COORDINATED STRUCTURES 123 



Darwinian explanation to be so great, that he adopted 

 the hypothesis of the inheritance of acquired char- 

 acters, as being the only adequate explanation of the 

 phenomena which was in his time available. 



Unfortunately, satisfactory evidence that such a 

 form of inheritance ever actually takes place has never 

 been forthcoming in sufficient amount to lead to 

 universal conviction. Indeed, at the present day the 

 consensus of opinion among experts is undoubtedly 

 to the effect that acquired characters are not inherited 

 at all, except in so far as better nutrition of the parent 

 may lead to the production of more vigorous off- 

 spring. And it seems clear that such an effect as the 

 latter cannot go on accumulating for more than a few 

 generations. 



Thus we see that in the purely Darwinian view there is 

 something wanting, whilst the Lamarckian explanation 

 is ruled out of court for the present for lack of direct 

 evidence. If, at this point, we find that in Nature a 

 co-ordinated set of structures can and does arise in 

 an already perfected condition at a single step, and 

 that such phenomena take place with sufficient fre- 

 quency to give ample opportunities for the survival 

 of the new type so arising, we have at once discovered 

 an alternative way out of the difficulty. Such a 

 discovery must throw abundant light on the obscurity 

 overshadowing the methods by which evolution has 

 taken place, even though we may not yet have arrived 

 at any kind of explanation of the cause of this phe- 

 nomenon of co-ordinated and definite variability. 



The actual observation of variations of this kind is 



