SEA- ANEMONES : THEIB WEAPONS. 878 



cerned a double outline to the walls themselves, the op- 

 tical expression of their diameter; but have never de- 

 tected any, even the least, appearance of any tissue start- 

 ing from the walls, as the ecthoreum 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 injection ; for I have many times seen 

 floating atoms driven forcibly along the interior of the 

 ecthoreum, sometimes swiftly, and sometimes more delibe- 

 rately. Nothing that I have seen would lead me to con- 

 clude that the wall of the cnida is ciliated. 



I consider, then, that this fluid, holding organic 

 corpuscles in suspension, is endowed with a high degree 

 of expansibility ; that, in the state of repose, it is in a 

 condition of compression, by the inversion of the ectho- 

 reum ; and that, on the excitement of a suitable stimulus, 

 it forcibly exerts its expansile power, distending, and, con- 

 sequently, projecting, the tubular ecthoreum, the only 

 part of the wall that will yield without actual rupture. 



It has been proved that the execution of these weapons 

 is as effectual as their mechanism is elaborate. The wire 

 shot with such force penetrates even to its base the tissues 

 of the living animals which the Anemone attacks ; and then 

 its barbs preclude the withdrawal of the dart. But the en- 

 trance of bodies so excessively slender would of itself 

 inflict little injury ; there is evidently the infusion at the 



