386 THE AMERICAN NATURALIST [Vol. LVI 



In the systematic survey which we are making-, at the 

 beginning of our experimental study of duration of life, 

 it seemed desirable to test the influence upon this char- 

 acter of degree of natural ventilation of the bottles. It 

 is the purpose of this first section of this paper to pre- 

 sent the results of some experiments on this point. 



Material and Methods 



The experiments were carried out in two series. For 

 the first, wild type flies of our Old Falmouth stock 

 (Pearl and Parker (27)) belonging to Line 107, the dura- 

 tion of life constants of which have been given by Pearl 

 and Parker (32), were used. These flies were of the 25th 

 pedigreed generation. Eighteen mass matings of the 

 flies of this line were started for the present experiments 

 on March 13, 1922, and the flies to be used emerged 

 March 23-30, 1922. 



For the second series short-lived flies of Quintuple 

 stock (Pearl and Parker (27)) were used, in the 27th 

 pedigreed generation. Twenty-five mass matings of 

 Quintuple line 405 were started April 10, 1922, and six 

 mass matings of mixed Quintuple stock were started 

 April 11, 1922. The flies for use in the experiment 

 emerged April 22-27, 1922. 



The procedure in making up the experiments was as 

 follows: The flies were counted out each morning upon 

 emergence into our standard one ounce screw top shell 

 vials used in the determination of duration of life (Pearl 

 and Parker (27)). Fifty flies were put in each bottle. 

 The wild type flies were counted in through the counting 

 tube described in these Studies, III (Pearl and Parker 

 (44)). The Quintuple flies move through the tube so 

 slowly, however, that there is time for moisture to con- 

 dense and accumulate on the walls of the tube, killing 

 some of the flies by drowning, and injuring others. Con- 

 sequently the flies of this type were etherized and 

 counted into the bottles. It has been shown in these 

 Studies, III, that such etherization has no measurable 



