406 



THE AMEBIC AN NATURALIST [Vol. XLIX 



but even amongst tbe females a large percentage of gray 

 reds are normal. The yellow white abnormal class is 

 relatively much more abnormal, i. e., relatively fewer 

 have undergone the transition- 



The results from the reciprocal cross are given in the 

 next table. Here the F x male contains two dominants 

 (GR) and one recessive factor (N). The females GRN 

 YW'Al) carry only one dose of Ab, yet they are largely 

 abnormal. The GRAb are single cross-overs. 



Yellow, Red, Abnormal ? by Gray, White, Normal $ 

 Only one experiment of this kind was made, but as the 



number of F 2 flies was rather large the results may be 



given (Table XIII). 



In this cross the gametes ar 



The F 1 male is GWN and contains, therefore, one domi- 

 nant sex-linked factor, viz., G. Therefore, all of the F 2 



