216 Darwin, and after Darwin. 



Moreover, it certainly originated as a direct result 

 of climatic influences, independent of natural selection ; 

 seeing that, as soon as individual members of this 

 apparently new species were restored to their original 

 climate, they recovered their original colouration. 



As previously remarked, it is, from the nature 

 of the case, an exceedingly difficult thing to prove 

 in any given instance that natural selection has not 

 been the cause of specific change, and so finally to 

 disprove the assumption that it must have been. 

 Here, however, on account of historical information, 

 we have a crucial test of the validity of this assump- 

 tion, just as we had in the case of the niata cattle; 

 and, just as in their case, the result is definitely 

 and conclusively to overturn the assumption. If 

 these changes in the Porto Santo rabbits had been 

 due to the gradual influence of natural selection 

 guided by inscrutable utility, it is simply impossible 

 that the same individual animals, in the course of 

 their own individual lifetimes, should revert to the 

 specific characters of their ancestral stock on being 

 returned to the conditions of their ancestral climate. 

 Therefore, unless any naturalist is prepared to con- 

 tradict Darwin's statement that the changes in 

 question amount to changes of specific magnitude, 

 he can find no escape from the conclusion that 

 distinctions of specific importance may be brought 

 about by changes of habitat alone, without reference 

 to utility, and therefore independently of natural 

 selection. 



