86 CREATIVE EVOLUTION [chap. 



then there is the possibility, as we shall explain further 

 on, that the part played by chance is much greater in the 

 variation of plants than in that of animals, because, in 

 the vegetable world, function does not depend so strictly 

 on form. Be that as it may, the neo-Darwinians are 

 inclined to admit that the periods of mutation are deter- 

 minate. The direction of the mutation may therefore 

 be so as well, at least in animals, and to the extent we shall 

 have to indicate. 



We thus arrive at a hypothesis like Eimer's, according 

 to which the variations of different characters continue 

 from generation to generation in definite directions. This 

 hypothesis seems plausible to us, within the limits in which 

 Eimer himself retains it. Of course, the evolution of the 

 organic world cannot be predetermined as a whole. We 

 claim, on the contrary, that the spontaneity of life is mani« 

 fested by a continual creation of new forms succeeding 

 others. But this indetermination cannot be complete; it 

 must leave a certain part to determination. An organ like 

 the eye, for example, must have been formed by just a 

 continual changing in a definite direction. Indeed, we 

 do not see how otherwise to explain the likeness of structure 

 of the eye in species that have not the same history. Where 

 we differ from Eimer is in his claim that combinations 

 of physical and chemical causes are enough to secure the 

 result. We have tried to prove, on the contrary, by the 

 example of the eye, that if there is "orthogenesis" here, 

 a psychological cause intervenes. 



Certain neo-Lamarckians do indeed resort to a cause 

 of a psychological nature. There, to our thinking, is 

 one of the most solid positions of neo-Lamarekism. But 

 if this cause is nothing but the conscious effort of the in- 

 dividual, it cannot operate in more than a restricted num- 

 ber of cases — at most in the animal world, and not at all 



