522 



FRANK n. LILLIE 



Fig. 3 Another suspension photographed 3 minutes after mixing; description in 

 text. 



only to the extent that they appear to be significant for the 

 phenomena of aggregation and agglutination, which are the main 

 problems for our consideration. 



2. Individual movements of the sperm 



To explain the various reactions of the sperm it is necessary to 

 consider first some of the more obvious features of locomotion of 

 individual spermatozoa. In their free movements through the 

 water they describe, as is well known, spiral paths. In Nereis the 

 successive turns of the spiral are rather close set. As soon as a 

 spermatozoon comes in contact with a surface, the movements of 

 translation cease, and circus movements begin. The sperm moves 

 round and round in a circle of varying diameter in contact with 

 the surface. In the case of a preparation beneath a cover slip 

 on a slide, those in contact with the slide rotate anticlockwise, 

 those in contact with the cover-slip clockwise. The direction of 

 rotation is always the same. It is associated no doubt with struc- 

 tural asymmetry which I described briefly in Study III (Lillie 



