BEHAVIOR OF THE GAMETES 233 



function in the reactions involved in fertilization. The older conception of 

 Waldeyer that the acrosome was a perforating device which enabled the sperm 

 to pass through the egg membranes and thus to enter the egg is untenable in 

 the light of later observation. Many years ago Bowen ('24) though admitting 

 a minor mechanical role for the acrosome, emphasized that the acrosome 

 essentially is a secretory product whose principal function is to initiate the 

 physicochemical reactions of fertilization. It should be recalled in this con- 

 nection that Hibbard ('28) and also Parat ('33, a and b) have attributed to 

 the acrosome of the anuran, Discoglossus, the ability of carrying or producing 

 an enzyme which enables it to reach the egg's surface through the jelly sur- 

 rounding the egg. Parat further suggested that the acrosome in this species 

 contains a "proteolytic enzyme" which, when introduced into the egg, results 

 in development. 



The concept of a proteolytic enzyme associated with the acrosome of Dis- 

 coglossus is interesting in the light of the suggestion by Leuchtenberger and 

 Schrader ('50) that the mucolytic enzyme, hyaluronidase, in the bull sperm 

 may be associated with the acrosome. Both of the above suggestions need 

 more work before it can be stated with certainty that the acrosome is con- 

 nected with either of these enzymes in the above species. However, these sug- 

 gestions do serve to emphasize the possibility that the acrosome may be an 

 enzyme-producing or enzyme-carrying device which enables the sperm to 

 make its way through the egg's surroundings to the egg surface, and also, that 

 it may play a part in egg activation. 



5) Summary of the Activities of the Egg and Sperm in Bringing About 

 the Primary or Initial Stage of the Fertilization Process, Namely, that of Egg 

 and Sperm Contact. 



a) The secretion of fertilizin by the egg: 



( 1 ) activates the sperm to increased motility, and 



(2) through chemotaxis, entices the sperm to move in the direction of the 

 egg- 



b) In moving toward the egg the lytic substances elaborated by the sperm 

 enable it to "plow" through the gelatinous envelopes and cellular barriers to 

 the surface of the egg. This movement undoubtedly is aided by movement of 

 the flagellum in some species, but not in all (see Discoglossus). The acrosome 

 of the sperm may function at this time either as an instrument carrying lytic 

 substances or as one which actually manufactures these substances. The pres- 

 ence of large numbers of sperm near the egg may aid sperm penetration to 

 the egg's surface by contributing lytic substances to the environment around 

 the egg which aid in the removal of membranes and other barriers surrounding 

 the egg. 



c) The antifertilizin of the sperm may then unite with the fertilizin of the 



