The Descent of Man

secretion from the gland is not poisonous; and
on the leg of the female there is a hollow, apparently
for the reception of the spur. (7. Owen on
the cachalot and Ornithorhynchus, ibid. vol. iii.
pp. 638, 641. Harting is quoted by Dr. Zouteveen
in the Dutch translation of this work, vol.
ii. p. 292.)
When the males are provided with weapons
which in the females are absent, there can be
hardly a doubt that these serve for fighting
with other males; and that they were acquired
through sexual selection, and were transmitted
to the male sex alone. It is not probable, at least
in most cases, that the females have been prevented
from acquiring such weapons, on account
of their being useless, superfluous, or in
some way injurious. On the contrary, as they
are often used by the males for various purposes,
more especially as a defence against their
enemies, it is a surprising fact that they are so
poorly developed, or quite absent, in the fema-