{Sexual dimorphism} (Biol.), the condition of having one of
the sexes existing in two forms, or varieties, differing
in color, size, etc., as in many species of butterflies
which have two kinds of females.
{Sexual method} (Bot.), a method of classification proposed
by Linn[ae]us, founded mainly on difference in number and
position of the stamens and pistils of plants.
{Sexual selection} (Biol.), the selective preference of one
sex for certain characteristics in the other, such as
bright colors, musical notes, etc.; also, the selection
which results from certain individuals of one sex having
more opportunities of pairing with the other sex, on
account of greater activity, strength, courage, etc.;
applied likewise to that kind of evolution which results
from such sexual preferences. --Darwin.
In these cases, therefore, natural selection seems
to have acted independently of sexual selection.
--A. R.
Wallace.