BIOCHEMISTRY OF THE SEXUAL ORGANS 281 



The eggs of insects are comparatively rich in phosphorised 

 fats. By extraction with alcohol and ether, Dubois * isolated 

 from locusts' eggs a yellowish oil containing 1*92 per cent, 

 phosphorus. 



Glycogen, purine bases, and cholesterin have been found in 

 the eggs of Bombyx. The changes which take place during 

 incubation, in the chemical composition of these eggs, have been 

 investigated by TichomirofL 2 



The following table shows that a considerable amount of 

 purine bases are formed during incubation. At the same time 

 the fat and glycogen diminish in amount, while the cholesterin 

 remains practically unchanged and the phosphorised fats in- 

 crease slightly in amount. 



On the whole the changes are similar to those observed 

 in hens' eggs, except that glycogen is present in considerable 

 quantities in the egg and disappears during development as well 

 as the fat, while the phosphorised fats are apparently not utilised 

 as a source of chemical energy. The " energy of development " 

 is very considerable, and,, calculated as a percentage of the 

 chemical energy contained in the whole egg, is as great as in the 

 case of the developing hen's egg. 3 



The pigments have been studied especially in the eggs of 

 Crustacea. From the eggs of Maja squinado, Maly 4 isolated 



1 Dubois, " Sur 1'huile d'CEufs d' la Sauterelle d'Algerie (Acridium 

 pzlerinum)," Gomptes Rendus, vol. cxvi., 1893. 



2 Tichomiroff, loc. cit. 



:{ Farkas, " Uber den Energieumsatz des Seidenspinners wahreud der 

 Entwicklung im Ei u. wahrend der Metamorphose," Pjluger's Archiv, 

 vol. xcviii., 1903. See Appendix to this Chapter, p. 302. 



4 Maly, " tiber die Dotterpigmente," Berichte der Akademie der Wissen- 

 schaften, in Wien, vol. Ixxxiii., 1881. 



