ACTINIADAE - ANEMONES "A Sea anemone, is a radiate animal, or actiniform polype. Character.—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 disc, very dilatable, surrounded by one or more rows of tentacula. Oviparous and viviparous ; marine."—A sea anemone is a helian thoid or sun-flower shaped polype. " This family of polypes, from the fibrous character which the substance of their body as sumes, have been named by zoologists, ' Fleshy Polypes.' The body of an Actinia, when moderately expanded, is a fleshy cylin der, attached by one extremity to a rock or some other sub-ma rine support ; whilst the opposite end is surmounted by numerous tentacula, arranged in several rows around the oval aperture, when these tentacula are expanded, they give the animal the appearance of a flower, a resemblance which is rendered more striking by the beautiful colors which they not unfrequently as sume ; and hence, in all countries, they haye been looked upon by the uninformed as sea-flowers, and distinguished by names indicative of the fancied resemblance. Their animal nature is soon, however, rendered evident, by a little attention, to their habits. When expanded at the bottom of the shallow pools of salt water left by the retreating tide, they are seen to manifest a degree of sensibility, and power of spontaneous movement, which we should little anticipate from their general aspect. A cloud veiling the sun will cause their tentacles to fold, as though ap prehensive of danger from the passing shadows; contact, how ever slight, will make them shrink from the touch; and if rudely assailed, they completely contract their bodies, so as to take the appearance of a hard coriaceous mass, hardly distinguishable from the substance to which they are attached.
" The like the Hydra, possess the power of chang ing their position. They often elongate their bodies, and re maining fixed by the base, stretch from side to side, as if seeking food at a distance ; they can even change their place, by gliding upon the disc which supports them, or detaching them selves entirely, and swelling themselves with water, they become of nearly the same specific gravity as the element which they inhabit, and the least agitation is sufficient to drive them else where : when they wish to fix themselves they expel the water from their distended body, and sinking to the bottom, attach themselves again by the disc at their base, which forms a power ful sucker. From this sketch of the outward form of these polypes, we will be prepared to examine their internal economy, and the more minute details of their structure. On examining attentively the external structure of the body, it is seen to be covered with a thick mucous layer, resembling a soft epidermis, which extending over the tentacula and the fold around the aperture of the mouth, is found to coat the surface of the stomach itself ; this epidermic secretion forms, in fact, a deciduous tunic which the creature can throw off at intervals. On remov ing this, the walls of the body are seen to be made up of fasci culi of muscular fibre, some running perpendicularly upwards towards the tentacula, and others which cross the former at right angles, passing transversely around the body ; the meshes formed by this interlacement are occupied by a multitude of granules, apparently of a glandular nature, which give the integument a tuberculated aspect : these granules are not seen upon the suck ing disc at the base.
" The tentacula are hollow tubes, composed of fibres of the same description. The stomach is a delicate folded membrane, form
ing a simple bag within the body. It seems to be merely an ex tension of the external tegument, somewhat modified in texture. It is closed inferiorly, the same orifice serving both for the intro duction of food, and the expulsion of effete, or indigestible matter. On making a section of the animal, the arrangement of these parts is distinctly seen—the muscular integument, the tentacula, formed by the same fibrous membrane—and the stomach, which is apparently derived from it. Between the di gestive sack, and the fibrous exterior of the body, is a consider able space, divided by a great number of perpendicular fibrous partitions, into numerous compartments, which, however, freely communicate with each other, and likewise with the interior of the tentacula. Every tentacle is perforated, at its extremity by a minute aperture, through which the sea-water is freely admit ted into these compartments, so as to bathe the interior of the body ; and when, from alarm, the animal contracts itself, the water, so admitted, is forcibly expelled in fine jets through the holes by which it entered. There can be no doubt that the surrounding fluid, thus copiously taken into the body, is the me dium by which its respiration is effected ; and every one who has been in the habit of keeping Actinice in glass vessels for the purpose of watching their proceedings, must have noticed, that as the fluid, in which they are confined, becomes less respirable, from the deficiency of air, the quantity taken into the body is enormous, stretching the animal until it rather resembles an inflated bladder than its original shape. It is in the compartments, which are thus at the will of the creature distended with water, that we find the convoluted and frilled bands which constitute the ovaries, covered with cilia. The germs which are there developed find their way out through a duct, which opens at one angle of the mouth. The eggs found in the ovaria, are round and of a yellowish color, resembling minute grains of sand. The oviger ous membrane which secretes these eggs, is, through its whole extent, bathed with water, admitted into the compartments in which it is lodged, a circumstance which provides for the respi ration of the ova during their development. It is a pleasing sight, and one, by no means uncommon, to see five, ten, or twenty young, of various sizes, but perfect in form, expelled from the duct and dispersed around, where they soon attach themselves, and constitute a colony around their parent. The young while in the body of the parent, are not unfrequently found in the hollow tentacles which communicate freely with the interseptal chambers ; and Sir John Dalyell thought this was their normal position. He says in the course of six years, a specimen pre served by the author produced above two hundred and seventy six young ; some pale and like mere specks, with only eight ten tacula ; others florid and with twenty. They are frequently dis gorged along with the half digested food ; thirty-eight appearing thus at a single litter.' The abbe Dicquemare relates several curious experiments on the multiplication of these animals by mechanical division. When transversely divided, the upper por tion still stretched out its tentacles in search for food, which, when seized, sometimes passed through its mutilated body, but was occasionaly retained and digested. In about two months, tentacles grew from the cut extremity of the other portion, which soon afterwards began to seize prey. By similar sections, he even succeeded in making an animal with a mouth at each end.