194 



THE FOOD OF ANIMALS 



It has already been pointed out (p. 7) as a rule of general 

 application that the digestive tract is relatively longer in creatures 

 which live on vegetable food than in those which subsist on 



Fig. 434. — Tadpoles 



animal matter. The Frog is a very interesting application of 

 this rule, for we find that in the tadpole the intestine, here coiled 

 like a watch-spring, is relatively longer than in the adult animal. 



FISHES 



Lung-Fishes (Dipnoi), Sharks and Rays (Elasmobranchii), 

 and the Ganoid group (Sturgeons, &c.) of the Teleostome fishes 

 are exclusively or mainly carnivorous, and the same is true for 

 most families of the Ordinary Bony-Fishes (Teleostei) which 

 constitute the great bulk of the last-named subdivision. A good 

 many of the Teleosts, however, are mixed feeders, and a few are 

 vegetarians pure and simple. Among these last may be mentioned 



