SPERM AGGLUTINATION AND FERTILIZATION. I9 



I. "Cluster-formation" versus Agglutination. 



The phenomena exhibited by sperm suspensions of Arbacia 

 with which we have to deal are of four distinct types, which it is 

 essential to distinguish sharply: (i) activation; (2) aggregation; 

 (3) agglutination, (4) mass-coagulation.^ (i) That the activity 

 of spermatozoa is affected by substances in the sea-water requires 

 no argument. The subject is discussed in study V (Lill'e, 1913a, 

 pp. 519-532). (2) Aggregation of spermatozoa may be brought 

 about by tropistic reactions. In my paper on the "Behavior 

 of Spermatozoa," I devoted a great deal of attention to such 

 aggregation phenomena and the distinction from phenomena of 

 agglutination (1913, pp. 532-548 and pp. 551-552). Among 

 other things I pointed out that aggregation as a tropistic phe- 

 nomenon implies a gradient,^ and that the spermatozoa never 

 adhere, however crowded they may be; there is no observable 

 physical change of the spermatozoa and the slightest agitation 

 suffices to disperse them again. Such tropistic phenomena may 

 be exhibited in response to COo and other acids (Nereis), or 

 certain constituents of egg secretions, to mention only chemotaxis. 



(3) Agglutination of spermatozoa on the other hand requires 

 no gradient, and the spermatozoa adhere physically to such an 

 extent that the agglutinated masses may be preserved intact in 

 killing fluids; its degree is a function of the concentration of the 

 agglutinating medium, and is also different in different species. 

 Agglutination is non-toxic, not limiting the life of the sper- 

 matozoa; it is reversible, its duration depending on the concen- 

 tration of the agglutinating medium ; it cannot be repeated if the 

 reaction is complete, at least within the time limits of my ex- 

 periments, even though the spermatozoa remain motile;^ finally 

 motility of the spermatozoa is a prerequisite to a decided reac- 



1 The reaction here referred to is a lethal phenomenon. It possibly involves 

 cytolysis with subsequent adhesion of the spermatozoa. 



2 It is important to notice that the spermatozoa of suspensions may produce 

 gradients through their own activities. Thus I pointed out that autogenous aggre- 

 gation reactions in sperm suspensions of Nereis arise from the positive chemotaxis 

 of the spermatozoa to their excreted CO2, giving rise to very striking phenomena 

 (Lillie, 1913a, pp. 519-521 and pp. 538-540), It is conceivable that such a tro- 

 pistic phenomena is involved as a part factor in the agglutination phenomena 

 under discussion. 



3 Glaser (1914) also comes to this conclusion. 



