HEREDITY OF SEX 



255 



companying diagram illustrates the behaviour of the 

 chromosomes during these processes. The hetero- 

 tropic chromosomes are represented as black, whilst 

 the remaining chromosomes are left white, and for the 

 sake of simplicity only two pairs of the latter are 

 indicated in the somatic cells. 



o 

 CO 







<*- E 



o o 



to 



c o 



.2 E 

 o 



3 5- 

 IJ- _C 



o 



CL 

 CO 



O 

 00 



Fiff.47. 



ov, ovum ; pb, polar body ; sp, spermatozoa (a and b the two kinds). 



When the above facts are taken into consideration 

 it is scarcely possible to doubt that there is a causal 

 relationship between the characteristics of the female 

 sex and the presence of two heterotropic chromo- 

 somes, and that a similar connection exists between 

 maleness and the presence of only one. Let us trace 

 this relationship a little further. 



