Vellow 

 Female 



Gray 

 Male 



Parents XX 



XY 



Germ V y 

 Cells 1^ 1^ 



Fi XX XX XY XY 



Gray Females Yellow Males 



Figure A 



Yellow 

 Female 



Gray 

 Male 



Parents XX 



XY 







Y 



)0(Y + XXX XO YO 



Dii 



Figure 26, A and B. Diagrams to illustrate inheritance through 

 the X-chromosomes, in cases in which the distribution of the X's is 

 normal (figure 26A), and in those in which the two X's of the fe- 

 male are united, so that they go together to the same germ cell 

 (figure 26B). The underlined X's are recessive, producing yellow; 

 those not underlined are dominant, producing gray. The two X's 

 having a bar above them (in B) are the united X's, both going to 

 the same germ cell, and leaving other germ cells (O) without X or Y. 

 Figure 26, A, normal distribution: sons like the mother, daughters 

 like the father. Figure 26, B, abnormal distribution: sons like the 

 father, daughters like the mother. See text. 



92 



