466 DIRECTIVE FACTORS IN EVOLUTION: 



with all its tremendous consequences in regard to the evo- 

 lution of mind, is an outgrowth of the differentiation of sex." 

 There can be little doubt that the biology of the future will 

 attach not less but more importance to sexual selection. 

 For it seems likely that characters and qualities originally 

 established in this way have often influenced both body and 

 behaviour in reaches now more or less remote from the tides 

 of sex-impulses. 



§ 8. Selection and Progressiveness. 



There is a very important reason why we should keep 

 in mind the relation of Natural Selection to the Systema 

 Naturae which has been gradually evolved, which is continu- 

 ally becoming more complex, which is made up of numerous 

 components, mostly stable and beautiful, often intelligent 

 and purposeful. The reason is that we have here part of 

 the explanation of the progressiveness of evolution. For, 

 while there are blind alleys and other paths that turn back 

 on themselves, the large fact is that on the whole evolution 

 has been in the direction of increased differentiation and 

 integration, of growing mastery and freedom. In this way 

 Nature has led up to Man, her minister and interpreter. But 

 how was it effected ? 



It may be that part of the secret is insoluble, that it is 

 wrapped up with a tendency to complexify which may be 

 seen even in the inorganic, where corpuscles form atoms 

 and these molecules, where small molecules form large ones, 

 and large molecules colloid masses, and so on. A fortiori 

 it may be inherent in the very nature of an organism to 

 complexify, to differentiate. 



We could suggest, however, that part of the riddle is 

 solved when we carefully observe the process of Natural 



