242 



GREGOR T. POPA. 



to another, and in the same spermatozoon during the obser- 

 vation l until at the end of the reaction almost all spermatozoa 

 show the middle piece as a compact mass, red-stained. 



FIG. 5. Spermatozoon of Nereis to show sensillae amoeboideae. 



When the slowly moving spermatozoon shows its tip, one can 

 see that there is really a minute opening. The tip of the 

 spermatozoon is extremely sticky and adheres to everything 



1 The instability of this region was very clearly observed by Retzius and 

 Ballowitz, but they believe that it occurs because of the technique. However, 

 without staining, under conditions approximately normal, the same variations of 

 shape can be noticed. Gustav Retzius, "Die Spermien von Aurelia aurila L.," 

 Bio!. Unters., N. F., XIV., 1909, S. 67. Gustav Retzius, "Die Spermien der 

 Nereiden," Biol. Unters., N. F., XIV., 1909, S. 69. E. Ballowitz, "Uber die 

 Kornige Zusammensetzung des Verbindungsstiickes der Samenkorper der Knochen- 

 fische," Arch.j. Zellforschung, 14 Bd., 1917, p. 355. 



