INHERITANCE OF SEX 259 



ova, one kind which, when fertilised, will give rise to 

 males, and another which, when fertilised, will give 

 rise to females. The former, the male-producing, 

 arise in the right ovary, and the latter, the female- 

 producing, in the left ovary. So that about equal 

 numbers of the two kinds are given off. When a 

 woman is once mature, an ovum is produced alter- 

 nately from each ovary, one at a time, at each 

 ovulatory period; a male-producing one from the 

 right ovary ; next month a female -producing one from 

 the left ; next, a male from the right ; then a female 

 from the left again, and so on. So that when a woman 

 has had one child imder such circumstances that the 

 date of the ovulatory period at which the egg, from 

 which the child developed, was extruded from the 

 ovary can be calculated, the sexes of any future 

 children required may be arranged. The evidence 

 adduced for the allocation of the male- and female- 

 producing ova to the right and left ovaries respectively 

 cannot yet be considered to have proved the point ; 

 nor is the point necessary for our purpose. What 

 is of intense interest is the fact that clinical obser- 

 vations conducted in complete ignorance of Mendelian 

 speculation should have led to the enunciation of a 

 theory of sex which is practically identical with the 

 Mendelian one, The two theories, at any rate, have 

 these points in common. According to both, one sex, 

 the female, produces two kinds of germs, male-produc- 

 ing and female-producing, in equal numbers, whilst the 

 male only produces germ- cells of one kind. The sex, 

 therefore, is determined by the female. Dr. Dawson's 



