ACTINFAH2E, a family of Heliantboid Polypes, having for its type the old genus A ctinia, the Sea Anemonies. It has the following characters. Animal single, fleshy, elongate or conical, capable of extending or contracting itself, fixed by its base, but with the power of locomotion ; mouth in the middle of the upper disk, very dilatable, surrounded by one or more rows of tentacula ; oviparous and viviparous • marine.
The internal structure of the Actinic has been care fully investigated by Spix, Teale, and others. They pos sess an alimentary cavity, with a single aperture, very large at the lower end, and so elastic and contractile that it can easily be turned inside out. The cavity is surrounded with flat muscles, running lengthwise and parallel The egg organ (ovarium), according to Teale's obser vations in Actinic coriacea, forms elongated masses attached along the inner border of a series of organs called leaflets, fig. 2, Is h. " Each ovary is composed of several folds or plaits, which, when unfolded, show this structure to be about three times the length it assumes when attached to the leaflet. By carefully spreading out these folds, the ovary, with the assistance of a lens, is seen to consist of two very delicate layers of membrane, enveloping a closely com pacted layer of ova. After enveloping the ova, the mem branous layers are placed in apposition, and form a kind of mesentery, by which the ovary is attached to the in ternal border of the leaflet." The A ct iniathe propagate all the year round, although perhaps in some species the ova are deposited most abundantly in autumn. The ova are roundish, and like those of polypes in general, are moved by means of vibratile cilia, which cover their surface. After being discharged from their parent they move about actively for several days, during which they undergo some change in form. They then relax their activity, the cilia NAT. 111ST. Dry. VOL. 1.
are absorbed, they attach themselves to a spot, and pass through a series of forms, before arriving at maturity.
Although Spix has described in Actinia coriacea a nervous system, this has not been confirmed by more recent observers.
The habits of the Actinice have been studied by the Abb6 Dicquemare and others. The forms of A ctinice vary according to their contraction
or expansion, presenting in numerable varieties. Their expansion is said to be a more certain indicator of fine weather than the rise of the barometer ; but this cannot be practically taken advan tage of except during summer, as the cold of winter drives the Actinice from the shore to the deeper waters, where the temperature is more equable and mild. On changing their place of abode, some abandon ,themselves to the mercy of the waves, others creep along the bottom, turning them selves inside out, and making use of their tentacula as feet. When they find a suitable place, they fix them selves, often so firmly, that they cannot be detached without tearing their bodies.
Our distinguished English naturalist, Ellis, has given a very minute and, so far as it goes, an accurate account of these animals in the Philo sophical Transactions,' vol. lvii., part of which it may be interesting to quote :— " The lower part," he says, "of these bodies have a com munication with a firm, fleshy, wrinkled tube, which sticks fast to the rocks, and sends forth other fleshy tubes, which creep along them in various directions. These are full of different sizes of these remarkable animals, which rise up irregularly in groups near to one another.
"This adhering tube, that secures them fast to the rock or shelly bottom, is worthy of our notice. The knobs that we observe are formed in several parts of it by its insinuating itself into the inequalities of the coral rock, or by grasping pieces of shells, part of which still remain in it, with the fleshy substance grown over them.
This shows us the instinct of nature, that directs these animals to preserve them selves from the violence of the waves, not unlike the anchoring of mussels, by their fine silken filaments that end. in suckers ; or rather, like the shelly basis of the Serpula, or worm-shell, the tree-oyster, and the slipper-barnacle, &c., whose bases conform to the shape of whatever substance they fix themselves to, grasping it fast with their testaccous claws, to with stand the fury of a storm.