Il6 NATURE STUDIES. 



the newts themselves teaclies us that the newts have 

 arisen from the fish- stock, and that they represent a 

 lower phase of amphibian life than do the frogs and 

 toads with their shortened tails. Indeed, the study 

 of the frog itself not merely proves to us its own 

 evolution, but demonstrates an orderly sequence in 

 the descent of its class a sequence wherein the 

 newt-type followed the fish, and wherein the frog- 

 type, in turn, was evolved from the newt. 



That some such explanation or, at least, an ex- 

 planation based on similar grounds is the only 

 feasible method of explaining the metamorphosis of a 

 frog, may be stoutly maintained against all comers. 

 Evolutionists may differ regarding the exact lines 

 along which the descent proceeded. They do not 

 differ regarding the main facts at issue, namely, that 

 fishes are linked to frogs in more ways than one, 

 and that the history of the frog-race, rightly viewed, 

 is really a connecting-thread on which the various 

 forms of living and extinct members of its class may 

 be strung. In my next paper, I shall endeavour to 

 trace the f ' links " which bind birds to reptiles. 



PART III. BIEDS AND REPTILES. 



THERE are no two classes of animals between which 

 exists a greater dissimilarity than birds and reptiles. 

 The active organisation of the one and the sluggish 

 ways of the other, the warm blood of the former and 

 the cold blood of the latter, are points in the popular 



