6 Permanence and Evolution. 



is the antipodes of a clear idea, combining, 

 as it does, the notions of origin from one 

 stock, real or possible ; existence as distinct 

 races in a wild state, even in separate areas ; 

 fertile reproduction inter se, breeding together 

 naturally, without human interference, and a 

 certain undetermined degree of likeness. That 

 these things go together is taken for granted, 

 hence interminable debates as to whether any 

 given races of animals are distinct species, 

 or only varieties of one species. It is often 

 brought forward as proof of the specific unity 

 of two animal forms, that when crossed they 

 produce perfectly fertile offspring. Now if we 

 adopt the definition of species founded on fertile 

 interbreeding, this is tautology ; if any other, 

 it is an unproved assumption on a subject of 

 which we can know nothing except from ex- 

 perience. There is no reason why there should 

 not exist in nature any number of original races 

 differing in all manner of degrees, and capable 



