194 
POPULAR SCIENCE REVIEW. 
they have never been seen to take part in the prehension of 
food. It is, however, indirectly obtained by means of the 
arms. 
On the upper surface of each arm and pinnule there is (in 
most cases) a narrow groove (PI. Y. fig. 2, f.g., and PI. YI. 
fig. 1, f.g.), which is lined by a number of those delicate 
little protoplasmic filaments, known to naturalists as cilia. 
These are in a state of continual vibratory movement, which i& 
always in the same direction, viz. towards the mouth. Cur- 
rents are thus set up in these food- grooves, all making for the 
mouth, to which the grooves converge. Any of the small 
alimentary particles scattered in the water which may happen 
to settle down in one of these food- grooves are thus carried 
along it towards the mouth. The grooves of adjacent arms 
unite in succession so as to form from five to ten primary 
groove- trunks, which end in a peristomial area of variable 
size and shape. This may be either almost in the centre of 
the body (Pl. Y. fig. 1 and PI. YI. fig. 12), or altogether 
eccentric (PI. YI. fig. 11). Within this peristomial area is a 
narrow slit, the mouth ( m ), into which are poured the contents of 
the various food-grooves. This, though mostly microscopic, 
appears to vary very much in character, according to circum- 
stances. Dr. Carpenter has found the stomach of the Arran 
ComatulcB to contain large quantities of the horny remains of 
infusorial animalcules, while in other specimens the horny 
casings of Entomostraca, or of the larvse of higher Crustacea, 
have been found in the stomach. I have myself removed from 
the stomach of a large tropical Comatula the body of an Isopod 
Crustacean nearly half an inch long, while in another case I 
have found the food-grooves to contain numerous foramini- 
feral shells, Rotalice , Biloculince, and others. 
The whole of the coiled digestive tube is lodged in the body 
of the Comatula , no part of it extending into the arms (PI. Y. 
fig. 1, cl.) This body consists of two parts, (1) the cup or calyx 
formed by the skeleton, and (2) the visceral mass, usually 
termed the disc, which is supported in this cup, but is sometimes 
very readily detached from it, as has been the case with the discs 
represented in PI. YI. figs. 11, 12. The disc is usually more or 
less hemispherical in shape (PI. Y. fig. 1), the lower convex por- 
tion fitting into the cup, while on the flattened upper surface (PI. 
YI. figs. 11, 12) is the mouth, with the food- grooves converging 
towards it, and a tubular projection, at the end of which is the 
second opening of the digestive canal.* When the mouth is 
central, as in the genus Anteclon (PI. YI. fig. 12), the anal tube 
( a.t .) is in one of the interradial spaces on the disc between two 
of the food- grooves ; but when the mouth is eccentric, as in 
* I have one monstrosity, an Actinometra, with two mouths and two 
anal tubes. 
