The Periwinkle's table-manners differ slightly from those of his relations. When he eats, he separates two little fleshy lips, and the glistening, glass-like tongue is seen, or rather the rounded extremity of a bend of it *'Woodward's "Mollusca," 161. E rapidly running round like an endless band in some piece of machinery ; only that the tooth points, as they run by, remind one rather of a watch-wheel. For an instant this appears, then the lips close again, and presently reopen, and the tongue again performs its rasping. It is wonderful to see ;—perhaps not more wonderful than any other of God's great works, never more great than when minutely great; but the action and the instrument, the perfect way in which it works, and the effectiveness with which the vegetation is cleared away before it, all strike the mind with more than usual force, as exhibitions of the skill of the Creator.

As the Periwinkle moves along, mowing his sea-grass as he goes, he carries before him two soft and flexible horns, marked with zebra-like bands of black and white, which he constantly waves about. These are organs of some sense, probably of touch, and are therefore called tentacles (or tryers) ; but they bear on their outer sides, near the base, a pair of other organs, which are more closely analogous to what we ourselves possess. You see on each tentacle a little wart, which, when you look at it with a lens, you perceive to have a round black glossy extremity. This is the eye. By careful dissection under the microscope, Ave find it to contain a beautiful transparent crystalline lens, with a thick and glutinous vitreous humour adhering to it behind, bounded by a retina or curtain to receive the optic image, and an optic nerve.

But much more attractive you will find the eyes in this little Scallop. It is a half-grown individual of what is provincially known as the Squin (Pecten opercidaris), much prized for its delicate flavour. Belonging to the bivalve class of the Mollusca, the animal is inclosed within two shallow shelly plates, concave internally and convex externally, which are united by a hinge, just as the works of a watch are protected by the case. When the little creature is at its ease, as when the water is pure and clear, it lies on one side, its valves being separated as we see them now, a quarter of an inch or so apart allowing us to discern what is contained between them.

Well, we see first a number of slender white pointed threads, peeping out from each valve, and spreading on all sides, waving hither and thither, groping, now contracting, now expanding, with incessant but deliberate motion. These are tentacles. If we trace them to their origin, we find them attached to a fleshy sort of veil that lines each valve to near its edge, and then abruptly falls at an angle towards the opposite valve, where it meets a corresponding veil. These two veils form the mantle. It is from each of these that the tentacles spring ; and we discover that there are four rows of these organs, one row set along the angle, and one along the edge, of each veil.

But as we peer among these slender threads, our attention is riveted by some tiny points that are seated near their bases, which glitter like brilliant gems. They are seen only in those rows of tentacles which spring from the angles of the veils, and not in those which fringe their edges. Even the unassisted sight can detect the gleam and glitter of these little specks ; but it is only when we bring the lens to bear upon them that we see all their beauty. Then they look like diamonds or emeralds, each set in a broad ring of dark red substance, which greatly enhances their beauty. They are inserted into the mantle in the line of the tentacles, alternating with them, yet not with absolute regularity, for there are more tentacles than gem-points ; they are about half as numerous again as the radiating ridges of the shell. Some are much larger and more prominent than others, but they have all the same structure and appearance.

These little organs are eyes. As its movements are far more extensive, and more fitful and rapid than is common in this class of animals, the little Pecten probably needs these brilliant organs of vision to guide its wayward e 2 rovings, as well as to guard it from hostile assaults. The animal is very sensitive, withdrawing its tentacles and mantle, and bringing the valves of its shell together, on. any shock being given to the vessel in which it resides. It manifests, however, a wisely measured degree of caution, for it does not actually close the valves, unless it be repeatedly disturbed, or unless the shock be violent, contenting itself with narrowing the opening to the smallest space appreciable ; yet even then the two rows of gem-like eyes are distinctly visible, peeping out from the almost closed shell, the tw^o appearing like one undulating row from the closeness of their proximity.

If you are familiar with the pin-cushions which children often make with a narrow ribbon round the edges of these very Scallop-shells, you can scarcely fail to be struck with the resemblance borne by the living animal to its homely but useful substitute ; and the beautiful eyes themselves might be readily mistaken for two rows of diamond-headed pins, carefully and ribbon,—the regularly stuck along the two edges of the pin-cushion ribbon itself representing the satiny and painted mantle. A friend of mine, to whom I was once showing this object compared it, not inaptly, to a lady's ring set with diamonds.

You will not fail to remark how the position of these beauteous organs is suited for their most extensive usefulness consistent with their safety. In the ordinary condi tion of the animal's expansion, and especially when it i& about to make its sudden and vigorous leaps, the gemlike points are so situated as just to project beyond the margin of the shell. So that when we view the creature perpendicularly as it lies, our eyes looking down on theconvexity of the upper valve, the minute eyes are seen, all round its circumference, just, and but just, peeping from under its edge. It is clear that this arrangement secures to them the widest range of vision with the least possibleexposure. As Divine contrivance has been often most deservedly recognised in the projection of the bony ridge •over the human eye, which we call the brow, we surely cannot fail to recognise, and admire it also, in the position •of these delicate organs, either beneath the margin of the solid shell, or, if projected, projected only in the smallest •degree, and endowed with the power of retreating beneath its barrier with the rapidity of thought on the least alarm.

There can be no doubt that these points, numerous as they are, are true eyes, endowed with the faculty of vision an a well-developed degree. For when their structure is carefully examined by the skilful anatomist, each is found to be covered with the proper sclerotic* tunic, which •becomes a perfectly transparent cornea in front, and to possess a coloured iris,—perforated with a well-defined pupil, and connected with a layer of pigment which lines ithe choroid tunic,—-a crystalline lens, and a vitreous humour for the due refraction of the rays of light, and a retina in their focus, formed by an expansion of the optic aierve, and fitted to receive the picture ; the sensation of which is then conveyed by an optic nerve from each eye to the common nerve-trunk which runs along the border of the mantle. Thus there exists in each of these lustrous points every element needful for the due performance of vision; though, probably, the impressions thus conveyed may be neither so powerful nor so distinct as those which are conveyed by the eyes of vertebrate animals. They are, however, we may be sure, amply sufficient for the wants of the pretty Scallop, and are fresh proofs of the Divine wisdom and benevolence.

We have been accustomed from childhood to recognise .as eyes the shining black extremities of the upper pair of " horns " in the Garden Snail. And though some natu- * The ball of the eye is composed of three coat* or tunics, the sclerotic, choroid, and retina, and contains three humours, the aqueoits, vitreous, and crystalline. The cornea is the front part of the sclerotic, tthe iris that of the choroid.

ralists have doubted, and even denied, that the tentacle was anything more than a very delicate organ of touch, yet it has been abundantly proved by dissection, and is now incontrovertibly established, that its tip carries an eye, even more completely developed than those of the Pecten which we have just been looking at. The eye is situated, not indeed on the very summit of the tentacle, but on one side of a movable bulb there placed. It is very minute, almost spherical, but slightly flattened in front. It is protected by a very thin transparent layer of the common skin, and is surrounded at the side and behind by a perfectly black membrane, called the choroid, or pigment-membrane. This black globule contains a transparent and semi-fluid substance, with which it is completely filled ; towards the bottom it is of thinner consistence, and appears to contain many brilliant particles when the eye is dissected under the microscope ; this may be considered as the vitreous humour. In the front part of the eye there is a crystalline lens, a small, circular, nattish body, shaped like a lens, perfectly clear and translucent, but a little more solid than the vitreous humour.

Now protection for these so delicate organs is provided in a way quite different from, yet equally effective with, that which we just now admired in the case of the Pecten. You know that if you touch, though ever so tenderly, the eye of the Snail, it is instantly drawn into the horn by a

STRUCTURE OF EYE OF SNAIL.

most curious process of inversion. This action is performed by means of a long muscular ribbon, which origi-

nates from the great muscle that retracts the head within the shell, and which is inserted into the extremity of the hollow tentacle. When this ribbon contracts at the will of the animal, and still more forcibly when it is aided by the contraction of the great head-muscle, the tip of the tentacle with its eye is drawn within the surrounding parts, just like the finger of a glove. When the animal would again protrude its eye, the fibres which surround the tentacle, like so many rings throughout its whole length, successively contract, and thus gradually squeeze out, as it were, the inverted part, until it is turned back to its original position.

But the ears of this homely " creeping thing " are, perhaps, even more curious than its eyes, though far less elaborate in their structure. You will imagine now, that I refer to the other pair of tentacles, as you are accustomed to associate the idea of ears with projecting organs situated on the head. No, you must not look there for them. Here, in this young Garden Slug, which is so small as to be conveniently examined on the stage of the microscope, and so devoid of colour that we can readily look through its tissues,—we shall easily find its ears, though they are not quite so prominent as those of an ass.

I subject the animal to a gentle pressure by means of the compressoriurn,* just sufficient to flatten its soft body a little, without injuring it. And now, with this low power, you may see what Siebold, a learned zoologist and comparative anatomist, familiar with the curious phenomena of life, truly calls " a wonderful spectacle." In the neck of the little animal you discern, deep-seated in the soft flesh, a pair of perfectly transparent globules, or capsules, without any opening, but filled with a clear fluid, in which there are some minute bodies performing the most extra- * An instrument for compressing or flattening an object under the microscope.

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