58 EGG AND SPERM SUBSTANCES 



These lytic agents not only permit penetration of the egg mem- 

 branes by the sperm, but they may also contribute a specificity 

 factor in fertilization. Thus the lysins and eggs of Haliotus and 

 Megathura do not cross react (Tyler, 1939b). Mtjtilus calif ornia- 

 nus extracts dissolved both the egg membrane and intercellular 

 cement of M. edtdis but cross reaction did not occur in the re- 

 verse combination. Extracts from neither species acted on eggs of 

 more distantly related forms. Likewise, sperm extracts from such 

 foreign species did not act on Mytilus eggs (Berg, 1950). In 

 other molluscs the lytic action is also largely specific (von 

 Medem, 1942, 1945 ) . Krauss ( 1950b ) , however, reported an in- 

 teresting heterologous reaction, namely lysis of the Megathura 

 membrane by a heat-labile agent from sea urchin sperm. 



Although the cases described above are well established, the 

 situation in the sea urchin has been disputed. In sea urchins a 

 special lytic agent may not be required for penetration of the 

 sperm through the jelly. In most species the jelly is not highly 

 viscous and is readily soluble in weak acid. The COi> produced 

 by the penetrating sperm may be sufficient to dissolve a path to 

 the egg surface. Claims that the sea urchin egg jelly is dissolved 

 by depolymerases from the sperm have not been substantiated 

 (Krauss, 1950c; Monroy and Tosi, 1952; Monroy et al, 1954). 



Aside from action on the egg jelly, extracts have been prepared 

 from sperm which act upon the egg surface. Runnstrom, Lindvall, 

 and Tiselius (1944) found that the methanol extracts of sea ur- 

 chin sperm caused eggs to shrink without wrinkling in hyper- 

 tonic sea water. This and other tests led to the view that the 

 methanol extracts partially lysed or liquefied the egg surface. 

 This egg surface lysin (androgamone III) was found to be heat 

 stable and dialyzable. These and other properties, including du- 

 plication of the action by detergents, led to the view that the agent 

 is a low-molecular-weight, surface-active agent of fatty acid na- 

 ture (Runnstrom, Tiselius, and Lindvall, 1945; Runnstrom and 

 Lindvall, 1946; Runnstrom, 1947, 1949a). Sperm supernatants 

 have the same action as methanol extracts. Therefore the agent 

 may be available and function under physiological conditions. 



