A 



FIG. 52. Hydra. 



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

 filament and the cnidocil (cnc). 



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.) 



