266 BREEDING 



one is wrong ; or it may be that one sex is hetero- 

 zygous in one species and another in another. But 

 there is another point in which the conclusions derived 

 from these two sources differ. According to the 

 Mendelian conclusion the homozygous sex, which 

 happens to be the male, is a recessive homozygote 

 (RR), whilst according to the cytological the homo- 

 zygous sex, which happens to be the female, all of 

 whose germ-cells possess the " extra " chromosome 

 possessed by only half of the spermatozoon, is a 

 dominant homozygote (DD). Now, if the Mendelian 

 theory, and especially the presence and absence 

 hypothesis, means anything at all, both these con- 

 clusions cannot be true. DD contains two " doses " 

 of the sex factor ; RR contains none. They differ 

 more from one another than a male from a female, 

 as interpreted by Mendelian theory. DR differs 

 from RR only by one " dose." It may be that the 

 homozygous sex is DD in some cases, and RR in 

 others. But this impasse may be due to the initial 

 error of founding a theory of sex, as the Mendelian 

 theory of it has been founded, on a basis of material 

 particles. And it may be that the antithesis is really 

 not between heterozygous and homozygous, i.e. be- 

 tween the presence and absence of particles, but, as 

 the case of the crabs seems to indicate, between an 

 unstable condition and a stable one. 



