SEX-LINKED INHERITANCE 



107 



In man the sex formula appears to be XX for the 

 female and XO or XY for the male, and since this 

 is essentially the same as that in Drosophila, the ex- 

 planation of sex-linked inheritance is the same. Ac- 

 cording to de Winiwarter there are 48 chromosomes 



a 



'4 ■' V . 









Fig. 47. — a, speniiatogonimn cell of white man, showing 48 

 chromosomes, including the small F-chromosome; 6, same of 

 negro; c and d. Primary spermatocytes, side views, showing 

 X- and F-chromosomes. {After Painter.) 



in the female and only 47 in the male, the I^-chromo- 

 some being absent. After the extrusion of the polar 

 bodies there should be 24 left in the e^^. In the male 



