68 CREATIVE EVOLUTION [chap. 



system of complementary changes for the plant to remain 

 fit to survive. But it is not so in the animal, especially 

 in the case of an organ like the eye, a very complex struc- 

 ture and very delicate function. Here it is impossible 

 to identify changes that are simply solidary with changes 

 which are also complementary. The two senses of the 

 word "correlation" must be carefully distinguished; it 

 would be a downright paralogism to adopt one of them 

 in the premisses of the reasoning, and the other in the con- 

 clusion. And this is just what is done when the principle 

 of correlation is invoked in explanations of detail in order 

 to account for complementary variations, and then cor- 

 relation in general is spoken of as if it were any group of 

 variations provoked by any variation of the germ. Thus, 

 the notion of correlation is first used in current science 

 as it might be used by an advocate of finality ; it is under- 

 stood that this is only a convenient way of expressing one- 

 self, that one will correct it and fall back on pure mechan- 

 ism when explaining the nature of the principles and turn- 

 ing from science to philosophy. And one does then come 

 back to pure mechanism, but only by giving a new meaning 

 to the word "correlation" — a meaning which would now 

 make correlation inapplicable to the detail it is called 

 upon to explain. 



To sum up, if the accidental variations that bring about 

 evolution are insensible variations, some good genius must 

 be appealed to — the genius of the future species — in order 

 to preserve and accumulate these variations, for selection 

 will not look after this. If, on the other hand, the acci- 

 dental variations are sudden, then, for the previous function 

 to go on or for a new function to take its place, all the 

 changes that have happened together must be comple- 

 mentary. So we have to fall back on the good genius 

 again, this time to obtain the convergence of simultaneous 



