A Year at the Shore

by Philip Henry Gosse

I have on other occasions noticed the elaborate and wonderful mechanism of the sucker-feet as they appear in the commoner species of the class. I need not therefore repeat those details, but look at a few other particulars in the economy of the animals whose locomotion is dependent on this curious contrivance.

There is a pretty little species abundant enough hereabout, chiefly affecting shores on which numerous angular masses of stone lie irregularly scattered and heaped one on another. Yet they seem to have a predilection, for they do not occur in all our localities even though these conditions be not lacking. Livermead Point, and the south side of Anstey’s Cove, beneath the cliffs, are favourite spots for them, the former especially, where we can find the little Gibbous Starlet,[88] for such is its name, at all times of the year, when the tide is sufficiently out. The retiring tide here leaves a shallow pool of considerable area, which then continues to run out by a narrow channel among the rock boulders, a winding rivulet of salt water; along whose borders, by turning over the loose blocks, scores of this pretty Star are exposed, clinging to the wet sides and roofs of the dark passages by means of their sucker-feet. Forbes has given two figures of the species, but manifestly taken from dead specimens, and from very small ones too. He says, “large specimens measure only an inch across;” from which I infer that on the shores of the Isle of Man, where he was familiar with it, the Starlet does not attain the dimensions it reaches on our mild southern coast. He indeed alludes to one in Mr. Ball’s collection, which measured one inch and five lines in diameter. Specimens, however, of this size are quite common with us, nor would one of an inch and a half be looked upon as at all exceeding the modest and proper range of the species.

Plate 20.
P. H. GOSSE, del. LEIGHTON, BROS.
PURPLE-TIPPED URCHIN. ROSY FEATHER-STAR. STARLET.

ITS EYES.

It is of a pentagonal figure, with the margin a little receding between the angles, but not so as to cause the latter to form distinct arms. The body is flat below, and plump and cushion-like above, of a yellowish olive hue, with the very edge of a golden orange tint, while a spot of the latter colour, a little out of the centre, marks the situation of a remarkable organ called the madreporiform tubercle, the proper use of which has not as yet been satisfactorily determined. Just at the extremity of each angle, but a little below, is situated a wart of rich crimson hue, which is supposed to be an eye, being seated on a small ganglionic swelling of a nerve that passes along the ray. It is true no crystalline lens has as yet been detected on the pigment dot, either in this species or any other (for the specks are found in the same position in all the proper Star-fishes), but they are manifestly of the same character as similar specks in Rotifera, and other humble animal forms, which in some examples are connected with an indubitable lens. It might seem at first as if the situation of these eyes were not very favourable to vision; but, in truth, they command the ground just before and around the ray-tip, and also the water in a horizontal direction; and as there is one at each of the five angles, the entire circumferent space is viewed at each moment. Add to this, that the animal is in the habit of very frequently turning up the tip of one or other of its rays, when the range of vision would take in the zenith; and we shall perceive that no position in any other part of the body could be so suitable for the location of eyes as these selected. It is not to be supposed that distinct definition of objects is attained by these rudimentary organs; but the animal is probably conscious of the difference between light and darkness, and may also discern the sudden approach of any object, either by its interception of light, or by its colours, though its features and form may be indistinct. Such a degree of visual perception, though very imperfect in our esteem, may be of great use to this sluggish creature, and amply sufficient for its need.

The whole upper surface of this Starlet is covered with six-sided convex plates, each of which is crowned by a group of short blunt spines; the number in each group varying from one to nine; four to six, however, most commonly; arranged in a diverging tuft. Over the madreporiform tubercle, the tufts are stouter, and bend towards each other, as if to protect this delicate organ, which, whatever its function, is grooved with sinuous furrows, visible only with a considerable magnifying power, like the rounded masses of coral from the tropical seas, called brain-stones.

On the under surface similar stout short spines are arranged in transverse bands across each ray, interrupted, however, by the central furrow, which is perforated with two ranges of orifices to give issue to the sucker-feet, which thus form a double row. These organs do not differ importantly either in structure, function, or appearance, from those in the Cross-fishes, in the Sea-cucumbers, or in the Urchins.