SPERM-EGG INTERACTING SUBSTANCES, I 37 



effect on egg jelly, apart from forming a precipitation membrane 

 at its surface. After the precipitation membrane has formed, the 

 jelly contracts to such an extent that its surface becomes contiguous 

 with that of the egg proper and is, consequently, invisible. On the 

 basis of this phenomenon Tyler & O'Melveny (1941) believe that 

 the substance claimed to have hyaluronidase activity is in reality 

 sperm-antifertilizin and that sea-urchin spermatozoa do not contain 

 a separate depolymerase. The experiments of Krauss (1950) con- 

 firm that claims for the existence of a hyaluronidase-like enzyme in 

 sea-urchin spermatozoa should not be accepted. Vasseur (1951) 

 also reported that sea-urchin spermatozoa contained an enzyme 

 which splits egg jelly. But in this case again, the claim has been 

 refuted, by Monroy & Tosi (1952), who also cast doubt on the 

 earlier work on this subject, mentioned above, by Monroy & 

 Ruffo (1947). Ishida (1954) has recently claimed that sea-urchin 

 spermatozoa release a jelly-dissolving substance at the moment of 

 fertilization. The situation is sufficiently confused to merit 

 systematic re-examination. 



A protein which is, however, distinct from sperm-antifertilizin 

 can be extracted from limpet spermatozoa. The unfertilized egg 

 of Megathura crenulata is surrounded by a tough membrane which 

 is not dissolved by concentrated acid applied over a period of hours. 

 Yet suspensions of homologous spermatozoa dissolve the mem- 

 brane in a matter of minutes, Plate IV, while extracts obtained by 

 freezing sperm suspensions to —80° C and thawing achieve the same 

 result. These eggs also have jelly round them, through which the 

 spermatozoa must get to reach the membrane (Tyler, 1939). Berg 

 (1950a) has made similar observations on the eggs of Mytiliis edulis 

 and Monroy (1948) on those of Pomatoceros triqiieter. One cannot 

 help feeling that, although enzymes of this type may dissolve mem- 

 branes external to the egg surface, they must also have a function in 

 softening up the plasma membrane, so that the spermatozoon is 

 able to enter the egg and get on with the business of syngamy. 



Inhibitors of sperm movement derived from spermatozoa or semen. 

 A substance which inhibits sperm movement and might, therefore, 

 be said to antagonize fertilizin, can be extracted from sea-urchin 

 spermatozoa. This substance, Androgamone I (A.I), can be ex- 

 tracted from these spermatozoa by a variety of treatments such as 

 centrifugation (Southwick, 1939; Vasseur & Hagstrom, 1946; 

 Rothschild, 1948), warm water (Frank, 1939), or extraction with 



