Nay; after all, it is what it is; and those comparisons just help one who has never seen it, to form some conception of its appearance; but by one who has, all will be rejected as inadequate.
And as to what the brilliant organ is going to do, that we see. For the long taper foot being thrust to its utmost, feels about for some resisting surface, that stone, half buried in the sand, for instance; which no sooner does it feel than the hooked point is pressed stiffly against it, the whole foot by muscular contraction is made suddenly rigid, and the entire creature,--mantle, siphons, foot, shell and all--is jerked away in an uncouth manner, “quite permiscous,” as the fisherman hard-by says, to a distance of some foot or more. But the cockle can leap on occasion much more vigorously; one has been seen to throw itself clear over the gunwale of a boat when laid on the bottom-boards.
Thus we see one use of the hooked tip is to afford a stronger spring; but it has a more direct bearing on the burrowing habits of the animal. Like all the rest of its beautiful tribe, this species is a dweller in the deep sand, into which it can penetrate with considerable power and rapidity. In order to do this, the foot is straightened, and the sharp point is thrust perpendicularly down into the wet sand. The muscular force exerted is sufficient to penetrate the soft sand to the whole length, when the point is suddenly bent sidewise, thus obtaining a strong holdfast. The whole organ is now strongly contracted in length, and the animal and shell are dragged forcibly to the mouth of the burrow, the edges of the valves downward and piercing the sand a little way. The straightened point is then pushed an inch or two farther down; again hooked, and another pull is made. The shell descends a little farther into the yielding sand, and the same interchange of processes goes on till the animal is sufficiently buried. To read this description you would suppose it a most clumsy, and ineffective, and slow business; but indeed this is very far from its character. The elongations and contractions are made with great rapidity; and almost with the quickness of thought the unwieldy cockle, when in full vigour and thoroughly alarmed, disappears into his sandy fortress; so fast, indeed, that you must be very alert to overtake him and prevent his descent, if you have no appliances but your two hands.