140 Darwin, and after Darwin. 



view of the whole history of Darwinism, what must 

 strike us as the really significant fact is the astonish- 

 ing unanimity which has been so rapidly attained 

 with regard to matters of such immeasurable impor- 

 tance. It is now but little more than thirty years 

 since the publication of the Origin of Species \ and 

 in that period not only have all naturalists unequi- 

 vocally embraced the doctrine of descent considered 

 as a fact ; but, in one degree or another, they have 

 all as unequivocally embraced the theory of natural 

 selection considered as a method. The only points 

 with regard to which any difference of opinion still 

 exist, have reference to the precise causation of that 

 mighty stream of events which, under the name of 

 organic evolution, we have now all learnt to accept as 

 scientifically demonstrated. But it belongs to the 

 very nature of scientific demonstration that, where 

 matters of great intricacy as well as of high generality 

 are concerned, the process of demonstration must be 

 gradual, even if it be not always slow. It is only by 

 the labours of many minds working in many directions 

 that, in such cases, truth admits of being eventually 

 displayed. Line upon line, precept upon precept, 

 here a little and there a little such is the course of 

 a scientific revelation ; and the larger the subject- 

 matter, the more subtle and the more complex the 

 causes, the greater must be the room for individual 

 differences in our reading of the book of Nature. 

 Now, if all this be -true, must we not feel that in the 

 matter of organic evolution the measure of agreement 

 which has been attained is out of all proportion to 

 the differences which still remain differences which, 

 although of importance in themselves, are insignificant 



