A Year at the Shore

by Philip Henry Gosse

Immediately behind each of these head-tentacles you see a little wart, which has a black bead set as it were in its substance. You have often, doubtless, observed the similar black points that are placed at the tips of the upper pair of the horns (tentacles) of the common garden snail; and I daresay, when a child, you have amused yourself by touching them, and noticing how instantaneously the sensitive creature would roll them in, so to speak, concealing them far in the interior of the inturned horns. And every child is taught that these black spots are the snail’s eyes; and so, indeed, they are; and these spots on our Top’s warts are its eyes too, notwithstanding that some learned naturalists, apparently from the mere love of paradox, have affected to doubt the fact that such is their function. If you could dissect out one of these points, and submit it to careful examination with a good microscope, you would find all the parts essential to an organ of vision; there is a sclerotic coat, a distinct little pupil and iris, a cornea in front, and a dark pigment layer within, with vitreous and aqueous humours, and even a crystalline lens for the condensation of the rays of light. Minute these parts are, to be sure, but not less exquisitely finished for that. Indeed, the more skill they require in the demonstrator, the more they reflect the inimitable skill of the Creator. Swammerdam, the Dutch physiologist, who so beautifully showed the structure of the snail’s eye, seems to have feared the doubts of his conclusions that would ensue from the difficulty of repeating his investigations. “But who will credit this?” he says; “for does it not seem impossible that on a point not larger than the nib of the pen with which I write, such exquisite art and so many miracles should be displayed?”

SPIRAL SHELLS.

Now, leaving the animal, though we might devote a few moments to the admiration of its rich colours, adorned as is its deep yellow hue with lines and clouds of deeper brown, let us look at the shell, the solid house of stone, which our friend Trochus has himself built up to cover his head in the hour of danger. How well has he combined the utile cum dulci!—the comfortable with the ornamental! Its general form is that of a cone of much regularity, but with an oblique base, and perhaps you may be surprised to learn that this conical form is but the result of the winding of a very long cone upon itself in a spire. But if you examine a dead shell with care, you will see that it is so. Supposing you had a very long and slender hollow cone of plastic material, and, beginning with the acute point, you twined the whole upon itself, descending in a spiral form, you would have the representation of a turbinate shell, which, by a little gentle pressure of the fingers, might be moulded, without at all losing its essential character, into the exact shape of our Trochus, in which the progress of the spire can without difficulty be followed as well by slight inequalities of surface as by the arrangement of the colours.

It is one of our showy shells. This specimen before us has for its ground colour a chaste, cool grey, occasionally varied with tints of reddish buff, but most conspicuously adorned with a series of large and regular spots of purplish crimson running along the lower angle of the spire from the base to the summit. Each of these spots passes off into an oblique line above, the repetition of which augments the beauty of the pattern.

The interior of the shell has a glory of quite another character. It is covered with a coat of nacre or pearl, of exceedingly brilliant and rich lustre, and the presence of this inward pearliness is quite characteristic of this genus, and of most of the others belonging to the same family, the Turbinidæ. Many of the fine large tropical species are specially conspicuous for this adornment, as I have seen in those that lie along the dazzling beach of coral-sand in lovely Jamaica. The pearl of these shells is used in the arts. De Montfort mentions a necklace which he had seen, that was made out of the nacred part of the shell of the Turbo smaragdus, and which was much more brilliant and beautiful than any of the finest orient pearls.[3] And Chenu observes:—“Les grandes espèces fournissent une fort belle nacre, employée pour les ouvrages de marqueterie. Quelques espèces ont reçu des noms sous lesquels les marchands les distinguent: il y a le Burgau ou Nacré; la Veuve Perlée, dont les tubercles extérieurs usés ressemblent à des perles; la Bouche-d’Or, dont la nacre est d’un beau jaune doré; la Bouche-d’Argent; le Perroquet, ou Turbo Impérial,” etc.[4]

At another time we may examine the structure of shell, and inquire by what instruments and with what materials the ingenious animal contrives to construct so strong and so elegant a dwelling. For the present, however, as the month is January, we shall, if we sit still longer, run the risk of “catching a cold,” if we catch nothing else, though the wind is in the south, and the temperature is so mild for the season.

THE DOG-WHELK.

Therefore, we will move about and pursue our researches among the rocks and under the loose stones. Well, we are rewarded with other specimens: here are several neat little shells, with a lengthened spire, and with a remarkably thickened lip. This is the little Thick-lipped Dog-whelk,[5] a very common mollusk with us under such stones as these at low water-mark. And here is another species of the same genus, the Netted Dog-whelk,[6] which is a much larger shell, being nearly twice as long as the former, and marked with close transverse furrows, which, crossing the longitudinal ribs at right angles, give a peculiar reticulate surface, on which the specific name is founded.

Comparing these shells with the Trochus, we see that they have a deep notch cut in the front part, of which no sign appears in the latter; and this mark, trivial as it may seem, is an important indication of the habits of the animal. The inhabitants of all shells which have this notch are carnivorous, while those with simple lips are herbivorous. The Trochus gnaws or rather rasps away the tender growth of marine vegetation, or the fronds of the grown Algæ, with its remarkable palate-ribbon, all studded with reversed points, of which I may find another opportunity to speak. The Dog-whelk, on the other hand, acts the part of a cannibal ogre, feeding on his simpler brethren of the bivalve shells; storming their stony castles, in which they seem so secure, by open violence.