56 EGG AND SPERM SUBSTANCES 



These experiments indicate that antifertihzin at the sperm sur- 

 face is an aid to fertiUzation and render hkely the possibihty 

 that the agent is essential for fertiHzation. 



Sperm Paralyzing Agents 



Several workers (e.g., Southwick, 1939; Hartmann, Schartau, 

 and Wallenfels, 1940; Vasseur and Hagstrom, 1946; Runnstrom, 

 Lindvall, and Tiselius, 1944; Rothschild, 1948) have found that 

 seminal fluid or sperm extracts, mainly from sea urchins, inhibit 

 sperm motility. Hartmann et al. ( 1940 ) attributed the action to 

 an agent, androgamone I. Other investigators working on other 

 forms have failed to find comparable action. In certain cases the 

 paralyzing effect is evidently due to O2 lack. Only in the case of 

 the salmon is it probable that the agent is normally functional 

 (Rothschild, 1951b). Tyler (1948a), Runnstrom (1949a), and 

 Rothschild (1951b) have reviewed these studies in detail. 



Egg Membrane and Surface Ltjsins from Sperm 



In many forms the egg is surrounded by extraneous jelly lay- 

 ers, membranes, cell layers, or a combination of these. Such mem- 

 branes are mechanical barriers to the fertilizing sperm. These and 

 the egg surface itself must be penetrated for the sperm to enter 

 the egg cytoplasm. Such penetration is evidently achieved, in 

 some forms at least, through the action of egg membrane lysins 

 carried by the sperm. Indeed, of the various "sex substances" that 

 have been obtained from gametes only these membrane lysins 

 have well-understood action in fertilization. The most thoroughly 

 studied of these agents are the membrane lysins from the sperm 

 of molluscs and hyaluronidase in mammals. Since the role of hya- 

 luronidase in mammalian fertilization is discussed elsewhere 

 (Chang, this volume), it will be omitted here. Among molluscs 

 the limpet, Megathura crenulata and the mussel, Mytilus edulis, 

 have been examined in most detail. 



Freshly shed Megathura eggs are surrounded by a jelly layer 

 and a rather thick membrane. The latter is closely applied to the 

 egg but gradually rises as the egg stands in sea water. Upon 

 heavy insemination, the membrane disappears. The responsible 



