14 



HERPETOLOGY. 



ith skin, yet in reality the whole body within A difference of sexes prevails in all reptiles, and the 



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jtn*iuy 

 cad Pbyo. the shell is enveloped with a thin transparent cuticle, 



fc*yrf 



Rtpulo. 



MKl<*of 

 the tkin. 



Change ef 



capable of being detached in plates. In most of these 

 animals, the cuticle, when exposed, is covered with 

 of a horny texture, and differing very much in 

 number, situation and figure. A thin membrane re- 

 einhling cuticle, also covers the shell of the Chelonians; 

 and in several ipecies, the upper shell, or shield, is co- 

 vrred with a dense and strong membrane resembling 

 K'nthcr or parchment. Among the Saurians there is 

 first a cuticle enveloping the true skin, then scales, 

 plates, or tubercles, and over these again another cu- 

 ticle, as in the Chelonians. In the crocodiles and 

 Dractma, there are strong and broad plates differently 

 shaped and arranged, as we shall see hereafter ; in the 

 tupinambes, the scales are disposed in circular rows 

 or transverse bands ; in the basilisks, they are diffused 

 over the whole body, while in the lizards again, they 

 are arranged in transverse bands. The Batracians have 

 the epidermis smooth, and in general slimy. 



The Saurians have generally very strong and nume- 

 rous subcutaneous muscles, especially in the tail ; and 

 in most cases, there is an intimate connection or adhe- 

 sion between these muscles and the skin. 



We have already seen that the Chelonians are co- 

 vered, both on the upper and lower parts of their body, 

 with a strong and hard shell, of which the upper part 

 may be termed the shield, and the lower the breast- 

 plate. Each of these is divided into a considerable 

 number of separate plates, united together by their 

 edges, sometimes in a smooth and even manner, at 

 others overlapping each other. A row of these plates 

 lies along the middle of the back over the vertebrae, 

 and these are surrounded on each side by several others, 

 which, together with the vertebral plates, constitute 

 what is called the disc. The other plates of the shield, 

 lying between the disc and the breastplate, are called 

 marginal, and are generally from twenty-one to twenty- 

 live in number. They are of a more irregular figure than 

 those of the disc, and generally of an oblong form. The 

 shield is more or less convex. The shield and breast- 

 plate are united only at their sides, leaving a space at 

 the fore and back parts for the head, tail, and extremi- 

 ties. This shelly covering, in general, resembles the 

 hoofs of quadrupeds in its texture, though in some in- 

 stances, as in what is called tortoise-shell, it is purer 

 and more transparent than the finest horn. 



The Saurians and Batracians occasionally change the 

 cuticle, throwing off the old, and acquiring a new one. 

 This is particularly the case while they are young, and 

 after leaving their winter quarters. In these animals, 

 the change is not made at once, as in serpents, (see 

 OPHIOLOOV.) but the cuticle is detached in scales or 

 plates, till the whole is thrown off. 



CHAP. VIII. 



O/ Generation in Reptiles. 



THRK ii no part of the economy of reptiles more 

 Curiou", none more interesting to the naturalist, than 

 that function by which these animals generate their 

 like. The differences, with respect both to organs and 

 phenomena, which are found in this class, admirably 

 illustrate the observation of a celebrated naturalist, that 

 systematic arrangement of animals, as well as plants 

 might lie composed merely from a comparison of their 

 generative organs. 



distinction of male and female organs is in most instan- 

 ces very manifest. There is one part of the structure, 

 however, found in both sexes. The cloaca, which has 

 been already noticed as forming the common outlet Sexes. 

 for the urine and faeces, also forms, as in birds, the 

 common receptacle of the external organs, and the out- 

 let for the ova. 



All male reptiles have testa, but these organs differ Male or _ 

 in form and situation. In the Chelonians, they lie with- j^g, 

 in the abdominal cavity, (as is the case in all these ani- 

 mals,) contiguous to the kidneys, and united to their 

 inferior or sacral surface. In the Saurians, they lie in 

 front, or on the sternal side of the kidneys, on each side 

 of the vertebral column ; and in the Batracians they are 

 situated immediately below the anterior surface of those 

 organs. In the first order, the testes are composed of 

 large vascular bundles, disposed in various directions ; 

 and the epididymis is formed in the usual way, by the 

 convolutions of the vessels, particularly of the seminal 

 duct, or vat dejerens. It is not certain whether these 

 animals have seminal vesicles. The lestcs of the croco- 

 dile are long and narrow, and communicate with two 

 organs that are supposed by some anatomists to be se- 

 minal vesicles, and if so, form the only instance of 

 these organs among the reptile tribes. In salamanders, 

 each of the testes is divided into two spherical bodies, 

 placed one before the other : and their texture consists, 

 as in all the Batracians, of an agglomeration of small 

 whitish granular bodies, interspersed with blood-ves- 

 sels. 



The penis is single in all the Chelonians, and in most 

 of the Saurians. The Batracians have 'no organ of this 

 kind ; but, in some of that order, its place appears to 

 be supplied by a small papilla within the cloaca. This 

 organ is most remarkable in the Chelonians, in some of 

 whom it is of very considerable length. It is cylindri- 

 cal, terminates in a point, and has a deep furrow along 

 the whole extent of its upper surface. It is furnished 

 with two retractor muscles, by which it is withdrawn 

 within the cloaca, where it usually lies concealed, and 

 from which it is thrust out in preparing for copulation. 

 In the Saurians, this organ is short, cylindrical, and 

 beset with numerous spiny processes, resembling the 

 bristles of the hedgehog. In the usual state, it is drawn 

 up under the skin of the tail, and, when erected, ap- 

 pears externally at the slit of the cloaca. 



We must here notice a peculiarity of structure in the 

 males of those reptiles which do not immediately copu- 

 late with the female. There are found in these males, 

 during the copulating season, hard brown or blackish 

 papilla; or tubercles, attached to the thumb and palm 

 of the fore feet, which assist in grasping the female. 

 These tubercles are found chiefly in the frog and toad. 

 Salamanders have, during the same season, a crest with 

 divided edge upon the back and tail, which afterwards 

 disappears. 



The female reptiles have ovaries, and most of them Female ON 

 a uterus, or an expansion of the oviducts, which answers gans. 

 a similar purpose. The ovaries of the Chelonians re- 

 semble those of birds, (see ORNITHOLOGY. ) They are 

 two in number, and have each a duct opening into a 

 uterus. The uleri are thick and fleshy, and have open- 

 ings by which they communicate with the cloaca. The 

 ovaries of the Saurians and Batracians are much alike ; 

 but the former contain fewer eggs, and have larger and 

 shorter oviducts. Those of frogs lie below the liver. 



A curious structure prevails in the female of the Su- 

 rinam toad, or Bufo dorsiger. The skin of the back in 



