XEMATOCYSTS 



301 



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FIG. 77. Hydra. 



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

 and the cnid'ocil (cnc). (< 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 (mi. 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, 

 and from its inner surface project the barbs. The 



