The Descent of Man

les or in the young, would have been of no service
to them, and would not have been selected;
and moreover, if dangerous, would have
been eliminated. Thus the females and the
young will either have been left unmodified, or
(as is much more common) will have been partially
modified by receiving through transference
from the males some of his successive
variations. Both sexes have perhaps been directly
acted on by the conditions of life to which
they have long been exposed: but the females
from not being otherwise much modified, will
best exhibit any such effects. These changes and
all others will have been kept uniform by the
free intercrossing of many individuals. In some
cases, especially with ground birds, the females
and the young may possibly have been modified,
independently of the males, for the sake of
protection, so as to have acquired the same
dull-coloured plumage.
CLASS II.