24i 



PROGS, TOADS, AND SALAMANDERS 



passed on land. Since the earl}', or larval stage, of these 

 animals is }ms.setl in the water, most of the larva' are furnislied 

 with gills for breathing. Adult amphibians that hve in the 

 water all their lives retain the gills throughout life. Those, 



ho\\'ever, that live on 

 lantl during the adult 

 stage lose the gills, an( 1 

 have lungs instead. 

 They differ from the 

 fishes in having seg- 

 mented Umbs instead 

 of fins. The}' are 

 cold blooded. The 

 majorityhave smooth, 

 scaleless skins. 



Adaptations to en- 

 vironment. — Note 

 that the tadpoles of 

 amphibians wliich live 

 in the water have 

 gills to suit such an 

 land is substituted for water, 

 Again, the necturus 



Fig. 169.- 



4H ' 

 ■Tree toad on the bark of a tree 



environment; but when dry 

 the gills are lost and lungs appear, 

 and the siren that live in the water all their lives retain the 

 gills throughout life, as best suited to such an emdronment. 

 Tadpoles of frogs and toads are providetl with broad, 

 flat tails for swimming; but the adult frogs and toads are 

 tailless. Many frogs are excellent swimmers, however, 

 because of their webbed toes and the adaptations of their 

 legs to such a purpose. The webbed toes of some species 

 of the tree frogs of the Malaysian Islands (Fig. 170) have 

 become much enlarged and adapted to quite a different 



