CALVIN B. BEIDGES 



balance against these flies an equal number in which vestigial 

 occurs as a non-crossover. In this case the error will be the 

 opposite of the previous one, and by combining the two experi- 

 ments the errors should balance and give a better approach 

 to the true value. If each class is thus balanced the error should 



TABLE 2 

 Pi purple X vestigial. B. C. Fj wild type 9 X purple vestigial c? & 



TABLE 3 



Linkage of purple and vestigial with balanced viability (Ists) 



