ORDER BATRACHIA. 417 



solely on vegetable substances, with the exception, according 

 to M. Dumeril, of the obstetric toad. 



This is the state in which it is named by us tadpole^ a 

 word which literally signifies the young of a toad. The 

 French call it tetard, from tete, (head,) in consequence of 

 the volume of the anterior part of the body. At this time 

 it inhabits the water as a matter of necessity. 



But it soon changes its skin ; its eyes begin to shew them- 

 selves. First its two hinder feet, then the fore-feet appear 

 on the sides of the trunk, and finally, the fall of the tail is 

 speedily followed by the loss of the gills, while at the same 

 time the digestive canal loses much of its dimensions. 



Then the animal respires the atmospheric air, and acquires 

 the form which it is destined to preserve for the rest of its 

 existence. 



In the egg of the salamander, the tadpole, curved on itself, 

 and enveloped by a vitelline membrane, is free, and unpro- 

 vided with an umbilical cord. 



The spinal marrow of this embryo is divided and composed 

 of two nervous cords, in front of which is a very small ves- 

 sel, dilated at one of its extremities, and which has been 

 supposed to represent both the heart and the aorta. Here 

 then we find, according to M. Iloth, some approximation 

 between this arrangement and that of the nervous system in 

 the annelides. 



The limbs make their first appearance in the shape of 

 papillae. 



Under the head of the hyoid apparatus, the examination 

 of the tadpole of the frog is of great importance in com- 

 parative anatomy, since, as the Baron has demonstrated, it 

 leads us to the knowledge of what is truly the hyoid bone 

 in fishes ; and the more so because the frog, having in its 

 first state respired like fishes, undergoes such modifications 



VOL. IX. 2 E 



