And here is another very beautiful thing which you must not miss. One would think the dark rock under the water had blossomed out into a small bed of filmy bluish pinks, only what you see is even more delicate and feathery. That is a patch of true corals; and it is most fortunate it was found here, for it is rarely seen, except when brought up in a dredge from water several fathoms deep.
Now let us see whether we cannot find some of the tube-worms which in feathery beauty are rivals of even the anemones and coral-polyps. Look down to the very bottom of the pool. Do you see that bunch of long, twisted tubes, which seem to be fastened to one of those big stones?
They are made by a very common sea-worm called the serpula, or shell-worm, for they are quite as often found attached to shells as to stones. This worm never leaves the tube it forms about it out of the limy mucus thrown out of its skin, so that it has no use for feet; consequently these have become simply a row of bristles along its sides, by which the animal can hitch itself up and down, or forward and backward, within its case. Sometimes it may want to draw itself back into its tube very quickly, to save its head being bitten off by some fish or ravenous worm. So along its back it has a row of between thirteen and fourteen thousand little hooked teeth, with which it can take a firm hold of the lining of its tunnel. And if it is suddenly alarmed it just raises these teeth, and then jerks itself back into its tunnel with such wonderful speed that you can scarcely see what has become of it.
Now let us lift the bundle of tubes out of the water, and examine them a little more closely. Do you see that each one is closed, just a little way below the entrance, by a kind of scarlet stopper? That shows that the worm inside is alive. The stopper is shaped just like a tiny cork, and whenever the serpula retreats into its tube it pulls this odd little stopper in after it, and so prevents any of its enemies from getting in and devouring it, just as gastropods close the aperture of their shells with the operculum.
If you were to put this bunch of tubes back into the water and watch it carefully for an hour or so, you would most likely see all the stoppers come out, one after another; and a few moments later you would see a bright scarlet tuft projecting out of the mouth of each tube. These tufts are the gills, by means of which the serpulas breathe. But at the slightest alarm the tufts would all disappear, and in less than a second every tube would be tightly corked up again, just as before.
On the Gulf coast of Florida, and throughout the West Indies, lives a larger relative of the serpula called "sea-flower," which secretes its tube upon the surface of large coral-heads, so that the tube becomes covered by the coral, leaving the opening still at the surface. "This opening," says Dr. Mayer, "is protected by a sharp spine, and is closed by the operculum of the worm when it withdraws its gills. When expanded these gills resemble a beautiful pink or purple passion-flower, about three-quarters of an inch wide."
In such pools, and in the mud among the stones near low-tide mark, lie buried several kinds of worms which poke their heads up into the water above them when the tide comes in, and expand tufts of pink, or crimson, or yellow gills and tentacles, the latter used to catch minute floating food—mainly the microscopic larvæ of various mollusks, worms, etc.—and also, in some cases, to drag to them the grains of sand out of which they construct their tubes. One of these is the fringed worm (Cirratulus) whose gills are like long orange-colored threads; and another the similar "blood-spot" (Polycirrus) whose great cluster of crimson tentacles about the mouth looks like a clot of blood on the sand. More often turned out by the naturalist's spade, however, is the tufted worm (Amphitrite) which dwells in a house made by itself, by taking a number of good-sized grains of sand, and sticking them together by means of a kind of glue which it pours out of its mouth, and which very soon "sets" and becomes quite hard, even though it is under water. This glue is so tough and strong that you can take the tube and give it quite a smart pull without tearing or hurting it in the least. And when the tube is finished Amphitrite makes that little fringe round the entrance by taking a number of very tiny grains and fastening them together in the form of threads.
There is one in this nook of our pool, now; and you may see the three pairs of blood-red tentacles which, with many pale yellow ones, the worm has thrust out into the clear water, breathing by means of some (the gills), and with the others capturing the invisible creatures upon which it mainly feeds.
The tubes of these worms usually run for several inches down into the sandy mud at the bottom of the pool, and are often carried down under the rocks, or big stones. So you will not find it very easy to dig them up. And if you startle Amphitrite herself, she will always wriggle at once down to the very bottom of her tubular fortress.
There! our four rambles are over, and although we have met with a great many interesting creatures, we have not seen nearly all that there is to be seen, either on the beach, or in the mud, or on the rocks, or in the pools which lie among them. But all the curiosities of the seashore may be found by those who have patience and know how to use their eyes.