SPERM-EGG INTERACTING SUBSTANCES, I 



35 



while sperm-antifertilizin does not cause homologous sperm 

 agglutination. This complicated question, which has been dis- 

 cussed at great length by Runnstrom (1949), is not yet resolved, 

 and further work is needed to clarify the chemical properties of 

 sperm-antifertilizin, which is certainly of biological importance, 

 both in eggs and spermatozoa. If a decision had to be taken now, 

 it would probably be in favour of sperm-antifertilizin being an 

 acidic protein, and not an unspecific basic protein. 



F. R. Lillie believed that the function of egg-antifertilizin was to 

 neutralise fertilizin which would otherwise diffuse out of the egg 



TABLE 5 

 Electrophoresis of purified solutions of sperm-antifertilizin ofE. 

 cordatum {Runnstrom et al., 1942) and L. pictus {Tyler, 1949) 



at a time when there would be no point in it doing so. This idea 

 loses much of its value now that we believe fertilizin is in general 

 derived from egg jelly and not from eggs; and it is therefore not 

 surprising that Monroy & Runnstrom (1950) were able to extract 

 antifertilizin from fertilized eggs. Runnstrom (1952) believes that 

 egg-antifertilizin is a chromoprotein which reacts with the vitelline 

 membrane on the unfertilized egg at the moment of fertilization, 

 hardening and converting it into the fertilization membrane. If 

 this view is correct, egg-antifertilizin might be located in the cortical 

 granules of the egg, as these are known to have a hardening or 

 tanning effect on the fertilization membrane (see pp. 9-10). 



Sperm lysins. Spermatozoa contain compounds which can break 

 down or dissolve the membranes and jelly which so often surround 

 unfertilized eggs, and a similar substance may have a lytic effect 

 on the plasma membrane itself. Some such action seems to be 

 required at fertilization, as the spermatozoon has got to get through 



