METABOLIC AND OTHER CHANGES AT FERTILIZATION 89 



sulphate extracts show a decrease in solubiHty of one component 

 immediately after f. P. lividus (Monroy, 1950). 



In a later paper by Monroy & Monroy-Oddo (1951, p. 246), it is said 

 that 'the electrophoretic patterns of the water extracts of unfertilized 

 and fertilized eggs of Arhacia lixula are essentially identical. . .' 



(16.2) No change in solubility of proteins extractable with 

 M-KCl after f. A. piinctidata (Monroy & Monroy-Oddo, 195 1). 



The eggs were treated with trypsin before fertilization to prevent 

 the formation of the fertilization membrane, it being thought that the 

 salts in the perivitelline fluid might cause ambiguous results. Al- 

 though the authors found a change in the M-KCl-soluble fraction 

 after fertihzation of Arhacia lixula eggs, they say that further experi- 

 ments are needed to decide whether the postulated coagulation 'is an 

 actual occurrence under natural conditions.' (p. 253). Similar doubts 

 about Mirsky's results have been expressed by Lindvall & Carsjo 

 (1951), using the eggs oi Echinus esculentus. 



(17) Production of acetyl choline or acetyl choline-like substance 

 at f. P. depressus (Numanoi, 19536). 



In the same paper the author states that spermatozoa of Pseudo- 

 centrotus depressus (A. Agassiz) and Clypeaster japonicus contain cholin- 

 esterase, as do mammalian spermatozoa (Sekine, 1951). Scheer (1945) 

 showed that acetyl choline and physostigmine, at concentrations of 

 i/io^, inhibited the activation of eggs of Urechis caupo and Strongy- 

 locentrotus purpuratus. In a later paper, Scheer & Scheer (1947) found 

 that the inhibitory action of acetyl choline was extremely complicated, 

 at any rate in Urechis eggs, inhibition being most marked when activa- 

 tion was affected by subjecting unfertilized eggs to potassium- and 

 magnesium-free, but calcium-enriched, sea water. In view of these 

 results, it would be unwise to attach too much importance to Nu- 

 manoi's results until they have been confirmed. Heilbrunn (1952, pp. 

 635-642) makes some cogent remarks about the necessity for caution 

 in interpreting experiments designed to demonstrate the existence of 

 acetyl choline in tissues. 



(18) Release of sulphate due to splitting of heparin-like poly- 

 saccharide sulphate at egg surface (jelly?) by sperm sulphatase. 

 H. pulcherrimiis (Numanoi, 1953a). 



(19) No change in hexokinase activity at f. A. punctulata (Krahl 

 et al., 19546). 



(20) No change in urease activity at f. S. purpuratus (Brook- 

 bank & Whiteley, 1954). 



