No. 643] STUDIES ON THE DURATION OF LIFE 



179 



Eesults of Ixbeed Ee-tests for Coxstaxcy 

 During the progress of the experiments described in 

 the preceding section the offspring flies (from original 

 brother X sister matings) in each of tlie lines, whose dura- 

 tion of life was being tested, were allowed to mate at 

 random in their bottles, and their progeny removed to 

 form stocks of the several lines. These stocks were al- 

 lowed to reproduce in stock bottles, all matings being 

 therefore random within the line, for a period of about 7 

 months (cf . Table IV) . At the end of that time it was de- 

 cided to make a re-test of each line to see how it was then 

 behaving relative to duration of life. There was then 

 made, at dates indicated in Table IV, a random selection 

 from each line stock bottle from which a brother and 

 sister pair was bred, and these two individuals were 

 mated to get a set of progeny on which to carry out a sec- 

 ond set of life duration experiments. The necessary 

 facts as to line numbers and dates nn this re-test are given 

 in Table IV. 



TABLE IV 



The survivorship distributions of the progeny groups 

 of this second brother X sister mating are given in Table 

 V, and the biometric constants calculated from the ob- 

 served dx distributions in Table VI. These tables are 

 for comparison with Tables II and III above. 



