RECAPITULATION 289 



varieties and sub-species, and species. On separate con- 

 tinents, and on different parts of the same continent 

 when divided by barriers of an^^ kind, and on outljdng 

 islands, what a multitude of forms exist, which some 

 experienced naturalists rank as varieties, others as geo- 

 graphical races or sub-species, and others as distinct, 

 though closely allied species! i 



If, then, animals and plants do varj', let it be ever / 

 so slightly or slowly, why should not variations or indi- 

 vidual differences, which are in any way beneficial, be 

 preserved and accumulated through natural selection, .- 



or the survival of the fittest? If man can by patience ^v 

 select variations useful to him, why, under changing and 

 complex conditions of life, should not variations useful 

 to nature's living products often arise, and be preserved 

 or selected? What limit can be put to this power, act- 

 ing during long ages and rigidly scrutinizing the whole 

 constitution, structure, and habits of each creature — 

 favoring the good and rejecting the bad? I can see no 

 limit to this power, in slowly and beautifully adapting 

 each form to the most complex relations of life. The 

 theory of natural selection, even if we look no further 

 than this, seems to be in the highest degree prob- 

 able. I have already recapitulated, as fairly as I 

 could, the opposed difficulties and objections: now let 

 us turn to the special facts and arguments in favor of 

 the theory. 



On the view that species are only strongly marked 

 and permanent varieties, and that each species first ex- 

 isted as a variety, we can see why it is that no line of 

 demarcation can be drawn between species commonly 



