24 THE GENESIS OF SPECIES. [Chap. 



separate organism as the expression ot" powers and ten- 

 dencies not to be accounted for by "Natural Selection" 

 alone, or even by that together with merely the direct 

 influence of surroundinji conditions. 



The difiicullics which appear to oppose themselves to 

 the reception of ''Natural Selection" or "the survival of 

 the fittest, " as the one explanation of tlie origin of species, 

 have no douljt been already considered by Mr. Darwin. 

 Nevertheless, it may be worth while to enumerate them, 

 and to state the considerations which appear to give them 

 weight ; and there is no doubt but that a naturalist so 

 candid and careful as the author of the theory in c|ues- 

 tion, will feel obliged, rather than the reverse, by the 

 suggestion of all the dilliculties which can be brought 

 against it. 



AVhat is to Ije brought forward may be summed up as 

 follows : — 



That " Natural Selection " is incompetent to account for 

 the incipient stages of useful structures. 



That it does not harmonize with the co-existence of 

 closely similar structures of diverse origin. 



That there are grounds for thinking that specific dif- 

 ferences may be developed suddenly instead of gradually. 



That the opinion tliat species have definite though very 

 different limits to their variability is still tenable. 



That certain fossil transitional forms are absent, which 

 might have been expected to be present. 



That some facts of geographical distribution intensify 

 other dilliculties. 



That the objection drawn from the physiological 

 difference between " species " and " races " still exists 

 unrcfated. 



