68 CREATIVE EVOLUTION CHAP. 



how can they ever agree to arise in every part of the 

 organ at the same time, in such way that the organ 

 will continue to perform its function ? Darwin quite 

 understood this ; it is one of the reasons why he 

 regarded variation as insensible. 1 For a difference 

 which arises accidentally at one point of the visual 

 apparatus, if it be very slight, will not hinder the 

 functioning of the organ ; and hence this first 

 accidental variation can, in a sense, wait for comple 

 mentary variations to accumulate and raise vision to a 

 higher degree of perfection. Granted ; but while the 

 insensible variation does not hinder the functioning 

 of the eye, neither does it help it, so long as the varia 

 tions that are complementary do not occur. How, 

 in that case, can the variation be retained by natural 

 selection? Unwittingly one will reason as if the slight 

 variation were a toothing stone set up by the organism 

 and reserved for a later construction. This hypothesis. 

 so little conformable to the Darwinian principle, is 

 difficult enough to avoid even in the case of an organ 

 which has been developed along one single main line of 

 evolution, e.g. the vertebrate eye. But it is absolutely 

 forced upon us when we observe the likeness of 

 structure of the vertebrate eye and that of the molluscs. 

 How could the same small variations, incalculable in 

 number, have ever occurred in the same order on two 

 independent lines of evolution, if they were purely 

 accidental ? And how could they have been preserved 

 by selection and accumulated in both cases, the same 

 in the same order, when each of them, taken separately, 

 was of no use ? 



Let us turn, then, to the hypothesis of sudden 

 variations, and see whether it will solve the problem. 



1 Darwin, Origin of Species, chap. vi. 



