54 H. D. GOODALE. 



In spite of these contradictions, sex is such a well nigh universal 

 attribute of living beings, that there would seem to be some 

 equally common differences between the sexes. It hardly seems 

 reasonable to suppose that femaleness, for example, is one thing 

 in one group and something else in another. But whatever the 

 common difference between maleness and femaleness as such, it 

 by no means follows that this difference of itself determines the 

 sex of an individual. Instead, other factors may be responsible. 



The observations on Ophryotrocha, Inachus, Lychnis and maize 

 afford evidence of the presence of factors which control the 

 patency of sex, so that what is really hermaphrodite may appear 

 to be unisexual. The case of Siline inflata, cited by Correns 

 from Schultze, also points toward the presence of factors which 

 modify hermaphrodites. There are five different types, males, 

 andromonoecious (males and hermaphrodites on the same plant), 

 hermaphrodites, females and gynomoncecious. Moreover, ac- 

 cording to Correns and Shull, crossing hermaphrodites and uni- 

 sexual forms results in dominance of the unisexual forms. 



If we assume that hermaphroditism, which is very much more 

 common in plants and the lower animals than in the higher ani- 

 mals, is the primitive condition, we have a basis from which 

 may be derived the present diverse modes of sex determination. 

 During the course of evolution, various changes have occurred 

 in the gametic constitution of some individuals or modifying 

 factors may have developed, which brings about our present 

 diverse modes for the determination of sex in the individual. 

 That the determination of sex, even from a Mendelian stand- 

 point, is not brought about by the simple interaction of maleness 

 and femaleness, is shown, I think, by the deviations from equality 

 in the sex ratios. In man, for instance, there is a slight but 

 constant excess of males at birth, whereas on the assumption 

 that one sex is heterozygous, the other homozygous, either equal- 

 ity should be expected, or that sometimes the number of female 

 births should exceed the male births. 



Though our present evidence undoubtedly favors the view 

 that the female fowl is a sex heterozygote, it does not necessarily 

 follow that she is therefore a potential hermaphrodite. The 

 hermaphrodite, it is true, may be considered as a sex heterozygote, 



