i 9 to] SHULL INHERITANCE OF SEX IN LYCHNIS in 



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 

 x 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 WILSON (12), CASTLE (3), BATESON (i), 

 DONCASTER (5), and MORGAN (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 

 regarding 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." 



