LINKAGE 



51 



taken place between black and vestigial in the pair 

 of homologous chromosomes. The numerical results 



OR1T VESTIGIAL 



FIG. 22. Diagram, like that of Fig. 21, to illustrate non-crossing over 

 in the male and crossing over in the female when gray vestigial is mated 

 to gray long (repulsion experiment). The percentage of crossovers here 

 is the same as in Fig. 21 showing that the same percentage results irre- 

 spective of how the factors enter. 



show that this crossing over takes place in about 

 17 per cent, of cases. In other words, the chances are 



