343 
“ It is not at all necessary that the several parts of the body 
should have simultaneously varied. Each stag presents individual 
differences, and in the same district those which had slightly heavier 
horns, or stronger necks, or stronger bodies, or were- the most coura 
geous, would secure the greater number of does, and consequently 
leave a greater number of offspring. The offspring would inherit, in a 
greater or less degree, these same qualities, would occasionally inter 
cross with each other or with other individuals varying in some 
favourable manner ; and of their offspring, those which were the best 
endowed in any respect would continue multiplying; and so on 
wards, always progressing, sometimes in one direction and sometimes 
in another, towards the present excellently co-ordinated structure of 
the male elk.”—(The Variatio7i. vol. ii., p. 334.) 
Let us now consider what probability there is that 
Natural Selection, when left alone, will produce results 
similar to those of correlated variation. We must bear 
in mind that the materials on which Natural Selection acts 
are those variations which are necessarily associated with 
reproduction. Now it should be remembered that every 
individual variant whose individuality is the necessary 
result of sexual reproduction, is itself an illustration of the 
action of correlated variation, inasmuch as it is a structure 
all of whose parts are co-ordinated ; so that a relative 
proportion is maintained between the parts, and they are 
able to co-operate in the production of a common work 
useful or necessary for the individual. Here, then, is a co 
ordinated structure ready made, in the production of which 
it is fair to assume that any modification in one part has 
been accompanied with modifications in other associated 
parts. And as each organism which presents itself for 
selection is a co-ordinated structure, so also, if there be any 
truth in the principle under discussion, every transmuta 
tion must be made subject to the principle of correlated 
variation. And yet Mr. Darwin invites us to ignoi'e alto 
gether the principle of correlative variation. “ It is not at 
all necessary that the several parts of the body should