SEA-ANEMONES I THEIR WEAPONS. 865 



into as close contact as they can be. A high power now 

 being put on, examine the organs in question. 



You see a multitude of perfectly transparent, colourless 

 vesicles, of a lengthened ovate figure, considerably larger 

 at one end than at the other ; one of average dimensions 

 measures in length ^ru^ of an inch, and in greatest 

 diameter -s-gV^th. In the larger (the anterior) moiety, 

 passing longitudinally through its centre, is seen a slender 

 chamber, fusiform or lozenge-form, about ^sV^th of an 

 inch in its greatest transverse diameter, and tapering to a 

 point at each extremity. The anterior point merges into 

 the walls of the cnida at its extremity ; while the posterior 

 end, after having become attenuated like the anterior, 

 dilates with a funnel-shaped mouth, in which the eye can 

 clearly see a double infolding of the chamber-wall. After 

 this double fold the structure proceeds as a very slender 

 cord, which, passing back towards the anterior end of the 

 capsule, winds loosely round and round the chamber, with 

 some regularity at first, but becoming involved in contor- 

 tions more and more intricate, as it fills up the posterior 

 moiety of the cavity. The fusiform chamber appears to 

 be marked on its inner surface with regularly recurring 

 serrations, which are the optical expression of that peculiar 

 armour to be described presently. 



Under the stimulus of pressure, when subjected, as 

 now, to microscopical examination, and doubtless under 

 nervous stimulus, subject to the control of the will, during 

 the natural exercise of the animal's functions, the cnida 

 suddenly emit their contents with great force, in a regular 

 and prescribed manner. It must not be supposed, how- 

 ever, that the pressure spoken of is the immediate mechani- 

 cal cause of the emission : the contact of the glass-plates 

 of the compressorium is never so absolute as to exert the 

 least direct force upon the walls of the capsule itself; but 

 the disturbance produced by the compression of the sur- 

 rounding tissues excites an irritability, which evidently re- 



