136 



MORPHOLOGY OF FERTILIZATION 



7 8 9 10 I? 12 13 



Figs. 1-13. Spermatozoa of bivalve mollusc species to show morphologi- 

 cal changes resulting from the acrosome reaction. (From Dan and Wada, 

 Biol. Bull., 1955.) 1, Mijtiliis edulis spermatozoon in sea water. 2, Mytiltis 

 spermatozoon after egg water treatment. 3, Mijtilus spermatozoon showing 

 partial reaction. 4, Petricola japonica spermatozoon before reaction. 5, Re- 

 acted Petricola spermatozoon in vicinity of egg. 6, Partially reacted Petricola 

 spermatozoon. 7, Mactra sulcataria spermatozoon. 8, M. sulcataria super- 

 numerary spermatozoon. 9, Mactra veneriformis spermatozoon. 10, M. 

 veneriformis spermatozoon after egg water treatment. 11, Spondylus cruen- 

 tus spermatozoon. 12, Spondylus spermatozoon reacted in egg water (side 

 view). 13, Reacted Spondylus spermatozoon as found affixed to under side 

 of coverglass. 



