CLUSTER FORMATION OF SPERMATOZOA 139 



2. The cluster formation resembles the phenomena of surface 

 tension in various respects, e.g., inasmuch as the clusters are 

 spherical or tend to assume a spherical shape, and inasmuch as the 

 fusion of two clusters results in the formation of a larger spherical 

 cluster. When sperm is put into ordinary sea water or the super- 

 natant water of foreign eggs these apparent surface tension 

 phenomena are not observed. In real sperm agglutination neither 

 cluster formation nor the above-mentioned surface tension, 

 phenomena are noticeable. 



3. It was found that the cluster formation is a direct function 

 of the motility of the spermatozoa. As soon as the spermatozoa, 

 are immobilized by NaCN or by high temperature or by KCl the- 

 cluster formation ceases; as soon as the motility of the sperma- 

 tozoa returns the cluster formation occurs again when the ^erm 

 is put into the supernatant sea water of eggs of the same species. 

 The real agglutination of Sperm occurs just as well when the sperm 

 is immobilized as when it is motile. The cluster formation is 

 therefore not a form of agglutination. 



4. The clusters last only a few minutes, like Lillie's sperm^ 

 ' agglutinations. ' The writer has found that in a neutral solution 

 they last much longer than in an alkaline solution and that they 

 scatter the more rapidly the more the alkalinity of the sea water 

 is raised by the addition of NaOH. 



5. The writer offers tentatively a working hypothesis whiclt 

 assumes that the phenomenon of cluster formation is essentially 

 or partly due to a negative chemotropism of the spermatozoa to> 

 the egg-sea water. 



6. It is shown that eggs which have been treated with acidl 

 sea water lose permanently their power of producing a sub- 

 stance which causes the cluster formation of the spermatozoa of 

 their own species; while the acid sea water in which the eggs were? 

 treated when filtered and neutralized with NaOH induces a very- 

 powerful cluster formation. If it is true that the acid dissolve^-, 

 the chorion (the jelly-like substance surrounding the egg) this-, 

 experiment would prove that the substance which causes the; 

 cluster formation is not formed in the egg but in the chorion. IfT 

 this substance is identical with the substance which LilLiecalls^ 



