exceedingly active in the water, and often escapes the fishermen by leaping over the headrope of the net; when one of the prisoners has taken this course, the others are sure to follow, unless the net be raised sufficiently to prevent them. Two other species of Mugil are found upon the British coasts, but they appear to be rare ; the Mediterranean possesses five species. The Sand-smelt (Atherina presbyter) a small fish which is tolerably abundant along the south coast of our island, also belongs to this family. It resembles the Grey Mullet in the habit of ascending the mouths of rivers with the tide. The Sand-smelt is about five or six inches in length, and is considered to have some resemblance to the Smelt in its flavour. It is a favourite fish with visitors to the southern watcring places, but seldom reaches the London market. Nearly allied to the Mugilide is the singular family of the Anabatida, the remark- able habits attributed to one member of which has obtained for it the name of the Climbing Perch. The fishes of this family are very variable in form—sometimes broad and flat, sometimes elongated and cylindrical; they have a single dorsal fin, of which the anterior portion is usually strongly spinous, but in some species the rays of this part of the fin, although undivided, are very flexible. The anal fin is also single, with a spinous anterior portion. The whole surface is covered with scales, which in the soft-finned species are truly cycloid, whilst those of the spiny forms are ctenoid. The ventral fins are placed under the pec- torals ; one of the rays is frequently much elongated, and in some species the ventral fin is represented by a single long fila- Y ment. esa == The most remarkable character pre- Tig. 38.—Head of Anabas scandens, with the sented by these fishes, however, consists operenlum: removed: in the structure of the superior pharyngeal bones (Fig. 38), which are dilated into voluminous folded laminz, inclosed in a large cavity of the base of the skull, and forming numerous cells, in which a supply of water THE CLIMBING PERCH—THE GOBIES. 325 may be carried, for the purpose of moistening the gills, when the creature, as its habit is, quits the water for a time. This peculiar structure attains its greatest development in the Anabas scandens, or Climbing Perch of India (Fig. 39), which is by this means enabled to live out of the water for as long a period as six days. They frequently quit the ponds or streams which they inhabit, and wander for a considerable distance over the land—a circumstance which has led the inhabitants of the countries frequented by them to suppose that these fishes , fell from the skies. They are ¢ even said to climb trees; and © Daldorff states that he once took a specimen, at a height of five feet from the ground, on the stem of a palm-tree,—but Fig. 39.—Climbing Perch (Anabas Scandens). this habit has been denied by some other naturalists. Daldorff’s statement, however, receives some support from the Tamul name of the fish—Paneiri, or the Climber of Trees. This and some other species of the family are commonly exhibited by the jugglers of India and China, to which countries the fishes of this family are almost entirely confined; their flesh is exceedingly good, and one species, the Gourami (Osphromenus olfax), which grows to the size of the Turbot, is considered even to excel that highly-prized European fish. The Gourami is a native of China; but has been naturalized in the Mauritius, and even in Cayenne. The great tenacity of life possessed by these fishes enables the fishermen to bring them to market alive ; and the larger species are often cut up alive to suit the convenience of the smaller consumers. The Godiide are usually distinguishable at the first glance by having the ventral fins, which are situated on the breast, united into «4 funnel-shaped disc. These fins are sometimes distinctly separated, or united only at their bases; but even in these cases they are usually capable of being formed into a funnel at the pleasure of the animal. The pectoral fins are large, and the entire rays of the dorsal and anal fins soft and flexible. The skin is sometimes naked, sometimes clothed with large, finely ctenoid scales; the edges of the opercula are unarmed, and the opercular aperture small, so that these fishes are enabled to live for some time out of the water. The stomach and intestines are both destitute of coeca. Some of the fishes of this family produce living young, but the majority appear to be oviparous. The male of a species of Godius, inhabiting the Mediterranean, has been observed to make a nest amongst the seaweeds, with the roots of the Zostera, or Grass- wrack; in this he awaits the females, which soon come to deposit their spawn: this is fecundated by the male, and he then remains as a guard over the precious deposit, which he defends with the greatest courage. This habit of the Godiws was probably known to the ancients, as Aristotle mentions a fish, called phycis, which he says is the only fish that constructs a nest: we have already seen, however, that it is certainly equalled in this respect by our common Sticklebacks (page 41). The Gobiidz are, for the most part, small fishes, which keep close to the shore, usually amongst rocks; they often attach themselves by means of their disc-like ventral fins to the lower surface of stunes and other objects. Some species are also abundant in tidal rivers. 326 THE LUMP-FISH AND SUCKING-FISH, One of the largest and most singular species is the Lump-fish (Cyclopterus lumpus), which inhabits the northern European seas, and may often be seen hanging up in the shops of the London fishmongers. It is also called the Lump-sucker, and is the Cock- paddle of the Scotch. The Lump-fisk sometimes weighs as much as seven pounds, and is of a thick massive form; but its flesh is very soft and insipid. It is of a purplish black colour, variegated with red and brown, and the belly is crimson. The back and sides have rows of tubercles, and the appearance of the fish is extremely grotesque. The sucker, formed of the ventfal fins, is of a somewhat oval form, and of great size and powef. §o firmly does it adhere by means of this organ that, according to Pennant, on putting a freshly-caught specimen into a pail containing several gallons of water, it fixed itself so firmly to the bottom that the whole pail, with its contents, could be lifted by taking hold of the tail of the fish. It is said to feed upon Medusz and other gelatinous marine animals, and in its turn affords a favourite repast for the Seals, which, however, reject the skin. A still more remarkable and celebrated fish belonging to this family is the Remora, or Sucking-fish (Zcheneis, Fig. 40), of which « few species are found in the seas of various patts of the world. In this genus the ventral fins are only united at the base, and do not appear to be applicable to the attachment of the animal to submarine bodies; but to compensate for this, the upper surface of the head is furnished with a singular disc, formed of transverse, cartilaginous, denticulated plates, by means of which the Remora attaches itself to rocks, ships, and even to the bodies of large fishes. : The habit which this fish has of fixing itself to the bottoms of ships, gave rise, in ancient times, to the opinion that it could thus instantaneously arrest the course of a ship in full sail; and the names still applied to it in several countries refer to this fable, which is related in the most circumstantial manner, and with the utmost good faith, by several ancient authors. Thus, amongst other marvellous tales, we are told that at the battle of Actium, Antony’s ship was held motionless by a Remora, notwithstanding the exertions of several hundred sailors; and on another oecasion we are informed that Caligula, when on a voyage, was arrested by one of these fishes, which attached itself to. the rudder, and manifested such an invincible determination that the emperor should not proceed on his voyage, that the efforts of four hundred able seamen were of no avail, until one of them, more knowing than his. fellows, ascertained the cause of this disagreeable occurrence, and, by detaching the obstinate Remora, set the ship free to pursue her course. The common Remora is about a foot long, and somewhat of the form of the Herring. It occurs commonly in the Mediterranean, and is also found in the ocean, and occasionally on the British coasts. Some of the other species are larger and more elongated. The Dragonets (Callionymus), of which two species are found on our coasts, are arranged amongst the Gobiide, although they appear to possess characters which might entitle them to form the types of a distinct family. Their branchial apertures are very small, and placed at the upper part of the opercula, close to the back; and their ventral fins are very large and distant. The eyes are placed on the top of the | head, looking upwards; the skin is smooth and scaleless, and the first dorsal fin has bristle-like rays, of which the first is sometimes exceedingly elongated. They are Fig. 40.—Sucking Fish (Zcheneis remora.) THE BLENNIES—THE SEA-WOLF. 327 handsome fishes, of moderate size, often adorned with brilliant colours, and their flesh is said to be very good. Nearly allied to the preceding are the Blenniide, which were, in fact, placed in the same family with the Gobies by Cuvier. They are distinguished, however, by the structure of the ventral fins, which are placed on the fore part of the breast, or on the throat, and consist only of a few, usually two, rays. In the Sca-wolf (Anarrhicas lupus Fig. 41), the ventral fins are entirely wanting. They agree with the Gobiide in the structure of the intestinal canal, and in the absence of the air-bladder ; the skin is either naked or furnished with very small concealed scales, and is covered with a great quantity of mucous matter; from the latter cir- cumstance the name of the typical genus Blennius (Gr. dlennos, mucus) is derived. The dorsal fin is very long, usually extending throughout the whole length of the back; the entire ray& of this and of all the other fins are flexible, as in the preceding family. The pectoral fins also are very large. The mouth is usually armed with acute fangs, which, in the Sea-wolf, acquire most formidable dimensions, and are accompanied by an inner series of blunt molars, which serve to crush the shells of the molluscous animals upon which this creature usually feeds. The abdominal cavity is short, and the anal fin consequently of considerable length. The head is frequently furnished with tentacular filaments, which are some- times singularly branched (Fig. 42). Of the British species, the Shanny (Blennius pholis) is remarkable for the habit exhibited by the larger specimens, of creeping out of the water, with the aid of their pectoral fins, as the tide recedes, and hiding themselves in holes amongst the rocks, where they remain until, on the return of the tide, the water again covers them and sets them at liberty. They place themselves singly in these caves, with their heads outwards; and if any danger shows itself at the mouth of their retreat, they immedi- ately retire backwards to its more sheltered recesses. This fish has even been known to survive a confinement of thirty hours in a dry box; but it is soon killed by being put into fresh water. : Many of these fishes produce living young; and, in general, the outlet of the male generative organs is situated in a small prominence near\the anal opening, which gives considerable support to the opinion that a genuine copulation must take place between these fishes. Of the British Blennies, one species, the Zoareus viviparus, exhibits this peculiarity of bringing forth its young alive; and they are said to be perfectly able to take care of themselves from the moment of their exclusion. The young appear to be of different sizes, in proportion to the sizeof the females producing them. Thus, Mr. Yarrell mentions that a specimen of fifteen inches long, which was brought to the Edinburgh fish-market, contained several dozens of young, which were still alive, and measured from four to five inches long; whilst the young of another female, seven inches in length, were only about an inch and a-half long. The Blennies are generally of small size, and of little or no value. They swim together im small shoals amongst the rocks of the sea shore, and are constantly to be found in the small rock pools left by the retiring tide. They are exceedingly active, NN Fig. 41.—Sea-wolf (Anarrhicas lupus). 328 THE SEA-WOLF. and difficult. to catch, even when confined within a small space, dashing and leaping about with the greatest rapidity, and concealing themselves under the sea- weeds which fringe their pool. Like the Gobiide, they are able to live for a considerable time out of the water; andone species, the Salarias scandens of Ehrenberg, which inha- bits the Indian Ocean and the Red Sea, is able to ‘Fig. 42,—Ocellated Blenny (Blennius occllaris). climb and leap about the : rocks of the shore. It is so excecdingly active in this somewhat anomalous position that it has been taken by some observers for a small Lizard; and as it can take leaps of four or five feet, it is by no means easy to catch. , One of the largest and most formidable fishes of our seas is the Sea-wolf (Anarrhi- cas lupus, Fig. 41), which belongs to this family, and the dentition of which has already been referred to. In the British seas, this fish attains a length of six or seven feet, and in more northern and colder latitudes it is said to grow still larger. The back of this formidable fish is of a brownish-gray or olive-brown colour, with trans- verse black or brown stripes, which extend more or less over the whitish belly. Its common food consists of crustaceous and molluscous animals, for crushing which its powerful apparatus of teeth is especially adapted, and the strength of its jaws is exceedingly great. When captured, it defends itself vigorously, attacking the fisher- -men with the greatest ferocity, and often inflicting severe wounds upon those who are ‘not very careful in their approaches ; this ferocity, however, is the means of shortening the captive’s life, for the fishermen, knowing its habits, generally contrive to knock it on the head before it has an opportunity of doing any mischief. Its appearance is completely in accordance with its nature; for few fishes look more savage than the “Sea-wolf. Its flesh, however, is said to be exceedingly good; and as it bears salting well, it is of no small importance to the inhabitants of Iceland, where it is found in great abundance. The skin is converted into a sort of shagreen, which is much used for making bags and pouches; and Cuvier states, that the Icelanders employ its liver in place of soap. The Lophiide, forming the last family of the spiny-finned fishes, present u good deal of resemblance to the Gobiide, and especially to the Calionymi and their allies ; they are particularly distinguished by having the carpal bones very long, forming a sort of arm, at the extremity of which the pectoral fins are supported. The ventral fins are placed in front of these, on the flattened lower surface of the body; and the pectoral fins thus form, as it were, a pair of hinder legs, upon which many of the creatures are able to hop about upon the sea-beach in a very curious manner. Most of these fishes have a large head, and a short, stout body, terminated by a slender tail. They are covered with a naked skin, which is usually roughened with warts and tubercles of different kinds. The branchial aperture, which is placed behind the pec- toral fins, is very small, whilst the branchial cavity itself is of large size; and, as is THE FISHING-FROG. 329 usual in fishes which exhibit this conformation, the Lophiide are able to endure u tolerably prolonged absence from the water. The best known of these fshes is the Lophius piscatorius (Fig. 43), commonly known underthenames of Angler, Fishing Frog, and Sea Devil. It is perhaps one of the ugliest of all fishes ; its head is of enormous size, forming nearly half the entire body, and is cleft in front by a most formidable —_ transverse mouth, armed with numerous pointed teeth. , The head is much de- WY pressed, and the eyes are placed upon the top of it, eee Sica rather close together. ‘The body is’very short, and terminated posteriorly by the pec- toral fins, behind which it runs off into a gradually tapering tail, bearing two dorsal fins, and the caudal and anal fins. . The Fishing Frog is a sluggish fish, and as its voracious appearance by no means belies its character, it might be supposed that it would have some difficulty in gratify- ing the enormous appetite which must apparently be associated with such a tremendous mouth. It is said, however, that the fish possesses a stratagem by which to satisfy the cravings of its maw, without the necessity of subjecting its unwieldy person to any very violent exertion. On the upper surface of the front of the head are two long moveable bony filaments, the foremost of whichis dilated at its tip, which has a silvery lustre. Lying close to the ground, the fish disturbs the sand or mud, so as to obscure the water around it, justly thinking, no doubt, that its appearance is not sufficiently amiable to inspire much confidence in the weaker inhabitants of the deep; it then elevates the filamentous appendages just described, and waves them to and fro in the water, when the small fishes, which are soon attracted by the hope that this silvery object is something to eat, become instead the prey of their artful foc. This is said to be the ordinary mode of procuring its food followed by this fish, but it certainly at times seeks its prey by other methods. Thus Mr. Yarrell quotes a case in which one of these fishes seized a Cod which had just been hooked by a fisherman, and allowed himself to be drawn up to the surface, where he was only compelled to quit his hold by a severe blow on the head; and on another occasion a Fishing Frog seized a Conger Eel that had just been hooked, when the latter wriggled himself through the narrow bran- chial aperture of hissecond captor, and in this manner both fishes were drawn up together. The Lophius piscatorius is a large fish, sometimes attaining a length of no less than five feet. The most common size, however, is about three feet, and specimens of this size are not unfrequently taken at various parts of the coast. In itself, the fish is of no value, but many of the fish found in its capacious stomach are generally quite uninjured, sometimes even alive; and the fishermen frequently make a little money by exhibiting the fish itself to sea-side visitors, generally accompanying their exhibition with a most doleful lamentation upon the ravages committed by their not very pre- possessing captive. Fig, 43.—Fishing Frog (Lophius piscatorius). 330 THE LOPHOBRANCHIA, Sus-orDER V.—LoPHOBRANCHL.. General Characters,—In all the groups of bony fishes which we have hitherto had under consideration, the gills are formed of comb-like series of laming ; but in the Lophobranchia, these organs are arranged in little tufts, disposed in pairs along the branchial arches, a conformation which is not exhibited by any other bony fishes. The opercula, are very large, but are confined throughout by a membrane which only leaves a very small aperture for the exit of water, and the branchiostegous rays are entirely wanting. The body is very elongated in its form, and covered with bony plates, which are usually of considerable comparative size, so that the body becomes more or less angular. The fins are usually very imperfectly developed; the pectorals are small, the ventrals usually altogether absent, and the caudal and anal fins are also often wanting. The bones of the face are much prolonged, forming a sort of snout or proboscis, at the extremity of which the oral aperture is situated, a structure very similar to that which we have seen in the family Fistularide (page 39), in the preceding sub-order.. This sub-order includes only a single family, the Syngnathide, composed of small fishes of very singular appearance. The best known form is the Hippocampus or Sea- horse (Fig. 44), so called from the remarkable resemblance which they present to that mammal when the elongated head is bent at about a right angle to the axis of the body. One species is found in the British seas; but specimens of tropical species are often brought home by sailors, and may commonly be seen in the shops of dealers in curio- sities. They possess no caudal fin, and make use of the long tapering tail to support themselves, by twisting it round the stems of sea-weeds and other objects. In this position they present a very curious appearance, wonderfully justifying the popular comparison with the horse. The true Syngnathi are of a still more elongated form than the Hippocampi, and have the head in the same direction as the axis of the body. They are commonly known as Pipe-fish, and some species are tolerably abundant on some parts of our coast; the largest British species is said by some authors to attain a length of three feet. The habits of all the species appear to be very similar; they swim about. slowly amongst the sea-weeds, feeding upon minute Crustacea, worms, Mollusca, &c. The most singular part of the history of these creatures, however, is their mode of reproduction. Individuals are found furnished with a curious pouch or cavity at the base of the tail, which is either com- pletely closed, with the exception of a small opening, or concealed by a pair of membranous folds. In the course of the summer this is found filled with eggs; and at a later period, when the fry are : hatched, it appears that they continue for a time to seek shelter from a csere conn danger in this singular cavity. The attachment of the Syngnathi to their young has been noticed by several authors; and Mr. Yarrell says, that he has been assured by fishermen that if the young be shaken out of the pouch into the water, close to the boat, they do not swim away; but when the parent fish is held in the water, in a favourable position, the young again enter the pouch. The most, remarkable circumstance, however, connected with this is that the pouch- bearer is the male fish, and that the female is quite destitute of any such organ, so. THE PLECTOGNATHA. 331 that the ova must actually be deposited by the latter in the abdominal receptacle of her mate. Mr. Walcott’s observations upon a British species, the Synguathus acus, as quoted by Mr. Yarrell, are as follows :—‘ The male differs from the female in the belly from the vent to the tail fin, being much broader, and in having, for about two-thirds of its length, two soft flaps, which fold together, and form a false belly (or pouch). They breed in the summer; the females casting their roe into the false belly of the male. This I have asserted from having examined many, and having constantly found, early in the summer, roe in those without a false belly, but never any in those with; and, on opening them later in the summer, there has been no roe in those which I have termed the female, but only in the false belly of the male.” Mr. Yarrell also states, ! that he has ascertained the correctness of these statements by the dissection of speci- mens, and found that the individuals with the ventral pouch were actually furnished with the usual internal organs of the male sex, whilst those which had no pouch possessed ovaries crowded in the usual manner with eggs. The mode in which the ova are introduced into the ventral pouch of the male is still unknown; but it is remarkable that amongst fishes, wherever any unusual care is taken of the eges and young, this duty always devolves upon the male; whereas, amongst other classes, it appears to be a gencral rule that the care of the young is the special business of the mother; although, ‘in many cases, the male undoubtedly shares in the labours of his partner. Thus the males of many birds assist in collecting materials and im the construetion of the nest, and, in some instances, even take a share in the work of incubation ; but we know of only one instance amongst birds in which the eggs and young are dependent exclusively upon paternal care. Sun-orper VI.—PLEcroGNarHa. General Characters.—In this, the last group of the Teleostia, we mect, to acertain extent, with a combination of the characters of this and the following orders. The bones of the head are perfectly ossified ; but the remainder of the skeleton, and especially the vertebral column, often remains in a state very similar to that which prevails in many of the Ganoid and Cartilaginous fishes. The union of the bones of the head also is . much closer than in the other fishes of the present order; and the principal character of the group consists in the firm attachment of the bones of the upper jaw and palate to those of the cranium. The principal part of the upper jaw is made up of the inter- maxillary bones, which constitute the entire margin of that part of the mouth, and these are firmly fixed to, or rather amalgamated with, the cranial and maxillary bones. The bones of the palate, also, are immoveably attached by a suture to those of the cranium. The head is large; the mouth small; and the opercula are so covered by skin ‘and muscles, that only a small aperture is left for the exit of the water employed in respiration, The body is usually short and stout, and covered with a thick skin, which is sometimes roughened by scattered points, like those in the skin of the Sharks, and sometimes more or less covered with bony plates. The fins are small and soft ; the ventrals usually entirely deficient. The intestinal canal is short and destitute of pyloric cceca, and most of them possess a large air-bladder. ‘Divisions.—The Plectognatha form only two families. The Sclerodermata have the head more or less produced into a snout in front of the eyes; at the extremity 332 THE TRUNK FISH AND BALISTES. of this is the mouth, armed with a series of distinct teeth, which are received into sockets of the jaws, and bear some resemblance to the front teeth in man. The body is covered with bony plates, which in some cases, as in the Trunk-fish (Ostracion, Fig. 45), are of large size and regular shape, covering the whole surface of the body. with a suit of inflexible bony armour. The tail is inclosed in a sort of bony tube; and this and the pectoral fins are the only moveable parts of Fig. 45,—Trunk-fish (Ostracion). the fish; the vertebra cven are usually immoveable. The dorsal fin is single, small, and entirely composed of soft rays. They are generally of small size, and are found only in the seas of warm climates. In the fishes of the genus Balistes (Figs. 46 and 47) and their allies, on the other hand, the dermal skeleton takes the form of regular scales or grains, leaving the skin a certain amount of flexibility ; the ven- tral fins are often represented by a pair of powerful denticu- lated spines, and the back bears two dorsal fins, of which the anterior is formed of strong spinous rays, the first of which is usually very large, and den- ticulated in front. This first dorsal fin is sometimes reduced to a single strong spine; it is supported upon a bone attached to the head, and can be retracted within a groove formed in the latter. These fishes are generally of rather small size; they inhabit the tropical seas, ; and are often adorned with the most brilliant colours. One species occurs on the British coasts. They are but indifferent food, and are said to be- come poisonous at certain seasons from feeding upon the coral-polypes ; this, however, is probably a mistake, as Cuvier.states, that in all specimens opened by him he found nothing but sea-weeds. The second family, the Gymno- donta, is distinguished from the pre- ceding by the structure of the mouth, which, instead of teeth, has the sur- Fig. 47.—Balistes penicilligerus. faces of the jaws covered with a plate of an ivory-like substance: They feed upon sea-weeds, and also upon Crustacea and Fig. 46.—Balistes geographicus. Mollusca, in breaking up the shelly coverings of which these solid jaws are of great GLOBE-FISHES AND SUN-FISHES. 333 service to them. The skin is thick and leathery, usually beset with spines; and the branchial aperture is reduced by it to a very small size. Like those of the preceding family, the majority of these fishes are found only in the seas of warm climates, very few occurring in the waters of Europe. Some of them, belonging to the genera Diodon and Tetraodon, have a large air-bladder, and possess the singular power of inflating the body with air, so as to swell it up into a more or less globular form. This inflation is effected by the passage of air into a large sac, which opens into the esophagus, and extends over the whole of the belly beneath the skin. The air, according to Mr. Darwin’s observations, is swallowed, and then forced into the sac, where it is retained by a muscular contraction. This sac was formerly described as a crop, or first stomach. When thus distended, the great quantity of air collected in the ventral region causes the fish to float with its belly upwards at the surface of the water, in a most helpless position, although it appears to have some little power of directing its course by the agency of the pectoral fins. The distension of the skin also causes the spines with which it is covered to erect themselves in a most formidable manner, affording an efficient protection against the attacks of ordinary enemies. Mr. Darwin states that a species observed by him, on the coast of Brazil, was able to bite most severely ; and that it could eject water from its mouth to some distance, at the same time making a curious noise by the movement of its jaws. A singular phenomenon presented by this fish was, “that it emitted from the skin of its belly, when handled, a most beautiful carmine-red secretion, which stained ivory and paper in so curious a manner, that the tint is retained with all its brightness to the present day.” These fishes, some of which are well known as Sea Porcupines, are of moderate size, some of them measuring above two feet in length, They are, however, of little value ; their flesh being very indifferent, if not absolutely unwholesome., One species has been taken on the coast of Cornwall; it was first described by Pennant, who considered it identical with the Tetraodon levigatus of Linneeus—a species found in Carolina. Mr. Yarrell considers it to be distinct from this, and has described it under the name of T. Pennantii. It attains a length of more than a foot and a-half, and the diameter of the inflated belly, in a specimen of this size, is about a foot. A species found in the Nile, the T. lineatus, which is said to possess electrical properties, is often deposited on the banks of that river by its periodical inundations; on finding them- selves hopelessly deserted by the water, they always swell up their ventral sac, and become dried in this inflated condition, when they are collected by the children and used as balls. The largest species of the family, and indeed of the whole sub-order, are the Ortha- gorisci, which have a soft skeleton and a short, thick body, destitute of tail; the air- bladder and the ventral sac of the preceding fishes are entirely absent, and the fishes possess no power of inflating their bodies. The appearance of these fishes is very peculiar; they look like the anterior portion of some very large fish, cut off through the dorsal and anal fins, and then closed behind and furnished with a broad caudal fin. Of this curious group two species are found in the British seas, although they appear to be rather rare in the waters surrounding our coasts. One of these, the Short Sun- fish, or the Sun-fish, par excellence (Orthagoriscus Mola), is almost of a circular form, with long dorsal and anal fins projecting like handles from its hinder part, the space between these being occupied by a broad caudal fin. About the centre of the body, on each side, is a small pectoral fin, and in front of this, the orifice of the branchial cavity. The other British species, the O. oblongus, is of an oblong form; it has the fins in the 334 THE GANOID FISHES. seme position as the circular species. Both these fishes attain a large size; the Short Sun-fish, in particular, sometimes weighs three or four hundred pounds, and measures four or five feet in length. The flesh of the Orthagorisc: is soft and very indifferent, and possesses a disagreeable odour; qualities which cause it to be very little esteemed. It is, however, fat, and yields a considerable quantity of oil. When alive these fishes have a silvery appearance, and at night they are said to be exceed- ingly phosphorescent; from which circumstance, coupled with their more or less rounded form, it is probable that the names of Sun-fish and Moon-fish, applied to them in different places, are derived. Orprer IV.—GanorsEa. General Characters.—Of the remarkable fishes belonging to this order very few exist at present in our waters. But their fossil remains occur in abundance in almost all the fossiliferous strata of the earth, and, in some of the older formations, constitute almost the only indications of the existence of vertebrated animals upon our planet at the period of the deposition of these strata. It was, in faet, the abun- dance and variety of these fossil remains that first called the attention of naturalists to these fishes, and thus introduced a new and important element into ichthyological classification. Professor Agassiz, in his great work on the fossil fishes, found it necessary to adopt a different system from that generally in use amongst zoologists, as, in many instances, the organs upon which the latter relied for the characters of their groups, were absent or unrecognizable in the remains of the fishes of former ages. Under these circumstances he derived the leading characters for his general classification of Fishes from the form and structure of the scales, or dermal appendages (see page 14), these organs being generally well preserved in fossil specimens ; and this has undoubtedly been of great service to the study of fossil Ichthyology. It cannot be denied, however, that, as is always the case where the structure of a single system of organs is adopted as the basis of a classification, the arrangement of Fishes proposed by Professor Agassiz is evidently artificial, and often violates the natural affinities of the animals, removing closely allied species to a distance from each other, and bringing others into close juxtaposition which have nothing in common but the general form of their scales. This is abundantly evident from the study of the characters of the bony fishes, as already set forth, and it is equally true with regard to the Ganoidea of Agassiz, the establishment of which as a distinct order is the most important zoological point in the work of that eminent naturalist. In strict accordance with his principle of arrrangement, he includes under this order all the fishes which are either entirely or partially covered with bony plates—a character which is exhibited by many of the fishes already referred to amongst the Teleostia, such}as the |Lophobranchia, a con- siderable portion of the Plectognatha and Siluride, and many other fishes belonging to different groups of bony fishes, But a great many of the living representatives of the order Ganoidea, as originally circumscribed by Agassiz, were well known to be nearly allied to other species and groups in which the dermal skeleton never presented the ganoid structure, so that it became necessary either to violate these natural affinities by preserving the order in the form originally proposed by its founder, or to introduce into it new elements which did not exhibit the peculiarities by which it was characterized, and which, of course, would have entirely effaced the boundaries of the order. The perception of this difficulty induced Professor Miiller to SCALES AND SKELETON OF GANOID FISHES. 335 investigate the structure of the living species of Ganoidea, and to compare it with that of the bony fishes on the one hand, and with that of the cartilaginous fishes on the other; and it appears from his researches that a portion of the Ganoidea of Agassiz present characters entitling them to rank as a distinct order, intermediate between the Teleostia and Selachia, but that a considerable number of the fishes originally referred to the order must occupy places amongst the Teleostia. The character by which the Ganoidea were first distinguished from other fishes, was the nature of the dermal skeleton. This consists of smooth, bony plates, covered with a layer of enamel, which are sometimes distributed over the whole surface, some- times confined to the region of the head, or arranged on the sides of the body with intervals of greater or less extent between them. They are frequently of a rhomboidal form, arranged edge to edge, in obliquely transverse rows, the plates forming each of these being attached to those of the next row by a distinct process. In other cases the covering of these fishes is formed of rounded scales, very similar, both in form and arrangement, to the horny scales of the Teleostia, but often very distinct from these in their structure. Like the scales of the Teleustia, these bony plates are formed in capsules of the skin, and the membrane of this capsule appears to extend in the form of a very thin pellicle over their surface. In a few species the skin is quite naked. The skeleton of the Ganoid fishes presents a considerable diversity in its structure, and especially in the extent to which ossification takes place init. Thus in some forms the centre of the vertebral column is reduced to’a mere dorsal cord (chorda dorsalis), terminated by a cartilaginous skull, which is usually protected by external bony plates. The processes forming the arches for the passage of the spinal cord and aorta in these fishes are distinctly ossified. By degrees, however, the ossification extends further ; the skull and vertebral column are scen to be composed of distinct bones; the bodies of the vertebre exhibiting, in some cases, the same structure as in the Selachia, of a series of cartilaginous rings, inclosing a larger or smaller portion of the gelatinous matter of the original dorsal cord; whilst in others the vertebre acquire the form exhibited by those of the Teleostia (see page 11), or even, as in the Lepidosteus, acquire a still higher development, the anterior surface of the body of each vertebra being fur- nished with a convex process, which fits into a cavity of the posterior surface of the preceding one. Thus the structure of the spinal column shows that the Ganoid fishes should occupy a position intermediate between the Teleostia and the Selachia, as the peculiarities of both these groups are reproduced in different members of the order; and the Lepidosteus even appears, in this respect, to approach the higher classes of Vertebrata, the Reptiles and Batrachia, in which its peculiar vertebral conformation is first met with. In the compound structure of the lower jaw also, the Lcpidostews presents a considerable resemblance to the Reptiles. The structure of the fin-rays partakes of the same diversity as that of the skeleton. They are all, with the exception of the first rays in some of the fins, of a soft and flexible consistence ; but in some cases they are entire, in others divided like the soft rays of most of the Teleostia. In many cases the edges of the caudal fin, and the anterior margins of the other fins, are covered by a series of small bony pieces, called fulera, which are often so acutely pointed as to give the edge of the fin a strongly serrated appearance. In number and position, the fins resemble those of many of the bony fishes. The pectorals are always present, as are the yentrals, with a few doubtful exceptions; the latter are always placed on the ebdomen, and from this circumstance the living Ganoid 336 ANATOMY OF GANOID FISHES. fishes were arranged by Cuvier and other naturalists with the abdominal Physostomata. The dorsal and anal fins present much the same differences of size and position as the corresponding organs in the Teleostia; but the arrangement of the caudal fin is fre- quently very different. In some cases the spinal column terminates at the middle of the caudal fin, which thus occupies the extremity of the body as in the fishes of the preceding order; whilst in others the extremity of the spine is continued in the form of a pointed process, beneath which the rays of the caudal fin are attached. Of these s two forms of the caudal extremity, the former, which is denominated homocercal, is characteristic of the Teleostia, the lat- ter, called heterocercal, of the Selachia ; and the Ganoid fishes exhibit a tolerably gradual passage from the one to the other. In their internal anatomy, the Gan- oidea present the same peculiar combin- ation of the characters of the other two great orders of Fishes. Thus the arterial bulb, as that portion of the branchial artery which is situated immediately in front of the heart is called, instead of being formed merely by a thickening of the walls of the vessel, as in the bony fishes, is furnished with a distinct muscu- lar coat (Figs. 48 and 49), by which it is enabled to act as a sort of supplementary heart, or elongated ventricle, in the pro- Fig. 48. Fig. 49, pulsion of the blood through the branchial Fig. 48,—Heart and arterial bulb of Lepidosteus. vessels; and to fit it more completely for a, ventricle; b, auricle; ¢, arterial bulb; d, the performance of this office, it is fur- branche eT Uiatinuation of the artery; g, nished internally with u great number branches leading to the opereular branchiz. of valves (Fig. 49), to prevent the return Fig. 49.—The arterial bulb cut open. == of the blood. This conformation is ex- ty enti Ps Tare cule coat of the arteriat hibited also by the Selachia, although bulb; d, opening for the posterior branch from the number of valves contained in the which ¢ e the branches leading to branchie rise. arterial bulb ig much smaller in them than in the Ganoidea; but the Teleostia are only furnished with a single pair of valves at the aperture leading from the heart into the artery, and the latter is quite destitute of the muscular coat. In the structure of the branchie the Ganoidea agree with the true bony fishes. They have all free, pectinated gills, contained in a cavity which is protected by an operculum, and closed beneath by a branchiostegal membrane, which is frequently furnished with branchiostegal rays. In addition to the regular branchive, there is frequently a supplementary branchial organ (the opercular branchia) attached to the interior of each operculum; and below this a false gill or pseudobranchia, which receives only arterialized blood. Insome cases the top of the head is furnished with a pair of spiracles, a structure which occurs amongst the Selachia, but is never met with in the bony fishes. An air-bladder is always present; it communicates with the pharynx by a duct, as in the Physostomata. CLASSIFICATION OF GANOID FISHES. 337 The intestine is often furnished with a spiral valve, as in the Sharks and Rays. The arrangement of the optic nerves is also very different from that which prevails amongst the bony fishes. In the latter these nerves cross, so that each nerve runs to the eye of the side opposite to that from which it takes its rise. In the Ganoidea, on the contrary, the optic nerve runs to the eye of its own side, and the two nerves meet and unite at some little distance from their origin. Divisions.—Professor Miiller divides the living Ganoid fishes into two great groups, the Holostea, with a perfectly bony skeleton, and the Chondrostea, with the skeleton cartilaginous, and the centre of the vertebral column composed of a continuous soft chorda, The application of this rule to the fossil fishes of this order is, however, attended with considerable difficulties, as, according to Agassiz, species agreeing closely in their general characters with the former section, exhibit in the structure of their skeleton an approach to the second. Professor Vogt, deriving his classification from the forms of the dermal skeleton, divides the Ganoidea into three principal groups or sub-orders—the Cyclifera, in which the scales or plates covering the body are rounded, and lie over each other in the same manner as those of the true bony fishes; the Rhombifera, which have the body clothed with quadrangular bony plates; and the Loricata, which are either entirely naked, or have the head, and often the anterior part of the body, more or less covered with irregular plates of, bone. The last of these groups corresponds with the Chondrostea of Professor Miller, and the two others may be regarded as equivalent to his Holostea; and as they appear to be more nearly related to each other than to the Chondrostea, and may very well be included in a single group, we shall retain Professor Miiller’s sections, especially as the principal characters upon which they are founded are exactly applicable to all the living species, the only examples to which we can satisfactorily appeal. Sus-orprr I.—Ilonosrera. General Characters.—The fishes belonging to this sub-order, both recent and | fossil, are distinguished by having the entire surface covered either with scales or bony plates. In the diving species, the skeleton acquires a bony consistence, and, in some cases, the ossification of the bodies of the vertebre even proceeds to such an extent as to depart entirely from the ordinary piscine type, and to present no small resem- blance to the structure prevailing in many Reptiles. In the form of the body and the structure of the head these fishes resemble those of the preceding order; the head in particular is never covered with a system of dermal bones. Divisions.—The differences in the structure of the dermal covering exhibited by the fishes of this sub-order enable us to divide them readily into two principal : Ke hey 1b groups. In one of these, the Cyclifera of Fig. 50; Beales of Ganvid: Fishes: Vogt, the body of the fish is covered with 4, of Lepidotus; 3, of Glyptolepis. rounded overlying scales (Fig. 50 4), presenting a considerable resemblance, both in form and disposition, to those of the ordinary bony fishes. In some instances they are even of the same horny texture; and this is the case in the only living representatives of the group, the species of the genus Amia (Fig. 51), which, in x feos 338 THE ROUND-SCALED GANOID FISHES. fact, have generally been regarded as truc Teleostia. Others have similar horny scalcs, covered with a layer of enamel, whilst others again are furnished with scale-like bony plates. The character of the dermal covering is not, however, the only point in which the Cyclifera depart somewhat from the normal Ganoid type and approach the true bony Fishes ; the fins are entirely destitute of fulcra (see page 63), and in other respects exactly resemble those of the Teleostia; the arterial bulb (page 64, Figs, 48 and 49) has but a scanty muscular coat, and contains only two rows of small valves, and the spiral valve in the intestine becomes exceedingly small. None of these fishes have opercular branchiz. The nearest approach to the Teleostia is made by the family Amiide, the only family of this group of which we have living representatives (Fig. 51). They are clothed with small horny scales, usually covered with a layer of enamel, as are also the bones of the skull, over which avery thin skin is extended. They are nearly homocercal (the caudal fin occupying the whole posterior extremity of the body) ; but the spinal column turns up slightly at its extremity, so that the larger por- tion of the fin is situated below its termination, giving it, as it were, an indication of the heterocercal struc- ture which prevails amongst many of Fig. 51.—Amia marmorata. the other members of the order. The species of the genus Ama inhabit the rivers of the warmer parts of America, where they feed on minute Crustacea. They are of small size, and but little valued as food. In the fossil Cyclifera, the scales are of a bony consistence. They form two families, of which one, the Celacanthide, is characterized by having the scales rather small, and the perpendicular fins of extraordinary size, all placed upon the hinder extremity of the body, so as to present the appearance of a single enormous fin. There are always two dorsal and anal fins, and the caudal is generally symmetrical; although one genus (G/yptolepis, of which the scales have been figured in page 65) is heterocercal. In the Ioloptychiida, the scales are much larger and thicker than in the preceding family, and the whole surface, both of the bony scales and of the head, is covered with a layer of enamel, and often adorned with elegant raised patterns. ‘They were heter- ocercal fishes, often of large size, and furnished with a formidable apparatus of conical teeth, which proves them to have been of a most predaceous disposition, The arrangement of the dentine and enamel in these teeth is exceedingly curious and complicated. Tn the second section of the Holostea, the Rhombifera of Vogt, which may be regarded as the types of the Ganoid fishes, the bony scales are always of a more or less quadrangular form, usually rhomboidal (Fig. 50 a). They are arranged in oblique rows, and the edges are generally so bevelled that cach scale slightly overlaps the one beneath it; whilst the plates in each row/are usually connected with those in the next by means of peculiar processes. These plates are composed of true bony THE KHOMBIFEROUS GANOID FISHES. 339 matter, and covered with a beautiful layer of glassy enamel. The fins in the Rhom- bifera are always well developed, and generally furnished with fulcra; the ventral fins are abdominal in position, and the caudal extremity exhibits either the homocercal or the heterocercal character. The fossil remains of fishes of this group are distributcd through almost all the strata of the earth; but in our present world it has but few representatives belonging to two genera. The group may be divided into two sections, characterized by the presence or absence of fulcra on the fins, and each of these sections possesses one living genus. 5 Of the group in which the fulcra are deficient, the only living representatives belong to the -family Polypteride. These fishes are distinguished by the peculiar structure of the dorsal fin, which is broken up into a number of separate spines, occu- pying nearly the whole length of the back, and each furnished with a soft fin attached to its posterior surface. The pectoral fins are broad, rounded, and fan-like, supported upon a sort of short, scaly arm ; the ventrals are placed very far back: the anal fin is single, and the tail slightly heterocercal. The body is very elongated and cylindrical ; the head depressed, and furnished with a pair of spiracles, which can be closed by a bony valve. The opercular branchie and pseudo-branchie are wanting, and the branchiostegal rays are replaced by a single large triangular bony plate. The only known species of this family inhabit the African rivers. One (Polypterus bichir), which is found in the Nile, has sixteen dorsal fins, whilst another (P. senegalus), with twelve dorsal fins, inhabits the Senegal. The Nilotic species attains a length of about eighteen inches. It kceps in the muddy bottom of the river, and is only occa- sionally taken ; it is regarded as an excellent fish for the table. Nearly allied to the Polypteride are the Dipteride, a family of fossil fishes which have hitherto occurred only in the Old Red-sandstone. The Diptcride are decidedly heterocercal ; the upper lobe of the caudal fin being much larger than the lower, and the tail running almost to its extremity. The upper surface of the tail is bordered, like the lower surface, with a rayed fin, but there are no traces of spines or fulcra either on this or on any of the other fins; the pectorals are of considerable size, the ventrals are small, and there are two large dorsal and anal fins, situated opposite to each other, near the hinder extremity of the body. The Acanthodide were also heterocercal fishes, in which the upper surface of the tail was furnished with a small rayed fin, but quite destitute of spines or fulcra, whilst the remaining fins were all furnished with u single strong spinous ray. The dorsal and anal fins were single. The fishes of this family were of small size, and covered with very small bony plates. They are found entirely in some of the oldest fossiliferous strata, the Old Red- sandstone and Carboniferous groups, and they are remarkable amongst the fishes of these early periods, from having the skeleton more distinctly ossified. The family Pycnodontide is composed of homocercal fishes, of a broad, compressed form, which are distinguished from the other Ganoidea by the absence of ventral fins. They were small fishes, which probably derived their nourishment from molluscous animals ; all the teeth of the jaws and palate, with the exception of the front teeth in the jaws, which resemble the human incisors, being broad and flat, so as to adapt them especially for crushing the hard shells of these animals. Their remains are found in several strata, but disappear after the Tertiary period. Of the species in which the fins are furnished with fulera, some are distinguished 340 THE BONY PIKE. by having a double row of those organs along the edge of the tail, whilst others have only asingle row. The only living forms belong to the former series, and constitute, with several fossil genera, the family Lepidosteide. These are elongated Pike-like fishes (Fig. 52), which were formerly associated with the Esocide, and are generally known under the name of bony pikes. They are heterocercal, and both edges of the caudal fin are furnished with a double series of fulcra, as are also the anterior \ margins of the other fins. The jaws are usually produced into a long narrow snout, presenting a great resemblance to that of the Gangetic Cro- codile, and armed with a double series of formidable conical teeth, the internal structure of which is very remarkable. The nostrils are situated quite at the extremity of the upper jaw, which is composed of several pieces bearing teeth; the lower jaw, in like manner, consists of several portions, presenting, in this respect, a close resemblance to that of many Reptiles. The vertebral column also presents a structure such as we meet with in no other fishes, the bodies of the vertebre being regularly articulated together. The Lepidosteide are furnished with opercular branchie and pseudo-branchie ; the branchiostegal membrane contains rays, and the air-bladder is of large size, and divided into numerous cells. The fishes of the genus Lepidosteus inhabit the rivers and lakes of America, especially in the warmer regions. Several species have been described by American authors as inhabiting the fresh waters of the United States; but of these some are no doubt mere varieties. They attain a considerable size, some of them being between Fig. 52.—Bony Pike (Lepidosteus osseus). |. two and three feet in length, and their flesh is said to be very good. The Lepidotide—a nearly allied family, with two rows of fulcral scales on the margins of the fins—are distinguished from the preceding family by their homocercal structure and smaller teeth, which never exhibit the peculiar folded arrangement of their constituent parts which is characteristic of the Lepidosteide. The species of this family are all fossil. The Ganoid fishes with a single row of fulcral scales on the fins are also known to us only by their fossil remains. Like the forms with double fulera, they may be divided into two families, in accordance with the structure of the caudal extremity. The heterocercal species constitute the family of Paleoniscide, examples of which are found only in the older formations up to the Oolitic period. They have a single dorsal fin placed about the middle of the body, and the anal fin is also single, and situated near the caudal. :The homocercal forms, forming the family Dapediide, resemble the | preceding in the number and position of their fins, but the bodies of the vertebre are ossified. They make their appearance in the oolite. Sus-orper I].—CHonprostza, or Loricata. General Characters.—The fishes belonging to this sub-order were arranged by most of the earlier naturalists amongst the Cartilaginous fish, of which they formed, with Cuvier, a peculiar order, characterized by having the free branchie and opercular SHIELDED GANOID FISHES. 341 apparatus of the ordinary bony fishes. They are, in fact, distinguished from the other living species of the order Ganoidea by the nature of their skeleton, in which the centre of the vertebral column is represented by a simple, soft chorda dorsalis, without any indication of a division into separate vertebral bodies. The processes of the vertebrae are, however, generally distinctly ossified. The character of the dermal skeleton is also different. It consists of large, cellular bony plates, which are usually collected together so as to form a strong covering for the head, where they are firmly united to the cartilaginous skull, whilst the remainder of the body is either entirely naked or furnished with a few bony plates, separated by intervals of skin of greater or less extent. In « few species the skin is completely naked. In the recent forms the mouth is always placed on the lower surface of the head, at some little distance from the tip of the snout; but in some of the fossil species, which agree with this group in the general characters of the skeleton and the arrangement of the dermal plates, it is situated, as in the ordinary fishes, at the front of the head. The greater part of the fossil species belong to the family Cephalaspide, in which not only the head, but even a considerable portion of the body, was covered with bony plates, giving these creatures a most singular aspect. So anomalous is the appearance of some of the species, in fact, that for a considerable time after the discovery of their remains, paleontologists were much divided in opinion with regard to their nature ; and some of them were said to be gigantic water beetles, whilst others (such as Tig. 53.—Pterichthys. Pierichthys, Fig. 58) were considered to be allied to the King-crabs (Limi), or to the Trilobites. The fins in these fishes were very imperfectly developed, and some of them appear to have been often entirely wanting. Thus, in the Pterichthys, the only repre- sentatives of the fins appear to be the singular jointed organs which project on each side of the anterior part of the body, and which are undoubtedly the pectoral fins, although certainly under a very curious form. The perpendicular fins are also very slightly developed, and the caudal fin appears to have been always deficient. The remains of these fishes are found only in the most ancient fossiliferous strata of the earth’s crust; they occur in the greatest abundance in the Old Red-sandstone, and entirely disappear in the strata above the carboniferous rocks. Divisions.—The recent Chondrostea form two families, which, however, agree very closely in their general form and organization, and differ principally in the character of the dermal covering. In the family of the Sturgeons, or Acipenserida, the body is elon- gated and fusiform ; the head depressed, produced into a triangular snout, and covered with bony plates, and the body furnished with rows of large tubercular plates. The mouth is funnel-shaped and protrusible, placed on the under surface of the head, and ' 849 THE STURGEONS. in front of it a few barbules depend from the snout. They possess opercular hranchie, pseudo-branchie, ,and spiracles; the opercula are large, the fins well developed, the tail heterocercal, and furnished with fulera along its upper margin. The Sturgeons are generally of large size, and inhabit the seas of different parts of the world; but often ascend particular rivers in great abundance for the purpose of spawning. It is only during their progress towards, and their abode in, the fresh water that the fishery for the Sturgeons can be carried on; as during their sojourn in the sea they appear to frequent such deep water as to keep out of the reach of the nets, and Mr. Yarrell states that he has never heard of an instance of a Sturgeon ‘being taken by line. Two species are found on the British coasts; the Acipenser sturie, or common Sturgeon, is the best known of these. Its usual length is from five to six feet, but a specimen has been taken in Scotland measuring eight feet six inches in length, and weighing two hundred and three pounds ; and Pennant mentions the capture of a fish of this species which weighed four hundred and sixty pounds. The flesh of the Sturgeon is regarded as a great delicacy, its flavour being compared to that of veal; and so highly was it esteemed in former days, that our Henry the First is said to have prohibited its being eaten at any other table than his own. Very recently, any Sturgeon taken in the Thames, within the jurisdiction of the Lord Mayor, was denominated a royal fish, from an old custom that such fish-should be presented to the sovercign. The common Sturgeon is far more abundant in the seas of the North of Europe than on our coasts; it also exists in the Caspian and Black Seas in great quantities, asso- ciated with other species, of which one, the Beluga (Acipenser huso, Fig. 54), attains anenormous size. This fish often measures twelve or fifteen feet in length, and weighs more than twelve hundred pounds; and Cuvier states that specimens have been seen weighing no less than three thousand pounds. It ascends : the great rivers which empty themselves into the seas above mentioned, in company with the common sturgeon, and with two smaller species, the A, Helops and A. Ruthenus, of which the former attains the length of about four, and the latter of two or three feet. The Acipenser Ruthenus, or Sterlet, which abounds especially in the Caspian Sea, and ascends the Volga in great numbers, is regarded as the most delicate ‘species of the genus; but the flesh of the Beluga and of the Scherg (4. Helops) is of inferior quality, and that of the former is even said to be occasionally unwholesome. Nevertheless, this fish is, perhaps, the most important of its family, as, from its sound, or air-bladder, the most abundant supply of fine ésinglass is prepared. The other species also furnish this substance, and to procure it vast quantities of them are captured in the riversof Russia. Another article, prepared from the different species of Sturgeon, is the substance called caviare, which forms an important article of com- merce in the countries bordering on the Mediterranean. It consists of the roe of the female fish, which is cleaned, washed with vincgar, and dried, when it is either pressed into small cakes, or packed in kegs. The roe in these fishes occupies a very great pro- portion of the body, occasionally constituting more than one-third of its total weight ; and as upwards of one hundred thousand of the Beluga alone* are said to be taken * The roe of this species sometimes weighs as much as eight hundred pounds. Fig. 54.—Beluga (Acipenser huso). THE SELACHIA. 343 annually in the Russian rivers, we may form some idea of the commercial importance of this article. The caviare prepared from the roe of the Sterlet is said to be far superior to that obtained from any other 'species; and Cuvier states that it is reserved for the Imperialcourt. The skin of the Beluga is employed by the Russians for harness leather; and the chorda dorsalis of several species is said to be cut in pieces, dricd, and ‘used as food in some countries. The Baltic and the American seas also abound in Sturgeons, the species found in the latter locality being distinct from those of Europe. They are taken in considerable quantities, and their flesh is often pickled and exported to other countrics. The Spatularide, forming the last family of the Ganoid fishes, resemble the true Sturgeons in their gencral form; but their skin is quite naked, and destitute of the bony plates which, in the fishes of the preceding family, cover the head and part of the body. They are also distinguished by having the snout enormously prolonged and compressed, so as to form a thin elongated leaf-like organ, which is sometimes nearly as long as the rest of the body. The opercular apertures are very large, and the hinder margins of the opercula are produced backwards into a membranous point, which attains nearly the middle of the body. The mouth is wide, and very different in its form from that of the Sturgeons; it is armed with numerous minute teeth whilst the animal is young ; but these are lost as it increases in age. ‘Lhe species of this curious family are found only in the great rivers of North America; the first described was the Spatularia folinm from the Mississippi. Orpver V.—SELAcHIA. Genexal Characters.—The great order of the Seachia, including the Sharks and Rays, may be considered to correspond with the typical portion of the Chondroptery- gious or Cartilaginous fishes of Cuvier. That author, however, included amongst his cartilaginous fish the Sturgeons, which we have seen to belong to the Ganoid order, and the Lampreys and their allies, which, except in the soft texture of their skeletons, and the arrangement of the branchial openings, have certainly nothing in common with the highly-organised fishes arranged in the present order. The Sclachia have generally been placed nearly at the bottom of the scale in the classification of fishes; but this opinion of their inferiority has arisen entirely from the imperfect ossification of their skeleton ; in the perfection of their general organisation, they certainly exceed all the other members of the class, and in many respects approach the classes immediately above them so closely that Linnzeus even removed them altogether from the class of Fishes, and placed them amongst the Reptiles as a peculiar order to which he gave the name of Nantes. The skeleton in the Selachia is entirely of a cartilaginous nature. The skull con- sists of a cartilaginous capsule, composed of a single piece, without any indications of sutures. The structure of the jaws varies considerably. In the Chimeride the upper teeth are supported upon the front of the lower surface of the skull, which also takes the place of the palate; but in the Sharks and Rays there is a true moveable upper jaw bearing the teeth, and Letween this and the base of the skull are the rudiments of a true palate. The lower jaw always consists of a single cartilaginous arch, The teeth are very variable in their form. In the Sharks, the most active and predaceous members of the order, the teeth are exceedingly sharp, compressed, and occasionally serrated at the edee: inthe Rays the tecth also sometimes exhibit the samé 344 STRUCTURE OF THE SELACHIA. trenchant character, but in many cases they are arranged in mosaic, and these different forms appear occasionally to be only sexual peculiarities. In some cases the teeth form broad, pavement-like plates, covering the surface of the jaws. The teeth are never inserted into the jaws, but are simply retained in their position by the strong skin of the gums. They are ar- ranged in numerous rows upon the rounded edge of the jaws, those of the outermost row standing perpendicularly, and being the only ones in use, whilst those of the inner \ rows are inclined inwards, and only acquire the perpen- dicular position when they move forward to take the place of one of their fellows that has been worn out by long use. The spinal column is sometimes a simple chorda dorsalis, which occasionally exhibits indications of segmentation, and sometimes composed of a regular series of cartilaginous vertebrae, furnished with the same conical cavities as in the bony fishes. The arches of the vertebre are, however, generally cartilaginous, even in the forms with a con- tinuous dorsal chord; and in those which have the bodies of the vertebra cartilaginous, the bases of the processes are usually inserted into peculiar sockets of those bones, The pectoral fins are attached to a strong cartilaginous arch, which usually, as in the bony fishes, depends from the hinder part of the skull. The ventral fins are always situated at the hinder part of the abdomen, on each side of the anus; and in the males they are furnished with curious cylindrical appendages, which are probably organs of adhesion. The perpendicular fins vary considerably in number and position, as in the preceding groups of fishes, and some of them are frequently wanting. The tail is usually heterocercal. The fin rays are exceedingly numerous, and of a horny texture, very different from that of the rays of the fishes of any other group; but the fins are also frequently provided with a strong hollow spine, composed of dentine, and usually serrated behind; this is supported upon a moyeable cartilaginous piece, and often constitutes a formidable weapon. The skin is sometimes quite naked, but usually bears a number of larger or smaller fragments of dentine, which are sometimes in the form of scattered spines, separated by intervals of naked skin, but in other cases are distributed in minute grains over the whole surface. The Selachia are especially distinguished from the other fishes by the structure of their branchiz. The branchial arches are fixed, and the branchial lamine, besides being attached by their bases to the arches, are also fixed by the whole of one margin to a series of partitions, which thus bear a series of laminz on each side of them. In this manner a series of branchial sacs is formed, which open into the pharynx by separate slits, and also usually possess separate external apertures to allow the water employed in respiration to pass off. The usual number of these openings is five on each side; but in some cases there are six, and even sevenof them. In the Chimeride _ there is, however, only a single external opening; and this character induced Cuvier to place these singular fishes with the Sturgeons in his order of Chondropterygii with free branchiz, although the internal structure of the branchial apparatus is the same as that of the typical Selachia. oY me " Fig. 55.—Mouth of Shark. STRUCTURE AND REPRODUCTION OF THE SELACHIA. 345 The arterial bulb in the Selachia exhibits the same muscular coat and apparatus of internal valves that we have already described as existing in the Ganoid fishes; but the valves are generally less numerous than in the recent species of that order. The intestine is also furnished with a spiral valve, which often attains an extraordinary degree of development. ‘There are no pyloric ceca, but the pancreas is in a glandular form. The nervous system exhibits a marked superiority over that of the ordinary fishes, the volume of the cerebral hemispheres being much greater (see Fig. 15, B); and the optic nerves present the same arrangement as in the Ganoid fishes. The Selachia are also the only fishes in which the auditory cavity is in communication with the outer world; the eyes are in some cases furnished with nictitating membranes, and the nasal sacs are of very complicated construction. The reproduction of these animals presents several remarkable peculiarities, and differs considerably from that of most fishes. Thus most of them produce living young, which are developed in an enlarged portion of the oviduct, where they lie free, and surrounded by an albuminous liquid, which appears to assist in their nutrition during the period of development. It is even said that in one species, at least, the yelk-sac attaches itself by means of little appendages to the walls of the oviduct, thus forming a connection with the parent such as we only meet with elsewheré amongst the Mammalia. Some spe- cies, on the other hand, produce ova, which are inclosed in hard, horny, quadrangular shells, usually furnished with a pair of filamentous processes at each ex- tremity (Fig. 66). These egg-cases are furnished with slits to allow the passage of Fig. 56.—Egg-case and Young of Dog-fish. water to the embryo, which lies coiled up in their interior until its development is sufficiently advanced, when it makes its escape through an opening at the extremity towards which its head is situated. The filamentous processes of these egg-cases are said to scrve for their attachment to sea-weeds, so as to prevent the young animal from being the sport of the waves; the empty cases are constantly to be found thrown up on the beach, and they are well known at the sea-side under the name of Mermaid’s-purses, Sea- purses, &c. The embryo exhibits one remarkable peculiarity which appears greatly to justify the position of this order in the immediate neighbourhood of the Batrachia. Before its exclusion the yonng fish is furnished with external filamentous branchia, like those which exist in the tadpoles or larve of the Batrachia, a character which we meet with in no other group of fishes. The Selachia are all inhabitants of the sea, although some of them occasionally frequent the estuaries of large rivers. They are all of large or moderate size, some species attaining gigantic proportions, when their voracity renders them objects of terror to the inhabitants of the coasts on which they occur. Divisions.—They may be divided into two primary groups or sub-orders—the 346 THE CHIMZBAS. Holocephala, which may be recognized by their single branchial apertures on each side, and the Plagiostomata, in which each branchial sac has a seprrate opening. Sus-orpER I.—HoLocePHana. The Holocephala make the nearest approach to the Sturgeons, and were, in fact, included in the same order with them by Cuvier. They have a continuous chorda dorsalis, with cartilaginous neural arches and transverse processes. The skull is short and rounded, and its anterior margin takes the place of the upper jaw, and supports the teeth, which consist of broad plates, of which the upper jaw bears four, the lower one only two. The eyes are very large, but without eyelids. The nasal cavities are very large and convo- luted; they open on the lower part of the snout, in front of the mouth, which is of small size. On each side of the neck there is a single branchial aperture, which is furnished with a sort of rudimentary cartilaginous operculum, and which leads down to five distinct branchial sacs, with separate openings into the pharynx. There are two dorsal fins, of which the anterior is rather short, triangular, furnished in front with a very large spine, and sitnated immediately over the large, powerful pectoral fins; the anal fin is small, and the tail heterocercal. The skin is perfectly naked. The Holocephala are all oviparous, and their eggs, like those of the Sharks and Rays, are inclosed in a strong, horny capsule. They form a single family, the Chimeride ; Linneus having applied the name Chimera to them from their singular appearance, especially when badly stuffed. ‘The best known species is the Northern Chimera (Chimera monstrosa), which is called the Sea-cat, and the King of the Herrings, in different localities. It is three or four feet long, of a silvery colour, spotted with brown; the snout is obtusely conical, and the extremity of the tail is produced into a very long tapering filament. It is a native of the northern seas, and usually follows the shoals of Herrings during their periodical migrations towards the shore, feeding upon these and other small fishes; it is also said to feed on Meduse and Crustacea. The males are furnished with bony appendages at the base of the ventral fins, and also with a singular plate, terminated by a spinous disc, on the crown of the head in front of the cyes; the possession of this appendage, coupled with its habit of following the Herrings, has no doubt given rise to the fanciful appellation.referred to above. This fish occurs occasionally on the British eoasts; its flesh is coarse, and very indifferent as food; but the oil furnished by its liver is said to be employed by the Norwegians in diseases of the eyes. In the seas of the southern hemisphere, the place of the Chimera monstrosa is taken . by another species, the Callorhynchus australis (Fig. 57), so called from its having the snout produced into a cartilaginous process, which is bent backwards at the extremity, so as to acquire no small resemblance toa hoe. It is of about the same size as the northern Chimera, and is of a silvery colour, tinged with yellowish brown. The tail is not produced into a filament. Fig. 57.—Southern Chimiera (Callorhynchus australis.) THE DOG-FISHES. 347 Svs-orprr IT.—Piaciostomars. General Characters.—In the Plagiostomata, the centre of the vertebral column is usually more or less ossified, and divided into separate vertebrae, and even where it still forms a continuous chorda dorsalis, the boundaries of the vertebre are indicated by transverse partitions. The union of the vertebral column with the skull is effected by means of a joint, which contains a conical cavity. The skull, as in the preceding | sub-order, forms a simple cartilaginous capsule; but its anterior margin no longer performs the office of 2 jaw, the upper jaw being formed of a separate cartilaginous arch. The mouth is very wide (Fig. 55}, and placed quite on the lower surface of the body, at some distance from the extremity of the snout, which is greatly inflated to give room for the enormous nasal capsules. The mouth is always of an arched form, and contains numerous rows of teeth, of which the inner are continually coming up to replace those which have been long in use. The branchial sacs are completely separated, and furnished with distinct apertures for the passage of the water which has been employed in respiration ; these, in the Sharks, are placed at the sides of the neck, but in the flattened Rays they are situated on the lower surface of the body, a little behind the mouth. On the upper surface of the head, behind the eyes, is a pair of spiracles, which communicate with the pharynx. The skin is almost always furnished with the hard bedies already described, either in the form of scattered spines, or of minute grains covering the whole skin. Divisions.—These fishes are divided by Professor Miiller into numerous families, which, however, may all be referred to one of two groups, the Sharks (Sgualina), and the Rays (Ratina). The Sharks are at once distinguished by their clongated, spindle-shaped bodies, their branchial apertures placed on the sides of the neck, and their pectoral fins of the ordinary form and position. The symmetrical tail is large and fleshy, furnished with powerful fins, which render it a most powerful agent in progression; the nose is usually conical and pointed, the mouth large, and armed with most formidable cutting teeth, and the upper surface of the head is frequently furnished with a pair of suiiwoles, although these apertures are often wanting. This group includes the numerous species of Sharks and Dog-fishes, which may be distribuicd into the following families. The Stylliide, or Dog-fishes, have a short, blunt snout, an anal fin, two dorsal fins, placed further back than the ventrals, and small branchial apertures, of which a part stand over the base of the pectoral fins. The top of the head possesses spiracles, and the teeth are sharp and tongue-shaped, with three points, a large one in the middle, and asmall one on each side; but some of the teeth, which appear to be specially intended for cutting, are finely senate along both their edges. The Dog-fishes are also distin- guished from the other Sharks by their oviparous reproduction ; the egg-case, with its little inmate, has, already been figured (Fig. 56). The Dog-fishcs are amongst the smallest of the Sharks, the largest British species measur ing no more than two or ti.:cc feet in length. Three species inhabit the British seas, avons one of them occurs in great abundance, and is often caught by lines intended for other fish. It is, however, of little or no value. Both species are of a reddish tint, mottled in the one with small black spots, and adorned in the other with a smaller number of Jarge round black and white spots. The skin of thesc fishes is commonly used by cabinct-makers as a fine rasp ; it is known to them by the name of “ fish-skin.’ 318 THE SHARKS. The Carcharida, or true Sharks, have acute triangular teeth of very large size, two . Spineless dorsal fins, of which the anterior is situated above the, space between the pec- torals and ventrals, and a more or less forked tail (Fig. 58). The spiracles are wanting. g» To this family belong the large Sharks of hot climates, of the ferocity of which, in attacking even human beings when swim- ming, such wonderful stories are often re- lated by travellers. Of Fig. 58.—Thresher, or Fox Shark (Carcharias Vulpes). these the most celc- brated is the White Shark (Carcharias vulgaris, Fig. 58*), which appears to occur in almost all seas, is tolerably abundant in the Mediterranean, and, according to some natu- ralists, has even been taken near our own coasts. This terrible fish attains a length of twenty-five or thirty feet; its mouth is very wide, and armed with acute, serrated, cutting tecth, with which, if some of the accounts of travellers are to be believed, it can readily bite through the body of aman. It constantly follows ships in warm climates, apparently for the sake of the garbage and other matters which are thrown overboard; but sailors are generally averse to such a formidable neighbour, and means are soon taken to get rid of him. The Shark bites boldly at almost any bait of sufficient size to suit his enor- mous throat, and may generally be taken easily by putting a piece of pork upon a large hook attached to a chain, and trailing this tempting bait at the stern of the ship. When hauled on board the first operation is usually to cut off the tail, as its great strength renders its blows exceedingly dangerous. Another species, which, although an inhabitant of the Mediterranean, is not unfrequently met with on our south coasts, is the Blue Shark (Carcharias glaucus). It sometimes reaches the length cf eight feet, and is an exceedingly bold and voracious animal, which is regarded by the fishermen as one of their greatest enemies. ‘The Blue Sharks live almost entirely upon fish, of which they must devour a great number ; and they often annoy the fishermen greatly by hanging about the boats, seizing the fish that are being drawn up, and not only biting through the lines for the legitimate purpose of getting off with their prey, but even sometimes, apparently, for the mere pleasure of the mischief. Sometimes, however, they get hooked when thus engaged, when, if they cannot bite through the line, they immediately roll themselves round so Fig. 58*.—White Shark (Carcharias vulgaris). THE SHARKS. 349 as to wind the line upon their bodies; and Mr. Couch states that “this is sometimes done in such a complicated manner, that he has known a fisherman give up any attempt to unroll it as a hopeless task.” To the drift nets employed in the Pilchard fishery, on the Cornish coast, it is an equally dangerous enemy, passing along the whole length of the net, and picking out the Pilchards by biting them away, together with the portion of the net in which they are entangled. Many of the old writers on natural history celebrate the affection of the Blue Shark for its young; and even in the ~ present day it is a common belief amongst sea-faring people that at the approach of danger the young Sharks enter the mouth of their parent and take shelter in its belly. Another British species is the Fox Shark (Carcharias Vulpes, Fig. 58), which is also known as the Sea Fox, the Sea Ape, and the Thresher; the latter name is said to be applied to it from its habit of defending itself by blows with its tail. It is said to attain a length of fifteen feet, and specimens have been taken in the British seas thirteen feet long. Its appearance is rendered very remarkable by the great length of the upper lobe of the tail. The Zygenide, or Hammer-headed Sharks, are very closely allied to the Car- charide, and differ principally in the singular form of the head (Fig. 59), which is very broad, forming a projection on each side of the front of the body, at the extremityof which the eyes are situated. The head bears a considerable re- semblance to the head of a hammer, whence the name commonly applied to these creatures. Several species of these curious fishes occur in various parts of the world; the common species, Zygena malleus, is found in the Me- diterranean, and also in the Fig. 59.—Hammer-headed Shark (Zygena malleus.) warm parts of the ocean, and attains a length of about twelve feet; it is very ferocious, and is even said to attack men when bathing. In the Lamnide, the two dorsal fins are destitute of spines, the spiracles are large, and the branchial apertures, which are of very large size, are all situated in front of the base of the pectoral fins. There is an anal fin; the nose is usually long and pyramidal, the mouth very wide, and the teeth lingulate, not serrated, but sometimes furnished with small lateral points. In these Sharks, the caudal fin is broadly forked, and the two lobes are nearly symmetrical. Three species are found in the British seas. Of these the Porbeagle (Lamna cornubica), and the Beaumaris Shark (ZL. monensis), rarely attain a length of nine feet, whilst the third species, the Basking Shark (Selachus maximus), is the largest of the whole group of Sharks, measuring occasionally no less than thirty-six fect. Notwithstanding its great size, this fish appears to be the least ferocious of the Sharks, and its teeth are smaller in proportion than those of any other species. It appears to Oe 350 THE SHARKS. be sluggish in its habits, frequently lying motionless, sunning itself at the surface of the water, from which circumstance the name of Sun-fish is given to it on the north coast of Ireland. When thus engaged, it will sometimes allow a boat to touch it before moving. It does not appear to feed on fishes, the stomach, when examined, containing a pulpy mass, apparently consisting of the remains of invertebrate animals ; Linneus states that it feeds on Meduse, whilst Pennant attributes to it a vegetable diet. The branchial apertures are very large, surrounding the greater part of the neck. It is taken occasionally for the sake of the liver, which yields a large quantity of oil. The usual way in which it is captured is by the harpoon; but when struck with this instrument, it is said to plunge down into the water with such force and rapidity as to render it rather a dangerous prize. The Galeide have an anal fin and spiracles; their two dorsal fias are destitute of spines, the caudal exceedingly unsymmetrical, and the spiracles are very small. Two species occur commonly in our seas. One of these, the common Tope (Galeus vulgaris), known on some parts of the coast as the Penny Dog andthe Miller’s Dog, attains a length of about six feet, and is very injurious to the fishcrics. Its teeth are triangular, sharp, and serrated externally ; and, like the Blue Shark, when caught on a line, it frequently bites through, and thus gets away ; butif it fails in this, it has recourse to the same expedient of twisting the linc round the body. Its liver furnishes an oil, and this is tho only use that is made of it when caught. The other British species, the Smooth Hound (Mustelus levis), although resembling the preceding in its form and general characters, is remarkably distinguished by the structure of its teeth, which are flat, and cover the jaws with a sort of mosaic, similar to that which prevails amongst the Rays. From this circumstance it is called the Ray-mouthed Dog in Cornwall. This fish is one of the smallest of the Sharks, and feeds principally upon Crustacea, which its pavement-like teeth are admirably adapted for crushing. The Wotidanide resemble the Lamnide in many respects; but they have only a single dorsal fin, and the branchial apertures are six or seven in number. These are comparatively small fishes, measuring about three feet in length: two of them are common in the Mediterranean. The Cestraciontide, of which we have only a single living representative, although their fossil remains are tolerably numerous in some of the older formations, arc distin- guished by the form of their teeth, which are arranged upon the jaws in a payement- like form, those in front being pointed, whilst the hinder ones are converted into broad, flat grinders, The form of the body is short and stout; the head is large, with promi- nent eyes; and the mouth is placed at the front of the head. There are two dorsal fins, each furnished with a short, stout spine, a single anal fin, and a pair of spiracles. The only species, the Cestracion Phillipsit, is found in the Eastern scas, especially on the coast of New Holland. In the Spinacide the general form of the body resembles that of the Galeidw, and, as in those fishes, there are two dorsal fins, but the anal fin is wanting. The teeth are small and acute ; the spiracles are distinct ; and both the dorsal fins are furnished with a strong spine. A very common Ruronean species is the; Picked Dog-fish (Spinax _Acanthias), which is found in the European seas, and attains a length of about three feet. They are said to afford the best food of any of the Sharks, and are commonly brought to the markets of sea-side towns. The flesh is often dried ; the liver yields a large quantity of oil; and when they occur, as they sometimes do, in vast quantities, their intestines are employed asmanure. Mr. Couch states that he has heard of twenty THE SHARKS. 351 thousand of them being taken in a sean at one time. It is, however, as a general rule, rather a nuisance to the fishermen, often biting off great numbers of their hooks.. The spines of the dorsal fins are employed by the Picked Dog-fish as weapons of offence ; it bends itself into the form of a bow, and then, by a sudden motion, strikes out with great force; and so accurate is its aim said to be, that if it be touched upon the head, it will inflict a wound upon the aggressor without the least injury to its own skin, The Scymnide resemble the Spinacide in most of their characters, including the absence of the anal fin, but the dorsals are destitute of the strong spines characteristic of the preceding family. The Scymnide are also shorter and thicker in the body, and the lobes of the caudal fin are more equal. Some species of this family attain a considerable size, the Greenland Shark (Scymnus borealis) sometimes measuring upwards of fourteen feet in length. It is occasionally found on the northern coasts of this country, but generally inhabits the Arctic seas, where it is one of the greatest enemics of the Whales, attacking and biting those enormous creatures with the great:st perti- nacity. When it meets with a dead whale, it scoops hemispherical pieces out of the body with its enormous jaws, which border a mouth of from twenty to twenty-four inches in breadth ; but although the Sharks are constant attendants upon the whale- fishers when they are engaged in cutting the blubber from their captures, and the men not unfrequently slip into the water amongst them, Mr. Scoresby states that he never heard of an instance of their being attacked. It is exceedingly tenacious of life, and so indifferent to wounds that it will return again to its banquet after having been driven off by a stab with a knife which might have been supposed quite sufficient for its destruction. When eut up, also, the different parts of the body appear to retain a certain amount of life for some hours, and even after decapitation it is said not to be safe to trust the hand between its formidable jaws. Whales, however, are not 1}: only food of the Greenland Shark; it condescends also to devour small fishes and crabs. ° It appears to be particularly liable to the attacks of a parasitic crustaceous animal, one or two inches in length,* belonging to the family Lerneide (vol. i., p. 298), which attaches itself to the eyes, and occurs so constantly in this situation that it was formerly regarded as a peculiar natural appendage of the eye. ‘This parasite, no doubt, has a very injurious effect upon the sight of the animal; and the sailors commonly believe that the Greenland Shark is totally blind, as it never exhibits any desire tu escape, even when threatened with a blow from a knife or lance. Several other species of this family are found in the seas of different parts of the world. The Squatinida, at the first glance, exhibit a considerable resemblance to the fishes of the following group, the body being much depressed, and the pectoral and ventral fins large and broad, giving them a discoid form. Like the fishes of the preceding families, they are destitute of an anal fin, and have a pair of spiracles on the top of the head, which is very broad, and bears the eyes on its upper surface instead of on the sides. The mouth is very wide, and situated quite at the front of the head; and the branchial orifices are long, and placed in a cleft which separates the large pectoral fins from the head. Both the pectoral and ventral fins are broad and extended laterally; there are two dorsal fins placed upon the caudal portion of the body behind the ventrals; the anal fin is wanting, and the caudal is nearly, or quite, symmetrical. The typical species of this family, the Sguatina angelus, is not uncommon in our seas ; it is known both in England, and in several other countries, by the name of the Angel, which certainly, as hinted by Mr. Yarrell, was never given to it for its beauty. It is * Lernea elongata of Grant. 2a THE RAYS. also called the Monk-fish in some places, probably from the hooded appearance of its head; and Mr. Donovan states that its form has also attained for it the name of the Fiddle-fish. It is said sometimes to attain a length of seven or eight feet, and is an exceedingly voracious fish, swimming close to the bottom of the water, and feeding principally on the common flat fishes, which are to be met with in abundance in such ' situations. Its flesh was formerly held in some esteem, but it is now considered coarse and seldom eaten. The skin, however, is much used for polishing cabinet work, and also affords a fine sort of shagreen, A species found in the Mediterranean, the Squatina aculeata, is distinguished by having a row of strong spines along the back. The second group of the Plagiostomata, the Razina, including the fishes commonly known as Rays, are distinguished at the first glance by the singular flattened discoid form of their bodies. The greater part of this disc is made up of the pectoral fins, which are extremely large, and are supported upon a remarkable modification of the bones of the anterior members. The scapular arch is firmly attached to the hinder part of the head, and its two sides are also united above the vertebre of what may be called the cervical region, which are amalgamated together so as to form a continuous cylinder. Thetwo sides of the scapular arch also unite below, so that they form a complete ring, from each side of which long curved cartilages are given off, which serve to support the rays of the pectoral fins. These cartilaginous supports not only pass backwards from the scapular urch along the sides of the body, but also extend in front of it to the sides of the head, where they unite with other cartilages springing from the apex of the skull, which also support fin rays, so that the whole of both sides of the body, from the point of the snout to the base of the tail, is usually margined with a broad fin. The rays supporting these fins are composed of numerous small cartilaginous joints, and the fins themselves are usually formed by a thick layer of muscles, At the extremity of the body, close to the anus, the ventral fins are situated ; in the males they are furnished with peculiar appendages, like those of the Sharks. The perpendicular fins are very variable in their development, but always of small size; the caudal fin is often wanting, and the dorsal and anal fins, when present, are always placed upon the tail, often close toits extremity, and the former are frequently furnished with long spines, similar to those of many Sharks, which sometimes exist without afin, forming a most formidable weapon, with which the fishes are said to inflict dangerous wounds. The eyes are situated on the upper surface ; but it must be borne in mind that this is the back of the animal, and not the side, as in the ordinary flat fishes; behind the eyes are a pair of large spiracles. The lower, or ventral surface, is very flat, and upon it are situated the orifices of the nose and the mouth, the branchial apertures (five on each side), and the anus. The mouth is smaller in proportion than in the Sharks, and the jaws are covered either with numerous rows of small pointed teeth, or with a sort of mosaic flattened molars, which sometimes take the form of broad bony plates. It is remarkable that in some species the adult males possess teeth of the former descrip- tion, whilst’ the young males and the females are furnished with grinding teeth. The skin is naked, but in most cases beset with a considerabie number of spines, or thorns, which are sometimes scattered over the surface of the body, sometimes arranged in rows, especially along the tail. The structure of these spines is very peculiar. They consist of a sort of cartilaginous cup imbedded in the skin, from the concavity of which springs an acute spine formed entirely of dentine, and in many cases exactly resembling a true tooth in its structure. They are of very various sizes, sometimes mere prickles, whilst in other cases they constitute most formidable offensive weapons, TIE RAYS—THE SAW-FISH. 353 The Rays are all oviparous, and their eggs are inclosed in brown, leathery capsules of a quadrangular form, like those of the Dog-fishes, and furnished, like these, with elongated processes at their angles. They are all marine, and many of them attain a very large size. Some of them, in fact, acquire almost gigantic proportions, and weigh several hundredweights. We are told by some writers, that in Marseilles they may occasionally be seen so large, that when they are hung from the second floor of a house the tail will still touch the ground; and there is a record of the capture of a gigantic Ray on the coast of New Jersey which required the united efforts of six oxen, two horses, and two-and-twenty men, to get it safely landed! This fish was described as measuring eighteen feet in diameter, and its weight is said to have been five tons. Another enormous species is said to be an object of great terror to the pearl divers, as it occasionally passes over them, and holds them down till they are drowned; but the degree of dependence to be placed on these statements is very doubtful. Their habits are very predacious; they keep close to the bottom, moving about with a peculiar sliding action in pursuit of the small fishes, Mollusca and Crustacea, which constitute their ordinary food. Divisions.—Professor Miiller divides the Rays into six families. Of these the Rhinobatide appear to unite the characters of the Sharks and Rays in the greatest degree, resembling the former in the general conformation of the body, and even to a great extent in the position of the fins, the pectoral fins being even smaller than those of the Angel Sharks. The first dorsal fin is: situated above the ventrals; the caudal is well developed and unsymmetrical ; and their teeth are in the form of mosaic. The fishes of this family inhabit the seas of most parts of the world, but none have been taken on the British coasts. A Brazilian species, Rhinobatus electricus, is said to possess electrical properties ; but this statement requires confirmation. The most sin- gular form, and the one which exhibits the closest resem- blance to the Sharks, is the Saw-fish (Pristis antiquorumn, : Fig. 60), which has been as- Fig. 60.—Saw-fish (Pristis antiquorum). sociated with the Sharks by some authors, and might, perhaps, be regarded with justice as the type of a distinct family. The most remarkable character presented by this fish consists in the pro- longation of the point of the snout into a sword-like organ, which is armed along its edges with strong, tooth-like spines. With this formidable weapon the Saw-fish attacks even the largest Cetaceous animals, upon which it often inflicts very serious injuries. The true teeth are very small. The species of Saw-fish, of which it is probable there are several, are distributed in the seas of most parts of the world; but they rarely approach the shores. They often attain a length of twelve or fifteen feet. From the Rhinobatide we pass to the family of Torpedinida, or Electric Rays, distinguished by their rounded smooth bodies and by the possession of an electrical apparatus. The latter is disposed in two masses, one on each side of the skull, occupy- ing the space between that capsule and the base of the pectoral fin. It is composed of a multitude of perpendicular gelatinous columns, separated by membranous partitions, which receive an immense number of fine nervous threads, derived from the eighth pair of nerves (nervi vagi). Nearly twenty species of this singular family are known; they Lis 354 THE TORPEDOS. inhabit the seas of all parts of the world, and all probably possess electrical powers. Two or three species are found in the European seas, especially in the Mediter- | ranean, and one or two of these have occurred on the British coasts ; but there appears to be some doubt as to the actual species taken by our fishermen. The electrical powers of the Torpedo were well known to the ancients; and “as long ago as the time of Dioscorides the shock communicated by this fish was recommended for medical purposes, and especially for pains of the head; and this may be considered as the earliest record of the application of electricity to medicine. In later times it was ap- plied to the cure of gout, the patient being directed to keep his foot on the fish until the numbness extended to the knees.” —(Yarrell.) The real object of. the electrical powers with which this and a few other fishes are endowed is not yet very clearly ascertained; and we can only judge from probability that this property is given them partly for their protection from danger, and partly to enable them to obtain food ; and this latter office is probably one of great im- portance to the Torpedo, which is exceed- ingly slow in its movements. Mr. Couch also thinks that the electricity of this animal may have some influence upon Fig. 61.—Anatomy of the Torpedo. The anterior part of the dorsal skin is removed, showing the electrical organs, brain, and nerves. G, brain; }, skin, with its glands; ¢, eye, with the spiracle behind it; d, electrical organ; ¢, branchie ; f, nerves running to the pectoral fin; g, spinal chord ; 4, branches of the nervous vagus the digestibility of the animals killed by it, rendering them “more readily disposed to pass into a state of decomposition, in which condition the digestive powers assing to the electrical organ; i, lateral nerve. i ee ; "4 more speedily and effectually act upon them.” He adds, “if any creature more than others might seem to require such a preparation of its food, it is the Cramp-ray, the whole canal of whose intestine is not more than half as long as the stomach.” The True Rays, or Ratide, have the snout more or less pointed, frequently produced, and the disc formed by the body and pectoral fins is usually of arhomboidal figure. The tail is slender, and bears two small dorsal fins near the extremity; the caudal fin is also sometimes present, To this family belong all the best known species, including the | Slates and Thornback so common in our markets. The British seas are inhabited by eight or nine species, several of which are very common, and some of them attain a large size; Pennant mentions a Skate that weighed two hundred pounds. dant species is the Thornback (Raja elavata, Fig. 62); and this and The most abun' the Homelyn Ray (#. maculata) are the species most commonly brought to the London THE SKATES AND STING RAYS. 355 market, where they are both sold as Skate. The females are usually denominated maids. The Sharp-nosed Ray (R. oxyrhynchus) is said by Mr. Yarrell to be the favourite spe- cies with the French, whose boats frequently visit Plymouth during Lent to purchase Skate. The Raiide are exceedingly voracious animals, devouring great numbers of small fishes, Crustacea and / Mollusca; and the strength of their jaws is so great that they crush the hard shells of the latter animals without difficulty. They are taken both by net and line; when hooked, some of them strug- gle violently. In the family Trygonide, or the Sting Rays, the tail is armed with a long, denticulatcd spine, but bears no dorsal fin; the pec- toral fins are large, and unite in front of the head, and the tect are of small size. The Sting Ray is not uncommon in the Mcditer- ranean; it was well known to the ancients, who attributed the most extraordinary venomous powers to its spine, which, no doubt, from its barbed structure, Fig. €2,—Thornback (Raju elavata). must inflict an exceedingly pain- ful wound. It seems probable, from the observations of some writers, that this spine is deciduous, as specimens have been seen with a second small spine close to the base of the first. The spines of some species of Trygonidz are often used by the natives of savage countries to form barbed spear and arrow heads. According to Mr. Couch, the common Sting Ray (Zrygon pastinaca) of the Medi- terranean, which occurs pretty frequently on our south coast, defends itself in a manner that “shows its consciousness of the formidable weapon it carries on its tail. When seized or terrified, its habit is to twist its long, slender, and flexible tail round the object of attack, and, with the serrated spine, tear the surface, lacerating it in a manner calculated to produce violent inflammation.” It is also said occasionally to strike its prey first with the spine, and afterwards to secure it by twisting the tail round it. Its flesh is said to be very bad. Nearly allied to the Sting Rays is the curious family of the Cephalopteride, which agree with the former ia having the jaws armed with numerous small tecth, and the tail with a long, barbed spine; but differ in the form of the pectoral fins, and in having a small dorsal fin. The head in these fishes projects a little beyond the ante- rior margin of the pectural fins, and-is furnished witha pair of curious little fins, * 356 THE EAGLE RAYS—THE BATRACHIA. which stand out in front of it like horns. The pectoral fins are very wide and pointed. An enormous species, the Cephaloptera giorna, is found in the Mediterranean ; and it ‘seems probable that if there be any truth in the statements already referred to, regarding the gigantic enemy of the pearl fishers, the Ray in question would belong to this group. A specimen of a Cephaloptera has been taken upon the Irish coast, but Mr. Yarrell was unable to determine the species; it measured forty-five inches across the pectoral fins. The Myliobatida, or Eagle Rays, resemble the preceding fishes in most of their characters ; they are, however, destitute of the small horn-like fins on the front of the head, and the jaws are covered with broad hexagonal plates instead of teeth. The tail, like that of the Cephalopteride, is very long and slender, armed with a strong spine and furnished with a small dorsal fin, and the pectorals are very broad and do not meet in front of the head. These fishes are commonly known as Eagle Rays, from the great size of the pectoral fins, which present a considerable resemblance to a pair of wings; they are also called Whip Rays, on account of the form of the tail. The Eagle Ray (Myliobatis aquila) is not uncommon in the Mediterranean, where the wounds inflicted by its spine are so much dreaded by the fishermen, that they always cut off the tail as soon as the fish comes within reach. Several other specics are found in the seas of warm climates. With the Rays terminates the class of Fishes, the only class of strictly aquatic vertebrated animals, and we must now pass to a singular group which, although they possess gills at some period of their existence, always subsequently acquire lungs, and become air-breathing creatures. These are the Crass II.—Barracuia. General Characters.—The singular animals forming this small class have been, and still are, included under the Reptiles by many naturalists. They appear, however, to possess so many remarkable characters, that they may very justly be regarded as constituting a distinct class, approaching the Fishes on the one hand, especially,during their earlier stages of development, and, on the other, presenting a considerable resem- plance to the Reptiles in the mature forms of their higher species. The class, in fact, forms a distinct transition from the strictly aquatic Fishes to the strictly air-breathing Reptiles; and, as might be expected in a group of this nature, the forms, and even the organization of the animals composing it, are exceedingly various. Thus in the lower orders, which approach most closely to the preceding class, we meet with completely fish-like creatures, possessing permanent branchie, and in which the limbs are reduced to a rudimentary condition, and the tail is flattened and surrounded by a fin; in fact, zoologists are still divided in opinion as to whether one of these orders should be referred to this or the preceding class. With the exception of a remarkable order of apodal terrestrial animals, we find that as we advance in the class the limbs are gradually more and more developed, and fitted more especially for terres- trial progression; many of the higher forms are capable of very active motion on the ground, and some even have their habitual residence in trees. The structure of the skeleton also exhibits great differences. The spinal column in some is composed of a continuous chorda dorsalis, inclosed in a fibrous sheath, but furnished with bony superior and inferior arches for the protection of the spinal cord and principal blood-vessels. In others we meet with a repetition of the vertebral column of the bony fishes, composed of separate vertebra, of which the bodies contain STRUCTURE OF THE BATRACHIA. 357 double conical cavities; whilst in the highest forms the vertebre are articulated together by a sort of ball-and-socket joint. The vertebre are usually furnished with ;long transverse processes, which appear to take the place of ribs; the latter are deficient throughout the whole class. The development of the skull partakes of this variable character. In the species with a chorda dorsalis the skull is formed of a simple cartila- ginous capsule, with which the chorda is completely continuous; and the only indica- tions of ossification are to be found in the lateral portions of the occipital bone. In the higher forms the skull is completely ossified; it is always of a broad and flattened form, with enormously large orbits, and possesses one constant character, which enables us to distinguish readily between the skull of a Batrachian and thaf of a true Reptile ; the occipital bone is always furnished with two lateral condyles, which fit into corres- ponding sockets in the first vertebra of the neck. The bones of the upper jaw and palate form a broad arch, which is always firmly attached to the skull; the maxillary and intermaxillary bones assist in the formation of the edge of the mouth, and both these and the palatine bones are usually furnished with teeth. The lower jaw is articulated to a bony process, which usually projects more or less backwards from its point of attachment to the skull, so that the opening of the mouth may not unfrequently extend beyond the base of the skull. The hyoid bone is generally of considerable size, and in many cases gives attachment to a series of branchial arches, which, however, rarely reach the skull, and in the higher forms are reduced to a rudimentary condition. Very few of the Batrachia are quite destitute of limbs, but several possess only a single pair. In the most fish-like forms the anterior limbs are attached, as in the fishes, to the back of the skull; but in all the others the scapular arch is distinct. The structure of the pelvic arch, and the development of the moveable bones of the limbs, varies greatly in the different orders into which the class is divided; but as their modifications will be described in characterising those groups, it will be unnecessary to dwell further upon them here. In the majority of the Batrachia the skin is smooth and naked. It is composed of a soft corium, which usually lies loosely about the body, and is covered by a thin colourless epidermis; it frequently contains numerous glandular organs, which secrete an acrid fluid of a disagreeable odour. A few species are covered with minute horny scales, resembling those of the bony fishes in their structure and arrangement, and some have larger scales of u peculiar composite nature, which have been regarded as analogous with those of the Ganoid fishes. In the development of the nervous system and the organs of the senses, the Batrachia, as a class, exhibit a slight advance upon the Fishes; and the cerebral hemispheres generally constitute the greater part of the brain. The nasal cavities are separated by a partition, and always open into the mouth. The eyes are sometimes rudimentary, and even concealed beneath the skin; but in most of these animals the organs of sight are well formed. In the Frogs they are exceedingly moveable, protected by eyelids, and furnished with a nictitating membrane. In most of the tailed Batrachia the ear exhibits but little advance from the condition of that organ in Fishes; but in the Frogs it has an external opening, furnished with a tympanic membrane, and the labyrinth consists of three semicircular canals and a sac, which is filled with micro- scopic calcarcous crystals. The mouth in these animals is always of large size, and almost always armed with small conical teeth. In a few species the jaws are unarmed, and in others the teeth are in the form of small perpendicular plates. The tongue is usually of large size, and 358 DEVELOPMENT OF THE BATRACHIA. is often capable of being protruded trom the mouth toa considerable distance, when it is employed in the capture of insects. The intestinal canal is short; the liver is large, and usually divided into two lobes; the gall bladder, pancreas, and spleen are always present. "The structure of the respiratory organs indicates more clearly than any other part .of their organization the intermediate nature of these animals. They all possess lungs ; but during their young or larval condition they are always furnished with branchire, and these, in many instances, are persistent throughout the life of the animal. The form and arrangement of the branchial organs will be described hereafter. The heart is composed of three chambers, a single muscular ventricle, and two membranous auricles ; but in some species the partition between the latter is imperfect. ‘The arterial bulb is surrounded by a distinct muscular coat, as in the Ganoid and Selachian fishes ; and from the continuation of this the arteries running to the branchiz and lungs are given off. © The Batrachia are all strictly oviparous animals, although in some species the eggs are retained in or upon the body of the parent until the young have attained a certain degree of development. As a general rule, the ova are impregnated by the male at the moment of their leaving the abdomen of the female ; the eggs are united by a glutinous matter into masses or long chains, which may be constantly seen floating in the waters frequented by these animals. a The development of the young exhibits many points of great interest. On leaving the egg, the young animals are very different in furm from their parents, and they undergo a considerable series of transforma- tions before arriving at their final form. In their earliest stage (Fig. 63, a) they are well known as tadpoles—little, fish-like creatures a = with broad heads, followed immediately by a jis a ee sac-like belly, and terminating posteriorly : Cae in a long compressed tail. The mouth is placed at the lower part of the front of ° the head, and is furnished with a pair of LS horny jaws, with which the little creatures es - feed upon the animalcula which form its C, ; nourishment. Whilst still very young, the aY tadpole is furnished with external gills; these soon disappear in the young of the frog, but in the tadpoles of the newts they remain for some time, and acquire a con- siderable size (Fig. 7). As the tadpole in- creases in size, the tail acquires greater . breadth, and by degrees the limbs burst g ¢ forth. It is remarkable that in the frogs ae, i -iete een the Frog. the hinder legs are the first to make their me aivole in its firststage; b,withhindlege; #PPearance (Fig. 63, 6), whilst in the newts ial "SNORE Hoge wih te roma sf ine tadpoleef the fog the hind-legs gene. 3 a ? -. e- the tail ; ‘e, when completely developed. rally appear some little time before the others, and even after the fore-limbs have been developed the tail still continues to ve the principal organ of motion (¢); but when these are fully formed, the large tail gradually disappears, and even before it has quite gone the young frogs often quit the RESPIRATION IN THE BATRACHIA. 359 water (d), and the remainder of the useless appendage is got rid of after- wards (e). In the newts and the other tailed Batrachia, the process is very similar, except y : ap av ab 3 tat the tail is a, the arterial ball, giving Hoe three pala of braachial axtorien: ab; D4, 2 2 , giving rise to three pairs of branchial arteries, ab; 01, 2, 8, notcastoff. But ‘the three pairs of branchie ; ¢, arteries running to the head, formed from the ¥ first branchial vein ; c, vessel formed by the union of the two hinder branchial during thepro- —_veins, and uniting with that of the other side to form the aorta, av ;, ap, rudimen.- gress of these tary pulmonary artery; 1, 2,3, branches uniting the branchial arteries and veins. external changes, modifications of a not less important character are taking place in the t internal organs. The bran- chial apparatus at first exhibits, the arrangement shown in Figure 64, in which the circulation goes on exactly as in the fishes. Thus the blood, driven from the arterial bulb through the bran- chiz, is again collected in : the branchial veins, of . fps fh which ‘two pairs assist in Fig. 65. —the Vessels of the itn atten the commencement the-farmntion of th ee a ‘Of aerial respiration. The letters have the same meaning as in aorta of the body, whilst the preceding figure. ° ’ the other pair is. distri- buted in the head. The pulmonary arteries first make their appearance in a very rudimentary form, springing from the bran- | chial vessels; but as the lungs are developed, and the aerial respiration commences, they rapidly incréase in size, whilst the branchie contract in the same proportion. This ¢on- dition of the respiratory apparatus is shown in Fig. 65, which may also be considered to represent the state of these organs in’ the Batrachia with persistent branchie. In the strictly air-breathing species, however, the- change goes still further—the ” branches (1, 2, 8) uniting the branchial arteries ac- quire amuch greater development, and gra-' dually divert more and more ofthe blood from the branchie, which quickly’ disappear : é altopether (Fig.66); the anterior branchial: rie. at _The Vessels in the Perfect Animal. oO 360 THE FISH-LIKE BATRACHIA. arches then become converted into the arteries for the head and eyes, the second pair go to form the aorta, whilst the place of the third is taken by the preliminary arteries, by the agency of which the whole business of respiration is now carried on. The Batrachia are essentially inhabitants of the warmer countries of the earth ; they abound particularly in the tropical zones. Although they are by no means confined to the water, they are always found in damp places, as moisture appears to be absolutely necessary for their existence. The lary feed entirely upon animal- cula; but the mature animals derive their subsistence principally from insects and worms, in the capture of which they often display great agility. In temperate climates they pass the winter in a torpid state, buried in the mud of ponds and ditches, without food or air; but under other circumstances the access of air must certainly be necessary, and the accounts which have repeatedly been given of the occurrence of toads in the heart of a solid block of stone, must always be received with some little allowance for the surprise which would naturally be created by the sudden appearance of the creature in an unexpected situation, such as the inside of a tree, or of an apparently solid stone. It is well known that, under favourable circumstances of air and moisture, the Toads will live for months without food, so that if those two grand requisites be granted, we may account for the most surprising of these cases without much difficulty. Divisions.—The class Batrachia may be readily divided into five very distinct orders—namely, the Lepidota, with a fish-like scaly body, four simple limbs, and per- manent gills; the 4poda, with a vermiform body and no legs; the Amphipneusta, with naked skin, two or four legs, and permanent gills; the Urodela, breathing by lungs alone, and retaining the tail in the perfect state ; and the Anowra, in which the tail is wanting in the fully developed animal. Orprr I.—Lepripota. This order includes only three singular animals, which have been placed by different observers alternately amongst the Fishes and the Batrachia; and it must be confessed that the claims of the two groups are so nearly balanced that it depends entirely upon the stress that may be laid upon different characters, under which class it shall be placed. The body is completely fish-like in its form, covered with rounded scales, laid over one another exactly like fish scales ; and immediately behind the head there is a small branchial aperture, The limbs are simple styliform organs, the anterior pair, like the pectoral fins of a fish, being attached to the back of the head, and the fin that runs round the posterior extremity of the body is supported by a series of horny rays. The scales with which the body is covered are of a peculiar structure; they appear to be composed of numerous small mosaic-like pieces. The skeleton consists of a continuous chorda, with bony arches, and the skull is cartilaginous, with a few bony plates. The teeth are in the form of perpendicular cutting plates. The branchie are attached to three complete arches, between which there is a similar number of slits opening into the pharynx, and there are also two other arches which bear no branchial lamin. The nasal cavities open into the mouth, and an opening into the pharynx leads to a pair of cellular lungs, which receive venous blood from the heart, and return it, when arterialized, into the aorta. These characters appear to prove that the animals of this order belong rather to the Batrachia than to the Fishes, especially as the auricle of THE LEPIDOSIREN—THE CCGCILIA. 361 the heart is distinctly separated into two chambers, although the partition between them is imperfect. Another important cha- racter is that one species, at least, possesses external branchie in the perfect state, a structure which does not occur in any Fish. Three species of this curious order are already known; they are found in the fresh waters of the hot regions of South America and Africa. The South American species (Lepidosiren paradoxa, Fig. 67) is between two and three feet in length; and another species (the LZ. annectens), of about a, foot long, is found in the Gambia. During the dry season these creatures bury themselves = in the mud; and one of them is said to make Fig. 67.—Lepidosiren paradoxa. itself a sort of nest in which to pass the period of torpidity. In these burrows they await the return of the wet season, which recalls them to thcir aquatic life. The Gambian species is said to pass nine months of the year in this torpid state. ' OrveR II.—Avopa. The animals belonging to this order also present such anomalous characters, that naturalists have long been doubtful whether they should be placed amongst the Batra- chia, or with the Snakes amongst the Reptiles. In the form of the body they closely resemble large earthworms ; they are totally destitute of limbs, and covered with a soft, viscous skin, which is annulated and wrinkled, and contains numerous minute horny scales, exactly resembling those of Fishes. The mouth is of moderate size; the eyes very small, and sometimes entirely wanting; and the anus is situated at the hinder extremity of the body, without the least indication of a tail. For many years great difficulty was experienced in assigning a place to these curious creatures, as it was not known whether they passed through any metamorphosis; and they were accordingly arranged by Cuvier, and many other zoologists, amongst the Serpents. It is found, however, that in the young state there is an aperture in the side of the neck, which leads down to a system of branchie. The Apodal Batrachia form a single family, the Ceciliide, so called in consequence of the minute size and occasional absence of the eyes. They live in the tropical regions of both hemispheres, where they burrow in marshy ground, like earthworms, in pursuit of the larve of insects, upon which they feed. The species generally mea- sure from one to two feet inlength ; but Cuvier states that he possessed the skeleton of a Cecilia which was more than six feet in length, and contained two hundred and twenty-five vertebrae. Orver II].—Ampuipnevsta. General Characters.—This and the following order agree in having the skin perfectly naked, the body elongated and produced behind into a permanent tail, and the limbs more or less developed. The Amphipneusta are distinguished principally by the permanent nature of the branchial organs (Fig. 68), which project from the sides of the neck during the whole life of the animal. The lungs, although existing, are in a comparatively rudimentary 362 . THE PROTEIDA—THY SIRENIDE. state, and there can be no doubt that the respiration of these animals is essentialiy aquatic. The eyes arc always small, sometimes completely concealed beneath the skin, but never furnished with eyelids; the legs aro small and weak, sometimes only two in number, and terminated by rudimentary toes. Divisions.—These singular animals, which are generally of small size, are divi- sible into two families, the Proteid@ and the Sirenide. The former have a compressed tail, large branchiw, and four legs. Of these the best known is the Proteus, or Hypochthon anguinus, an extraordinary creature which is only found in the subterranean waters of some caves in the south of Europe (Carinthia and some other parts of the Austrian dominions). It is about a foot long, and sometimes nearly three quarters of an inch in diameter. Itis of a pale flesh colour, or perfectly white, with the exception of the three pairs of branchial tufts, which are of a fine bright crimson; the body is cylin- drical, and a good deal longer than the tail, which is broad, and much compressed. The legs are very weak, and the anterior pair terminate in three toes, the posterior in two. Although apparently a weak and sluggish animal the Proteus swims with considerable ease, with a leech-like undulation of the body, and like the Lepidosiren, it is said to bury itself in the mud at the bottom of its place of abode when the water happens to dry up. Several species of this group arc found in different parts of America; of these, one of the most remarkable is the Axolotl (Siredon pisciforme, Fig. 68), which inhabits the lake surrounding the city of Mcxico, where it attains a length of ten or fifteen inches, and is esteemed a great luxury. At the time of the invasion of Mexico by Cortez, it was so plentiful in the lake that he is said to have fed his army upon it for some time; and. Mr. Bullock, in his account of his residence in Mexico, states he saw it in thousands exposcd for sale in one of the markets. The Axolotl is of a brown or grayish colour, spotted with black; the fore feet have four and the hind ones five toes; on each side of the neck there is a very large aperture, within which are branchial arches; but the projecting branched gills are attached to the opercula, or flaps, which close these orifices. The largest specics appear to belong to the genus Menobranchus, of which one, the Af. Jateralis, which is found in the great North American lakes, attains a length of from two to three fect. “ The Sirenide have only the two anterior legs ; the body is elongated, and somewhat cylindrical, and the branchial tufts small. They have no operculum. The best known species is the Siren lacertina, which inhabits the marshy rice- grounds of Carolina. It is of an eel-like form, and occasionally measures as much as three feet in length. The feet are small, and furnished with four toes, and the tail is compressed so as to form a sort of blunt fin. The Siren lacertina generally keeps in the mud and muddy water of the rice swamps, but is said occasionally to come upon land; it feeds upon worms and insects. Its original discoverer, Dr. Garden, who furnished Linneus with specimens, accompanied them with some wonderful stories relating to its supposed habits. - He stated that the Siren fed habitually on serpents, and that it had a sort of singing voice. From the latter circumstance Linnaus gave the name of Siren to the genus. Dr. Garden’s statements have, however, been denied Fig. 68.—Axolotl (Siredon pisciforme). THE NEWTS. 363 by subsequent observers. Several smaller species are also found in different parts of the United States. Onvrer IV.—UrRopz3a. Genezal Characters.—The Urodela, in the general form of the body, frequently: present a close resemblance to the Lizards, with which they were arranged by Linnzus and the older naturalists. They have a persistent tail, four limbs, which are sometimes very small, and occasionally the toes are furnished swith claws. There are no external branchize, and the lungs are well developed; but in a few species there is. a branchial aperture on each side of the neck, within which are the branchial arches, with their laminew. The skin is cither quite smooth or covered with warty prominences ; it is usually furnished with numerous glands, which secrete an acrid, viscid fiuid, and this has no doubt obtained for these animals the reputation for venom which many of them enjoy. ig Divisions.—The Urodela form two great families. ‘In the Amphiumide the limbs are of very small size; the neck has usually a branchial aperture on each side; and the eyes are minute and destitute of eyelids. These animals are generally of large size, the Amphiuma tridactylum attaining a length of three fect. Like the Sirenid, which they a good deal resemble in form, they are particularly partial to the mud of shallow waters. Most of them inhabit the United States of America. The Salamandride, the only family of tailed Batrachia of which examples occur in our own country, is distinguished from the preceding family by the total absence of all | traces of a branchial apparatus after the animals have attained their mature form, and also by the structure of the eyes, which are very prominent, and protected by eyelids. This family is divisible into two very distinct groups or sub-families—namely, the Tritons,.or Aquatic. Salamanders, in which: the tail is much compressed, and which frequently visit the water ; their reproduction is oviparous, their eggs producing tadpole- | like larvee (Fig. 7), which gradually acquire the form of their parents, after swimming | about for some time in the water, respiring by means of gills;—and the Salamandra, ox Land Salemanders, which have a cylindrical tail, and live on land in damp places, | producing their young alive. . (These divisions into terrestrial and aquatic species must not, however, be received in the strictest sense, as it appears, from the observations of Mr. Higginbottom upon our British Tritons, that,these little animals really pass a great part of their time on land, and only visit the water during the. breeding season. Mr. Higginbottom also states that the Tritons do not breed until they are fully three years old, and that the interval. between their quitting the tadpole state, and retiring to the water for the purpose of breeding, is entirely spent on the ground. During this period, the young Tritons conceal themselves for the winter in solitary holes, often at a considerable depth in the ground; but the full-grown ones frequently collect together into a mass as ahd as a onbksttell and thus hybernate in company. At the approach of the .. breeding-season, which commences in March or April, the Tritons begin to acquire peculiar appendages, con- sisting principally of a fin-like crest running along the back and- tail . Figs 69, triton, 8 branous appendages to the toes. ee When in a the water they are exceedingly, voracious, devouring almost, all small aquatic (Fig. 69), and some similar mem- | 364 THE NEWTS AND SALAMANDERS. animals, and not even sparing the Tadpoles of their own species. These are generally excluded about the month of June or July; and in the course of July or August the old Tritons quit the water, and again betake themselves to a terrestrial existence, whilst the Tadpoles, according to Mr. Higginbottom, remain for the most part without much change until the following spring, when they acquire legs, and are enabled to quit the water. The species of Triton are very difficult to distinguish, as it appears that the cha- racters of the same species vary greatly in accordance with sex and age—the crests and other appendages which make their appearance during the breeding season, having been particularly fertile sources of confusion. It appears, however, that we possess at least two distinct species, of which the larger, Triton palustris, measures, when full- grown, about six inches in length ; whilst the smaller and commoner one, T. aguaticus, is only a little more than halfthat length. Both these specics may be found commonly in ponds and ditches during the spring and summer months; the former is of a very dark brown above, with the sides mottled with white, and bright orange beneath, spotted with black. The colours of the smaller species are somewhat similar to those of the preceding, but are generally paler. Their tenacity of life is most wonderful ; they may be mutilated in various ways, and will reproduce the lost members, as proved by the experiments of Bonnet and Spallanzani. According to the testimony of other observers, moreover, they may be frozen hard in the centre of a lump of ice, and recover their former activity as soon as they are thawed, even although they may ne been in this close prison for some time. When depositing their ova they- inclose them very carefully in the leaves of aquatic plants, apparently in order to prevent the too free access of the water, which would cause the young to be developed too rapidly, and no doubt lead to their destruction. The terrestrial species, or True Salamanders, have a rounded tail; and the young, instead of being developed in the water, are retained within an enlarged part of the oviduct, where they pass through the first part of their metamorphoses in an albuminous fluid. The Salamanders have a large gland behind the ear, which secretes a yellow matter ; and small glands of a similar nature are scattered through the skin. The matter thus secreted is so abundant, that it was long a vulgar superstition that the Salamander, if put upona fire, immediately discharged a quantity of water, sufficient to put the fire out; and many of these unfortunate Amphibia have no doubt been sacrificed in consequence of this belief. The Salamanders are generally of small size; none are found in this country, but several occur on the continent. They rarely exceed six inches in length. OrpEer Y.—ANURA. General Characters.—The general form of the animals included in this order, of which the well-known Frog may be taken as the type, is shorter and broader than that of any of the preceding groups, and the tail is entirely wanting. The head is broad, and the opening of the mouth very large. The limbs are of unequal length, the hinder pair being usually much longer than the anterior, supplied with powerful muscles, and fitted to enable the animals to perform considerable springs. The skin is quite naked, smooth, and extremely dilatable; in many cases it is furnished with a great number of glands, which secrete an acrid liquid. THE FROGS AND TOADS. 865 The organs of the senses always exhibit a much greater degree of perfection than in the preceding groups ; the eyes are almost always of very large size, prominent, but retractile, and furnished with a pair of eyelids, of which the lower one is large enough to.cover nearly the whole of the eye. The external ear is situated immediately behind the eye, and the internal portions of the auditory organ present a much greater perfection of organization than in any of the preceding vertebrata. The upper jaw is usually armed with small, hooked teeth, and similar teeth are occasionally distributed! in the lower jaw and palatine bone. The tongue is some- times wanting, but is generally of large size, filling up nearly the whole space between the two sides of the lower jaw. It is usually fixed to the front of the mouth, so that its hinder part is quite free, and can be pushed out of the mouth to a consider- able extent, and employed in the capture of prey. The fore legs are usually terminated by four free toes, which are of nearly equal length ; the hind legs generally have five toes, more or less united by a membrane, and of unequal length, the innermost being by far the shortest, and the fourth usually the longest. The spinal column of the Anura is very short, consisting, as a general rule, only of eight vertebre ; itis terminated posteriorly by a long slender bone, which runs down the middle of the elongated opening of the pelvis; the latter is composed of two very long parallel bones, which lie in the same direction as the axis of the spine. The thighs are articulated at the extremity of this pelvis. The habits of these animals are very various. Many of them live habitually in the water, whilst others only visit that element for the purpose of depositing their ova, which give origin to tailed Tadpoles, the development of which has already been described (page 86). Of the species which only visit the water occasionally in this manner, some live constantly on the ground in moist places, or hide themselves under stones, and come out in search of food generally in the evening, whilst others pursue their insect prey upon the trees and bushes, the ex- tremities of their toes being furnished with ad- hesive organs, which enable them to climb about with great ease and security. Divisions.—This or- der, including the well- known Frogs and Toads, is divisible into three dis- tinct ‘and well-marked families, Of these, the — aa pe tere ee Fig. 70.—Surinam Toad (Pipa Americana). tongue ; the tympanum of the ear is concealed, the head is triangular, and the small eyes are placed low down towards the mouth. The body is broad and thick, and the hind legs exceedingly large and powerful, the toes being completely united by an ample membrane. In the typical genus Pipa the teeth are wanting, whilst in Dactylethra, which is 366 THE TOADS. also distinguished by having hoof-like claws on some of the toes of the hind feet, the upper jaw is armed with small pointed teeth. The Pipa americana, or Surinam Toad (Fig. 70), belonging to this family has long been known as affording an example of a most remarkable and anomalous mode of reproduction. At the breeding season the back of the female exhibits a number of singular pits, each of which receives an egg, and the young animal, which, as usual, makes its first appearance in the form of a tadpole, undergoes its changes ‘in this confined space, and emerges at once a perfect Toad. These facts have been known for many years, and for a long time it was supposed that the eggs (which are completely inclosed in the dorsal cells) were produced immediately in the place where they were | found without going through the protess usual amongst the other Anura. It has been found, however, that the Pipa does not differ from its fellows in this respect ; but the mode in which the ova reach their destination certainly affords a curious example of instinct. The female deposits her eggs at the margin of the water, but the male, instead of merely impregnating them, and lcaving them to their fate, takes the trouble to collect the whole mass of eggs and deposit them upon the back of his partner, where they are pressed into the open cells, which are afterwards closed with a sort of lid. The development of the embryo then takes place in these cells in exactly the same way as with the free larvee of the other Batrachia. The Surinam Toad is commonly found in the dark corners of houses in Guiana and Surinam; it is, perhaps, one of the ugliest of the Toads; but notwithstanding its disgusting appearance it is eaten by the natives. The Bufonide, or Toads, are always provided with a well-developed tongue, a character which serves to distinguish them at once from the preceding family. The body in these animals is thick and heavy, and the skin usually covered with glandular warts, from which an acrid juice exudes. The hind legs are but little longer than the others, and the animals are consequently unable to perform those great springs which are characteristic of the following family. But the most important distinction between these animals and tho Frogs consists in the absence of the teeth in the Toads, the jaws being rather sharp at the edge, but quite unarmed. The Toads are generally regarded with but little favour; and there is certainly not -much in their appearance to recommend them. They generally come abroad in search of food in the dusk of the evening, when they may often be seen in gardens, woods, and Janes. : The Toads generally live out of the water, but visit that element during the breeding season, which is in March or April; during winter they lie in a torpid state, concealed in holes or under stones. They produce an immense number of eggs, which, instead of being inclosed in a mass of gelatinous matter as in the Frogs, are united into long strings inclosed in a similar substance. Of these strings or necklaces of eggs thore are generally two, which the male draws out of the body of the female with his hind feet. ’ We have two species of Toads in this country—the common Toad (Bufo vulgaris, Fig. 71), and the Natter-jack (B. calamita). Several other species are found on the continent of Europe, amongst which the most remarkable in its habits is perhaps the species called the Accoucheur Toad (B. obstetricans), of which the male not only assists the female in the exclusion of the eggs, but attaches them afterwards to his own hind | legs, where the young are developed until they arrive at the tadpole state, when the umale visits the water, and the young animals escape. This species is very common in the vicinity of Paris, © : e * THE TOADS. 367 Our common Toad feeds upon insects and worms of every kind; but it will not eat anything that is not living. When about to feed, it remains motionless, with its eyes fixed intently upon its intended prey, and remains in this position until the insect moves, when the tongue is instantly darted out of the mouth with the rapidity of lightning, and the victim rarely escapes being drawn back with it into the mouth. Mr. Bell states that when the prey is taken it is slightly pressed by the margins of the jaws; but as this seldom kills it, unless it be a soft tender larva, it is generally swallowed alive; and he adds that he has often seen the muscles of the Toad’s sides twitching in a most singular manner from the tickling movements of a beetle that had been introduced alive into the stomach. There are probably few harmless animals that have suffered more from a false charge of venom than the Toad. Whether it be Fig. 71.—Toad (Bufo vulgaris). from the ugliness of the creature, or from some other cause, the Toad appears to be regarded as venomous by the popular mind of almost all countries, and the poison is said sometimes to reside in the saliva, sometimes in the bite, and sometimes in the liquid cxuded from the skin. The last- mentioned matter appears really to be sufficiently acrid to produce painful effects if applied to a very tender or wounded surface ; and it is said that dogs which have carried a Toad in their mouths fora distance, have been observed to be atfected with a slight swelling of the lips, which, however, soon goes off, without any danzerous conse- quences. I¢ is well known that the Toad can live for along time without food, and even with a very small supply of air; but the instances commonly related of these creatures being found imbedded in solid stone, or in the heart of the trunk of a tree, with no possible communication with the external world, must be regarded as arising from errors of observation. This is, however, a very curious subject; and much probably remains to be ascertained before we can satisfactorily account for the facts which have given rise to the common opinion. There can be no doubt, in fact, that Toads have been found in situations which rendered their obtaining food apparently an impossi- bility, whilst their supplies of air and moisture must have been very small; but we are not, therefore, prepared to admit, with some writers, that the animals were really inclosed hermetically in their prison. With Mr. Bell, we may say, “to believe that a Toad, inclosed within a mass of clay, or other similar substance, shall exist wholly without air or food, for hundreds of years, and-at length be liberated alive, and capable of crawling, on the breaking up of the matrix, now become a solid rock, is certainly a demand upon our credulity which few would be ready to answer.” The Ranide, or Frogs, of which the Common Frog (Rana temporaria, Fig. 7?) is a well-known example, have the body of a lighter and more elegant form than the Toads, and the hind legs are much longer, exceedingly muscular, and fitted for the performance of considerable leaps. The upper jaw is always armed with teeth; the skin is usually smooth, but in some cases is covered, as in the Toads, with glandular warts. In the structure of the tongue they resemble the Toads. | | | | e 368 THE FROGS. The Frogs, undoubtedly, form the highest group of the Batrachian class. They are active creatures, living on insects and worms, which may be divided into two sub- families, in accordance with important differences in their structure and mode of life. . The Ranides, or Frogs, which live upon the ground in the neighbourhood of standing water, and pass a considerable portion of their lives in the water, have their toes pointed, and those of the hinder feet united, almost to the tips, by a membrane. The Common Frog is a very abundant F and well known ani- mal. It is constantly to be found hopping about in the neighbourhood of water, especially in damp evenings. It generally deposits its eggs in the water in the month of March; they are enveloped in a mass of gelatinous matter, within which the eggs are seen gradually to increase in size for a month or five weeks, at the end of which time the young tadpoles may be seen moving. When ready to enter upon their aquatic existence, they eat their way through the surrounding jelly, and thus escape. In the course of six or eight weeks the four legs are fully formed; the tail then gradually disappears, and the young Frog usually quits the water imme- diately. In this way they often suddenly make their appearance in prodigious numbers in particular spots, giving rise to the popular superstition of “‘ Frog rains ;” and in some cases it is said that the little creatures have been taken up and carried to a distance by high winds, to the great astonishment of the inhabitants of the districts in which they again descended. The Common Frog is said to be five years in attaining its full size, and its life is supposed to extend to twelve or fifteen years. Itpasses the winter in a state of tor- pidity, either in holes in the earth, or buried in the mud at the bottom of ponds, without the possibility of feeding or breathing. The voice of the Frog is a peculiar hoarse cry, well known as croaking. In the males, there is a large sac on each side of the neck, which is inflated with air during the croaking, and probably serves to increase the sound. The species of Frogs are very numerous, and distributed very generally over the globe; they are especially abundant in tropical countries. Their habits are generally very similar to those of the Common Frog. Of the European species, the most célebrated is the Edible Frog (2. esculenta), which is exceedingly common in standing water on the continent, although in England it appears to be rare. It is rather larger than the Common Frog; and its nocturnal croakings are said to be so exceedingly loud and disagreeable, that temporary dwellers in the neighbourhood of ponds frequented by it are often prevented from sleeping by its clamorous chorus. It is this species that is most approved of on the continent for culinary purposes. Fig. 12.—Frog (Rana temporaria). BULL-FROGS—TREE-FROGS. 369 Of the exotic species, one of the largest is the Bull-frog (Rana pipiens), which inhabits North America, and has received its name from the fact that its croak resembles the distant lowing of a bull. The body of this species measures sometimes as much as eight inches in length, without including the hind legs, which are large, and have the toes broadly webbed. This frog is said to confine itself exclusively to the small pools formed at the issue of springs, each of which, according to some observers, is taken possession of by a pair of Bull-frogs. The inhabitants believe that the frogs keep the water clean; consequently leave them without molestation, although they are often destructive to young ducks and goslings, which they swallow whole. One of the most remarkable species is the Jakie (Rana paradoxa) of Guiana, in which the tadpole is of such large size, and possesses such an enormously developed tail, that the earlier observers described it as a frog which became converted into a fish. The Hylides, or Tree-frogs, are distinguished from the preceding animals by their having the extremities of the toes dilated into small knobs (Fig. 6), which usually produce a sticky secretion, of the greatest service to the animal in its active arborea life. These animals are usually of a more elegant form and of brighter colours than the other Frogs, and they are particularly active during the day, thus in many respects presenting a great approach to the Lizards. The Tree-frogs are active little creatures, pursuing their insect prey upon the trees and bushes ; sometimes stealing cautiously towards their victims, and sometimes spring- ing upon them with a sudden leap. In all these evolutions it is greatly assisted by the sticky palette-like terminations of its toes, and also by some glandular organs imbedded in the skin of the abdomen, which secrete a viscous fluid. The Tree-frogs have a very loud croak, and are observed to be particularly clamorous at the approach of rain. During the winter they bury themselves, like the other Frogs, in the mud at the bottom of pools. They breed in the spring, depositing their spawn in the water. A curious property is attributed by Linneus and the older writers to an American species of this group, the Hyla tinctoria. It was said that the natives of South America were in the habit of pulling out the feathers from young green parrots, and rubbing the blood of this frog upon the bare place; when it was believed that the feathers produced upon these spots would be of a yellow or red colour. A singular species of this sub-family has recently been described by Dr. Weinland, of Berlin, under the name of Notodelphys ovifera. In this animal the back of the female is furnished with a large double sac under the skin, in which the eggs are retained, and the embryo developed as far.as the production of the feet; the further progress of the young is not known. This species is from Venezuela. Cuass III.—Reprizia orn Reprices. General Characters.—The true Reptiles, a group of animals generally regarded with but little favour by mankind, constitute the first class of the higher vertebrata, or of those {in which a mechanism for aquatic respiration is never found. They differ from the Batrachia, which are very commonly included in the class of Reptiles, and with which they agree in the coldness of their blood, and, to a certain extent, in the character of their circulatory apparatus, not only in the important physiological point above mentioned, but also in several particulars of their anatomical structure, and especially in, the mode of development of the embryo, in whick they closely resemble the Birds. 370 SKELETON OF REPTILES. The Reptiles in general, almost with the sole exception of the Tortoises, are of an elongated form, often nearly cylindrical, and they usually terminate posteriorly in a very long tail. The feet are very variably developed, but.rarely suffice to support the animal in the manner of an ordinary quadruped ; the belly, as a general rule, trailing along the ground when the animal is in motion. In a considerable number no traces of the limbs are to be found, and when they first make their appearance it is in such a rudimentary form that they can be of little or no use to their owner. In all these animals the ossification of the skeleton is very complete, and in none of them does it present the cartilaginous state of that of many l'ishes and some Batrachia. The true skull is always of comparatively small size, and the great bulk of the head is made of the bones of the jaws. The occipital bone always exhibits the vertebral form with great distinctness; it is furnished with a single articulating process, which, however, is sometimes divided into two parts by a narrow furrow: this, fits into the cavity of the first cervical vertebra. . The floor of the cranium is formed by the sphenoid bone, and its upper surface principally by the parictals, which are usually amalgamated so as to form a single bony plate. The front of the cranial cavity is closed by the frontal bones, which are also frequently coalescent, and by the nasal bones. The bones of the upper jaw and palate are always greatly developed; in some instances they are firmly fixed to the cranial bones, whilst in others they are moveable, and only attached to the skull by articulations. The lower jaw is of very complex structure, each half being composed of a variable number of picces ; in the Snakes, this number is four or five; whilst in the Lizards and Crocodiles each branch of the jaw consists of no less than six pieces. In the Snakes, the two branches of the lower jaw are united only by ligaments and muscles, so that they are capable of being sepa- rated to a considerable distance at the pleasure of the animal; but in the Lizards and Crocodiles the union is much closer, the bones being united by fibro-cartilage in the one case, and in the other by asuture; whilst in the Tortoises, the whole of the lower jaw is amalgamated into a single piece, The mode of articulation of the lower jaw varies greatly in the different orders, and will be referred to in the proper places. The mouth in almost all Reptiles is armed with sharp hooked teeth, which are sometimes placed only on the jaws, but in some instances are distributed over the palatine bones and vomer. ‘Chey are generally inserted into a furrow of the bone, to which they are attached only by flesh and sinews ; but in the Crocodiles they are sunk separately into regular sockets in the jaws. Inthe Tortoises, again, no teeth exist, the edges of the jaws being simply armed with a horny covering, bearing no distant resemblance to the beak of a bird. The vertebral column is rather variable in its structure. In a very few instances the bodies of the vertebrae exhibit a conical cavity at each end, like that existing in the vertebre of Fishes; but in most cases one of the end-surfaces is more or less convex, and fits into a corresponding cavity in the body of the next vertebra. This structure is most developed in the Snakes, in which the bodies of the vertebra articu- late by a regular ball-and-socket joint. In the Tortoises, the two extremities of the yertebre are ‘flat, and united by a dise of fibro-cartilage. A striking osteological distinction between these animals and the Batrachia, consists in the constant presence of ribs in the'former, these appendages to the vertebral column being always wanting in the latter class. 2 In the Reptiles the ribs generally extend backwards to the pelvis; they are always LIMBS AND SKIN OF REPTILES. 371 well developed, and, in most cases, a greater or less proportion of them are attached to a well-developed sternum or breast-bone, which, in the Crocodiles, also runs back to the pelvis. In the Snakes the ribs are perfectly free at the extremity, and, from their great mobility, are important aids in the movements of these footless creatures ; whilst in the Tortoises, on the contrary, these boncs are immoveably fixed, and constitute a great portion of the bony case in which those animals are inclosed. The neck is generally short, and the cervical vertebrae are sometimes furnished with ribs; in the Tortoises, however, this portion of the vertebral column is of considerable length, and possesses great flexibility. The caudal portion is usually very long, and tapers gradually to a point ; in many cases it more than equals the rest of the body in length. In the development of the extremities these animals exhibit as great a diversity as the Batrachia. In tho greater part of the Lizards and in the Crocodiles all the limbs are well developed. The feet are formed of freely moveable toes, which are usually terminated by strong claws; and the bony arches supporting these members are always of considerable size and firmness, so that the animal walks with facility, and is often able.to perform considerable leaps. In some members of the group of Lizards, however, the extremities gradually diminish in size, still retaining their perfect form, but aiding little or nothing in the movements of the creature; in others the anterior pair disappear, and the posterior take the form of large scale-like organs, in which there is no external indication of any complexity of structure, although, except in the want of toes, the bones contained in them are identical with those of the more perfectly formed Reptiles; whilst in others, again, even these rudimentary limbs are absent. The latter structure prevails throughout the great group of Snakes, in which the only trace of the existence of the limbs consists in a pair of small bones suspended in the muscles near the vent in some species, which must be regarded as the analogues of the pelvic bones, the presence of which is sometimes indicated externally by a pair of horny spines projecting on each side of the anal opening. Of the perfectly developed feet several modifications occur. In general, the whole of the toes, which are usually five in number, are extended forwards from the extremity of the leg; but in the Chameleons the toes are divided into two sets, one including two, the other three toes, forming a sort of grasping hand, which must be of the greatest service to these creatures in their arboreal residence. In the Crocodiles and some Tortoises the toes are distinctly recog- nizable externally, but united to a greater or less extent by membranes, in order to adapt these creatures for their aquatic habitation; and in other Tortoises the toes are completely concealed by a fleshy mass, which in the Land Tortoises is of a thickened and more or less cylindrical form, adapted for terrestrial progression, whilst in the Turtles it is much compressed and modified so as to form a broad and powerful fin-like organ. In the clothing of the skin we find almost an equal diversity. In a small group of Lizards the skin is covered with free scales, lying over one another like’ tilcs, in the same way as those of Fishes, and inclosed like these in peculiar dermal sacs ; but in the majority the scaly covering has a very different arrangement. The scales are generally appendages of the true skin or corium, and are covered by the epidermis, a delicate horny pellicle, which is cast off periodically. In the Crocodiles and Tortoises they become converted into bony plates, which in the former are immersed in the corium, whilst in the latter they become united with the bones of the internal skeleton to form the well-known bony cases which serve as such an admirable protection for those sluggish creatures. In these also the epidermis becomes permanent, and formg thick, horny plates of regular forms, covering the bony skeleton. 372 ANATOMY OF REPTILES. With the exception of a few Tortoises, all Reptiles are carnivorous animals, feeding entirely upon living prey. Their teeth, however, are never constructed for the division of the flesh of their victims, and they are consequently compelled to swallow them whole. For this purpose the cesophagus is usually very wide, and capable of great dilatation, many of the Snakes actually being capable of swallowing animals of con- siderably greater bulk than themselves. The tongue is sometimes closely attached to the bottom of the mouth; but in most Reptiles it is free, elongated, and bifid, terminating, Fig, 73.—Anatomy of a Snake (Coluber natriz). 7, tongue and glottis; @, msophagus, divided at a to show the heart, &ce.; i, stomach; 7, intestine; cl, cloaca; an, anus; f, liver; 0, ovary; o', eggs; t, trachea; p, principal lung; p’, undeveloped lung; vt, ventricle; c, left auricle; ¢’, right auricle; ag, left aortic arch ; ad, right aortic arch; a’ a’, ventral aorta; ac, carotid arteries 3 v, Vena cava superior; ve, vena cava inferior. 3 in many, in a pair of nearly horny filaments, which are inclosed in a sheath, and can be protruded and retracted at the pleasure of the animal. The intestine is usually of great width, ‘but comparatively short; it terminates in a wide cloaca, into which the ducts CIRCULATION IN REPTILES. 373 of the urinary and generative organs also generally open. The liver, pancreas, and spleen, are always present. The anus opens in two very different directions in the Reptiles, and this character has been employed to divide the class into two great sections. In the Snakes and Lizards, the anal aperture is transverse, and usually closed by a sort of valve (sec Fig. 75); whilst in the Crocodiles and Tortoises it opens in a longitudinal direction. These peculiarities in the anal aperture are accompanied by remarkable differences in the external generative organs of the male. In the former section there are two of these organs, which are contained in a cavity of the base of the tail behind the anus, whilst in the second the male organ is single, and lies within the cloaca. In the Lizards there is generally a transverse series of glandular organs placed immediately in front of the anal valve; and these are frequently continued upon the under side of the thighs. These glands open by a corresponding number of pores; and the presence or absence, and number, of these, especially of the femoral pores, often furnish valuable characters for the distinction of genera and species. In the organs of circulation and respiration, the Reptiles exhibit a marked advance upon the Batrachia, although these organs are still far from exhibiting the same degree of perfection that they attain in the Birds and Mammalia. The heart consists essen- tially of four chambers, although in by far the majority of these animals the partition between the two ventricles is imperfect, so that, for all practical purposes, we may regard the ventricle as single. The consequence of this arrangement is, that the blood returning to the lungs, after exposure to the influence of the air, mingles with that brought back from the general system, and this mixed fluid is driven at once from the ventricle into the pulmonary as well as into the systemic arteries, so that only a portion of the venous blood passes through the lungs before being retuwmed into the general circulation. In the Crocodiles, the partition between the two ventricles is complete; but in these, as well as in other Reptiles, « communication between the great pul- monary and systemic arteries is effected by the agency of the remains of the branchial arches of the embryo (Fig. 74). The aorta forms one, two, or three arches (Fig. 75), from the foremost of which the carotid arteries are sometimes Fig. 74.—Heart and large vessels of the Crocodile. v, Vena cava, conveying venous blood from the sys- tem to the rightauricle, od ; given off. The aorte afterwards unite in the middle of the body below the spinal column, forming a single great trunk, which runs down the body, and is called the abdominal aorta. The blood returning to the heart is collected in the vene cave, of which the inferior forms a great trunk running up the body, and gives off a portal system of veins to the liver and kidneys (Fig. 75). The lymphatic system attains an extraordinary degree of development in this class, and possesses some regularly pulsating organs, or lymphatic hearts, which serve for the propulsion of the peculiar fluid contained in these vessels. vt, the ventricles, separated by an internal partition; ap, pulmonary arteries con- veying venous blood from the right ventricle to the lungs ; vp, pulmonary veins, running to the left auricle, og; ao, aorta rising from left ventricle, and conveying blood to the system ; a, trunk rising from right ventricle, and carrying venous blood to the descending aorta; c, carotid arteries running to the head. The respiration of these animals being always aerial, their respiratory organs, of course, take the form of /ungs, and these are often of extraordinary size, in some 374 RESPIRATION AND SENSES IN REPTILES. instances extending through the whole length of the ventral cavity, which is not Fig. 75.—Cireulation in a Lizard. a, arches of aorta; }, left auricle; ¢, right auricle ; d, ventricle; e, carotid artery ; f, superior voma cava ; g, abdominal aorta; h, pulmonary vein; 4%, brachial artery ; j, pulmonary artery; /, inferior vena cava; 1, lungs; m, liver and vena porte ; ”, stomach; 0, kid- neys; p, vena porte; 7, intestines; s, artery of gene- rative organs; ¢, anus. : divided bya diaphragm or transverse partition. In the more elongated forms, such as the Snakes and some Lizards, only one active lung is present, the other being reduced to arudimentary condition or altogether wanting. Bs The processes of respiration and ‘circulation go on with far less activity in these animals than in the Birds and Mammalia, and their blood, like that of the lower Ver- tebrata, is cold, that is to say, its temperature is but little higher than that of the surrounding medium. The performance of all their func- tions partakes of this inactivity; their digestion goes on very slowly ; and although they are capable of violent muscular exertion, and are often very agile in their movements, their general habits are sluggish. In the general arrangement of the nervous system the Reptiles present a considerable resemblance to the Batrachia; but the brain, and especially the cerebral hemis- pheres, attain a much greater deve- lopment in the higher species of the class. The cerebellum also exhibits a gradual development from the lowest to the highest forms. The organs of the senses are generally possessed in a state of con- siderable perfection. The nasal cavities are of large size, and always. open into the mouth; in the Cro- codiles, this opening is placed very far back, and the palate is fur- nished with a velum, by which the aperture can be closed; the nostrils in these animals are also provided with valvular organs, which prevent the ingress of water. The eyes are usually sinall, sometimes, though rarely, concealed under the skin, generally furnished with eyelids. These pro- tections to the visual organs are wanting in tke Snakes, which have the front of REPRODUCTION OF THE REPTILES. 375 . the moveable eye-ball covered with a transparent capsule, which is inserted under a fold of skin, like the glass of a watch in its frame. Between this capsule and the eye | there is a space which is filled by the secretion of the lachrymal glends; the excess of this passes off through a duct into the nasal cavity. The cyes of most other Reptiles | are furnished with a pair of eyelids, of which the upper one is usually very small and stiff, and the lower one alone is capable of being drawn up to cover the eye, which it | does completely. In some cases this lower cyelid has a transparent space in the part | corresponding with the pupil; in others, it is furnished with a peculiar bony plate. The most remarkable structure in this respect is presented by the Chameleons, which have large, prominent, globular eyes, capable of very great and independent motion, but completely covered by a circular lid, in which there is only a small central hole corresponding with the pupil. All the Reptiles with eyelids also possess a nictitating membrane, which can often be drawn completely over the eye. The structure of the auditory organs is almost as complex as in any of the higher Vertebrata, but some of their component parts are often in a low state of development. The tympanum is sometimes exposed, sometimes covered by a fold of skin, or completely concealed under the skin ; in the Crocodiles, there is a moveable valve, by which the tympanum can be concealed at pleasure. All the Reptiles are truly oviparous animals, and by far the majority come under this denomination in its strictest sense ; but the ova are generally retained within the | body of the parent until: the development of the embryo has proceeded a certain dis- tance, and in a few cases, until the complete development of the young animal, which then breaks out of the egg whilst this is still inclosed in the oviduct. The species in which this phenomenon oceurs are often called ovo-viviparous. The eggs of Reptiles are | generally of large comparative size, and are furnished with a very large yelk; they | are usually covered with a parchment-like shell, which occasionally contains a small portion cf caleareous matter. The truly oviparous Reptiles generally deposit their eggs in warm, sandy places, where they leave them to be hatched by the heat of the sun; but the common opinion that they take no further care of the progeny, although } correct in many instances, is certainly contradicted in others; for the Crocodiles and some Lizards are said to watch in the neighbourhood of the place where they have laid their eggs, so as to protect them from any threatened danger, and the gigantic Pythons have been seen, in the Tower and other menagerics, to coil themselves round their | mass of eggs in a conical form, closing the top with their heads. In the species which | bring forth living young, the connection between these and the parent appears to be still closer ; and, according to the testimony of some observers, the young of some of the poisonous snakes take refuge from impending danger by creeping down the throat of their mother. In the development of the embryo, the Reptiles differ from the Fishes and Batra- éhia, and approach the higher classes of Vertebrated animals, especially in the forma- tion of a peculiar membranous sac, the amnios, which completely envelopes the em- bryo; this structure does not occur in any of the lower Vertebrata. After the embryo has attained a considerable degree of development, a second membranous coat makes its appearance, of which we meet with no‘trace in the embryonic states of the lower yertebrata. This is the ad/antois, which forms a membranous sac, richly supplied with vessels, enveloping both the embryo and the amnios. The Reptiles are essentially inhabitants of the warmer regions of the earth. In our northern countries but few species exist, and these pass a great portion of the year in a 376 ORDERS OF REPTILES. state of torpidity, and only come abroad in the warm days of spring and summer ; but in tropical regions the number of these creatures is surprising; Snakes and Lizards are to be encountered at every turn, and Crocodiles often swarm in the rivers and tanks, The size attained by these creatures in hot climates is also enormous—the Boas and Pythons of tropical America and Asia, and the Crocodiles and Alligators of the warmer parts of both continents often acquire dimensions which render them formidable even to man himself, and the virulence of the poisonous snakes of hot countrics is so great, that their bite is frequently attended by fatal consequences. Divisions.—The characters already given (p. 101), serye to divide the Reptiles into two great sections, each of which contains two orders. Of the two orders with a transverse anal aperture, which are also characterised by the absence of bony matter in the dermal system, the Ophidia, or Snakes, are distinguished by the constant want of limbs and eyelids; by their dilatable mouths, moveable facial bones, and by the total want of asternum. In the Lizards or Sauria, the limbs are sometimes entirely absent, or present only in a rudimentary condition; but they are generally pretty well developed, four in number, and adapted for terrestrial or arboreal progression. Their mouths are not dilatable, and the bones of the upper jaw and face are firmly attached to the skull; the eyes are almost always provided with eyelids, and a portion of the ribs is always attached to a sternum. a In the second section, the anal aperture is either rounded or placed in a longitudinal direction, and the dermal skeleton acquires a bony consistence. Of the two orders of which it is composed, the Loricata or Crocodiles are distinguished by their lizard-like | forms, their toothed jaws, and their skin covered with square bony plates imbedded in the corium; whilst in the Tortoises, or Chelonia, the bony plates of the dermal skeleton unite with the ribs and sternum to form a case for the protection of the soft parts of the animal, and the jaws are toothless and armed simply with a horny plate. Orprer I.—Opurpra, General Characters.—Few animals appear to have been, in all ages, the objects of more general aversion than the creatures forming this order. Not to enter upon the question of possible theological grounds for this general disgust, we may take the state- ment in the book of Genesis, that ‘the serpent was more subtle than any other beast of the field,” as a proof that at very early periods the stealthy creeping movements of these creatures had obtained for them the same reputation for cunning that they enjoy in the present day amongst the uninformed—a reputation which has caused them to become one of the most common emblems of deceit; whilst the poisonous properties possessed by some of them, having been extended in the popular mind to the whole group, cause them to be viewed by all with feelings of distrust and dread. In the works of all the older naturalists, the popular notion of a snake as a reptile destitute of feet is adopted; and even in the “ Régne Animal’ of Cuvier, the distinc- tion between the Serpents and Lizards reposes entirely upon the preserce or absence of organs of locomotion. We have already seen, however, how very gradual is the series of steps in the development of the limbs of these animals; and this appears even to have been observed by Linnzeus, who includes in his genus Anguis, all the species of snake-like lizards, whether furnished with rudimentary fect or totally destitute of those organs. The justice of this approximation cannot be doubted, but modern naturalists, instead of placing these animals, with Linnzus, amongst the Serpents, have removed them to the Lizards, with which they agree in most points of their organization. This STRUCTURE OF THE HEAD AND JAWS IN SERPENTS. 3T7 has necessitated the establishment of new characters for the distinction of these two groups, the old division, founded on the presence or absence of the limbs, being evidently untenable under any circumstances; and fortunately there is no difficulty in finding excellent characters for this purpose. One of the principal distinctive characters of the Snakes consists in the peculiar structure of the jaws. The mouth in these animals is exceedingly dilatable; all the bones of the upper jaw and palate are freely moveable, with the exception of the inter- maxillaries, which are firmly attached to the nasal bones; and the two branches of the lower jaw, each of which is composed of several pieces, are united in front by liga- ments and muscles, which permit of their being separated to a considerable distance at the pleasure of the animal. But the principal cause of the immense extent to which the mouth of these creatures is capable of being dilated, consists in the mode in which the lower jaw is articulated to the head (Fig. 76). The mastoid bone, which in most Vertebrata forms a part of the skull, is here moveable and only attached to the skull by ligaments and mus- eh oe . * cles. It bears at its astucnitt - long, somewhat a CP ene cylindrical bone, called the tympanic bone, to the opposite extremity of which the lower jaw is articulated ; and as the tympanic bone usually takes an oblique direction, downwards and backwards, it often extends considerably behind the back of the skull, and thus enables the mouth to open beyond the head. The jaws are always armed with hooked conical teeth, which serve only to hold the prey and assist in its progress down the throat; but the arrangement of these varies considerably in the different groups. In the innocuous snakes, the teeth all form solid cones, and are arranged in continuous rows round the whole of the upper and lower jaws, the palatine bones also bearing another double row of teeth. In many of the venomous species the maxillary bones are reduced to a rudimentary condition, and bear only a pair of long, acute, perforated teeth, which can be raised or depressed at will by the action of peculiar muscles. These, in fact, form a pair of tubes, commu- nicating by ducts with the poison glands, and through which the venomous secretion of these glands is injected into the wounds made by the animal. The teeth of the palate and lower jaw are arranged in these’snakes more or less after the same fashion as in the harmless species, but those of the true upper jaw are of course wanting, and this has given rise to an opinion that venomous snakes might be known by the want of maxillary teeth. This, however, is a mistake, as some of the most deadly species are furnished wiih a few teeth behind the poison fangs; and in some, which are suspected of poisonous properties, the upper jaw bears one or more large furrowed fangs towards its hinder part, its anterior portion being furnished with small solid teeth of the ordi- nary kind. Snakes, like almost all other Reptiles, live entirely by the capture of living prey, and as their teeth are not adapted for the division of their food, they are of course compelled to swallow it whole, As their victims are often of considerable size, this operation is not unfrequently attended with difficulty ; but the form and arrange- ment of the teeth and jaws are most admirably adapted for the peculiar exigencies of their mode of life. Dilating its mouth to the utmost, the Snake seizes upon one end of the dead body of its victim, and by the continual action of the jaws and teeth, gradually draws it into its throat, a process which, perhaps, might rather be described 376 STRUCTURE OF SERPENTS. as the gradual extension of the Snake over the body of its prey. The consumption of this mass of food takes place very slowly, and many Snakes, after a full meal, pass 4 month or six weeks in a state of torpidity, whilst the operation of digestion is going on, The general form of these Reptiles is too well known to need description. They are totally destitute of limbs; the scapular arch and sternum are entirely wanting, and the only trace of the posterior extremitics consists in a pair of small bones, repre- senting the pelvis, and sometimes a second pair, corresponding with the hind limbs, which are found suspended in the muscles on each side of the vent in a few species. These bones occasionally bear a sort of horny claw, which projects slightly from the skin, on each side of the anus; but these organs are usually so small, that they can be of but little use to the animal. Their movements are entirely effected by the agency of the very flexible vertebral column, and the exceedingly moveable ribs. The latter are excessively numerous, extending from the neck to the extremity of the belly, or even beyond this into the tail, and the animal, when gliding along the ground, may be considered to be walking upon the free extremities of the ribs, much in the same way that the Millepedes (Juli, vol. i. p. 830) progress by the action of their innumerable little legs, The skin appears to be covered with scales and plates, from the existence of numerous scaly appendages of the corium; these, however, are completely covered by the epidermis, which embraces them closely, and follows all the irregularities of . surface, so that when the epidermis is cast it presents, as it were, an exact mould of all the elevations and depressions which existed upon the animal. On the upper surface of the body these dermal appendages have the form of seales; on the head and belly they are usually converted into plates, or shields, of larger or smaller size, and either of a hexagonal or quadrangular figure. The peculiarities of these organs furnish valuable characters-fur the classification of these animals. The eye, as already stated, is destitute of lids, and covered with a glassy capsule, within which the eye is capable of moving freely. The cars are not visible externally ; the nostrils are placed on the snout, and often quite at its extremity, and the tongue is very long, thin, bifid, and protrusible. There is usually only a single large lung, situated on the left side of the body—that of the right side is generally quite rudi- mentary. The trachea is very long, and often cellular, so that the distinction between the trachea and the lung is sometimes difficult of recognition, and the hinder part of the long lung is frequently destitute of cells, forming a simple sac, which probably serves as a reservoir of air. The other internal organs are also much clongated, in accordance with the general form of the body, and the gall bladder is often separated from the liver by a considerable interval. Divisions,—The classification of these Reptiles presents considerable difficulties, and scarcely any two authors are agrecd as to the limits of the subordinate groups, or the order in which they should be arranged. The general arrangement here adopted is much the same as that given by Dr. Gray in his Catalogue of the Snakes in the British Museum. He divides the order Ophidia into two sub-orders, the Viperine, or essen- tially venomous Serpents, with weak jaws, of which the upper is entirely destitute of teeth, except the two large poison fangs, and the Colubrine Snakes, which are, for the most.part, harmiess, although the upper jaw, in many species, bears fangs, besides the ordinary solid, maxillary teeth. E ; THE VIPERINE SNAKES. 379 Scun-orper J.—Virerina. General Characters.—The Viperina, or Venomous Snakes par excellence, are distinguished from all others by the peculiar arrangement of the teeth in the upper jaw. The true maxillary bones are reduced to a very small size, capable of a great " amount of motion, and bear a single pair of long curved fangs,* which can be laid flat in the mouth during repose, or erected when in action by the agency of peculiar muscles. These are the only teeth supported by the maxillary bones; they are perfo- ; rated throughout by a slender canal, which communicates with a large gland situated in the head, behind and under the eyes. This secretes the venomous fluid, which passes through a duct to the base of the tooth, and thence through the canal in its interior, until it is injected into the wound made by the bite of the Serpent. Its propul- sion is effected partly by the contraction of the proper walls of the gland, and partly by the pressure of the muscles of the jaws, which act upon it during their contraction (Fig. 77). The poison which is thus injected into the wound mixes with the blood, and is then carried into the circulation, when it speedily produces an injurious effect, giving rise to an altered condition of the blood, which, if the poison be present in sufficient quantity, quickly renders it inca- | pable of supporting life. In fact, a bite from one of the large poisonous Snakes of tropical climates is generally fatal, even to man, if the animal be in a vigorous con- | dition and provided with a good supply of poison ; but a bite froma similar Snake, : after it has nearly exhausted its venom by & previous attacks, may give rise to little or Fig. 77.—Head of Rattlesnake, with the skin no inconvenience. It is remarkable, also,