No. 646] 



THE DURATION OF LIFE 



387 



influence on duration of life. Each day's flies were di- 

 vided equally between control and experimental groups. 

 Fertility in the Quintuple flies is so low that even with 

 the large number of matings the hatches on some days 

 did not equal 100 flies. It thus resulted that there were 

 a few bottles of the Quintuples with fewer than 50 flies 

 to the bottle : 1 case with 40 flies in control and 40 in the 

 experimental bottle, 1 with 37 flies in each bottle, and 1 

 with 23 flies in each bottle. 



The control bottles were plugged with cotton in the 

 ordinary way. The experimental, ventilated bottles 

 were covered with one layer of silk bolting cloth of No. 

 48 mesh (48 meshes to the linear inch), this being the 

 largest mesh which could be used without any possibility 

 of a fly squeezing through the openings. The cloth was 

 held firmly and evenly in place by an aluminum screw 

 cap in the top of which a central hole a little more than 

 % inch in diameter had been punched out. This is 

 practically the internal diameter of the shell vials which 

 we use. 



Both control and ventilated bottles were carried in 25° 

 incubators, and all other procedure was that which has 

 been described by the authors (27) as standard in the 

 work of this laboratory on duration of life in Drosophila. 



Results 



The observed L distributions (survivors out of 1,000 

 starting together) for the wild type Old Falmouth Line 

 107 are given in Table I, together with the absolute num- 

 bers of flies on which the distributions are based. 



These distributions of Table I are shown graphically 

 in Fig. 1. 



It is evident at once that the flies in the well-ventilated 

 bottles outlive those in the ill-ventilated. Their expecta- 

 tion of life is greater at every age. The magnitude and 

 significance of this difference can best be appreciated 

 from the constants of duration of life set forth in Table 

 II. 



