A. L. COLWIN AND L. H. COLWIN 



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Fig. 21. Reacted spermatozoa of Asterina pectinifera showing acrosome 

 filaments after suspension in egg water. (From Dan, Biol. Bull., 1954.) a, 

 small cluster of agglutinated spermatozoa; b, single reacted spermatozoon. 



than in the unreacted spermatozoon (Fig. 22B), and the base of 

 the flagelknn and the acrosome filament lay nearly at right angles 

 to each other. 



Molluscs. In some of the species of bivalve mollusc studied 

 by Dan and Wada ( 1955 ) , the acrosome reaction was elicited by 

 the species egg water and/or by "contact" with glass surfaces. 

 However, in all the species studied, the spermatozoa produced 

 acrosome filaments when placed in the presence of unfertilized 



Fig. 22. Head ends of spermatozoa of starfish. (After Dan, Biol. Bull., 

 1954.) A, reacted, showing the acrosome filament; B, unreacted. 



