2. Actinia, or Sea-Anemone.

The beautiful genus thus denominated from its resemblance to the Bower of this name when its feelers or tentacles are expanded, is characterized by having an oblong body, of an extensile and expansile nature, and adhering by the base to rocks and other marine substances. The mouth is situated in the centre of the upper part or disc, and is surrounded by very numerous, soft, extensile feelers, or arms, spreading in the manner of rays, and disposed in a single, double, or triple series, according to the different species. The Actiniæ are very common on the rocks of most of the European coasts: when in their contracted state, they have the appearance of inanimate rounded masses of coloured pulp, or flesh; and when expanded, they greatly resemble the appearance of an expanded polypetalous flower, particularly those of the anemone and ranun. culus tribe. One of the most common British species is the actinia varia*, found on most of our coasts, and varying ad infinitum in its colours, being either red, olive, green, of different shades, and either plain or variously spotted: its principal character, and which distinguishes it in whatever variety of general colour it may happen to appear, consists in a row of short bead-like prominences, surrounding the external row of tentacula: these bead-like processes are invariably of a bright blue colour. The actinia varia in general, measures about two inches in diameter, at the base, but is occasionally seen of a larger size.

A more beautiful species is, however, found on our own coasts; generally imbedding itself in the sand, instead of adhering to rocks; it is called the actinia crassicornis, and is distinguished by its red colour, and roughish external surface; while the central or middle part, when expanded, is white, most elegantly marked near the base of the tentacula, with numerous carmine-coloured streaks: the tentacula themselves, being of a pearl-colour, and of a much thicker or more swelled appearance than in most other species. The actinia crassicornis often measures four, five, or even six inches in diameter when in its expanded state.

The actiniæ, or sea-anemonies, are naturally very voracious animals, preying not only on the softer sea-animals, but on such as are

guarded by a shelly defence; they swallow various kinds of univalve shell-fish, the smaller kind of crabs, and other animals; and when they have absorbed the juices of their prey, they reject the shell or other integument by the mouth. When kept in vessels of sea-water, which may be easily practised, they seem to require no particular nutriment, absorbing a sufficient quantity of animal gluten, from the sea-water itself, for all the purposes of nutrition. In this confined state they do not grow or increase in size, though they frequently produce a numerous offspring, being of a very prolific nature, and viviparous. The young are produced of various sizes, from that of a pin's head to that of half an inch in diameter, and to the number of five, ten, or more at a birth. As these ani. mals are allied to the polype tribe in some degree, they partake of their qualities, and will reproduce many of their organs, when either purposely or accidentally mutilated.

3. Astertas, or Star-Fish.

Most of these are of a stellated or radiated shape, as their name imports; the rays differing in number in different species, from five to ten or twelve. The most curious of the whole tribe, is A. Caput Medusæ, of Linnæus, or Medusa's head star-fish. It grows to a large extent, measuring more than two feet in diameter when the limbs are fully extended. This very extraordinary animal is first divided into five equidistant, jointed processes, each of which is soon subdivided into two other smaller ones; and each of these, at a somewhat farther distance, into two others, still smaller; this mode of regular subdivision, being continued to a vast extent, and in the most beautiful gradation of minuteness, till at length the number of extreme ramifications amounts to several thousands. By this most curious structure, the animal becomes, as it were, a kind of living net; and is capable of catching such creatures as are destined for its prey, by the sudden contraction of all its innumerable ramifications, and thus the object is secured beyond all power of escape. Examples of this animal, well worthy of notice, are to be found in the British, and were formerly in the Leverian Museum.

The sea-stars, in general, have a very considerable degree of reproductive power; and if injured by accidental violence, or if one or more of the limbs be cut or torn off, the animal will in time be furnished with new ones. They wander about the ocean in quest of

prey, more particularly near the shores; and feed not only on the softer sea-animals, but on the smaller shell-fish. Their mouth, which, as before observed, is situated beneath, is armed with hard and sharp teeth, resembling a kind of spines, and converging towards the centre of the mouth, and differing in number in the different species. We should not omit to observe, that the curious species last mentioned, the Medusa's head star-fish, is chiefly confined to the Indian seas, but is sometimes found in those of Europe. Those who may wish for a particular description of the anatomy of the star-fishes, may consult the observations of Reaumur on this subject, published in the Memoirs of the French Academy.

[Shaw.

SECTION V.

Testaceous Worms, or those possessing Shells.

We have already seen that these consist of three divisions, according to the number of valves or pieces of which the entire covering consists; and hence these divisions are denominated univalves, bivalves, and multivalves. We shall select a few of the most curious

instances of each.

Among the UNIVALVES, or those possessing only a single shell, the most common perhaps are the suail, (helix,) and the perri-winkle, (turbo,) kinds. Among the most interesting are the paper-nautilus, the pearl-nautilus, and the ship-worm. The animals inhabiting this description of shells, are, for the most part, the slug and the cuttlefish.

1. Paper Nautilus.

Argonauta Argo.-LINN.

"Among the principal miracles of nature," says Pliny, "is the animal called nautilos, or pompilos. It ascends to the surface of the sea in a supine posture, and gradually rising itself up, forces out, by means of its tube, all the water from the shell, in order that it may swim the more readily; then throwing back the two foremost arms, it displays between them a membrane of wonderful tenuity, which acts as a sail, while with the remaining arms it rows

course and thus it pursues its voyage; and if alarmed by any appearance of danger, takes in the water and descends."

The paper nautilus is an inhabitant of the Mediterranean and Atlantic seas. In the Indian seas is found a species so similar, that it has generally been considered as a variety: it differs in having the shell marked into numerous slight tubercles on each side the furrows. This is the variety described by Rumphius, in his account of its inhabiting animal, observed by him during his residence at Amboyna.

2. Pearl Nautilus.

[Edit. Plin. Shaw.

Nautilus Pompilius.-LINN.

This animal possesses a large and strong shell, often measuring five or six inches in length: it is of a very firm or dense fabric, of a shape somewhat compressed on the sides, with a very wide opening or mouth, and with the back part rolled into a spiral form within the cavity of the shell. The colour, externally, is a dull yellowishwhite, marked with numerous zebra-like yellowish brown or dusky bands; and within, of the richest and brightest silvery-pearl-colour. When the natural pellicle or epidermis of the outside is rubbed off, the whole shell appears silvery also. The great and striking character of the genus however, at least so far as regards the shell, is the extraordinary structure of the internal part, which is formed into a great number, (from thirty to forty) separate chambers or divisions, each communicating with the rest by a small tubular hole near the centre. The opening or mouth of the shell therefore presents a large but shallow concavity, pierced with a central or nearly central hole, and beyond lie all the divisions before-mentioned. The body or chief part of the inhabiting animal fills up the front or great concavity, and that only; while from its extremity proceeds a slender tail or process, passing through all the rest of the chambers; and it has been supposed by some, that the animal possesses the power of, at pleasure, filling up the chambers or cavities, either with air or water, or of exhausting them of both occasion ally, in order to make itself specifically heavier or lighter, during its navigations; for this animal is also supposed to have a power of sailing, though in a less perfect manner than the argonaut, or paper

nautilus. The animal is also indistinctly allied to the cuttle-fish tribe; having an oval body, with the front or central part fur. nished with a parrot-shaped beak, and surrounded by arms or tentacula; but they differ from those of the sepiæ or cuttles, in being very short, extremely numerous, disposed in several concentric rows or circles, and not beset with any visible suckers. From above the neck, or round the upper part of the head, rises a large, concave flap or hood, beset on the inside with numerous but small suckers, or concave tubercles. By the elevation and expansion of this concave flap, or hood, the animal of the pearly nautilus is supposed to sail. It is of a pale reddish-purple colour, with deeper spots and variegations.

[Shaw.

Ship-Worm.

Teredo Navalis LINN.

This is long a worm, covered with a calcareous shell; the shell is smooth, thin, cylindrical, more or less twisted, rather obtuse at the hip; from four to six inches in length. The same worm is not unfrequently found naked, or destitute of its shell, and is then called Terebella, or naked ship-worm; it has the same habits as the Teredo, and pierces planks nearly as readily. The ship-worm is a native of the Indian Seas, from whence it has been imported into Europe. It penetrates easily into the stoutest oak-plank, and produces dreadful destruction to the ships, by the holes it makes in their sides; and it is to avoid the effects of this insect that vessels require sheathing.

The head of this creature is well prepared by nature for the hard offices which it has to undergo: being coated with a strong armour, and furnished with a mouth like that of the leech, by which it pierces wood as that animal does the skin. A little above this it has two horns, which seem a kind of continuation of the shell; the neck is as strongly provided for the service of the creature as the head, being furnished with several strong muscles; the rest of the body is only covered by a very thin and transparent skin, through which the motion of the intestines is plainly seen by the naked eye; and by means of the microscope several other very remarkable particulars