A Year at the Shore

by Philip Henry Gosse

It is worthy of note that the newly-hatched young from these nests were so unlike the full-grown Stickleback, and so like the common smooth Blenny, that Mr. Couch concluded that there had been some error in his observation, and that the nest truly belonged to the latter fish. Further research, however, proved that the Stickleback was indeed the parent; and the transition from the infantile Blenny-like outline of the face, high, bluff, and almost perpendicular, to the true Stickleback outline, long, slender, pointed, with the far-projecting lower jaw, is something remarkable.

CRABS.

But now the tide has reached its lowest mark; and as we wander over the wet sand at its very verge, our attention is attracted by every tiny object that breaks the uniform level, even at a considerable distance. Some of these are worm-casts thrown up by busy Annelids, working away in the sand to reach a lower and therefore a wetter level, as the upper stratum dries in the sun. But others are Crabs, of two or three species. One of them is the somewhat uncommon and very beautiful Portumnus variegatus, of which a great number are left by the sea, but all of them dead; some of them, however, from their freshness, only recently defunct. The shape of the carapace, or body-shell, is very elegant, and the colours, though sober—a light drab, mottled and pencilled with pale lilac—are pleasing: the hindmost pair of feet terminate in thin swimming-plates, but they are narrow, and exhibit the natatory character in only a subordinate degree.

Other Crabs are alive and active, though, to be sure, in a somewhat sluggish way. Here we catch sight of a slight movement in the wet sand, and, stooping, we perceive a pair of antennæ, much beset with short bristles, projecting from the surface. They wag to and fro, and presently up pushes a shelly head, with its pair of stalked and jointed eyes, and two tremendously long angular arms, furnished with awkward-looking nippers at their extremities. Another effort, and the whole Crab emerges from his sandy burrow, and displays his pale buff-coloured shell, wrinkled across, and armed with sharp spiny points at its front and edges. We easily take him up, for his means of escape are feeble, as he uncouthly shuffles on his short legs over the sand; and his bellicose instincts are not strongly developed, nor, if they were, have those long levers of arms any formidable powers of offence. Latreille gave to the genus the title of Corystes; which signifies a warrior armed for battle, from κόρυς, a helmet, but its inoffensiveness belies the appellation.[62] Pennant had already conferred on the species the name of Cassivelaunus, the ancient British chief immortalized by Cæsar. If you were to ask me why this obscure crab should bear a name so renowned, I can answer only by conjecture. The carapace is marked by wrinkles, which, while in some specimens they suggest nothing, in others, especially old males, bear the strongest and most ludicrous resemblance to the face of an ancient man. I have taken specimens in which the vraisemblance was so perfect as to strike me, and others to whom I showed it, with amazement. Now Pennant, as is well known, had strong sympathies with his British ancestry; and perhaps, by a not extravagant stretch of imagination, his playful fancy saw the features of the grand old Celtic warrior perpetuated on this Crab, which he first met with, too, be it remembered, on the Welsh coast.

Plate 14.
P. H. GOSSE, del. LEIGHTON, BROS.
MASKED CRAB.

USE OF THE ANTENNÆ.

Mr. Couch, in his Cornish Fauna, notices the unusual length of the antennæ. “These organs,” he says, “are of some use beyond their common office of feelers; perhaps, as in some other crustaceans, they assist in the process of excavation; and, when soiled by labour, I have seen the Crab effect their cleaning by alternately bending the joints of their stalks, which stand conveniently angular for this purpose. Each of the long antennæ is thus drawn along the brush that fringes the internal face of the other, until both are cleared of every particle that adhered to them.” This suggested use of the antennæ does not seem to me to be a very felicitous guess of the excellent Cornish naturalist: I should fancy them to be somewhat inefficient instruments in excavation: perhaps I can help him to a better. I have observed that, when these Crabs are kept in an aquarium, they are fond of sitting bolt upright, the antennæ placed close together, and also pointing straight upward from the head. This is, doubtless, the attitude in which the animal sits in its burrow, for the tips of the antennæ may often be seen just projecting from the sand. When the chosen seat has happened to be so close to the glass side of the tank as to bring the antennæ within the range of a pocket lens, I have minutely investigated these organs, without disturbing the old warrior in his meditation. I immediately saw, on each occasion, that a strong current of water was continuously pouring up from the points of the approximate antennæ. Tracing this to its origin, it became evident that it was produced by the rapid vibration of the foot-jaws, drawing in the surrounding water, and pouring it off upwards between the united antennæ, as through a long tube. Then, on examining these organs, I perceived that the form and arrangement of their bristles did indeed constitute each antenna a semi-tube, so that when the pair were brought face to face the tube was complete. It is difficult to make this arrangement intelligible by mere words; but I may say that if either of the antennæ were broken off in the middle and viewed vertically, the bristles would be seen to project from each side of the inner face, in a curved form, each making about a fourth of a circle, so that the two corresponding bristles enclose, with the body of the antenna, a semicircle. Of course, those of the opposite antenna make another semicircle, and, when placed face to face, the points of the bristles just cross each other, and a circle is enclosed. Now, the whole length of the antennæ (about an inch and a half) is closely beset with these bristles, and thus a long row of rings is formed with very narrow interspaces between them; and these rings do in effect constitute a tube quite sufficient to retain the stream of water that is poured through it.

I think then that we may, with an approach to certainty, conclude that the long antennæ are intended to keep a passage open through the sand, from the bottom of the burrow to the superincumbent water, for the purpose of pouring off the waste water, rendered effete by having bathed the gills: and it is one of those exquisite contrivances and appropriations of structure to habit which are so constantly exciting our admiration in the handiwork of the ever blessed God, which cannot be predicated by the à priori reasoner, however astute, but are ever rewarding the research of the patient observer.