HARVARD UNIVERSITY WITH AWN Libary DESBe NGS Comparative Zoology wo ls weer 7A May 28 2.1942 725 ss a» ny =. 7 % -*s.' * = ' ‘ ' THE Cov BRIDGE NARORAL HISTORY S. F. HARMER, Sc.D., F.R.S., Fellow of King’s College, Cambridge ; Superintendent of the University Museum of Zoology AND. A. E. SHIPLEY, M.A., Fellow of Christ’s College, Cambridge ; University Lecturer on the Morphology of Invertebrates VOLUME VIII wl oy Wy Wwel[rutoe ye uopuoT Sa1d3 4 GQNV VWISIHdWY JO NOILNGIYLSIA 4VvOlHav¥9039 FHL ONILO344V GQIYOM AHL AO SSAYNLV3S TWOISAHd — aes , a 2 7 rein oar Sy Sees TSH TIOSGNG UaZOdy Apuaueussed jo QUT eaUuo7 papooy a2e49d Wa) UJA\Y}4ION ‘uonejagen padnisezuiun | SNONUIZUOD LAIM §9SI404 [2OIAOL SUYBUUPAED P SOWIE) "999/90d, qed qSow Pi Wy Sees HES Pp XKeseg = "==="="= $AJBSET] od Eee Pour Aa een ea la Tine a 17 -udoo|ude9 . 4o| 01 — ra ce Jo S1douy AMPHIBIA AND REPTILES By Hans Gapow, M.A. (Cantab.), Ph.D. (Jena), F.R.S., Strick- land Curator and Lecturer on Advanced Morphology of Vertebrata in the University of Cambridge London MACMILLAN AND CO, LIMITED NEW YORK: THE MACMILLAN COMPANY IQOI All rights reserved ee Th the “yt : 20 Ala UE ie. tn rire PREFACE LiInNAEUS had but a poor opinion of the Amphibia and their describers, or he would not have called the former “ pessima tetraque animalia,” nor would he have dismissed the latter with the terse remark: “ Amphibiologi omnium paucissimi sunt nullique veri.” That was, however, nearly 150 years ago; and at the present time there are fewer difficulties in writing a book on Amphibia and Reptiles. Those who care for the study of Amphibia and Reptiles —the Herpetologists, to give them their scientific title—have never been numerous; but most of them have been serious students. One reason for the fact that this branch of Natural History is not very popular, is a prejudice against creatures some of which are clammy and cold to the touch, and some of which may be poisonous, People who delight in keeping Newts or Frogs, Tortoises or Snakes, are, as a rule, considered eccentric. But in reality these cold-blooded creatures are of fascinating interest provided they are studied properly. The structure of animals is intimately connected with their life-habits ; and this correlation is perhaps more apparent in Amphibia and Reptiles than in any other class. The anatomist who studies internal and external structure is as much struck with the almost endless variety in details as he who takes the trouble to observe the living animal in its native haunts, or at least under conditions not too unnatural. He will agree with V. von Scheffel’s Toad “that those above seem to have no Vi PREEACE notion of the beauties of the swamp ”—brilliantly coloured Newts engaged in amorous play, concert-giving Frogs, and meta- morphosing Tadpoles. The motto assigned to the Reptiles seems singularly appropriate when we consider that poisonous snakes have been developed from harmless forms, and that many kinds of reptiles have lost limbs, teeth, and eyesight in the process of evolution. The present work is intended to appeal to two kinds of readers to the field-naturalist, who, while interested in litfe- histories, habits, and geographical distribution, beauty or strange- ness of forms, is indifferent to the homologies of the metasternum or similar questions ;—and to the morphologist, who in his turn is liable to forget that his specimens were once alive. A great portion of the book is anatomical and systematic. It was necessary to treat anatomy, especially that of the skeleton, somewhat fully, since it has long been recognised that it is impossible to base a scientific classification upon external characters. The reader familiar with Vertebrate anatomy has a right to expect that questions of special morphological interest will be dwelt upon at length. Those who have no anatomical foundation must be referred to one of the now numerous intro- ductory manuals on the subject. The account of the Amphibia is more complete than that of the Reptilia. It was possible to diagnose practically all the recent genera; and this has been especially done in the Anura, in order to show how in an otherwise very homogeneous group almost any part of the body, internal or external, can be moditied in kaleidoscopic variety. The same could not be done with the Reptilia. Their principal groups,—called sub-classes in the present work, in order to emphasise their taxonomic importance in comparison with the main groups of Birds and Mammals,— differ so much from each other that it was decided to refrain PREFACE Vil from attempting a general account of them. Moreover, the number of species of recent lizards and snakes is so bewilder- ing, the genera of many families being but tedious variations of the same theme, that only those forms have been described which are the most important, the most striking, or which the traveller is most likely to come across. The student who wishes to go farther into systematic details must consult the seven volumes of the Catalogue of Reptiles in the British Museum (London, 1889-1896). Mr. G. A. Boulenger, the author of this magnificent series, has rendered the systematic treatment of recent Amphibia and Reptiles an easy task. During many years of the most friendly intercourse I have profited on count- less occasions by his ever-ready advice. Although he has kindly read the proofs of the part dealing with the Amphibia it would be unfair to associate him with any of its short- comings or with contestable opinions, for which I alone am responsible. ¢ Cope’s large work on the Crocodilians, Lizards, and Snakes of North America (Rep. U.S. Nat. Mus. for 1898 (1900)) has unfortunately appeared too late to be used in the present work. The drawings on wood were, with few exceptions, made by Miss M. E. Durham, mostly from living specimens—-a procedure which has to a great extent determined the selection of the illustrations. Since both the metric and the English systems of measure- ments have been employed, it may be well to state for the convenience of the reader that the length of a line of the text is four inches or approximately ten centimeters. I have frequently and freely quoted accounts of previous authors instead of paraphrasing them. Especial thanks are due to Messrs. Longmans, Green, and Co., and to Messrs. Murray, Vili PREFACE for their courteous permission to make several long quotations from Sir J. E. Tennent’s Ceylon, and from H. W. Bates’ Naturalist on the River Amazons. Lastly, a remark about my Editors. Instead of being a source of annoyance they have rendered me the greatest help. H. GADOW. CAMBRIDGE, December 19, 1900. CONTENTS PREFACE SCHEME OF THE CLASSIFICATION ADOPTED IN THIS Book PART I.. AMPHIBIA CHAPTER 1 CHARACTERS AND DEFINITION—POSETION OF THE CLASS AMPHIBIA IN THE PHYLUM VERTEBRATA—HISTORICAL ACCOUNT OF THE CLASSIFICATION OF AMPHIBIA Oils VE Ds aE SKELETON OF URODELA AND ANURA—SKIN—COLOU R-CHANGING MECHANISM— PoIsON-GLANDS—SPINAL NERVES—RESPIRATORY ORGANS—SUPPRESSION oF LuNGs—URINO-GENITAL ORGANS—FECUNDATION—NURSING HABITS —DEVELOPMENT AND METAMORPHOSIS CHAPTER III NEOTENY—REGENERATION—TEMPERATURE—GEOGRAPHICAL DISTRIBUTION . CHAPTER IV STEGOCEPHALI Ok LABYRINTHODONTS— LISSAMPHIBIA—APODA CHAPTER V LIsSAMPHIBIA (CONTINUED)—URODELA CHAPTER VI LISSAMPHIBIA (CONTINUED)—ANURA PAGE 11 63 78 94 X CONTENTS PART IL, REPTILTA CHAPTER VII DEFINITION AND CHARACTERS—POSITION OF THE CLASS REPTILIA IN THE PHYLUM VERTEBRATA—CLASSIFICATION—SKULL AND VERTEBRAE . CHAPTER VIII PROREPTILIA—PROSAURIA—THEROMORPHA CHAPTER Ix CHELONIA—ATHECAE—THECOPHORA CHAPTER X DInosauRIA—CROCODILIA CHAPTER XI PLESIOSAURIA—ICHTHYOSAURIA— PTEROSAURITA—PYTHONOMORPHA CHAPTER XIl SAURIA—AUTOSAURI OR LACERTILIA—-LIZARDS CHAPTER XIII SAURTA (CONTINUED)—OPHIDIA—SNAKES INDEX PAGE 277 bo (o'2) Or 473 SCHEME OF THE CLASSIFICATION ADOPTED IN THIS BOOK CLASS AMPHIBIA. Sub-Class. Order. Sub-Order. Family. Sub-Family. Stegoce- ~ BRANCHIO- phali Lepo-} sAurt(p. 80). spondyli AISTOPODES (p. 80) | (p. 81). Stegoce- STEGOCE- anee rame PHALI (p. 78) (p. 81) Stegoce- phali Stereo- spondyli (p. 83) “Apoda CoECILIIDAE(p.89). (p- 84) ‘ AMPHIUMIDAE (p. 97). ‘ Desmognathinae (p. 102). Urodela |} SALAMANDRIDAE | Plethodontinae (p. 103). (p. 94) ° . (p. 102) i Amblystomatinae (p. 109). Salamandrinae (p. 115). PROTEIDAE (p. 182). SIRENIDAE (p. 136). AGLOSSA (p. 143). ( DIscoOGLOSSIDAE (p. 152). LISSAM- 4 Peon acme BUFONIDAE (p. 166). Amphignathodontinae Anura |} 4, | LLXEIDAR (p. 185) (pv: 188). (p. 138) } PHANERO- j Hylinae (p. 189). riage 7 { Hemiphractinae (p. 210). Gp, 152) CYSTIGNATHIDAE } Cystignathinae (p. 211). (p. 209) © |) Dendrophryniscinae _ (p. 224). aren ie : ( Engystomatinae (p. oe ee Dyscophinae (p. 235). aoe) Genyophryninae (p. 236). | Ceratobatrachinae (p. 237). RANIDAE (p. 237) , Raninae (p. 238). Dendrobatinae (272). — iw) i | Xi SCHEME OF CLASSIFICATION CLASS REPTILIA (p. 277). PROREPTILIA (p. 285). ryops (p. 286). Cricotus (p. 287). Sub-Class. Order, Sub-Order Family. Microsauri (p. 288). cae ei | Prosauri { PROTOROSAURI (p. 290). (p. 290) \ RuayNcHocEPHALI (p. 292). * Pareiasauri (}). 304). cee pHa | Theriodontia (p. 306). (p. 300) Anomodontia (}). 309). eae vrs | Placodontia (p. 311). Atheca (p. 333) SPHARGIDAE (p. 333). ( CHELYDRIDAE (p. 338). DERMAPEMYDIDAE (p. 341). CRYPTODIRA CINOSTERNIDAE (p. 342). (p. 338) ‘| PLATYSTERNIDAE (p. 345). CHELONIA | tesreorsias (p. 345). p. 312) CHELONIDAE (p. 378). eee ‘| a cae ( PELOMEDUSIDAE (p. 390). Peed, eS Baavil , CHELYDIDAE (p. 399). Pe eee, | CARETTOCHELYDIDAE (p. 404). TRIONYCHOIDEA TRIONYCHIDAE (p. 404) (p. 404). ‘ Sauropoda (p. 418). Theropoda (p. 420). ag ere DINOSAURIA (p. 425). (p. 412) Orthopoda ORNITHOPODA (p. 424) (p. 426) Ceratopsia (p. 430). ( Pseudosuchia (}). 452). Parasuchia (p. 433). ( TELEOSAURIDAE (p. 450). METRIORHYNCHIDAE (p. 451). CeCe ee MACRORHYNCHIDAE (p. 461). eae Eusuchia(}). 434) < GAVIALIDAE (p. 451). iosttinotar (p. 453). (GONIOPHOLIDAE (p. 453). CROCODILIDAE (p. 454). Nothosauri f MuEsosauRIDAE (p. 476). PLESIO- (p. 476) 7 : * \ NorHOSAURIDAE (p. 477). SAURIA 2 ( PLIOSAURIDAE (p. 477). ae lesi ri pe (p. 4738) eae PLESIOSAURIDAE (p. 478). er) 2 ; ~ | ELasmosavRIDAE (p. 478). ey Wao Ichthyosauri (p. 478) (p: 263) “ PrERODACTYLI P once mn Pterosauri | (p. 486). 184) (p. 486) | PTERANODONTES (p-. 404) Bola 487). ‘ Dolichosauri | (p. 489). Mosasauri (p. 489). PYTHONO- MORPHA (p. 487) SCHEME OF CLASSIFICATION Xili Sub-Class. Order. Lacertilia (p. 491) SAURIA (p. 491) Ophidia (p. 581) Sub-Order. GECKONES (p. 502) 4 LACERTAE (p. 518) | CHAMAELEON- TES (p. 567) Family. Sub-Family. ‘ Geckoninae (p. 507). GECKONIDAE Eublepharinae (p. 507) ly, Sp. G1 2): | Uroplatinae (p. 512). AGAMIDAE (p. 515). IGUANIDAE (p. 528). XENOSAURIDAE (p. 536). ZONURIDAE (p. 536). ANGUIDAE (p. 537). HELODERMATIDAE (p. 540). LANTHANOTIDAE (p. 541). VARANIDAE (p. 542). XANTUSIIDAE (p. 547). TEJIDAE (p. 547). LACERTIDAE (p. 549). GERRHOSAURIDAE (p. 559). ScINCIDAE (p. 559). ANELYTROPIDAE (p. 564). DIBAMIDAE (p. 564). ANIELLIDAE (p. 564). AMPHISBAENIDAE (p. 565). | PYGOPODIDAE (p. 567). Je See J CHamABLEoNTIDAE (p. 573). r TYPHLOPIDAE (p. 593). - GLAUCONIIDAE (p. 594). ILYSIIDAE (p. 594). UROPELTIDAE (p. 595). _ { Pythoninae (p. 598). Borax (p. 596) ) Buinae (p. 601), XENOPELTIDAE (p. 605). (800). Lae, (p. 606). Aglypha } coittbrinae (p. 607). (p- / | Rhachiodontinae (p. 622). Dipsadomorphinae (p. 623). Elachistodontinae (p. 625). Homalopsinae _ (p. 625). ( Elapinae (p. 626). + Hydrophinae. (p- 635). Opistho- glypha - (p. 623) | A Protero- elypha (p. 625) AMBLYCE- PHALIDAE (p. 637 ) CoLUBRIDAE (p. 606) { Viperinae (p. 638). | Crotalinae (p. 644). VIPERIDAE (p. 637) 3 oe —— 7 ee > - a) _ i wi . ae > 2 S . a oe rea 2a a Van - 7 = ae , 1 1 = : a a ie a) Jet . he . - ee - oe _ — aah 7 i. { => oe AY nee " qe a a “= vp i De a tT: ? ees r=. oa oo oo! - “Se, “tT ae Cen et ee ee * Te 7 sy = 1.4% _ Gen he ee le, _ a ink 9 > a an} i : “6 a ‘if BA oi xy ie at vue Pie : @ fades LU) “LY 1 Al a 4 ~ mI — - = 7 oe 7 Ww p 5 a _ - - 7 es ; mae : on © > i iis - : L o a i A _ i a - - i - ‘ ( ae J 7 Ww. : - Men) - so At “¢ ' 1&,; 7 oe ae ; ae 4 y -) “a! a. ae F . td 7 “ 7 7 \ 5 = _ Mi - = ied > Wy 8 rem a lo Sore ‘ .° - 7 - 7 : a 6 _ e aA ~ : - ya. 7 a - ‘ow -_ : ee m_. ba = a ad oy i] ’ ae , AS 71 Aa . i » tad! ‘ : Jae eae ee ee —> — es ah Li rae, ye a Pr 3 ‘wis — : an 7 : 7 wy _ vb) 7 ‘ . [- i e q a 0 7 bh - me Vs d : 3 - 67 Ps ba Ghat. " er oa ae Cal “china ah - 7 , re ey i" ’ i eek bh : _ ae fi pean » aa — 7 : ' hi ma. [io . 41% : . ™ : " us a) 7 ce i : +, 7 pet ie Se a) af ; ° ’ T van _) ou ¢ “a 7 | y je Co ¥& & | 7 7 : sv —, ae ey a vey _ | es se - 1 7 ~e ; RAY ait a.) ‘ Via a ee “ , 7 4-¥ ms t, Rees f 4 ee a ~~ nt j - ? iad ge a, =e : aay? : hel 7 es 7 7 re a | a le } +. " 7% : 1 ‘j 7 _ eo 7 y Cor & ~s a = iM =~ [te a - a . > _ 7 - U — a vy i ' 7 ts a an 7 ae ani Vat 7 a 7 = 7 _ > 16 : : - = 7 -_ i Pres a. 4, 7 ae ia _ 7 “ eu i » aT i. a ! 1) tt a 7 . | ; me a fe» aye TN anse & \aear . We = i es tid iy, nee ( 7 a + ar ten on | + - a frees 2 i oar) 7 e Amt ie © - 7 a « rece Pe de 6h he oe er oe ra 7 - 4 _ z ‘ Vv. Aa 1G Bre, 2 x 146 ‘ t eu : i 7 = : 2 oe ET aetna oh. i UTE ¥ 9 (ee ae ‘- “Tira > 1 a . ie a U - - : : wy * 7 ye 2 = , The ra > ul a an ® ® Phi ne . >=) : By a i ia A = = 7 ye > ' eA > _ eens: , y=, 7 7a — - ea 7 es y Vo a ii aa 9 : yi ag ae , : - rh 5s oe ah | - Mas a > 7 ig 7 i ies). " 7 7 oe td ae ' in = ‘ ‘(oe ca es : - ; Saas ii - ae) ry I ; ; ie * i A ws ‘ oO » oe | a : 7 f . Pa e io pais _ . , is -7 ‘ : : ue 7 i ni ey i ; oe - 7A ai ios a - 7 . ’ 7 5 F ? - 7 ae 7 Z a. _ = - A 7 ~~? & — ass a ‘oo a a98 - 7 : ~ 16 rw : pe. & ‘ »\ 7 _ rr - 7 . ' 7 ri. ~~ ee , wf a or > Oa ari : : - i, arene, * a - : 7 , i] - bey \ ’ 7 7 - ee ? x = "se . “o2 son. a : j : - (ary & is : - — Ooo - “- a. ie : 7 a2 13h a i oe a 8. ; - ar Py =) a“ he “9 &) can eee ov. ie _ a a a X@ aoe ee oo Toes —. en e+ vei i ~~ . A pe ae ae ja (e _ 4 =o , ic fot f ; > - ae Se ee oe at) ange = 5 gee i te = ee) ne © PART AMPHTIBLA VOL. VIII £ ««’s scheint, dass die hier oben keine Ahnung haben von dem Sumpf und Seiner Pracht.” The ‘‘ plattgedriickte Krote,’ ScHEFFEL’s TJ'rompeter von Sdkkingen. CRAP TER: o AMPHIBIA CHARACTERS AND DEFINITION——POSITION OF THE CLASS AMPHIBIA IN THE PHYLUM VERTEBRATA—HISTORICAL ACCOUNT OF THE CLASSIFICATION OF AMPHIBIA A Birp is known by its teathers, a Beast by its hairs, a Fish by its fins, but there is no such obvious feature which characterises the Amphibia and the Reptiles. In fact, they are neither fish, flesh, nor fowl. This ill-defined position is indicated by the want of vernacular names for these two classes, a deficiency which applies not only to the English language. All the creatures in question are backboned, creeping animals. Those which are covered with horny scales, and which from their birth breathe by lungs only, as Crocodiles, Tortoises, Lizards, and Snakes, are the Reptiles. The rest, for instance, Newts or Efts, Frogs and Toads, are the Amphibia. Their skin is mostly smooth and clammy and devoid of scales; the young are different from the adult in so far as they breathe by gills and live in the water, before they are transformed into entirely lung-breathing, terres- trial creatures. But there are many exceptions. Proteus and Siren the mud-eel, always retain their gills; while not a few frogs undergo their metamorphosis within the egg, and never breathe by gills. If we add the tropical limbless, burrowing Coecilians, and last, not least, the Labyrinthodonts and other fossil forms, the proper definition of the class Amphibia,—in other words, the reasons for grouping them together into one class, separated from the other backboned animals,—requires the examination of many other characters. 4 AMPHIBIA CHAP. So far as numbers of living species are concerned, the Amphibia are the least numerous of the Vertebrata. There are about 40 limbless, burrowing ApopA; 100 URoDELA or tailed two- or four-footed newts, and about 900 ANuRA, or tailless, four-footed frogs and toads; in all some 1000 different species. Few, indeed, in comparison with the 2700 Mammals, 5500 Reptiles, nearly 8000 Fishes, and almost 10,000 Birds. But we shall see that the Amphibia have not only “had their day,’ having flourished in bygone ages when they divided the world, so far as Vertebrata were concerned, between themselves and the Fishes, but that they never attained a dominant position. Inter- mediate between the aquatic Fishes and the gradually rising terres- trial Reptiles they had to fight, so to speak, with a double front during the struggle of evolution, until by now most of them have become extinct. The rest persist literally in nooks and corners of the teeming world, and only the Frogs and Toads, the more recent branch of the Amphibian tree, have spread over the whole globe, exhibiting almost endless variations of the same narrow, much specialised plan. The greatest charm of the Anura lies in their marvellous adaptation to prevailing circumstances; and the nursing habits of some kinds read almost lke fairy-tales. Characters of the Amphibia.’ |. The vertebrae are (a) acentrous, (b) pseudocentrous, or (c) notocentrous. The skull articulates with the atlas by two condyles which are formed by the lateral occipitals. For exceptions see p. 78. 3. There is an auditory columellar apparatus, fitting into the fenestra ovalis. 4. The limbs are of the tetrapodous, pentadactyle type. 5. The red blood-corpuscles are nucleated, biconvex, and oval. 6. The heart is (a) divided into two atria and one ventricle, and () it has a conus provided with valves. The aortic arches are strictly symmetrical. 8. Gills are present at least during some early stages of development. 9. The kidneys are provided with persistent nephrostomes. 10. Lateral sense-organs are present at least during the larval stage. 11. The vagus is the last cranial nerve. 12. The median fins, where present, are not supported by spinal skeletal rays. 13. Sternal ribs and a costal or true sternum are absent. 14, There is no paired or unpaired medio-ventral, copulatory apparatus. 15. Development takes place without amnion and allantois. to None of these characters is absolutely diagnostic, except 1 (c¢), and this applies only to the Anura and most of the Stegocephah.. ! References to explanations of the terms used below will be found in the index. I CHARACTERS AND POSITION 5 Numbers 1 (6), 1 (c), 2, 3, 4 and 12 separate the Amphibia from the Fishes. Numbers 1, 6 (0), 7, 8, 9, 11, 13, 15 separate them from the Reptiles, Birds, and Mammals. Number 2 separates them from the Fishes, Reptiles, and Birds. Number 5 separates them from the Mammals. Number 6 (a) separates them from the Fishes (exel. Dipnoi Mammals. , Birds and We can, therefore, very easily detine all the Amphibia, both recent and extinct, by a combination of the characters enumerated above. For instance, by the combination of numbers 2, 3 or 4 with either 7, 8, 9, 11, 13 or 15. Amphicondylous Anamnia would be an absolutely correct and all-sufficient diagnosis, but it would be of little use in the deter- mination of adult specimens; and the tetrapodous character is of no avail for Apoda. Amphicondylous animals without an intra- cranial hypoglossal nerve is a more practical diagnosis. In the case of living Urodela and Anura the absence of any scales in the skin affords a more popular character; it is unfor- tunately not applicable to the Apoda, many of which possess dermal scales, although these are hidden in the imbricating transverse rings of the epidermis; and the frequent occurrence of typical scales of both ecto- and meso-dermal composition in many of the Stegocephali forces us to discard the scales, or rather their absence, as a diagnostic character of the class Amphibia. The same applies to the mostly soft, moist, or clammy, and very glan- dular nature of the skin. The position of the class Amphibia in the Phylum Verte- brata.—There is no doubt that the Amphibia have sprung from fish-like ancestors, and that they in turn have given rise to the Reptilia. The Amphibia consequently hold a very important intermediate position. It was perhaps not a fortunate innoya- tion when Huxley brigaded them with the Fishes as /ehthyopsida, thereby separating them more from the Sawropsida (= Reptilia and Aves), than is justifiable——perhaps more than he himself intended. The connecting-link, in any case, is formed by the Stegocephali; all the recent Orders, the Apoda, Urodela, and Anura, are far too specialised to have any claims to the direct ancestral connections. The line leading from Stegocephali to fossil Reptiles, notably to such Proreptilia as Hryops and Cricotus, and even to the Lepospondylous Prosauria, is extremely gradual, and the steps are almost imperceptible. | Naturally, 6 AMPHIBIA CHAP. assuming evolution to be true, there must have lhved countless creatures which were a “rudis indigestaque moles,” neither Amphibia nor Reptilia, in the present intensified sense of the systematist. The same consideration applies equally to the line which leads downwards to the Fishes. But the great gulf within the Vertebrata hes between Fishes and Amphibia, between absolutely aquatic creatures with internal gills and “ fins,” and terrestrial, tetrapodous creatures, with lungs and fingers and toes. On the side of the fishes only the Dipnoi and the Crosso- pterygil come into consideration. The piscine descent of the Amphibia is still proclaimed by the following features.—(1) The possession by the heart of a long conus arteriosus, provided with, im many cases, numerous valves, or at least (Anura) one series at the base, another at the beginning of the truncus where the arterial arches branch off; (2) the strictly symmetrical arrangement of these arches; (3) the trilocular heart is still like that of the Lung-fishes or Dipnoi ; (+) the occurrence of as many as four or even five branchial skeletal arches in the larval stage; (5) the glottis is supported by cartilages which themselves are derivatives of posterior visceral arches ; (6) the development of the vertebrae (Stegocephali and Urodela) from four pairs of arcualia, and the formation of the intervertebral joints by a split across the intervertebral ring of cartilage: this feature is unknown in Reptilia, but it occurs also in Lepidosteus, most probably also in Polypterus ; (7) the hypo- glossal still retains the character of a post-cranial or cervical spinal nerve; (8) the presence of lateral sense-organs; (9) the possession of external gills is of somewhat doubtful phylogenetic value, although such gills occur amongst fishes only in Dipnoi and Crossopterygii. It is not unlikely that in the Amphibia these organs owe their origin to entirely larval requirements, while the suctorial mouth of the larvae of the Anura and many fishes has certainly no ancestral meaning, but is a case of con- vergent development. The usual diagnoses of the Amphibia contain the statement that they, or most of them, undergo a metamorphosis, or pass through a larval stage. The same applies to various fishes ; while, on the other hand, the larval (not ancestral) stage has become permanent in the Proteidae and Sirenidae; and lastly, we cannot well speak of larvae in the viviparous Sa/amandra atra. I CLASSIFICATION 7 The evolution of an adequate classification of the Amphibia has been a long process. Even their recognition as a class, separate from, and of equal rank with that of, the Reptilia, was by no means generally accepted until comparatively recent times. A historical sketch of the laborious, often painful, striving for light, in France and Germany, then in England, and lastly in America, is not without interest. The term Amphibia was invented by Linnaeus for the third class of animals in his famous “Systema Naturae.” It comprises a very queer assembly, which, even in the 13th edition (1767), stands as follows :— |. REPTILES PEDATI, with the four “genera” Testudo, Draco, Lacerta, and Rana. Lacerta includes Crocodiles, Lizards, and Newts! 2. SERPENTES APODES. ; 3. NANTES PINNATI. Elasmobranchs, Sturgeons, Lampreys, and various other fishes. Laurenti, 1768, in a dissertation entitled “Specimen medicum, exhibens Synopsin Reptilium . . .,” uses Brisson’s term, Reprines, and divides them into :— REPTILIA SALIENTIA, these are the Anura. YRADIENTIA, namely the Urodela and Lizards. SERPENTIA, the Snakes and the Apoda. Brongniart, 1800, “Essay d’une classification naturelle des Reptiles,” ! dis- tinguishes :— CHELONI, SauRt, OpHipi, BarRacHir; the last for the Frogs, Toads, and Newts. Latreille, 1804, “ Nouveau Dict. Hist. Nat.” xxiv.,2 accepts the four Orders of Brongniart’s “ Reptiles,’ but clearly separates the fourth Order, “Barracuy,” from the rest by the following, now time-honoured, diagnosis: Doigts des pattes nayant pas Wongles; des branchies, du moins pendant wn temps; des métamorphoses. But there is not one word about “ Amphibia” in opposition to “ Reptilia.” Duméril, 1806, “ Zoologie analytique” (p. 90), and “Elémens de Vhistoire naturelle,” 1807, divides the “ Reptiles batraciens,” or “ Batracii,” into Ecaupatr and Caupatt; he also introduces the terms ‘“ ANOURES” and “ Urop&LES” as their equivalents ; but since these terms appear in the French form purists do not admit their having any claim to recognition ! Oppel, 1811, “Die Ordnungen, Familien und Gattungen der Reptilien,” establishes the term Apona for the Coeciliae, and recognises their affinity to the Ecaudata and Caudata by removing them from the Snakes. De Blainville, 1816, “Prodrome dune nouvelle distribution du regne animal ” >— AMPHIBIENS SQUAMIFERES. [The Reptilia. | 3 NUDIPELLIFERES s. Ichthyoides. [The Amphibia. | 1 Bull. Soc. Philom. ii. p. 81. 2 Tableaux méthodiques, yp. 61. 3 Bull. Soc. Philom. p. 113. 8 AMPHIBIA CHAP. Merrem, 1820, “‘ Tentamen systematis Amphibiorum.” PHoutrpora. [The Reptilia. ] BaTRACHIA: APODA. SALIENTIA. | Mutabilia [with metamorphosis, ¢.9. ; : Newts. | Ges aE EEL Amphipneusta [Perennibranchiate Uro- cleles. | F. S. Leuckart, 1821, “ Einiges ueber die fischartigen Amphibien.” ! Monornoa, [The Reptilia. ] with temporary gills: Ecaudata + Caudata aoe t. EN with permanent gills: ‘ Proteidae,’ Meno- poma and Amphiuma. Latreille, 1825, “ Familles naturelles du regne animal.” The Vertebrata are divided into Haematherma and Haemacryma. These terms for warm- and cold-blooded creatures were later on amended by Owen to Haemato- therma and Haematocrya. The latter are divided by Latreille as follows :— Reprinta. Still including the Coeciliae amongst the Snakes. N { Caducibranchiata. AMPHIBIA | es : \ Perennibranchiata, PISCEs. Wagler, 1830, “Systema Amphibiorum.” TESTUDINES, CROcODILI, LACERTAE, SERPENTES, ANGUES, COECILIAE, Ranak, ICHTHYODI. RanaE I. AGLOSSA. a Il. PHANEROGLOSSA: 1. Cauda nulla. [The Anura.] . 55 2. Cauda distinecta. [The Sala- mandridae. } IcntHyopI |. ABRANCHIALES. Menopoma — {Cryptobranchus | and Amphiuma. “: Il. BRANCHIALES. [The Perennibranchiate Urodela. | J. Miller, 1831, “ Beitrage zur Anatomie ... der Amphibien.” ? GYMNOPHIONA, DEROTREMATA, PROTEIDAE, SALAMANDRINA, Bar- RACHIA, J. Bell, 1836, Todd’s “Cyclopaedia of Anatomy and Physiology,” Art. * Amphibia.” AMPHIPNEUSTA, the Perennibranchiate Urodeles; ANouRA, URODELA ; ABRANCHIA, Menopoma and Amphiwma ; Apopa. Stannius, 1856, ‘“ Handbuch der Zootomie: Anatomie der Wirbelthiere.” (2nd ed.) AmpHIBIA Monopnoa. The Reptilia. AMPHIBIA Dipnoa. 1. URopELA. PERENNIBRANCHIATA. DEROTREMATA : Amphiuma and Menopoma, MYCTODERA.? 1 Tsis, 1821. * Treviranus’ Zeitschr, f. Physiol. 1831, p. 190. * 6épn, neck ; wlw, close. 1 CLASSIFICATION 9 2. Barracuta. AGLOSSA. PHANEROGLOSSA : Systomata Ingystomatidae. 3ufoninae. Without manubriun sterni, Raninae. With manubrium. Hyloidea. With adhesive finger- (lises, GYMNOPHIONA., Gegenbaur, 1859, “ Grundziige der vergleichenden Anatomie.” AMPHIBIA as a separate class, equivalent to that of the Repriia, are divided into the four Orders: PERENNIBRANCHIATA, SALA- MANDRINA, BATRACHIA, and GYMNOPHIONA. In the second edition of the ‘“ Grundziige” (1870) they are divided into URODELA, ANURA, and GYMNOPHIONA. Huxley, 1864, “The Elements of Comparative Anatomy.” MAMMALS. SAUROIDS, subsequently changed into Sauropsmpa = Reptilia + Aves. ICHTHYOTDs, 5. a IcHtHyYoPsSIDA = Amphibia Pisces. Haeckel, 1866, “‘ Generelle Morphologie.” Amphibia. A. PHRACTAMPHIBIA s. Ganocephala = Labyrinthodonta + Peromela [Apoda}. B. LIisSAMPHIBIA s. Sozobranchia = Sozura [Urodela] + Anura. Cope, 1869.! STEGOCEPHALI, GYMNOPHIDIA, URODELA, PROTEIDEA, TRACHYSTOMATA, ANURA. Huxley, 1871, “ A Manual of the Anatomy of Vertebrated Animals.” Amphibia I. SavropatRacuta [v.d. Hoeven’s term] s. URoDELA 1. Proteidea. 2. Salamandridae. Il. LABYRINTHODONTA. III. GyMNoPHIONA. IV. BaTRACHIA s. ANURA. Boulenger, 1882, “ Catalogue of the BarracHta GRADIENTIA s. CaupaTa and BATRACHIA Apopa,” divides the Caudata simply into: SALAMAND)- RIDAE, AMPHIUMIDAE, PROTEIDAE, and SIRENIDAE. 1882, “Cat. Batrachia Salientia s. Ecaudata,” see p. 140. Cope, 1890, “Synopsis of the Families of Vertebrata.” ~ Chass BarRACHIA. Sub-Class I. STEGOCEPHALI. Order 1. Ganocephali: Trimerorhachis, Archegosaurus. 2. Rhachitomi: Hryops 3. Embolomeri: Cricotus. 4. Microsauri: PBranchiosaurus, Hylonomus, ete. 1 Proc. Ac. Philad. p. 209. 2 Americ. Natural. xxiii. p. 849. IO AMPHIBIA CHAP. I Sub-Class [I]. Uropeua. Order 1. Proteidae: Proteus. 2. Pseudosauria. [AI] the rest of the Coeciliidae. | 3. Trachystomata: Sirenidae, IIT. SALrentra. P. and F. Sarasin, 1890, “ Zur Entwicklungsgeschichte der Ceylonesischen Blindwiihle, Ichthyophis glutinosa.” ! Sub-Class I, ARCHAEOBATRACHI 8. STEGOCEPHALL Il. NEoOBATRACHT. Order 1. URODELA. a. Salamandroidea. [The Urodela. ] b. Coeciloidea = Amphiumidae + Coeciliidae. 2. ANURA. Urodela + The classification adopted in this volume is as follows :-— CLASS AMPHIBIA. Sub-Class I. Phractamphibia. Order I. Stegocephali Lepospondyli. Sub-order 1. Branchiosauri. Sub-order 2. Aistopodes. Order II. Stegocephali Temnospondyli. Order III. Stegocephali Stereospondyli. Sub-Class I]. Lissamphibia. Order I. Apoda. Order LI. Urodela. Order II]. Anura. Sub-order 1. Aglossa. Sub-order 2. Phaneroglossa. 1 Sarasins’ Ergebnisse . . . Ceylon, 1887-1890. (Ghia hee ines Ma rl hea SKELETON OF URODELA AND ANURA—SKIN—COLOUR -CHANGING MECHANISM — POISON -GLANDS——-SPINAL NERVES RESPIRA- TORY ORGANS—SUPPRESSION OF LUNGS——URINO -GENITAL ORGANS-— FECUNDATION— NURSING HABITS——DEVELOPMENT AND METAMORPHOSIS SKELETON OF THE URODELA The vertebral column. The number of vertebrae is smallest in the terrestrial, greatest in the entirely aquatic forms, and is excep- tionally large in the eel-shaped Amphiwma. In the following table the sacral vertebra is included in those of the trunk. Trunk. Tail. Siren lacertina : ay 35 4+ Necturus maculatus —. ett 29 Proteus anguinus ; . 30 28 +4 Cryptobranchus alleghuniensis 20 or 21 24 + (. scheuchzer’ ; : Se ei CL japonicus : ; > ee 22 to 26 Amphiuma means . 63 35 4 Aimblystoma tigrinuii 17 or 16 32 + Salamandra maculosa. . V7 27 Triton cristatus Nz 36 Triton taentatus . : estore 36 + Triton palmatus . : . 14 23 to 25 Salamandrina persprcrllatu . 15 OZ tO 42 Spelerpes fuscus , 3 , 16 a3 The vertebrae of the Urodela and those of the Apoda differ from those of all the other Tetrapoda’ by possessing no special centra or bodies. That part which should correspond with the centrum is formed either by the meeting and subsequent complete co-ossification of the two chief dorsal and ventral pairs of arcualia 1 Credner’s term for all Vertebrates higher than fishes. 1 qe URODELA CHAP. (tail-vertebrae), or entirely by the pair of chief dorsal arcualia. There is consequently no neuro-central suture. Moreover, the central region of each vertebra is strongly pinched in laterally, widening towards the ends. Another feature of the vertebral column of the Urodela is the possession of a considerable amount of intervertebral cartilage, by which the successive vertebrae are held together. This cartilage does not ossify, and it either remains continuous, serving in its entirety and owing to its flexibility as a jot, or it becomes more or less imperfectly separated into a cup and ball portion, the cup belonging to the posterior end of the vertebra. Such joints are called opisthocoelous, and occur in the Desmognathinae and Salamandrinae. In the adult the cup and ball frequently calcify, and the chorda dorsalis or notochord is completely destroyed. Those vertebrae between which the inter- vertebral cartilage remains unbroken, are called amphicoelous, since in them, most obviously in macerated or dried skeletons, the vertebrae appear hollowed out at either end. In such amphicoelous vertebrae a considerable amount of the chorda always remains, running in an unbroken string through the whole length of the vertebral column. ‘Towards adult life the chorda becomes constricted, and is ultimately squeezed out or destroyed, in the middle of the vertebra, by the invasion of cartilage from the chief arcualia. This intravertebrally situated cartilage has been described erroneously as chordal cartilage. The development of the vertebrae proceeds as follows. First appear a pair of basidorsala and a pair of basiventralia (Fig. 1, 1, B.D, B.V), blocks of cartilage, imbedded in and resting upon the thin sheath of the chorda dorsalis. Next appears a pair of inter- dorsal blocks, immediately behind the basidorsals ; and somewhat later appears a pair of interventral blocks. These four pairs of cartilages or “arcualia” each meet, above or below the chorda, and form semi-rings, Which again by extending upwards or downwards fuse into complete rings, in such a way that the interdorsal and interventral elements form the intervertebral mass spoken of above. The basidorsals fuse with the basiventrals, and form the body of the vertebra, the fusion being effected chiefly by the calcification and ossification of the lateral connecting portion of the skeleto- genous layer. The basidorsalia form the neural arches with their unpaired short spinous or neural, and the paired anterior and posterior zygapophysial processes. Concerning the basi- II VERTEBRAL COLUMN I 2 = _ —— —— — = ventralia we have to distinguish between the trunk and the tail. In the latter they produce a pair of ventral outgrowths or haemapophyses, which wltimately enclose the caudal blood-vessels. In the trunk the basiventral blocks of cartilage are suppressed ; they appear in the early larvae, but disappear during or even before metamorphosis. Towards the end of the tail the vertebrae diminish in size, and their constituent cartilages assume a more and more 4 1 2 3 BD N 8D i 8D Fic. 1.—1-5, Five successive stages _A. 1D 2 a wie osx» of the development of a caudal vertebra of a newt; 6-7, the meray =—W Vv vo second and the first cervical ver tebra of Cryptobranchus ; 8-9, BY side view of the constituent cartilaginous blocks of a caudal vertebra (8) and a trunk-ver- tebra (9) of Archegosaurus as typical examples of Temno- spondylous quadripartite and tripartite vertebrae. The cross- hatched parts indicate the artic- ular facets for the ribs. The anterior end of all the vertebrae looks towards the right side. af, In 7, articulating facet for the occipital condyle ; B.D), basi- dorsal piece or neural arch ; L.V, basiventral piece or ven- tral arch ; Ch, chorda dorsalis, or notochord ; J.D, interdorsal piece ; /.V, interventral piece ; I.V.L, intervertebral ligament ; NN, spinal nerve—these are num- bered I, II, III in 6 and7; R, rib; 7, in 7, rib-like tubercle on the first vertebra. indifferent shape, until they become confluent into a continuous rod of cartilage, resembling in this respect the Dipnoi and Holocephali. A periodical revival of this rod, at least of its connective tissue, appears in the tail-filament of the male 7v/on palmatus during the breeding-season. The first vertebra, called the atlas, because it carries the head, is remarkable for the possession of an odontoid process. The latter is formed by a pair of cartilages and represents part of a vertebra, the dorsal portion of which seems to have been added to the occipital part of the cranium. I4 URQDELA CHAP. All the trunk-vertebrae, with the exception of the atlas, carry ribs, at least vestiges thereof. Owing to the early dis- appearance of the basiventral cartilages the capitular portions of the ribs are much reduced, and are mostly represented by strands of connective tissue only. The ribs develop therefore occasion- ally at some distance from the vertebral column, and that por- tion of the rib which in the metamorphosed young newt looks like the capitulum is to a great extent really its tuberculum. Fig. 2.—Transverse section through a Witness the position of the ver- OLE SCR ha ore larva Where rebral arpeny.n which sbi N@mnmnnise mandra maculosa, enlarged. The right side shows the actually existing state, cates the true foramen trans- while on the left side the rib and its ~~... .: Mo SOG , attachments are restored to their pro- ASUS EIN. The homologies ot bable original condition. A, Verte- these parts are still more ob- bral artery within the true transverse —| |. Veyhee fives “t may canal ; B.V, remnant of the basi-ventral scured Dj 1€@ 1act jab a new cartilage ; Ch, chorda dorsalis; Sp.c, process grows out from the rib, spinal canal; *, the false transverse 5 ; LESS ; Say: by which the latter gains a new support upon a knob of the neural arch. Thus an additional foramen is formed, sometimes confounded with the true transverse canal. The meaning which underlies all these modifications is the broadening of the body, the ribs shifting their originally more ventral support towards the dorsal side. The whole process is intensified in the Anura ; it is an initial stage of the notocentrous type of vertebrae. The transverse ossified processes of the adult are often much longer than the vestiges of the ribs themselves, and are somewhat com- plicated structures. They are composed first of the rb-bearing cartilaginous outgrowths of the neural arches ; secondly, of a broad string of connective tissue which extends from the ventro-lateral corner of the perichordal skeletogenous layer to the ribs. The shoulder-girdle is extremely simple. It remains almost entirely cartilaginous, and the three constituent elements are not separated by sutures. Ossification is restricted to the base of the shaft of the scapula, and may extend thence over the glenoid cavity. The coracoids are broad, loosely overlap each other, and are “tenon and mortised” into the triangular or lozenge-shaped II LIMB-GIRDLES [ ut cartilaginous sternum, which latter has no connection with the ribs. The precoracoid is a large, flat process, directed forwards, not meeting its fellow; it is absent in Siren. The humerus articulates with both radius and ulna, and these two bones of the forearm remain separate. The elements which compose the wrist and hand exhibit an almost ideally simple arrangement, slightly varied by the frequent fusion of two or more neighbouring carpalia into one, and by the reduction of the number of fingers. Most frequently the intermedium and the war carpal element fuse together, and there is more often one centrale instead of two. The wrist and hand of the Urodela represent, however, no longer the entirely primitive pentadactyle type, owing to the loss of one finger together with its metacarpal and carpal element. Comparison with the Anura makes it probable that the Urodela have lost the pollex, their four fingers being consequently the 2nd, 3rd, 4th, and 5th. Siren has four or three fingers ; Protews has only three fingers and three large compound carpal cartilages. In Amphiuma, with either three or two fingers, the ulnare, intermedium, and carpale are fused together, the radiale with the neighbouring carpale. The number of phalanges in the four-fingered species is generally 2, 3, 3, 2 respectively. The pelvic girdle.—The ilium stands vertically to the vertebral axis, slanting slightly forwards and downwards. It is attached by means of a rib to only one vertebra, and this ilio-sacral connection is acetabular in its position, ze. it es in the same transverse plane with the acetabulum, in other words vertically above it. The ventral portion of the pelvis is formed by one large continuous mass, the united pubo-ischia, the anterior or pubic portion of which extends forwards in the shape of a broad triangle (Nectwrus) or as a slender, stalked, Y-shaped cartilage, the epipubis, which is often movably jointed at its base. The lateral portion of the pubic cartilage is always perforated by the nervus obturatorius. Ossification is restricted to the ischium and to the middle of the shaft of the ilium. The acetabular fossa for the femur is closed. The tibia and fibula remain separate. The foot is still more primitive than the anterior extremity, as the majority of Urodela possess the full complement of five 2 toes, with 2, 2, 3, 3, 2 phalanges respectively. _Concrescence of d the tarsalia applies most frequently to the fourth and fifth distal 16 . URODELA SA and to the two centrala; exceptional, for instance, in Crypto- hbranchus japonicus, are as many as three centralia, but this is an individual, even a one-sided variation, as shown for instance by a specimen in the Cambridge Museum. Loss of the fifth toe occurs sporadically in genera of different groups, namely, in Salamandrella, Batrachyperus, Salamandrina, Necturus, Manculus, Batrachoseps. In Amphiuwma the number is reduced to three or two; in Proteus to two; and in Stren the hind limbs, with their girdle, are altogether absent. Lastly, in some species of Spelerpes and Batrachoseps both fore and hind limbs have become so small as to be practically without function, parallel cases being found among various Scincidae and other Lizards. The hyoid apparatus is still very primitive in many, especially in larval, Urodela. Besides the hyoid there are as many as four pairs of branchial arches, which, however, decrease in size and completeness, so that the last two have lost their connection with the median copular piece, and become attached in various ways to the second branchial arch. This is the arrangement apparently in all larvae, but four pairs of branchials persist in the adult Siren, Amphiuma, and Cryptobranchus alleghaniensis. The whole branchial apparatus is reduced to three pairs of arches in Necturus and Proteus, to two in the adult Crypto- branchus japonicus and in the Salamandridae. Of considerable interest is the vestige of a fifth pair of arches in the larvae of Triton and Salamandra, in the shape of a pair of tiny cartilages, which lie in front and on each side of the opening of the trachea, and give rise to the formation of the laryngeal cartilages, better developed in the higher Vertebrata. The following are noteworthy characters of the skull of Urodela. The articulation of the skull with the vertebral column is not always effected entirely by the two condyles of the lateral occipital bones, but the median basal cartilage often possesses a pair of facets for the odontoid-like process of the first vertebra ; such additional facets are perhaps best developed in Crypto- branchus and in the Salamandrinae. The middle portion of the primitive cranium, from the exit of the optic nerve to the ethmoid cartilage, is formed by a pair of separate bones, the orbito-sphenoids. The parietal and frontal bones remain separate. One or more periotic bones exist, besides the prootic, in the aquatic families. II SKULL 17 A pair of prefrontal bones is present in most Salamandridae, e.g. Salamandra, Triton, Amblystoma, especially in the larva, and in Cryptobranchus; these bones are absent in Amphiuma, Necturus, Proteus, and Siren. The lacrymalia are still separate in some Amblystomatinae, Fic. 3.—Skulls of various Urodela. 1, Salamandra ma- culosa, ventral view, and 2, dorsal view ; 3, Axolotl stage of Amblystoma ; 4, adult stage of Amblystoma ; 5, Salamandrina perspicillata (after Wieders- heim); 6, Salamandra ma- culosa, dorsal view of the lower jaw. A, Articulare; C,, Ci, outer and inner occipital con- dyles ; Ch, choana or posterior nasal opening ; d@, dentary ; L, ethmoid; F, frontal; LO, lateral occipital ; 17, maxillary ; NV, nasal ; No,nostril ; OS, orbito- sphenoid ; P, parietal ; P/, pre- frontal ; P/, palatine; Pim, pre- maxillary ; Po, prootic; PS, parasphenoid; P¢, pterygoid; Q, quadrate ; S, angulo-splenial ; Sq, squamosal ; Sf, stapes ; Vo, vomer ; II, VII, X, exits of the optic, facial, and glosso- vagus nerves. e.g. Ranidens and Hynobius. A pair of nasalia are generally present, but are absent in Neeturus, Proteus, and Siren, The parasphenoid is furnished with teeth in the Plethodontinae and Desmognathinae. Separate palatine bones exist in Necturus and Proteus, and in the larva of Amblystoma, but in the adult form they fuse with the vomers, producing the vomero-palatines characteristic of the majority of Urodela. VOL. VIII C 18 ANURA CHAP. The pterygoid bones are most fully developed, so as to reach the vomero-palatines, in the Amblystomatinae, in Necturus, and in Proteus; they are reduced, so as to leave a gap, in Crypto- branchus, and still more in the Salamandrinae; they are absent in Amphiuma and in Siren. The quadrates are directed forwards in Necturus, Proteus, and Siren, while in the other Urodela they extend transversely and almost horizontally. The hyomandibular remnant, the so-called operculum, is small, and forms a plate which fits into the fenestra ovalis, extending as a ligamentous process upon the quadrate. The quadrato-jugal elements are reduced to ligaments. In many Salamandrinae the large orbito-temporal space is divided into an orbital and a temporal fossa by an arch which is formed by the meeting of two corresponding processes from the squamosal and frontal bones respectively. This bridge is rarely bony (Salamandrina, Triton), mostly ligamentous ;—apparently a reminiscence of the Stegocephalous condition. The two pre- maxillary bones are liable to fuse imto one, for instance in Cryptobranchus, generally in adult Tritons. They are most reduced, and are toothless, in Siren. The two maxillary bones are absent only in Necturus, Proteus, Typhlomolge, and Siren. Their posterior end is frequently free, loosely connected by ligaments with the pterygoid in Crypto- hranchus ; oy with the distal portion of the quadrate, and in this case either just touching it (7'lototriton), or forming a_ broad junction (Pachytriton). Each half of the lower jaw consists of a dentary, articular and angulo-splenial. The splenial remains as a_ separate element in Siren ; in others only during the larval period. There are no mento-Meckelian elements. SKELETON OF THE ANURA The vertebral column.—The distinctive peculiarities ot the vertebrae of the Anura are that they are notocentrous, and that about a dozen of them are modified and fused into an os coccygeum. The whole column is the most specialised found in the Vertebrata; and various stages are rapidly hurried through and obscured caenogenetically during the embryonic development. aired cartilages appear on the dorsal side of the thin chordal sheath, and whilst tending to enclose the spinal cord in a 11 THE DEVELOPING VERTEBRAL COLUMN 19 canal, their bases grow head- and tail-wards into what will ultimately become the intervertebral region. This extension of cartilage leads to a fusion with that of the next following pair of arches, so that the axial column at this early stage consists of aright and left longitudinal ridge of cartilage which sends off dorsal processes, neural arches, in metameric suecession. Next. the intervertebral cartilage increases in such a way as to constrict the chorda either laterally (Rana) or obliquely from above downwards and inwards (Bufo, Hy/a). We ree yonise In this cartilage the interdorsalia. Ventral arcualia are late and much obscured. There is scarcely any cartilage which could represent the interventralia, the intervertebral cartilage being almost entirely made up of the interdorsalia. These fuse together and form a disc or nodule, which later fuses either with the vertebra in front, and in this case fits into a cup carried by the vertebra next behind (procoelous vertebrae), or the knob is added to the front end of the vertebra, fitting into a cup formed by the tail end of the vertebra next in front (opisthocoelous vertebrae). Much later than the two longitudinal dorsal bands there appears on the ventral side an unpaired band in which appear metamerically repeated swellings of cartilage, likewise unpaired. These swellings become confluent, in a way similar to that which produced the dorsal bands, and form the unpaired ventral band of cartilage, the hypochordal cartilage of some authors. The swellings in this band, equivalent to the basi- ventralia, become semilunar in a transverse view, their horns tending upwards towards the basidorsal cartilages, but there is no actual meeting. Both dorsal and ventral elements are, however, joined together and form the chief portion of the ver- tebrae, owing to the rapidly proceeding calcification and later ossification of the all-surrounding “ membrana reuniens” or skeletogenous layer so far as that is not cartilaginous. Procoelous vertebrae exist in the overwhelming majority of Anura ; opisthocoelous are those of the Aglossa, the Discoglossidae, and of some Pelobatidae. The systematic value of this pro- or opistho-coelous character has been much exaggerated. We have seen that the centra of the vertebrae of the Anura are formed entirely by the interdorsal elements, hence the term “notocentrous,’ and these centra sometimes remain in adult specimens of Pelobates as separately ossified and calcified pieces, ZO ANURA CHAP, not fused with the rest of the vertebrae. This important dis- covery has been made by Boulenger, but Stannius had previously mentioned a specimen of Pe/obates in which the second and fourth vertebrae are biconvex, the third, sixth, and eighth bicon- cave. Moreover, since the sacral vertebra, generally the ninth, in all the Anura is invariably biconvex, the eighth being biconcave in the procoelous families, opisthocoelous lke the remaiing seven vertebrae in the other families, it is not difficult to imagine that in the Anura the production of pro- or opistho-coelous vertebrae depends simply upon the centra or articulating knobs happening to fuse either with the hind or the front end of the vertebrae. This must of course ultimately be determined by a mechanical problem of motion. A second type of the vertebrae amongst the Anura is the epichordal type, an exaggeration in degree of the notocentrous tendencies of the more usual perichordal arrangement. It shows, namely, the almost complete suppression of all the ventral cartilaginous elements, so that the chorda remains for a long time on the ventral surface of the axial column in the shape of a flattened longitudinal band. These two types are not un- connected. The suppression of the ventral elements applies most typically to the trunk region, while hypochordal cartilage exists in the anterior cervical vertebrae, and above all in the coccyx. Typically epichordal are the vertebrae of Pipa, Xeno- pus, Bombinator, Pelobates, Discoglossus and Alytes. It is significant that the epichordal often coincide with opisthocoelous vertebrae, and still more suggestive is the fact that Lombinator is eminently aquatic, Pipa and Yenopus entirely so, having lost the tympanum, at least externally. The epichordal feature is not necessarily indicative of- relationship. It has probably been developed independently in various groups, in correlation with a resumption of aquatic life. Various genera of Pelobatidae and most likely some Cystignathidae, e.g. Psewdis, will not improbably connect the two types and their several correlated features, for instance, the frequent reduction of the tympanic cavity. The os coceygeum has retained rather primitive features in so far as much dorsal and ventral cartilage is developed; but this has almost entirely lost its metameric arrangement, and the posterior half of the coceyx is formed chiefly by the ventral mass of cartilage, while the dorsal elements are more or less reduced. Il VERTEBRAL COLUMN 2] Only two vertebrae, generally the tenth and eleventh of the whole column, are clearly visible, each being composed of a pair of dorsal and a pair of ventral cartilaginous blocks. The sacral vertebra articulates with the coccyx by one or two convexities, but in the Aglossa, in some Pelobatidae, and a few others, the coccyx is fused with the sacral vertebra. Beyond the first and second component vertebrae of the embryonic coccyx, the cartilage is continued in the shape of two dorsal, and one ventral, bands, which soon fuse with each other. Dorsally this cartilage surrounds the spinal cord; the latter degenerates towards the end of the tadpole-stage, leaving, however, the empty spinal canal. The chorda, completely surrounded by cartilage, persists into the post-larval stage, but is destroyed Jong before the creature attains maturity. Ultimately the whole coccyx ossifies. The tail proper, namely that portion which is absorbed during the metamorphosis, remains throughout its existence in an apparently primitive condition. The chorda dorsalis and the spinal cord extend through its whole length, surrounded hy continuous connective tissue without any cartilage ; in fact it represents a piece of typical vertebral column before the appear- ance of cartilage. The reduction of this swimming organ begins at the hind end. The vertebral column of the adult—tThe first vertebra (we will call it the atlas since it carries the skull) is not, as in the Urodela, provided with an odontoid process. It articulates by two cups with the condyles of the occiput. In some Anura it co-ossifies, rather incompletely, with the second vertebra, regularly in the fossil Palaeobatrachus, often in Ceratophrys, Prevaiceps, and occasionally in SPelobates, Bufo, Rana, and Nenopus. This is, however, no justification for looking upon the first vertebra as a complex of two vertebrae, although the atlas is frequently very thick and broad, and even carries, in the Aglossa, considerable lateral wings or diapophyses. Those of the trunk-vertebrae are often very long, acting thereby as substitutes for ribs which are absent, except on the second, third, and fourth vertebrae of the Discoglossidae, and on the second and third of the Aglossa. In the adult Aglossa these ribs fuse with the processes which carry them. The diapophyses of the sacral vertebra carry no ribs, the ilia being attached to them directly. They are either cylindrical bo i) ANURA CHAP. as in the Ranidae and Cystignathidae, or they are more or less dilated as in all the other families, most strongly in the Pelobatidae and the Aglossa. In some members of the large sub-family of the Cystignathidae the otherwise cylindrical diapophyses are shghtly dilated. The sacrum is formed by the ninth vertebra, but there are a few interesting exceptions. Pelobates, Pipa, and Hymenochirus possess two sacral vertebrae; and, neglecting individual abnor- malities, these three genera form the only exception amongst recent Amphibia. In the three genera the coccyx is fused with the second sacral vertebra, and such a fusion occurs elsewhere normally only in Sombinator with its single sacral vertebra. The morphologically oldest condition is normally represented by Pelobates, the sacral vertebrae bemg the tenth and ninth. One Fic. 4.—Dorsal view of the sacral or ninth vertebra (9), with the attachment of the ilium, of (1) Rana temporaria, (2) Bufo vulgaris, showing the whole coccyx and pelvis, (3) Pelobates fuscus, as examples of cylindrical and of dilated sacral diapophyses. (About nat. size.) «, Acetabulum ; ¢, coecyx ; 7, ilium ; z, anterior zygapophyses. case has been recorded by Boulenger of Bombinator pachypus “with eleven segments,” the last carrying the ihum. Individual lop-sided abnormalities have been described in Bombinator and Alytes, where the right ium articulated with the tenth, the left ilium with the ninth vertebra. This shifting forwards of the ium to the extent of one metamere has been continued further in Pipa, in which the sacrum is formed by the ninth and eighth vertebrae, their diapophyses fusing on either side into extra broad wing-like expansions. In old specimens of Palacobatrachus fritschi the seventh vertebra is in a transitional condition, the ilium being carried by the ninth and eighth, and shghtly also by the diapophyses of the seventh vertebra; and in P. diluvianus the II VERTEBRAL COLUMN to w diapophyses of all these vertebrae are united into one broad plate to which the ilia are attached. Lastly, in Hymenochirus the first sacral is the sixth vertebra, and this creature has thereby reduced the pre-sacral vertebrae to the smallest number known. This shifting forwards of the ihac attachment implies the conversion of original trunk into sacral vertebrae, and the original sacral vertebra itself becomes ultimately added to the urostyle. The second sacral, the tenth of Pelobates, the ninth of Pipa, and the tenth on the right side of the abnormal Bombinator, are still in a transitional stage of conversion. In Discoglossidae the tenth is already a typical post-sacral vertebra, and is added to the coccyx, but it still retains distinct, though short, diapophyses. In the majority of the Anura the tenth vertebra has lost these processes, and its once separate nature is visible in young specimens only. In Sombinator even the eleventh vertebra is free during the larval stage. In fact the whole coccyx is the result of the fusion of about twelve or more vertebrae, which from behind forwards have lost thei im- dividuality. We ‘conclude that originally, in the early Anura, there was no coccyx, and that the ilium was. attached much farther back; and this condition, and the gradual shifting for- wards, supply an intelligible cause of the formation of an os coceygeum. The fact that the sacral vertebrae of the Anura possess no traces of ribs as carriers of the ilia, is also very suggestive. The ilia have shifted into a region, the vertebrae of which had already lost their ribs. By reconstructing the vertebral column of the Anura, by dissolving the coccyx into about a dozen vertebrae, so that originally, say the twenty-first vertebra carried the ilia, we bridge over the enormous gap which exists between the Anura and Urodela. That whole portion of the axial continuation behind the coceyx, more or less coinciding with the position of the vent, is the transitional tail. The disappearance of both notochord and spinal cord, and the conversion of the cartilaginous elements into a continuous rod in the case of the os coceygeum, find an analogy in the hinder portion of the tail of Dipnoi and Crossopterygii, and in the tail-end of most Urodela, portions which are not homologous with the os coccygeum. The term urostyle should be restricted to such and similar modifications of the tail-end, and this latter happens to be lost by the Anura during metamorphosis. 24 ANURA CHAP, Strictly speaking, or rather in anatomical parlance, the Vertebrate tail begins with the first post-sacral vertebra. In the Anura that portion of the whole tail has retained most cartilage, and has become the cocecygeum, which is required as a “backbone” for the often enormous belly. This require- ment is an outcome of the great shortening of the trunk proper Gf the trunk be defined as ending with the pelvic region), and this shortening of the trunk is again intimately connected with the jumping mechanism, enlargement of the hind-limbs, elongation of the iha, and throwing the fuleral attachment forwards as much as possible. The pre-acetabular ilio-sacral connection is varried to the extreme in the Anura. The shoulder-girdle and “sternum” are more complete than in the Urodela, there being also a pair of clavicles, fused with the precoracoidal bars. The whole apparatus presents two types. In the arciferous type the coracoids and precoracoids retain a great amount of cartilage in their distal portions, and these cartilages (the epicoracoids of some authors) overlap each other movably on one another, the right usually lying ventrally upon the left. The epicoracoidal cartilage of each side, by connecting the distal end of the coracoid with the precoracoid of the same side, forms an arc, hence “arciferous.” In the firmisternal type the epicoracoidal cartilages are much reduced, and, instead of overlapping, meet in the middle line and often fuse with each other, forming thereby a firm median bar, which connects the ventral ends of the precoracoids with those of the coracoids. This type is morphologically the higher and more recent, and passes in the larval stage through the arciferous condition. It is restricted to the Ranidae, Engystomatinae, and Aglossa. Although these two types afford an excellent distinctive char- acter for the main divisions of the Anura, they are to a certain extent connected by intermediate forms in such a way, that, for instance, in Bufo and among Cystignathidae in Ceratophrys, the two opposite epicoracoidal cartilages begin to unite at the anterior end. | In many Engystomatinae the precoracoids together with the clavicles are much reduced, sometimes to thin ligaments, being in this case mostly curved back and lying closely against the coracoids ; or they may be lost completely. Very rarely the precoracoidal bars are actually much stronger than the coracoids, “ SHOULDER-GIRDLE lo ww and the median symphysial bar of cartilage is lost; this is the case in Hemisus. The scapula is always large and curved into transverse, dorsally broadening blades, the dorsal greater portion of which the so-called supra-scapula, does not ossify but calcifies. It is very doubtful if the Anura possess a true sternum, if ? by sternum we understand a medio-ventral apparatus which owes its origin to the ventral portions of ribs. The so-called Fra. 5.—Ventral views of the shoulder-girdles of various Anura. (Slightly enlarged.) 1, Lombinator igneus, and 2, Bufo vulgaris, as examples of the arciferous type ; 3, adult, 4, metamorphosing Rana temporaria, showing change from the arciferous into the firmisternal type ; 5, Hemisus guttatum ; 6, Breviceps gibbosus ; 7, Cacopus systoma. (5, 6, 7, after Boulenger.) Cartilaginous parts are dotted ; ossified parts are left white. C7, Clavicle ; Co, coracoid ; #, epicoracoidal cartilage ; 7, humerus : M, metasternum ; O, omosternum; 7, precoracoid ; Sc, scapula; SS, supra- seapula, sternal apparatus of the Anura consists of two pieces. One, anterior, variously named episternum, presternum, or omosternum, rests upon the united precoracoids and extends headwards, being either styliform or broadened out. Sometimes it is partly ossified, with a distinct suture at its base; this is the case especially in the Firmisternia; in many Arcifera the omosternum remains ‘artilaginous and is continuous, without a sutural break, with the cartilage of the precoracoids, indicating thereby its genetic relation to the shoulder-girdle. Hence omosternwin is the 26 ANURA CHAP. preferable name. It is frequently much reduced, even absent, for imstance in most Bufonidae and in the Engystomatinae. The posterior so-called sternal part may be termed metasternwm. It forms the posterior counterpart of the omosternum. It is attached behind to the epicoracoidal cartilages, or fusing with them forms their posterior continuation. It appears mostly in the shape of a style, which is frequently ossified, and broadens out behind into a cartilaginous, partly calcified blade. In the Discoglossidae only it diverges backwards into two horns, assuming a striking resemblance to the typical xiphisternum of the Amniota. In young Anura the metasternal cartilage is intimately connected with the pericardium, an indication of its being derived not from ribs but from the shoulder-girdle. The glenoid cavity is always formed by the coracoids and by the scapula, but the precoracoid often takes part in its forma- tion, for instance in Bufonidae, Hylidae, and Discoglossidae. In the fore-limb the humerus has a crest, stronger in the males than in the females; it assumes extraordinary strength in some Cystignathidae, notably in the male Leptodactylus. Radius and ulna are fused into one bone. The carpalia are originally nine in number: radiale, ulnare, two centralia, and five carpalia distalia, the fifth of which is reduced to a tiny nodule or to a ligamentous vestige. The primitive condition still prevails in the Disco- vlossidae. In most of the other Anura the fourth and third distal carpalia, in any case very small, fuse with the enlarged ulnar centrale ; the radial centrale comes, in the Bufonidae and Pelobatidae, into contact with the radius, so that the forearm articulates with three elements as in the Urodela, but with this difference, that the mtermedium of the Urodela has been lost by the Anura. There are five metacarpalia and five fingers, but the elements of the first or thumb are nearly vestigial, so that the pollux is reduced to one or two nodules, scarcely visible externally. The normal munber of the phalanges of the second to fifth fmgers is 2, 2, 3,3. The distal phalanges are generally straight, either pointed or expanded or with Y or T-shaped ends ; but in the Hylidae, in Hylambates amongst the Ranidae, and in Ceratohyla, one of the Hemiphractinae, the terminal phalanges are produced into curved claws which support the adhesive finger-discs. There are, however, many genera of different families, which possess finger-dises and have no claw-shaped II PELVIC GIRDLE 2 / phalanges. The Hylidae, and many of the climbing members of the Ranidae with adhesive discs, possess an extra skeletal piece intercalated between the last and last but one phalanges of the fingers and toes. This piece, a mere interarticular cartilage in Hyla, is in the following Raninae developed into an additional phalanx, so that their numbers are 3, 3, 4, 4 in the hand and 3, 3, 4, 5, 4 im the foot: Cassina, Hylambates, Rappia, Mega- lizalus, Rhacophorus, Chiromantis, Ivalus, and Nyctiaalus. All the other Ranidae are without this additional phalanx, irrespec- tive of the presence or absence or size of digital expansions.' The pelvic girdle looks like a pair of tongs (see Fig. 4, p. 22). The ilium is enormously elongated and is movably attached to the sacral diapophyses. This connection is always pre-acetabular in position. The ilium and ischium co-ossify ¢om- pletely, and make up nearly the whole of the pelvis: the pubis is very small, and remains cartilaginous unless it calcifies. It rarely possesses a centre of ossification, for instance in Pelobates, where the osseous nodule is excluded from the acetabuluin, recalling certain Labyrinthodonta, whose ossa pubis likewise do not reach that cavity. The latter is open or perforated in young Anura and remains’ so in the Discoglossidae, but im the others it becomes closed up as in the Urodela. The ventral halves of the pelvis, besides forming a symphysis, closely approach each other, just leaving room for the passage of the rectum and the urmo-genital ducts. The hind-limbs are in all cases longer than the fore-linbs. The femur is slender, the tibia and fibula are fused into one bone. The tarsus is much modified by the great elongation of the two proximal tarsalia (there being no intermediuim) into an astragalus and a caleaneum, both of which fuse together distally and proximally, or completely as in Pe/odyfes ; in the latter case the limb assumes a unique appearance, since it consists of three successive and apparently single bars of nearly equal length. The other tarsal elements, especially the more lateral ones, are practically reduced to pads. The Anura have thereby acquired two well-marked joints, one cruro- tarsal, the other tarso inetatarsal; this shows a high stage of specialisation in com- parison with the Urodelous and Stegocephalous type of still undefined joints. 1 Boulenger, ?.7.S. 1888, p 204. 28 ANURA . CHAP. The Anura possesses five well-developed toes with normally 2, 2, 3, 4, and 3 phalanges, and the rudiments of a sixth digit, the so-called prehallux, which consists of from two to four pieces, including the one which represents its metatarsal. This prehallux, as a vestige of a once better developed digit, is exactly like the elements on the radial side of the wrist, which, we are certain, are the remnants of a once complete finger, namely the pollex. The only weighty difficulty against its interpreta- tion as a prehallux hes in the fact that hitherto no six-toed Stegocephali have been found; but the fact that there are no Stegocephali known with more than four fingers could be used as an argument against there being a pollex-vestige in recent Anura with just as little reason. The skull of the Anura differs from that of the other recent Amphibia in the following features :— The orbital region of the primitive cranium remains carti- laginous, but further forward the cranial cavity is closed by the unpaired sphenethmoid, which forms a ring round the anterior portion of the brain-cavity, hence called “os en ceinture” by some anatomists. The frontals and parietals fuse into one pair, of fronto-parietal bones, and these again can fuse together in the middle line ; as in Aglossa and Pelobates. The palatal portion of the palato-quadrate cartilage is complete, reaching forwards to the sides of the ethmoid region. The curved arch, formed by this cartilage, is covered by the following bones: (1) the quadrato- jugal, reduced to a thin splint which connects the quadrate and squamosal with the posterior end of the maxilla; (2) the ptery- void, always strong, extending from the distal inner corner of the quadrate to the maxilla, sometimes also to the palatine, and with a broad, median process to the parasphenoid, this process covering ventrally most of the otic region; (3) the palatines, which vary considerably in shape and size; they are placed transversely and meet in the middle line: in Bombinator and Pelodytes they are absent. The quadrates are directed transversely and backwards, in conformity with the wide gape of the mouth. The squamosal is always well developed, covering the whole of the quadrate on its outer side; it has a forwardly directed process which ends freely in Rana, meets a corresponding process of the maxilla and forms a bony arch with it in Discoglossus, Pelobates, and others, or ll SKULL 209 is scarcely developed at all, for instance in Bufo. In Pelobutes cultripes the squamosal is very wide and forms a junction with the fronto-parietals, thus producing a broad bridge across the temporal fossa. The nasal bones are large and meet in the middle line. Frequently they leave a space between them and the diverging anterior portion of the fronto-parietals, through which gap appears part of the dorsal surface of the ethmoid cartilage. A fontanelle between the frontals occurs in most Hylidae, many Cystignathidae, some few Bufonidae, in Pelodytes amongst the Pelobatidae, and in the Discoglossidae. The tympanic cavity is bordered in front, above, and below by the squamosal and quadrate, behind by the musculus depressor mandibulae, internally by the otic capsule, and by the cartilage of the cranium between this and the lateral occipital bone. The cavity communicates, however, by the wide and_ short Eustachian tube with the mouth, the passage being bordered anteriorly by the pterygoid, posteriorly by soft parts. Partly imbedded in these soft tissues is the styloid process or stylohyal, which is attached to the cranium, mostly behind the otic region, and is continued downwards into the anterior horn of the hyoid. The whole partly cartilaginous, ligamentous, and osseous string is, in fact, the entire ventral half of the hyoid arch, while the dorsal half or hyomandibular portion of this, the second visceral arch, is modified into the columellar or auditory chain. The inner end of this chain, the stapes, is inserted into and around the fenestra ovalis of the otic capsule, while the outer end is somewhat T-shaped, and is loosely attached to or near the upper rim of the tympanic ring and to the middle of the tympanic disc. In many Anura this terminal bar can be seen from the outside. The middle portion of the columellar chain is ossified, the rest remains cartilaginous. But the whole chain exhibits various modifications in different genera, especially in the number and the extent of the processes sent out by the outer cartilaginous portion; these are attached in various ways to the tympanum and its rims. The tympanic disc is carried by a cartilaginous ring, which rests against a special process sent out by the quadrate, and is probably itself a differentiation of this element. In some very aquatic genera the whole tympanic cavity 1s 30 ANURA CHAP. much reduced, for instance in Pelobates, Bombinator, Liopelma. In Batrachophrynus not only the cavity, but also the Eustachian tubes are suppressed. Ih the Aglossa only the two tubes are united into one short but wide median canal, opening at the level of the pterygoids on the roof of the mouth. The lower jaw is remarkable for the possession of mento- Meckelian cartilages, absent only in the Aglossa and Disco- glossidae. At first they are much longer than the rest of the jaw; during the larval hfe they indeed form the functional jaw, and they are now covered with horny sheaths instead of teeth. Owing to the absence of teeth on them, these mento- Meckehian cartilages are later not invested by bone, although in many Anura they ultimately ossify, either retaining their sepa- rate nature or fusing partly with the dentary bones. The bulk of the lower jaw, the Meckelian cartilage, becomes invested by the dentary, a small articulare, and an inner angulare, while a splenial element is absent. The dentary itself is mostly reduced to a small dentigerous splint, while the angulare forms by far the greater part of the bony jaw. Teeth are more restricted in their occurrence than in the Urodela. On the jaws they always stand in one row. With the exception of the Hemiphractinae, Amphignathodontinae, ‘Ceratobatrachinae, and Genyophryninae, no recent Anura carry teeth on the lower jaw, and even in these genera they are mostly much reduced in size and firmness, having all the appearance of vanishing structures. The premaxillae and maxillae are frequently furnished with teeth, except in the Dendrobatinae, Genyophry- ninae, Engystomatinae, Dendrophryniscinae, Bufonidae, Pipa, and Hymenochirus. The vomers mostly carry a series of teeth on their posterior border; when these teeth are absent, as In many species of Bufo, a kind of substitute sometimes occurs on the palatines in the shape of a row of tuberosities. The palatines carry teeth in Hemiphractinae. The parasphenoids are toothed in Triprion and Diaglena, and occasionally in Pelobates cultripes. A few Anura possess peculiar substitutes for teeth in the anterior portion of the lower jaw, namely, a pair of conical bony processes, sometimes rather long, but always covered by the dense gums, or investment of the jaws; eg. Lepidobatrachus, several Rana, e.g. R. adspersu, R. khasiana, R. kuhli, and Cryptotis bre vis. II SKIN o>) Cranial dermal ossifications are developed in some species of Bufo, still more in the Hemiphractinae, and above all in /’e/o- hates cultripes and in the Cystignathoid genus Calyptocephalus. The hyoid apparatus of the Anura is complicated. It is originally composed of the hyoidean and four branchial arches, with one median, copular piece. The branchial arches form in the early life of the tadpole the elaborate framework of the filtering apparatus mentioned on p. 44. During metamorphosis the whole filter disappears, owing to resorption of the greater part of the branchial arches; only their median portions remain, and fuse with the enlarged copular piece and the hyoidean arches into a broad shield-shaped cartilage (corpus linguae), whence several lateral processes sprout out, the posterior pair of which are generally called thyrohyals or thyroid horns. The true hyoid horns give up their larval lean-to articulation with the quadrate, become greatly elongated, and gain a new attach- ment on the otic region of the cranium. The transformation of the whole apparatus has been studied minutely by Ridewood, in Pelodytes punctatus.’ SKIN The epidermis of the young larvae of Amphibia is furnished with cilia, which later on are suppressed by the development of a thin hyaline layer or cuticula, but clusters of such cilia remain, at least during the larval life and during the periodical aquatic life of the adult, in the epidermal sense-organs. In the frog, currents are set up by the ciliary action at an earlier stage, and are maintained to a later stage than in the newt. In the latter the tail loses its ciliation, whereas in the frog it remains active almost up to the time of the metamorphosis. In tadpoles of 3-10 mm. nearly the whole surface is ciliated (Assheton). The cilia work from head to tail, causing the little animal, when perfectly quiet, to move forwards slowly in the water. Beneath the cuticula, in the Perennibranchiata and the larvae of the other Urodela, lies a somewhat thicker layer of vertically striated cells, the so-called pseudo-cuticula, which disappears with the transformation of the upper layers of the Malpighian cells into the stratum corneum. The latter is very thin, consists of one or two layers of flattened cells, and is shed periodically by all 1 P.Z.S. 1897, p. 577. 2 0.7. M.S. xxxviii. 1896, p. 465. to AMPHIBIA CHAP. Amphibia in one piece. In the Urodela it generally breaks loose around the mouth, and the animal slips out of the delicate, transparent, colourless “shirt,” which during this process of ecdysis or moulting becomes inverted. In the Anura it mostly breaks along the middle line of the back, the creature struggles out of it, pokes it into its mouth, and swallows it. Urodela also eat this skin. As a rule the first ecdysis takes place towards the end of the metamorphosis, preparatory to terrestrial life. So long as the animal grows rapidly, the skin has to be shed frequently, since this corneous layer is practically dead and unyielding. Adult terrestrial Urodela do not seem to moult often, mostly only when they take to the water in the breeding season.