half of the uro-proctodaeal fold, near which open the male ducts. Very young crocodiles possess a typical middle chamber or urodaeum, into the dorso-lateral corners of which open the ureters, but soon the strong circular fold between urodaeum and coprodaeum disappears completely, so that both chambers now form one large oval room, which is used solely for the storage of the urine, there being no bladder. The faeces are kept in the not specially dilated rectum.

The cloacal arrangement of the Chelonia is a further development of early crocodilian conditions, but it has become rather complicated and shows a surprising resemblance to that which still prevails in the Monotremes. The proctodaeum is deep and very long, especially in the males. From its innermost and ventral walls arises the large copulatory organ. From the urodaeum is separated off a deep ventral recess into which open the ureters and the genital ducts, and it is continued by a long neck into the large bladder. Between the dorsal wall of this recess and the ventral wall of the main portion of the urodaeum arises a horizontal fold which, diverging, is continued on to the investing skin of the penis, helping to form the edges of the deep longitudinal furrow on its morphologically dorsal surface. If the lips of this furrow were closed, urine and all the genital products would pass through this urethral canal, but in reality only the semen is conducted through it (the furrow during the state of turgescence being transformed into a closed tube), whilst urine and eggs escape through the wide slit near its inner end. This is an arrangement almost the same as that of Ornithorhynchus. The urodaeum is separated from the rectum by a strong sphincter, and there is, as in the crocodiles and mammals, no special coprodaeum. The Chelonian urodaeum is further complicated by the occurrence of a pair of large anal sacs, thin-walled diverticula on the dorsal side. Such sacs, not to be confounded with the anal glands of other reptiles, exist in many water tortoises, especially in the Chelydidae, also in various aquatic Testudinidae, e.g. Emys, in Platysternum, and sometimes in Trionyx; they are absent in the Chelonidae and in the typically terrestrial tortoises. These sacs have highly vascularized walls and a considerable layer of circular and longitudinal non-striped muscular fibres; their inside is sometimes villous, never glandular. They are incessantly filled and emptied with water through the vent, and act as additional respiratory organs, like a kind of water lungs. When such a tortoise is suddenly taken out of the water it squirts out a stream of water, which is not, as is usually supposed, the urine from the bladder.

In connexion with the cloaca may be mentioned the frequent occurrence of peritoneal canals. In the tortoises their abdominal openings are situated in a recess of the peritoneal cavity close to either side of the neck of the bladder; in the females they extend as funnels, generally blind, into the cloaca on or near the base of the clitoris. In the males they extend, without having communication with the cavities of the corpora cavernosa, and without ramifications, as canals along the dorsum penis and either terminate blindly in the glans (Testudo, Chelone), or they open, each by a small orifice, in the groove at the base of the glans. In crocodiles these canals are short and open near the base of the copulatory organ, protected by a small papilla. They are present in both sexes, but are still closed in newly hatched and very immature specimens. In an adult Nile crocodile they are wide enough to pass an ordinary lead pencil. The function of these outlets from the body cavity is obscure. In Sphenodon the writer has found them as closed funnels which project as soft papillae into the proctodaeum a little to the right and left and caudalwards from the urino-genital papillae.

Urinary Organs.

The kidneys of the reptiles show, like those of the birds and mammals, a considerable advance upon those of the Batrachia. They are, in the adult, represented entirely by the metanephros; the segmental tubes have no longer any nephrostomes opening into the body cavity, not even during any time of their development, and it has come to a complete

separation of the efferent genital ducts from the kidneys and from their ureters. Yet these differences are but of degree, there being a continuous bridge from Batrachian to Lacertilian conditions. In Lacerta, for instance, in which these features have been studied most thoroughly, the mesonephros continues as the only functional excretory organ during the first year of the young creature until and during its first hibernation, when the formation of the metanephros takes place, and with it the complete separation of the vasa deferentia from the kidneys. Until then the segmental canals remain in the male as common carriers of semen and urine, at least morphologically, not physiologically, since in the immature there is no occasion for the conduction of semen. The kidneys of these young lizards show precisely the same arrangement as that of the Batrachia, excluding the Discoglossidae."

Clearly the metanephros is developed from, and is part of, the posterior portion of the mesonephros, the glomeruli of which no longer open into the segmental duct, but become connected with a new canal, the future ureter, which sprouts from the distal portion of the segmental duct and grows headwards. Or let us put these important changes in another way. Since there are originally several segmental ducts (permanent in the male newt) which tailwards more and more lose their connexion with the testes, until-in the posterior portion of the mesonephrosthey become entirely urinary ducts, the hindmost of these sprouts (in lizards postembryonic, much earlier in birds and mammals) independently, but at the same time as the neighbouring mass of the mesonephros, the growing glomeruli of which then connect with the sprouting processes of the ureter. Phylogenetically and ontogenetically it is evident enough that the kidneys are essentially one organ, the anterior portion of which is the oldest and decays, whilst farther backwards new and more differentiated portions continue to grow. Pro-, mesoand metanephros are successive wave-like stages of the same organ with morphological and functional continuity, until the next, improved portion is ready. It is important that in the. Discoglossidae, especially in the male Alytes, an arrangement has come to pass which much resembles that of the Amniota. The mesonephros has, by a simple contrivance, become a metanephros, provided we define the former as a kidney which is still connected with true segmental ducts.

The supra-renal bodies, adrenals, head-kidneys or Nebennieren, are yellowish bodies which lie more in connexion with the generative glands than with the kidneys, always closely attached to the vena cava posterior just above the kidneys. They are very elongated in the snakes, in a 10-foot python they measure about one inch in length; they are flattened in tortoises, roundish in crocodiles.

In all reptiles the kidneys are retroperitoneal, and they do not project into the body cavity. Their position is different in the various groups, and their general shape is much affected by the shape of the body. In the Ophidia they are much elongated, and of course far in front of the pelvic region, which has been moved to the cloaca. They are placed asymmetrically, the right extending farthest forwards. They consist of many transverse lobes, sometimes in such a way as to appear spirally twisted. Each terminates considerably in front of the cloaca. Each ureter begins at the anterior end of the kidney, and thence proceeds on its inner and dorsal border, receiving ducts from the interspaces of the numerous lobes. In the male each ureter opens upon a papilla, together with the vas deferens; in the female the ureter is joined by a blind canal, the vestige of the male duct. No snake has a urinary bladder. The urinary excretion is white, chalky, consisting mainly of uric acid in crystals, with very little fluid.

In the Lacertilia the kidneys are more posteriorly placed than in snakes. They lie between the pelvis and the cloaca and are generally close together, sometimes partly fused with each other. Only in the Amphisbaenids the right kidney extends more forwards. They are usually transversely furrowed. The ureters open dorso-laterally into the urodaeum upon papillae as in the snakes. In the females the remnants of the segmental

ducts, or vestigial representatives of the vasa efferentia, are often of considerable length, persistent in chameleon and Uromastix, much reduced in geckos, or disappearing with age as in Lacerta. The urine of most lizards contains much solid uric acid, which is retained in the urodaeum and voided as a rather solid, white mass, not united with the faeces. Those which have a greater amount of fluid urine have a bladder which receives the fluid portion. The opening of this bladder is on the ventral side of the cloaca, not in direct connexion with the ureters. The bladder is very rarely absent, e.g. in Varanidae and Amphisbaenidae. The Crocodilia have the kidneys placed below the pelvis; their surface shows meandering convolutions separated by furrows. The ureters are for the greater part of their length deeply sunk into the substance of the kidneys, which they leave near the hinder ends, to run freely for a short distance along the dorsal sides of the cloaca, and they open, each separately, and away from the vasa deferentia, into the dorsal side of the urodaeum, which, together with the coprodaeum, forms a large oval chamber, and this being filled with the very fluid urine, functionizes instead of the absent bladder.

In Chelonia the kidneys lie in the pelvis, short and thick, more or less trihedral; the surface is marked with many shallow meandering grooves and fewer deeper furrows. Each ureter, composed of several large successive canals, leaves its kidney near the inner hinder end, and then runs free for a short space, crossing the gut to open into the neck of the urinary bladder, which arises ventrally out of the urodaeum, which itself has become a recess of the cloaca. The bladder is large, often more or less two-horned, attached to the pelvic wall by a peritoneal fold, and it contains very fluid urine.

The kidneys of Sphenodon are very small and far removed from the generative organs. The ureters open, each close to the vas deferens of its side, beneath a little papilla, on the dorsal side, rather near the midline of the urodaeum, whence arises a long-necked bladder.

Reproductive System.

The Ovaries are always in pairs, placed headwards at a distance from the kidneys in Sphenodon, lizards and snakes; in the latter the right ovary lies farther forward. In tortoises, and especially in the crocodiles, where they are very long and much twisted or lobated, they are situated close to the kidneys and even accompany them. The ovaries of lizards and snakes contain many and large lymph spaces; those of the other reptiles are much denser in structure. The ripening eggs always cause them to assume the shape of a bunch of grapes. The oviducts are each held by a peritoneal fold which arises from near the dorsal midline. The abdominal ostia are long slits and are turned towards the side, away from the ovaries. The walls of the ducts gradually become thicker, glandular and much folded. Whilst the ripe eggs, often in considerable numbers, receive their shell, each egg lies in a separate chamber; in the geckos, which lay only one pair of eggs, the two respective chambers have become permanent features. In Sphenodon each oviduct opens together with the ureter of its side near the dorsomedian line of the urodaeum. In most lizards the two oviducts and the two ureters have four separate openings in the dorsal wall of the rather deep dorsal recess of the urodaeum. But in Lophura both oviducts unite (like the ureters) and have only one opening, which is placed a little nearer towards the pelvis than the urinary opening, but they are divided by a longitudinal septum which extends almost to their common orifice. In the snakes the oviducts likewise open into the dorsal recess, sometimes by a common ostium, which is provided with a strong sphincter. The whole recess acts like a vagina for the reception of one of the copulatory organs. The oviducts of the crocodiles open in a decidedly ventral position, on either side close to the base of the clitoris, a considerable distance from the openings of the ureters. In the tortoises the oviducts open separately into a wide ventral urino-genital sinus, at the base of the neck of the bladder.

The Testes correspond in position with the ovaries; in snakes and Amphisbaenids the right is placed farther head

wards than the left. The usual shape is elongated, sometimes pointed forwards. The Epididymis is sometimes of the same size as the testis and then consists of many meandering convolutions of the vas deferens which is composed of several canals from the testis. The convolutions are held together by a peritoneal lamella. Towards the cloaca they become much smaller and shorter, and the vas deferens passes along the median side of the ureter. In Sphenodon these open separately, each near and below the same papilla near which opens the ureter of the same side. In most lizards the vas deferens unites with its ureter into one short canal which opens beneath or upon a small papilla in the upper corner of the urodaeal recess, far away from the penis. In snakes vas deferens and ureter of each side are likewise commonly united. In the crocodiles each vas deferens passes from the dorsal side of the cloaca to the ventral side, not accompanied by the ureter, and opens into the blind sac which forms the basal continuation of the deep groove on the dorsal side of the penis. In the tortoises the epididymis is very large and the vas deferens is also much convoluted; each opens separately near the neck of the large urinary bladder close to the backward continuation of the deep longitudinal groove of the copulatory organ.

Remnants of the Müllerian ducts run parallel with the vasa deferentia, and similar remnants of the Wolffian ducts accompany the oviducts in crocodiles and tortoises, least degenerated of course in young specimens. Such reciprocal vestiges occur most likely also in lizards, and in female snakes a vestige of the male duct joins its ureter. In a nearly adult male Sphenodon the present writer missed the female remnants.

a

pa

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The copulatory organs show very important modifications. Sphenodon is the only recent reptile which is devoid of such an organ; its imperfect substitute is an unpaired, thin, but high membranous fold which arises from the dorsal middle of the circular fold between urodaeum and coprodaeum. During copulation this part of the cloaca is probably everted to secure conception, a striking resemblance to the arrangement found in the Caecilia. The organs of all lizards and snakes are paired, in their quiescent state withdrawn into deep pockets which open on the right and left posterior corners of the proctodaeum or outer chamber of the cloaca, which for this reason has assumed the shape of transverse slit in all lizards and snakes. Hence these have sometimes been called Plagiotremata. Each organ can be everted and tucked in like the finger of a glove, a muscle being attached to the inside of the apex ; when everted, the muscle extends through the length of the organ; each muscle arises from the ventral side of several transverse processes of the tail FIG. 39.-Male copulatory organs of Lacerta agilis (after Leydig). P1, P2, vertebrae, at a considerorgans of right and left sides able distance from the between them is the anal aperture; cloaca. In the embryo each pp, preanal plate. organ arises as a conical protuberance, or papilla, which projects out of the vent. Later it becomes inverted. Probably this ontogenetic feature recapitulates the phylogeny of these organs, which have to be looked upon as swelling flaps or portions of the walls of the cloaca which were protruded during copulation, and which in time borrowed, and specialized, muscular fibres from the ventral tail muscles. On the outer everted side of each organ is a furrow for the reception of the semen. The apex is either single or more or less deeply bifurcated, each arm being followed by the likewise divided furrow. The outer investing membrane of these very muscular erectile bodies is epidermal; often, especially in snakes, provided with numerous papillae, folds or other excrescences.

XXIII. 6 a

In

many snakes these are spiny and hard, but according to Leydig this hardness is not due to a horny substance but to the deposition of calcifying matter. E. D. Cope has investigated the almost endless minor modifications of these penial features and uses them for taxonomic purposes in the snakes. Vestiges of these organs occur in females of snakes and lizards. Close to these organs of the snakes lies a pair of anal glands of some size, which pour their very offensive secretion through an opening close to the base of each penis. The same glands occur in the same position in Sphenodon, which has no copulatory organs, and in crocodiles they appear as evertible musk glands. Hence Hence J. E. V. Boas, not knowing of their existence in both sexes of snakes, tried to homologize them with the paired penes of reptiles, an error which has been repeated in C. Gegenbaur's Lehrbuch, vol. ii. p. 533.

The crocodiles and tortoises possess a single, median copulatory organ; it lies on the ventral or anterior end of the cloaca, the outer opening of which is therefore a longitudinal slit, hence the term Orthotremata. In the crocodiles the organ is attached to the caudal corner of the ischiadic symphysis by a strong and roundish fibrous band, which arises single from the ventral sides and forms partly the continuation of the two fibrous halves of the organ; the bulk of the crura, comparable to corpora cavernosa, is not attached to the pelvis, as generally stated, but projects backwards towards and into the pelvic cavity. This portion is especially rich in venous cavernosities. The outer coating of the glans possesses various papillary projections, which are furnished with sensory, hedonic corpuscles. On the morphologically dorsal side of the organ, not on the dorsum penis, is a deep groove which ends towards the crura in a blind sac, into the farther corner of which open the vasa deferentia. In a full-grown Nile crocodile the whole organ is about 10 in. long. In young females up to a total length of 3 or 4 ft. the clitoris is nearly of the same size as the male organ, but it remains stationary and appears very small in large specimens.

The organ of the tortoises is essentially of the same type as that of the crocodiles, but it is nowhere directly attached to the pelvis or to any other skeletal part. The whole organ, when withdrawn, lies in a ventral, long recess of the wide outer cloacal chamber, and its crura extend so far back as to form the continuation of the ventral and lateral walls of the recessus which is continued into the neck of the urinary bladder. Its orifice and those of the seminal ducts are enclosed by the walls of the deep groove which runs along the underside of the organ. This is always of considerable size, surprisingly large in Trionyx. The clitoris is small, sometimes tiny.

The sexual act is extremely prolonged in Chelonians and still more so are the preliminaries, but in crocodiles it is the deed of a few seconds. Lizards and snakes insert only one side.

There remains the question whether the unpaired organ of the crocodiles and tortoises, which is the prototype of the mammalian organ in every essential point, and the paired organs of the lizards and snakes, are to a certain extent homologous organs in so far as they can both be derived from the same indifferent condition. With this view we assume that originally the protrusible walls of the outer cloacal chamber became specialized into a right and left imperfect intromittent organ, that subsequently, in lizards, those hemipenes were shifted back towards the tail and were henceforth bound to develop separately, while in the crocodiles, tortoises, mammals and birds the two primitive lateral evertile flaps approached each other towards the ventral anterior side of the cloaca, and that this led to a fusion, beginning probably at the basal part, which at the same time was farther withdrawn from the surface and secured the reception of the sperma from both vasa deferentia into one canal. This hypothesis has been objected to by Boas, but accepted by Gegenbaur (p. 538) after having been rejected on p. 533 of his Lehrbuch.

The Fat bodies belong at least physiologically to the generative system. They are placed outside the peritoneum. In

lizards they appear as two masses in the pelvic region, the black peritoneal lining covering only their dorsal side. They consist of a network of arteries and connective tissue, the meshy spaces of which are filled with "fat"; they each receive an artery from the femoral vessel which enters them in the inguinal region; the veins collect into the abdominal. In snakes the fat bodies are very long, extending from the cloaca to the liver. Tortoises seem to have only traces of them, but in Sphenodon and in crocodiles they resemble those of lizards.The peculiar organ suspended from the right abdominal wall of crocodiles, variously mentioned as mesenteric gland or body, or fatty spleen, by Butler, is possibly related to the same category. The fat bodies of reptiles are sometimes vaguely alluded to as hibernating bodies; like the fat bodies which are attached to the generative glands of Amphibia they do not become reduced during the eventual hibernation but are largest before the pairing season, by the end of which they are exhausted, looking reddish or grey after the loss of their stores of fat and probably other important contents.

The Embryonic Development.

Fertilization of the egg always takes place internally, and the egg containing a large amount of food-yolk is of course meroblastic. It is sufficient to mention that many lizards, some chameleons and many snakes (not Sphenodon, geckos, crocodiles and Chelonians) retain their, in these cases very thin-shelled, eggs in the oviducts until the embryo is ready to burst the egg-membrane during the act of parturition or immediately after it. Such species are usually called ovoviviparous, although there is no difference between them and other viviparous creatures, for instance the marsupials. The majority of reptiles are oviparous and the egg is enclosed in a strong parchment shell, with or without calcareous deposits. Only gas exchange can take place between such an egg and the outside, and it loses by evaporation, whilst in the batrachian egg various other exchanges are easy through the thin membrane. The salamander embryo, within its thin egg-membrane, even grows to a size many times larger than the original egg, it does not only breathe, but it is also nourished through the gills, and by some means or other the waste products are partly eliminated without filling the bladder. The amphibia are born as larvae and live as such for a long time, often in a most imperfect condition. Nothing of all this applies to the reptile, which leaves the egg as a perfect little imago. A great amount of yolk supplying the material, and a large "bladder " to receive the waste products and to act as respiratory organ, have made this possible. That the allantois and the amnion behave precisely in the same way in the mammals with their much reduced yolk, only testifies to the superior value of these organs, and after all there is no difference in this respect between a monotreme and a reptile. These two organs seem to have come into existence with the reptiles and constitute the most reliable diagnostic feature between higher and lower vertebrates. All reptiles, birds and mammals have a navel, a feature unknown and impossible in Batrachia and fishes. A few remarks on these important embryonic organs may not be superfluous, especially concerning their possible origin.

Whilst the urinary bladder of the Batrachia remains within. the body throughout the embryonic stage, this organ undergoes in the higher vertebrates, reptiles, birds and mammals, considerable modifications, and it assumes, henceforth as Allantois, new important functions besides that of being the receptacle of the embryonic urine. The development of the Allantois is in intimate causal connexion with that of the Amnion. All the Allantoidea are also Amniota and vice versa, but the term Amniota is preferable, since the basal portion of the Allantois remains in the adult as the urinary bladder, as an organ henceforth equivalent to and homologous with that of the Anamnia. The primary feature seems to be the allantois which leaves the body cavity, remains without the amniotic folds, even after these have enclosed the body within the amniotic bag, and

then spreads nearly all over the inner side of the egg-shell. Having thus come into the closest possible contact with the atmospheric air, the vessels of the allantois can exchange their carbon dioxide for oxygen and the allantois becomes the respiratory organ of the embryo. Herewith stands in direct correlation the complete absence of any internal and of external gills in the embryonic reptiles. The blood vessels of the allantois are fundamentally the same as those of the batrachian bladder, namely, branches from the pelvic arteries (later hypogastrics) and veins which return from the base of the bladder to the abdominal wall and thence to the liver.

In the normal reptilian egg, surrounded by its non-yielding shell, space is absolutely limited, and whilst the yolk is being diminished and increased secretion of urine distends the bladder, this soon protrudes out of the body cavity proper into the extra-embryonal coelomatic space between the true amnion and the false amnion or serous membrane. It fills this space so far as the yolk-sac allows it. It seems reasonable to suppose that this growth of the allantois has been one of the causes of the caudal amniotic fold; the sinking of the embryo into the space of the diminishing yolk-sac is no doubt another cause, but the fact remains that the amnion is the chief hindrance to the closing of the body-wall at the region of the future navel. The life-histories of embryonic development are the domain of the embryographers. They are the imperfect accounts of the ways and means (often crooked and blurred, owing to short cuts and in adaptation to conditions which prevail during the embryonic period) by which the growing creature arrives at those features which form the account of the anatomical structure of the adult. Comparative anatomy, with physiology, alone lead through the maze of the endless embryonic vagaries and afford the clues for the reconstruction of the real life-history of an animal and its ancestry. For detail the reader is referred to numerous papers quoted in the list of literature, and to the various text-books, above all to the Handbuch d. vergleichenden Entwicklungsgeschichie d. Wirbelthiere, edited by O. Hertwig,

Berlin.

AUTHORITIES ON ANATOMY. Bibliography.-The appended list of papers (many with shortened titles) represents but a fraction of the enormous literature dealing with the anatomy of reptiles. Special stress has been laid upon the more recent publications. A great amount of information, general and detailed, is contained in Bronn's Klassen u. Ordnungen d. Thierreichs, the three volumes concerning reptiles having been written by C. K. Hoffmann (Leipzig, 1878-1890); E. D. Cope's Crocodilians, Lizards and Snakes of North America, U.S. Nat. Mus., Washington, 1900; H. Gadow's Amphibia and Reptiles," vol. xiii. of The Cambridge Natural History (London, 1901); above all in C. Gegenbaur's Vergleichende Anatomie d. Wirbelthicre (Leipzig, 1898–1901).

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Skeletal.-J. F. v. Bemmelen, "Schaedelbau v. Dermochelys coriacea," Festschr. f. Gegenbaur (1896); E. Gaupp, "Morphologie d. Schaedels," Morpholog. Arbeiten (1894), iv. pp. 77-128, pls.; ibid. ("Problems Concerning the Skull"), Anat. Ergebn. (1901), x. pp. 8471001. W. K. Parker," Skull of Lacertilia," Phil. Trans. 170 (1880), pp. 595-640, pls. 37-45; "of Tropidonotus," ibid. (1879), 169, pp. 385-417, pls. ; Crocodilia," Trans. Zool. Soc. (1885), xi. pp. 263-310, pls. Chamaeleons," ibid. (1885), xi. pp. 77-105, pls. 15-19. F. Siebenrock, Kopfskelet d. Scincoiden, Anguiden u. Gerrhosauriden," Ann. Nat. Hofmuseum (Wien, 1892), vii. 3. Of the enormous, still increasing, literature concerning the homologies of the auditory ossicles, a few only can be mentioned; the papers by Kingsley and Versluys contain most of the previous literature: W. Peters, several most important papers in Monatster. Ak. Wiss. (Berlin, 21st Nov. 1867, 5th Dec. 1867, 7th Jan. 1869, 17th Jan. 1870, 15th Jan. 1874). H. Gadow, "Modifications of the First and Second Visceral Arches, and Homologies of the Auditory Ossicles," Phil. Trans. 179 (1888), B. pp. 451-485, pls. 71-74; 'Evolution of the Auditory Ossicles," Anat. Anz. (1901), xix. No. 16. J. Versluys, "Mittlere u. äussere Ohrsphäre d. Lacertilia u. Rhynchocephalia,' Zool. Jahrb. Anat. (1898), 12, pp. 161-406, pls. (most exhaustive and careful); ibid., Entwickl. d. Columella auris b. Lacertiliern,' ibid. (1903), 18, pp. 107-188, pls. J. Kingsley, The Ossicula auditus," Tufts College Studies, No. 6 (1900). E. Gaupp," Columella auris," Anat. Anz. (1891), vi. p. 107. T. H. Huxley, The Representatives of the Malleus and Incus of the Mammalia in the other Vertebrata," P.Z.S., 1869. W. K. Parker, Struct. and Development of Crocodilian Skull," Trans. Zool. Soc. (1883), xi., especially pls. 68 and 69. H. Gadow, "Evolution of the Vertebral Column of Amphibia and Amniota," Phil. Trans. (1896), 136, pp. 1-57 (with a list of ninety-three papers). G. B. Howes and H. H. Swinnerton,

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W Development of the Skeleton of Sphenodon," Trans. Zool. Soc. (1901), xvi. pp. 1-86, pls. 1-6. G. A. Boulenger, Catalogue of Chelonians, Rhynchocephalians and Crocodiles, Brit. Mus. 1889; Cat. of Lizards (3 vols., 1885-1887); Cat. of Snakes (3 vols., 18931896); these volumes contain a great body of osteological observations, ignored by most compilers of anatomical text-books; Osteol. of Heloderma, and Vertebrae cf Lacertilia," P.Z.S., pp. 109-118 (1891). L. Calori, Skeleton of Varanus, Lacerta,' Mem. Acc. Sci. Instit. Bologna (8, 1857, and 9, 1859). E. D. Cope, Osteology of Lacertilia," Proc. Am. Phil. Soc. (1892), 30, PP. 185-221; Degeneration of Limbs and Girdles, Journ. Morph. (1892), vii. pp. 223-244. E. Ficalbi, Osteologia del Platidattilo (Pisa, 1882). A. Goette, Beitrage z. Skeletsystem," Arch. Hatteria," Phil. Trans. (1867), 157, PP. 595-629, pls. micr. Anat. (1877), 14, PP. 502-620. A. Günther, Anatomy of S. Orlandi, Note anatomiche s. Macrosincus," Atti S. Lig. (Geneva, 1894), v. 2; Skelet d. Scinc. Anguid. Gerrhosaurid," Ann. Naturhist. Hofmus. (1895), x. pp. 17-41; Skelet d. Agamidae," Sitzb. Ak. wiss. Wien, (1895), 104, pp. 1089-1196. F. Siebenrock, Skelet v. Brookesia," Sitzb. Ak. Wiss. Wien (1893), 102, pp. 71-118; Skelet v. Uroplates," Annal. Naturhist. Hofmuseum (1892), vii. pp. 517-536, 1893; "Skelet d. Lacertiden," Sitzb. Ak. Wiss. Wien (1894), 102, Pp. 203-292. C. Smalian, "Anat. d. Amphisbaenid," Zeitschr. wiss. Zool. (1885), 42, pp. 126-202. A. Voeltzkow, Biolog. u. Entwickl. von Crocodilus," Abh. Senckenb. Ges. (1899), 26, pp. 1-150, 17 pls. E. A. Case, "Osteology and Relationships of Protostega," Journ. Morph. (1897), xiv. pp. 21-60. H. Goette, "Entwickl. des Carapax d. Schildkroeten," Zeitschr. wiss. Zool. (1899), 66, pp. 40-434, pls. O. P. Hay, Morphogeny of Chelonian Carapace, Amer. Nat. (1898), 32, pp. 929-948. G. Baur, "Morphol. Unterkiefer d. Rept.," Anat. Anz. (1896), xi. pp. 410-415. M. Fürbringer, "Brustschulterapparat und Schultermuskeln. Reptilien," Jena Zeitschr. (1900), 34, pp. 215-718, pls. 13-17 (with a list of many titles of papers concerning reptiles; and a new, unsatisfactory classification of the whole class). C. K. Hoffmann, Becken d. Amphib. u. Reptil.," Niederl. Arch. f. Zool., iii. E. Mehnert, Beckenguertel d. Emys lutaria,' Morph. Jahrb. (1890), 16, pp. 537-571, pl. ; "Os hypoischium, &c. d. Eidechsen," Morph. Jahrb. (1891), 17, pp. 123-144, pl. W. K. Parker, Shoulder Girdle and Sternum," Roy. Soc. London, 1868. A. Rosenberg, Development of Skeleton of Reduced Limbs," Zeitschr. wiss. Zool. (1873), 23, pp. 116-170, pls. A. Sabatier, Comparaison des ceintures et des membres ant. et post," Mém. Ac. Montpellier (1880), xix. C. Gegenbaur, Untersuch. z. verg. Anat., important monographs). A. Banchi, "Parafibula," Monitore Zool. I. Carpus u. Tarsus" (1864), II. "Schulterguertel" (1865) (the most Italiano (1900), xi. No. 7 (A nodule ][ between femur and fibula in Lacerta). G. Baur, " Carpus u. Tarsus d. Reptil.," Anatom. An eig. iv. No. 2. G. Born, Carpus u. Tarsus d. Saurier," Morph. Jahrb. (1876), 2, pp. 1-26, pl. A. Carlsson, "Gliedmassenreste bei Schlangen, Svensk. Vetensk. Ac. Handlingar, ii. (1886). A. Johnson, Development of Pelvic Girdle," Q.J.M.S. (1883), 23, pp. 399-411, G. Kehrer, Carpus u. Tarsus," Ber. Naturf. Ges. (Freiburg, i. 1886). W. Kuekenthal, Entwickl. d. Handskelets des Crocodiles," Morph. Jahrb. (1892), 19, pp. 42-55. H. F. Sauvage, "Membre antérieur du Pseudopus," Ann. Sci. Nat.-Zool. 7. art. 15 (1878). A. Stecker Carpus u. Tarsus bei Chamaeleon," Sitzb. Ak. Wiss. (1877), 75, 2, pls. R. Wiedersheim, Gliedmaṣṣen skelett., Schulter. u. Beckenguertel (Jena, 1892). K. Baechtold, Über die Giftwerkzeuge der Schlangen (Tübingen, 1843). A. Dugès, Venin de l'Heloderma," Jubil. Soc. Biol. (1899), PP. 34-137. D. F. Weinland, On the Egg-tooth of the Snakes," Proc. Essex Institute (Salem, 1856); and in Württemb. Jahresheft, Verein vaterl. Naturk. (1856). G. S. West, "Puccal Glands and Teeth of Poisonous Snakes," P.Z.S. (1895), pp. 812-826, pls. 44-46.

"

Tegumentary.-A Batelli, "Bau der Reptilienhaut," Arch. mikr. Anat. (1880), 17, pp. 346-361, pls. J. E. V. Boas, "Wirbelthierkralle," Morph. Jahrb. (1894), xxi. pp. 281-311, pls. A. Haase, "Bau d. Haftlappen bei den Geckotiden," Arch. Naturg. (1900), 61, PP. 321-345, pls. R. Keller, 'Farbenwecksel d. Chamaeleons," Arch. ges. Physiol. (1895), 61, pp. 123-168. C. Kerbert, Haut der Reptilien," Arch. mikr. Anat. (1876), 13, pp. 205-262. F. Maurer, Epidermis und ihre Abkoemmlinge (Leipzig, 1895). F. Schaefer, "Schenkeldruesen d. Eidechsen," Arch. Naturg. (1902), 68, pp. 27-64, pls. F. Todaro, Ricerche f. nel labor. di anat. norm. di Roma (1878), II. I. F. Toelg, Drüsenartige Epidermoidalorgane d. Eidechsen u. Schlangen," Arb. Zool. Inst. Wien (1904), 15, PP. 119-154. pls.

Nervous System.-J. F. Bemmelen, "Beitr. Kenntniss d. Halsgegend bei Reptilien Mededeel," Natura Artis Magistra (Amsterdam, 1887). L. Edinger, Zwischenhirn d. Reptilien," Abh. Senckenb. Ges. (1899), 20, pp. 161-197, pls. J. G. Fischer, "Gehirnnerven d. Saurier," Abhandl. Naturwiss. Verein, Hamburg, II. (1852), pp. 115-212 (with many excellent illustrations). M. Fürbringer, Spinooccipital Nerver," &c., Festschr. f. Gegenbaur, iii. (1896). S. P. Gage, Brain of Trionyx," Proc. Am. Micr. Soc. (1895), xvii. pp. 185-222. E. Gaupp, Anlage d. Hypophyse b. Sauriern,' Arch. mikr. Anat. (1893), 42, pp. 569-680. Giuliani, “Struttura d. midolla spinale d. Lacerta viridis,' Ric. Lab. di Anat. Roma, ii. J. Grimm, "Rückenmark v. Vipera berus," Arch. Anat. Phys. (1864),

pp. 502-511, pl. 12. C. L. Herrick, "Brain of Certain Reptiles," Journ. | comp. Neurol. (1891), i. pp. 1–36, iii. (1893), pp. 77-106, 119-140, with many plates. O. D. Humphry, "Brain of Chelydra." Journ. comp. Neurol. (1894), pp. 73-116. H. v. Jhering, Das peripherische Nervensystem (4to, Leipzig, 1873), pls. St G. Mivart and R. Clarke, "Sacral Plexus of Lizards, &c.," Trans. Linn. Soc. Zool. i. (1877), PP. 513-532, pls. 66, 67. H. F. Osborn, "Origin of the Corpora callosa," Morph. Jahrb. xii. pp. 530-543. H. Rabl - Rückhard, Centralnervensystem d. Alligator," Zeitschr. wiss. Zool. (1878), xxx. pp. 336-373, pls. 19 and 20. "Python," ibid. (1894), lviii. pp. 694-717, pl. 41. G. Ruge, "Peripher. Gebiet. d. N. facialis" (masticator muscles, &c.), Festschr. f. Gegenbaur (1896), iii. L. Stieda, "Centralnervensystem d. Emys,” Zeitschr. wiss. Zool. (1875), xxv. pp.

66

"

361-408

"

Sense Organs.-R. Hoffmann, “Thraenenwege d. Vögel u. Reptil.," Zeitschr. f. Naturw. (Nat. Verein Sachsen u. Thüring., 1882). C. Röse, "Nasendrüse u. Gaumendrüsen d. Crocodils,' Anat. Anz. (1893), viii. pp. 745–751. C. Ph. Sluitez, "Jacobson's Organ v. Crocodilus," Anat. Anz. (1892), vii. pp. 540-545. O. Seydel, "Nasenhöhle u. Jacobson's Organ d. Schildkröten," Festschr. f. Gegenbaur (1896), ii. B. Solger, Nasenwand u. Nasenmuschelw. d. Reptil.," Morph. Jahrb. (1876), i. pp. 467-494, pl. E. Beraneck, Parietalauge d. Rept.," Jen. Zeitschr. (1887), xxi. pp. 374-410, pls.; ibid., Anat. Anz. (1893), No. 20. P. Francotte, L'Eil pariétal, &c. chez les Lacertiliens," Mem. couronné Ac. Belgique (1898), 55, No. 3. H. W. de Graaf, Structure and Development of the Epiphysis in Amph. and Rept. (Leiden, 1886; written in Dutch). W. B. Spencer, Presence and Structure of the Pineal Eye in Lacertilia," Q.J.M.S. (1886), 27, pp. 165-237, 7 pls. H. Strahl u. E. Martin, Entwickl. d. Parietalauges b. Anguis u. Lacerta," Arch. f. Anat. u. Phys. (1888), pp. 146-165, pl. 10. A. Dendy, Development of Parietal Eye of Sphenodon," Q.J.M.S. (1899), 42, pp. 1-87 and pp. 111-153, 13 plates. H. Müller, Schriften z. Anat. u. Physiol. d. Auges, edit. O. Becker (Leipzig, 1872). E. Ficalbi, Palpebralapparat d. Schlangen u. Geckonen,' Att. Soc. Tosc. Pisa, ix. C. K. Hoffmann, "Anatomie d. Retina d. Amph. Rept. u. Vögel. Niederl.," Arch. Zool. (1875), iii. M. Borysiekiewicz, Retina v. Chamaeleo vulgaris (Leipzig, 1889), 7 pls. M. Weber, Nebenorgane d. Auges d. Reptil.," Arch. f. Naturg. (1897), 43. E. Clason, Gehörorgan d. Eidechsen," Anatom. Studien (Leipzig, 1873). C. Hasse, Gehörorgan d. Krokodile," &c., ibid.; Gehörorgan d. Schildkroeten, von Tropidonotus natrix," ibid. G. Retzius, Gehörorgan d. Wirbelthiere, i. (Stockholm, 1881).

"

Muscles.-O. C. Bradley, "Muscles of Mastication of Lacertilia," Zool. Jahrb. Anat. (1902), 18, pp. 475-488. M. Fürbringer, "Vergleich. Anatomie d. Schultermuskeln," Jena Zeitschr. (1873), vii. pp. 237-320; (1874), vii. pp. 175-280; (1900), xxx. pp. 215-718; Morph. Jahrb. (1875), i. pp. 636-816; Knochen u. Muskeln d. schlangenähnlichen Saurier (Leipzig, 1870). H. Gadow, Bauchmuskeln d. Crocod. Eidechs. Schildkroeten," Morph. Jahrb. (1882), vii. pp. 57-100, pl.; "Myologie d. hinteren Extremitaet d. Reptilien, ibid. (1882), vii. pp. 327-466, pls. G. M. Humphrey, "Muscles of Pseudopus," Journ. An. Phys. (1872), vii. G. Killian, "Ohrmuskeln d. Crocodile," Jen. Zeitschr. (1890), xxiv. pp. 632656, pl. F. Maurer, Ventrale Rumpfmuskulatur d. Reptil.,' Festschr. f. Gegenbaur (1896), i. St. G. Mivart, "Muscles of Iguana,' P.Z.S. (1867), p. 766; "of Chamaeleon," ibid. (1870), p. 850. N. Rosén, Kaumuskeln d. Schlangen u. Giftdruese," Zool. Anz. (1906), 28, pp. 1-7. A. Sanders, "Muscles of Platydactylus,' P.Z.S. (1870), p. 413; of Liolepis," ibid. (1872), p. 154; "of Phryrosoma," ibid. (1874), p. 71 ; F. Walther, Visceralskelett u. Muskulatur b. Amph. u. Rept.," Jen. Zeitschr. (1887), xxi. pp. 1-45, pls. Respiratory System.-F. E. Beddard, Trachea and Lungs of Ophiophagus bungarus," P.Z.S. (1903), pp. 319-328. G. Butler, Suppression of one Lung in various Reptiles," ibid. (1895), p. 691. S. H. Gage, Pharyngeal Respiration in the Soft-shelled Turtle," Proc. Am. Ass. Adv. Sci. (1884), pp. 316-318; and Amer. Nat. (1886), xx. pp. 233-236. J. Henle, Vergl. anat. Beschreibung d. Kehlkopfes (1839). F. Siebenrock, Kehlkopf u. Luftroehre d. Schildkroeten," Sitzb. Ak. Wien (1899), 108, pp. 563-595, pls. G. Tornier, Kopflappen u. Halsluftsaecke bei Chamaeleonen," Zool. Jahrb. Anat. (1904), 21, pp. 1-40, pls. D. Bertelli, "Pieghe dei reni primitivi nei Rettili. Contributo allo sviluppo del diaframma," Atti Soc. Toscan (Pisa, 1896), 15, (1898), 16. I. Bromann, Entwicklung d. Bursa omentalis und achnlicher Recessbildungen (Wiesbaden, 1904). G. Butler, Subdivision of Body-cavity in Lizards, Crocodiles and Birds," P.Z.S. (1892), pp. 452-474, 4 pls. ; "Subdivision of Body-cavity in Snakes," ibid. (1892), PP. 477497, pl. 6; "The Fat Bodies of the Sauropsida," ibid. (1889). . 602. pls. 59-60. F. Hochstetter, Scheidewandbildungen in d. Leibeshöhle der Krokodile, Voeltzkow, Reise in Ostafrika, vol. iv. pp. 141-206, pls. 11-15 (Stuttgart, 1906).

Vascular System.-F. E. Beddard, various papers on vascular system of Ophidia and Lacertilia, P.Z.S. (1904); "Notes on Anatomy of Boidae," ibid. (1903), pp. 107-121. F. E. Beddard. and P. C. Mitchell, "Structure of Heart of Alligator," ibid. (1895). A. Greil, 'Herz u. Truncus arteriosus d. Wirbelthiere Reptilien," Morph. Jahrb. (1903), 31, pp. 123-310, pls. O. Grosser and E. Brezina," Entwickl. Venen d. Kopfes u. Halses bei Reptil.,'

"

F. Hochstetter,

Morph. Jahrb. (1895), pp. 289-325, pls. 20 and 21. several important papers on vascular system of reptiles, Morph. Jahrb. (1891, 1892, 1898, 1901); ibid., Blutgefäss - System,' O. Hertwig's Entwickl. d. Wirbelthiere (Jena, 1902); BlutgefaessSystem d. Krokodile," Voeltzkow, Reise in Ostafrika (Stuttgart, 1906, iv.). A. Langer, Entwickl. Bulbus cordis bei Amph. u. Rept.," Morph. Jahrb. (1894), PP. 40-67. J. Y. Mackay, "Arterial System of Vertebrates, homologically considered," Memoirs and Memoranda in Anatomy (London and Edinburgh, 1889), i. B. Panizza, Sopra il sistema linfatico dei rettili (Pavia, 1833). C. Roese, Vergl. Anat. d. Herzens d. Wirbelthiere," Morph. Jahrb. (1890), 16, pp. 27-96, pls. A. Sabatier, Études sur le cœur et la circulation centrale (Paris, 1873); "Transformat. du système aortique," Ann. Sc. Nat. Sev. (1874), 5, J. 19. H. Watney, "Minute Anatomy of Thymus," Phil. Trans. (1882), 173, pp. 1063-1123, pls. 83-95.

Urino-genital System.-J. E. V. Boas, “Morphol. d. Begattungsorgane d. Wirbelth.,' Morph. Jahrb. (1891), xvii. pp. 171-287 pl. 16. J. Budge, "Das Harnreservoir d. Wirbelthiere," Neu Vorpommern, Mittheil. 7, (1875), pp. 20-128, pl. W. R. Coe and B. W. Kunkel, “Reproduct. Org. of Aniella," Amer. Natural. (1904), 38, pp. 487-490. H. Gadow, Cloaca and Copulatory Organs of the Amniota," Phil. Trans. B. (1887), PP. 5-37, pls. 2-5. Hellmuth, Kloake u. Phallus d. Schildkroeten u. Krokodile," Morph. Jahrb. (1902), 30, pp. 582-613. F. v. Moeller, Urogenitalsystem d. Schildkroeten," Zeitschr. wiss. Zool., 65, pp. 573-598, pls. F. W. Pickel, Accessory Bladders of Testudinata," Zool. Bull. (1899), ii. pp. 291-301. F. Schoof, Zur Kenntniss d. Urogenitalsystems d. Saurier. Arch. f. Naturg. (1888), 54, p. 62. Unterhoessel, Kloake u. Phallus d. Eidechsen u. Schlangen," Morph. Jahrb. (1902), 30, pp. 541-581. O. Schmidtgen, "Cloake und ihre Organe bei Schildkröter," Zool. Jahrb. (1907), PP. 357-412, pl. 32, 33. (H. F. G.)

46

IV. DISTRIBUTION IN SPACE

P.

This zoo-geographical review deals only with modern reptiles. We begin with a survey of the faunas of some of the most obvious land-complexes which bear close resemblance to the now classical "regions" of P. L. Sclater and A. R. Wallace. None of these "regions" has definable frontiers, and what acts as a bar to one family may be totally ignored by another. According to the several orders of reptiles the world is mapped out in very different ways. The African fauna does not stop at the Suez Canal, nor even at the Red Sea; there is a transitional belt noticeable in the countries from Syria to Arabia, Persia and India. To the north, Indian influence extends right into Turkestan, or vice versa; the Central Asiatic fauna passes into that of India. On the Chinese side prevailing conditions are still almost unknown; Wallace's line is more or less rigidly respected by Trionychidae, hooded Elaps, vipers and Lacertidae, while it has not the slightest influence upon crocodiles, pit vipers, Varanidae, Agamidae, &c. In the western hemisphere we have a grand illustration of the interchange of two faunas and of the fact that it is neither a narrow strait nor an equally narrow isthmus which decides the limitation of two regions. Central America and the Antilles form one complex with S. America. The nearctic region ends at the edge of the great Mexican plateau, which itself is a continuation of the north continent. Many nearctic forms have passed southwards into the tropics, even into faroff S. America, but the majority of the southerners, in their northern extension, have been checked by this plateau and have surged to the right and left along the Pacific and Atlantic tropical coastlands. The present writer happens to have made a special study of this part of the world (cf. "The Distribution of Mexican Amphibians and Reptiles," P.Z.S., 1905, pp. 191-294); the N. and S. American faunas have therefore been more fully treated in the following review of the various faunas. No doubt others can be treated in a similar manner, but the physical features between N. and S. America are unique, and the results are closely paralleled by those of the fauna of birds. The narrow and long neck of the isthmus of Panama (once no doubt much broader) is no boundary; if the meeting of N. and S. had taken place there, that narrow causeway would be crowded, and this is not the case.

NEW ZEALAND.-The only recent reptiles are Sphenodon (q.v.), which testifies to the great age of these islands; about half a dozen Scincidae of the genus Lygosoma, members of a cosmopolitan family; and some few geckos, e.g. Naultinus, of a family of great