422 



THE AMERICAN NATURALIST [Vol. L 



heterozygous for the ten mutant factors used in this group 

 have been recorded. The table only gives the result with 

 respect to nine characters, however, as arc wing was not 

 followed in all of the experiments. (The data given later 

 as to its position have, accordingly, not been calculated 

 from quite as large a count of flies as have the data for the 

 other factors.) 

















Between 



Single Cross-oven 





lible Cross-overs 



db cb a 



