108 EVOLUTION AND GENETICS 



at one of the maturation divisions the single X- 

 chromosome passes to one pole. In consequence there 

 are two classes of sperms in man ; female-producing 

 containing 24 chromosomes, and male-producing 

 containing 23 chromosomes. If the factor for color- 



FiG. 48, — Primary spermatocytes of man, side views of spindle. 

 The X- and the F-chromosomes are separating in advance of 

 the others. {After Painter.) 



blindness is carried by the X-chromosome its inher- 

 itance in man works out on the same chromosome 

 scheme and in the same wav as does white eve color 



