MORPHOLOGY OF FERTILIZATION: 



ACROSOME FILAMENT FORMATION 

 AND SPERM ENTRY 



ARTHUR L. COLWIN and LAURA HUNTER COLWIN: 



QUEENS COLLEGE, FLUSHING, NEW YORK 



Some Aspects of Sperm Morphology 



The older studies of spermatozoa by Retzius ( 1904, 1905, 

 1910) and others revealed that there are wide morphological 

 variations among the spermatozoa of different species. Contem- 

 porary investigations of sperm morphology are in part directed 

 toward a detailed analysis of structure by means of electron mi- 

 croscopy as in the studies of Dan ( 1952, 1954 ) and of Burgos 

 and Fawcett (1955, 1956), and in part toward a cytochemical 

 characterization as in the studies of Clermont, Glegg, and Le- 

 blond (1955). Phase contrast microscopy is facilitating observa- 

 tion of the living spemiatozoon. The present paper will deal 

 chiefly with the acrosomal region, especially with reference to 

 certain changes occurring in this and other regions at fertilization 

 or under other conditions some of which may obtain at fertiliza- 

 tion. 



The acrosomal region can be seen as a structural entity in sper- 

 matozoa of many species. Often it projects beyond the nucleus 

 in an apical or near apical position. Some investigators have used 

 the terms "acrosome" and "perforatorium" synonymously to in- 

 dicate the entire acrosomal region. Others have used these same 

 terais to distinguish two specific structures within the acrosomal 

 region. It is to be expected that the confusing terminology which 

 exists in the literature concerning the acrosomal region will soon 

 be clarified (vide Burgos and Fawcett, 1955, 1956). 



Dan and Wada (1955) have described three differentiated 



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