J 



60 Da7"win, and after Dariuin. 



view of adaptation. Still, on the doctrine of chances, 

 it is to be expected that sometimes a change of 

 structure which has thus been indirectly produced by 

 correlation of growth might happen to prove useful 

 for some purpose or another ; and in as many cases 

 as such indirectly produced structures do prove useful, 

 they will straightway begin to be improved by the 

 direct action of natural selection. In all such cases, 

 therefore, we should have an explanation of the origin 

 of such a structure, which is the only point that we 

 are now considering. 



I think, then, that all this effectually disposes of 

 the doctrine of " prophetic germs." But, before 

 leaving the subject, I should like to make one 

 further statement of greater generality than any which 

 I have hitherto advanced. This statement is. that we 

 must remember how large a stock of meaningless 

 structures are always being produced in the course of 

 specific transmutations, not only by correlation of 

 growth, which we have just been considering, but also 

 by the direct action of external conditions, together 

 with the constant play of all the many and complex 

 forces internal to organisms themselves. In other 

 words, important as the principle of correlation 

 undoubtedly is, we must remember that even this is 

 very far from being the only principle which is con- 

 cerned in the origination of structures that may or may 

 not chance to be useful. Therefore, it is not only 

 natural selection when operating indirectly through 

 the correlation of growth that is competent to produce 

 new structures without reference to utility. In all 

 the complex action and reaction of internal and ex- 

 ternal forces, new variations are perpetually arising 



