METHOD OF OPERATION 



123 



A B 



A B 



A B 



A B 



A B 



A B 



A B 



A B 



A B 



Figure ig. Change in size of the two members of a pair, A and B, 

 at conjugation, and at two-day intervals after conjugation. At the 

 upper left are shown the relative mean sizes of the two races before 



