PHYSIOLOGY OF THE SPERMATOZOON 95 



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

 Loeb (19 1 5) 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). 



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. 



