NEMATOCYSTS 



301 



FIG. 77. Hydra. 



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

 and the cnidocil (cnc). (x 400.) 



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). (From Parker's Biology: after Schneider.) 







which is turned in as a hollow pouch : the free end of 

 the latter is continued into a hollow, coiled filament, 

 ,nd from its inner surface project the barbs. The 



