ARCHITECTURE OF THE GERMPLASM 287 



vestigial wings, the hybrids of the first generation are 

 all like the wild-type parent because gray body and 

 long wings are dominant over black body and vestigial 

 wings. 



Parents 



Gametes 



Gamete* 



FIG. 69. Typical linkage in Drosophila. Symbols as in Fig. 68. 

 Data from Morgan. 



When a male of one of these hybrid flies is crossed 

 back with a recessive black-vestigial female, if Mendelian 

 segregation took place there would be four possible 

 kinds of offspring, as shown in Figure 68, viz., gray- 



