498 HEREDITY AND SEX 



reduction of its chromosomes in maturation, get rid of hereditary 

 material antithetic to the dominant tendency. It is conceivable 

 that a young ovum with a cytoplasmic tendency towards male- 

 production may similarly get rid of hereditary material antithetic 

 to the dominant tendency. But what really takes place no one 

 knows. In getting rid of some chromatin material and in keep- 

 ing some a maturing gamete may be dividing its hereditary 

 material in an impartial and random fashion or in a differential 

 fashion. We do not know. 



McClung has suggested that in the maturation of the sperm- 

 cell there may he a quantitative division of the tetrads, re- 

 sulting in two kinds of spermatozoa, comparable to those with 

 and without an accessory chromosome. 



As far as facts go, there does not seem to be any warrant at 

 present for correlating maturation-divisions and sex-determina- 

 tion. 



Fertilisation. — Let us suppose a fertilised ovum to be in 

 process of developing into a female, and let us leave aside, for 

 the moment, the question why it is becoming a female rather 

 than a male. The fact is that it is becoming a female, and if the 

 constitution in potentia has its material basis in the chromosomes 

 of the first cleavage spindle, we may say that these chromosomes 

 are determined in the direction of femaleness — that is, in the 

 direction of an organism producing eggs. Now, on the general 

 theory of germinal continuity, the chromosomes of the germ- 

 cells of this developing female should retain this general tendency 

 and character, unless there are disturbing nutritive or other in- 

 fluences inducing change. Thus some have supposed that the 

 chromosomes of an egg have an inherent bias to produce a 

 female, and that the chromosomes of a spermatozoon have an 

 inherent tendency to produce a male. This seems to us entirely 

 illegitimate, since we adhere to the view that the primary difference 

 between maleness and femaleness is simply a slight difference in 

 metabolism, which may quite well be effected in the course 



