248 HEREDITY AND SEX 



chromosomes, and two containing 23 chromosomes ; 

 all four sperms having come from the same spermato- 

 gonial cell (Fig. 121). 



In the female von Winiwarter had difficulty in deter- 

 mining the number of chromosomes present. His 



. v, ,- determination in /Han 



~{~<l 



,;>, 



^7 ** 



/ 



N <">IW|H l '' 







FIG. 121. Diagram of human spermatogenesis. A, spermatogonial 

 cell with 47 chromosomes ; B, first spermatocyte with reduced haploid number 

 and sex chromosome (open circle) ; C, first division ; D, two resulting cells 

 = second spermatocytes ; E, division of second spermatocytes ; F, four 

 resulting spermatozoa, two female-producing (above), two male-produc- 

 ing (below). 



best counts gave 48 chromosomes for the full or duplex 

 number. These observations fit in with the results 

 from the male. 



If these observations are confirmed, they show that 

 in man, as in so many other animals, an internal 

 mechanism exists by which sex is determined. It is 

 futile then to search for environmental changes that 



