THE BULLFROG 119 



The bullfrog, indeed, pertains to an order far more 

 distinct from the other orders of its class than is man's 

 order from the various orders which comjjose his own 

 class, the class of mammals. It also belongs to an order 

 which is singularly homogeneous, and yet to a class 

 (Batrachia), which compared with that of birds is very 

 heterogeneous. 



It is an animal which diflters from every member of 

 the higher classes of vertebrates in that it comes into 

 the world with a structure and with habits which con- 

 trast most forcibly with its structure and habits when 

 adult. In fact, it undergoes a metamorphosis ! 



If, then, we are asked. What is a bullfrog ? we may 

 reply : " It is a very large North American species of 

 the genus Rana, a genus of an order of tailless, lung- 

 breathing, gilled vertebrates, with fore limbs typically 

 differentiated and undergoing a distinct metamorphosis, 

 its order being one of those four w^liich makes up the 

 class Batrachia." 



Such is our reply to the question as to what the frog 

 is ; but we may further ask how did it come to be — what 

 was the origin of frogs ? We may also, on the principle 

 of evolution, and seeing how very ancient the frog's class 

 is, be asked what forms may be supposed to have sprung 

 from it ? Of what existing creatures, which are not 

 Batrachia, can batrachians be supposed to have been the 

 ancestors ? 



In the early days of the promulgation of the theory of 

 evolution nothing seemed easier than to answer such 

 questions. Genealogical trees of animal life were set up 

 by very many naturalists — most conspicuously of all by 

 Prof. Haeckel of Jena — with eagerness. Soon, however, 

 they were found to need pruning, then " lopping and 

 topping," and finally not a few have we seen cut dow^n or 



