18 



REPTILES AND BATRACHIANS. 



the mouth. In the account of each we shall recur again to this 

 subject. 



In the above particulars all reptiles and batrachians are alike ; 

 but in form and action no single class of animals are less alike. 

 To compare one with another and the various orders — some with 

 four legs, some with two legs, or no legs, with a tail and without, 

 some covered with a hard, solid case, others with strong plates, 

 some with scales, and some with only a soft, smooth, and ex- 

 ceedingly sensitive skin, some with a spine reduced to a few 

 joints, while in others it is extended to three or four hundred 

 vertebras ; some with eyelids and others without, we should scarcely 

 pronounce them all of a class, and yet their internal organism is 

 alike in all. Their movements are as varied as their form. 

 Among them some fly, others creep, crawl, or glide. A frog 

 "hops," leaps really, and with wonderful skill and precision, 

 and swims in the true scientific manner ; a tortoise creeps, and 

 to save its life it can only creep, therefore never attempting escape 

 in peril, it retires within its fortress, and is there safe. There are 

 frogs and lizards that live in trees and can fly, but not with wings. 



Fig. 3.— Flying Frog. 



The frog (fig. 3) has exceedingly long fingers and toes, with a strong 

 membrane between each, so that when outspread they are like 

 four fans, each covering some considerable space, and enabling it 

 to take leaps from branch to branch, or to let itself down to the 

 ground and up again supported by these four fans, like parachutes, 

 to break its fall. The little flying lizard, Draco volans (fig. 4), is 

 similarly sustained in its leaps, but by five or six of its middle ribs, 



