128 JACQUES LOEB 



reaction of the spermatozoa. If this were the case, we should 

 expect that anything that diminished the motihty of the sperma- 

 tozoa would lessen the tendency of the sperm to form clusters, 

 and if the sperm were paralyzed completely the cluster formation 

 would also cease completely. 



It was easy to show that both assumptions were correct. To 

 3 cc. of a dense sperm suspension in ordinary sea water were 

 added 1 or 2 drops of a 0.1 per cent solution of NaCN, and the 

 whole thoroughly mixed. In one or two minutes the sperm lost 

 its motility and did not regain it when put into sea water. When 

 one or several drops of this immobilized sperm were added to the 

 egg-sea water and when after one minute the dish was gently 

 agitated, the sperm behaved exactly as if it had been put into 

 normal sea water. Not a trace of cluster formation was notice- 

 able; a slight agitation sufficed to bring about a perfectly homo- 

 geneous mixture of the sperm in sea water. After two hours the 

 sperm became motile again when put into sea water. When such 

 sperm, after the recovery of its motility, was put into egg-sea 

 water a very powerful cluster formation occurred again. 



These experiments were varied and always proved definitely 

 that the whole phenomenon of cluster formation existed only 

 when the sperm was motile. 



There are other ways of paralyzing the spermatozoa. When 

 the sperm of purpuratus is heated to a temperature of 35°C. or 

 even 36°C. the sperm remains motile and the phenomenon of 

 cluster formation is striking when a drop of such sperm is added 

 to 3 cc. of egg-sea water and the mass is agitated. As soon as 

 sperm is brought to a temperature of 37.6° or above and rapidly 

 cooled, the motility is gone and no cluster formation takes place. 



The same experiment was made with the sperm of Strongylo- 

 centrotus franciscanus and the supernatant sea water of eggs of 

 the same species. When the sperm is heated to a temperature of 

 36.2° its motility continues and the cluster formation is not dimin- 

 ished. When the sperm is heated for one minute to a temperature 

 of 37° the motility of the sperm is only diminished and only small 

 clusters are formed. If the sperm is heated to 38° the motility 

 of the sperm disappears and the phenomenon of cluster formation 

 is impossible. 



