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 
