958 ENERGETICS AND ENERGY-SOURCES [pt. iii 



of a yolk, and which disappears in metamorphosis, Tangl was here 

 making the same mistake as has so often been made by other in- 

 vestigators of closed systems such as eggs. A given substance in- 

 creases in amount, therefore, they say, it cannot be in process of 

 being used up, forgetting that there may be a balance between 

 catabolic and anabolic factors, the net result of which happens to 

 be in favour of the latter. So here, the "fat body" may be responsible 

 for a good deal of Wa. in metamorphosis. 



Tangl used for his work a large supply of the larvae of Ophyra 

 cadaverina, one of the corpse flies, and carried out on it a large 

 number of chemical analyses and bomb calorimeter measurements. 

 Thus, during the 6 days of pupation, looo pupae combusted 3-72 Cal. 

 of energy, or per day 0-62 Cal., and during the 13I days of meta- 

 morphosis the pupae combusted 3-82 Gal., or 0-282 Cal. per day. 

 Thus the energy utilisation per gm. per day during the first period 

 was 57-2 cal., and during the second period 36-0 cal. From his 

 chemical analyses Tangl calculated that, in the pupation period, 88-7 

 per cent, of the energy in the solid burned was provided by fat, and 

 that, in the metamorphosis period, 98-6 per cent, was so provided. 



From the figures given, it follows that during the metamorphosis 

 of the completely pupated larva into the completely free imago 

 3-82 cal, are lost per insect. To this must be added the calorific 

 value of the excrements in the chrysalis and the chrysalis case itself, 

 i.e. 4-44 cal., making a total of 8-26 cal. As the imago when com- 

 pleted weighed 7-32 mgm. (all these values, of course, were averages 

 from a large number of observations) the R.Ea. and the S.Ea. were 

 readily calculable, and came out as follows : 



calories 



R.Ea 523 



S.Ea. ... ... 1566 



though these should perhaps be termed R.Ua. and S.Ua. With these 

 figures Tangl compared some other values which he calculated from 

 the chemical work of Weinland on the fly Calliphora vomitoria thus: 



calories 



Ea. 24-3 



R-Ea 399 



S.Ea 1184 



The agreement was striking, but would have been even more so had 

 Weinland counted the abandoned chrysalis cases as part of the waste. 



