1238 METABOLISM OF LIPOIDS, STEROLS, [pt. m 



but it must be remembered that hatching occurs very early in the frog. 

 Faure-Fremiet & Dragoiu found that 25' 13 per cent, of the total fatty 

 acids were in the form of phosphatides at the beginning and 20-o per 

 cent, at hatching, 



loss by % of 



I egg (mgm.) initial value 

 Unsaturated acids ... 0-0838 30-0 



Myristic acid o-ooig 2-7 



Phosphatides ... ... 0-0444 42'0 



No determinations of lipoid phosphorus were made by Faure-Fremiet 

 & Dragoiu at the end of the second period, i.e. at the time of dis- 

 appearance of the yolk-sac. There is general agreement, therefore, 

 that the lipoid phosphorus diminishes during the development of the 

 amphibian egg, but little is known about the behaviour of the other 

 phosphorus fractions. 



The cholesterol of the frog's egg has been occasionally investigated. 

 Faure-Fremiet & Dragoiu found the total unsaponifiable fraction of 

 their ether-alcohol extract to amount to 3-13 per cent, of the total 

 solid present, and this, after treatment with digitonin, separated into 

 1-43 per cent, of cholesterol and 1-7 per cent, of a body which Faure- 

 Fremiet identified with the "unsaponifiable X" of Kumagawa, prob- 

 ably spinacene or squalene. Thus the dry weight composition of the 

 ether-alcohol extract at zero hour of development was : 



%dry 

 weight egg 

 Phosphatides ... ... ... ... 5-98 



Neutral fatty acids ... ... ... 14-82 



Cholesterol 1-43 



" Unsaponifiable X " ... ... ... 1-70 



23-93 



Unfortunately Faure-Fremiet & Dragoiu seem to have forgotten to 

 make any estimations of cholesterol and other unsaponifiable sub- 

 stances at later stages of development. Parnas & Krasinska made 

 determinations of cholesterol only as follows : 



Cholesterol 



% of the total Milligram per 



fatty acids individual 



Egg 13-6 0-056 



Hatched larva ... ... 167 0-056 



Thus there was apparently no change in the total cholesterol, 

 although in per cent, of the fatty acids it rose, owing to their utilisa- 



