REPTILES. 



angle, of which the point is made by the union of the two 

 heads ; or they may only join muzzle to muzzle. The 

 bodies arc always very near together, fo that the angle 

 formed by the two heads or muzzles is always very acute. 

 Then the male erefts that dcntatcd prominence, which is 

 placed on his back, and agitates it in a curious manner: 

 he alfo moves his tail bri(l<ly, bending it about, and ftriking 

 very gently the fides of tlie female. During this time lie 

 emits from the aperture of the anus, now unulually tumid 

 and dilated, a copious jet of femen, which mixes with the 

 water, and thus diluted arrives at the anus of the female, 

 alfo more enlarged than ufual. In this important operation, 

 then, the anus of the male is never in contatt with that 

 of the female, which maintains a greater or fmallcr diltancc, 

 and never {hews any part charafterillit of her fex. After 

 the male has difcharged this jet of femen, he reils for a 

 while, on fome occafions quitting the female; he then re- 

 turns to his employment, and repeats the contortions of his 

 tail, and the eniiflion of femen." § 8o. 



In the land newts there is a momentary copulation : " in 

 the cleareft days, and in the places moll cxpofed to the 

 iun, the male runs after the female, and when he has over- 

 taken her, he twines himfelf about her, and unites his geni- 

 tals to her's, but this union may be termed momentary, 

 after which they part." § 8l. 



The vehemence of the propenfity in amphibia is fo re- 

 markable, that they aftually will copulate with other fpe- 

 cies, as frogs with toads, &c. No example of hybrid ofF- 

 fpring, from fuch a conjunftion, has been recorded. It 

 has alfo been known, that frogs, in want of a female, have 

 copulated with other males, or with dead females. 



That the animals are entirely abforbed by the powerful 

 emotions accompanying this aft is evinced by a feries of 

 difgufting experiments of Spallanzani, purfued and multi- 

 plied with an unrelenting and unneceflary cruelty, and re- 

 lated quite coolly, without evidence of remorfe or the 

 flightelt apology. He pricked, cut, and hacked the male 

 frog and toads, without making them loofe their hold ; am- 

 putation ot the limbs, and of the head, was equally ineffec- 

 tual. 



Males, after fuffering amputatidn of the fore or hind 

 limbs, renewed their fituation, and completed the genera- 

 tive aft. *• Nay, even the decapitation of a frog did not 

 Hop the embraces or fecundation. It is well known, that 

 thefe animals are fo tenacious of life, that th.at operation 

 does not take it away immediately. That of which I am 

 fpeaking was thrown into convulfions ; but neitlier the 

 fore-feet nor legs quitted the breaft of the female, which 

 brought forth her fetufes in an hour and three quarters, and 

 I was an eye-witnefs to the male's befprinkling them with 

 femen ; that they were fecundated there can be no doubt, 

 fince they came to life at the ufual time. As foon as he 

 had performed this operation, he deferttd his fituation, and 

 died in four hours afterwards." Diflertations, v. 2. § 90 

 and 100. 



All reptiles may be faid to be oviparous ; an egg, contain- 

 ing the germ, and as much nourifliment as is necelfary to fup- 

 port it until it is fufficiently developed to leave this abode, is 

 formed in the body of the mother, and enters the oviduft in all. 

 But there is a fubdivifion, according to tlie fubfequent pro- 

 grefs of the egg thus produced. In the greatelt number of 

 reptiles, the ova or eggs are laid by the female in that ftate, 

 and the young reptiles are developed afterwards : but m 

 fome, as the venomous ferpents, and the true lalamander, 

 the ovum may be faid to be hatched in the oviduft, although 

 the animals Hill come into the world fo far enveloped by the 

 membranes, that the charafter of an oviparous generation is 



preferved. The reptiles of the latter kmd are called ovo- 

 viviparous. 



In botli thefe cafes, a real egg, like that of birds, is pro- 

 duced, and has no conneftioii with the body of the mother ; 

 it is a very different thing from the ovum of the marnmiferous 

 animals, in whicli there is no fupply of nourifliment for the 

 foetus ; and the latter is coiincfted by the umbilical chord 

 with the vcffels of the mother, and derives from this fource 

 the materials of its growth. Here, as no true egg is pro- 

 duced in any part of the procefs, and as the young are al- 

 ways brought into the world alive, they may be juflly termed 

 viviparous. See Lacepcde, Hill. NaturcUe des Serpens, 

 t. i. p. 31. 



In ufing the common term ovum, we do not mean to re- 

 prefent that the thing produced is the fame in all ; nor that 

 It is like the egg of birds in all. There are varieties in the 

 different orders, and, in the batracians at leaft, there is not 

 a very clofe analogy to the ova of birds. 



The eggs of reptiles are covered with a membranous, ra- 

 ther than calcareous Ihell ; but there is fome earthy matter 

 in it. In the green turtle this (hell is flexible, but contains 

 earthy particles. It is compofed of a foft membrane, con- 

 taining albumen, which heat does not harden, and a yolk 

 which it does. The eggs of lizards have a more or lefs hard 

 fhell : it is flexible in the grey lizard, hard in the fcink ma- 

 bouya, and the crocodile. It has been ailerted, that the 

 eggs of the iguana are not hardened by boiling. The cover- 

 ing of the egg is foft and calcareous in ferpents. The ba- 

 tracians lay gelatinous and femitranfparent eggs, without 

 any covering. 



A part, correfponding more or lefs clofely to the yolk of 

 a bird's egg, is produced in the ovary, efcapcs from it:( 

 membranous covering, and enters the oviduft, where it re- 

 ceives its external inveflment, as the yolk of^ the bird's egg 

 receives its fhell and albumen. In the turtle, the procefs 

 feems very ilmilar to what we fee in birds. There are nu- 

 merous large yolks obferved in the ovarium, cOHtained in ca- 

 lyces ; and thefe, when boiled, are very fim.ilar to the yolks 

 of birds. In the crocodile and ferpents, it is nearly the 

 fame. But in frogs, toads, and newts, the egg in the ovary 

 does not feem to be a yolk, but the rudiment of the tad- 

 pole ; and it comes forth, furrounded by a quantity of tranf- 

 parent glutinous matter. In the toad and newt, thefe rudi- 

 ments are formed into long cords by the glutinous medium, 

 which cords are double in the toad. In the frog they come 

 out fepai-ately in fo many fphcres of the gelatinous matter, 

 about the fize of large peas. 



In all the reptiles which have a penis, fecundation is effefted 

 within the body ; but in the batracians, which have no male 

 organ of copulation, it occurs extersally. When frogs are 

 joined, it may be feen, that an obtufe, tumid point, occu- 

 pying the place of the penis, is elongated, and brought to- 

 wards the eggs neareit the vent. By taking them-out of 

 water while this laying is going on, an aftual difcharge of 

 feminal fluid upon the eggs may be feen from this point. In 

 the fame way the male of the water newt difchargeshis fluid 

 into the water near the anus of the female, and thus fecun- 

 dation takes place. Spallanzani has inflituted an immenfe 

 number of experiments on this fubjeft ; they prove, that 

 if breeches be put on the frog, fo as to receive the feminal 

 fluid, no fecundation occurs ; while, on the contrary, the 

 feminal fluid from the epididymis, or the juice of the tefti- 

 cles, will produce artificial fecundation of eggs laid by the 

 female after the male has been removed, and othervvife un- 

 produftive, or of eggs taken out of the lower part of the 

 oviduft immediately after death. Dilution of the feminal 

 fluid, although it diminifhed the effeft of its aoplication, 



did 



