416 CLASS REPTILIA. 



The tadpole then is a young batracian, from the moment 

 in which it issues from the egg, until, after various metamor- 

 phoses, it passes to the adult state, without preserving either 

 its form, structure, or even its mode of living. 



When we examine the different periods of its evolution in 

 the eggs of frogs, (which of all the eggs of reptiles have 

 been the most carefully studied, as to the development of 

 germs,) we find that during the three or four days which 

 follow the fecundation, the tadpole is nothing but a kidney- 

 formed mass of small granulations. Towards the middle of 

 the fourth day, these little grains are confounded one with 

 the other : the embryo becomes distinct. It is divided by a 

 contraction into two parts, one of which comprehends the 

 head and thorax, the other the abdomen and tail. It is im- 

 mersed in a fluid, which Swammerdam has compared to that 

 of the amnios. 



Moreover, according to the same observer, we then per- 

 ceive in the eggs in question, an allantoi's, a chorion, an 

 amnios, and umbilical vessels. 



During the fifth day, the embryo increases a little, and 

 towards the evening of the sixth, we see besides the head, 

 thorax, abdomen and tail, a gill appear on each side of the 

 neck, and answer the purpose of respiration, for the little 

 animal, of swimming, and of reposing itself in the glairy 

 fluid. 



In the course of the seventh, and at the commencement 

 of the eighth day, the foetus successively leave the albu- 

 minous fluid of the milt ; and from thence until the thirteenth 

 day, they exhibit no change of form, and merely augment 

 in volume. 



On coming out of the ^gg^ the little batracian is blind 

 and without feet. It has a tail even in the anourous species 

 of frogs and toads ; it respires by gills ; it has a large and 

 globulous belly ; its intestines are excessively long. It lives 



