272 MR. GOSSE ON PEACHIA HASTATA. 



have the well-marked character of projecting, from pores in the exterior of the body, 

 whenever they are irritated, thread-like fdaments, in great abundance and to great length, 

 which are again withdrawn into the body. These filaments, when examined with a high 

 power, are seen to be chiefly composed of thread-capsules, or "nettling-organs;" and I 

 have given elsewhere* evidence to show that their function is that of efficient weapons of 

 offence, paralysing even vertebrate animals, with which they are brought into contact. 

 Every one who has handled A. parasitica, venusta, or any of the species with missile 

 threads, is aware of the great tenacity with which these filaments adhere to the fingers. 

 This is owing to the penetration of the epidermis by the myriads of ejected threads, and 

 to the hold which their barbed structure enables them to retain. For when these nettling 

 organs are examined, say with a power of 500 diameters, the thread is perceived to be 

 armed in a manner which gives them a superiority over those of all the non-shooting 

 species ; and thus the structure of these organs affords us another excellent and constant 

 generic character. There are, indeed, in these species, always to be found many thread- 

 capsules of the ordinary form and structure, viz. linear-oblong, emitting a thread which 

 is apparently simple, and of great length, extending to about twenty times the length of 

 the capsule. But the principal portion of the capsules are of another form, being long- 

 oval with a distinct longitudinal chamber, and emitting a thread, never exceeding thrice 

 the length of the capsule, and more commonly one or one and a-half times, as in A. Bellis 

 (fig. 10), and in A. Troglodytes (fig. 11). The terminal portion of this thread (including 

 from half to more than three-fourths of its length, according to the species) is barbed 

 with close-set bristles radiating on all sides like the hairs of a bottle-brush, and more or 

 less reverted. In A. venusta (fig. 7), a zigzag lineation is discernible on the thread, 

 which seems to indicate that the hairs are set on in a spiral arrangement. Before emis- 

 sion, the thread-chamber is very distinct in this species (fig. 8), running through the 

 whole length of the capsule, slightly bent in a sigmoid curve, and gradually merging into 

 the capsule-walls at the discharging end. In some instances the thread is discharged, in 

 every respect agreeing with that just described, but perfectly simple and without barbs 

 (fig. 9) : I think that this occurs when the emission has been very slow ; that the barbed 

 hairs fly out only when the missile force is sudden ; that, otherwise, they continue 

 appressed to the sides, and invisible. I can discover no trace of the spiral in the un- 

 emitted thread. 



This brush-like form of the nettling-thread I find in ten of our native species of Actinia 

 (which I shall presently enumerate), invariably co-existent with the power of emitting 

 filaments spontaneously. They are marked also by other characters, of less importance 

 because less definite : — the tentacles are generally of small size, slender, numerous, and 

 much crowded ; the body is soft, rarely coriaceous, and smooth, though commonly per- 

 forated with sucking glands, which are distinct from the emitting pores ; and the colours 

 of the body often have a tendency to run in longitudinal bands, and those of the tentacles 

 to form arrow-heads. The genus thus characterized I propose to call Sagartiaf. 



The remaining British species (for I beg it to be observed that I am speaking only of 



* ' Devonshire Coast,' passim ; 'Aquarium,' pp. 115, 143, 148. 



f " There is a certain nomadic race called Sagartians. . . . The mode of fighting of these men is as follows : — 



