CHROMOSOMES OF HUMAN SPERMATOCYTES 13 



(). The second spermatocyte iiietaphase plates contain 12 

 chromosomes, one of which can be recognized as a half of the 

 split XY pair. In the division it is assmned that the X and Y 

 constituents pass undivided to opposite poles while the remain- 

 ing 11 chromosomes all divide. The result would be that one 

 half the spermatids receive 11 ordinary chromosomes plus X 

 and the other half 11 plus Y. 



7. The number and behavior of the chromosomes in the sper- 

 matogenesis of the white and negro races of man is the same in 

 the material studied. 



LITERATURE CITED 



Allen, Ezra 1916 II Experiments on technique, witli description of a method 

 for demonstrating the cytological details of dividing cells in brain and 

 testes. Anat. Rec, x, 9, 1916. 



GuYER, M. F. 1910 Accessory chromosomes in man. Biol. Bull., xix, no. 4, 

 1910. 



GuYER, i\I. F. 1914 Accessory chromosomes in man. Science, xxxix, 1914. 



Montgomery, T. H. 1912 Human spermatogenesis, spermatocytes and sper- 

 miogenesis: a study of inheritance. Jour. Acad. Nat. Sci. of Phila- 

 delphia, XV, 1912. 



Morgan, T. H. 1914 Chromosomes of the white man and the negro. Science, 

 xxxix, 1914. 



VON Winiwarter, H. 1912 Etudes sur la spermatogenese humaine. I. Cellule 

 de Sertoli. II. Heterochromosome et mitoses de 1' epithelium seminal. 

 Arch. d. Biol., xxvii, 1912. 



