bed is rich the diver often collects 150 oysters at one dip, but sometimes not more than five.' It is said that a single diver will, in one day, often bring up from 1000 to 4000 oysters.

From the simple circumstance that Providence has instructed this animal, which cannot eject from its shell those substances, whether formed within itself, or that have accidentally entered, to encase them in the precious substance which it is empowered to secrete, what a vast fund of ornament to deck the most lovely part of the creation, and having no parallel in any gem that the earth produces, is provided. The pearls obtained from other shell-fish vary in colour-those from the wing-shell are brown, and those from the fresh-water muscles greenish, but sometimes they are yellow, pink, bluish, and some are even black; these last are very rare and dear.

Other bivalves fix themselves by a tendinous ligament to the rocks. In one genus, in the upper valve near the hinge, is an aperture, closed by a kind of operculum formed at the dilated extremity of an internal muscle, it is by this operculum that the animal fixes itself. In another, related to the last,' the beak of the lower valve turns up, overhanging in some degree the upper valve; in this beak is a notch or aperAnomia, PL. V. FIG. 2, 3.

'Malte-Brun, Geogr. iii. 225. 3 Terebratula, PL. V. FIG. 4.

2

ture through which the fixing tendon passes; affording an admirable instance of variation in the means of attaining the same end, when circumstances require it. It was necessary that the valves should not be reversed, a tendon through the lower valve secures this in the first of these animals; but in the second, where the overhanging beak would interfere with this purpose, the tendon issues from the beak itself, so as to enable the animal still to fix itself with the proper valve downwards. In the Anomia the valve takes the form of the substance it is fixed to.

Who would think that these headless animals, unprovided with organs that indicate any of the higher senses, as sight, smell, and hearing, and apparently fitted with no other means of motion than those of opening and shutting the valves of their shells, or travelling very slowly for a few inches, should yet be able not only to leap and use other motions, but occasionally to sail gaily on the surface of the ocean; but, however improbable this may seem, it has been proved to be the case by the evidence of eyewitnesses of the fact.

The common cockle,' Poli says, can not only, by means of its foot turn round, or to either side, but even take a good leap. The Trigons,2

1 Cardium edule.

2 Trigonia.

nearly related to the cockle, are mostly fossils but there is one recent species, found on the coast of New Holland, called originally, from the pearly lustre of the inside of its shells, the pearl trigon,' a name changed, without reason, by Lamarck. This, which was originally taken by Lesueur and since by Capt. King, was more recently brought from thence by Mr. Setchbury, who told me, that they would leap over the gunwhale of a boat in which he was, to the height of above four inches. The foot of this animal is bent at an acute angle, so, as upon pressure, to form a very elastic organ,2 and that of the cockle is nearly the same.

Those elegant shells the Pectens, or combshells, have long been celebrated for their motions. Pliny says, probably meaning these shells, that they leap and flutter out of the water, and dive. D'Argenville relates, that when they are on shore, they regain the water by opening the valves of their shells as wide as they can and then shutting them briskly, by which they acquire sufficient elasticity to rise three or four inches, and thus proceed till they accomplish their object. Most probably the foot assists in producing these leaps. Their progression in the water is described as very different; when they rise to the surface-but the

T. margaritacea.

PLATE V. FIG. 5.

means by which they do this has not been clearly explained-they support themselves half under water. They next open their shells, to which they communicate such a vibration, that they acquire a very brisk movement from right to left, which enables them, as it were, to run upon the water.

The tulip-shell,' when it walks, if I may so speak, opens and shuts its valves, and at the same time lengthens and shortens its foot, which seems to indicate a connection, or action, between the former and the latter organs, similar to what has been observed to take place in insects, and perhaps points out some analogy between the valves of the shell and the upper wings, or elytra of insects, and the mantle and their under wings.

Bosc states, that the animals of the genus Venus, in calm weather, may be seen sailing on the surface of the waters, using one of their valves as a boat and the other as a sail. As these are usually rather heavy shells, they must be furnished with some means of rendering themselves lighter than the water. Pliny, of old, mentions shells dedicated to Venus, which sail and oppose their concave part to the wind.

Thus we see the Creator has given even to these apparently stupid and inactive creatures means of enjoyment, that every one is not aware

1 Tellina.

of; and powers of locomotion, of which, at first sight, they seem incapable.

I might enlarge here on the admirable contrivance and variety observable in the hinge, as it is called, by means of which the animals are enabled to open and shut the valves of their shells; upon the sculpture and colours that distinguish many of them, particularly amongst the unimusculars, but this chapter is already too long, and enough has been said to prove that they have in no respect been neglected or overlooked by the Almighty Being who willed their existence, and who is ever watchful over the creatures of his hand, to provide them with all things necessary for their being, consistently with the ends he created them to serve.

CHAPTER IX.

Functions and Instincts. Univalve Molluscans.

THE Univalve shells of the Swedish naturalist, a term adopted from Aristotle's Monothyra, are next to be considered; these, with the multivalve Chitons, form the Gastropods, or shell-fish using their belly for a leg, of Cuvier; and with the