CLASS AMPHIBIA. 299 



308. Habits of Life and Food. While most amphibians 

 have lungs in the adult stage the great majority of them 

 like to remain close in reach of water, and many of them 

 spend most of their lives in it. The fact that their eggs 

 must be laid in the water doubtless brings this about. 

 The soft, unprotected nature of their skin also makes it 

 necessary. The insects and worms, snails, Crustacea, 

 and small fishes, that they use for food are found abund- 

 antly in such regions. None of the amphibians live in 

 salt water. The frogs and the water forms have more 

 enemies than the toads. Chief among these are the 

 wading birds, fishes, and snakes. The common toads 

 are active chiefly after dusk and the tree toads are often 

 colored in such a way as to be inconspicuous. In the 

 case of the frogs their white bellies render them less con- 

 spicuous to the enemies below them in the water; and 

 their green and rusty brownish colors, less visible to 

 enemies from above. 



Their quick leap is also puzzling to a pursuer, as has 

 doubtless been discovered by the members of the class 

 who have undertaken to capture them. 



309. Reproduction and Development. Most amphib- 

 ians breed in the early spring. The eggs are laid singly 

 or in masses and are surrounded by a gelatin which 

 swells up on entering the water and protects them and 

 holds them together. They are fertilized after leaving 

 the body of the mother. Only a few days are required 

 for hatching and escape from the gelatinous envelop as a 

 young tadpole. Fig. 118 will illustrate some of the steps 

 in the later development. The most important fact to 

 be remembered and studied is the metamorphosis through 

 which they go. This metamorphosis involves from the 



