Protein Constituents of Spermatozoa 95 



Swyer (1947«, b) to be quite sufficient for hyaluronidase to pass 

 completely into solution. In an isotonic medium spermatozoa also 

 tend to liberate hyaluronidase but when the concentration of the 

 enzyme outside the cell reaches a certain level it seems to prevent 

 further leakage. Indeed, under certain experimental conditions, 

 spermatozoa depleted of hyaluronidase have been found to be 

 capable of reabsorbing the enzyme from a hyaluronidase-rich 

 medium (Emmens and Swyer, 1948; Swyer, 1951). 



The physiological role of sperm hyaluronidase is far from clear 

 at present. It may be related in some as yet unknown manner, 

 to the spsrmiogenic function of the testis, but there is also soms 

 indication that in certain mammals at any rate, hyaluronidase acts 

 by facilitating the contact between the male and female gametes 

 through a direct liquefying action on the viscous gel which cements 

 the follicle cells around freshly ovulated eggs. 



Much thought has been devoted in the past to the problem of the 

 participation of 'lytic' agents in the process of ovum fertilization, 

 and to what at one time used to be called the 'ovulase' activity of 

 spermatozoa. However, the early investigators of this problem were 

 in the main concerned with lower animals. In many molluscs, 

 fishes and amphibia, the unfertilized egg is normally surrounded by 

 a viscous 'jelly coat' and a membrane, which the spermatozoon 

 must penetrate before fertiUzation can be effected. To explain this 

 process, several investigators postulated the presence of lytic agents 

 in the spermatozoa, capable of mediating the fusion of the gametes, 

 but there has been little evidence that these agents are in fact enzymic 

 in nature, until Tyler's (1939, 1942) discovery of the 'egg-membrane 

 lysin', a heat-labile protein-enzyme which he extracted from the 

 sperm of two molluscs, the key-hole limpet Megathura cremilata 

 and the abalone Haliotis cracherodii. With sperm extracts of these 

 species, the disappearance of the egg membrane could be demon- 

 strated within about 3 min., if the gelatinous coat of the egg 

 was present, and in less than 30 sec, if the coat has been first 

 removed. 



The occurrence of similar lytic enzymes in the sperm of other 

 lower animals is still under discussion (cf. Tyler, 1948; Berg, 1950; 

 Runnstrom, 1951). Several lytic agents have been described in sea- 

 urchin spermatozoa. One of them is the previously mentioned 



