« НазадПродовжити »
number and direction to the bands observable in the shell itself; the colouring matter appearing to be here disposed, ready for its deposition with the other substances of the shell. But in the olives and the porcellaneous shells the colours are disposed in two layers, the outer of which is the production of an organization different from that of any of the other inhabitants of shells, and from which proceeds an operation also different from what occurs in any other instance. The highly ornamented surface of these shells is formed at two different periods, and by two different processes. The first appears to be that deposition which takes place from the surface of the body of the animal, and in which but little takes place different from what occurs in shells in general. But as the age of the animal advances, this surface is covered by another; the primitive colours disappear, others are disposed over them, and the substance itself of the shell becomes considerably thickened. This process is performed by a simple but most curious organization. Two soft membraneous flaps, or winged processes, pass out of the opening of the shell, turn back on the external convex surface, and cover it so completely as not to leave the least portion to be seen at the line where they meet each other, on the back of the shell. From the superior sarface of these membraneous bodies, that surface which clings to the convex part of the shell exudes that secretion by which the shell is increased in bulk, and a new arrangement of the beautiful colours of its drapery is effected. Brugutere ascertained this formation of a second surface by actual observation at Madagascar; and the fact derives additional proof from the pale line which passes frequently along the back of these shells, marking the part where the edges of the membraneous wings met. Still more positive proof is rendered by rubbing down the second coat, when the markings of the first coat will make their appearance.
· Although the colours are thus disposed by the animal, the action of light appears to have a material effect in augmenting their brilliancy; climate also occasions considerable differences in this respect; hence the shells obtained from the torrid zones are much more rich in their colouring than those which are found in the more temperate zones. But notwithstanding the circumstance just noticed, there is great reason for attributing the high degree of colouring in shells more to the effects of light than to the heat of the climate. It is not the colouring only of the second coat of the porcellaneous shells which is given by this second operation; the several asperities observable in various shells, as in the cyprea tuberculosa, and in the c. pediculus, are superadded at the same period.
On Taking and Preserving
! On taking a shell, the most expeditious method of depriving the animal of life, is to immerse it in spirit of wine: this being effected, the shell, with its contents, may be placed in hot water for some time, by which the body of the animal will become firm, and may easily be removed with any sharp instrument. Care should be taken that the whole of the animal be extracted, as, if any parts be left within the shell, on their becoming putrid, they often give out a stain which is injurious to the markings of the shells. If any difficulty be experienced in removing the whole of the body, burying the shell for some hours in an ant-hill will generally answer the purpose most effectually, as these little animals will consume every fleshy particle.
Of multivalve and bivalve shells, the different parts of the shell should all be carefully preserved; in these no difficulty will arise in removing the in
habitant, as almost instantly the animal is dead the shells open, and their contents are easily extracted. The greatest attention should be observed not to injure either the hinge or teeth, as, from the structure of these parts, the generic characters are principally founded; care should likewise be taken to preserve apy beard or silky threads that may be attached, as these will often assist in making out the species.'
In the brief sketch we have given of the habits of edeh genus, their haunts are mostly alluded to: some are only to be obtained accidentally, when detached from rocks situated beneath the depths of the ocean; others are found in rocky currents, or in shallows of four or five fathoms depth ; many resort to the sands or mud on the beach, beneath the surface of which they retiré as the water recedes; and numerous kinds may be found attached to sub-marine rocks. Most kinds are but of little worth, after being exposed on the beach to the sun and air; so that, to have them in perfection, they should, if practicable, be obtained with their inhabitant alive. A trawling or dredge net, such as in common use with fishermen, will be found very useful, as by it many kinds can be obtained from deep water, which would otherwise only come accidentally to shore.
Many valuable shells may be found on the beach after violent storms, being removed or separated from their native beds by the agitations of the water: some kinds may be found affixed to the bottoms of ships that have been long stationed in warm climates, as also the stocks of anchors, cables, &c.
On obtaining any species containing the living animal, the particular genus to which the animal belongs should be noted, with its peculiarities of structure, as likewise whether frequenting deep waters or shallows; if affixed to other substances, or detached, if it retires beneath the sand or slime of the beach at low water, and such particulars; if, as the animal advances in age, any and what
the partie noted, wer frequen substances time
advamater, and the samstances wa.
changes take place in the appearance or structure of its dwelling; if it be used as food, or afford any dye; and if the shell or shells be convertible to domestic or other purposes. · River shells, though not of such brilliant colours, often possess much interest: their localities are of the same kind as the marine species, and the same means are required to obtain them. Their substance is usually thin, and they are very brittle.
Land shells are frequently of very beautiful co- lours, and are held in great estimation; they frequent
moist mossy banks, shady lanes, and some of the kinds are only found on chalky situations. The terrestrial shells, or rather their inhabitants, have the property of resisting the action of boiling water for a considerable length of time, without receiving any material injury; so that the quickest mode of destroying the animals is by plunging them into spirit, either of wine or turpentine: the substance of land shells is thin, and they are mostly brittle..
When the shells are clean, dry, and their contents completely removed, they should be wrapped separately in paper, and may then be packed in a box, with a quantity of sawdust, bran, or fine sand, so that all the interstices between the shells be filled up to prevent their rubbing one against the other; besides this precaution, they require no other care'.
On Polishing Shells.
Amateurs are seldom contented with the simplicity of nature. Vitiated in their taste by a fashion which abides by no rules, they attempt to improve even her most elegant productions, and delight to exhibit in their cabinets some of the efforts of their art. As such are in search of innocent amusement, we mean not to dispute the propriety of their conduct, but
· Graves's Naturalist's Pocket Book, p. 272.
rather shortly to mention, for their edification, the method generally in use to improve the beauty of testaceous objects Many shells, it is true, naturally possess so fine a polish, that no preparation is considered necessary before placing them in the cabinet. Such are the cypreæ, olivæ, and the greater number of what are termed porcellaneous shells. In general, however, it happens that, when shells become dry, they lose much of their natural lustre. This may be very easily restored, by washing them with a little water in which a small portion of gum arabic has been dissolved, or with the white of an egg. This is the simplest of those processes which are employed, and is used not only by the mere collector, but by the scientific Conchologist. There are many shells of a very plain appearance, on the outside, by reason of a dull epidermis or skin with which they are covered: this is removed by soaking the shell in warm water, and then rubbing it off with a brush. When the epidermis is thick, it is necessary to mix with the water a small portion of nitric acid, which, by dissolving a part of the shell, destroys the cohesion of the epidermis. This last agent must be employed with great caution, as it removes the lustre from all the parts exposed to its influence. The new surface must be polished with leather, assisted by tripoli. But, in many cases, even these methods are ineffectual, and the file and the pumice-stone must be resorted to, in order to rub off the coarse external layers, that the concealed beauties may be disclosed. Much address and experience are necessary in the successful employment of this last process. But it must be confessed that the reward is often great. When thus prepared, even the common muscle is most beautiful.