74 THE FACTOES OF ORGANIC EVOLUTION. 



been immensely the most important ; and throughout that 

 large part of the animal world characterized by relative 

 inactivity, the survival of individuals that had varied in 

 favourable ways, must all along have been the chief cause 

 of the divergence of species and the occasional production 

 of higher ones. 



But gradually with that increase of activity which we 

 see on ascending to successively higher grades of animals, 

 and especially with that increased complexity of life 

 which we also see, there came more and more into play as 

 a factor, the inheritance of those modifications of structure 

 caused by modifications of function. Eventually, among 

 creatures of high organization, this factor became an 

 important one; and I think there is reason to conclude 

 that, in the case of the highest of creatures, civilized men, 

 among whom the kinds of variation which affect survival 

 are too multitudinous to permit easy selection of any one, 

 and among whom survival of the fittest is greatly inter 

 fered with, it has become the chief factor : such aid as 

 survival of the fittest gives, being usually limited to the pre 

 servation of those in whom the totality of the faculties has 

 been most favourably moulded by functional changes. 



Of course this sketch of the relations among the factors 

 must be taken as in large measure a speculation. We are 

 now too far removed from the beginnings of life to obtain 

 data for anything more than tentative conclusions respecting 

 its earliest stages ; especially in the absence of any clue to 

 the mode in which multiplication, first agamogenetic and 

 then gamogenetic, was initiated. But it has seemed to me 

 not amiss to present this general conception, by way of 

 showing how the deductive interpretation harmonizes with 

 the several inferences reached by induction. 



In his article on Evolution in the Encyclopedia Lritan- 

 nica, Professor Huxley writes as follows : 



&quot; How far natural selection suffices for the production of species 



