AMPHIBIA 



221 



CLASS III. AMPHIBIA 



To this class belong the toads, frogs, salamanders, and 

 newts. The skin is smooth, as in the frog, or warty, as in the 

 toad, with a glandular secretion. It is often highly colored 

 owing to the pigment cells in the deep layers. In the common 

 "tree-toad," as well as in some of the 

 terrestrial frogs, the color may be 

 changed to harmonize with the en- 

 vironment. No amphibians are ma- 

 rine. Most of them are aquatic or 

 semi-aquatic. In the adult stage some 

 are terrestrial, some arboreal. They 

 are usually carnivorous in the adult 

 stage, but the larvae may be herbivo- 

 rous. They hibernate in the mud at 



'Vf;;. 



Fig. 182.— Bullfrog. (Skeleton 

 cleaned and mounted by stu- 

 dents.) 



Fig. 183. — Necturus. (Skeleton 

 cleaned and mounted by stu- 

 dents.) 



the bottom of a stream and may live a long time without food. 

 They make fine specimen? for study in a tank or tub, since 

 many of them will endure captivity a good while. 



