8EA-ANEM02TES : THEIR WEAPONS. 427 



explosive violence with wliicli the nipple-like end of 

 the cnida gives Ava}^ and the contents burst foi'th ; as 

 also the exti-enie rapidity witli which, ordinarily, the 

 whole length is evolved. A curious example of this 

 force once excited my admiration. The ecthormum 

 from a cnida of Corynactis vii'dis was in course of 

 rapid evolution, when the tip came full against the 

 side of another cnida already emptied. The evolution 

 was momentarily arrested, Lut tiie wall of the empty 

 capsule presently was seen to bend inward, and sud- 

 denly to give way, the ecthorceurn forcing itself in, and 

 shooting round and round the interior of the cnida. 



" The most careful observations have failed to reveal 

 a lining membrane to the cnida. I have repeatedly 

 discerned a double outline to the walls themselves, the 

 optical expression of their diameter ; but have never 

 detected any, even the least, appearance of any tissue 

 starting from the walls, as the ecthorceum bursts out. 

 My first supposition, reluctantly resigned, was, that 

 some such lining membrane, of high contractile 

 power, lessened, on irritation, the volume of the cavity, 

 and forced out the wire. 



" The cnida is filled, however, with a fluid. This 

 is very distinctly seen occupying the cavity when, from 

 any impediment, such as above described, the wire 

 flies out fitfully ; waves, and similar motions, passing 

 from wall to wall. Sometimes, even before any portion 

 of the wire has escaped, the whole mass of tangled 

 coils is seen to move irregularly from side to side, 

 within the capsule, from the operation of some intestine 

 cause. The emission itself is a process of h^jection y 

 for I have many times seen floating atoms driven for- 

 cibly along the interior of the ecthorcBuin^ sometimes 



