or a strong preference for, certain
individuals of the opposite sex.

Such are the main lines of evidence in favour of the theory of sexual
selection. And although it is enough that some of them should be merely
stated as above in order that their immense significance should become
apparent, in the case of others a bare statement is not sufficient for
this purpose. More especially is this the case as regards the enormous
profusion, variety, and elaboration of sexually-embellishing characters
which occur in birds and mammals--not to mention several divisions of
Arthropoda; together with the extraordinary amount of trouble which, in
a no less extraordinary number of different ways, is taken by the male
animals to display their embellishments before the females. And even in
many cases where to our eyes there is no particular embellishment to
display, the process of courtship consists in such an elaborate
performance of dancings, struttings, and attitudinizings that it is
scarcely possible to doubt their object is to incite the opposite sex.
Here, for instance, is a series of drawings illustrating the courtship
of spiders. I choose this case as an example, partly because it is the
one which has been published most recently, and partly because it is of
particular interest as occurring so low down in the zoological scale. I
am indebted to the kindness of Mr. and Mrs. Peckham for permission to
reproduce these few selected drawings from their very admirable work,
which is published by the Natural History Society of Wisconsin, U.S. It
is evident at a glance that all these elaborate, and to our eyes
ludicrous, performances are more suggestive of incitation than of any
other imaginable purpose. And this view of the matter is strongly
corroborated by the fact that it is the most brightly coloured parts of
the male spiders which are most obtruded upon the notice of the female
by these peculiar attitudes--in just the same way as is invariably the
case in the analogous phenomena of courtship among birds, insects, &c.

[Illustration: FIG. 122.--Courtship of Spiders. A few examples of
some of the attitudes adopted by different species of males when
approaching their females. (After Peckham.)]

[Illustration: FIG. 123.--Courtship of Spiders. Continued from Fig.
122, similarly showing some of the attitudes of approach adopted by
males of yet other different species. (After Peckham.)]

But so great is the mass o