THE BULLFROG 



97 



made up of orders, and these are four in number. Three 

 of them are represented by living species, and the 

 fourth by others which have been extinct for an un- 

 imaginable abyss of time, namely, since the deposition of 

 the coal measures. 



Our present endeavour will be, first, to mention cer- 

 tain facts about frogs and the whole of that batrachian 



FIG. 26. 



THE BULLFROG. 



order of which they form part ; secondly, briefly to 

 describe the other three orders ; and, thirdly and finally, 

 to consider the relations which exist between the frog 

 class and the other classes of backboned animals. For, 

 just as we found birds to stand between beasts and 

 reptiles, so we shall find that batrachians stand between 

 reptiles and fishes, and also that as they advance in life 

 they become less like the latter and grow more like the 

 former. 



But the frog has special claims on our gratitude and 



