Igtt] SHULL—REVERSIBLE SEX-MUTANTS 363 
character of these plants was purely superficial and did not affect 
the germ cells in any recognizable manner. The only bearing 
these plants have upon the question of sex determination, I think, 
is in the evidence they give that genetically normal males may be 
induced in some unknown way to exhibit female characters. When 
the male is interpreted as a Mendelian heterozygote in respect 
to the sex-producing gene, the occurrence of such a somatic modifica- 
tion has the appearance of a simple case of imperfect dominance, 
such as has been noted not infrequently in other Mendelian hetero- 
zygotes. However, the development of male organs (non-func- 
tional) in the supposedly homozygous female, when the latter 
is attacked by the smut (Ustilago violacea), gives support to the 
_ View held by SrraspurcER (36), that not only the heterozygous 
sex but both sexes contain in some degree the elements of the 
Opposite sex or the capacity to react in the sexually opposite 
Manner. This fact may perhaps indicate that sex is a more 
fundamental condition than might be inferred from the frequency 
with which it behaves as a Mendelian unit character. MorGAN 
(23) suggests a way in which the appearance of the organs or 
characters of one sex in individuals of the opposite sex may be 
explained in harmony with the Mendelian interpretation of sex 
determination. He assumes that there may be present, underlying 
the female sex gene, a male element with respect to which all 
individuals of both sexes are homozygous. This he indicates by 
introducing m into all of his sex formulae. In keeping with com- 
mon usage among geneticists, he should have used M, since he 
intends to denote the presence of maleness. 
While recognizing the aptness of this suggestion in removing 
Some of the difficulties in the way of a general application of the 
Mendelian explanation of sex, I am inclined to the view that the 
Mendelian nature of sex is of secondary rather than of primary 
consequence. May not maleness and femaleness be thought of 
as alternative states, which can be crudely analogized with the 
acidity and alkalinity of chemical solutions? Just as solutions 
may be made acid or alkaline in different ways, either by qualita- 
tive or by quantitative additions, subtractions, or substitutions, 
or by a combination of qualitative and quantitative changes, it 
