CLASS AMPHIBIA 381 



404. Regeneration. — Amphibians possess greater powers of regenera- 

 tion than any other vertebrates. Limbs and tails of larvae when cut 

 off readily regenerate. This of course is an advantage when mutilation 

 occurs as the result of seizure by enemies. 



405. Hibernation. — The power of hibernation is sometimes considered 

 as an additional adaptation to terrestrial hfe. During the winter and 

 frequently during seasons when bodies of water become dry, amphibians 

 will bury themselves in the mud at the bottom and remain there in a 

 dormant condition until spring or until the water is restored. During 

 this period of dormancy the lungs are not used in breathing, and respira- 

 tion must take place through the skin. The temperature of the hiber- 

 nating animal remains sUghtly above that of the earth about it, only a 

 small amount of physiological activity is maintained, and the organism 

 lives on food stored in its body. In some tropical countries amphibians 

 exhibit a similar dormant condition during the heat of the summer. 

 This phenomenon is known as estivation. 



406. Economic Importance. — Amphibians are almost mthout excep- 

 tion beneficial, and some, particularly the toads, are of considerable 

 importance as destroyers of noxious insects. Frogs are used as food, 

 the hind legs only being eaten, and frog farms are now being operated 

 in Wisconsin, California, and a number of other states. Frogs are 

 also used very extensively in laboratory experimentation and as fish 

 bait. 



