e _Modification of Organisms_, p. 46.

There is only one other remark to be made in this connexion. Mr. Syme
chooses two cases as illustrations of the supposed difficulty. These are
sufficiently diverse--viz. Foraminifera and Man. Touching the former,
there is nothing that need be added to the general answer just given.
But with regard to the latter it must be observed that the dominion of
natural selection as between different races of mankind is greatly
restricted by the presence of rationality. Competition in the human
species is more concerned with wits and ideas than with nails and teeth;
and therefore the "struggle" between man and man is not so much for
actual _being_, as for _well-being_. Consequently, in regard to the
present objection, the human species furnishes the worst example that
could have been chosen.

* * * * *

Hitherto I have been considering objections which arise from
misapprehensions of Darwin's theory. I will now go on to consider a
logically sound objection, which nevertheless is equally futile,
because, although it does not depend on any misapprehension of the
theory, it is not itself supported by fact.

The objection is the same as that which we have already considered in
relation to the general theory of descent--namely, that similar organs
or structures are to be met with in widely different branches of the
tree of life. Now this would be an objection fatal to the theory of
natural selection, supposing these organs or structures in the cases
compared are not merely analogous, but also homologous. For it would be
incredible that in two totally different lines of descent one and the
same structure should have been built up independently by two parallel
series of variations, and that in these two lines of descent it should
always and independently have ministered to the same function. On the
other hand, there would be nothing against the theory of natural
selection in the fact that two structures, _not_ homologous, should come
by independent variation in two different lines of descent to be adapted
to perform the same function. For it belongs to the very essence of the
theory of natural selection that a useful function should be secured by
favourable variations of whatever structural material may happen to be
presented by different organic types. Flying, for instance, is a very
useful function, and it has been developed independently in at least
four differen