CHARLES B. MKTZ 



23 



The acrosome reaction has been reported to occur under a variety of con- 

 ditions. These include the following: a) contact with glass, b) treatment with 

 alkaline sea water, c) treatment with egg water, d) treatment with egg water 

 plus an adjuvant, e) exposure to unfertilized eggs. Examination of the available 

 data, (16, 18-20, 22-25, 71) shows that the acrosome reaction is a rather wide- 

 spread phenomenon (24 species in 4 phyla). In 2^5 of the 24 species examined, 



Fig. 4. Electron photomicro- 

 graphs of Astereis forbesii sperm 

 fixed in 59f formalin, diai\zed 

 against distilled water, air dried 

 to the collodion membrane and 

 shadow cast with chromium. 



a, Control sperm from sea water 

 suspension. Sperm nucleus and 

 middle piece are compact and 

 closely applied to each other; no 

 trace of acrosome filament, b and c, 

 Spermatozoa with acrosome fila- 

 ments from a suspension treated 

 with 0.0 rM Versene and egg water. 

 The long acrosome filament pro 

 jects upward from the nucleus in b, 

 and to the left in c. In both b and c 

 the entire sperm head region ap- 

 pears to have undergone partial 

 Ijreakdown with 'loosening' and 

 displacement of the midpiece. 



an acrosome reaction resulted from egg water treatment (and adjuvant in 

 starfish) or contact with eggs. Sperm of 4 species produced filaments in alkaline 

 sea water and, or upon contact with glass. In the absence of negative reports 

 m these data, it must be concluded that only a very few species have been 

 examined exhaustively for filament formation under diverse conditions. 



In a study of 5 species (3 molluscs, 2 echinoids) Rothschild and Tyler (94) 



