345 
Mr. Darwin tells us, on the same page, that “according 
to the doctrine that I maintain, the horns of the male 
elk were slowly gained by sexual selection ” ; and then, 
after describing the conflict for the females, adds that 
“ Natural Selection would thus tend to give to the male 
elk its present structure.” 
In order to bring in the principle of Natural Selection, 
we must assume that the variants produced by sexual 
reproduction are not necessarily organisms composed of 
co-ordinated parts; that Natural Selection will choose 
out here a part in one individual and there a part in 
another individual ; that these will survive and inter 
marry, and thus two elements necessary for the produc 
tion of a co-ordinated structure, similar to that produced 
by correlated variation, will be secured. Thus, to take 
Mr. Darwin’s own illustration, Natural Selection will 
choose out the larger antler of one individual and the 
stronger neck of another. This idea is full of difficulty. 
If there is anything in the principle of correlated varia 
tion, as applied to individuals, the animal with a larger 
antler will either have the stronger neck at birth or the 
neck, compelled to bear the larger weight of the head, 
will increase in strength through the greater demands 
made upon it, so that the correlation will be secured 
before the age of sexual maturity arrives. 
If this were not so, it must be because the variation 
was so slight that any increase of strength in the neck 
was not required. But if so, Natural Selection could not 
select such an individual, because it is inconceivable that 
such a slight difference could make the difference between 
life and death. But, on the other hand, if the head were 
made much heavier and the neck were not strengthened, 
this would be a positive disadvantage to the animal, and 
it would be apt to succumb in the struggle for existence.