184 Darwin, and after Darwin. 



complexities of living processes, there is no room for 

 any other influence in the production of change, even 

 of the most trivial and apparently unmeaning kind. 

 But if there were any good evidence or logical argu- 

 ment to the contrary, this antecedent presumption 

 would have to give way ; and the certainty that all 

 specific characters are likewise adaptive characters 

 would be determined by the cogency of such evidence 

 or argument as could be adduced. In short, we are 

 not entitled to conclude — and still less does it follow 

 '' as a necessary deduction from the theory of natural 

 selection " — that all the details of specific differentia- 

 tion must in every case be either useful, vestigial, or 

 correlated, unless it has been previously shown, by 

 independent evidence, or accurate reasoning, that there 

 is no room for any other principle of specific change. 



This, apparently, is the central core of the question. 

 Therefore I will now proceed to consider such argu- 

 ments as have been adduced to prove that, other 

 than natural selection, there can have been no " means 

 of modification.'' And, after having exhibited the 

 worthlessness of these arguments, I will devote the 

 next chapter to showing that, as a matter of ob- 

 servable fact, there are a considerable number of 

 other principles, which can be proved to be capable 

 of producing such minute differences of form and 

 colour as "in a large proportional number" of cases 

 constitute diagnostic distinctions between species and 

 species. 



First, then, for the reasons a priori — and they 

 are confessedly a priori — which have been adduced 

 to prove that natural selection has been what in 

 Darwin's opinion it has not been, — " the exclusive 



