PHYSIOLOGY OF THE SPERMATOZOON 95 



spite of Schiicking's (1903) statement to the contrary. 

 Loeb (1915) has shown that spermatozoa will not 

 fertilize in the presence of an immobilizing concentra- 

 tion of NaCN, no matter how concentrated the sperm, 

 "while the same sperm when it revives from the effect 



FIG. 13. Photograph of the aggregation of a sperm suspension of 

 Nereis, taken 90 seconds after mixing the. suspension (natural size). 



4 



of NaCN fertilizes the same eggs at once." The 

 experiment is not conclusive proof of the necessity of 

 motility for fertilization, because the block in the ferti- 

 lization reaction might conceivably be due to some other 

 effect of the NaCN. The experiment, however, ren- 

 ders it very probable that motility of the sperm is 

 necessary. 



