be explained at all, this
can only be done, so far as we can at present see, by Mr. Darwin's
supplementary theory of sexual selection.

I have now briefly answered all Mr. Wallace's objections to this
supplementary theory, and, as previously remarked, I feel pretty
confident that, at all events in the main, the answer is such as Mr.
Darwin would himself have supplied, had there been a third edition of
his work upon the subject. At all events, be this as it may, we are
happily in possession of unquestionable evidence that he believed all
Mr. Wallace's objections to admit of fully satisfactory answers. For his
very last words to science--read only a few hours before his death at a
meeting of the Zoological Society--were:

I may perhaps be here permitted to say that, after having carefully
weighed, to the best of my ability, the various arguments which
have been advanced against the principle of sexual selection, I
remain firmly convinced of its truth[49].

[49] Since the above exposition of the theory of sexual selection
was written, Mr. Poulton has published his work on the _Colours of
Animals_. He there reproduces some of the illustrations which occur
in Mr. and Mrs. Peckham's work on _Sexual Selection in Spiders_, and
furnishes appropriate descriptions. Therefore, while retaining the
illustrations, I have withdrawn my own descriptions.

Mr. Poulton has also in his book supplied a _resume_ of the
arguments for and against the theory of sexual selection in general.
Of course in nearly all respects this corresponds with the _resume_
which is given in the foregoing pages; but I have left the latter as
it was originally written, because all the critical part is
reproduced _verbatim_ from a review of Mr. Wallace's _Darwinism_, of
a date still earlier than that of Mr. Poulton's book--viz.
_Contemporary Review_, August, 1889.

_Concluding Remarks._

I will now conclude this chapter, and with it the present volume, by
offering a few general remarks on what may be termed the philosophical
relations of Darwinian doctrine to the facts of adaptation on the one
hand, and to those of beauty on the other. Of course we are all aware
that before the days of this doctrine the facts of adaptation in organic
nature were taken to constitute the clearest possible evidence of
special design, on account of the wonderful mechanisms which they
everywhere displa