PRESIDENTIAL ADDRESS. 255 



its present structure, yet it is probable that the inherited 

 effects of use, and of the mutual action of part on part, 

 have been equally or more important ; " and this can hardly 

 be regarded as very emphatic rejection ! Of course it is 

 open to the thorough-going Darwinian to say that the result 

 has been reached by the selection of now one, now another, 

 and subsequently yet other sets of correlated variations or 

 co-adaptations, not produced by, but chancing to coincide 

 with, effective utility. It would seem, however, that the 

 occurrence of such co-adaptive sets of variations might fairly 

 be regarded as indicative of directed or determinate variation, 

 however originating. And in general the facts of corre- 

 lation and co-adaptation seem, so far as they go, to point 

 to determinate variation. 



Still it may fairly be urged that such determinate 

 variation may itself be the outcome of a long course of 

 natural selection. If the individuals in which an adaptive 

 correlation a h n t occurred were there b}^ placed among the 

 survivors, while the individuals in w^hich the non-adaptive 

 correlations a c in .s, ah q 2, etc., occurred were thereby 

 placed on the elimination list, it is clear that there would 

 be ingrained in the species a tendency for the correlation 

 a h n t to occur. Thus in a horned animal size of antlers 

 and strength of supporting structures would be correlated ; 

 these again with proper blood-vessels and nerves ; and so 

 on. And again, in the ancestor of the giraffe, a number 

 of co-adapted correlations would already be established, and 

 these would form a sufficient basis for variation in the 

 direction of the special and peculiar co-adaptations in the 

 giraffe itself. In other words, even if the determinateness 

 of the variations in any species be established, it does not 

 follow that this is not the result of long selection among 

 variations primitively indeterminate. 



