CHAPTER VII. 



ONE of the great changes which has been wrought 

 in biological science by the Darwinian theory of 

 natural selection, consists in its having furnished 

 an intelligible explanation of the phenomena of 

 adaptation. Indeed, in my opinion, thi is the most 

 important function which this theory has had to 

 perform ; and although we still find systematic 

 zoologists and systematic botanists who hold that 

 the chief merit of Darwin's work consists in its 

 having furnished an explanation of the origin of 

 species, a very little consideration is enough to 

 show that such an idea is but a survival, or a 

 vestige, of an archaic system of thought. So long 

 as species were regarded as due to separate acts 

 of creation, any theory which could explain their 

 production by a process of natural evolution became 

 of such commanding importance in this respect, 

 that we cannot wonder if in those days the principal 

 function of Darwin's work was held to be what 

 the title of that work The Origin of Species by 

 means of Natural Selection itself serves to convey. 

 And, indeed, in those days this actually was the 

 principal function of Darwin's work, seeing that in 



