74 DARWINISM TO-DAY. 



we recall what Darwin has said on the advantage that 

 those forms will have in which a great number of new 

 variations appear to fit them to the great diversity of 

 natural conditions, and if we recall the gradations that exist 

 in external conditions, I think we shall find that Darwin's 

 reply fails to give a satisfactory answer to the question. 



"It is well known, and Darwin himself has commented on 

 it, that the same species often remains constant under very 

 diverse external conditions, both inorganic and organic. 

 Hence I think the explanation fails, in so far as it is based 

 on the accumulation by selection of small individual varia- 

 tions that are supposed to give the individuals some slight 

 advantage under each set of external conditions. Darwin 

 admits that 'this difficulty for a long time quite confounded 

 me. But I think it can be in large part explained/ The 

 first explanation that is offered is that areas now continuous 

 may not have been so in the past. This may be true in 

 places, but the great continents have had continuous areas 

 for a long time, and Darwin frankly acknowledges that he 

 'will pass over this way of explaining the difficulty/ The 

 second attempt is based on the supposed narrowness of the 

 area, where two species, descended from a common parent, 

 overlap. In this region the change is often very abrupt, 

 and Darwin adds : 



" 'To those who look at climate and the physical condi- 

 tions of life as the all-important elements of distribution, 

 these facts ought to cause surprise, as climate and height 

 or depth graduate away insensibly. But when we bear in 

 mind that almost every species, even in its metropolis, would 

 increase immensely in numbers, were it not for other com- 

 peting species; that nearly all either prey on or serve as 

 prey for others ; in short, that each organic being is either 

 directly or indirectly related in the most important manner 

 to other organic beings, we see that the range of the in- 

 habitants of any country by no means exclusively depends 



