266 



MOVEMENT 



which has a shorter body, the track of the hind feet is 

 very near that of the front. Moreover, the movements 

 are extensive, and cause a serpentine twisting of the 

 whole body. As these movements are very rapid, a 

 great number of photographs must be taken — about 

 sixty per second — in order that their sequence may be 

 distinguished. 



Frogs, Toads, and Tadpoles.— In accordance with the 

 stage of development, batrachians depend on different 

 types of locomotion. 



Before the tadpole's legs are completely developed 



Fig. 188. — Locomotion of batrachians at different periods of development. 



it swims with its tail after the manner of a fish (Fig. 

 188, first row). When the tail has disappeared and 

 the four legs are completely formed, the swimming 

 of batrachians resembles that of man (Fig. 188, 

 second row). The legs, which are at first widely 

 separated, are brought suddenly together, then drawn 

 up under the body, and finally separated again, 



