THE METABOLISM OF EGGS, II 75 



in free (i.e., extractable with ether-chloroform mixtures) 'chole- 

 sterol'; but in his 1945 paper, Ohman says that his previous ob- 

 servation was unreliable and that there is no change in the 'chole- 

 sterol' content of the eggs at fertilization. Monroy & Ruffo (1945), 

 on the other hand, reported an increase in free 'cholesterol' at 

 fertilization in sea-urchin eggs. The word cholesterol is placed in 

 quotation marks above, because there is some doubt whether the 

 substance whose concentration was measured by Ohman, Monroy 

 & Ruffo, and earlier workers such as Mathews (1913) and Page 

 (1923), was actually cholesterol or a related steroid. 



CHg-O-PO-O-CHa'CHg-NHa 



OH 

 Phosphatidylaminoethanol, a simple cephalin 

 R-COOH and R'-COOH are fatty acids 



Nitrogen metaholism. Important work in this field was done by 

 Orstrom in 1941. He reported that, at fertilization or parthogenetic 

 activation, there was a transient production of ammonia, lasting 

 for about ten minutes, and that simultaneously, a substance which 

 liberated ammonia upon heating and which Brachet (1950) thinks 

 may be a glutaminylpolypeptide, disappears. Orstrom believed that 

 the ammonia production resulted from the deamination of nucleic 

 acid. However, this view was based on the deamination of muscle 

 adenosine and adenylic acid by unfertilized egg homogenates, a re- 

 action which he said was accelerated by the addition of cytolysed 

 spermatozoa. Orstrom also claimed that fertilized eggs differed 

 from unfertilized ones in being able to synthesize glutamine from 

 glutamic acid and ammonia, though both unfertilized and fertilized 

 eggs can effect the reverse reaction, the hydrolysis of glutamine 

 to glutamic acid and ammonia. xA.part from transiently producing 



