EVOLUTION 377 



element. But while we cannot neglect certain bathmic 

 factors in evolution, to assume that evolution, either in the 

 main or even considerably, is due to the organic ante- 

 cedents of a particular type of life rather than to the 

 physical environment of life is without doubt unscientific. 

 The physical evolution would then be fixed by physical 

 causes and the organic evolution by organic causes, 

 but what is then to preserve the unison between 

 the two evolutions ? Are we to suppose them like two 

 clocks wound up independently and keeping the same 

 time ? Why should the " inherent growth-force " produce 

 the right variation at the right time and in the right 

 place ? To assume that it does so, is fundamentally 

 unscientific ; we propound a new cause, when the old ones 

 have not yet been shown to be insufficient, — in other 

 words, we blunt " Occam's razor " (Appendix, Note III.). 

 If, on the other hand, we take refuge in one of our clocks 

 being controlled by the other, i.e. assert that the environ- 

 ment controls the bathmic tendency in variation, so that 

 the tendency towards the type suitable to the environment 

 only receives freedom to come into play when the environ- 

 ment is suitable, we seem lost in a verbal maze. For 

 there must be endless tendencies then in the primitive 

 form of life, each of which could have come into play with 

 different sequences of environment, and we seem no longer 

 to have the " inherent growth-force " giving variation a 

 definite bias and evolution a definite direction such as the 

 bathmic evolutionists demand ! We are indeed wonder- 

 fully close to the random variation and selection due to the 

 environment, i.e. to the explanation given by Darwin him- 

 self. 



§ 4, — The Factors of Evolution 



It seems to me, then, that we cannot seek for a theory 

 of evolution in the immediate organic antecedents of any 

 type of life, or in an "inherent growth -force." Bathmic 

 elements there are, which must be appealed to when we 

 discuss variation, inheritance, and reproduction, but they 

 do not suffice to describe progressive change of type. We 



