to each other, is proof are these characters are not gametogenic, but were
originally due to external stimulation of particular parts of the soma.



CHAPTER IV

Origin Of Somatic Sex-Characters In Evolution


In his _Mendel's Principles of Heredity_, 1909, Bateson does not discuss
the nature of somatic sex-characters in general, but appears to regard
them as essential sex-features, as male or female respectively. As
mentioned above, he argues from the fact that injury or disease of the
ovaries may lead to the development of male characters in the female, that
the female is heterozygous for sex, and from the supposed fact that
castration of the male leads merely to the non-appearance of male somatic
characters, that the female sex-factor is wanting in the male. He does not
distinguish somatic sex-characters from primary sex-factors, and discusses
certain cases of heredity limited by sex as though they were examples of
the same kind of phenomenon as somatic sex-characters in general. One of
these cases is the crossing by Professor T. B. Wood of a breed of sheep
horned in both sexes with another hornless in both sexes. In the _F1_
generation the males were horned, the females hornless. Here, with regard
to the horned character, both sexes were of the same genetic composition,
_i.e._ heterozygous, or if we represent the possession of horns by _H_,
and their absence by _h_, both sexes were _Hh_. Thus _Hh[male]_ was horned
and _Hh[female]_ was hornless, or, as Bateson expresses it, the horned
character was dominant in males, recessive in females. Bateson offers no
explanation of this, but it obviously suggests that some trace of the