INDEPENDENT MENDELIAN INHERITANCE 75 
our shorthand notation they will all be (WX). On the other hand, 
the white-eyed male will produce sperm cells half of which have an X- 
chromosome and half a Y-chromosome. The X-chromosome of the sperm 
cells carries a factor w for white eyes, but the Y-chromosome does not bear 
Fic. 35.—Inheritance of white eye color in Drosophila. Red-eyed female mated to 
white-eyed male. Solid lines indicate history of chromosomes of female; dotted and 
gray lines, of the male. (Adapted from Morgan.) 
this factor. In the shorthand notation these two kinds of sperm are rep- 
resented by (wX) and Y respectively. The Y-chromosome is drawn in 
black to indicate its unknown constitution with respect to the factors it 
contains. When an egg-cell (WX) of the red-eyed female is fertilized 
by a (wX) sperm cell, a female is produced of the genetic constitution 
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