The Oyster: Where, How and When to Find, Breed, Cook and Eat It

by Eustace Clare Grenville Murray

The mouth (b) is a kind of trunk, or long aperture surrounded by four lips nearly resembling those of a gill, but far shorter.

Behind the muscles is to be seen a large fleshy white and cylindrical substance moving on a central muscle, and containing the stomach and intestines (i). This part resembles the trunk of other conchæ, but it has no power of opening or contracting. The canal of the intestines is situated on the top of the muscle (a).

The oyster has circular vessels, on the bottom of which are to be seen deep muscular cavities, occupying the place of the heart (h), and sending their moisture to the small skin through which they come in contact with the water or the air.

In his "Outline of the Animal Kingdom," Professor Rymer Jones most happily describes all these peculiarities. "Wonderful indeed is the elaborate mechanism," are his words, "employed to effect the double purpose of renewing the respired fluid and feeding the helpless inhabitants of these shells! Every filament of the branchial fringe, examined under a powerful microscope, is found to be covered with countless cilia in constant vibration, causing, by their united efforts, powerful and rapid currents, which, sweeping over the surface of the gills, hurry towards the mouth whatever floating animalcules, or nutritious particles, may be brought within the limits of their action, and thus bring streams of nutritive molecules to the very aperture through which they are conveyed to the stomach, the lips and labial fringes acting as sentinels to admit or refuse entrance, as the matter may be of a wholesome or pernicious character."

Nature, too, has given the oyster a sensitive perception of the changes of light as the means of its protection from the many enemies it has to contend with; for if the shadow of an approaching boat is thrown forward so as to cover it, it closes the valves of its shell before any undulation of the water can have reached it. This sensitiveness is easily studied in the marine vivary, where the oyster, with its beautiful cilia, more beautiful by far than the richest lace of a bride's wedding dress, is always an object of great interest.

The oyster is an hermaphrodite animal, and hence its propagation is effected by self-produced eggs, which it bears within in the form of a greenish milky juice which it casts as spat in May, and which, as has already been stated, in this country is protected by wise and prudent acts of the Legislature. "The liquor in the lower shell of the oyster," says a writer in No. 587 of the "Family Herald," "if viewed through a microscope, will be found to contain multitudes of small oysters, covered with shells and swimming nimbly about—120 of which extend about an inch! Besides these young oysters, the liquor contains a variety of animalcules." Indeed, with the aid of a microscope one million of young have been discovered in a single oyster. Guarded by their two tender shells, these swim freely in the sea when ejected by the parent oyster, until, by means of a glutinous substance, they fix themselves so fast to some object that they can be separated only by force. These young are very soon able to produce others, many say at four months after their birth. When the oyster attains the size of a crown the shell is still very tender and thin; it is only after the second, third, or fourth year that it becomes fit for human food.

If we cannot answer the Fool's question in Lear, and "tell how an oyster makes his shell," we can, nevertheless, tell by his shell what is his age.

"A London oysterman," says a correspondent of No. 623 of the "Family Herald," "can tell the ages of his flock to a nicety. The age of an oyster is not to be found out by looking into its mouth. It bears its years upon its back. Everybody who has handled an oyster-shell must have observed that it seemed as if composed of successive layers or plates overlapping each other. These are technically termed 'shoots' and each of them marks a year's growth; so that, by counting them, we can determine at a glance the year when the creature came into the world. Up to the time of its maturity, the shoots are regular and successive; but after that time they become irregular, and are piled one over the other, so that the shell becomes more and more thickened and bulky. Judging from the great thickness to which some oyster-shells have attained, this mollusk is capable, if left to its natural changes unmolested, of attaining a great age." Indeed, fossil oysters have been seen, of which each shell was nine inches thick, whence they may be concluded to have been more than 100 years old.

For the most part the offspring remains near the mother, which accounts for the large oyster banks or beds which are found in almost all the seas of the temperate and torrid zones, and which in some places have been known to attain such magnitude as to cause ships to be wrecked upon them. The lower stratum is necessarily lifeless, being pressed upon by the upper one, so that the oysters beneath are unable to open themselves, and are consequently deprived of food.

The immense propagation of the oyster may be understood from the fossil oyster bed near Reading, in Berkshire. These fossils have the entire shape, figure, and are of the same substance as our recent oyster-shells, and yet must have lain there from time immemorial. This bed occupies about six acres, forming a stratum of about two feet in thickness. But the largest fossil oyster banks are those raised by earth-quakes along the western shores of South America, which measure from sixty to eighty feet in depth, are often forty miles in length, and in many places stretch above two miles into the interior.