1911] SHULL—REVERSIBLE SEX-MUTANTS 361 
by males not derived from a hermaphrodite family. These 11 
males appeared in hermaphrodite families comprising a total of 
5467 individuals, thus possibly indicating a somewhat greater 
coefficient of mutability than that reported for the production 
of hermaphrodites from normal males. It seems therefore that the 
Modification of the gene M (or f) into a hermaphrodite gene H, 
and the reversal of this modification so that a normal male gene 
is again produced from a hermaphrodite gene, occurs with somewhat 
unequal facility, but the difference is not great enough to warrant 
the belief that mutation in the one direction is caused by the 
appearance of a new, independent organ, while its reversal is due 
to the disappearance of that organ. It seems to me more probable 
that these reversible mutations are due to reversible modifications 
of an element or organ continuously in existence, and not to the 
Production of a new element or the dropping out of an old one. 
The change from a male to a hermaphrodite condition and the. 
_ Feverse are processes both striking and sudden. Perhaps they are 
as fundamental mutations as those observed among the oenotheras. 
The interpretation given here of the process of mutation in the 
Sex character of Lychnis seems to be available for other mutations 
as well. The sudden acquirement of new functions by a gene 
already in existence is different from the conception presented by 
E Vries in Die Mutationstheorie, to account for the origin of 
the Oenothera mutants, and is in accord with SprttMan’s “teleone 
hypothesis.” Sprrrman (30) is inclined to attribute the remarkable 
mutations in Oenothera to irregularities of mitosis, but in these 
Sex Mutants of Lychnis, abrupt genotypic modifications have 
taken place which can hardly be assigned to such irregular mitoses. 
One puzzling feature of the inheritance of sex in Lychnis is 
the fact that self-fertilized hermaphrodites produce similar ratios 
of females and hermaphrodites as are produced when unrelated 
females are fertilized by sperms from hermaphrodites. Since it is 
obvious that the two types of offspring are due to the heterozygous 
character of the male, we are led to the conclusion that even though 
the hermaphrodite individual is heterozygous in respect to sex, 
its egg cells? are of a single type like those of the normal female 
* Perhaps I should say “its successful egg cells.” 
