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Lay fi) b rat ah Canina dy Coady Tie i aren : el AB (Gla ty | hee deen ie tatuingl habe od RN UR aNG inet sea i we bat Daa a ae eels Hoe Beane Ay a ee ni a pote yi Cala oh 1 Si Be ila ie idan ft, yh iy 2 aa peice [eater onde Zi ames be: ariel tg aie Avis elohe is ae ‘ ie lei sy eed % e : en iid ee peitar te! rele itr liarrckghesth ple e re gagethe nena koe tet cbr os enge, cera nates ee nD atrnes ae a tk aeesinnoupet ot a tsi ae j Petite er eeimtig dite peut ey A Hae : nop ee ( bert co tote 4 yy at delacerehG} fepies Hea ea Ree : Bipiiditaiabir rhs cor Maokanbel gab pee elas ah Hehe i Wa is oid key edie hi ieeuibtr: Tt BMS eee obs ha Uoiaesentie Saag in Wait te poser iE pasar ee rapt oe ‘ yi IMAG BIBL SR acptDenie pena arene ae ain hfe nt r ie et Pah 7 at tone fe ei toe Moly sti i Stier che Ferrie cite o Rises Aelia renee Wee Herne i es later rate apenas rs f ead oa ea liane aunt eetn ates ipyiat shea ny bi su Sble aie mie He fy os " oe nisi Hi ah i i, oe zr CORN EIPE INT aI LIBRARY BOUGHT WITH THE INCOME OF THE SAGE ENDOWMENT FUND GIVEN IN 1891 BY HENRY WILLIAMS SAGE Corne! 43.C17 1 Cambridge natural histor ini Vi r DATE DUE oF 25 65 Mp DET jo wore = "ae 10 Mm GAYLORD Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924024535506 THE CAMBRIDGE NATURAL 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 “SATMId AY NV VWIGIHdWY JO NOILNEIYLSIAG TVvOlHdVH9049 FHL ONILO 344 Q1YOM AHL AO SAYNLW3AA TVOISAHd UePUoT. FOF, 60H GPLGPEMS * : AORN 3 08 Ea or at o HALI (p. ca epondel ISSAM- PHIBIA (p. 84) | (p. 81) Stegoce- phali Stereo- \ spondyli (p. 83) Apoda (p. 84) Urodela (p. 94) AGLOSSA (p. 143). Anura | P HANERO- (p- 188) | Grossa (p. 152) Sub-Order. , Stegoce- ( BRANCHIO- SAURI(p. 80). Family. Sub-Family. phali Lepo- | spondyli ete ten (p. 80) (p. 81). Stegoce- CoECILIIDAE (p.89). AMPHIUMIDAE (p. 97). (ae nathinae (p. 102). SALAMANDRIDAE | Plethodontinae (p. 103). (p. 102) Amblystomatinae (p. 109). eee dna (p. 115). PROTEIDAE (p. 182). SIRENIDAE (p. 136). DIscoGLOssIDAE (p. 152). PELOBATIDAE (p. 160). BUFONIDAE (p. 166). { Amphignathodontinae IIyLIDAE (p. 185) (p. 188). Hylinae (p. 189). Hemiphractinae (p. 210). CYSTIGNATHIDAE i Cystignathinae (p. 211). (p. 209) | Dendrophryniscinae (p. 224). ' ern d , { Engystomatinae (p. 225). peansenee Dyscophinae (p. 235). 2 Genyophryninae (p. 236). Ceratobatrachinae (p. 237). Raninae (p. 238). Dendrobatinae (272). RANIDAE (p. 237) XIl SCHEME OF CLASSIFICATION CLASS REPTILIA (p. 277). PROREPTILIA (p. 285). Eryops (p. 286). Cricotus (p. 287). Sub-Class. Order. Sub-Order Family. Microsauri (}). 288). i i [Bestest f PRrororosauRi (p. 290). Ys ) | (p. 290) \ RuyNCHOCEPHALI (p. 292). Pareiasauri (}). 304). araepHA | Theriodontia (p. 306). (p. 300) Anomodontia (p. 309). ly | Placodontia (p. 311). ( Atheca (p. 333) SPHARGIDAE (p. 833). CHELYDRIDAE (p. 338). DERMATEMYDIDAE (p. 341). CRYPTODIRA CINOSTERNIDAE (p. 342). (p. 338) PLATYSTERNIDAE (p. 845). CHELONIA TESTUDINIDAE (p. 345). (p. 312) CHELONIDAE (p. 378). eee Paaeeenws eee se HELYDIDAE (p. 399). Kp 888) | CARETTOCHELYDIDAE (p. 404). TRIONYCHOIDEA TRIONYCHIDAE \ (p. 404) (p. 404). ( Sauropoda (p. 418). Theropoda (p. 420). STEGOSAURI DINOSAURIA | (p. 425). (p. 412) Orthopoda ORNITHOPODA (p. 424) (p. 426) Ceratopsia L (p. 430). Pseudosuchia (p. 432). Parasuchia (p. 433). . TELEOSAURIDAE (p. 450). CROCODILIA oe (431) \ Eusuchia(}. 434) . GAVIALIDAE (p. 451). ities ATOPOSAURIDAE (p. 453). GONIOPHOLIDAE (p. 453). CrocopILipak (p. 454). Nothosauri f Mesosavnipas (p. 476). PLESIO- (p. 476) \ Nornosaunrripas (p. 477). SAURIA Plesiosauri { Putosaunipar (p. 477). (p. 473 (p. 477) PLESIOSAURIDAE (p. 478). = | ELASMOSAURIDAE (p. 478). green Ichthyosauri (p. 478) (p. 483). PLrERODACTYLI ae " Pterosauri [ (p. 486). (yp. 484) (p. 486) PLERANODONTES ue : ; (p. 487). PYTHONO.- fl Dolichosauri (p. 489). eae Mosasauri (p. 489). SCHEME OF CLASSIFICATION Xili Sub-Class. Order. Lacertilia (p. 491) Ophidia (p. 581) Sub-Order. GECKONES (p. 502) LACERTAE (p. 518) | CHAMAELEON- TRS (p. 567) Family. Sub-Family. ‘ Geckoninae (p. 507). GECKONIDAE | Eublepharinae (p. 507) (p. 512). 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 (). 549). GERRHOSAURIDAE (p. 559). SCINCIDAE (p. 559). ANELYTROPIDAE (p. 564). DIBAMIDAE (p. 564). ANIELLIDAE (p. 564). AMPHISBAENIDAE (p. 565). PyYGOPODIDAE (p. 567). { CHamarceosrian (p. 578). TYPHLOPIDAE (p. 598). GLAUCONIIDAE (p. 594). ILYsIIDAE (p. 594). UROPELTIDAE (p. ae 5 ’ Pythoninae (}. 598). Borpas (p. 596) Bhince (p. ol), XENOPELTIDAE (p. 605). Acrochordinae (p. 606). ects Guinbrnse (p. 607). € At ) | Rhachiodontinae co (p. 622). = Dipsadomorphinae = Opistho- a? 628). << tee eee E ey pha (p. 625) @ (pe G25) | atin = (p. 625 = | Protero- Elapinae (p. 626). ALS oe ee (p. 625) (p. 635). AMBLYCE- PHALIDAE (p. 637). VIPERIDAE { Viperinae (p. 638). (p. 637) | Crotalinae (p. 644). PART I AMPHIBIA VOL. VII £ ““’s scheint, dass die hier oben keine Ahnung haben von dem Sumpf und Seiner Pracht.” The ‘‘ plattgedriickte Krote,”’ SCHEFFEL’s J'rompeter von Sékkingen. CHAPTER I AMPHIBIA CHARACTERS AND DEFINITION——POSITION OF THE CLASS AMPHIBIA IN THE PHYLUM VERTEBRATA—HISTORICAL ACCOUNT OF THE CLASSIFICATION OF AMPHIBIA «\ Birp is known by its feathers, 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 URopeEva or tailed two- or four-footed newts, and about 900 ANuRA, or tailless, four-footed frogs and toads; in all some 1000 different species. Yew, indeed, in comparison with the 2700 Mammals, 3500 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 vlobe, 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 like fairy-tales. Characters of the Amphibia.' 1. The vertebrae are (a) acentrous, (b) pseudocentrous, or (c) notocentrous. 2. 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 () divided into two atria and one ventricle, and (h) it has a conus provided with valves. 7. 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. None of these characters is absolutely diagnostic, except 1 (c), and this applies only to the Anura and most of the Stegocephali. 1 References to explanations of the terms used below will be found in the index. I CHARACTERS AND POSITION 5 Nunbers 1 (0), 1 (c), 2, 3, 4 and 12 separate the Amphibia from the Fishes. Numbers 1, 6 (6), 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 (excl. Dipnoi), Birds and Mammals. We can, therefore, very easily define 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 Animnia 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 innova- tion when Huxley brigaded them with the Fishes as Ichthyopsida, thereby separating them more from the Sawropsida (= Reptilia and Aves), than is justifiable-—perhaps moré 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 lived countless creatures which were a “rudis indigestaque moles,” neither Amphibia nor Reptilia, in the present intensified sense of the systematist. The samme consideration applies equally to the line which leads downwards to the Fishes. But the great gulf within the Vertebrata lies 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- pterygii 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, in 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 Salamundra 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, everi in the 13th edition (1767), stands as follows :— 1. Reprines pEpatt, with the four “genera” Testudo, Draco, Lacerta, and Rana. Lacerta includes Crocodiles, Lizards, and Newts ! 2, SERPENTES APODES. 3. Nanves prnnati. Elasmobranchs, Sturgeons, Lampreys, and various other fishes. Laurenti, 1768, in a dissertation entitled “Specimen medicum, exhibens Synopsin Reptilium uses Brisson’s term, Reprinus, and divides them into :— REPTILIA SALIENTIA, these are the Anura. GRADIENTIA, namely the Urodela and Lizards. SERPENTIA, the Snakes and the Apoda. Brongniart, 1800, “ Essay Vune classification naturelle des Reptiles,” ! dis- tinguishes :-— CHELONI, Sauri, OPHIDI, BatRacuit; the last for the Frogs, Toads, and Newts. Latreille, 1804, “ Nouveau Dict. Hist. Nat.” xxiv.,? accepts the four Orders of Brongniart’s “Reptiles,” but clearly separates the fourth Order, “Barracull,” from the rest by the following, now time-honoured, diagnosis: Doigts des pattes wayant pas @ongles; des branches, du moins pendant un 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 Ecavupati and Caupati; he also introduces the terms “ ANOURES” and “ Uropkies” 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 Apopa for the Coeciliae, and recognises their affinity to the Ecaudata and Caudata by removing them from the Snakes. De Blainville, 1816, “Prodrome d’une nouvelle distribution du régne animal ” ?— AMPHIBIENS SQUAMIFERES. [The Reptilia.] NUDIPELLIFHRES s. Ichthyoides. [The Amphibia. ] ” 1 Bull. Soc. Philom, ii. p. 81. 2 Tableaux méthodiques, p. 61. 3 Bull. Soc. Philom. p. 113. 8 AMPHIBIA CHAP. Merrem, 1820, “ Tentamen systematis Amphibiorum.” Puourpora. [The Reptilia.] Batracuia: APODA. SALIENTIA. Mutabilia [with metamorphosis, eg. Newts.] eee eee Amphipneusta [Perennibranchiate Uro- deles. ] F.S. Leuckart, 1821, “ Einiges ueber die fischartigen Amphibien.” ! Monopnoa. [The Reptilia.] with temporary gills: Ecaudata + Caudata ie t. Peeve Leyla with permanent gills: ‘“ Proteidae,” Meno- poma and Amphiuma. Latreille, 1825, “ Familles naturelles du régne 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 :— : Reprinia. Still including the Coeciliae amongst the Snakes. Amputera / Caducibranchiata. \ Perennibranchiata. PISCES. Wagler, 1830, “Systema Amphibiorun.” TESTUDINES, CrocopiLI, LACERTAE, SERPENTES, ANGUES, COECILIAE, Rawnag, IcHrHyop1. Ranaz IL. AGLOSSA. 5 Il. PHANEROGLOSSA: 1. Cauda nulla. [The Anura.] ss “ 2. Cauda distincta. [The Sala- mandridae. ] Icutayopr |. ABRANCHIALES. Menopoma [Cryptobranchus] and Amphiwma. 33 Ul. BRANCHIALES. [The Perennibranchiate Urodela. ] J. Miller, 1831, “ Beitrage zur Anatomie... der Amphibien.” 2 GyMNopHIonA, DeRoTREMATA, PROTEIDAR, SALAMANDRINA, Bar- RACHIA. J. Bell, 1836, Todd’s “Cyclopaedia of Anatomy and Physiology,’ Art. * Amphibia.” AnpHipNgustA, the Perennibranchiate Uvrodeles ; ANOURA, URODELA ; ABRANCHIA, Menopoma and Amphiuma ; Avopa. Stannius, 1856, “Handbuch der Zootomie: Anatomie der Wirbelthiere.” (2nd ed.) AmpHIBIA Monopnoa. The Reptilia. AwpuHipia Dipnoa. 1, URopELA. PERENNIBRANCHIAT A. DEROTREMATA: Amphiuma and Menopoma. MYCTODERAS 1 Jsis, 1821. * Treviranus’ Zeitschr, f. Physiol. 1831, p. 190. * Gépn, neck ; pw, close. I CLASSIFICATION 9 2. Barracuta. AGLOSSA. PHANEROGLOSSA: Systomata = Engystomatidae. Butoninae. Without manubriwn sterni, Raninae. With manubrium. Hyloidea. With adhesive finger- discs, GYMNOPHIONA., Gegenbaur, 1859, “ Grundzuge der vergleichenden Anatomie,” AMPHIBIA as a separate class, equivalent to that of the Reprivia, are divided into the four Orders : PERENNIBRANCHIATA, SAL A- 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. SavROIDs, subsequently changed into Sauropsipa = Reptilia + Aves. IcHTHYOIDs, 55 $3 IcaTHyorsipA = Amphibia + Pisces. Haeckel, 1866, “ Generelle Morphologie.” Amphibia. A. Paractamputpra s. Ganocephala = Labyrinthodonta + Peromela [Apoda]. B, Lissampuipta s. Sozobranchia = Sozura [Urodela] + Anura. Cope, 1869.1 STEGOCEPHALI, GyYMNoPHIDIA, UrRopELA, PRrorerpra, TRACHYSToMaATA, ANURA. Huxley, 1871, “A Manual of the Anatomy of Vertebrated Animals.” Amphibia I. Savropatracuta [v.d. Hoeven’s term] s. URoprna 1. Proteidea. 2, Salamandridae. II. LasyrintHoponta. III. Gymnopuiona, IV. Batracuia s. ANURA. Boulenger, 1882, “ Catalogue of the BarRACHTA GRADIENTIA s. CAUDATA and Batracuta ApoDA,” divides the Caudata simply into: SALAMAND- RIDAE, AMPHIUMIDAE, PROTEIDAE, and SIRENIDAL. 1882, “ Cat. Batrachia Salientia s. Ecaudata,” see p. 140. Cope, 1890, “Synopsis of the Families of Vertebrata.” 2 Cuass BatRACcHIA. Sub-Class I. SrEGocEPHALI. Order 1. Ganocephali: Trimerorhachis, Archegosaurus, 2. Rhachitomi: Eryops 3. Embolomeri. Cricotus. 4. Microsauri: Branchiosaurus, Hylonomus, ete. 1 Proc. Ae, Philad. p. 209, 2 Americ. Natural. xxiii. p. 849. ie) AMPHIBIA CHAP. I Sub-Class IT. Uropzta. Order 1. Proteidae : Proteus. 2. Pseudosauria. [AJl the rest of the Urodela + Coeciliidae. ] 3. Trachystomata: Sirenidae. IIL. Sanrenrra. P. and F, Sarasin, 1890, “Zur Entwicklungsgeschichte der Ceylonesischen Blindwiihle, Ichthyophis glutinosa.” 4 Sub-Class I. ARCHAEOBATRACHI 8. STEGOCEPHALI. II. Neopatracut. Order 1. URODELA. a. Salamandroidea. [The Urodela.] b. Coeciloidea = Amphiumidae + Coeciliidae. 2. ANURA. : The classification adopted in this volume is as follows :-— Crass AMPHIBIA. Suh-Class I. Phractamphibhia. Order I. Stegocephali Lepospondyli. Sub-order 1. Branchiosauri. Sub-order 2. Aistopodes. Order II. Stegocephali Temnospondyli. Order III. Stegocephali Stereospondyli. Sub-Class TT. Lissamphibia. Order I. Apoda. Order IL. Urodela. Order ITI. Anura. Sub-order 1. Aglossa. Sub-order 2. Phaneroglossa. 1 Sarasins’ Ergebnisse Ceylon, 1887-1890. CHAPTER II SKELETON OF URODELA AND ANURA—SKIN—COLOUR- CHANGING MECHANISM — POISON -GLANDS—-SPINAL NERVES——RESPIRA- TORY ORGANS——SUPPRESSION OF LUNGS——URINO -GENITAL ORGANS 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 Amphiuma. In the following table the sacral vertebra is included in those of the trunk. Trunk. Tail. Siren lacertina . 22 35 + Necturus maculatus 19 29 Proteus anguinus ; 30 28 + Cryptobranchus ailleghantuiints 20 or 21 244 C. scheuchzert —. 21 C. japonicus ‘ , 22 22 to 26 -lmphiuma means 63 BA + Amblystoma tigrinum 17 or 16 32+ Nalamandru maculosa . 17 a7 Triton cristatus . 17 36 Triton taeniatus . 14 or 15 36 + Triton palmatus . 2 14 23 to 25 Salamandrina persprcillate 15 32 to 42 Spelerpes fuseus : . 16 23 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. I2 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 joint, 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 basidorsalia 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 chietly 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 Loe) ventralia we have to distinguish between the trunk and the tail. In the latter they produce a pair of ventral outgrowths or haemapophyses, which ultimately 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 Fic. 1.—1-5, Five successive stages of the development of a caudal vertebra of a newt; 6-7, the second and the first cervical ver- tebra of Cryptobranchus ; 8-9, side view of the constituent cartilaginous blocks of a caudal vertebra (8) and a trunk-ver- tebra (9) of Archeyosaurus as typical examples of Temno- 7 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 ; B.V, basiventral piece or ven- tral arch ; Ch, chorda dorsalis, or notochord ; /.D, interdorsal piece ; /.V’, interventral piece ; I_V.L, intervertebral ligament ; N, spinal nerve—these are num- bered I, II, IIT in 6 and7; R, rib; 7, in 7, rib-like tubercle on the first vertebra. 1 2 3 Bp oN _ 8p WV BY 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 Z’riton 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. 14 URODELA 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- trank vertebra of a larva of Swa- tebral artery, which still indi- mandra maculosa, enlarged. The right side shows the actually existing state, cates the true foramen trans- attachments are restored to their pro, YexSarium. ‘The homologies of bable original condition. A, Verte- these parts are still more ob- canal B.V,remantofthebasiventral Scured by the fact that a new cartilage ; Ch, chorda dorsalis; Sp.c, process grows out from the rib, une canal; *, the false transverse 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 rib-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 Il LIMB-GIRDLES 15 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 Stren. 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 ulnar 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. Svren has four or three fingers; Proteus 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 ilo-sacral connection is acetabular in its position, 7.¢. it lies 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 (Necturus) 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 toes, with 2, 2, 3, 3, 2 phalanges respectively. Concrescence of the tarsalia applies most frequently to the fourth and fifth distal 16 URODELA CHAP. and to the two centralia; exceptional, for instance, in Crypto- branchus 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 Amphiuma 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, Amphiwma, and Cryptobranchus alleghaniensis. The whole branchial apparatus is reduced to three pairs of arches in Necturus and Proteus, to two in the adult Crypto- hranchus 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 he 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 eartilage 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 Amphiwma, Necturus, Proteus, and Siren. The lacrymalia are still separate in some Amblystomatinae, Pm 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; Cy, Cy, outer and inner occipital con- dyles ; Ch, choana or posterior nasal opening ; d, dentary ; £, ethmoid; /, frontal; LO, lateral occipital ; 1/, maxillary ; N,nasal ; No,nostril ; OS, orbito- sphenoid ; P, parietal ; P/, pre- frontal ; Pl, palatine ; Pm, pre- maxillary; Po, prootic; PS, parasphenoid; Pt, pterygoid; Q, quadrate ; S, angulo-splenial ; Sq, squamosal ; St, stapes; Vo, vomer ; II, VII, X, exits of the optic, facial, and glosso- vagus nerves. eg. Ranidens and Hynobivs. A pair of nasalia are generally present, but are absent in Necturus, Proteus, and Siren. The parasphenoid is* furnished with teeth in the Plethodontinae and Desmognathinae. Separate palatine bones exist in Mectwrus 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 G 18 ANURA CHAP, The pterygoid bones are most fully developed, so as to reach the vomero-palatines, in the Amblystomatinae, in Nectwrus, 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 Veeturus, Proteus, and Niven, 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 (Sdlamandrina, Triton), mostly ligamentous ;—apparently a reminiscence of the Stegocephalous condition. The two pre- maxillary bones are liable to fuse into one, for instance in Cryptobranchus, generally in adult Tritons. They are most reduced, and are toothless, in Stren. The two maxillary bones are absent only in Werturus, Proteus, Typhlomolge, and Siren. Their posterior end is frequently free, loosely connected by ligaments with the pterygoid in Crypto- branchus ; oy with the distal portion of the quadrate, and in this case either just touching it (7'ylototriton), 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 Stren ; in others only during the larval period. There are no mento-Meckelian elements. SKELETON OF THE ANURA The vertebral column.—The distinctive peculiarities of the vertebrae of the Anura are that they are notocentrous, and that about a dozen of them are modified and fused into an os coceygeum. 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. Paired cartilages appear on the dorsal side of the thin chordal sheath, and whilst tending to enclose the spinal cord in a iW THE DEVELOPING VERTEBRAL COLUMN 19 canal, their bases grow head- and tail-wards into what will ultimately become the intervertebral region. This extension of eartilave leads to a fusion with that of the next following pair of arches, so that the axial column at this carly stage consists of avight and left longitudinal ridge of cartilage which sends off’ dorsal processes, neural arches, in metameric succession. 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, Hyla). We recognise 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 dise 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 land 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 vir- 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, 20 ANURA CHAR: 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 Pelobates 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 like the remaining 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 Bombinator 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 heen developed independently in various groups, in correlation with a resumption of aquatic life. Various genera of Pelobatidae and inost likely some Cystignathidae, e.g. Pseudis, 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 coccyx is formed chiefly by the ventral mass of cartilage, while the dorsal elements are more or less reduced. I VERTEBRAL COLUMN 21 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 long 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 by 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 Ceratuphrys, Dreviceps, and occasionally in Pelobates, Bufo, Rana, and Aenopus. 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 a2 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 slightly dilated. The sacrum is formed by the ninth vertebra, but there are a few interesting exceptions. Pelobates, Pipu, 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 Bombinetor with its single sacral vertebra. The morphologically oldest condition is normally represented by Pelohates, the sacral vertebrae being the tenth and ninth. One Hs eS Fra. 4.—-Dorsal view of the sacral or ninth vertebra (9), with the attachment of the ilinm, ol (1) Rana temporaria, (2) Bufo vulgaris, showing the whole coccyx and pelvis, (3) Prlobutes fuscus, as examples of cylindrical and of dilated sacral diapophyses. (About nat. size.) «, Acetabulum ; ¢, coccyx ; /, ilinm ; -, anterior zygapophyses. case has been recorded by Boulenger of Sombinator pachypus “with eleven seements,” the last carrying the ilium. Individual lop-sided abnormalities have been described in Lombinator and Alytes, where the vight ilium articulated with the tenth, the left ium with the ninth vertebra. This shifting forwards of the iliuim to the extent of one metamere has been continued further in Pipe, in which the sacrum is formed by the ninth and eighth vertebrae, their diapoplyses fusing on either side into extra broad wing-like expansions. In old specimens of Pulacobatrachus fritscht the seventh vertebra is in a transitional condition, the ilium being carried by the ninth and eighth, and slightly also by the diapophyses of the seventh vertebra; and in P. dilurianus the Ir VERTEBRAL COLUMN 23 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 iliac 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 Lombinator even the eleventh vertebra is free during the larval stage. In fact the whole coceyx is the result of the fusion of about twelve or more vertebrae, which from behind forwards have lost their in- dividuality. We conclude that originally, in the early Anura, there was no coccyx, and that the illum was attached much farther back; and this condition, and the gradual shifting for- wards, supply an intelligible cause of the formation of an os coccygeum. The fact that the sacral vertebrae of the Anura possess no traces of ribs as carriers of the ila, 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 coceyx 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 coccyx, 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 coccygeum, 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 coceygeum, 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 (if 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 ilia, and throwing the fulcral attachment forwards as much as possible. The pre-acetabular ilio-sacral connection is carried 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 hegin 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, > re SHLOULDER-GIRDLE 25 and the median symphysial bar of cartilage is lost; this is the case In Heamisis. 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 é Pic. 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, Cucopus systoma. (5,6, 7, after Boulenger.) Cartilaginous parts are dotted ; ossified parts are left white. C/, Clavicle ; Co, coracoid ; Z, epicoracoidal cartilage ; 4, humerus ; J/, metasternum ; O, omosternum ; /’, precoracoid ; Se, scapula; S.S, 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 omosternwin remains cartilaginous and is continuous, without a sutural break, with the cartilage of the precoracoids, indicating thereby its genetic relation to the shoulder-girdle. Hence omosternwm is the 26 ANURA CHAP. preferable name. It is frequently much reduced, even absent, for instance 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, assuining a striking resemblance to the typical xiphisternum of the Amniota. In young Anura the metasternal cartilage is intimately connected with the pericardium, au 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 Leptoductylus. Radius and wna are fused into one bone. The carpalia are originally uine in number : radiale, ulnare, two centrala, 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 vase 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 eleinents as in the Urodela, but with this difference, that the intermedium 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 number of the phalanges of the second to fifth fmgers is 2, 2,5, 3. The distal phalanges are generally straight, either pointed or expanded or with Y or T-shaped ends; but in the Hylidae, in Hy/ambates amongst the Ranidae, and in Verutohyla, 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 tinger-discs and have no claw-shaped II PELVIC GIRDLE 27. phalanges. The Hylidae, and many of the climbing members of the Ranidae with adhesive discs, possess an extra skeletal rece 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 in the foot: Cassinu, Hylambates, Ruppia, Meya- livalus, Rhacophorus, Chiromantis, Ivzalus, and Nyetiaalus, 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 Vig. 4, p. 22). The ilimn is enormously elongated and is movably attached to the sacral diapophyses. This connection is always pre-acetabular in position. The ilium and ischium co-ossity com- 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 Pelobutes, where the osseous nodule is excluded from the acetabulum, 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 in 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 urino-genital ducts. The hind-limbs are in all cases longer than the fore-limbs. 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 intermedium) into an astragalus and a caleaneum, both of which fuse together distally and proximally, or completely as in Pe/odytes; 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 eruro - tarsal, the other tarse- inetatarsal; this shows a high stage of specialisation in com- parison with the Urodelous and Stevocephalous type of still undefined joints. 1 Boulenger, 2.7.8. 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 lke 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 lies 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 ypollex-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 sphenethinoid, 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 /’e/obates. 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 hy 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- goid, 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 Sombinator 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 Aen, meets a corresponding process of the maxilla and forms a bony arch with it in Discoglossus, Pelobates, and others, or $s SKULL 29 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 hy 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, igamentous, 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 is 30 ANURA CHAP, much reduced, for instance in Pelobates, Bombinator, Liopelma. In Batrachophrynus not only the cavity, but also the Eustachian tubes are suppressed. In the Aglossa ouly 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 lite 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- Meckelian 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 Hymenochivus. 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 guins, or investment of the jaws; eg. Lepidobatrachus, several Rana, cy. R. wdspersa, R. khasianu, &. kuhli, and Cryptotis brevis. u SKIN 31 Cranial dermal ossifications are developed in some species of Bufo, still more in the Hemiphractinae, and above all in /elo- hates eultripes and in the Cystignathoid genus Colyptocephalus. The hyoid apparatus of the Anuwa 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 hfe ot 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 lingwae), 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 punetatus.’ 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 PAS. 1897; ps 577. 2 Q.S.US. xxxviii. 1896, p. 465. i) AMPHIBIA CHAP, Go 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. Anura, on the other hand, moult often on land, at least every few months. The surface of the new skin is then quite moist and slimy, but it soon dries and hardens. The Malpighian stratum consists of several layers, thickest in the Perennibranchiata; in them it contains mucous cells throughout life, in others such slime-cells are restricted to larval lite. Later, regular slime-glands are developed, which open on the surface. They are very numerous, and more evenly distributed, over most parts of the body, than the specific or poison-glands, which are restricted to certain parts, often form- ing large clusters, especially ou the sides of the body. They reach their greatest development in the “parotoid glands” of the Anura. Both kinds of glands are furnished with smooth muscle-fibres, which are said to arise from the basal membrane underlying and forming part of the Malpighian layer; these muscle-cells extend later downwards into the corium. For the action of the poison, see p. 37. The stratum corneum is mostly thin, but on many parts of the body, especially in Anura, the epidermal cells proliferate aud form hard spikes or other rugosities, generally stained dark brown. With these may be grouped the nuptial excrescences so frequent in the Anura, especially on the rudiment of the thumb, and on the under surface of the joints of the fingers and toes. In many Anura, less frequently in the Urodela, the tips of the fingers and toes are encased in thicker horny sheaths, producing claws or nails. They are best developed among newts in Onychodactylus, among the Anura in Yenopus and Hymenochtrus. The horny covering of the metatarsal tubercles reaches its greatest size in I SKIN 33 the digging spur or spade of Pelobates. In most of these cases the cutis is elevated into more or less wart-like papillae, covered, of course, by the proliferated and cornified epidermis. In the female of Rana temporaria nearly the whole surface of the body becomes covered with rosy papillae during the breeding season. Similar nuptial excrescences are common, and are most note- worthy in the male of the Indian Rana liebigi. The epidermis also contains sense-organs. They attain their highest development in the larvae; later on they undergo a retrogressive change. Each of these sense-organs is a little cup-shaped papilla, visible to the naked eye. It is composed of elongated cells which form a mantle around some central cells, each of which ends in a stiff cilium perforating a thin, hyaline membrane which lines the bottom of the cup, and is perhaps the representation of the cuticula. These ciliated cells are connected with sensory fibres, the nerve entering at the bottom of the whole organ. The cilia are in direct contact with the water, but the outer rim of the whole apparatus is protected by a short tube of hyaline cuticula-like secretion. These sense-organs are, in the larvae, scattered over the head, especially near the mouth and around the eyes, whence they extend backwards on to the tail, mostly in three pairs of longitudinal rows, one near the vertebral column, the others lateral. They are supplied by the lateral branch of the vagus nerve. They disappear during the metamorphosis, at least in the Anura, with the exception of Yenopus, in which they form conspicuous white objects. The white colour is caused by the tubes becoming choked with the débris of cells or coagulating mucous matter, so that it is doubtful if these organs, which moreover have sunk deeper into the skin, are still functional. In the terrestrial Urodela these organs undergo a periodical process of retrogression and rejuven- escence. During the life on land they shrink and withdraw from the surface, and their nerves likewise diminish, but in the breeding season, when the newts take again to aquatic life, they revive, are rebuilt and become prominent on the surface. They are an inheritance from the fishes, in which such lateral line organs are universally present. The cutis of most Amphibia is very rich in lymph-spaces, which, especially in the Anura, assume enormous proportions, since the so-called subcutaneous connective tissue forms com- VOL. VIII D 34 AMPHIBIA CHAP, paratively few vertical septa by which the upper and denser layers, the corium proper, are connected with the underlying muscles. The spaces are filled with lymph, and into some of them the abnormally expanded vocal sacs extend, notably in Pe/idicola, Leptodactylus, and other Cystignathidae, and in Rhinoderic, The cutis frequently forms papillae and prominent folds, sometimes regular longitudinal keels on the sides of the back; but dermal, more or less calcified or ossified scales are restricted to the Stegocephali and to the Apoda, gv. pp. 79, 87. We con- clude that the Urodela and Anura have entirely lost these organs. Dermal ossifications, besides those which now form an integral part of the skeleton, like many of the cranial membrane-bones, are rare, and are restricted to the .\nura. They are least infrequent on the head, where the skin is more or less involved in the ossification of the underlying membrane-bones, for instance in Triprion, Calyptocephalus, Hemiphractus and Pelobates. The thick ossifications in the skin of the back of several species of Ceratophrys ave very exceptional. In Brachycephalus ephippivm these dermal bones enter into connection with the vertebrae; small plates fuse with the dorsal processes of the first to third vertebrae, while one large and thick plate fuses with the rest of the dorsal vertebrae. Simple calcareous deposits in the cutis are less uncommon, for instance, in old specimens of Bufo vulgaris. We are scarcely justified in looking upon these various calcifications and even ossifications as reminiscences of Stego- cephalous conditions. The skin contains pigment. This is either diffuse or granular. Diffuse pigment, mostly dark brown or yellow, occurs frequently in the epidermis, even in the stratum corneum. The granular pigment is stored up in cells, the chromatophores, which send out amceboid processes, and are restricted to the cutis, mostly to its upper stratum, where they make their first appearance. Contraction of the chromatophores withdraws the pigment from the surface, expansion distributes it more or less equally. The usual colours of the pigment are black, brown, yellow, and red. Green and blue are merely subjective colours, due to interference. A peculiar kind of colouring matter is the white pigment, which probably consists of guanine, and is likewise deposited within cells; cf. the description of the white spots in the skin of Hyla coerulea. ul CHANGES OF COLOUR ae Most Amphibia are capable of changing colour, the Urodela, however, far less than the Anura, some of which exhibit an extraordinary range and adaptability in their changes. The mechanism by which the change of colour is produced in frogs has been recently studied by Biedermann.’ If we examine the green skin of the common Tree-frog, Hyla arborea, under a low power and direct light, we see a mosaic of green, polygonal areas, separated by dark lines and interrupted by the openings of the skin-glands. Seen from below the skin appears black. Under a stronger power the black layer is seen to be composed of anastomosing and ramified black pigment-cells. Where the light shines through, the skin appears yellow. The epidermis itself is quite colourless. The mosaic layer is: composed of polygonal interference-cells, each of which consists of a basal half which is granular and colourless, while the upper half is made up of yellow drops. Sometimes the tree-frog appears blackish, and if then the black pigment-cells are induced to contract, for instance, by warming the frog, it appears silver-grey; in this case the pig- ment in the yellow drops is no longer diffuse, but is concentrated into a round lump lodged between the interstices of the granular portions; the black pigment-cells are likewise balled together. These black chromatophores send out numerous fine branches, which occasionally stretch between and round the polygonal cells. When each of these is quite surrounded and covered by the black processes, the frog appears black. On the other hand, when the black pigment-cells withdraw their processes, shrink up, and, so to speak, retire, then the ight which passes through the yellow drops is, by interference, broken into green. Stoppage of the circulation of the blood in the skin causes the black chromatophores to contract. Carbon dioxide paralyses them and causes them to dilate. This is direct influence without the action of nerves. But stimulation of the central nerve - centres makes the skin turn pale. Low temperature causes expansion, high temperature contraction, of the chrom- atophores. Hence hibernating frogs are much darker than they are in the summer. Frogs kept in dry moss, or such as have escaped into the room and dry up, turn pale, regardless of light or darkness, probably owing to a central, reflex, nerve-stimulus. Tree-frogs turn green as the result of the contact with leaves. 1 treh. ges. Physiol. li. 1892, p. 455. 36 AMPHIBIA CHAP, Dark frogs will turn green when put into an absolutely dark vessel in which there are leaves. This is reflex action, and blinded specimens do the same. The principal centres of the nerves which control the chromatophores, lie in the corpora bigemina and in the optic thalami of the brain. When these centres are destroyed, the frog no longer changes colour when put upon leaves, but if a nerve, for instance the sciatic, be stimulated, the corresponding portion of the body, in this case the leg, turns green. Rough surfaces cause a sensation which makes the frog turn dark. ana seems to depend chiefly upon temperature and the amount of moisture in the air, so far as its changes of colour are concerned. Biedermann concludes that the “chromatic function of frogs in general depends chiefly upon the sensory impressions received by the skin, while that of fishes depends upon the eye.” All this sounds very well, but the observations and experi- ments are such as are usual in physiological laboratories, and the frogs, when observed in their native haunts, or even when kept under proper conditions, do not always behave as the physiologist thinks they should. There is no doubt that in many cases the changes of colour are not voluntary, but reflex actions. It is quite conceivable that the sensation of sitting on a rough surface starts a whole train of processes: roughness means bark, bark is brown, change into brown; but one and the same tree- frog does not always assume the colour of the bark when it rests, or even sleeps upon, such a piece. He will, if it suits him, remain grass-green upon a yellow stone, or on a white window-frame. I purposely describe such conditions, changes, coincidences, and discrepancies in various species, notably in Hylu arborea, H. coerulea, Rana temporaria, Bufo viridis, to show that in many cases the creature knows what it is about, and that the eye plays a very important part in the decision of what colour is to be produced. The sensory impression received through the skin of the belly is the same, no matter if the board be painted white, black, or green, and how does it then come to pass that the frog adjusts its colour to a nicety to the general hue or tone of its surroundings ? Boulenger ' has given us a summary of the action of the poison of Amphibia: : 1 Wat. Sei. i, 1892, p. 185. Pr u POISON 37 It is well known to all who have handled treshly-caught newts, and certain toads, especially Bombinator, that their secre- tion acts as a sternutatory, and causes irritation of the nose and eyes, the effects produced on us by Bombinator being comparable to the early stages of a cold in the head. Many collectors of Batrachians have learned, to their discomfiture, how the intro- duction of examples of certain species into the bag containing the sport of their excursion may cause the death of the other prisoners; for although the poison has no effect on the skin of individuals of the same species, different species, however closely allied, may poison each other by mere contact. But when inoculated the poison acts even on the same individual. Miss Ormerod, to personally test the effect, pressed part of the back and tail of a live Crested Newt between the teeth. “The first effect was a bitter astringent feeling in the mouth, with irritation of the upper part of the throat, numbing of thg teeth more immediately holding the animal, and in about a minute from the first touch of the newt a strong flow of saliva. This was accompanied by much foam and violent spasmodic action, approaching convulsions, but entirely confined to the mouth itself. The experiment was immediately followed by headache lasting for some hours, general discomfort of the system, and half an hour after by slight shivering fits.” Numerous experiments have shown that the poison of toads, salamanders, and newts is capable, when injected, of killing mammals, birds, reptiles, and even fishes, provided, of course, that the dose be proportionate to the size of the animal. Small birds and lizards succumb as a rule in a few minutes; guinea- pigs, rabbits, and dogs in less than an hour. This poison of Amphibia is not septic, but acts upon the heart and the central nervous system. That of the common toad has been compared, in its effects, to that of Digitalis and Erythrophlacum. Some authorities hold that the poison is an acid, others regard it as an alkaloid. Phisalix! has come to the conclusion that toads and sala- manders are possessed of two kinds of glands, different both anatomically and physiologically. These are, first the mucous glands, spread over the greater part of the body, with an alkaloid secretion, which acts as a narcotic; secondly, specific glands, as 1. 2. Ac. Sei. cix. 1889, pp. 405, 482. 38 AMPHIBIA CHAP, the parotoids and larger dorsal glands, the secretion of which is acid, and acts as a convulsive. : The Indians of Colombia are said to employ the secretion of Dendrobates tinctorius for poisoning their arrows. The poison is obtained by exposing the frog to a fire, and after being scraped off the back is sufficient for poisoning fifty arrows. It acts on the central nervous system, and is used especially for shooting monkeys. Concerning the use of this poison for “dyeing” parrots, see p. 272. The milky secretion of toads protects them against many enenues, although not always against the grass-snake. Amer. Natural, xxx. 1886, p. 829. IL LUNGS VOICE 47 smaller in comparison than the right, and there is no pulmonary vein. The auricular septum has a large aperture, the communi- cation between the auricles being larger than even in Nicturus (which breathes essentially by gills). The sinus venosus, instead of opening into the right auricle only, opens more freely into the left than into the right, and the latter communicates more directly with the ventricle than the left, instead of about equally. In short, the heart of these creatures appears almost bilocular, instead of being trilocular, at least functionally. The lungs of the Urodela are always simple, extremely thin- walled bags. They are highly developed in the Anuya, the walls being modified into numerous air-cells, whereby the respiratory surface is considerably increased. The lungs are filled with air by the pumping motion of the throat while the mouth is closed, the nostrils being provided with muscular valves. A muscular apparatus assists the filling of the lungs in the Anura.' Most, if not all, Anura and some Urodela have a veice pro- duced by the larynx, which, especially in the Anura, is provided with a complicated cartilaginous and muscular apparatus and with vocal cords. The voice of the Urodela is at the best a feeble squeak. The females of the Anura are either mute or they produce a mere grunt, but that of many males is very loud, and, moreover, in many species it is intensified by vocal sacs which act as resonators. These sacs are diverticula of the lining of Fic, 6.—Internal view of the mouth of A, the mouth-cavity, and bulge Rana, esculente, B, Bufo calamita (ef: Fig. a 5 p. 269). Ch, Choana, or inner nasal opening ; out the outere skin and the ‘, opening of the Eustachian tube; 5S, slit muscles, chiefly the mylo~ ling inte the vo! az 7, toneves To, hyoid, of the throat. The nostrils and the mouth are firmly closed during the croaking. “The sacs are called internal when they are covered by the unmodified gular integument, however much this may be dis- tended; external when their membrane projects through slits at 1 For the mechanism of the frog’s respiration, see Gaupp, Arch. Anat. 1896, p. 239. 48 AMPHIBIA CHaP. the sides of the throat, as in Runa esculenta (Fig. 52, p. 269), or when the skin is thinned and converted into a bladder-like pouch, as in Ayla arborea.” ' These sacs exhibit many modifica- tions. They may be unpaired and median, and open by two slits into the mouth, on either side below the tongue; in Bufo one of the slits or openings, either the right or the left, is obliterated. They may be paired and symmetrical, and open one on each side of the head, below and near the posterior angle of the jaws. These modifications differ in closely allied species. They reach their greatest complication in Rhinoderma and in some of the Cystignathidae by extending far back beneath the skin into the wide lymphatic spaces. In Rhinoderma they are put to the unique use of nurseries for the young (see p. 228). Leptodactylus typhonius has a very distinct pair of outer vocal sacs and a well-marked unpaired sac which extends into the belly and com- municates with each outer sac. Several species of Paludicola, eg. P. fuscomaculata and P. signifera, have a similar arrangement, in addition to an unpaired gular sac which can be inflated independently of the rest (see Fig. 45, p. 220). URINO-GENITAL ORGANS The kidneys and the male generative glands are still inti- mately connected with each other. The general plan is as follows :— The kidneys consist of a large number of glomeruli, produced by the coiled segmental tubes, each of which is composed of a nephrostome or funnel opening into the body-cavity, a Mal- pighian body and an efferent canal. The latter combine to form the segmental duct which opens into the cloaca. The’ testes, composed of a large number of sperm-producing glands, are drained by transverse canals which combine into a lonpdbndinel canal, and this again sends off numerous efferent canals which open into the efferent canals of the kidney, so that the segmental duct (Leydig’s duct of many authors) conveys both sperma and urine. In the female the network of transverse and longitudinal canals, which originally connect the generative ¢lands with the kidney’s efferent canals, is reduced in so far as the connection is ' Boulenger, The Tailless Batrachians of Europe, Ray Soc. 1896. _ URINO-GENITAL ORGANS 49 Fic. 7.—Diagrammatic representation of modifications of the urino-genital ducts. 1, 2, Male and female Newt; 3, a tubule of the kidney; 4, male Rona; 5, male Bufo, 6, male Bombinator ; 7, male Discoglossus ; 8, male Alytes. a, Artery entering, and producing u coil in, the Malpighian body, Jf; B, Bidder’s organ ; ef.s.c, efferent segmental canal; J.B, fat-body ; gl, glomerulus; A, kidney ; l.c.c, longitudinal collecting canal; iW, Malpighian body; Md, Miillerian duct; J, nephrostome ; O, ovary ; Ov, oviduct ; s.d7, segmental duct; 7, testis ; Uv, ureter ; V.d, vas deferens ; 1.s, vesicula seminalis. VOL. VIII E 50 AMPHIBIA CHAP. interrupted and the vestiges of the transverse canals are no longer functional. The eggs fall into the body-cavity and are caught up by the ostium or inner abdominal opening of a special duct, the oviduct (Miillerian duct of many authors). Vestiges, more or less complete, of these oviducts persist in the males of most Amphibia. . This general scheme presents some modifications in the various groups of Amphibia. The Apoda retain the most primitive conditions. The kidneys are still long and narrow, and the glomeruli are, at least in the anterior part of the organ, still strictly segmental, agreeing in number and position, each with a vertebral segment: later, the number of the glomeruli is greatly increased, and the former agreement becomes quite disturbed. The generative glands still retain their segmental arrangement, but they are restricted to a much shorter region than the kidneys. In the male Apoda a considerable portion of the cloaca can be everted by special muscles, and acts as an intromittent organ. Both sexes possess a ventral urinary bladdey. In the Urodela both kidneys and testes are much concentrated, the testes especially have lost all outward appearance of seg- mentation, and their efferent canals, connecting them with the longitudinal collecting canal, are much reduced in numbers. The greater portion of the kidneys, at least their anterior half, has all the appearance of a degenerating organ and is on the way to losing its urinary function, although it still possesses Malpighian bodies and complete ducts; the main function of the latter is now the conveyance of the sperma. In the Perennibranchiata, and in some others, e.g. Spelerpes variegatus, the longitudinal collecting canal, between testis and kidney, is sometimes sup- pressed, a very simple, but pseudo-primitive arrangement. A urinary bladder is present. The cloaca is not eversible. In most Anura, eg. Rana and Bufo (Fig. 7; 4, 5), the same scheme is adhered to. The efferent canals of the testis form a network, with a longitudinal canal, and open into the efferent canals of the kidney, in the substance of which they are more or less deeply imbedded. The ducts which lead out of the kidney to compose Leydig’s duct, are frequently dilated, or the latter duct is much elongated, convoluted or varicated, and this whole portion is enclosed in a sheath of connective tissue, giving an ul URINO-GENITAL ORGANS Sil appearance as if the single duct itself were dilated in the greater part of its length ; hence the occasional name of vesicula seminalis. Such means of storing the sperma enable the latter to be ejected suddenly in great quantities. In Bombinator (6) some of the most anterior seminal canals do not perforate the kidney, but run over it superticially and open directly into a branch of Leydig’s duct. This branch, no doubt equivalent to a number of segmental canals which have lost their uriniferous function, is curved round the upper end of the permanent kidney, while its forward continuation, ending blindly, is the remnant of its former headward extension. This arrange- ment of Bombinator is carried further in Discoglossus (7). The testis conveys its sperma through a wide duct directly into Leydig’s canal, without interfering with the kidney, and all the testicular efferent network is lost. The anterior end of Leydig’s duct still extends headwards; its middle portion acts solely as a vas deferens, while the lower portion still behaves like a typical segmental duct, conveying both sperma and urine. Lastly, in Alytes (8) the functional division of the old segmental duct has been earried to an extreme. The kidney is drained by one canal only, now a true ureter, and this is of course produced by a consolida- tion of the multiple exclusively uriniferous canals of the lower half of the kidney. The whole of the segmental duct is now in the service of the testis, and near its junction with the ureter it forms a large diverticulum or true vesicula seminalis. Remmants of oviducts, or Miillerian ducts, are common in the male Anura; they are best developed in ufo, much reduced, and individually absent, in Rana. In Bombinator each duct 1s restricted to its upper or abdominal portion, and is attached to the vestigial headward extension of Leydig’s duct. Lastly in is- coglossus and in -Llytes all traces of oviducts seem to have vanished, at least in the adult males. It is interesting to note that in the arrangement of the urino- genital ducts the Discoglossidae are the most advanced of all Amphibia, instead of showing the most primitive conditions. This is rather unexpected, but is paralleled by the epichordal type of the vertebral column. The oviducts of the Apoda and Urodela remain more or less straight ; in the viviparous species they form uterus-like dilata- tions. In the Anura they become greatly elongated during the 52 AMPHIBIA CHAP, breeding season and form many convolutions. As a rule each oviduct opens separately into the cloaca, but in Hyla they have one unpaired opening, while in Bufo and Alytes the lower parts of both oviducts are themselves confluent. All Amphibia possess Fat-bodies. They consist of richly vascularised lymphatic tissue, the meshes of which are filled with lymph-cells, globules of fat and oil. In the Apoda these bodies lie laterally to the generative glands, and along the posterior half of the kidneys. In the Urodela they accompany the anterior half of the kidney. In the Anura they are lobate, and are placed upon the anterior end of the testes or ovaries. Their exact function is still doubtful, but it is intimately connected with that of the generative glands. The old notion, that they are simply stores of fat for the nourishment of the animal during hibernation, is quite untenable. The fat-bodies do not decrease during this period, on the contrary they attain their fullest size in the spring at the time of the rapidly awaking activity of the reproductive organs, and they enable considerable quantities of sperma and of eggs to be produced and ripened without detri- ment to, or utter exhaustion of, the animals, which often spawn before they have had time or opportunity to feed. After the spawning season the fat-bodies have dwindled down to incon- spicuous dimensions. , Lastly, there is in some Anura, hitherto observed in Bufo only, a mysterious organ, intercalated between the fat-body and the testis or ovary. This is “ Bidder’s organ” and it seems to be a rudimentary ovary, or rather that upper, anterior portion of the whole organ which undergoes retrogressive metamorphosis. It disappears in old female toads, but in the males it sometimes assiunes a size equal to, or surpassing that of the testes. The males are in this respect hermaphrodite, and cases are known in which parts of the generative glands have developed testes and egg-bearing ovaries. The spermatozoa of the Apoda and Urodela have an undulat- ing membrane along the tail, while the head-end is either pointed or truncated. Those of Spelerpes fuscus and of Ichthyophis glutinosa measure about 0-7 mm. in total length, those of the other Urodela being much smaller. A peculiarity of the Urodela is that their spermatozoa are massed together in or upon spermato- phores, an arrangement which undoubtedly facilitates the internal II SPERMA-EGGS 53 fecundation of the female without actual copulation. The female takes up such a deposited spermatophore with the cloacal lips, squeezes the sperma out of the capsule which remains behind, and either conveys the former into a special receptaculum seminis, eg. in Sulamandra atra and in 7riton, or the spermatozoa wriggle their way, thanks to the undulating tail, directly up the oviducts to the ova. The spermatophores are composed of a colourless, soft, gela- tinous mass, which is probably produced by the cloacal gland. The shell of jelly is in fact a cast of the cloacal cavity, reproducing all its ridges, furrows and folds, while a toad-stool-shaped papilla of the cloaca makes the inside lumen of the cast, eg. in Triton. Those of Salamandra maculosa are much simpler, consisting, in conformity with the absence of a cloacal papilla, merely of a cone with a globular mass of sperma on the: a ex teenies top. Those of Amblystoma are similar. spermatophore of The spermatozoa of the Anura show con- — 7iton dipesiris. x3. : : ‘ 4 (After Zeller.) ? siderable differences in the various genera, of which, however, only the European forms have been properly examined. The “head” is wound like a corkscrew in Discoglossus, Pelobates, and Pelodytes ; spindle-shaped, more or less curved, in Rana temporaria and R. agilis, Hyla, Bufo and Bombinator, in the latter with an irregular membrane on one side; cylindrical in Rana esculenta and R. arvalis, The tail is mostly long and filiform, but in Bufo vulgaris and Discoglossus it is provided with an undulating membrane. Their size is generally very small, only about 0-1 mm., excepting those of Discoglossus which reach the astonishing length of 3 mm. These differences in shape, especially that of the head, explain why species of the same genus, e.g. funda tem poraria and R. arvalis, cannot fertilise each other. The eggs differ much in size, colour, and numbers. They are holoblastic, with unequal cleavage, lt those species which possess an unusual amount of food-yolk, for instance Rhacophorus schlegeli and the Apoda, approach the meroblastic type of segmen- tation. Asa rule, the greater the amount of yolk, the smaller is the number of eggs.produced. But the nwnber which is laid 1 Zoitschr. wiss. Zool. xlix. 1889, p. 583. 54 AMVHIBIA CHAP. during one season is not only difficult to calculate, but it varies individually, old females laying more than young specimens. Moreover, some kinds, e.g. the Discoyvlossidae, spawn several times in one year. l/ytes, Rhinoderma, Hylodes, Ihacophorus, Pipa, in fact those kinds which are remarkable for special nursing habits, lay only a few dozen eges at a time. Myla arborea pro- duces up to 1000, Rana temporaria about 5000, Bufo vulgaris averages 5000, Bufo riridis and Ranuw esculenta up to 10,000 and more. T. H. Morgan! has observed a Bufo /entiginosus which laid 28,000 eggs within ten hours! The number of eges produced by the Apoda and Urodela is comparatively moderate, in the average a few dozen, Amhlystoma alone laying about 1000. The eggs possess a velatinous mantle of variable thickness and consistency. In dAmphiuma they are strung tovether like the beads of a rosary, and the envelope hardens into a kind of shell. Many Newts and some Anura fasten their eggs singly on to plants and other objects in the water, with or without threads of stiffening mucus. In many Anura, ey. Bufonidae, they pass out as Glosely-set strings of beads, one string out of each oviduct; in others, e.g. Ranidae, they are disconnected, and form large, lampy masses, especially when the gelatinous mantle swells up in the water. The use of this mantle seems to be chietly the protection of the growing embryo, which in many species, when hatched out of the egg proper, drops into and remains for some time in the softened jelly. Possibly the latter affords some nutriment to the early larva. Concerning the mode of fecundation it is to be remarked that copulation proper takes place only in the Apoda. For the Urodela Boulenger® has given the following summary. In no case does actual copulation take place. The male deposits the spermatophores which it is the oftice of the female to secure : I. No amplexus, but a leugthy courtship in ihe water; the male is more brilliantly coloured than the female, and ornamented with dorsal and caudal crests, or other appendages : Triton, cf. also systematic part. IT. Amplexus takes place ; there are uo marked sexual differences in colour and no ornanental dermal appendages. A. Amplexus of short duration, partly on laud, but deposition of the sperma in the water. No accessory sexual characters: Terrestrial Salamanders, namely Salamandra, Chioglossa, Salumandrina. Spel- erpes breeds in damp caves without water. ' Amer. Natural, xxv. 1891, p. 753. 2 Zool. Jahrb. Syst. vi. 1892, pr. 447. ul OVIPOSITION NURSING 55 B. Amplexus of lengthy duration and in the water. «. The male, distinguished by a greater development of the fore- limbs, which are armed with temporary excrescences, clasps the female in the axillary region with the fore-lmbs: Triton waltl. b. The male, distinguished by a greater development of the lind- limbs and a prehensile tail, clasps the female in the lumbar and caudal regions: The Huproctus-group of newts: Triton usper, T. ruscont7, and T. montunas. The act of tecundation of most of the other kinds of Urodela, notably Cryptobranchus, Amphinma, Proteus, has not yet been observed. Embracing of the two sexes is the universal rule with the Anura, the male creeping on to the back of the female and clasping her firmly with the arms and hands either in the inguinal region, higher up, or under the armpits. See the numerous statements in the systematic part. This often ex- tremely forcible, pressing embrace seeins to be uecessary, although the females can deposit the eggs without the help of the male, but in such cases the expulsion takes place at irregular intervals instead of at one time. When the eggs appear at last, and this happens in many species many hours, or even some days, after the beginning of the embrace, the male voids the contents of its seminal vesicles over them. Fertilisation is consequently external, with the possible exception of Pipa, qr. p. 152. Deposition of the eggs and nursing habits—The majority of the Amphibia are oviparous, but some Apoda and Urodela are viviparous. It is unnecessary to call the latter condition ovo-viviparous, since this is really a distinction without a difference. Viviparous forms :—amougst Urodela ; Salamandru. maculosu, the young burst the egg-membrane in the act of being born, and are provided with long gills; S. atra, the young undergo their whole development and metamorphosis within the uterus (see p- 119); Spelerpes fuscus, the young are likewise born in the perfect condition: amongst Apoda; T'yphlonectes compressicaudu and Dermophis thomensis. The oviparous Apoda, at least Jehthyophis and Hypogeophis, and a-few of the Urodela, as Desmognathus and Amphiuma, take care of their eggs by coiling themselves around them in a hole underground. Nursing habits are very common amongst the Anura. 56 ANURA CHAP, Boulenger ' has summarised the various conditions concerning the deposition and care that is taken of the eggs, in the following list, in which more recent discoveries have been interpolated. I. The ovum is small, and the larva leaves it in a comparatively early embryonic condition. A. The eggs are laid in the water :— «. Without further care or preparations: probably the majority of Anura ; all European forms, except Alytes. 6. The eggs are laid in a specially walled-in part of the pond: Hyla faber. B. The eggs are deposited out of the water :— «. In holes, or under grass, near the banks of pvols. The larvae are liberated and washed into the water by the next heavy rain: Leptodactylus ocellatus, L. mystacinus, Paludicola gracilis, Psewdophryne australis and P. bibroni. 6. On leaves above the water, the larvae dropping down when leaving the egg: Chiromantis rufescens, Phyllomedusu theringi, Ph. hypochondrialis, II. The yolk is very large and the young undergoes the whole or part of the metamorphosis within the egg; at any rate the larva doe§ not assume an independent existence until after the loss of the gills. A. The eggs are deposited in damp situations, or on leaves. The young escape as :— a. Tadpoles: Arthroleptis seychellensis, Rhacophorus schlegeli, Rh. maculatus, b. Perfect, air-breathing frogs: Rana opisthodon, Hylodes mar- tinicensis, Hyla nebulosu. B. The eggs are carried hy a parent. w. By the male :— «. Round the legs; the young leaves the egg in the tadpole stage: Alytes, B. In the enlarged vocal sacs; the young leave in the perfect state: Rhinoderma. b. By the female :— a, Attached to the belly: Rhacophorus reticulatus. f. Attached to the back; the young complete their metamor- phosis within the egg: Pipa. y- Ina dorsal pouch which the young leave as tadpoles: Noto- trema marsupiatum ;—or in the perfect state: Nototrema testudineum, N. cornutum, N. oviferum, N. fissipes, and Hyla goeldtt. The development and metamorphosis of many species have been described in the systematic part. The following is a short general account of some of the more important features. Meta- morphosis in the Apoda and Urodela is restricted chiefly to the reduction of the gills, the closing of the clefts, and the loss of the 1 Aan. Nat. Hist. (5), xvii. 1886, p. 463, ul TADPOLES 37 vill-chamber and the finny margins of the tail; but the change from the tadpole to the final Anurous animal implies an almost entire reorganisation. In the earliest condition the embryo consists of a large head and body, while the tail is still absent. Behind the beginnings of the future mouth appears a transverse crescentic fold, with the convexity looking backwards, which develops into the paired or unpaired adhesive upparatus. This consists of large complex glands, developed in the Malpighian layer, originally covered by the cuticula, which soon disappears, whereupon the sticky secre- tion enables the larva to attach itself to the gelatinous mantle of the egg, later on to weeds or other objects in the water. The name of suckers, often applied to this apparatus, conveys ‘a wrong Fic, 9.—Four stages of the development of the adhesive apparatus (1) of Bufo vulgaris ; M, Mouth ; Sp.7. spiracular tube. In 3 the gills are almost completely hidden by the united right and left opercular folds. The small outlined figures indicate the shape and natural size of the tadpoles. (After Thiele.) idea, there being neither muscles nor any suctorial function. The shape of this organ undergoes many changes during the early life of the individual, and differs much in the various genera, affording thereby diagnostic characters At first a crescent, it divides into a right and a left oval or disc, which either remain asunder and behind the mouth (Ranuw, Bufo), or they move for- wards to the corners of the mouth (Hy/«) or further back, and unite again more or less completely, as in Discoglossus and Bombinator. It is mostly of short duration, and disappears by the time that the larva, by the proper development of the gills and the tail and the functional mouth, changes into the tadpole. But in a few species these discs transform themselves into an elaborate ventral disr. Such an organ persists throughout the creater part of the tadpole-stage in certain Oriental species of Rano, all of which, when adult, possess fully webbed toes and 1 J, Thiele, Zeitschr. wiss. Zool. xlvi. 1888, p. 67. 538 ANURA CHAP. strongly dilated discs on the fingers and toes, eg. Rana white headi, PR. natatriv, and L. cavitympanum of Borneo, &. jerboa of Java (this larva was originally described and figured as that of Rhacophorus veiniwurdti), and 2. ufghana of the Himalayan system. These tadpoles, at least those of R. jerboa, ave further remarkable for having the “spiracular” opening very far back on the left side, nearer to the base of the tail than to the snout, so as to be well out of the way when the creature has attached itself by the adhesive dise. The mouth of the tadpoles of Anura is furnished with horny armaments, substitutes for teeth. Their development and that of the mouth in general has been well described by Gutzeit.' In the young larvae of Rana temporaria, one or two days after hatching, a shallow groove appears above the conspicuous pair of adhesive organs. The groove becomes rhombic in outline, and when the mouth has been formed in its centre, the jaws appear in the median corners of ‘the rhombus. The epidermis then rises like a circular wall around the jaws, and Fia. 10. =1, Front view of the mouth of a tad- divides into an upper and pole of Runa temporaria, showing the trans- . verse rows of tiny horny teeth 5 2, three lower lip ; furrows appear nine ae horny teeth, much magnified. (After on them, and between these various papillae and comb-like transverse plates of teeth. The papillae are pos- sibly tactile organs, but although nerves enter them, nerve- endings of a sensory nature have not yet been discovered. On the fourth day the jaws become black, by the tenth day horny teeth have appeared upon all the plates of the mouth- armature, and on the seventeenth day the mouth-apparatus has reached the configuration typical of the tadpole, which is now about 14mm. long. The nunber of horny teeth in 2’. temporaria amounts to about 640. These teeth are not cuticular products, but cornified cells; they are very small, and consist each of one horny cell, which is shaped like a nightcap, the apex of which is cnrved back aud serrated. The little teeth are shed continu- ' Zeitschr. wiss. Zool. xlix. 1889, p. 43. im TADPOLES 59 ously, the renewal taking place by successive cells growing into the bases of the older series. The shape and size differ much in the various genera and species. The comb-like plates, composed of those teeth which surround the lips, seem to be used chiefly for the fixing or hooking of the food, while those which compose the horny beak proper, the armature of the jaws, are used like the radulae of snails. These beaks are likewise composed of a great number of individual teeth, closely packed together in several rows, but the teeth themselves are simple and not serrated. In Ayla avhover there are in all about 560 teeth. The development of the mouth does not begin before the eleventh day ; the horny teeth break through, and the jaws get black edges, on the eighteenth. In Pelubutes fuscus the number of horny teeth is increased to about 1100. In Borborocoetes taeniatus the horny teeth forin series of five bells, which fit into each other like the joints of a rattlesnake’s tail. One of the most extraordinary kinds of tadpoles is that of Megalophrys montana Myr, Annandale (Skeat Expedition) found it at Bukit Besar, Malay Peninsula, from 2000 to 3000 feet above the level of the sea. The tadpoles (Fig. 11) were found in the beginning of the month of May 1899 in sandy streains and in pools of rain-water; they floated in a vertical position, the peculiar membranous funnel-shaped expansion of the lps acting as surface-floats. The inside of the funnel is beset with radiating series of little horny teeth, and the whole apparatus is possibly used for scraping the under-surface of the leaves of water-plants in search of food. Total length of the tadpoles 1 inch.” The gills, the formation of the operculum, and the modifica- tions of the branchial arterial arches have been described fully on p. 43; those of the hyo-branchial skeleton on p. 31. | Fusion of the opercular fold with the skin of the neck, across the branchial region, causes the head to become confluent with the trunk (cf. Fig. 9,3, p. 57). The hody becomes oval, more or less globular, and the alimentary canal is greatly elongated and stowed away in the shape of a neat, very regular spiral, shining through 'M. Weber, Ann. Jard. Botan, Buitenzorg, Suppl. ii. 1898, p. 5. ” For ‘A Synopsis of the Tadpoles of European Batrachians,” see Boulenger, P. Z. 8. 1891, pp. 593-627, pls. xlv.-xlvii. ; also Bedriaga, ‘‘ Tableaux synoptiques pour servir 4 la détermination des larves des Batraciens Urodeles,” C. 2. cfs. France, Set. ii. 1891, pp. 540-546. 60 ANURA CHAP. the ventral wall of the body; the anus opens at the end of a somewhat protruding tube, either in the median line, just in front of the ventral fin (Discoglossidae, Pelobates, Bufo), ov it assumes an asymmetrical position by turning to the right side (/yla, Rana). Although both pairs of limbs begin to bud simultaneously, or Fre. 11.—Tadpoles of Meyelophrys montana from Bukit Besar, Malay Peninsula. x 3. the fore-limbs even earlier, the hind-limbs are hurried on, and appear first, long before the fore-lmbs. The latter lie ready beneath the skin of the gill-chamber, and the right always breaks through the skin, while the left does the same in the Medio- gyrinidae, while in the Laevogyrinidae it is generally pushed through the left-sided spiracular opening, immediately behind the outer gills. According to Barfurth the right limb appears, in about 80 per cent. of Rana esculenta, from two to eight hours before the left. ul METAMORPHOSIS 61 Meanwhile the lungs are being developed, and the tadpole occasionally rises to the surface to breathe air. The gills, which, as has been explained elsewhere, are less ancestral than they are larval organs, degenerate, and all the organs are modified for the coming terrestrial life. The fins of the tail are absorbed, the horny armature of the mouth and lips is shed in pieces and makes room for the true teeth, the eyes receive lids, and the whole cranium, especially the apparatus of the jaws, undergoes the final modifications—widening and lengthening of the mouth, arresting of the mento-Meckelian cartilages, elongation of the Meckelian cartilages or lower jaw proper, shifting backwards of the sus- pensorium, and lengthening of its orbital process to form the pterygo-palatine bridge. The tadpole ceases to feed, the whole intestinal canal is voided of its contents, and by “ histolysis ” is thoroughly rebuilt, becoming wider and shrinking to about one-sixth of its original length, —undoing thereby the spiral—preparatory for the coarser food, which consists of insects, worms, and other strictly animal, living matter. Hitherto the tadpoles have lived on “mud,” confervae, Diatoms, rotting vegetable and animal matter. The anal tube collapses, becomes ultimately absorbed, and a new vent is formed at and below the root of the tail. Barfurth + has made interesting observations and experiments with regard to the absorption of the tail and other organs which disappear during the metamorphosis. This is retarded by low temperature; it is accelerated by rest and freedom from mechanical disturbances, as, for instance, concussion of the water. Hunger shortens or hurries on the last stages of metamorphosis, the absorption of the tail taking place in four instead of five days. Amputation of the tail has no retarding influence ; it is followed at once by regeneration, although the tadpole may be on the verge of reducing the tail. Whilst hungering the whole organism draws upon its available store of material, naturally first upon those parts which sooner or later are to become superfluous. This applies eminently’to the tail, which represents a consider- able amount of “edible” matter, and also to that portion of the skin which still covers the fore-limbs. The elements of the cutis are resorbed, thereby thinning the skin; and consequently the limbs break through earlier in fasting than in well-fed 1 Arch. mikr. Anat. xxix. 1887, p. 1. 62 ANURA CHAP. II specimens. Nature herself seems to apply hunger as an acceler- ator. Mlle. von Chauvin found that the larvae of Urodela normally fast during the transformation, and according to Barfurth the larvae of Rana temporaria eat less after their hind-linbs are fully developed. This is, however, also preparatory for the reorganisation of the gut, which has to be more or less empty -during the shortening process. The loss of the tail is not due to a sudden dropping off of this organ —-a crude but by no means uncommon belief — but is brought about by a very gradual process of resorbtion. When the fore-limbs begin to break through the skin, the tip of the tail shrinks and becomes black, owing to an increase, or rather concentration, of the pigment cells. The reduction proceeds from the tip forwards until on about the fifth day there remains only a short, conical, black stump. From the beginning of this process of reduction the tail is scarcely used for locomotion, the tadpole rowing with its legs, or it crawls and hops about, although the tail may still be 20 mm. long. The cells of the epidermis atrophy, shrink, and peel off, while those of the cutis, blood-vessels, nerves, muscles, and chorda dorsalis become disintevrated, often under- going fatty degeneration. The leucocytes eat up the débris and other dissolved tissue, and carry it away through the lymphatic vessels, to be used as new building material in the rest of the animal. Barfurth asks very properly, Why do these tissues degenerate and die? Because the vasomotor nerve-fibres cease to regulate the circulation. And why does this trophic influence of the central nervous system stop? Because the function of the tail becomes superfluous through the appearance of the fore-limbs. The tail is doomed, and degenerates like any other organ without a function. The whole process is, of course, a recapitulation of ancestral, phylogenetic evolution. CIAPTER ITI NEOTENY— REGENERATION——TEMPERATURE—GEOGRAPHICAL DISTRIBUTION Neoteny.—It has long been known that the larvae of the Spotted Salamander occasionally attain the size of 80 mm. or about 3 inches, whilst the majority undergo metamorphosis when they are only 40 mm. long. Again, larvae of 7'riton have been found, in the months of April and May, 80 to 90 mm. long, still with functional gills, but with the sexual orgaus fully developed. De Filippi! found in one locality in Lombardy, besides a few normal fully metamorphosed specimens of only 30 mm. in length, more than forty specimens, which, although they had attained full size, about 55 mm., and were sexually mature, still retained their gills. According to him such gill-breathing, otherwise mature specimens, occur constantly in a small lake in the Val Formazzo, on the Italian slope of the Alps, in the province of Ossola. Later Duméril° astonished the world by his account of the metamor- phosis of the Mexican gill-breathing Axolotl into an entirely lung-breathing and terrestrial creature, hitherto called Ambly- stoma, and supposed to be not only a different species, but to belong to a different family from the Axolotl, which was known as Siredon uxolotl s. pisciforme, and naturally classed with the Perennibranchiata. This discovery led to a series of observations and experiments, chiefly conducted by Marie von Chauvin, instigated thereto by Koelliker and by Camerano.* It was then found that many, if not most of the European Amphibia, both Urodela and Anura, 1 Arch. per zool. e per Vanat. comp., Genova, 1861, p. 206. 2 Ann. sci. nat. (5), vii. 1876. 3 Mem. Ace. Torino, xxxv. 1883, and Alti Acc. Torino, xvii, 1883, p. 84. See also Woltersdorff, Zool. Garten, 1896, p. 327. 64 AMPHIBIA CHAP. occasionally postpone their metamorphosis, and also that such Urodela sometimes become adult for all practical purposes, but retain their gills. This retardation, the retention of larval characters beyond the normal period, was called Neotenie by Kollmann? (véos, young ; Teivw, extend, stretch). He distinguished further between :—I. Partial Neoteny, namely, simple retardation of the metamor- phosis beyond the normal period, for instance, the wintering of tadpoles of Pelobates fuscus, Bombinator pachypus, Pelodytes punetatus, Alytes obstetricans, Hyla arborea, Rana esculenta, R. temporaria, Bufo vulgaris, and B. viridis: Il. Total Neoteny, where the animal retains its gills, but becomes sexually mature ; hitherto observed in Urodela only, eg. Triton vulgaris, T. alpes- tris, ZT. eristatus, T. boseat, T. waltli and Amblystoma. Inter- mediate stages between these two categories are not uncommon. A satisfactory explanation of the meaning of neoteny is beset with difficulties. Some authorities look upon the phenomenon simply as the result of adaptation to the surroundings, which make it advantageous for the creature to retain its larval features. Others think that the surroundings somehow or other retard or prevent the assumption of the adult characters. Undoubtedly there are many cases in which larvae have been reared in water- holes with steep walls, so that they could not change from aquatic to terrestrial life, and it stands to reason that abnormally forced and prolonged use of the gills and of the tail may stimulate these organs into further growth at the expense of the limbs and other organs which are intended for terrestrial life. But not unfrequently typical neotenic and overgrown specimens occur side by side with others which have completed their metamorphosis, and the same is true of larvae of newts which were reared, for experimental purposes, under exactly the same conditions—for instance, in a high-walled glass vessel. Weismann tried to explain neoteny as cases of reversion to atavistic ancestral conditions, but this idea is based wpon an assumption which is probably wrong. His idea necessitates the supposition that all the Amphibia were originally gill- breathing, aquatic, and limbless animals, and that every feature seen in a larva must necessarily indicate an ancestral phylo- genetic stage. It is, on the contrary, much more probable that 1 Verh. Ges. Basel, vii. 1882, p. 387. Ml NEOTENY 65 the external gills of the Urodela have been developed in adapta- tion to their embryonic and larval, essentially aquatic, life. Con- sequently the possession of such gills would be a secondary, and not, strictly speaking, an atavistic feature. Normal loss of these gills, exclusively pulmonary respiration, and preponderating terrestrial life characterise the final adult Amphibian. These cases of neoteny are therefore instances of more or less complete retardation, or of the retention, of partially larval conditions. The whole problem is, however, by no means simple. Salc- mandra atra has become viviparous, and the whole metaimor- phosis takes place within the uterus; in fact, the young have an embryonic, but no larval period, if by the latter we understand the free swimming and still imperfect stage. Similarly, various Anura— for instance, Hylodes martinicensis—pass rapidly through their metamorphosis, and have suppressed the stage of free swimming tadpoles. On the other hand, in many newts, the duration of the larval period is much prolonged, and moreover is very subject to individual variation. In the Axolotl this larval period is continued until and after sexual maturity is reached, The extreme condition would then be represented by the Perennibranchiate genera. It may seem reasonable to look upon these as the youngest members of the Urodela, and the loss of the maxillae in the Sirenidae and Proteidae supports this idea. But it so happens that the majority of the most neotenic genera are more primitive in the composition of the skull and the verte- bral column than the typically terrestrial and rapidly meta- morphosing genera. Witness the amphicoelous vertebrae, the completeness of the pterygoids, the separate nature of the pala- tine bones, and the separate splenials, as mentioned in detail in the description of their skull. We have therefore to conclude, first, that the various Perenni- branchiate genera do not form a natural group, but are a heterogeneous assembly ; secondly, that they have become Perenni- branchiate at a phylogenetically old stage—in fact, that they are the oldest, and not the newest, members of the present Urodela. At the same time, it would be erroneous to suppose that the first Urodela were aquatic creatures, provided with a finny tail, with small, ill-developed lungs, and with epidermal sense organs. All these features are, on the contrary, directly correlated with aquatic life, and are larval acquisitions, not ancestral reminis- VOL, VIII 7 66 AMPHIBIA CHAP, cences. It would be equally wrong to allude to the absence of lungs in many newts as a piscine and therefore ancestral feature. The development of the typical pentadactyloid limb, the con- nexion of the pelvic girdle with the vertebral column, the development of the aes and absolute suppression of internal gills point without doubt to terrestrial creatures. What then, may we ask, were the first Amphibia like? and how about the external gills? They were undoubtedly akin to the less specialised Lepospondylous Stegocephali, in particular the gill-less Microsauri, and the various stages may perhaps be reconstructed as follows :— (1) Terrestrial, with two pairs of pentadactyloid limbs; breathing by lungs only; with a fully developed apparatus of five pairs of gill-arches, which during the embryonic life perhaps still carried internal gills; with or without several pairs of gill- clefts. Reduction of the dermal armour and of the cutaneous scutes had taken place. (2) Additional respiratory organs were developed by the embryo, in the shape of external gills; these were at first re- stricted to embryonic life (as in the existing Apoda), but were gradually used also during the aquatic life of the larva. These external gills, together with the lungs, have superseded the internal gills, of which there are now no traces either in Urodela or in Anura. (3a) Some Urodeles, retaking to aquatic life, retained and further enlarged the external gills into more or less permanent organs (cf. also Siren, p. 136). (3b) The majority of Urodela hurried through the larval, aquatic stage, and some—e.g. Salamandra atra—hbecame abso- lutely terrestrial. The possession of unusually long external gills by this species and by the Apoda indicate that these organs are essentially embryonic, not larval, features. Regeneration. Most Amphibia possess the faculty of re- generating mutilated or lost limbs. This takes place the more certainly and quickly the younger the animal. The amputation necessary to study these phenomena need not be experimental. Axolotls and other Urodelous larvae frequently maim each other fearfully, by biting off the gills or one or more limbs. The gills do not even require amputation. If the larvae are kept in stagnant water the gills often shrivel up or slough off and grow again. Mt REGENERATION——-TEMPERATURE 67 The same applies to the larvae of viviparous species, e.g. Sala- mandra atra, which, when cut out of the uterus and put into water, soon cast off their long, tender gills and produce a stronger set. In an Axolotl! two years old, a hand was cut off. After four weeks there was a conical stwnp; after the sixth week this stump had two points; in the eleventh week three or four fingers were discernible, and a week later the complete hand. Frequently these creatures reproduce five instead of the normal four fingers. But the more proximal the cut, the more liable is the new limb to reproduce supernumerary fingers, or even extra hands and feet. Complete regeneration of the limb, cut off in the middle of the humerus, took place within five months. Triton taeniatus, adult, reproduces cut fingers within five or six weeks, and if the hand be cut above the carpus, new finger- stumps appear in about one month. Gotte has observed that an adult Proteus did not completely reproduce its whole leg until after eighteen months; and, according to Spallanzani, more than one year elapses before the limb, bones, and cartilages of Zriton regain their normal strength. The Anura are likewise capable of regenerating their limbs, the more readily the younger the specimens. For instance, in a tadpole of Rana temporaria, in which the fore- limbs were still hidden, the hind-limb, cut at the middle of the thigh, reproduced nineteen days later a knee, followed by a short two- toed stump. Ultimately the whole limb became completed. The tail of tadpoles regenerates very quickly and completely, even if it be cut off shortly before the final metamorphosis, when the tail would in any case be reduced. Metamorphosed Anura have almost entirely lost this faculty, but not absolutely. I myself have kept two specimens of Rana temporaria, which, when already adult, had each lost a hand at the wrist. First there was only the clean-cut stump with a scar, but within a year this changed into a four-cornered stump, and two of the protuber- ances developed a little further, reaching a length of about 4 mm. These specimens lived for four years without further changes. Temperature.—Amphibia, like Fishes and Reptiles, are, as a rule, classed as cold-blooded animals, in opposition to the warm- blooded Birds and Mammals. This distinction is one of degree only. The terms poikilothermous and homothermous (croét«iXos, 1 Barfurth, Arch. Entwickmech. I. 1895, p. 117. 68 AMPHIBIA CHAP. variable; @uos, equable) are based upon a sounder principle, but are likewise liable to exceptions. Those creatures which, like Birds and Mammals, possess a specific temperature of their own under normal conditions, that of hibernation being excepted, are homothermous. Cold - blooded creatures have no specific temperature: they more or less assume that of their surround- ings. Frogs and newts, for instance, when living in the water, naturally assume its temperature, which is, of course, many degrees lower in a cold spring than in a shallow pond warmed by the sun on a hot summer’s day. The same applies to the changes from day to night. Dark-coloured tortoises basking in the sun are sometimes so hot that they are disagreeable to touch, since they possess but little mechanism for regulating their heat. The same individual cools down during a chilly night by perhaps 40° C. Anura are, however, very susceptible to heat ; most of them die when their temperature rises to about 40° C. Under such conditions they die quickly when in the water, but in the air their moist skin counteracts the heat, lowering it by evaporation ; otherwise it would be impossible for a tree-frog to sit in the glaring sun in a temperature of 120° F. Toads and others with drier skins seek the shade, hide under stones, or bury themselves in the coolest spots available, and many Amphibia and Reptiles aestivate im a torpid condition during the dry and hot season. Many of them can endure a surprising amount of cold, and during hibernation their temperature may sink to freezing-point. This power of endurance does not apply to all alike; tropical species can stand less than those which live in temperate and cold regions. In spite of many assertions to the contrary, it may safely be stated that none of our European frogs, toads, and newts survive being frozen hard. They may be cooled down to nearly —1° C., and they may be partially frozen into the ice. Circulation of the blood is suspended in such cooled- down frogs; their hmbs may become so hard that they break like a piece of wood, but the citadel of life, the heart, must not sink much below freezing-point, and must itself not be frozen, if the animal is to have a chance of recovering. The protoplasm resists a long time, and so long as some of it is left unfrozen the rest will recover. Hibernating frogs are lost if they are reached by prolonged frost during exceptionally severe winters. Every frog will be killed in an artificial pond with a clean concrete bottom, III GEOGRAPHICAL DISTRIBUTION 69 but if there is sufficient imud, with decaying veyetable matter, the creatures survive, simply because they are not absolutely frozen. A severe winter not infrequently kills off all the younger creatures, while the older and more experienced hide themselves more carefully and live to propagate the race. Geographical Distribution. There is a very ably written chapter on the geographical distribution of the Amphibia by Boulenger in the Catalogue of Butvachia Sulientia, pp. 104-118. He came to the important conclusion that the geographical distribution of the Amphibia agrees in general with that of the freshwater fishes. Giinther’s division into a Northern, Equatorial, and Southern zone is modified only in so far as the last two are combined into one, “Tasmania and Patagonia not differing in any point regarding their Frog Fauna from Australia and South America respectively.” Boulenger recognises— I. The Northern zone—(1) Palaearctic, (2) North American, region. Il. The Equatorial Southern zone. A. Firmisternia division = (Cyprinoid division of Giinther. 1. Indian region. 2. African region. B. Arcitera division = Acyprinoid division of Giinther. 1. Tropical American region. 2. Australian region. In the chapter on geographical distribution in Bronn’s Thierreich, Vogel, Systematischer Theil, p. 296 (1893), and in my Classificu- tion of Vertebrata (1898), due attention had been paid to the Amphibia as well as to the other classes of Vertebrata. It will be seen in the following pages that my arrangement is well applicable to the Amphibia so far as fundamental principles are concerned. It cannot be sufficiently emphasised that any attempt to form the various faunas of the different classes of animals into one scheme must necessarily be a petitio principti. The time- honoured six z00-geographical regions established by Sclater and Wallace represent fairly well the main continental divisions: North America, South America, Africa, Australia, and the large northern continental mass of the Old World, with India as a tropical appendix. There is no correlation and no subordination 7O AMPHIBIA CHAP, in this scheme. Huxley’s division (1868) into Norocaga and ARcTOGAEA (see p. 74) is of fundamental importance. The next improvement was the combination of the Palaearctic and Nearctic “yregions ” into one, an advance originally due to Professor Newton, carried out by Heilprin (1887) as the Holarctic region. I have, in 1893, substituted for it the more appropriate term Pervarctic, meaning the whole mass of land which les around the indifferent Arctic zone. The want of further co-ordination and subordination required the combination of the African and Oriental or Indian countries into a Palaeotropicul reyion (1893); the Ethiopian or African and the Indian or Oriental regions of Sclater and Wallace thereby assuming their proper subordinate rank of subregions. The two primary divisions NoroGakaA and ARCTOGAEA are fundamental. The four secondary divisions; namely the Aus- tralian and Neotropical, Periaretic and Palaeotropreal regions, also stand the test of application to the various classes and main groups of Vertebrata; but naturally, under the present con- ficuration of the world, the Palaeotropical region is nothing but the Southern continuation of the Eastern half of the Periarctic mass of land. This is especially obvious so far as India is con- cerned. There is, however, that broad belt of desert, sand, and salt-steppes, which extends from North-West Africa to Manchuria, and this belt is one of the most important physical features of the Old World. It is complicated by the system of mountain- chains which, broadly speaking, centre at the Pamirs, and radiate westwards through the Caucasus and Alps into Spain, eastwards through the Himalayas into China, and nortl-eastwards to Kamt- schatka ; interrupted by Bering’s Sea, it is continued as the back- bone of both Americas to Patagonia. The tertiary divisions, the subregions, have no real existence. They depend upon the class, or even order, of animals, which we happen to study. The faunistic distribution of the Urodela is not that of the Anura, and both follow separate lines of dispersal, different from those of the various orders of Reptiles, Birds, and Mammals. This must be so. There is no doubt that the dis- tribution of land and water was totally different in the Coal Age from what it is now. The face of the globe at the Jurassic Age can scarcely be compared with the aspect which the world has assumed in the Miocene period. This leads to another consideration, often neglected. We II GEOGRAPHICAL DISTRIBUTION 71 know that the various classes, orders, families, etc., of animals have appeared successively upon the stage. A group which arose in the Coal Age followed lines of dispersal different from one which was not evolved until Jurassic times, and post- cretaceous creatures could not avail themselves of what assisted their ancestors, and vice vers? The Amphibia are bound abso- lutely to the land and to fresh water; transportation across salt water is not excluded, but must be accidental, and is not a case of regular “ spreading.” Speaking generally, the older a group, the more likely is it to be widely distributed. If it appears scattered, this may be due to extinction in intermediate countries or to submergence of former land-connexions. There is great danger of arguing in a cirele. It is one of the most difficult tasks to decide in cases of great resemblance of groups of animals between their being due to direct affinity or to heterogeneous convergence, or parallel development. It is the morphologist who is ultimately responsible for the establishment of faunistic regions, not the systematist, least of all he who accepts an elaborate classification, and then mechanically, mathe- matically, by lists of genera and species, maps out the world. Let us take an example. The Neotropical region and Mada- gascar, but not Africa, are supposed to be faunistically related to each other. In both namely occur Boa and Corallus amongst snakes, Dendrobatinae amongst Ranidae, and of the Insectivora Nolenodon in Cuba, Centetes in Madagascar. More cases can no doubt be found which would strengthen this resemblance, perhaps in support of the startling view that Madagascar and South America have received part of their fauna from the famous Antarctica. But the value of the Insectivores has been disposed of by their recognition as an extremely ancient group, or as a case of convergence, and the two genera are no longer put into the same family as Centetidae. The Dendrobatinae (Aan- tella in Madagascar, the others in South America) are decidedly not a natural group, but an instance of very recent convergence (cf. p. 272). About the members of the ancient Boidae we do not feel quite so sure. It. is therefore advisable to eliminate for zoogeographical purposes groups about which there can be any reasonable doubt, otherwise we may argue that certain genera must cou- stitute a very old family, because they are now restricted to widely pe AMPHIBIA CHAP. separated countries, or on the strength of their distribution we may conclude that the genera in question cannot be related to each other, and do not belong to the same sub-family or family as the case may be. Such groups are the Engystomatinae and the genus NSpelerpes ; amongst reptiles the Eublepharidae, Helodermatidae, Anelytropidae, Ilysiidae, Amblycephalidae. It is customary to represent the various regions and sub- regions as if they had boundaries as fixed as political frontiers. Such limitations are quite arbitrary, and what is of more im- portance, they differ in reality according to the class or order of animals with which we happen to deal. Moreover, there has been, and is probably still going on, an exchange or overlapping of faunas. Such debatable grounds are Central America and the highlands of North-western South America. The famous Wallace’s line, between Borneo and Celebes, Java and Lombok, is absolutely inapplicable to the Anura. From their point of view the Austro-Malayan countries, Papuasia and Polynesia do not form a sub-region of the Australian, but rather of the Palaeo- tropical region. Concerning the Urodela, the division into Palae- and Ne-arctic sub-regions is unjustifiable since Eastern Asia has emphatically American affinities (cf. also p. 96). The Sahara and the rest of Northern Africa are intimately connected with Arabia, Persia, Afghanistan, and Northern India, just as equatorial Africa and Madagascar possess strong faunistic relationship with Southern India and the Malay islands. Limiting factors of distribution—Common salt is poison to the Amphibia ; even a solution of 1 per cent prevents the develop- ment of their larvae. Consequently seas, salt lakes, and plains encrusted with saline deposits act as most efficient boundaries to normal “spreading.” But undoubtedly many individuals have made long and successful voyages across the seas on floating trees. Solutions of lime are likewise detrimental to many species, and it is a general fact that limestone-terrain is poor in Amphibian life, unless, of course, sufficient accumulation of humus counteracts or prevents the calcareous impregnation of the springs and pools in meadows. Salamandra maculosa is, for instance, absent in Central Germany on the Muschelkalk, but it occurs in abundance in neighbouring districts of red sandstone or granite; nor can the larvae be reared successfully in very “hard” water. On the other hand, Profevs lives in the sub- 1 GEOGRAPHICAL DISTRIBUTION 73 terranean waters of Carniola, where the whole country is nothing but limestone. Cold is another powerful limiting factor. The absolute northern Innit of Amphibian life coincides rather closely with the somewhat erratic line of 0° Centigrade of annual mean temperature, a little to the north of which line the ground remains permanently frozen below the surface. The surface- erust, Which thaws during the summer, engenders an abundance of insects as food-supply, but its freezing down to the icy bottom makes hibernation impossible. There are, of course, some ex- ceptions, for instance the occurrence of Urodela in the Schilka river and in the district of Lake Baikal. Ranges of mountains are far less effective barriers than is generally supposed. In many cases the fauna is the same on either slope, and they act rather as equalising or dispersing factors, especially when they extend from north to south. Witness the Andes, owing to which Ecuador and Peru bear a great resem- blance to the Central American fauna, and differ from the tropical parts of South America. The existence of an Ambly- stoma in Siam is another instance. The more specialised a family the more intimately is it con- nected with the physical features of the country. Typically arboreal frogs are dependent on the presence of trees. Some have undoubtedly spread into treeless countries and have changed into prairie-frogs, eg. drris. They come out, so to speak, as something different at the other end, and it is unlikely that these modified descendants redevelop exactly the same features as their ancestors before the migration. Baldwin Spencer! met with only six species of frogs in Central Australia, Limnnody- nastes, Chiroleptes, Heleinporus, and Hyla. They are in the main identical with certain forms found in the dry inland parts of New South Wales and (Jueensland. They are to be regarded as immigrants from the latter regions, which have been able in the majority of cases to adapt themselves to unfavourable climatic conditions by means of a marked development of the burrowing habit, to which in certain cases has been added a capacity for absorbing and holding water. 1 The Horn Scientific Expedition, 1897, p. 155. 74 AMPHIBIA CHAP. Faunistic divisions of the Amphibia. NOTOGHA.—SoutTH WORLD. Characterised by the Cystignathidae* and by the predomi- nance of Arcifera, which form nearly 90 per cent of the Anurous population. I. AUSTRALIAN REGION.— Absence of Apoda and Urodela. All the Anura ave arciferous, with the exception of one species of Fene in the Cape York peninsula. The fauna of the Australian continent and of Tasmania consists chiefly of Cystignathidae and Hylidae (Ayla and Hylella) and several small genera of Bufon- idae (Pseudophiryne,* Notaden* and Myvbatrachus*). It is customary, and from the study of other Vertebrata quite justifiable, to divide the Australian region into several sub- regions, but the Amphibia lend no support to this. The only Amphibian in the Sandwich Islands is a Bufo, closely related to North American species. The only Amphibian in New Zealand is Liopelma,* one of the Discoglossidae which are otherwise con- fined to Europe, North-east Asia, and North-west America, and, to judge from their low organisation, had formerly a much wider distribution. New Caledonia possesses no Amphibia. The Fiji Islands ave inhabited by one or tio species of Cornufer, a genus of Ttanidae. The same genus is typical of the Austro-Malayan und Papuasian islands, the fauna of which consists of Ren and Cornufer, Ceratobatrachus, several genera of Engystomatinae, Hylidae, and Pelobatidae. Il. NeorropicaL neGion.—Characterised by Apoda, Aglossa (Pipa), abundance of Cystignathidae (Hemiphractinae,* Cystig- nathinae, and Dendrophryniscinae*), Hylidae (Hylinae and Amphignathodontinue*), numerous Bufonidae and Engystoma- tinae ; Dendsobatinac* ; the Raninae are represented by a few peculiar genera, mostly restricted to the Andesian province; the genus Rana occurs there in a few species only. Absence of Discoglossidae, Pelobatidae and l)yscophinae. Several species of Urodela, of the genus NSpelerpes, extend from Central America into the Andesian province, one occurs in Hayti, and Pethodun platense in Argentina. This region is by far the richest in the number of families, * indicates Amphibia which are peculiar to the respective regions or sub-regions. reat GEOGRAPHICAL DISTRIBUTION 75 genera and species; the total number of the latter being, accord- ing to Boulenger, about four-ninths of the known species. The region comprises South America, Central America, and the West Indian islands. Central America is naturally debatable ground ; one species of Hy/odes and one Hngystoma, besides about twenty Hylidae, extend into North America proper, while possibly the Raninae have entered the Neotropical region from the north. Bufo is too cosmopolitan to assist our conclusions. The occurrence * of four species of Hylella in South America, one in Australia, and one in New Guinea indicate that this is not a natural genus. From the point of the Amphibia the whole region can be divided into two sub-regions only: (1) The West Indian islands with Central America and the north-western Andesian province ; (2) the rest of South America. ARCTOGAEA.—Nortu WoRrLD. Characterised by the absence of Cystignathidae. I. PERIARCTIC REGION.—-Characterised by the Urodela, these being almost peculiar to the region (ef. p. {6). Absence of Apoda. Presence of Discoglossidae, Pelobatidae, DBufonidae, Raninae. Few Hylinae occur. The whole region can be subdivided into three sub-regions. 1. Western Palaearetic.—Prevalence of Salamandrinae (Saluimundra,* Chioglossa,* Salamandvina,* Triton); VProteidae (Proteus anguinus*); Spelerpes fuscus.* — Discoglossus, Bom- binator, Alytes,* Bufo, Hyla arborea, Pelobates,* Pelodytes,* Rana. 2. Eastern Palaearctic.—Amphiumidae (Cryptobranchus) ; Amblystomatinae ; Salamandrinae (Zviton, Pachytriton,* Tyloto- triton*) ; Amblystomatinae.— Bombinator, Bufo, Hyla arborea, Rana, Rhacophorus. 3. Nearctic—Amphiumidae (Cryptobranchus, Amphiuma*); Proteidae (Zyphlomolye,* Necturus*); Sivenidae* ; Amblystoma- tinae ; most Plethodontinae ; Desmognathinae.* — Discoglossidae, Pelobatidae .(Seaphiopus*); Bufo; Hylidae (Hyla, Aeris, Choro- phitus); Ranu. Il. PALAEOTROPICAL REGION.—Characterised by the presence of Apoda and by the great prevalence of Firmisternal Anura, which amount to nearly 90 per cent of the total population. * indicates Amphibia which are peculiar to the respective regions or sub-regions. ; 76 AMPHIBIA CHAP. Absence of Urodela (except mblystoma persimile*), of Cystigna- thidae, and practically of the Hylidae, only two of which occur in the Himalayan district. But this great chain of mountains should not be included within the region, while the outlying spurs in Upper Burma (with Amblystoma) are debatable ground. The subdivision of this widely extended region is beset with difficulties, chiefly on account of Madagascar and Papuasia. The fauna of Madagascar is very remarkable. All its Amphibia are Firmisternal, a mixture of African and Indian forms. The island agrees with Africa, in opposition to the Oriental countries, in no special point; all the Raninae, except Megalixalus, Rappia, and two rather common species of Rana, belong to different genera. Madagascar differs from Africa by the absence of Apoda, of Aglossa, and Bufonidae. On the other hand, it agrees with India or with the Malay islands, in opposition to Africa, by the possession of Dyscophinae, of the Ranine genus Rhacophorus, and the Engy- stomatine genus Calophrynus. Africa and India agree with each other, and differ from Madagascar by the possession of Apoda, the genera Bufo and Nectophryne, and ly the close resemblance of several genera of Raninae. India, the Malay islands, and Papuasia with Melanesia possess Pelobatidae (Leptobrachiwm,* Batrachopsis,* Asterophrys*), and thereby differ considerably from Africa and Madagascar. Batrachylodes* of the Solomon Islands has unmistakable affinities with Phiynoderma* of Karen, between Burma and Siam; Oreo- batrachus* of Borneo much resembles Phiynobatrachus* of West Africa; and Cornufer, typical of the Malay and Melanesian islands, occurs also in West Africa. All these Raninae indicate that the Austro-Malayan and Melanesian islands belong to the Palaeotropical region. Ceratobatrachus,* type of a sub-tamily, is peculiar to Melanesia. There are consequently several possible modes of subdivision, ul with a different result, according to the group of Amphibia, which we may select as of leading importance, eg. Apoda or Pelobatidae, or Dyscophinae and Rhacophorus. The Engy- stomatinae and Raninae are to be eliminated, since they oceur in all the countries in question, We have either to leave the whole region undivided—and it is a significant fact that the “indicates Amphibia which are peculiar to the respective regions or sub-regions. Ill GEOGRAPHICAL DISTRIBUTION 77 Indian countries possess not one sub-family of their own—or we must break it up into four provinces, not sub-regions :— 1. Ethiopian, or continental African, with Aglossa and Apoda, no Pelo- batidae, no Dyscophinae, few Bufonidae, and many Raninae. Indian and Malayan, with Apoda, no Aglossa, but with Pelobatidae, Dysvophinae, many Bufonidae and Raninae, amongst which Rhucophorus. 3. Malagasy, without either Apoda or Aglossa; with Firmisternal Anura only, chiefly Dyscophinae, ‘and Rhacophorus and other Raninae. 4. Papuasian, without Apoda, Aglossa, Dyscophinae, and Bufonidae, but with Pelobatidae and Ranidae. 19 DISTRIBUTION OF FAMILIES AND SUB-FAMILIES OF THE AMPHIBIA. lai | ae: 2 2 é Palae-arctic. = | ei & & z g 5 | West. Bax 2 Sig |e} = | i S & aes East. s Pe ei eléeié Amphiumidae - + | fs Salamandridae a + 5 A 1 Proteidae a: fo Sirenidae. . ef j Apoda. + | ue oe Aglossa + 1 4. Discoglossidae | oy ef ot Pelobatidae . | Lol an ee Bufonidae aye “Sa + + + oF +] t+ Hylinae. ef + + + 1 1 Aimphignathodontinae : + Hemiphractinae . + Cystignathinae | + + 1 Dendrophryniscinae + Genyophryninae . Engystomatinae . i + 1 + fe ey Dyscophinae | ae de Dendrobatinae | se x Raninae.. oe + + ES + ee eR WP oe Ceratobatrachinae 3 1 signifies the occurrence of only one species of an eee numerous group. x Mantella, cf. p. 71 and p. 2 CHAPTER IV STEGOCEPHALI OR LABYRINTHODOYTS—LISSAMPHIBIA——APODA Sus-Ciass I. STEGOCEPHALI orn PHRACTAMPHIBIA With a considerable amount of dermal armour, especially on the head. Tue earliest known terrestrial four-footed creatures occur in the Carboniferous strata of Europe and North America. They and their immediate allies, which extend through the Permian into the Upper Trias, are now comprised under the name of STEGo- CEPHALI, so called because the whole of the dorsal side of the cranium is covered, or roofed over, by dermal bones (oréyos, roof ; cepary, head). That these creatures, of which naturally only the skeletal parts are known, were not fishes, is shown by the typically pentadactyloid limbs; but to recognise them as Amphibia, and as distinct from Reptiles, is difficult, especially if the incipient Reptilia, which have sprung from some mem- bers of this Stegocephalous stock, are taken into account. However, they possess either two occipital condyles, or none, and their vertebrae are either pseudocentrous or notocentrous, but not gastrocentrous. Moreover, the whole skeletal organisation is still so ideally generalised, that it is easy to derive directly from it the arrangement prevailing in the Apoda and Urodela. The vertebral column always comprises a well - developed, sometimes a very long tail. The vertebrae exhibit three types, two of which are fundamentally distinct, while the third is a further development of the second. — 1. Lepospondylous and pseudocentrous.—The vertebra con- sists of a thin shell of bone surrounding the chorda. dorsalis, and is composed of two pairs of arcualia, which meet each other, CHAP. 1V STEGOCEPHALI 79 forming a suture, along the lateral side of the vertebra, both partaking in the formation of a transverse process which carries the rib. 2a. Temnospondylous. — The vertebra is composed of three pairs of units, which remain in a separate, unfused state. Two of them are dorsal arcualia, one of which tends to form the centrum of the vertebra, which then carries the neural arch. 2b. Stereospondylous—The three component units fuse by co-ossification into a solid, amphicoelous vertebra. The ribs are one- or two-headed, rather strong, but shioit, varely reaching half-way round the body. They occur on all the vertebrae of the trunk and on most of those of the tail. One pair of ribs connects one vertebra, the sacral, with the pelvis, of which the ilium and ischium are generally ossified, rarely also a portion of the pubic region. The shoulder-girdle is very primitive, greatly resembling that of the Crossopterygian fishes. It consists of the following bones :— a median, rhombic, or T-shaped interclavicle, a pair of clavicles, of cleithra, of coracoids, and of scapulae. The limbs show the typical pentadactyle plan, but even in these earliest Tetrapoda the hand possesses only four fingers, with 2, 2,3, 2 phalanges respectively. The foot has five toes, with 2, 3, 4, 4, 3, or 2, 2, 3, 4, 3 phalanges. Many Stegocephali were possessed of a dermal armour, covering either the whole body or only the under parts. Hence the term Phractamphibia (@paxros, armoured). The armour consists of a great number of small cutaneous scales, partly calcified, or perhaps ossified, and arranged in many more or less transverse rows. We can only surmise that these scales were covered by corresponding epidermal sheaths. The skull is ideally complete in the number of separate bones which appear on its surface. Besides the outer nares and the orbits there is always an unpaired, small, interparietal foramen. The whole temporal region is completely roofed over. The following bones are present :—nasals, frontals, parietals, supra- and latero-occipitals , lacrymals (unless fused with the jugals ?), prefrontals, postfrontals, postorbitals, squamosals, and epi- (or opisth-) otics ; premaxillaries, maxillaries, jugals, quadrato-jugals, and supra-temporals; quad- rates, pterygoids, palatines, vomers, and an unpaired para- sphenoid—The lower jaw is composed of a pair of dentaries, y 80 STEGOCEPHALI CHAP. articulars, angulars, and splenials. The dentaries and apparently sometimes the splenials, the palatines, maxillae, and vomers carry teeth. The eyes possess a ring of sclerotic bones. Order I. STEGOCEPHALI LEPOSPONDYLI. Vertebrae pseudocentrous. Sub-Order 1. Branchiosauri.—The young had several pairs of gill-arches, which, to judge from their size and from the Hig. 12.—A, Dorsal and B, ventral views of the cranium of Branchiosaurus salaman- droides, x about 4. (After Fritsch.) C, Posterior view of the cranium of Tremato- saurus, x abouts. (After Fraas.) Lr, Branchial arches ; C, condyle ; Zp, epiotic ; I, frontal ; J, jugal ; L.0, lateral occipital ; J/, maxillary ; NV, nasal ; No, nostril; Pa, parietal ; P7, palatine ; Pm, premaxillary; P.o, postorbital ; lr, prefrontal ; Ps, parasphenoid ; P, pterygoid ; Pt/, postfrontal ; Q, quadrate; (j, quadrato-jugal ; S.o, supraoccipital ; Sy, squamosal ; Sf, supratemporal ; V7, vomer. fact that they are beset with numerous nodules, denticles, or irregular little processes like gill-rakers—seem to have been exposed to the surface and to have carried gills. In the adult the arches and gills seem to be absent. One of the commonest genera is Branchiosaurus, including Protriton. Bb. salamandroides of the Lower Red Sandstone of Europe is known in every stage, from larvae of 16 mm. to the full grown animal of 64 mm. in length. The whole body was IV BRANCHIOSAU RI——-AISTOPODES 8) covered with little cutaneous scales. Pelosawrus and perhaps Melunerpeton are allied genera. The following genera are small newt-like creatures of the Carboniferous age of Europe and North America. In Aeraterpeton of Bohemia, Ireland, and Ohio, the dermal scales were restricted to the under parts; and the ribs were rather long, reaching half way round the body. Gulls have not been observed. A™ crasswm, a European species, reached more than one foot in length, two-thirds of which fall to the tail. The ventral side is covered with a most elaborate armour, which consists of about eighty chevron-shaped rows of little scale-shaped nodules. The epiotic bones end in strange processes, carrying a pair of spikes, giving the skull a “horned” appearance, hence the generic name. Uvrocordylus is an allied genus. Sub-Order 2. Aistopodes.— Body snake-like and without any limbs, hence the name doros, unseen; ribs long, and reaching half way round the body; from Carboniferous strata in Treland and Bohemia, with allied, or perhaps identical forms in Ohio. Dolichosoma longissimum possessed more than 150 verte- brae, and was about a yard long. The epiotics end in obtuse projections, recalling those of Keraterpeton. These marvellous creatures had strange appendages, extending from behind the sides of the head, which were possibly the supports of external gills; since the upper end of one of the visceral arches, probably the hyoidean arch, is attached to the labyrinthic region, and from this arch starts a bony rod which carries long skeletal filaments. The body seems to have been naked. Ophiderpeton had a compound ventral shield, while the skin of the back contained granular scutes. Although the Aistopodes have, not without reason, been looked upon as greatly resembling the Coeciliae or Apoda in organisation, especially in that of the vertebral column, the total absence of any other fossils which might bridge over the enormous gulf between the Coal Age and recent times, makes the attempt to derive the Apoda from these creatures very hazardous. Order II. STEGOCEPHALI TEMNOSPONDYLI. Mostly with rather long ribs and with chiefly ventral armour. VOL. VIII 82 STEGOCEPHALI CHAP, Chelydosaurus trom the Lower Red Sandstone of Bohemia was 3 feet long, and possessed a beautiful, complicated, ventral armour, consisting of about sixty chevron-shaped rows, about three times as numerous as the vertebrae in the corresponding region. Sphenosaurus from the same strata and localities must have been 2 yards long. The trunk-vertebrae of both these genera were composed of four pairs of arcualia. Zrimerorhachis from the Permian of Texas is very imperfectly known, but its trunk- vertebrae, as the name implies, consist of three pairs of separate arcualia, one of which, the interdorsal pair, tends to form a kind of centrum. Dissorophus multicinctus, also from the Permian of Texas, has been described by Cope? as a “Batrachian Armadillo,” and con- sidered allied to Yrimerorhachis. Ten vertebrae are known, of an aggregate length of 93 mm.; the length of the creature was perhaps one yard. The neural spines are elevated, and the apex of each extends in an arch on each side to the ribs. These spinous branches touch each other, forming a carapace. Above, and corresponding to each of them, is a similar dermal and osseous element, which extends from side to side without inter- ruption in the median line, forming a dermal layer of transverse bands which correspond to the skeletal carapace beneath it. This creature remotely approaches the genus Zatachys, Cope, where a dermosteous scute is co-ossified with the apex of the neural spine. The systematic position of this genus is at least doubtful. Aichegosaurus decheni from the Lower Red of Germany, known by many well-;eserved specimens, reached a length of 4 or 5 feet. The trunk vertebrae are tri-partite, those of the tail quadri-partite, like those of the trunk of Chelydosaurus. Young specimens show traces of gill-arches. The thoroughly terrestrial walking limbs have four fingers and four toes; the arrangement of the tarsalia, most of which are ossified, lend support to the view that the morphological axis went through femur, fibula, intermedium, the centralia, the second distal tarsale, and the second toe. The dentine and enamel of the teeth are much folded, and this feature, which applies to most members of this Order, to a lesser degree also to others, has caused them to be comprised under the name of LaByrinrHoponra. The upper 1 Amer, Natural, xxix. 1895, p. 998. IV LABYRINTHODONTA 83 surface of the head shows very characteristically arranged grooves, which probably contained slime -canals and possibly sensory organs. Actinodon and Huchirosaurus are closely allied forms, chiefly from the Lower Red Sandstone of France ; Gondiwanosaurus occurs in the Permian of India. Order III. STEGOCEPHALI STEREOSPONDYLI. These are the most highly developed members of the typical Labyrinthodonta, characterised by their much-folded teeth, and by their solid, bi-concave vertebrae. Zoxomma occurs in the Upper Carboniferous of England and in the Lower Red of Bohemia: Trematosaurus, Capitosaurus, and Metopias from the New Red or Lower Trias to the Keuper of Germany. Muastodonsawrus from the Trias of England and Germany is the most gigantic Amphibian known, with a skull of nearly 1 yard in length. Labyrinthodon from the Keuper of Warwickshire is one of the latest members of the group. Labyrinthodont creatures have also been described from the Trias of South Africa, eg. Rhyti- dosteus ; those from North America are insufficiently preserved. Many of these and allied genera have left their footprints in slahs of Sandstone, both Lower and New Red, in Europe, Africa, and America. But although their spoors are common enough, only a few can with certainty be referred to Stegocephali, e.g. Saurichnites salamandroides of the Lower Red of Germany. The spoors of Chirotherium, common in the New Red of Germany and England, for instance in Cheshire, belong to unknown owners; both the large hind feet (which measure nearly half a foot in length) and the much smaller fore feet, had five digits, the first of which stood off like a thumb. Five- fingered Stegocephali are unknown. There is an almost complete absence of fossil Amphibia from the Upper Trias to the Oligocene. The Stegocephali as such seem to have died out with the Trias. The recent Amphibia, of course, must have had ancestors in the Mesozoic age. There is one little skeleton, from the Wealden of Belgium, which belonged to a newt-like creature, called Hylaeobatrachus croyt. Scarce fragments, described as Mrgalotriton, are known from the Oligo- cene of France, and Zriton itself seems to be indicated by 84 APODA OR COECILIAE CHAP. remnants in the Lower Miocene of France and Germany. But fairly complete specimens of large creatures, much resembling Cryptobranchus, have been found in the Upper Miocene of Oeningen, Canton Solothurn, Switzerland. The first known specimen, now at Haarlem, indicating a total length of 3 feet or more, was described and figured in the year 1726 by Scheuchzer, in a learned dissertation entitled “ Homo dilwvit testis.” Betriibtes Beingeriist von einem alten Stinder Erweiche Herz und Sinn der neuen Bosheitskinder. Which may be rendered as follows :— Oh, sad remains of bone, frame of poor Man of sin Soften the heart and mind of sinful recent kin. This was the motto attached to the illustration, and it remained a warning to mankind until Cuvier declared the skeleton to be that of some large newt. Tschudi named it Andrias scheuchzeri, but it is scarcely generically distinct from Cryptobranchus, being almost intermediate between C. alleghaniensis and C. japonicus, see p. 97. Sus-CLass II. LISSAMPHIBIA., Amphibia without dermal armour. Order I. APODA or LIMBLESS AMPHIBIA. The Amphibia Apoda, Coeciliae or Gymnophiona, are a small group of worm-shaped, burrowing creatures, restricted to the Neotropical and Palaeotropical regions, excluding Madagascar. They have no limbs and no girdles. The tail is extremely short ; the vertebrae are pseudo-centrous, and most of them carry rather long ribs, none of which, however, meet to form a sternum. The whole snake-like body is covered with a smooth and sliny skin which forms numerous transverse folds or rings. The most remarkable feature of the skull is its solid com- pactuess, which stands in direct correlation with the burrowing habits of these creatures. The whole dorsal surface of the cranium is practically roofed in by bone, so that, in this respect, it greatly resembles that of the Stegocephali ; but this resemblance is produced chiefly by a broadening of those bones which exist Iv GENERAL ANATOMY 85 also in the other Lissamphibia, while supratemporals and supra- occipitals are absent. There is, however, a pair of bones which represent either the postorbitals or the postfrontals, perhaps both, of the Stegocephali. The quadrato-jugal arch is enormously developed, and by reaching the parietal, frontal, and postorbito- frontal bones (which latter occur only in Jchthyophis and Uraeotyphlus) and the maxilla, extends over the whole of the orbito-temporal fossa. The squamosal is completely fused with Fic. 13.—Skull of Zehthyophis glutinosa. x8, (After Sarasin.) A, Lateral, B, ventral, C, dorsal view. .d, Posterior process of the os articulare ; Ca, carotid foramen 5 Ch, choana or posterior nasal opening; F, frontal; ./, jugal; Lo, lateral occipital ; Me, maxillary ; .V, nasal; No, nostril; O, orbit; , parietal ; Pa, palatine ; Pi, premaxillary ; Po, postfrontal ; Pf, prefrontal ; Pt, pterygoid ; Q, quadrate ; 4, squamosal ; St, stapes; 7, tentacular groove ; Vo, vomer ; NX, exit of vagus nerve. the quadrato-jugal. The stapes has the typical stirrup-shape, is even perforated by an artery, and articulates distally with the shaft of the quadrate (as in the snakes). The maxilla is very large and broad. Owing to its broad junction with the quadrato- jugal arch, the prefrontal and frontal, the orbital fossa is reduced to a very small hole, or the maxilla completely covers the eye. Somewhere between the latter and the nares the maxilla is perforated by the tentacular groove. The periotic bones are represented by the prootics and epiotics; they fuse with the lateral occipitals and with the parasphenoid. The whole 86 APODA CHAP. orbito-ethmoidal region of the primordial skull is also turned into one mass of bone. The angular element of the lower jaw forms a thick and large process which projects upwards and backwards from the mandibular joint. The former possession of a splenial bone is indicated by the occurrence of a second series of teeth in the mandibles of Jehthyophis and Uraeotyphlus. Other genera have vestiges of this second row, or it may be completely lost. The hyoid and branchial apparatus is more primitive than in any other recent Amphibia. In the larva the hyoid and the first and second branchial arches are connected with each other by a median copular piece. The third branchial arches are free from the rest, but are fused in the middle line, the fourth are loosely attached to the previous pair. In the adult both fuse into one transverse, curved bar, and the second pair of branchials lose their connexion with the basal longitudinal piece and likewise form a transverse bar. The vertebrae are built upon the pseudocentrous type, are amphicoelous, and the chorda is intravertebrally destroyed by cartilage, as in the majority of the Urodela. The number of vertebrae is great, amounting in some species to between 200 and 300, of which a few belong to the tail. The first vertebra is devoid of an odontoid process. The ribs are proximally bifurcated as in the Urodela. The eyes are practically useless, being either more or less concealed under the skin, or they are covered by the maxillary bones. All Coecilians possess a peculiar tentacular sensory apparatus, which consists of a conical ftlap-shaped or globular soft tentacle, which is lodged in a special groove or canal of the maxilla, between the eye and the nose, whence it is frequently protruded while the animal is crawling about. These tentacles in the young Siphonops lie, according to the Sarasins, quite close to the eyes, but are later transferred nearer to the nose. The organ consists of a peculiarly rolled up and pointed fold which arises from the bottom of the sac or pit, where it receives a nerve. It is protruded by becoming turgid with llood, and is retracted by a strong muscle. Into the lumen of the sac are poured secretions from the large orbital (Harderian) gland, to keep the apparatus clean. Hence arose the mistaken Iv GENERAL ANATOMY 87 notion of its being a poison-organ. The whole structure is possibly an offshoot of the naso-lacrymal duct. The skin is most remarkable. In the ripe embryo the epidermis passes smoothly over the surface. Beneath follow two layers of soft cutaneous connective tissue, bound together by transverse or vertical lamellae, so that ring-shaped compartments are formed, and in these are embedded slime- glands. In the adult each compartment is modified into an anterior glandular belt and a posterior space, from the bottom of which grow several scales. The number of cutaneous rings agrees originally with that of the vertebrae; but later, and especially in the hinder portion of the trunk, each ring breaks up into two or more secondary segments, and these no longer agree with those of the skeleton. Each scale is beset with numerous smaller scales which consist of hardened cell-secretions infiltrated with calcareous matter. The whole scale is consequently an entirely mesodermal product of the deeper layers of the cutis. The usual statement that the skin forms imbricating lamellae, on the inner side of which appear the scales, is wrong. The “lamellae” can be lifted up only after the general epidermal sheath has been broken artificially in the constrictions between the rings. No scales exist in the Indian genus Gegenophis and in the American Siphonops, Typhlonectes, and Chthonerpeton, a secondary loss which does not indicate relationship. The scales develop late in embryonic life, and they are reasonably looked upon as inheritances from the Stegocephali. The glands either produce slime, whose function seems to be the keeping clean of the surface of the body, or they are squirt-glands. The latter kind are also numerous and are filled with a fluid which is squeezed out by muscular contraction, and seems to be poisonous, as it causes sneezing to those who handle or dissect fresh specimens. The Coecilians live in moist ground and lead a burrowing life. Their developmental history has only recently been studied, and in but a few species, see Ichthyophis, p. 91, and Hypogeophis, p-92. The female is fertilised internally, copulation taking place by means of eversion of the cloacal walls in the shape of a tube. The spermatozoa possess an undulating membrane; the eggs undergo meroblastic division and the embryos have three pairs of long external gills. Some are viviparous. ' The snake-like, limbless shape of the body (Fig. 15) is, as in 88 APODA CHAP, snakes, correlated with an asymmetrical development of the lungs; the left is reduced, while the right is drawn out into a long cylindrical sac. The liver is likewise very long, and partly constricted into a great number of lobes. Owing to the great reduction of the ribs progression is effected in an almost earth- worm-like fashion by the peristaltic motion of the skin, assisted by its numerous ring-shaped constrictions. The systematic position of the Coeciliae has been, and is still, a controversial matter. The Sarasins took up Cope’s suggestion, that their nearest allies are the Urodela, especially Amphiwma, and they went so far as to look upon Amphiwma as a neotenic form of the “ Coecilioidea,” which they divided into Amphiumidae and Coeciliidae; the Coecilioidea and Salaman- droidea forming the two sub-orders of the Urodela. They based this startling conclusion chiefly upon remarkable resemblances between Amphiuma and Ichthyophis, namely, (1) the mode of laying the eggs on land and coiling themselves around them ; (2) the existence of remnants of a tentacular apparatus in Amphiuma ; (3) Cope’s statement that Amphiwma alone among the Urodela possesses an ethmoid like the Coeciliae. This latter point is, however, erroneous; it has since been shown by Davison t that Amphiwma possesses no ethmoid bone, but that, instead of it, descending plates of the frontals join below the premaxilla and function as a nasal septum, with a canal for the olfactory nerves. We look upon the Apoda with more reason as creatures which of all the Lissamphibia have retained most Stegocephalous characters and at the same time form a highly specialised group equivalent to the Urodela and the Anura. The following are Stegocephalous inheritances peculiar to the Apoda in opposition to the other recent Amphibia: retention of cutaneous scales with calcareous incrustations, greatly resembling the scales of the Carboniferous Microsauri; occasional retention of post- frontal and lateral nasal or lacrymal bones, and of a second row of teeth in the mandible. To these may be added the presence of epiotic bones, and the primitive character of the branchial arches. The loss of all these characters would turn the present Apoda into limbless Urodela, but this assumption does not justify their inclusion in this Order. The possible homology of the tentacular apparatus has been discussed elsewhere, p. 45. 1 J. Morphol, xi. 1895, p 375. Iv COECILIIDAE 89 Fossil Apoda are not known; their subterranean life does not favour preservation. Only family, Coeciliidae. About forty species are known. These have been placed in seventeen genera, mostly on com- paratively slight grounds, and several of these genera are probably \U MMM coeciiac. Fic, 14.-- Map showing the distribution of the Coeciliae or Amphibia Apoda. unnatural, the distinctive characters having undoubtedly been developed independently in various countries. We have to remember that the recent species are the remainder of a formerly much more numerous group; it is also likely that more will be discovered in the tropical forests of South America and Sumatra. Boulenger ' has distinguished them as follows :— I. Cycloid scales embedded in the skin. A. Eyes distinct, or concealed under the skin. a. Two series of teeth in the lower jaw, vw. Quadrato-jugal (squamosal) and parietal bones in contact. Tentacle between eye and nostril. Ichthyophis, 2 species, India and Malay islands, p. 90. 55 below and behind nostril. Hypogeophis, 3 species, East Africa and Seychelles, p. 92. es below and in front of eye. Dermophis, 5 species, America and Africa, p. 93. 5 below the nostril. Coeczlia, 6 species, America. f. Quadrato-jugal separated from parietal. Tentacle close to the eye. Rhinatrema, 2 species, America. a below and behind nostril. Geotrypetes, 1 species, West Africa. 35 below nostril. Uraeotyphlus, 3 species, West Africa and India. b. One series of teeth in the lower jaw. Tentacle in front of the eye. Cryptopsophis, 1 species, Seychelles. 1 Pp. Z, 8.1895, p. 401. go APODA CHAP. B. Eyes below the cranial bones. Quadrato-jugal in contact with parietal. Tentacle near the nostril. Gymnophis, 4 species, South America. Herpele, 2 species, Panama and Gaboon. Il. Without scales. A, Eyes distinct, or concealed under the skin. a. Two series of teeth in the lower jaw. a, Quadrato-jugal in contact with parietal. Tentacle behind nostril ; end of body laterally compressed. Typhlonectes, 3 species, America, p. 93. B. Quadrato-jugal separated from parietal. Tentacle between eye and nostril. Chthonerpeton, 2 species, America. b, One series of teeth. v. Quadrato-jugal and parietal in contact ; tentacle in front of the eye 5 Siphonops, 4 species, America. B. Quadrato-jugal separated from parietal. Bdellophis, 1 species, East Africa. B. Eyes below the cranial bones. a. Two series of teeth. Quadrato-jugal and parietal in contact ; tentacle behind and below nostril. Gegenophis, 1 species, India. b. One series of teeth. Quadrato-jugal separated from parietal. Scolecomorphus, 1 species, East Africa. Boulengerula, 1 species, East Africa. Lehthyophis glutinosa extends from the slopes of the Hima- layas to Ceylon, the Malay islands, and into Siam. A second species, Z. monuchvous, occurs in Malabar, Malacca, Borneo, and Java. JL, glutinosa reaches about one foot in length, with a greatest thickness of a little more than half an inch. The general colour is dark brown or bluish black, with a yellow band along each side of the body. This species has been studied extensively by the Sarasins.! It breeds in Ceylon after the spring monsoon. The ovarian egg is oval, measuring 9 by 6 mm. The yolk is yellow; the blastoderm lies towards one of the poles. The strong vitelline membrane becomes surrounded in the oviduct by a dense albuninous membrane, which forms twisted chalazae, just like those of birds’ eggs, and by these two cords the eggs are strung together. Around all this les another mantle of albumen. The female digs a hole close to the surface in moist ground near 1 Pp. and F. Sarasin, ‘“‘ Zur Entwicklungsgeschichte der ceylonesischen Blind- withle, Jehthyophis glutinosa.” Ergebnisse naturwiss. Forschungen auf Ceylon, 1887-1890, vol. ii. Iv COECILHDAE gl running water, and there lays about two dozen eges. The ege- strings become glued together, entangled into a bunch, and the female coils herself round the bunch and remains in that posi- tion, probably to protect the eggs against other burrowing creatures, as blind snakes (7yphlops and Rhinophis) and certain limbless lizards, with which the ground literally swarms. During this kind of incubation the eggs assume a round shape, and grow to twice their original size, and the mature embryo weighs four times as much as the newly laid ege. The external gills are delicately fringed and red, and they move up and down in the fluid of the egg. The body of the Fic. 15.—Sehthyophis glutinosa x1, (After P. and F. Sarasin.) 1, A nearly ripe embryo, with gills, tail-fin, and still with » considerable amount of yolk ; 2, female guard- ing her eggs, coiled up in a hole underground ; 3, a bunch of newly laid eggs ; 4, a single egg, enlarged, schematised to show the twisted albuminous strings or chalazae within the outer membrane, which surrounds the white of the egg. embryo is at first white, hut becomes pigmented with dark grey. A strong line of lateral sense-organs is formed, and a ring of them lies around the eye and others on other parts of the head. The short tail develops a fin. Of the three pairs of gills the third is the shortest, and is generally turned dorsalwards. In embryos of 4 em. in length the longest gill measures as much as 2 cm. Yolk is still present in embryos which have reached the surprising length of 7 em. Then the gills begin to shrink a little, and at this time one pair of gill-clefts breaks through at the hase of the third external gill. When the larvae are hatched the gills are lost. The young larva takes to the water in a gill-less state, and moves about like an eel. At the bottom of the gill-hole on each side two arches are visible, and there are at this stage neither inner nor 92 APODA CHAP. outer gills. The larvae frequently come up to the surface to breathe. The eyes are large and clearly visible, but the tentacles are still undeveloped. The epidermal sense-organs are numerous, and appear as white spots in the grey skin; about fifty extend from the gill-opening to the tip of the tail. Tchthyophis seems to live a long time in the larval state. At last the gill-clefts close, the tail-fin disappears, and the tentacles come to the surface. The whole skin assumes a totally new structure, and the fish-like larva turns into a burrowing, sub- terranean creature so terrestrial that it gets drowned when made to remain in the water. Hypogeophis.— According to A. Brauer’ three species of Coecilians are found in the Seychelles: Cryptopsophis multipli- eatus, which is rare, Hypogeophis rostratus and H. alternans. They live in moist ground, near the coast in swamps, higher up in humus, under rotten trees and rocks, down to the depth of one foot. In the island of Silhouette, Brauer found them in brooks, at least during the dry season, from May to September. The natives call them “vers de terre.” They seem to propagate during the greater part of the year, provided there is sufficient moisture. The female coils round the eggs, which vary from half a dozen to thirty in number, those of H. rostratus measuring 7-8 mun., those of A. alternans only 4-5 mm. The embryos undergo their whole development in the egg. Four pairs of gill-clefts break through, the first between the hyoid and the first branchial arch, the fourth between the third and fourth branchial arches. There appears also a spiracular cleft between the quadrate and the hyoid arch; this cleft is, however, only developed dorsally, and persists for a shorter time. The external gills appear at the same time as the clefts, upon the first three branchial arches; the third gill is the latest, and remains in a vestigial condition covered up by the two others. The gills, of which the second is the longest, are not (as stated by the Sarasins) direct prolongations of the gill-arches, but they begin as button-like growths upon the arches. They begin to disappear with the absorption of the yolk, getting actually smaller, In embryos of 6 em. they are 6 mm. long, while in embryos of 6.5 cm. they are reduced to 4.5 mm. in length. The | “ Beitrage zur Kenntniss der Entwicklungsgeschichte und der Anatomie der ymnophionen,” Zool. Jahrb, Anat. x. 1897, p. 389, and xii, 1899, p. 477. IV COECILIIDAE 93 first to disappear is the third gill, of course by being resorbed ; and the clefts are closed before the creature leaves the ege. Hypo- geophis not leading an aquatic larval life possesses no tail-fin in the embryonic state, the gill-holes are closed, and the epidermal sensory organs disappear long before the time of hatching. Vestiges of gills appear also on the hyoid and on the man- dibular arch, but on the latter they are of very short duration. Those of the hyoid gradually fuse with the first of the branchial vills, and these also concentrate with their bases so that they ultimately seem to spring from one common stem. Brauer remarks that the distinction between internal and external gills seems to be one of degree only; the hyoidean and mandibular gills namely start from the hinder margin of the arches, just like the internal gills of ZVorpedo according to Ziegler, while the other gills start from the sides of the branchial arches. He also found a pair of little swellings behind the last gill-cleft, and an unpaired swelling (corresponding with a double one in Lehthyophis) in front of the vent. Not unreasonably he sees in these swellings the last, very transitional vestiges of the paired limbs. Typhlonectes compressicauda of Guiana and Venezuela is one of the largest Coecilians, reaching a length of 18 inches, with a body-diameter of 2 inch. The general colour, as in most of these creatures, is olive brown to black. A sort of adhesive dise sur- rounding the vent occurs in this genus. Peters, who described this species, found in one female six embryos of comparatively enormous size, one of them being 157 mm. (more than 6 inches) long, and 12 mm. thick, and devoid of a tail-fin. Instead of lateral gill-openings there is a “bag” on each side 55 mm. long, upon which is distributed a blood-vessel. The Sarasins have examined the same specimen: The gills are not a bag, but con- sist of two flat, unbroken membranes which are closely connected with each other. In fact the outer gills of all Amphibia may be said to begin in the shape of small bags, whence sprout secondarily the gill-fringes; but in Z'yphlonectes they form these flaps instead of growing into the usual three gills. The embryos have no epidermal sense-organs, but plenty of skin-glands. Prob- ably when born they take at once to terrestrial life, the flaps are possibly shed at birth, and there remains a little cicatrix. Dermophis thomensis of West Africa (its other relations live in East Africa, South and Central America) is also viviparous. CHAPTER V LISSAMPHIBIA (CONTIN UED)—URODELA Order II. URODELA or TAILED AMPHIBIA. THE recent tailed Amphibia, Salamanders and Newts in the wider sense, have been grouped into four families which can be con- veniently diagnosed by the following characters :— Both the upper and lower jaws are furnished with teeth. Fore- and hind- limbs are always present. Maxillary bones present. Eyes free and devoid of lids AMPHIUMIDAR, p. 97. Eyes with movable lids! SALAMANDRIDAE, p. 102. Maxillary bones absent. Eyes without lids. Perennibrauchiate PRoTErDan, p. 132. Both jaws are toothless. The hind-limbs, the maxillary bones and eyelids are absent. Perennibranchiate . SIRENIDAE, p. 136. These four families are closely allied to each other, especially the Amphiumidae and the Salamandridae. The geographical distribution of the Urodela is essentially Periarctic, except that about one dozen species each of Amblystoma and of Spelerpes extend southwards into Central America, and in the case of the latter genus even into the Andesian parts of South America. Plethodon platense inhabits Argentina. The Urodela afford good reasons for dividing the Periarctic region into three co-ordinate sub-regions, namely, Nearctic, Eastern and Western Palaearctic. The difference between the European and the Eastern Asiatic fauna is well marked ; the two are—at least with our present knowledge—separated by a wide stretch of country very poor in Urodele forms; while, lastly. » The existence of such a form as Typhlotriton, in the adult of which the eyes become closed up, makes such short diagnoses of the families defective, although there is no doubt about the Desmognathine affinities of this genus. See p. 103. CHAP. V GEOGRAPHICAL DISTRIBUTION 95 there are not a few resemblances between this Eastern Asiatic and the American fauna. The Urodela thus lend no support to the usual division of the Periarctic into a Palaearctic and a Nearctic sub-region. Nor is it possible to divide the Palaearctie into a Eurasian and a Mediterranean province. We have in this case to distinguish between an American, an Asiatic, and a Kuropean is) Bs 1, == SALAM. LECHRIODONTA. III|I!| S;MECODONTA. SSS IcHTHYODEA. ia Fic. 16.—Map showing the distribution of the Urodela. “ Ichthyodea ’’ = Amphiumidae + Proteidae + Sirenidae. fauna. The Asiatic or Eastern Palaearctic sub-region assumes the central position, at least from a merely geographical point of view. It would be unjustifiable to assume a spreading from this centre into Europe, and, on the other hand, into America. The centre existed more probably in the Arctic circle, now devoid of Urodela. So far as mere numbers of species are concerned the huge Asiatic or Eastern Palaearctic region is the poorest, but it is also the least explored, and China will probably yield a good many new forms. We know at present only 15 species, nearly all from the eastern half. These 15 species represent no less than 11 genera, 8 of which (= 75 per cent) are peculiar to the sub-region. Next comes the Western Palaearctic or European sub-region with about 21 recent species of 5 genera, 4 of which are peculiar. America is by far the richest, with no less than 66 species (36 eastern, about 16 western, and the rest Central American, etc.), belonging to 19 genera, 17 of which (= 90 per cent) are peculiar to the New World. But this richness in species is due mainly to the abundance of the two genera Amblystoma and Npelerpes, just as Europe is characterised by its many Tritons. One of the most striking features of the Asiatic sub-region is 96 URODELA CHAP, its difference from the European. Pachytriton, Tylototriton, and two species of Z'riton common. They have very little in (7. pyrrhogaster and 7. sinensis) are the only Salamandrinae, while all the rest are Lechriodont (see p. 102), like the American GEOGRAPHICAL DISTRIBUTION OF THE URODELA | Western Palaearctic. Eastern Palaearctic. American. Sirenidae 1 Siren ene 1 Pseudobranchus Proteids sine 1 Necturus err 1 Proteus 1 Typhlomolge Amphiumidae | si a Laps ie | (1 Andrias, Miccene)| 1 Cryptobranchus Salamandridae 4 Desio- gnathinae Pletho- dontinae Salaman- Amblystomatinae drinae 1 Spelerpes 14 Triton 1 Salamandrina 1 Chioglossa 3 Salamandra 1 Amblystoma 1 Batrachyperus 1 Ranidens 1 Geomolge 1 Onychodactylus 2 Salamandrella 3 Hynobius 1 Pachytriton 1 Tylototriton 2 Triton 1 Cryptobranchus 1 Thorius 1 Haptoglossa 3 Desmognathus 21 Spelerpes 2 Manculus 7 Plethodon 3 Batrachoseps 1 Typhlotriton 2 Autodax 16 Amblystoma 1 Dicamptodon 2 Triton 21 species, 6 genera 15 species, 11 genera 66 species, 18 genera Urodela, excepting the two American Tritons, 7. torosus and The occurrence of an Amblystoma, A. persimite, in the mountains of Siam and Burmah, is most suggestive, and 7. thers will in all probability be found. vir idescens. It must also be borne in e AMPHIUMIDAE 97 mind that the differences between the genera of Ainblystomatinae are in reality very slight; and the same applies to the sub- families themselves. The presence or absence of teeth on the parasphenoid, the possession of amphi- or opistho - coelous vertebrae, do not mean much, and certainly does not forbid the notion that all the recent Urodela are the offspring of one common generalised stock which inhabited the northern portion of the globe. Nothing is gained by hiding the solitary European species of the essentially American genus Spelerpes under the name of Geotriton. It is a Spelerpes in all characteristic points. Speaking broadly, each of the three principal sub-families of Salamandridae is characteristic of a sub-region; the Salamandrinae of the Western Palaearctic, the Plethodontinae of the American, while the Ambly- stomatinae are chiefly Asiatic, at least so far as diversity of genera is concerned. Fam. 1. Amphiumidae.— Without gills in the perfect state. The gill-clefts are in a vanishing stage, being either reduced to one pair of small holes or being altogether absent. The maxillary bones are present. Teeth occur in both jaws; those of the vomers form transverse rows. The vertebrae are amphicoelous. The fore-limbs and hind-limbs are present, but small. The small eyes are devoid of lids. This family is now represented by two genera, with only three species, found in the United States and in Eastern Asia, Cryptobranchus.—The limbs are functional, with four fingers and five toes. The outer digits and the sides of the limbs are bordered with folds of skin. The head and body are stout and depressed ; the tail is short, laterally compressed, and provided with a fin. The skin is very glandular and slimy, and forms a thick, irregularly-shaped fold along the side of the body. C. (Menopoma) alleghaniensis.—The gill-clefts are normally reduced to one pair, individually to the left cleft, the right closing up. There are, however, four branchial arches and vessels. The general colour is brown or grey above, sometimes with darker patches, lighter below. The “Hellbender” reaches a length of nearly 18 inches (about 46 cm.), is entirely aquatic, and is apparently restricted to the rivers and streams of the mountainous districts of the Eastern United States. It is very voracious, living on worms and on fish, being much disliked hy the fishermen, as it takes the angler’s bait, and destroys great VOL. VIII H e1 x4. 5) ns) 5 3 = 3 = 3 copy ~ 8 (&) Cy D ) a 3 a 3S ia) hus japonicus. CHAP. V AMPHIUMIDAE 99 quantities of the valuable food-tish Coregonus albus. Although rather common and easily kept, its larvae still remain un- known, C. japonicus s. mavimus—The Giant Salamander of Japan diflers from its American relation in one essential point only, namely, by the absence of gill-openings and of the modifications of the branchial apparatus connected therewith. It has but three branchial vessels, and the skeletal arches are reduced to two. It lives in Japan and in China, from 600 to 4500 feet above the level of the sea, in small streams of mountain-meadows. It feeds upon fishes, Amphibia, worms, and insects. It is aw fished with the hook and is eaten by the Japanese. The first living specimen was brought to Europe in 1829 by Th. von Siebold, its discoverer. It grew within a few years from 1 foot to 3 feet in length, and died in 1881, at least fifty-two years old. Another specimen lived in the Hamburg aquarium for fourteen years, during which time it is said to have grown 36 cm. (more than 14 inches), having attained a length of nearly 44 feet, or 134 cm. The largest specimen known measures 159 cm = 5 feet 3 inches. The life-history of this species is still imperfectly known. Japanese picture-books contain drawings of the adult and of larvae, the latter showing three pairs of fringed external gills. Young specimens of 16 cm. length have already lost the gills, but still retain a cleft on either side of the neck, in the shape of a horizontal slit, and this is soon after closed up by the skin. The best account has recently been given by Sasaki." Accord- ing to him the Giant Salamander leads a solitary life, concealed in dark places, under rocks in swift-flowing, thickly shaded small brooks of clear and cold water. The animal may be easily captured with a fish-hook, baited with a fish, frog, or several earth-worms, and tied to a string a few feet in length. This is thrust by the aid of a small bamboo- stick into the salamander’s retreat. The string is not tied to the stick, but the point of the loaded hook is forced into one end of it, far enough to keep it in place while this end of the rod is pushed under the rock. When the bait has been thus brought near the salamander, any bite will be instantly felt through the 1 J, Coll. Japan. i. 1887, p. 269. 100 URODELA CHAP. rod. The latter is then withdrawn as quietly as possible, the hook and bait being left. As soon as a jerk of the string is noticed, a pull is made, which generally ends in the capture of the unfortunate animal. If the first pull should fail, the bait is replaced as before, and a second opportunity is offered, which the unwary creature accepts as readily as the first. The fisherman, having obtained one bite, is sure of ultimate success, as the sala- mander does not learn by experience to refuse the proffered morsel. When captured, it emits a peculiar slimy secretion, having an odour much like that of the leaves of the Japan pepper (Yanthoxylon peperitum). This secretion hardens into a gelatinous mass after a short exposure to the air. Temminck and Schlegel state that the act of inspiration is ordinarily performed once every 6-10 minutes. This is true for specimens kept in tubs; but Sasaki is inclined to think that they perform this act less frequently in their native brooks. The eyes are so small that they are obviously of little import- ance; the salamanders capture their prey not by pursuing, but by waiting for its near approach, whereupon they seize it with their teeth by a swift lateral movement of the head. The eggs are said to be laid in August and September, and they form a string resembling a rosary. Each ege floats in a clear fluid, inclosed in a bead-shaped gelatinous envelope, and this is con- nected with the next by means of a comparatively small string. The egg measures about 6 mm. by 4 mm., and is yellow everywhere except at the upper pole, where it is whitish. All attempts to make Cryptobranchus breed in captivity have failed hitherto, owing no doubt to the difficulty of obtaining the cool temperature of its mountain streams. Sasaki’s smallest specimens measured 19 to 20 cm. These had three pairs of very short branchial processes, from 3 to 5 mm. in length, attached just ‘inside the branchial orifice. Each process was somewhat flattened and tapering, most of them still with branchlets. In another specimen, 20°5 cm. in length, the gills had almost wholly disappeared, but the branchial slits were still visible. One of 24°5 em. length showed no trace of gills, and the branchial orifice was completely closed, but still marked by a light streak. Amphiuma means s, tridactyla—The limbs are very much reduced, and end in two or three little fingers or toes. Just in v AMPHIUMIDAE IOL front of the fore-hmbs hes the pair of small gill-clefts, each guarded by two flaps of the skin. There are four branchial arches. The general colour of this eel-shaped creature is black, lighter below. The head is covered with numerous pores, arranged in several rows, which unite in the region of the neck, so that only two rows extend along the sides of the body. It reaches a length of three feet, and lives in swamps or muddy waters, Fic. 18. —Amphiwma une Xt. for instance in the ditches of rice-fields, burrowing occasionally in the mud, feeding on crayfishes, molluscs, small fishes, etc. It is confined to the south-eastern States of North America, from Carolina to Mississippi. According to Davison,’ copulation takes place in May. The rather hard-shelled eggs are deposited in the following August or September, and are connected by a twisted cord. The female lies about them in a coil. The embryos, which are hatched in the month of November or December, have well- developed external gills. By the following February they have 1 J. Morphol. xi. 1895, p. 375. 102 URODELA CHAP. reached a length of.from 68 to 90 mm. (about 3 inches), living in damp localities under rocks or rooted stumps, and have already lost their gills. The legs are said to be relatively longer than they are in the adult. Fam. 2. Salamandridae (Salamanders and Newts).— Without gills in the perfect state. Maxillaries are present. Both jaws are furnished with teeth. The eyes are protected by movable lids, except in Typhlotriton. Fore- and hind-limbs present, although sometimes very much reduced. To this family belong by far the greater number of tailed Amphibia. They have béen, for the sake of convenience, grouped into four sub-families, the determining characters of which are all internal and of comparatively slight importance. Little better is the division into Jfecodonta, with the teeth of the palate in two longitudinal rows diverging behind and inserted upon the inner margins of the two palatine processes, which are much prolonged posteriorly, and Zechriodonta, in which the series of palatal teeth are restricted to the posterior portion of the vomers and form either transverse or posteriorly converging rows. I. Series of palatal teeth transverse, restricted to the posterior portion of the vomers. Parasphenoid beset with dentigerous plates. Vertebrae opisthocoelous : Desmognathinae, p. 102. = amphicoelous : Plethodontinue, p. 108. IL. Series of palatal teeth transverse or posteriorly converging, restricted to the posterior portion of the vomers. Parasphenoid toothless. Vertebrae amphicoelous: Amblystomatinae, p. 109. III. Series of palatal teeth in two longitudinal series, diverging behind, inserted on the inner margin of the long palatine processes. Parasphenoid toothless. Vertebrae amphicoelous: Salaman- drinae, p. 115. Sub-Fam, 1. Desmognathinae.—Comprising only three genera, with five species, in North America. Five toes. Desmognathus——The tongue is attached along the median line, free behind, oval in shape. Three species in the eastern half of the United States. D. fuscus is one of the lungless Urodela, for which condition see p. 46. The skin is nearly smooth; parotoids prominent, gular fold strongly marked. General colour above, brown suffused with pink and grey, some- times with a dark lateral band; under parts mottled brown. The vomerine teeth are frequently absent. Total length, about 4 to 5 inches. They live, carefully concealed in the daytime, under ¥ Sefer eaten ee ane 103 stones in or on the edge of the banks of little mountain streams. The eggs are laid in two long strings, and are wrapped round the body of the female like a rosary, the female having resorted to a hollow in the mud, below a stone or other suitable place. The outer envelope of each egg tapers out into a short stalk, and the several stalks all converge, or are glued together into one common knot, “much hke a bunch of toy balloons held in the hand of a street vendor.” The egg is said to be meroblastic. The larvae seem to remain in the egg until they are nearly: adult, and they emerge at midsummer, with the gills already much re- duced. The complete meta- morphosis takes place in the autumn of the same year. These little newts Fie, 19.—Desmognathus fuscus ; female with eggs i : ; inahole underground, x1. (After Wilder. ) can, according to Wilder, be collected all the year round, in Massachusetts from March to December, except during the time of deep snow. They are nocturnal and are easily kept. Thorius pennatulus, from Orizaba, Mexico, the only species, is noteworthy for its extremely large nostrils, and for the tongue, which is supported by a central pedicle, free all round, and ending ina thick knob, which can probably be protruded. The limbs are weak, and the digits are also much reduced. Total length, under 2 inches, or 50 mm. Typhlotriton spelaeus, of the Rock House Cave in Missouri, is blind, the eyes becoming concealed by the skin during metamor- phosis, when the gills are lost. Sub-Fam. 2. Plethodontinae —The five genera of this almost entirely American sub-family (only one species of which, Spelerpes fuseus, occurs in Europe) can be distinguished as follows :— I. The tongue is attached by its central pedicle only, is free all round, ends in a soft knob and can be shot out to a considerable distance. With 5 toes: Spelerpes, p. 104. With 4 toes: Manculus, p. 106. 1 Amer. Natural. xxxiii. March 1899, p. 231. 104 URODELA CHAP. II. The tongue is attached along the middle line and cannot be pro- truded out of the mouth, Jaws with numerous small teeth. With 5 toes: Plethodon, p. 106. With 4 toes: Batrachoseps. Maxillary and mandibular teeth few in number but very large With 5 toes: Autodaz, p, 107. Spelerpes.— Except in a few species the limbs are well de- veloped and possess + fingers and 5 toes, which are either free or webbed. But in the Colombian S. parvipes, still more in 8. lineolus of Orizaba and S. uniformis of Costa Rica the limbs and digits are reduced to mere vestiges, and are practically without function, the body, with the extremely long tail, having assumed a wormlike shape. The young of many, if not all, species have a pair of short balancers below each nostril; in the adult these organs are reduced to little swellings or lost completely. Several species are lungless, see p. 46. The geographical distribution of this genus, of which some twenty species are known, is very remarkable. The majority live in Mexico and in the United States, a few are found in Colombia and Northern Peru (8. altamazonicus and Plethodon platense being the only Urodeles hitherto recorded from south of the equator), one in Hayti (S. ¢nfuscatus), two (S. subpalmatus and S. uniformis) in Costa Rica, and S. fuscus in Europe. N. bilineatus is a little newt under + inches in length—60-95 mim.—found in the Atlantic States. It is brownish-yellow above, with a black lateral line extending from the eye to nearly the end of the tail. The under parts are bright yellow. It lives on land, in damp places, concealed during the daytime under stones or old trees, whence it emerges after a rain or in the dusk of evening. According to H. H. Wilder,' “ the eggs are deposited in May and June in a single layer upon the lower side of submerged stones, each batch containing 30 to 50 eggs. The stones which are suitable for this purpose must be in the form of an arch, allowing the water to flow beneath. They are generally in the more rapidly flowing portions of the brook, but the depth of water must be such that the eggsare at all times entirely submerged. They are attached to the stone by gelatinous threads, proceeding from the outer envelope, and although they are generally contiguous, they 1 Amer. Natural. March, 1899, p. 235. Vv SALAMANDRIDAE— PLETHODONTINAE 105 are each attached separately.” The eggs are holoblastic. The larvae hatch early and continue for a long time in the larval state, probably two or three years. S. porphyriticus s. salmoneus.—Yellowish-brown or purplish- erey above with tiny darker dots and markings. The sides of the body are salmon-coloured, with a tinge of yellow. The under parts are whitish, turning into salmon-pink on the tail. This beautiful newt reaches about 6 inches in length and has a very moist, slimy skin, which, combined with the hvely motions ot the creature, make it as slippery as an eel. It is found in the Alleghany range, from New York to Alabama. Specimens which I am keeping prefer the wettest part of the cage, where they lie concealed in the moss and mud, leaving their hiding-places at night in search of insects. One of them escaped into the greenhouse and was discovered after nine months, having established its permanent home in a cleft between mossy stones : when the sweepings of a butterfly-net are emptied near its hiding- place it peeps out and with a flash of its long, forked, white- coloured tongue it secures its prey. Occasionally it goes into a tank, when it swims with rapid, undulating motions, the limbs being laid back and remaining inactive ; it sometimes rises to the surface to emit and to take in air, but, although mostly resting half in the water, upon a rotten stump, it often lies for hours at the bottom without stirring. When kept in dry surroundings, the skin soon dries and wrinkles, and the animals show every sign of suffocation and general discomfort. The respiration of this lungless species by means of rapid movements of the throat is very limited, most of the necessary oxidisation of the blood being effected through the skin. S. fuscus.—This, the only European species, is thoroughly terrestrial. It is found in the mountains bordering the Gulf of Genoa, and in Sardinia. Its total length remains under four inches. The smooth, very delicate and easily broken skin is brown above, light below, and speckled with lighter and darker markings. Below each nostril is a slight swelling, the remnant of the cirri or balancers common to the young of many species. It lives in shady surroundings, under stones, in old trees and in limestone-caves, glued to the walls with spread-out toes, belly and tail, quietly waiting for insects and spiders which it catches by flashing out the long tongue. 106 URODELA CHAP. According to J. Berg,' it keeps well in cool, moist and well- ventilated places. It lives on flies, small beetles, and maggots ; ants are also taken at once, probably owing to their lively movements, but a few minutes later the newts roll about in spasms and soon die. Towards the end of March one of Berg’s specimens gave birth to four young, which were 36 mm., or nearly Fic. 20.— Spelerpes fuscus, showing the position and shape of the partly and fully protruded tongue. The figure on the right side shows the tongue and the skeleton of the hyoid ap- paratus.. B, the threadlike, elongated, first branchial arch ; H, hyoid, in reality attached by its outer end to the vicinity of the quad- rate; 7’, tongue. About x 2. (After Berg and Wieders- heim. ) 14 inches long, and differed from the adult only by their exception- ally large nostrils, thereby resembling the Mexican Thorius. The little ones shot out their tongues about 10 mm., feeding on Aphides. i JManenlus—The two species of this genus live in Carolina and Florida. IM. quadridigitatis is a very slender, graceful little animal, about 3 inches in length, the long and thin tail being considerably larger than the rest of the body. Yellowish, minutely speckled with brown above and on the sides, greyish- white below. Life entirely terrestrial. Plethodon.—Alout seven species in North America. This genus has given its name to that of the subfamily, which might with more reason be called Spelerpinae. P. glutinosus is slaty or bluish-black, with small whitish specks, especially on the sides of the trunk, where they are large and often confluent. The skin is smooth and shiny. Total length about 5 inches, half of which belong to the tail. Holbrook con- sidered this as one of the commonest of the North American newts, and mostly widely distributed, from Ohio to the Gulf of Mexico. It usually lives concealed under stones, but prefers fallen trees, probably on account of the insects upon which it ' Zool. Garten, 1896, p. 88. Vv PLETHODONTINAE 107 preys. When taken in the hand it gives off a great quantity of slime. P. erythronotus extends into Canada and is much smaller. Brown or grey above, mostly with a broad, reddish-brown band over the head, back, and tail. The under parts are white, with grey and brown specks. alutodax s. dAnaides.—The large tongue is attached along the median line. The jaws are furnished with few, but surprisingly large, knife-shaped teeth, about ten in the upper and fewer in the lower jaw. The small teeth of the vomers form a chevron-shaped series behind the choanae, those of the parasphenoid stand in one elonzated patch. The tail is round; number of toes, five. Three species in Western North America, from California to Oregon. 1. lugubris.—The eyes are very large and prominent. The upper jaw shows a peculiar recess on either side for the reception of the large lower teeth. The skin is smooth, devoid of parotoid glands, but has a strong gular fold. The upper parts are dark brown or lead-coloured, with whitish dots on the sides; under parts white. Total length some 6 inches, about half of which belongs to the tail. The fingers and toes are very rich in sub- cutaneous venous sinuses. The habits of these creatures are in many respects peculiar. Van Denburgh ! says of A. iecanus “that it usually moves quite slowly, moving one foot at a time, but is capable of motion surprisingly rapid for a salamander. When moving rapidly, it aids the action of its legs by a sinuous movement of its whole body and tail. The latter is prehensile. Several individuals, when held with their heads down, coiled their tails around my finger, and, when the original hold was released, sustained them- selves for some time by this means alone. One even raised itself high enough to secure a foothold. This animal’s tail is also of use in another way. When caught, it will often remain motionless, but if touched, will either run a short distance with great speed, ov quickly raising its tail and striking it forcibly against the surface on which it rests, and accompanying this with a quick motion of its hind-limbs, will jump from four to six inches, rising as high as two or three.” Ritter and Miller” have made extensive observations on the life- history of 4. lugubris. When wishing to pass from the hand to ' P. Calif. Ac. (2) v. 1895, p. 776. 2 Amer. Natural. xxxiii. 1899, p. 691. 108 URODELA CHAP. the table, the creature will frequently execute a well co-ordinated spring and alight on its feet some distance away, instead of falling over the edge in the typical salamander-fashion. This species is nocturnal and entirely terrestrial, and seems to be indifferent even to proximity to water. Rotten stumps and logs are the habitations preferred, and wherever these occur in the region about San Francisco Bay, even though at the places remotest from water, specimens are sure to be found. The eggs are laid in a hollow under ground, and the female seems to remain curled around them until they are hatched, which takes place in two or three weeks. The specimen observed by Ritter and Miller laid 19 eggs. Each was contained in a gelatinous capsule 6 mm. in diameter, and was firmly anchored to a clump of earth by a narrow peduncle about 8 mm. long. The embryos developed very large gills, each being composed of three broad membranous lobes, the latter being thin and delicate, much expanded, highly vascular and widely confluent at their bases, so that the gills of each side really form one three-lobed mass. Their dorsal surfaces are appled to the inner surface of the egg-capsule. The amount of food-yolk is considerable. The whole larval life is passed through within the egg. Before the young is hatched the gills wither and cease to be functional, and the gill-shts close up. The tail is round, and shows no indica- tion of a fin at any time during the larval period. Newly hatched individuals appeared much distressed when put into water, and were quite unable to swim. They immediately sank to the bottom and remained there until they were removed. The integumentary sense-organs, so well developed in the aquatic larvae of Urodeles, are entirely wanting. When hatched the young creature is about 32 mm. long; its general colour is blackish-grey, finely sprinkled with bluish-silver. During the second year this garb is changed to the dusky brown of the adult, and the fine silver speckling is replaced by much larger and less numerous yellow spots. Although one of the most terrestrial of Urodeles, this species is lungless, but the skin remains delicately smooth and moist throughout life. According to the observers quoted, the pharynx plays an important part in respiration. From 120 to 180 or even more vibrations are made by the throat in a minute, and in some cases these movements are grouped into series of about Vv SALAMANDRIDAE—AMBLYSTOMATINAE 109 20 to 25 extremely rapid vibrations, with periods between each two series. Subfam. 3. Amblystomatinae,—Composed of seven closely allied genera, the distinguishing characters of which are the grouping of the palatal teeth and the number of the toes, which varies between 4 and 5. The geographical range of the subfamily extends over the whole of North America and Mexico and over the whole of Northern Asia, from Kamtchatka and Japan westwards to the Ural, and southwards into China. The occurrence of one species, Amblystoma persimile, in the moun- tains of Siam, makes it highly probable that other species and genera exist in the hitherto unexplored intervening countries. Boulenger gives the following synopsis :— I. The series of palatal teeth converge backwards, forming a V-shaped figure. With 5 toes: Hynobius, 3 species in Japan. With 4 toes: Salamandrella, 2 species Lake Baikal, Ussuri and Schilka rivers, and Kamtchatka, p. 109. Il. The series of palatal teeth form an uninterrupted, doubly arched V-shaped figure. The 4 fingers and 5 toes are furnished with black, horny claws : Onychodactylus japonicus. III. The series of palatal teeth form two arches, convex forwards, separated by a wide interspace. The two series are short, confined to the space between the choanae. With 5.toes: Ranidens sibiricus, Eastern Siberia and N.E. China. With 4 toes: Batrachyperus sinensis, Moupin in China. The series are long and converge backwards, 5 toes: Dicamp- todon ensatus, California. IV. The palatal teeth are arranged in a nearly straight, transverse line, or they form an angle which points slightly forwards ; they are not separated by a wide median space. With 5 toes: Amblystoma. Some 16 species in North and Central America, one in Siam, p.110. Salamandrella keyserlingi.—The mode of propagation of this newt-like species has been observed by Shitkow near Jekaterin- burg in the Ural mountains. The eggs were laid at the end of April and were deposited in bags, which were attached to a plant, with one end about an inch below the surface of the water. The bag measured 15 cm. in length and 2 cm. in width and contained 50 to 60 eggs. The larvae were hatched in 14 days in a sunny aquarium; in another with a northern Ilo URODELA CHAP. aspect the hatching took 23 days. The larvae were 10 mm. long, and remarkable for the length (1 mm.) of their balancers. Amblystoma opacum.—The general shape is very much like that of the European Spotted Salamander. The head is short and broad, the snout is rounded. The eyes are very pro- minent, with a black pupil and a dark-grey iris. The neck has a well-marked gular fold. The tail is thick and almost round. The hind-limbs are considerably larger than the fore-limbs. The general colour of the shiny, moist skin is a purplish-black with light grey, transverse, partly confluent bars, giving the creature a pretty appearance; the under parts are paler, bluish-grey. Total length between 3 and + inches, or 9 cm. This beautiful species inhabits many of the United States east of the Rocky Mountains, from New Jersey to Florida and Texas. In the perfect state it is thoroughly terres- trial and easily kept. My specimens prefer the holes of rotten and moist, ‘moss-covered stumps, or holes beneath stones, which they leave, at night only, in search of earthworms and insects. A. talpoidewm is closely allied, somewhat stouter and almost uniform FF a oe brownish - back. According to Hol- brook, “ it chooses light soil in which it will bury itself in a few seconds like a mole, and there continue its course concealed from view ; but its track can often be followed by the elevation produced on the surface of the soil, similar to that seen in fields infested by moles.” A. punctatum is bluish-black, with a row of roundish yellow spots on each side of the body and tail and upon the limbs. E. A. Andrews! has made observations upon the breeding of this species. Near Baltimore the eggs are very abundant in March and even in February, in small pools in the woods, but the adults are then rarely seen. Even when small pools, but 4 feet wide and 9 inches deep, were thoroughly raked out ' Amer, Natural. xxxi. 1897, p. 635. v AMBLYSTOMATINAE II! before and after the eggs appeared, no adults were found, so that it is to be inferred that the laying takes place in the night and that the adults leave the water every day to conceal them- selves under stones. One female was found moving away from a bunch of eggs early in the morning. This specimen was kept isolated, and laid many eggs, and as these developed into normal larvae, the existence of internal fertilisation was proved. Previously to the laying of the eggs white spermatophores were found in the small pools, on the dead twigs and leaves covering the bottom. al. jeffersonianum.—This very slender and slippery species, reaching a length of 6 inches, is remarkable for its long fingers and toes, and its rather compressed tail. The general colour is brown above, dirty whitish below, generally with numerous, small, light blue and pale brown spots on the sides of the neck, body, limbs, and tail. There are several colour-varieties, one of them with white specks. It is a very active and surprisingly good climber, easily escaping out of high-walled bell-glasses, hiding in the daytime in dark and moist localities. Its range extends from Indiana and Virginia to Quebec. 1. persimile.—-This species is rermarkable on account of its geographical distribution. It is the only non-American species, inhabiting the higher mountains of Siam and Upper Burmah. There is no doubt about its belonging to the genus Amblystoma, although it had originally been described as a Plethodon. It closely resembles A. jeffersonianum in most of its characters, notably in the arrangement of the palatal teeth, general propor- tions, slender toes, and even in the presence of whitish spots, which are scattered over the sides of its blackish, smooth skin. A. tigrinum.—This, the commonest species, is conspicuous for its large, depressed head, which is as broad as it is long, ,its; width being enhanced by the unusually large parotoid glands, The mouth is very wide. The large, prominent eyes are golden, and reticulated with brown. The gular fold is strong. The limbs are stout,‘the fingers and toes short. The trunk is strongly constricted by twelve intercostal grooves. The tail, which is as long as the rest of the body, is somewhat compressed laterally, but bears no trace of a fin. The general colour is more or less dark brown or bluish black, marked with numerous yellow spots and large blotches; the under surface inclines to rie URODELA CHAP, vrey. The length of the adult male is about half a foot; the females, as usual being larger, sometimes reach the length of 9 inches. The range is from New York to California and to Central Mexico. The larva of this species is the famous Axolotl. It is provided with three pairs of delicate and much-branched external gills, a flat, long tail with a broad ventral and dorsal fin, the latter extending along the back almost to the neck. The limbs, although comparatively slender, are fully developed, and the head is much more pointed than it is in the perfect form. The larvae usually reach 8 or 9 inches in length; exceptional specimens SS a Fra. 22.—Axolotls or larvae of Amblystoma tigrinum, x 1. have been recorded of one foot in length, and have been described as Triton ingens. These larvae were found by the Spanish conquerors to occur in great numbers in the lakes near Mexico City, and were called Axolotl by the natives, a word signifying “play in the water.” They were, and are still, eaten, either roasted or boiled, with vinegar or cayenne pepper. For many years these creatures were looked upon as a species of the Perennibranchiata, under the generic name of Siredon (S. axolotl, s. pisciformis, s. mexicanus, ete.), although Cuvier suspected that they were but the larvae of an otherwise unknown terrestrial Urodele. The mystery was not cleared up until the year 1865, when some Axolotls which had been kept for a year in the Jardin des Plantes at Paris, suddenly began v AMBLYSTOMATINAE 113 to pair, and laid eggs which within six months developed into full-sized Axolotls. This certainly looked as if these creatures were not larvae, but a true Perennibranchiate species. But to the general surprise several of these young Axolotls gradually lost their gills, the clefts closed up, the fins of the back and tail disappeared, the head became broader, the crea- tures left the water permanently, and in fact turned into the already well-known terrestrial Amblystoma tigrinum. The other brothers and sisters of the same brood remained aquatic Axolotls, which thereby revealed themselves after all as the larval and not as the perfect stage of this remarkable species. At the suggestion of Kolliker and Weismann, Frl. Marie von Chauvin! undertook, at the University of Freiburg, long and carefully conducted experiments, showing (1) that little Axolotls can comparatively easily be caused to develop further into the perfect Amblystoma if they are induced to breathe air more frequently than usual ; shallow vessels, perhaps also insufficiently aerated water, will produce the desired result; (2) that the commencing metamorphosis can again be checked, the shrinking gills then undergoing fresh development; (3) that they can be forced to remain Axolotls; (4) that the cutting off of the gills has no influence upon their possible metamorphosis, the gills being easily and quickly renewed. The same lady found also that Amblystoma, the perfect form, lives in the water during the pairing time and behaves in the same way as the Axolotls. The latest observations have been made by Metzdorff’ Axo- lotls, at least those which are kept in captivity in Europe, are ready for propagation several times in the year, either in the spring, from April to June, or in December. The male deposits spermatophores, which in the following night are taken up by the female into the cloaca. On the following day, preferably in the afternoon, she grasps a suitable leaf, for instance that of Vallisneria, with the hind-limbs, and presses it against the vent. The eggs are expelled by strong wriggling movements of the body, and are formed into three or four packets of six to ten eggs each, so that about thirty eggs are laid at one sitting. 1 Zeitschr. wiss. Zool. xxvii. 1877, p. 522; xli. 1891, p. 365; Zool. Anz. 1882, p. 513. 2 Zoology. Garten. 1896, p. 114. VOL. VIII I T14 URODELA cuap. Then she takes a rest before proceeding again; the whole process, in which the male takes no further interest, lasting about two days. The most suitable temperature is one of 18-20° C., or about 68° F. The water must be well aerated. Sterile egos tum white on the second day. The little larvae are hatched in about a fortnight. Eggs which are kept in a higher tempera- ture, from 22-24° C., develop more quickly, but the resulting young are smaller; they show already on the fifth day head, tail, and the beginning of the gills. According to Bedriaga, they live at first upon Infusoria and Daphnia; when they are 20-25 mm. long they eat 7ubifex rivulorum ; later on they take scraped meat and are liable, when hungry, to nibble off each other’s gills, but these are easily reproduced. When 20-25 em. long, at the age of about six months, they are able to breed. The chief point of interest is the fact that this species of Ambly- stoma frequently remains throughout life in the larval state, except that it develops generative organs. The natural causes of this retention are not completely known. According to Shufeldt, who observed them under natural conditions near Fort Wingate in New Mexico, plenty of food, the drying up of the swamps, and the increasing temperature of the diminishing water, hurries on the metamorphosis, while deeper water retards it. Weismann? suggested that the specimens in the Mexican lakes which remained Axolotls were prevented from becoming _ perfect Amblystomas on account of these lakes, after the disappearance of the surrounding forests, having receded from their former boundaries, which are now covered with a saline, uninhabitable crust. This may be an explanation, although Axolotls: do not live in brackish water. But Weismann went farther, and with his well-known dialectic powers has succeeded in spreading the belief not only that the Axolotl is a case of reversion to an ancestral stage, but that the present Amblystoma, instead of being the progressive, perfect form, is likewise a case of reversion. A reversion from a reversion! The whole line of evolution would then be as follows: Amblystoma; its young, owing to adverse circunstances, revert to the stage of the Perennibranchiate ancestors of all Urodela ; if some of these Axolotls lose their gills and fins, they revert thereby into the original Amblystomu. 1 Zeitschr. wiss. Zool. xxv. 1875, p. 297. See also Hahn, Rev. Quest. Set. (2), i. 1892, p. 178. Vv SALAMAN DRIDAE—SALAMANDRINAE 115 Surely a roundabout way of explaining a curious but after all rather simple process of Neoteny; cf. p. 63. Observations on the metamorphosis of Siredon lichenoides into Amblystoma mavortiwm have been made by Marsh, who also gives figures of the larval and adult forms.’ Sub-Fam. 4. Salamandrinae.—The six genera of this sub- family fall into two natural groups: I, True Salamanders, with the palatal teeth arranged in a pair of S-shaped figures, and without a fronto-squamosal: arch. II, Tritons, with the palatal teeth in the shape of a A, z.c. the right and left series meet at an angle; the fronto-squamosal arch is present, either bony, or at least ligamentous. Triton cristatus is, however, exceptional, in that the two palatal series often do not meet and that the arch is absent. The number of fingers is universally four, that of the toes is five except in Salamandrina, which has only four. The geographical distribution of the sub-family, entirely Peri- arctic, may be said to be the reverse of that: of the Amblystomatinae. Of the twenty-five species namely, only two are American, four are Eastern Asiatic, and of the remaining nineteen, twoare Algerian, while the rest live in Europe or in Asia Minor. It is in fact an essentially Palaearctic group. The six genera can be distinguished as follows :— I. The palatal teeth are arranged in two S-shaped curves. True Sala- manders. Tongue short and thick. Salamandra, p. 115. Tongue long and projectile. Chzoglossa, p. 121. II. The palatal teeth are arranged in a A shape. True Tritons. With only four toes. Salamandrina, p. 122. With five toes. Pterygoids separated from the maxillary and quadrate bones: Triton, p. 122. Pterygoids touching the maxillae and quadrates. Himalo- Chinese : Tylototriton, p. 132. Pterygoids united broadly with the maxillae. Chinese : Pachytriton, p. 132. Salamandra.—Without fronto-squamosal arch. Five toes. Tail round. Three species in Europe and Western Asia. S. maculosa.—The Spotted or Fire Salamander. General habit stout. Usual length about 5 to 6 inches; the females are mostly larger than the males; specimens of more than 8 inches in 1 Aner. Journ. Set. (2), xlvi. Nov. 1868, p. 364. 116 URODELA CHAP. length are giants. Head as broad as it is long, snout rounded. Limbs and digits stout and short. The skin is smooth, shiny and full of pores, with a strong gular fold. The parotoid glands are large and covered with large pores. A series of distinct swellings, or cutaneous glands, each with a distinct opening, extends along either side of the back, and a shorter series along the flanks. The general colour of the Spotted or Fire-salamander is black, with irregular, large yellow patches on the back and limbs. These markings vary extremely, so much so that scarcely two specimens, collected at random, are alike. In some the yellow patches form two more or less regular bands, in others they are partly confluent ; again the yellow may be preponderant on the back or much restricted. Occasionally the chrome- yellow is replaced by orange. The under surface is as a rule bluish grey-black. This combination of shiny yellow and black is a good instance of warning colours. The creature is poisonous, cf. p. 38. When left in peace, or handled gently, it is perfectly harmless, but when treated with violence, or submitted to severe pain, a milky white fluid exudes from the glands and is, under violent contractions of the muscular skin and body, sometimes squirted out in fine jets to the distance of a foot. Burning pain and subsequent inflammation result if this poison gets into the eye. The same applies to the mucous lining of the mouth and throat. A few drops of this poison introduced into the blood or into the stomach of a small animal are sufficient to cause its death. Cold-blooded animals are as susceptible as warm-blooded creatures. I once put two American bull-frogs into the same outdoor en- closure with a large number of salamanders. Next morning the huge frogs were found dead, each having swallowed a salamander, which they were not acquainted with and had taken without suspicion. The Fire-salamander has a wide range, namely the whole of Central, Southern, and Western Europe with the exception of the British Isles. It extends southwards into Corsica and Algeria, eastwards through Asia Minor into Syria. Where it does occur it is rather common, provided the terrain is mountainous or hilly and covered with vegetation. There it lives under moss or rotten leaves, in the roots of old trees, in the cracks and clefts of the ground, of rocks or of ruins of buildings ; Vv SALAMANDRINAE 117 in default of anything better under heaps of stones, or in the holes dug by mice or moles. One chief necessity for its happiness is moisture. The salamander does not occur everywhere, but is rather local. On certain kinds of limestone it is rare or absent ; granitic terrain and red sandstone seem to suit it best, for instance the Hartz Mountains, Thuringia, and Heidelberg are favourite localities. But even there we may spend days and weeks and never come across a single specimen. We may turn stones, rake up the moss and leaves, pry into cracks, and we unearth perhaps. afew sorry-looking, listless, dull and dry, half-emaciated creatures. The same place after a thunderstorm will be literally swarming with sleek, lively salamanders, in search of earthworms and all kinds of insects, especially at dusk or during the night. They disappear in the autumn, in October, to hibernate in the ground, out of the reach of frost, and they reappear again in April. Later on they congregate at little springs, always at running water, to reach which they have often to make long migrations. This is the only time when these thoroughly terrestrial creatures approach water, in which they easily get drowned. Although this species is so common its mode of reproduction has been satisfactorily discovered only quite recently. There are some puzzling facts which it took a long time to observe correctly and to interpret. The larvae are born in April, May, or June, while there are no eggs in the oviducts, but in July these are full of fertilised eggs before copulation takes place. This seems contradictory. The explanation is as follows. In July there is an amplexus of the sexes, short, and often on land—a sort of pre- liminary exciting performance. Both sexes then descend into the water, but generally remain on land with the fore part of the body. The male deposits a spermatophore and the female takes part of this into its cloaca. In the case of a virgin female the eggs are fertilised in the oviduct and ripen until the autumn, but the larvae nearly ready for birth remain within the uterus until the following May, i.e. about ten months. The mother then crawls half into the water, mostly at night, and gives birth to from a few to fifty young, fifteen being perhaps the average. The young are surrounded by the egg-membrane, which either bursts before or shortly after expulsion. This species is consequently viviparous in the proper sense. If she produces a few young only, say from 118 URODELA CHAP. two to five, these are much larger and stronger than those of a large litter. Occasionally a few addled or only partly developed eggs are also expelled. In the case of old females which have produced offspring before, the whole process is more complicated. The sperma, taken up in July, remains in the receptaculum of the cloaca until the May or June following, i.e. until the previous larvae have passed out of the uterus and are born. Then the spermatozoa ascend to the upper ends of the oviducts, where they meet and fertilise the new eggs. After these have descended into and filled the uterus, and are already developing into embryos, copulation takes place again in July, preparatory for next year’s eggs. The new-born salamanders have three pairs of long external gills, a long tail furnished with a broad dorsal and ventral fin, and four limbs, although these are small. The total length is about 25 mm. or 1 inch. The general colour is blackish with a pretty metallic golden and greenish lustre. The little creatures are very active, and at once eat living or dead animal matter. In captivity they are liable to nibble each other’s gills and tails. During the first six or eight weeks they assume a row of dark spots on the sides; these spots enlarge, and the whole skin becomes darker. Yellow spots appear next, first above the eyes and on the thighs, later upon the back; the ground-colour at the same time becomes black, until at the beginning of the fourth month they look like the parents. The metamorphosis is very gradual. The tail-fin diminishes first, but the gills grow until shortly before the little creatures leave the water. Darkness, cold, and insufficient food retard the metamorphosis, sometimes until October. It is easy to rear them artificially provided they are well fed, kept in a light place, and in clean, well aerated water. If prevented from leaving the latter, for instance when kept in a glass vessel with vertical walls, or if hindered by a piece of gauze from rising to the surface and taking in air, they can be kept as larvae well into the winter. Very young, perfect little salamanders, of from 1 to 2 inches in length, are excessively rare; even specimens of 3 inches are far from common. They probably spend the first two or three years of their life in careful seclusion. A few adults can be easily kept for many years in shady ¥ SALAMANDRINAE 119 places provided with moss, rotten stumps and stones, to afford them suitable moist and cool hiding-places, and they readily take earthworms, larvae of beetles, snails, woodlice, etc. But any attempt to keep them in large numbers ends in failure. They con- gregate together in cluinps, all making for the same cavity or recess, as if that were the only one in existence (very likely they are right in so far as that place is probably the: best), and they get rapidly enlarging sores, chiefly on the elbows and knees. These are soon infested with fungoid growths, and this disease spreads like an epidemic and soon carries them off. S. atra—The Alpine Salamander differs from the Spotted Salamander by its uniform black colour and smaller size, which averages between 7 and 5 inches. It is restricted to the Alps of Europe, from Savoy to Carinthia, at from 2000 to as much as 9000 feet, elevation, living with predilection near waterfalls, the spray of which keeps the neighbourhood moist, or in mossy walls, in the shade of forests near brooks, or under flat stones on northern slopes. The most interesting feature of this species is that it produces only two young at a time. These are nourished at the expense of the partially developed eggs in the uterus, and they undergo their whole metamorphosis before they are born. By far the best and most complete account of this mode of propagation has been given by G. Schwalbe.’ The length of the ripe embryos is about 45 mm.; they lie mostly bent up, with their heads and tails turned towards the head of the mother. The gills are beautiful, delicate red organs, the first pair being generally directed forwards and ventralwards, the second upwards, the third backwards; they are longest when the creature is about 32 mm. long, while there is still much yolk present. At this stage the gills are so long as to envelop nearly the whole embryo. There is rarely a second embryo in the same uterus, and an extra foetus is generally smaller, frequently a monstrosity not fit to live; it is probable that it is not used as food, but that it is expelled at parturition. The embryo passes through three stages, (1) still enclosed within its follicle and living on its own yolk, (2) free within the vitelline mass which is the product of the other eggs, (3) there is no more vitelline mass, but the embryo is possessed of gills 10-12 mm. in length, and is still growing. During the 1 Zeitschr. Biol. xxxiv. 1896, pp. 340-396. E20 URODELA CHAP, second stage the yolk is directly swallowed by the mouth. The walls of the maternal uterus are rather red. The ex- change of nutritive fluid takes place through the long external gills, which thereby function in the same way as the chorionic villi of the Mammalian egg. Lach gill contains a ventral artery and a dorsal vein, each of which looks like the midrib of a pinnate leaf; there is also a fine nerve and a weak bundle of striped muscular fibres. Hach gill-filament receives a capillary artery which extends to the epithelium of the tip, where it turns into a capillary vein. The epithelium of these filaments, which are full of blood, is ciliated, the resulting current being directed from the base towards the tip. In older larvae this ciliation becomes restricted to the tips. The body of the vills is furnished with flat epithelium, these non-ciliated portions alone are closely appressed to the uterine wall, and it is here that the exchange of gas takes place between mother and larva. The nutrition takes place through the gills, as they are bathed by the yolk- mass, Schwalbe also explains the whole question of the reduction of the number of embryos. He says rightly that in S. maculosa, which gives birth to many young, there are in the oviduct many eggs which have only partly developed into embryos, and these, perhaps from want of room and nourishment, degenerate into the irregularly shaped whitish-yellow bodies which are occasionally found packed in between the developing embryos. Consequently all those eggs had been fertilised near the ovaries. S. atra exhibits a further stage in so far as most of the eggs, fertilised above in the oviduct, degenerate, and only two or three become fully developed. These few embryos live on the degenerating eggs, which together produce the vitelline material spoken of above. The two full- grown and metamorphosed embryos, each measuring about 50 mm. in length, are equivalent to the numerous new-born larvae ot S. maculosa, especially if the smaller size of the adult Alpine Salamander is taken into consideration. Mlle. von Chauvin * has experimented with the unborn larvae of this Salamander. She cut out 23 larvae and put them into water. One of them, already 43 mm. long, took earthworms on the next day, and the beautiful long, red gills became pale and shrunk, and on the third day were cast off close to the ) Zeitschr. wiss, Zool. xxix. 1877, pp. 824 f., pl. xxii. v SALAMANDRINAE 121 body. New gills sprouted out on the same day, first in the shape of three tiny knobs on either side. After three weeks they had become round globes, which yradually sprouted out into several branches, far shorter and more clumsy than the original gills. During the whole time the larva was lying quietly at the bottom, in the darkest corner, but showed a good appetite. The fin of the tail disappeared and was supplanted by a stronger one. In the sixth week the skin was shed in flakes, and this process took fifteen days. This larva lived in the water for fourteen weeks and grew to 6 cm. in length! When the new gills gradually shrank, the compressed and finny tail assumed a round shape, the skin became darker and shinier, and after the larva had again shed its skin, there appeared the dark 1ugose skin of the typical S. atra. The gills were reduced to useless appendages—not cast off—and the creature crawled out of the water.