MAMMALIAN SPERMATOGENESIS — OPOSSUM 



23 



ments, or X-chromosome, go to one pole, while the Y-chromosome 

 goes to the other. No exceptions to this have been noted. 



As a result of the first maturation division, the secondary sper- 

 matocytes all receive 11 chromosomes, but in half of these cells 



Text fig. 4 Showing various stages in the separation of the X- and Y-chromo- 

 some elements in the first maturation division. 



we have the X-element and in the other half the Y-chromosome 

 is present. 



A distinct resting stage follows the first maturation division, 

 as Jordan has described and figured. I fail to find, however, 

 any very striking differences in the nucleoli of such resting cells. 



