Marvels of Pond-Life. 39 



fortunately happened that on exposing one of the 

 hydras to pressure in the live box, a small worm 

 {Anguillula) escaped, which had been pierced with the 

 minute weapons which are supposed to convey a poison 

 into the wound. The authors of the c Micrographic 

 Dictionary ' think that the prongs of the forks, 

 which will be seen to point upwards in the sketch,* 

 are springs, and occupy a reversed position in the 

 capsule cells, and that their function 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 the anemone was able to pierce 

 a thick piece of human skin. 



The same excellent observer attributes the emission 

 of the anemone poison threads, which he considers 

 hollow, to the injection of a fluid. In their quiescent 

 state, he thinks they are drawn in, like the finger of a 

 glove, and are forced out as the liquid enters their 

 slender tubes. Possibly the polyp stinging organs may 

 have the same structure. 



Notwithstanding their dangerous weapons, polyps 

 are often infested with a parasite, the Trichodina pedi- 

 culus, as shown in Fig. e, page 49, and it must happen 

 that either this visitation is not disagreeable, or that 

 the Trichodina is not influenced by the poison. 



As the plants in the bottles decayed, some of the 

 animalcules died off and others appeared. In one 

 bottle, containing i ecaying chara, Paramecia abounded. 

 The Paramecia, ot which there are various species, 



* See page 38. 



