Chap. XIV. RECAPITULATION. 469 



have admitted the existence of varieties, which they 

 think sufficiently distinct to be worthy of record in 

 systematic works. No one can draw any clear distinc- 

 tion between individual differences and slight varieties ; 

 or between more plainly marked varieties and sub-spe- 

 cies, and species. Let it be observed how naturalists 

 differ in the rank which they assign to the many repre- 

 sentative forms in Europe and North America. 



If then we have under nature variability and a power- 

 ful agent always ready to act and select, why should we 

 doubt that variations in any way useful to beings, under 

 their excessively complex relations of life, would be pre- 

 served, accumulated, and inherited ? Why, if man can 

 by patience select variations most useful to himself, 

 should nature fail in selecting variations useful, under 

 changing conditions of life, to her living products? 

 What limit can be put to this power, acting during long 

 ages and rigidly scrutinising the whole constitution, 

 structure, and habits of each creature, — favouring 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 looked no further than this, 

 seems to me to be in itself probable. 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 favour of the theory. 



On the view that species are only strongly marked 

 and permanent varieties, and that each species first 

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

 of demarcation can be drawn between species, com- 

 monly supposed to have been produced by special acts 

 of creation, and varieties which are acknowledged to 

 have been produced by secondary laws. On this same 

 view we can understand how it is that in each region 



