REPTILES AND AMPHIBIANS II7 



Science pursues the same method. It seeks the 

 common element in wider and wider groups of animals, 

 and overlooks what is individual. Fox, wolf, weasel, 

 marten, are regarded in their common features, and 

 described as " carnivores " or carnassia. All "species " 

 are distributed in "orders" of this kind. The work 

 is carried even further. Some of the orders of animals 

 are found to have features in common, and these are 

 bracketed together as "classes." Finally, the "classes " 

 are distributed into " stems." Thus the vertebrate 

 " stem " represents what is common to the five 

 " classes," mammals, birds, reptiles, amphibians, and 

 fishes, namely, the possession, first of all, of an internal 

 axial skeleton. This feature is not found in the other 

 stems, the members of which are at the most covered 

 externally with hard parts. 



It is the merit of Darwinism to have established that 

 there are in the nature which we really know no 

 "species," but merely a countless number of individuals, 

 each of which is unlike the other. Darwin has shown, 

 in fact, that the feature which is common to certain 

 forms, and enables us to grasp them as a " species," is 

 not always absolutely fixed. When, for instance, we 

 find that a number of individuals agree in having " long 

 ears" and so can be formed into a species, differing 

 from another or short-eared species, we see also that 

 there are other animals with ears of intermediate length. 

 Such animals could with equal right be put in either of 

 the two species. 



But while Darwin has destroyed species as realities, 

 he has at the same time fully established the idea of the 



