varieties of those shells, as our companion in this our ramble is well aware. We have the gracefully-formed Venus-shell and chione, the richly-coloured pecten, the spondyli, the tellinæ, the myæ, and a multitude of others, which, although more or less allied to each other, exhibit some interesting specific differences. We can, however, refer only to a few as types of others, and for this purpose shall select some of the most familiar.

It is low-water during a spring-tide. The waves have retreated far beyond their usual limit, and a wide extent of smooth sand is left bare. Let us ascertain whether it will not yield us some objects for our intended illustrations. Furnished with a trowel, we dig a little way beneath the surface. Our labour is at once rewarded: here is a cockle. It will suit our purpose most conveniently. We perceive that the shelly covering of this well-known member of the great family of molluscs consists of two pieces; not, as in the oyster, nearly flat, but almost hemispherical in shape. They are united together by a hinge, the processes of which are firmly attached by means of a ligament of great strength, and yet extremely elastic, so as to act as a kind of spring, on opening the shell, precisely in the manner in which the spring of a watch-case throws open the lid when the power that keeps it close is relaxed. This hinge and its elastic ligament afford a most beautiful illustration of that Divine Wisdom which so accurately adapts the means to the end in the structure even of the humblest creatures. The hinge and ligament differ in form in the different species of bivalves, and their modifications mark out the various genera in the classification of Linnæus. In some, as in the oyster and mussel, the hinge is very simple, consisting of a ligament only; in the gaper or mya there is a single tooth in addition to the ligament; and as we advance from the oyster or mussel toward the arca, the processes of the hinge become more complicated, till in the latter we perceive, in addition to the ligament, a number of tooth-like processes beautifully adapted and fitted to each other. None of these differences are undesigned or unnecessary. They are all intended to furnish a greater or less degree of compactness to the joint, so as to adapt it to the circumstances in which the animal is placed; and were we fully aware of all their peculiarities of habit, mode of life,

exposure to greater or less danger from pressure or other causes, we should find that in every instance those differences are expressly designed by the Great Author of nature for a particular end. But to return to our cockle.

On opening the valves, we perceive that the whole of the inner surface of the shell is lined with a soft membrane, which encloses the body of the animal as in a cloak, and is therefore called the mantle. It is found in all the varieties of molluscs, and, although subject to great modifications, is a most essential part of their structure. Among the marvels of creative power, perhaps there is not one more marvellous than the office which this apparently simple membrane performs. Strange to say, it is a piece of mechanism for the formation of the shell by which the mollusc is covered. It is, in fact, a chemical apparatus, simple in the extreme, so far as mere appearances are concerned, and yet utterly inimitable by the highest efforts of human ingenuity. This wonderful membrane is furnished with a series of most admirably - constructed glands, which secrete carbonate of lime for the substance of the shell, and colouring matter for its adornment. The glands at the margin of the mantle are occupied in adding continually to the edge of the shell, as its occupant increases in size, while the inner surface of the mantle adds to the thickness of the shell, depositing that beautifully-smooth pearly substance so reinarkable in its interior surface. Thus, for example, the fine mother-of-pearl on the inside of the oyster-shell, and the beautiful colours, of yellow, blue, pink, green, brown, red, crimson, and violet, which ornament and diversify the outside of others, are all the work of the mantle ! What the peculiarity of structure in the glands of this marvellous organ may be, by which the carbonate of lime is first secreted and then applied to its purpose; in what manner the colouring matter is elaborated; from what materials it is cbtained, and what is its chemical composition-these and many similar questions are such as to demand for their solution the highest exercise of human skill; but in many instances they are so intricate as to demand it in vain.

Within the mantle thus lining the cockle-shell is the body of the animal, consisting of a firm muscular substance, in which are the stomach, the liver, and other viscera. But what most attracts

our attention is a peculiar organ tipped with a fine yellow colour. This is the creature's foot, and is a highly organised implement, possessed, in common with the cockle, by other species of bivalves, but in some existing only in a rudimentary condition. This foot is an organ of locomotion; by means of it the cockle not only buries itself rapidly beneath the sand, but by protruding it suddenly is able to move in jerks along its surface.

If we turn from the cockle to the common scallop (pecten), we shall discover some modifications in the structure of the bivalves that are highly interesting. There is of course the usual mantle requisite to the growth or enlargement of the shell, and within it the body of the mollusc, which presents a general resemblance to those of other bivalves, but with certain remarkable peculiarities. The mantle is of a delicate flesh colour, instead of being, as in the cockle, of a pale yellow; around its margin are numerous semipellucid thread-like appendages, which the animal can protrude or retract at will: these are its tentacula. They are extremely delicate; yet are they not only furnished with muscles by which they can be moved in all directions, and protruded from the shell or retracted at the will of the animal, but supplied with a system of nerves, distributed over their surfaces, so as to suit them to their office as organs of touch. But what is most remarkable in the structure of the mantle is, that along its margin is a row of singularlybrilliant eyes, so placed that each eye is able to look out into the watery world around through one of the grooves in the fluted shell. These eyes are about half as many in number as the grooves themselves. In the full-grown scallop, each eye is about half as large in circumference as the head of a small pin; but, small as they are, they are, as already mentioned, remarkably brilliant, exhibiting, without any hyperbole, the lustre of minute diamonds surrounded with a dark rim or setting. This supply of organs of vision is altogether singular; for why should the pecten be furnished with so many, and these apparently so perfect, while the majority of its congeners are destitute of them? For this it is scarcely possible to furnish a reason; and yet that there exists some special necessity for these bright little optics is certain; for the All-wise Creator does nothing in vain-confers no faculty without its purpose. But what

can the purpose be in this particular instance? To what use does our pecten apply his numerous shining eyes? Is he a sage among the molluscs, occupied in calmly contemplating the manners of bivalves in general, in order to establish some favourite hypothesis of a shell-fish philosophy? Is he a censor in the subaqueous realms, noting with Argus-like power the conduct of his passionless brethren of the deep, that he may ascertain how they comport themselves under various trying circumstances? Or have his organs of vision reference merely to his own personal affairs? Do they only aid him to choose the viands on which he is to dine, or to admire the variegated coat and beaming eyes of his mate? The truth is, we know not wherefore the distinction should be; but how great soever our difficulty may be, of this we may be assured, that a final cause does exist, and that for some specific end the scallop has been thus rendered superior to his friends the cockle and the oyster. It is but right to state, however, that some naturalists have doubted whether these diamond-like points were really organs of sight, or only an apparatus designed for unknown and inexplicable uses; but we gladly confess that such doubts we entirely repudiate, not only because those points so much resemble eyes, even when viewed with the unassisted vision, but because we have examined them with a powerful microscope, and found that each eye consists of a lens surrounded by a vitreous covering, and otherwise exhibiting too close a resemblance to an organ of vision to be supposed suited to any other less important or less obvious use, and because their position, too, conjoined with their structure, is such as to dispel all reasonable doubt upon the subject.

Wandering along the sea-shore recently, we arrived at a place where some rocks jutted into the water, but which were now left bare, the tide having receded. These rocks were thickly covered with tangle, so as to afford at their bases an appropriate retreat to several of those creatures whose structure and habits enable them to endure without injury the absence of their usual element. We immediately proceeded to explore the spot. Lifting up the overhanging fronds of the sea-ware, we discovered, greatly to our surprise, at the base of a huge stone, but completely sheltered beneath the thick covering of the Algo, a singular congregation

of star-fishes, not one of which we could discover near any other of the stones. We counted more than forty of them, and among them a small egg-urchin. The stars were of various sizes-one or two not more than an inch and a-half in diameter, others four or five inches. We naturally felt some curiosity to discover for what purpose our Asteriado had held a meeting so numerously attended, and one so obviously important, that not one of the family, even of the youngest of them, resident in the vicinity was absent. We searched with care, lifting up all the sea-weed, when, lo! to our great delight, we discovered not only the cause, but at the same time a fact, as regarded the food of the star-fish, of which we were not previously aware. At the base of the stone, but almost hidden beneath the overhanging edge of it, was an unfortunate jelly-fish; not the large brown stinging species, from which our fingers have often smarted for hours, but one of those without tentacula, transparent, and with six circular purple rings on the centre of its umbrella. Unhappy Pulmonigrade!' said we, addressing the motionless gelatine, 'thou shalt no more wander on thy devious voyage through the bright sea waves! thy frail bark is fairly shipwrecked on these inhospitable rocks! Why didst thou not shun the shore, and steer thyself off with the ebbing waters, where, amidst the deep sea, thou mightest roll about, up and down, and from side to side, as thou wert wont? But time and tide, which wait neither for men nor medusæ, have so willed it, and here thou art, an unresisting prey to a host of star-fishes! Poor little mariner! many a bark as fair as thou, and sailing as gallantly among the billows of the deep sea, hath like thee been stranded on the shores of life; and many, alas! like thee, ere the tide again arose to float them on their way, have utterly perished beneath a host of fears, and griefs, and disappointments, and toils those curæ volantes which, the poet tells us, not only flit about the golden beams of the palace, but pursue the steed and his rider, and scale the sides of the ship in her most rapid course!' The truth is, our jelly-fish must have got himself entangled among the tangle, and so became the spolia opima of his foes. The star-fishes, although the tide had left them, were busy with their dinner; there was not one of them who had not a large

piece of the medusa at his mouth, and one of them actually swallowed a considerable slice while in our hands. Heartily did we wish that our readers were congregated around us at the propitious moment, like the corona of the old philosophers; we should incontinently have converted the rock by which we stood into a professor's chair, or, as we may say, a philosopher's stone, and delivered a lecture on the spot, doubtless to the great delight as well as edification of our disciples. As, however, we are not thus favoured, we shall imagine ourselves accompanied by the reader, and say a word or two as to the urchin and star-fish.

The egg-urchin belongs to the family of Echinida, a race whose pedigree extends far into the ages of hoar antiquity, having existed thousands of years before man became a denizen of this terraqueous globe. The species now existing, indeed, are not found in a fossil state, save in very recent deposits; but their ancestors flourished in prodigious multitudes during the secondary epoch and the tertiary, and are found imbedded in the oolite and chalk formations; some shaped like helmets, some elliptical in form, some turbinated, and others heart-shaped, like those of the present day. The urchin is therefore an object of interest to the geologist as well as to the student of natural history. The egg-urchin (Echinus sphæra) is doubtless familiar to our readers. The shell is globular, but somewhat depressed, so that the diameter perpendicular to the orifice in the shell is less than that at right angles to such diameter-that is, from one side of the sphere to the other. If we in the first instance examine the shell, we shall find it in the highest degree worthy of admiration. Unlike the crab or the lobster, the urchin does not cast its shell; it is therefore obvious, that for the animal to escape from its hard envelope by the narrow orifice in it would be impossible. The shell, therefore, is made to increase with the size of the wearer, and this necessity gives origin to a wonderfully complex as well as beautiful arrangement. It is plain, that were the panoply to consist all of one piece, its diameter could not increase; but the difficulty is admirably provided for. The sphere consists of hundreds of minute segments of a pentagonal shape, fitted to each other like the stones of an arch or a dome. The whole of the interior is lined with a delicate membrane, which likewise