ANIMAL KINGDOM, 261 



equal in number to the vertebras of birds, and in fact re- 

 present their rings and spinal processes. A circle of other 

 bony pieces, which appear to be analogous to the sternal 

 or cartilaginous portion of the ribs of other animals, sur- 

 rounds the carapace, and unites together all the ribs which 

 compose it. These are cartilaginous and flexible in the 

 genus Trionyx. The under surface of a Chelonian reptile 

 is in fact its sternum, and ordinarily composed of nine 

 pieces. So that we see in the extraordinary construction 

 of these animals what Cuvier means when he calls them 

 animaux retournts; they are in fact such, having their 

 skeletons on their outside, and the bones and muscles of 

 their head and limbs attached to the inside of this skeleton, 

 contrary to the plan pursued in all the other vertebrated 

 animals. Here then is an astonishing proof, that Nature 

 in one of her own groups adheres always to a particular 

 plan of organization even under the widest dissimilarities 

 of general form, and which plan of organization, could we 

 always detect it, would leave little to be desired in the way 

 of natural arrangement. 



The feet of the Tortoise cannot be assimilated to those 

 tentacula which we have termed feet in the Cephalopoda. 

 They are not even different forms of the same organ ; so 

 that this alone serves to throw a wide distance between the 

 two tribes of animals. To pass therefore from the Tortoise 

 to the Cephalopoda by a gradual change, some Chelonian 

 reptile must be found destitute of feet. But we know of 

 nonesuch; yet that the existence of such an animal is not 

 improbable, appears as well from the extreme shortness of 

 the feet throughout the tribe, as from the neighbouring 

 family of Ophidians being destitute of them. On quitting 

 a nervous system like that of the Mollusca, we ought to ex- 



