432 THE AQUARIAN NATURALIST. 



three feet, but ordinarily not more than about six 

 inches long (PI. VII. fig. 9). When a portion of this 

 gelatinous mass is placed in a small glass trough of 

 sea-water, multitudes of little polyps are soon ob- 

 served emerging from hexagonal cells upon its sur- 

 face, in such numbers as to cover it with a coating 

 resembling the finest down, and moreover so closely 

 set, that there seems to be hardly room for them to 

 spread forth their tentacula. In this state, indeed, it 

 is scarcely possible to make any observations upon 

 them ; but when a few only project, they become, from 

 their extreme delicacy and transparency, peculiarly 

 favourable subjects for examination under the micro- 

 scope, and soon reveal themselves to be Polyzoa as 

 elaborately organized as those inhabiting the cells of 

 the Flustrse described in the last chapter. 



In this species the tentacula are sixteen in num- 

 ber, and fully two-thirds the length of the body of 

 the polyp ; they are, moreover, extremely slender and 

 flexible. When expanded, they are frequently seen to 

 roll up closely upon themselves, even down to their 

 base, the revolution taking place either inwardly or 

 outwardly, and in one or more arms at the same 

 time. These tentacles, we need hardly say, are 

 densely covered with cilia of inexpressible delicacy, 

 transparent, and almost as imperceptible as 



" the fibrous cloud 



That catches but the faintest tinge of morn, 

 And which the straining eye can scarcely see." 



Nevertheless, the action of the tentacular cilia appears 

 to be entirely under the control of the animal, and 



