To naturalists it will introduce itself under the name of Echinoids; to the laymen as sea-urchin or sea-hedgehog, related to the crinoids, star-fishes, and sea-cucumbers, and representing with them the Echinodermata—one of the most distinct types of the animal kingdom.
An animal is this seemingly unmovable ball, although it is difficult to associate it with what is generally implied by that name.
For a closer examination, of course, it is necessary to remove the spines with which it is covered. There are about 4000 of them on every specimen, each one movable at the will of the owner, and difficult to dislodge from the flesh of the hand, so that a little caution is required in dealing with them. You will thus have accomplished a good hour's work, but will not yet have reached the animal proper, for its upper parts are further protected by a kind of shell—the armor of the sea-urchin. This shell is well worthy of a closer examination. It is formed of a number of separate plates, fitted together, one by one, like the steel plates protecting our men-of-war.
On a full-grown specimen there are about 300 of them. They grow in number and size with the age of the sea-urchin, without alteration of the general shape of the shell, since fresh deposits of the calcareous matter that constitute it are made upon the interior edges of each plate.
Sea-urchins are not sociable creatures. They prefer solitude to company, and rarely more than one occupies one dwelling. In earliest infancy they dig for themselves a home in the quiet surf or in the sand, where the retreating tides leave enough moisture to make them comfortable. There they live and prosper, enlarging their homes as their increased growth makes them uncomfortable, and mostly without enlarging the entrances themselves.
In this manner can be explained the fact of some large specimens having been found in dwellings with entrances through which it does not seem possible that they could pass.
Sea-urchins may not be very palatable, yet they are edible, and in some countries are extensively consumed by the poorer population, eaten boiled in the shell like an egg. In certain coast towns of Italy they even form quite an article of commerce with the more interior country, and accordingly large is the number of those engaged in the pursuit of collecting and diving for sea-urchins. This method of diving is very picturesque and amusing, and, as may be imagined, requires some skill.
More simple is the way the Chinese proceed about it. There the fisherman provides himself with a bundle of slender wooden rods, tapered to a little round knob at one end. With these he proceeds to the surf at low tide, and drops one of these rods into each burrow where he suspects a tenant. There it is left for about twelve hours. During this time the sea-urchin is sure to swallow the button, and as the elastic tissues contract, it is unable to release itself again, so that when the fisherman returns he can easily extract the rod with the victim attached. Palates differ with localities. So do the Chinese stew the sea-urchins like a turtle soup.
Of the rest of the family of the Echinodermata, the crinoids and sea-cucumbers have many interesting characteristics; yet especially worthy of mention is the star-fish.
You all know that clammy mass that dangles so hopelessly from the hand. Innocent as it looks, it is quite fierce company to the mollusks and even larger inhabitants of the sea, upon which it feeds. Destitute of any jaws or levers, and with the mouth located in the very centre of the star, its method of nourishment is highly interesting. Its first process is to lie prone upon its prey, folding its arms over it to hold itself in position. Then it applies the mouth closely to the victim, and deliberately pushing out its own stomach through its mouth, wraps the mollusk in its folds, and then calmly draws back the stomach, and is ready for digestion.