34 ZOOLOGY. 
words of Dana, “ within the polyp, as completely as the skull of an animal 
beneath its fleshy covering. All corals are more or less cellular, and 
through these cellules the animal tissues extend.” In some, however, the 
coral is exposed, as when the increase takes place by a terminal secretion 
upon a separate stem, when the apex alone is living, and as the stem 
increases in length the part below dies. This increase above and death 
below are common in most corals, and to this the great masses of coral are 
attributable. According to Dana, a solid dome of Astrea, twelve feet in 
diameter, has a living exterior of cule a a half or three Rimes of an inch in 
éhiakeias. 
The classification adopted here is chiefly that of James D. Dana, as given 
in his magnificent work on Zoophytes, the result of his labors in the United 
States Exploring Expedition. The characters of the families are in most 
cases condensed from the same work. 
The Order Actinoma includes not only the flower-shaped genera, like 
Actinia (pl. 77, figs. 5, 6), which do not secrete a coral, but also numerous 
coralligenous genera. The name of this order, from the Greek ax, a 
ray, is in allusion to the radiated arrangement of the tentacles, which, 
when expanded, in many cases resemble the petals of a flower. When 
contracted this resemblance disappears, and the mass may be compared to 
alemon in shape. Lesueur has described a species (A. margmnata) from 
Massachusetts Bay. (Jour. Acad. Nat. Sci. i. 172.) 
The Actinize are found in the sea, attached to stones, submerged timber, 
r&c. They have the power of ae pee and floating, and 
of creeping slowly upon their flat base, at the rate of about two inches in 
an hour. The texture of the exterior is either fleshy or coriaceous, the 
surface slimy, smooth, or tuberculous, and very sensitive. The mouth is 
simple, and fringed by the tentacles. These organs being tubular, they are 
expanded by having water forced into them, and when they contract, the 
water is ejected through a minute terminal perforation. The tentacles of 
some species resemble the Acalephee in having a stinging power. 
The interior of the Actiniz is taken up with the stomach, which isa 
simple sac, of which the mouth is the opening, and extending nearly to the 
base of the animal, where it communicates with the visceral cavity, 
occupying the space between the stomach and the exterior wall. The 
cavity is provided with a series of vertical muscular partitions, more or 
less perfect, which extend from the exterior wall to the stomach, so that a” 
transverse section of the animal would resemble a wheel, of which the nave 
would represent the stomach, and the spokes the visceral partitions. 
The Actiniz feed upon fish, crabs, shell-fish, &c., the shells and other 
indigestible parts being ejected from the mouth after a period of ten or 
twelve hours. A large individual sometimes accidentally swallows a smaller 
one, but the latter is usually cast out unharmed, as in the case of the 
Hydra. The objects swallowed are sometimes as large as the Actinia 
itself in a state of repose. The following account is given in G. J ohnston’s 
excellent History of British Zoophytes. 
“T had once brought me a specimen of Act. gemmacea, that might have 
238 
