A STUDY OF OXYGEN METABOLISM. 



453 



development, apart from those containing fully formed flies 

 unable to escape from the pupal cases, represented the stage of 

 development characteristic of 2-day-old pupae. In other words, 

 the histolytic process had been gone through but the recon- 

 structive had failed of attainment. 



15 



13 



11 



T5 

 I 



15 



13 



11 



FIG. 4. Metabolic rates and pupal weights for pupae of the first experimental 

 period, products of single mating Hd. Upper curve = O2 per pupa; middle curve 

 = Oz per gram; lower curve = pupal weights. Ordinates = Oa values in cu. mm. 

 at left, pupal weights in mg. per 10 pupae at right. Abscissae = numbers of the 

 vials from which experimental pupae were obtained. 



Do flies about to emerge possess a higher standard metabolism 

 than do larvae? Our selected figure throws some light on this 

 question. The elevated rates for the four-day pupae in the 

 figure are certainly in large part to be explained as due to mus- 

 cular contractions incident to emergence of the flies, and ac- 

 cordingly these records do not indicate standard metabolism. 

 When we recall that the figures for the first day of pupal existence 

 are for pupae which may be as old as 15 or 1 6 hours and in which 

 histolysis and its accompanying depression in rate of metabolism 

 has perhaps been in progress for an unknown length of time, 

 it would appear from a comparison of the rates for the first and 



