SECT. 7] 



OF EMBRYONIC DEVELOPMENT 



953 



monograph. The third paper of the series was by Farkas, and 

 contained a careful study of the developing silkworm egg from the 

 energetical point of view. He made complete analyses of the eggs 

 before and after their development, the details of which receive 

 consideration elsewhere in this book. For the unincubated egg he 

 got the following values : 



calories per gram 



calories per gram dry weight... 



calories per gram fat 



for the hatched larvae: 



calories per gram 



calories per gram dry weight... 



2163 



6104 (specific energy-content) 



9343 



1631 

 5782 



and for the unused materials, membranes, etc. : 



calories per gram 



calories per gram dry weight... 



4560 

 5301 



Or, in round numbers, expressed differently, i.e. for the whole 

 material : 



Unincubated eggs 

 Hatched larvae 



Unused material, membranes, etc. .. 

 Material lost, i.e. used up during de 

 velopment ... 



Calories 



in the 



material used 



71-402 



31-879 

 22-291 



17-232 



%of 

 the value for 



the unin- 

 cubated eggs 



44-65 

 31-22 



24-13 



The analytical figures showed that 17-32 per cent, of the original 

 dry solid, 48-24 per cent, of the original fat-content, and 0-65 per 

 cent, of the original nitrogen-content had disappeared, so at first 

 sight it seemed certain that the source of the energy utilised had been 

 fat. However, as the nitrogenous end products were not estimated, 

 and as they would remain in the eggs and so form part of the nitrogen 

 value at the end of development, some protein may have been 

 burned too, and perhaps some of the fat was turned into carbo- 

 hydrate, of which no determinations were made. 



From the figures just given, it follows, as 42,220 eggs were used, 

 that in the development of one silkworm egg 0-408 cal. is required 

 for waste or combustion, i.e. the Ea. is equivalent to 0-408 cal. or 

 o- 1 74 mkg. From the same figures the R.Ea. may easily be calculated, 

 and Farkas found that it came to 882 cal., while the S.Ea. was 



