" It is in seizing and devouring their prey however, that the habits of the Actinice are best exemplified. They will remain for hours with their arms fully expanded and motionless, waiting for some passing animal which chance may place at their disposal, and when the opportunity arrives, are little inferior to the Hydr in their voracity or powers of destroying their victims. Their food generally consists of crabs or shell-fish, animals apparently far superior to themselves in strength and activity, but even these are easily overpowered by the sluggish yet persevering grasp of their assailant. No sooner are the tentacles touched by a passing animal, than it is seized and held with unfailing pertinacity : the arms gradually close around it ; the mouth placed in the centre of the disc, expands to an extraordinary size ; and the creature is soon engulphed in the digestive bag of the Actinix, where the solution of all its soft parts is rapidly effected, and the hard, indigestible remnants speedily cast out at the same orifice. The Actinim, although exceedingly voracious, will bear long fasting. They may be preserved alive for a whole year, or perhaps even longer, in a vessel of sea-water, without any visible food ; but when food is offered, one of them will devour a crab, as large as a hen's egg or two muscles in their shells ; in a day or two, the shells are voided through the mouth, perfectly cleared of the soft parts which they contained. The tentacles have the same prehensile power as those of the Hydrce, a power which depends on the presence of projectile barbed weapons, ordinarily coiled in elastic cells. These organs are coiled in in conceivable multitudes imbedded in the tissues of the tentacles, of the lips, of the stomach, of the frilled ovarian bands, and especially, in some species, in long threads which are protruded from pores in the integuments of the body. The structure of these weapons is as follows :—each consists of an oval or elliptical sac of transparent membrane, within which is seen a thread coiled up, and in some instances, an oblong or lozenge-shaped chamber. At the pleasure of the animal, or under the stimulus of pressure, the thread is shot forth from one end of the cell with great force, until it extends to a length of from twice to fifty times that of the cell. When fully extended, it seems that the thread is but a continuation of the cell itself; that when it was dormant, it was turned in; and that in the process of ex pulsion, every part of its length has actually been turned inside out, like the finger of a glove. Sometimes the thread appears
simple, but in those cases, in which a chamber appeared with in the cell, it is furnished with an armature of barbed threads, which, after the expulsion, project from the sides of the thread in all directions. Xhe propulsion of the thread is sufficiently forcible to enable it to enter the tissues of other animals, and the barbed structure enables the weapon to retain its hold in the flesh, which facts warrant the presumption that a highly poisonous fluid is at the same time injected, capable of arresting and destroying the animal life. Although the prey of the Actinia usually consists of crustacea, the smaller mollusca and star fishes ; it is sometimes of much greater dimensions. Dr. Johnson observes, "I had once brought me a specimen of Actinia crassicornis, that might have been originally, two inches in diameter, and that had somehow contrived to swallow a valve of the great scallop (Peeten maximus) of the size of an ordinary saucer. The shell fixed within the stomach was so placed as to divide it completely into two halves, so that the body stretched tensely over, had become thin and flattened like a pancake. All conamnnication between the inferior portion of the stomach and the mouth was of course prevented, yet instead of emaciating and dying of an atrophy, the animal had availed itself of what had undoubtedly been a very untoward accident, to increase its enjoyments and its chance of double fare.' A new mouth fur nished with two rows of numerous tentacula was opened up on what had been the base and led to the under stomach. The in dividual had indeed become a sort of Siamese twins, but with greater intimacy and extent in its unions." Metridium PrEetextum, (J. P. Couthony,) exhibited wholly in the plate, is generally found with its body covered with sand, having its disc expanded on a level with the surface. When mo lested they entirely conceal themselves beneath the sand. Spe cimens were obtained off Santa Cruz : also on the north side of the harbor, near Praya Grande. Another allied species was observed by Dr. C. Pickering in the sand among the rocks out side of the harbor.