and the fertilisations are therefore
Dd, Dd, dd, dd,
or heterozygote dominants and pure recessives in equal numbers.
It is evident that the reproduction of the sexes is very similar to this. One of the remarkable facts about sex is that, although the uniting gametes are male and female yet they give rise to males and females in equal numbers. If one sex were a dominant this would be in accordance with Mendelian theory. In accordance with the view that the dominant is something present which is absent in the recessive, the Mendelian theory of sex assumes that femaleness is dominant, and that maleness is the absence of femaleness, the absence of something which makes the individual female. If we represent the character of femaleness by F and maleness or the recessive by f, we have the ordinary sexual union represented by
_Ff_x_ff_;
the gametes will then be
F+f and f+f
and the fertilisations
Ff and ff,
or males and females in equal numbers, as they are, at least approximately, in fact.