112 RESPIRATORY EXCHANGE OF ANIMALS AND MAN 



cess itself must be responsible for the large metabolism during the 

 first stage. The facts as known are not sufficient to warrant either 

 conclusion, and it is just as possible that the metabolism is proportional 

 at each stage to the amount of organized " living " tissue present. 



Krogh [1914] has made similar determinations on the chrysalides 



'0 60 80 200 



-From " Zeit. f. allgem. Physiol." 



of a beetle (Tenebrio^ the meal-worm) and obtained curves of the same 

 general form (fig. 32). These chrysalides are able to make move- 

 ments of the abdomen during the first stage but practically never do 

 it except when stimulated. Krogh determined the total metabolism 

 (production of carbon dioxide) together with the duration of the pupal 

 life at different temperatures. The results are given in Table XXIV. 



TABLE XXIV. 



At the four temperatures investigated the incubation time varies 

 from 138 to 320 hours, but the total production of carbon dioxide is 

 practically the same in all cases. The cost of production of the imago 

 or the " work of development" in the sense of Tangl is independent 

 of the temperature. If it had been lower at a certain temperature 

 than at others, as was expected when the investigation was under- 

 taken, that temperature would have been an optimum temperature for 



