130 FROGS AND TOADS 



and long before it lias disappeared two pairs of legs have 

 grown out. The front legs are weak, but the hind legs are 

 long and powerful, and being attached at the extreme end of 

 the body they have great freedom of movement. They are 

 adapted both for leaping and swimming. 



Of the adult creature, the body is short and broad, cov- 

 ered with a smooth skin, destitute of scales, and there is no 

 tail whatever. The mouth is wide and capacious. The 

 tongue is not free, being attached at the sides to the lower 

 jaw. The eyes are placed high up, cjuite above the upper 

 surface of the head, so that the creature can float with only 

 its eyes and nostrils above water. 



The frog skeleton possesses several marked peculiarities, 

 some of which must be noted, even though briefly. There 

 are no ribs. The vertebrae are very few in number, but very 

 wide in comparison with those of other vertebrates. The 

 pelvis is of great size, and so long that it forms nearly one- 

 half of the axis of the body. Instead of being attached at its 

 sides, midway from top to bottom, the thigh bones (femora) 

 are attached at the extreme lower end — the jiortion called 

 the is'chi-um. In comparison with other vertebrates, the 

 hind limbs and feet are of enormous proportions; and when 

 these members are flexed, and then suddenly straightened 

 out, the frog flies forward through the air as if thrown by a 

 powerful steel sj^ring. Some frogs can leap eight feet. 



Although there are no ribs, there is a well-developed breast- 

 bone, or sternum, for the attachment of the fore legs; and it 

 is said that in the frog the sternum appears for the first time 

 in the development of the vertebrates from the lower forms. 



