THE DETERMINATION OF SEX 591 



doubly represented {i.e., in the pure or homozygous condition). 

 Another example is given by the heredity of horns in the cross 

 between Suffolk hornless sheep and Dorset horned, as reported 

 by Wood. 1 Among the descendants of such a cross the females 

 are horned only when both parents have this characteristic, 

 while the males are horned if only one parent be horned. Con- 

 versely, the males are without horns only if the deficiency be 

 received from both parents. In other words, if the factor for 

 the horned character be called " H," in the female the presence 

 of HH means the horned condition, and of H alone the hornless ; 

 while in the male the presence of H means the horned condition, 

 its absence the hornless. 



It would not, I think, be profitable further to pursue the 

 theoretical side of the question at this time, or to take up the 

 question as to what role, precisely, is played by the chromo- 

 somes in sex-production. One possible misconception must, 

 however, be guarded against. The statement that the female 

 is the " plus sex," characterised by the presence of something 

 that is absent in the male, of course does not mean that the 

 female is a more highly developed male. It only expresses the 

 assumption that the presence of a particular factor so affects 

 the germ-cell as to turn the balance of development to the female 

 side, while its absence has the reverse effect. The primary cause 

 is quantitative, but not the effect, or not in the same sense. How 

 the original quantitative factor operates we do not in the least 

 know. 



It will be sufficiently evident that the quantitative hypothesis 

 of sex-determination seems to the writer to give the more in- 

 telligible view of the problem, in so far as it relates to! dioecious 

 organisms ; and this is also the position taken by Morgan in 

 the work on Phylloxera already cited. Further, the principle 

 that is revealed alike by the cytological and the experimental 

 evidence, seems so natural and simple that we may at least 

 hope to see its application much more widely extended than at 

 present. There is a certain temptation in the thought that the 

 sexual differentiation may be rooted in a simple principle of 

 plus and minus that holds true of all sexual organisms, from 

 the lowest to the highest, and may be an expression of a 

 fundamental principle of metabolism. But such a view, how- 

 ever tempting, cannot be accepted, or only with great reserve, 



1 See Bateson, op. cit. 



