TENTACLES AND POISOX THREADS. 51 



small cells or capsules, from some of which a very 

 slender wire or thread will be emitted.* These are 

 the stinging organs of the polyp, and resemble those 

 which Mr. Gosse has so ably elucidated in the sea 

 anemones. Some writers have endeavoured to shew 

 that they are not stinging organs at all, but so 

 large an amount of evidence to the contrary is 

 accumulated in jMr. Gosse's "Actinologia Britannica," 

 that no reasonable doubt remains. The stinging 

 capsules of the polyp are shewn in the annexed 

 sketch, and also the way in which they are employed, 

 for it fortunately happened that on exposing one 

 of the hydras to pressure in the live box, a small 

 worm (ArtguiUiiIa) escaped, which had been pierced 

 with the minute weapons which are supposed to 

 convey a poison into the wound. The authors of 

 the "iMicrographic Dictionary" think that the prongs 

 of the forks, which will be seen to point upwards 

 in the sketch,t are springs, and occupy a reversed 

 position in the capsule cells, and that their func- 

 tion is to throw out the threads. However this 

 may be, the polyps, and similarly endowed creatures, 

 have the power of darting out their poison-threads 

 with considerable force, and Mr. Gosse found that 

 tile anemone was able to pierce a thick piece of 

 human skin. 



The same excellent observer attributes the emis- 



* See page 47, C and D. f See page 52. 



