176 



ZOOLOGY. 



because they live a part of their lives in the water. All 

 Amphibians, with very rare exceptions, pass through a 

 metamorphosis; the young or larva? are called tadpoles; 

 their form is fish-like, as they breathe by external gills, and 

 do not at first have legs. 



An examination of the skeleton shows that the skull re- 

 sembles that of the higher vertebrates in being composed 

 of few pieces, while there are short ribs, and a true shoulder 

 and pelvic girdle to which the limb-bones are joined. The 



Fig. 223.— Skeleton of a Frog, a, skull; b, vertebrae; c, sacrum, and e, its con- 

 tinuation (urostyle); /, suprascapula; g, humerus; h, fore-arm bones; t, 

 wrist-bones (carpals and metacarpals); d, ilium; m, thigh (femur); n, leg- 

 bone (ulna); o. elongated. first pair of ankle-bones (tarsals); p, q, foot-bones 

 or phalanges. After Owen. 



heart is 3-chambered, there being two auricles and one 

 ventricle. 



Like fishes, Batrachians are highly colored in the spring 

 during the breeding season. The males of the newts at 

 this time acquire the dorsal crest and a broader tail-fin, 

 while in some species prehensile claws are temporarily de- 

 veloped on the fore-legs of the male. Male toads and frogs 

 are musical, the females being comparatively silent; the 

 vocal organs of the male are more developed than in the 

 females, and in the European edible frog large sacs for 



