INTRODUCTION. XXIX 



wisdom working to a given end by perfectly adequate 

 means. The ejected acontia, loaded with their deadly 

 cnidae in every part of their length, carry abroad their 

 fatal powers not the less surely, than if each had been 

 provided with a proper tube leading from its free extremity 

 to the nearest cinch's. 



The Cnidce. — I come now to describe those minute but 

 potent organs which constitute the object of all the mecha- 

 nism above described. Four distinct forms of these cap- 

 sules have occurred to my investigations ; and these I shall 

 treat of in turn. 



(1.) Chambered Guides {Cnidce cameratte). This is 

 perhaps the most generally distributed form, as it is 

 manifestly the most elaborately armed. It may be well 

 examined in Caryophyllia SmitJiii. The globular heads 

 of the tentacles seem, under pressure, to be literally com- 

 posed of these capsules, the ends of which project side by 

 side, as close as they can be packed, one against another. 

 The form of these is long and slender, almost linear. The 

 craspeda are also similarly studded with c?iidce, which are, 

 however, of longer dimensions, and of fuller form. As I have 

 seen no chambered cnidse, in any species, so large as these, I 

 shall take them as a standard for description, alluding to 

 those of other species only when they differ from these. 



They are perfectly transparent, colourless vesicles, of a 

 lengthened ovate figure, considerably larger at one end 

 than at the other (Plate XI. fig. 6). One of average 

 dimensions measures in length '004 inch, and in greatest 

 diameter *0005. In the larger (the anterior) moiety, is 

 seen, passing longitudinally through its centre, a slender 

 chamber, fusiform or lozenge-form, about '00015 inch in 

 its greatest transverse diameter, and tapering to a point at 

 each extremity. The anterior point merges into the walls 

 of the cnidce 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 contortions more and 

 more intricate as it fills up the posterior moiety of the 

 cavity. The fusiform chamber appears to be marked on 



