380 • ZOOLOGY 



limbs in relation to the body come to overlie and obscure the 

 axial muscles proper. The Anura (frogs and toads) are espe- 

 cially adapted to leaping and swimming by the great muscular 

 development of the hind legs. 



405. Exercise. — ^Are there any special advantages in the leaping habit of 

 motion either in the capture of prey or in escape from enemies? Verify from be- 

 havior of toads and frogs. Can you findillustrations from other groups of animals? 



406. Habits and Habitat. — There. are no marine Amphibia. 

 Nearly all live in or near the fresh-water streams, swamps, or 

 ponds, even in the adult air breathing stage. Some are good 

 climbers (tree-toads) ; others burrow. The tailless forms (Sali- 

 entia) are found the world over except in salt water. The 

 Caudata belong chiefly to the northern hemisphere. All are 

 more abundant in warmer climates. Their food consists largely 

 of insects, worms, and the smaller animals. The larvae even of 

 carnivorous forms are sometimes vegetable feeders. They may 

 live for a long time without food, and survive the winter in the 

 colder latitudes by burrowing deep into the mud at the bottom 

 of their ponds, or otherwise hibernating. During this time the 

 vital processes are suspended or much reduced. 



407. Reproduction and Development. — The common Am- 

 phibia lay rather large eggs, with a considerable amount of yolk 

 which results in more or less unequal cleavage (Fig. 13, B). 

 The eggs are usually surrounded by a gelatinous material, for 

 their protection and adhesion, but they have no shell. They 

 are almost universally deposited in the water, where impreg- 

 nation takes place. In some of the Caudata impregnation is 

 internal. In occasional species the young are brought forth alive. 

 Ordinarily further development takes place in the water without 

 any attention from the parents (frogs and toads). In a small 

 South American frog {Rhinoderma) the male carries the fertilized 

 eggs in his vocal sacs until hatched; in one of the tree-frogs from 

 South America (Gastrotheca) the female has a pouch on the back 

 in which the eggs are stored and hatched; in the Surinam toad 

 the eggs are placed by the male on the back of the brooding 

 female, where they become surrounded by spongy tissue. In 

 these pits they hatch at once into the adult form without having 



