n6 PROBLEMS OF FERTILIZATION 



apparently in nowise injured, in which respect iso- 

 agglutination differs from the frequent toxic effects of 

 foreign egg secretions, which may cause permanent 

 adhesion of spermatozoa in masses. 



The phenomenon of agglutination of sperm suspen- 

 sions by egg water probably does not occur in all 

 animals. Thus I have been unable to observe it in the 

 starfish, though Glaser (1914) reports its occurrence in 

 this form. Absence of sperm agglutination, however, 

 is not evidence for absence of a comparable secretion 

 of such ova, for the adhesion of the spermatozoa is 

 evidently a result of a surface physical change of sper- 

 matozoa which may be less in some forms than in 

 others. Thus while in some species the spermatozoa 

 are efficient indicators for the substance, they need not 

 be so in all. This does not, however, in the least de- 

 tract from the usefulness of the indicator when present. 



Loeb points out that sperm suspensions paralyzed 

 by KCN do not agglutinate in specific egg water; thus 

 motility of the spermatozoon is necessary for the reac- 

 tion; this is readily understood on the principle that 

 energy of impact is necessary for adhesion. Loeb also 

 states that the duration of the reaction is dependent to 

 some extent on the alkalinity of the medium. "The 

 more alkaline the latter the more rapidly the cluster 

 scatters. The presence of a salt with a bivalent metal, 

 especially Ca, seems necessary for the cluster for- 

 mation." 



The agglutination reaction may be studied in a 

 quantitative way. The reaction is reversible, as we have 

 seen; with high concentration of the agglutinating 

 substance it may be several minutes before the aggluti- 



