PLUMATELLID^ : ALCYONELLA. 397 



when expanded therein, resembles nearly the figure of a bell with 

 the mouth upwards ; and is usually about the length of half an 

 inch, and one quarter of an inch in breadth or diameter. This case 

 being very transparent, all the motions of its inhabitants may be 

 discerned through it distinctly. It seems divided internally into 

 several apartments, or rather to contain several smaller sacculi, each 

 of which incloses one of these animals. The openings at the tops of 

 these sacculi are but just sufficient to admit the creature's head, 

 and a very small part of its body, to be thrust out beyond them, the 

 rest remaining always in the case. The animal can, however, when 

 it pleases, draw itself entirely down within the case, which is an 

 asylum to secure it from its enemies, (for it is not unlikely many of 

 the larger aquatic insects prey upon it,) and a safe and agreeable 

 retirement wherein to perform the functions of digestion, sleep, and 

 the other necessary calls of nature. This case it can, I say, retire 

 into at pleasure ; and it never fails to do so when any sudden motion 

 of the water or of the vessel it is in disturbs it : as also when it has 

 seized with its arms any of the minute insects which serve for its 

 food. 



" The arms are set round the head to the number of forty, having 

 each the figure of a long /, one of whose hooked ends is fastened to 

 the head; and all together when expanded compose a figure some- 

 what of a horse-shoe shape, convex on the side next the body, but 

 gradually opening and turning outwards, so as to leave a consider- 

 able area within the outer extremities of the arms. And when thus 

 extended, by giving them a vibrating motion, the creature can pro- 

 duce a current in the water, which brings the animalcules, or what- 

 ever other minute bodies are not beyond the sphere of its action, 

 with great velocity to its mouth, whose situation is between the 

 arms, where they are taken in if liked, or else by a contrary current, 

 which the creature can excite, they are carried away again ; whilst at 

 the same time other minute animalcules or substances, that by lying 

 without-side the inclosure made by the arms are less subject to the 

 force of the stream, are frequently seized by them : for their sense of 

 feeling is so exquisite, that on being touched ever so slightly by any 

 such little body, it is caught immediately and conveyed to the mouth. 

 However, one may observe the creature is sometimes disappointed in 

 its acquisition, for after drawing down one of the arms suddenly 

 inwards towards the mouth, it may be perceived slowly extending 

 itself again without the creature's retiring into its case; which it 

 fails not to do on meeting with anything worth the while. 



