The Physiology of Nematocysts 377 



the reason why the nematocysts explode under the conditions 

 named, is because the nematocyte is stimulated to do something 

 which brings about discharge. The correctness of this inference 

 can be established, if without destruction, the nematocyte can be 

 eliminated from possible participation in the chain of events. 

 This can be done by narcotization. The most effective agent to 

 use, if used with moderation and care, is chloretone. If the 

 tentacles and acontia of Metridium are narcotized with chlore- 

 tone, saturated sodium chlorid, 95 per cent alcohol, and chloro- 

 form, all of which act as stimuli under normal conditions, do so no 

 longer, and the nematocysts enclosed by their anesthetized mother 

 cells fail to explode. These results seem to point conclusively 

 toward the nematocyte as a factor in the normal discharge of a 

 nematocyst, and this in spite of the fact that distilled water, Klein- 

 enberg's picro-sulfuric acid, sublimate acetic, acetic acid, ammo- 

 nium hydrate, and ether, are as effective on narcotized material as 

 on normal. All of these liquids are highly penetrating, or contain 

 very penetrating elements, or have specific gravities, so little above 

 that of distilled water, that they act under all circumstances, as 

 though the mother tissues, normal or narcotized, were not there. 

 Heat also is effective when applied to narcotized nematocytes, 

 either because the nematocysts under its influence absorb water, 

 or because their contents break down (p. 373.)- In addition to 

 the explanations suggested, it is possible that a nematocyte narcot- 

 ized sufficiently to be unresponsive to certain stimuli, it is not neces- 

 sarily sufficiently under anesthesia to render all stimuli ineffective. 

 Why then do the nematocysts of Coelenterates explode under 

 normal conditions ? Since they are completely enclosed by the 

 fluid contents of the nematocytes, contraction on the part of these 

 cannot be effective, since a uniform external pressure, no matter 

 how high it may be, is incapable of causing discharge. The 

 possibility of a distorting pressure produced by the nematocyte is 

 not absolutely ruled out, though we know of no mechanism by 

 which it might be produced. Appeal to undiscovered cytoplasmic 

 fibrillae might be made, but with little profit. The osmotic theory 

 on the other hand can be applied here also even if direct evidence 

 is still wanting. 



