MENDELIAN SEGREGATION 21 



11). If a vestigial gray fly is mated to a long-winged 

 ebony fly, all the offspring (Fi) will have long wings 

 and gray (or slightly darker) body color. If these 

 hybrids (Fi) are inbred, offspring (F2) will be pro- 

 duced in the ratios: 



9 Flies with long wings and gray body color. 

 3 Flies with vestigial wings and gray body color. 

 3 Flies with long wings and ebony body color. 

 1 Fly with vestigial wings and ehony body color. 



In the diagram (Fig. 11) two pairs of chromosomes, 

 the second and the third pairs, are represented by the 

 following conventions: The cross-barred chromo- 

 somes, each of which carries a factor for vestigial, 

 are the second pair. The third pair, that contains 

 the factors for ebony, is represented as black. The 

 third pair of chromosomes in the vestigial fly is 

 ''normal" in respect to ebony. Correspondingly the 

 second pair of chromosomes in the ebony fly is 

 ''normal" in respect to vestigial. 



Each germ cell of the vestigial-gray parent will 

 contain one chromosome with the factor for vestigial 

 and one for gray, and each germ cell of the long- 

 winged ebony parent will contain one chromosome 

 with the factor for long and one for ebony. The 

 hybrid (Fig. 11) will contain, therefore, a pair 

 of chromosomes, one of which carries vestigial, the 

 other long; and will also contain another pair, one of 

 which carries ebony, the other gray. 



In the maturation of the germ cells of the h3^brid, 

 the members of each pair separate from each other 

 as shown in Fig. 11 in the gametogenesis of Fi. 



