A Year at the Shore

by Philip Henry Gosse

But this is not all. Again, look at the living Sea-Urchin. It bristles with the rosy-tipped spines, which have a satiny lustre, owing to the reflection of the light from the delicate ridges and furrows with which the whole is fluted, like an Ionic column in miniature. How they are all moving, and swaying to and fro on their bases, quite independently of each other, however, making circles and traverses in the water with their points, as the mast-heads of a ship do among the clouds in a gentle swell, when seen from the deck. Professor Agassiz fell into the egregious blunder of supposing that the spines were the organs of locomotion in the Urchins, denying, with much contempt, the theory which attributed this office to the suckers. One can only wonder whether he ever saw a living Urchin in motion, as one moment’s glance at the phenomenon is sufficient to prove how utterly his theory was false, as Forbes has well shown.

However, let us once more observe the empty denuded box from the cabinet; and now on the exterior. Between the principal bands of pores (called ambulacra, from their fancied resemblance to walks in a garden), as also between the two series which constitute each band, the space is studded with hemispherical warts, of very diverse size, which look as if turned in ivory, unpolished; and each wart is crowned with a smaller wart of like material, but bearing the most perfect polish.

At the bottom of each spine there is a cavity exactly fitting this second wart, and equally highly-polished in its interior. During life the spine was seated on the wart, not united to it, but moving upon it in all directions, with perfect smoothness and freedom; a ball and socket joint, in fact. It was held in its place by an investment of muscle, which completely enclosed both the wart and the base of the spine, having one insertion in the unpolished wart, and the other in a remarkable ring or shoulder of the spine, visible just above the socket.

These are but two or three salient points of interest in the structure of this little unvalued, disregarded creature. I could relate much more; indeed, I think it would not be difficult to write a bulky volume of the history and biography of a single Sea-Urchin, of which every page would display the glory of God. But I have not space for that here.

We sometimes, but very rarely, find on this coast a very lovely form of this class of animals, the Rosy Feather-star.[90] It consists of ten long attenuated arms, radiating from a common centre, composed each of about forty slender joints of stone, and each joint carrying a pair of diverging beards, also many-jointed, all of which together, by their number and arrangement, give to the arm the aspect of a beautiful feather. Around the central point of radiation, a small cup-like body gives origin to the arms, which are double, a pair springing from a single basal joint. Within the cup the soft parts of the animal are chiefly located, the organs of the vital functions; and from the convex surface spring a number of jointed stony threads, like necklaces, much shorter and slenderer than the arms, which serve as claspers, gripping and holding firmly the projections of the rock, by means of strong curved claws with which they are terminated, in shape like those of an eagle.

The whole elegant creature is of a lively rose tint, interrupted by patches of bright yellow, disposed with no regularity or apparent order; the whole, both the yellow and the rosy portions, studded with crimson dots. Edward Forbes, if I rightly understand him, considers these dots to be ovaries, which he estimates at upwards of 57,000 in number.

INFANT FEATHER-STAR.

In infancy the Feather-star is seated at the extremity of a long slender jointed stalk, attached at its lower end, whence it rises erect, like a plant. Indeed the whole animal, in this condition, with its cup-like base and elegantly incurving arms, seated on its tall stem, has so close a resemblance of outline to a flower, that the fossil specimens, which are very numerous, and of large size, are known as Lily-stones, and technically as Encrinites, which word has the same allusion. After a while, the radiating portion, or flower, separates from the stalk, and swims freely, contracting its arms to give the impulse, in the manner of a Medusa.

Who, on looking at these two creatures side by side,—the Sea-Urchin and the Encrinite,—would imagine that they possessed any close natural relationship, or would suspect that they could have been framed on the same model? Yet it is really so; there is a common plan of structure in both; pervading, too, many intermediate forms, which at first sight would seem to manifest as little resemblance to the one as to the other. It would, in fact, be easy to select from any well-furnished museum a continuous chain of specimens, whose links approach each other so closely as to form an unbroken series from the Urchin to the Feather-star.

CONNECTING LINKS.