74 NO STRUGGLE NO SELECTION 



it is waiting for the occurrence of another individual 

 difference of the same favourable nature as before, to 

 improve it still further. This favourable variation at 

 length occurs, and begins its developmental action. 

 Let us assume that the favourable variation occurs in 

 one or two individuals. Darwin has exercised some 

 ingenuity in arguing, though in my opinion far from 

 conclusively, that individuals who have favourable 

 differences are more prolific than those who are less 

 fortunately varied, and that consequently they will 

 increase in numbers faster than the others. As time 

 goes on, he assumes that the favourably varied 

 individuals will become more and more numerous 

 in relation to the common form, which is also 

 undergoing a process of decimation from the destruction 

 of a still larger number of individuals by injurious 

 variations. 



At length the individuals possessed of the favourable 

 difference become the common form, and soon none of 

 the old form are left, and all the species possess the 

 favourable difference which has now become a character- 

 istic of the species. But from the time when the 

 favourable individual variation first occurred, until it 

 has achieved its work of modifying the species, and 

 becoming one of its fixed characters, a long interval of 

 time has elapsed, many ages probably, and what has 

 been accomplished is, after all, an infinitesimal modifi- 

 cation ; for, as Darwin is fond of repeating, " Natura non 

 facit saltum." As to what now takes place, he says : 

 " A variety, when once formed, must again, perhaps after 



