eed, I
hold to be highly inimical, not only to the progress of biological
science, but even to the true interests of the natural selection theory
itself. As to this I shall have a good deal to say in the next volume.
Here, however, the point is, that the theory in question is often
invoked in cases where it is not even logically possible that it can
apply, and therefore in cases where its application betokens, not merely
an error of judgment or extravagance of dogmatism, but a fallacy of
reasoning in the nature of a logical contradiction. Almost any number of
examples might be given; but one will suffice to illustrate what is
meant. And I choose it from the writings of one of the authors of the
selection theory itself, in order to show how easy it is to be cheated
by this mere juggling with a phrase--for of course I do not doubt that a
moment's thought would have shown the writer the untenability of his
statement.

In his most recent work Mr. Wallace advances an interesting hypothesis
to the effect that differences of colour between allied species, which
are apparently too slight to serve any other purpose, may act as
"recognition marks," whereby the opposite sexes are enabled at once to
distinguish between members of their own and of closely resembling
species. Of course this hypothesis can only apply to the higher animals;
but the point here is that, supposing it to hold for them, Mr. Wallace
proceeds to argue thus:--Recognition marks "have in all probability been
acquired in the process of differentiation for the purpose of checking
the intercrossing of allied forms," because "one of the first needs of a
new species would be to keep separate from its nearest allies, and this
could be more readily done by some easily seen external mark[32]."
Now, it is clearly not so much as logically possible that these
recognition-marks (supposing them to be such) can have been acquired
by natural selection, "for the purpose of checking intercrossing of
allied forms." For the theory of natural selection, from its own
essential nature as a theory, is logically exclusive of the supposition
that survival of the fittest ever provides changes in anticipation of
future uses. Or, otherwise stated, it involves a contradiction of the
theory itself to say that the colour-changes in question were originated
by natural selection, in order to meet "one of the _first_ needs of a
_new_ species," or for the purpose of _subsequently_ preventing
int