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THE AMERICAN NATURALIST [Vol. LVI 



DuKATiox OF Life in Different Progeny Groups out of 

 Brother X Sister Matings 

 The survivorship data (L frequencies) for 7 progeny 

 groups each out of a mating of brother X sister are ex- 

 hibited in Table II. All distributions are put on the same 

 basis of 1,000 flies at emergence from the pupal stage. 

 The absolute numbers of flies involved in each experiment 

 are given at the foot of each column. These numbers are 



TABLE I 



