The Descent of Man

arise in the female line, and to be transmitted
exclusively in this line, they would be extremely
liable to be lost. If, however, the females varied
and transmitted their newly acquired characters
to their offspring of both sexes, the characters
which were advantageous to the males
would be preserved by them through sexual
selection, and the two sexes would in consequence
be modified in the same manner, although
such characters were of no use to the
females: but I shall hereafter have to recur to
these more intricate contingencies. Lastly, the
females may acquire, and apparently have often
acquired by transference, characters from
the male sex.
As variations occurring later in life, and transmitted
to one sex alone, have incessantly been
taken advantage of and accumulated through
sexual selection in relation to the reproduction
of the species; therefore it appears, at first sight,
an unaccountable fact that similar variations