c?ib 



FIG. 52. Hydra. 



A, A nematocyst contained in its cnidoblast (cnb), showing the coiled 

 filament and the cnidocil (cue]. 



B, The same after extrusion of the thread, showing the larger and 

 smaller barbs at the base of the thread, nu, the nucleus of the 

 cnidoblast. 



c, A cnidoblast, with its contained nematocyst, connected with one 

 of the processes of a nerve-cell (nv. c), 

 (After Schneider.) 



