CLUSTER FORMATION OF SPERMATOZOA 131 



THE CONDITIONS WHICH DETERMINE THE SCATTERING OF 



THE CLUSTER 



The clusters (just like Lillie's 'agglutinations') have only a 

 short duration of from two to ten minutes, as the circumstances 

 may be. It was of interest to find out some of the conditions 

 which determine their duration. It was found that the stability 

 of the clusters depends upon the alkalinity of the sea water. In a 

 neutral solution the big clusters may last a considerable time, half 

 an hour or more, while in sea water to which a sufficient amount 

 of alkali has been added the clusters may scatter in a minute. 

 The reader must remember that if we add HCl or NaOH to sea 

 water part of the added acid or base will be neutralized by the 

 carbonates and phosphates of the sea water. 



To 5 cc. supernatant sea water from purpuratus eggs were added 

 0, 1, 2, 3, 4 drops of t^ NaOH and 3 drops of a dense suspension of 

 purpuratus sperm were added to each. In all dishes a large cluster 

 was formed. In the dishes with 4 and 3 drops of NaOH the clus- 

 ters were dissolved almost instantly after formation, in the dish 

 with 2 drops the resolution occurred more slowly and it lasted 

 longest — about eight minutes — in the sea water to which no 

 alkali was added. 



In a second experiment to 5 cc. of the same egg-sea water 0, 1, 

 2, 3 and 4 drops ^ HCl were added, and then purpuratus sperm 

 introduced. In 5 cc. egg-sea water + 4 drops of HCl no cluster 

 formation occurred, probably because the motility of the sperm 

 was too rapidly annihilated. In the dish with 3 drops HCl only 

 a trace of cluster formation was noticeable ; with 2 drops a moder- 

 ate cluster formation occurred and only in the two dishes with 

 and 1 drop of HCl was the cluster formation very powerful, since 

 here the motility of the spermatozoa was not impaired. In the 

 egg-sea water without acid the clusters disappeared much more 

 quickly than in the sea water with 1 or 2 drops of acid. 



Experiments in which neutral artificial sea water was substi- 

 tuted for normal sea water showed that at the point of neutrality 

 the cluster formation is most durable. The big clusters continued 

 to exist as long as half an hour, while in alkaline solutions they 

 disappeared very rapidly. In acid solutions no cluster formation 



