THEORY OF EVOLUTION 



13o 



Blaek veatlgilal 



CXE) 



m~) 



Gametes of Kale 



Game tea of Peoale 



CUD GllD 



CUD CUED CUD dCD 



( h z- ) c B r ) cjrZD CZZD 

 CHD mT) CUD CHD 



BUlCZ TK9TICT'T, 

 41.6 



GRAY LOjrO 

 41. E 



BLACK LONG 

 8.S 



CIUT VESTIGIAL 

 9.6 



Fig. 66. Cross between black vestigial and gray long flies. 

 Two pairs of factors involved in the second group. The F, fe- 

 male is back crossed (to right) to black vestigial male; and 

 the F'j male is back crossed to black vestigial female (to left). 

 Crossing over takes place in the F, female but not in the 

 F, male. 



value under the same conditions is obtained 

 IVoin the same pair of characters. 



