original dimorphism of the sheep in this character was retained in both
horned and hornless breeds. We may suppose that the factor for horns had
disappeared entirely from the hornless sheep by a mutation, but in the
horned breed another mutation had been a weakening of the influence of the
sexual hormones on the development of the character, which, as in all such
cases, is really inherited in both sexes. In the _F1_, when the horned
character in the female is only inherited from one side, the hereditary
tendency is not enough to overcome the influence of the absence of the
testis hormone and presence of the ovarian hormone, and so the horns do
not develop. The Mendelian merely sees a relation of the character to sex,
but overlooks entirely the question of the dimorphism in the original
species from which the domesticated breeds are descended. Similarly, with
regard to cattle where it has been found that hornlessness is dominant or
nearly so in both sexes, no reference is made to the opposite fact that
wild cattle have horns in both sexes and are not dimorphic in this
character.

Bateson proceeds to consider colour-blindness as though its heredity were
of similar kind. He refers to it as a male character latent in the female,
remarks that we should expect that disease or removal of the ovaries might
lead to the occasional appearance of colour-blindness in females. He also
discusses the case of _Abraxas grossulariata_ and its variety
_lacticolor_, and other cases of sex-linked heredity, apparently with the
idea that all such cases are similar to those of sexual dimorphism. _A.
lacticolor_ occurs in nature only in the female sex, and when bred with
_grossulariata_ [male] produces [male]'s and [female]'s all
_grossulariata_, these of course being heterozygous. When the _F1
grossulariata_ [male] was bred with the wild _lacticolor_ [female] it
produced both forms in both sexes, and thus _lacticolor_ [male] was
obtained for the first time. When this _lacticolor_ [male] was bred with