1910] SHULL—INHERITANCE OF SEX IN LYCHNIS Itl 
harmony among the species of a single genus than between a species 
of plants and a species of animals. CASTLE (3) has also attempted 
to relate the Bryonia and Abraxas types of behavior by the assumption 
that in each case the female is the equivalent of the male plus an 
* element, the female in Bryonia being a positive homozygote and 
the male a heterozygote, while in Abraxas the female is a heterozygote 
and the male a negative homozygote. This explanation recognizes 
that Bryonia and Abraxas present fundamentally different conditions. 
It is not my intention to present a general discussion of the present 
state of our knowledge regarding the inheritance of sex, as this has 
been well done recently by Witson (12), CASTLE (3), BATESON (1), 
Doncaster (5), and Morcan (8). However, it may be said that 
the number of studies which have been made in this field are 
entirely too few as yet to warrant far-reaching generalizations on 
the question of sex inheritance, and further data bearing on the sub- 
ject will be awaited with great interest. It has appeared to me that a 
serious criticism can be offered to the results of crosses between Bry- 
onia alba and B. dioica as a basis for conclusions regarding the whole 
problem of sex inheritance. These crosses are interspecific, and, as 
is very often true of crosses between distinct species, the sterility of the. 
F, offspring did not allow any test of the correctness of assumptions 
Tegarding the gametic composition of the hybrids. While it is true 
that in many species-crosses in which the hybrids are fertile, certain 
characteristics segregate normally, it has not been uncommon to find 
that many characters do not segregate, or at least that their segregation 
is very doubtful and obscure. The simple, typical segregation of 
characters is best exemplified by the most closely related forms, 
between which also the fertility is most perfect, and this may be 
expected to hold true of sex characters as well as of other alternative 
characters, 
BATESON (I, p. 166) has repeated the experiments with Bryonia 
and has fully confirmed the results of CoRRENS. BATESON is also 
convinced of the unsafe character of the Bryonia results as a basis 
for generalizations, and says that “the relation of dioecious to her- 
maphrodite and monoecious forms will not in all probability be 
satisfactorily or rapidly elucidated until some case can be found in 
which the two types can be crossed together with a fertile result.” 
