STUDIES IN ANIMAL LIFE. 101 



mits of limited variations ; any cause which should 

 push the variation beyond certain limits would de- 

 stroy the species, because by species is meant the 

 group of animals contained within those limits. Let 

 us suppose the original stock from which all these 

 kinds of cats have sprung to have become modified 

 into lions, leopards, and tigers in other words, that 

 the gradual accumulation of divergencies has re- 

 sulted in the whole family of cats existing under 

 these three forms. The lions will form a distinct 

 species; this species varies, and in the course of 

 long variation a new species, the puma, rises by the 

 side of it. The leopards also vary, and let us sup- 

 pose their variation at length assumes so marked a 

 form in the ocelot that we class it as a new spe- 

 cies. There is nothing in this hypothesis but what 

 is strictly consonant with analogies; it is only ex- 

 tending to species what we know to be the fact 

 with respect to varieties ; and these varieties which 

 we know to have been produced from" one and the 

 same species are often more widely separated from 

 each other than the lion is from the puma, or the 

 leopard from the ocelot. Mr. Darwin remarks that 

 " at least a score of pigeons might be chosen, which, 

 if shown to an ornithologist, and he were told that 

 they were wild birds, would certainly, I think, be 

 ranked by him as well-defined species. Moreover, 

 I do not believe that any ornithologist would place 

 the English carrier, the short-faced tumbler, the 

 runt, the barb, the pouter, and fantail in the same 



