The Descent of Man

enveloped in a silken web. The males search
eagerly for the females, and have been seen by
Canestrini and others to fight for possession of
them. This same author says that the union of
the two sexes has been observed in about twenty
species; and he asserts positively that the
female rejects some of the males who court her,
threatens them with open mandibles, and at
last after long hesitation accepts the chosen one.
From these several considerations, we may
admit with some confidence that the wellmarked
differences in colour between the sexes
of certain species are the results of sexual selection;
though we have not here the best kind of
evidence,— the display by the male of his ornaments.
From the extreme variability of colour
in the male of some species, for instance of Theridion
lineatum, it would appear that these
sexual characters of the males have not as yet
become well fixed. Canestrini draws the same
conclusion from the fact that the males of certain
species present two forms, differing from