204 THE ANIMALS AND MAN 



gills after hatching readily distinguish them from all the 

 batrachians. While most reptiles live on land, some in- 

 habit fresh water and some the ocean. As the young have 

 the same habitat and general habits as the adult, there is 

 no such metamorphosis in their life-history as is shown by 

 the batrachians. The reptiles are widespread geographi- 

 cally, occurring, however, in greatest abundance in tropical 



FIG. 101. The tiger salamander. (After Jenkins and Kellogg.) 



regions, and being wholly absent from the arctic zone. 

 They are not capable of such migrations as are accomplished 

 by birds and many mammals, but withstand severely hot 

 or cold seasons by passing into a state of suspended ani- 

 mation or seasonal sleep or torpor. 



The chief variations in body-form among the reptiles 

 are manifest when a turtle, lizard, and snake are compared. 

 In the turtles the body is short, flattened, and heavy, and 

 provided always with four limbs, each terminating in a 

 five- toed foot; in the lizards the body is more elongate, 

 and with usually four legs, but sometimes with two only, 

 or even none at all; while in the snakes the long, slender, 

 cylindrical body is legless, or at most has mere rudiments 

 of the hinder limbs. With the reptiles, locomotion is as 

 often effected by the bending or serpentine movements 

 of the trunk as by the use of the legs. Among lizards and 

 snakes the body is covered with horny epidermal scales or 



