112 



T. H. MORGAN 



Of the eight possible combinations, four carry lethal and will 

 not be represented in the male classes of the next generation 

 from the back-cross. The four surviving male clashes represent: 



(1) A non-cross-over class (eosin miniature) 



(2) A single cross-over class (red miniature) 



(3) A single cross-over class (eosin long) 



(4) A double cross-over class (red long) 



W 



M 



W 



X 



M 



w 



M 



u 



Figure F 



