4 JOSEPH HALL BODINE AND PAUL RUDBERT ORR. 



ula has been found a most convenient instrument for handling the 

 organisms. In weighing pupae a delicate analytical balance was 

 used. 



Since the purpose of the present investigation was primarily to 

 determine the rates of oxygen consumption and carbon dioxide 

 output of the different stocks of flies, it was necessary to have 

 methods accurate and delicate enough to measure the respiratory 

 exchange of such small organisms. The following types of ap- 

 paratus were found to fulfill these requirements. 



For oxygen determinations a modified Krogh (4) micro-respira- 

 tion apparatus was used. The accompanying diagrams and ex- 

 planations show the apparatus as finally adopted. For the meth- 

 ods of using the apparatus, derivation of formulae, etc., the reader 

 is referred to Krogh's (4) complete descriptions and explanations. 



Carbon dioxide determinations were made by the Haas (5) in- 

 dicator method, using suggestions pointed out by Jacobs (6) . A 

 decided improvement over the method as suggested by Jacobs, 

 however, is apparatus made entirely of hard glass with no rubber 

 stoppers or connections. The accompanying diagrams and ex- 

 planations show some of the various types of apparatus employed. 

 For methods of calculating results, etc., with this method the 

 reader is referred to the article by Jacobs (6) . 



Analyses of the air in culture bottles were made with a Haldane 

 gas apparatus (7), the sample of air being slowly drawn out of 

 the bottle into the apparatus by means of a capillary tube. 



ANALYSIS OF AIR IN CULTURE BOTTLES. 



Pearl and Parker (3) in recent studies on duration of life in 

 Drosophila have pointed out that in the case of wild type, ' . . . 

 an increase of roughly 10 per cent, in the mean duration of life 

 is brought about by increasing the ventilation of culture bottles, 

 by covering the mouth with one layer of number 48 mesh bolting 

 cloth as compared with the use of cotton plug stoppers as is the 

 usual practice in cultures of Drosophila in the laboratory." Sim- 

 ilar experiments were also carried out by these authors using 

 Quintiple type flies and no such differences in duration of life 

 were noted. Inasmuch as these authors report no analyses of the 

 air contained in culture bottles with such stoppers it was thought 



