34i
But if Natural Selection sometimes takes a part in this
business and sometimes does not, it is obvious that it is
not an essential factor ; and, in short, that the modification
of one part will lead to the correlated variation of other
parts, whatever be the cause of the modification of the one
part. Correlated variation is the ready ally of any trans
forming cause which may operate on a particular part ; it
is not, and it never ought to be represented as, the special
coadjutor of Natural Selection. Even if Natural Selection
did inaugurate such change, which there is some reason to
doubt, it would only produce a result which is achieved by
many other influences ; and when it came into action
it would play, after all, only a very small part in the
totality of the effect produced.
Mr. Darwin further states that the results of correlated
variation may be mastered by Natural Selection.
“ These tendencies, I do not doubt, may be mastered more or less
completely by Natural Selection. Thus a family of stags once
existed with an antler only on one side ; and if this had been of
any great use to the breed, it might probably have been rendered
permanent by selection.”—(Origin of Species, p. nj.)
Now it is quite clear that Natural Selection did not
produce this exception to the rule of correlated modifica
tion ; and, as there is no reason to suppose that one
antler is more useful than two, there is no kind of proba
bility that Natural Selection should have had anything to
do with rendering such a modification permanent in a race.
Moreover the perpetuation or the non-perpetuation of a
variation like this depends upon its being inherited by
offspring. But it is probable that such an exceptional
phenomenon will not be inherited, the co-ordinated struc
ture of the race asserting itself over the non-correlated
peculiarity of the individual ; or, if inherited, it will tend
to die out of itself, unless the variant should have the