Beautiful shells

by H. G. Adams

For it’s I that intend to demonstrate,

The creature’s phenomena strange,

Its functions to set every one straight,

And exhibit their structure and range.”

Scarcely will our limited space permit us to do this, but a few of the most remarkable particulars about this common Acephalan, we feel called upon to set before our readers.

First, then, it belongs to the class Conchifera; this is a word which we must stop to examine a little; it seems to come from the Latin concha, which means a shell-fish with two shells, in other words a bivalve mollusk. Second, our Oyster belongs to the class Pectinidæ. Now pecten is the Latin for a comb, and this class includes those bivalve shells whose edges are toothed, or, as it is said, pectinated; in the scallop and the cockle shells this peculiarity is more observable than in those of other members of the class, and these form the typical, or so to speak, pattern genus, pecten. Thirdly, the Common Oyster is a Monomyarian Conchifer. Ah! that’s something like a name for the acephaloid monarch! Look at these two words, mono-myarian, di-myarian, you know of course that mony-syllable means one syllable, and dis-syllable means two. You sometimes hear of a person who leads a monotonous life, and you think perhaps of the Oyster shut up in his shell all alone, one by himself; this notion you now know to be a false one; although it is true that he has but one abductor muscle, and therefore belongs to the division of the Pectinidæ family called Monomyaria, while the Pearl Oyster has two, and therefore belongs to that termed Dimyaria. If, as they say, there is reason in the roasting of eggs, surely there must be in the names given to the classes and divisions of shells. We hope to have succeeded in making the why and the wherefore in this case somewhat plain;—one—two—and away we go out of this maze of hard names. But what about the abductor muscle, above spoken of? well, this must be explained; abduce, coming from the Latin abduco, means to separate, to draw away, hence we have abduction. During the life of an Oyster, the usual and natural state of the shell is that of being kept open for a little distance, to allow the water necessary for its nourishment and respiration to flow in and out; but as a security against danger, it was necessary to furnish the animal with the means of rapidly closing the shell, and retaining the valves in a closed state. These actions being only occasional, yet requiring considerable force, are effected by means of a muscular power, for which purpose one or two, or sometimes more strong muscles are placed between the valves, their fibres passing directly across from the inner surface of one to that of the other, and firmly attached to both, and these are called the abductor muscles, because their office is to draw or pull; how strongly they do this those whose business it is to open Oysters can best tell; if the animal within were not alive, the process would not be a difficult one, as in that case the muscles would be relaxed, and the shell would come open of itself, so that actually people who eat Oysters directly they are opened, swallow them “all alive-O!”

If a pair of the shells from which the delicious morsel has been extracted, be taken in the hand, it may be noticed that one is much thinner, smoother, and flatter than the other; this is the side most exposed to the action of the water; the rougher and rounder side is that which is attached to the rock, or other substance to which the animal forms an attachment, that is usually life-long. The two portions of the shell are joined together by a hinge of curious workmanship, which is formed of the inner layer of the shell, and strengthened by a ligament which is wonderfully elastic; when the shell is drawn together by the abductor muscles, the ligament is at full stretch, and as soon as they relax at all, it contracts, and causes the shell to gape. This process is repeated as often as may be necessary for the safety and sustenance of the animal within, whose mouth is situated at the narrowest part of its habitation, namely, near the joint of the hinge, which connects its upper and under shell. The anatomical structure of the Oyster is more perfect than would be supposed, from its apparently low state of organization; it has a heart, liver, and intestinal canal, and a bag near the mouth, which answers the purpose of a stomach. Its breathing organs are gills, closely resembling those of most other fish; it has little vessels which convey the bile from the stomach to the liver, and may perhaps be subject to bilious attacks, as well as those who swallow this curious piece of organization at a mouthful, without thinking at all of the goodly structure they are demolishing. There is the tiny heart with its series of blood-vessels, just as perfect as in the larger animals. There are the nerves in the shape of minute feelers, which appear to be acutely sensible not only of actual contact with foreign bodies, but also of sounds and movements from without. A very nice sense of feeling appears to reside in what is called the beard, in scientific language bissus; this is a kind of double fringe to the two lobes of the mantle, or sac, as it is called, which envelopes the body of the animal, and floats free from the shell, except just at the part nearer the valve where it is attached.

We have just spoken of the beard of the Oyster, and this reminds us of a conundrum which may serve to amuse our readers, and enliven these dry details a little. Why is an Oyster the most anomalous, that is strange, contradictory, creature in existence? Do you give it up? Well then it is because

“It wears a beard without any chin,

And leaves its bed to be tucked in.”