In the last century many of the animals of the ocean were considered plants, and the sea anemones, which appear to open and shut like flowers, were described and painted in verse and prose as the flowers in the gardens of the sea. The sea anemone, common in almost every rocky pool, and found everywhere from the rocks bare at low tide to the greater depths, certainly has a very flowerlike appearance, some of them resembling a flower without a stem. Petals branch out on every side. Some are large, some small, and as though to carry out the idea the anemones are of all possible shapes and colors. Some are vivid red, others blue, some almost white, others spotted black and white, brown and barred. Almost every color is seen. Some are tall and slender, five or six inches high; others are flat. Some live in exposed places, as the luminous form attached to the shell of a hermit crab in Figure 29. Others bury themselves in the sand or hide beneath large jellyfishes, displaying the most remarkable tastes and fancies. Little wonder that the ancients believed that they were flowers. But touch one, and presto! it appears to draw within itself, and becomes a mere mound in place of the gorgeous creature which spread its splendors to the current.
The sea anemone is a highly organized animal several degrees above the jellyfishes in the scale of life, yet a very humble creature after all. They are tubular in shape, and are attached to the rocks by a sucking disk which clings so tightly that it is only with great difficulty they are forced off. Yet they have the power of moving, and slowly, very slowly, drag themselves along. Some move perhaps three or four inches a day; but this would be a long journey for many anemones, and the greatest number are fixed for life and live in crevices in the rocks. The only one I ever saw actually moving was traveling slowly across the glass of a tank. As it moved small pieces of the disk appeared to be torn off and left behind, each of which grew into a perfect sea anemone.
Fig. 29.—Sea anemones—one in the upper right hand corner is a luminous form on a hermit crab.
On the upper portion around the rim are the tentacles, armed with the same kind of ammunition (Fig. 30) found in the jellyfish, namely, lassos. In the center is the mouth.
Fig. 30.—Lasso or dart of a sea anemone.
We may imagine the anemone feeding, and we may easily see what occurs. The anemone displays its beautiful flowerlike face; it is spread out, waiting for prey. A shrimp comes swimming along, and innocently drops upon the beautiful flower. The moment it touches the attractive arms it is pierced by the lassos, and unless very vigorous is soon involved. The arms are thrown over it, the body shrinks, grows perceptibly smaller, the shrimp is pressed against the mouth, and finally ingulfed, and the once gorgeous anemone resembles (Fig. 31) a mere mound, a form which it may retain until the food is digested.
Fig. 31.—A sea anemone closed.
The structure of this interesting animal may be observed by glancing at Figure 32. The stomach is placed in the center of the animal, and is held in position by a number of partitions that are attached to the side of the anemone. These form little rooms in the body of the anemone, arranged about the stomach, but not opening into it. Each room has two windows leading into the room beyond, hence all are connected, and at the bottom all are connected with the stomach. Each room connects upward with a tentacle, which is hollow. When the animal is swallowing, the food passes down and is floated in water through the various rooms, the hard portions being rejected at the mouth. The animal has a current of water circulating through it almost continually, and it is water which, filling them, makes the tentacles stand upright and firm. Between the bases of the tentacles are the eyes. When the animal closes up, it forces the water out of its mouth and is able to shrink to a small and inconspicuous object.
Fig. 32.—Section of an anemone: c, tentacles; g, little rooms; d, mouth; g´, opening between rooms; a, sucking deck or foot; e, stomach.
Lowly as are the sea anemones, they often display an amount of intelligence that few would give them credit for. On the Florida Reef was a large lagoon, its bottom pure sand, and so light that the slightest dark object was easily observed. In the sand, buried several inches deep, lived a large anemone, whose normal hue was a dark brown, but when expanded was almost the exact color of the sand; not only this, its tentacles were covered with bits of sand. In a word, the anemone had disguised itself so that large and threatening fishes would not see it, as they swam along in search of food. The habit of placing bits of shells and sand on the tentacles is a common one. I have noticed it in a sand-living form on the California coast. As the tide went out and left the anemones dry, they were invariably covered with sand which adhered to the tentacles as though it had been gummed. To accomplish this protection from the hot rays of the sun, the anemone had picked up the atoms of sand with its tentacles and distributed them over its surface. As there were thousands of pieces, the amount of work may be imagined.
Anemones are found in many strange places. One, as we have seen, rides about upon the back of a hermit crab; another is so often found on the top of an ordinary crab that it is evidently a habit of the anemone. The anemone thus travels about with its host and shares its food. In the Indian Ocean a German naturalist found on every crab of a certain kind, which he caught, a sea anemone fastened upon the inside of the large biting claw. Thinking it accidental, he caught a number of crabs, but nearly all had the small anemone, which was so placed that when the crab raised its claw to its mouth to eat and tear its food, the sea anemone was in a position to obtain a full share of the food. Still thinking that this must be an accident, the naturalist placed a large number of the crabs bearing the sea anemones in a tank and removed the anemones with a knife, placing them in the water. The following day when they were examined every crab had its attendant again upon its claw. Again the experiment was tried, and again the crabs collected their curious attendants. The naturalist now cut one of the animals into several pieces, and even then the crabs attempted to collect them.
The anemones deposit eggs in vast numbers, which change into strange, free-swimming animals that finally settle upon the bottom and soon grow into the adult forms. They have another method of developing. Singular little "buds" appear on the sides and base of the adult, which soon resemble the parent. The anemone is very long-lived; specimens have been kept for nearly a century. They also have a marvelous faculty for renewing themselves if injured. If one is divided, sometimes two anemones will be the result, recalling their distant cousin the little hydra, which when turned inside out receives its food and eats as though nothing had happened. No amount of mutilating appears to affect its various portions, as each soon develops into a perfect hydra.
The sea anemone is a common form of the aquarium. It is easily secured by those living near the ocean, forming a most interesting pet, taking food from the hand, and soon proving itself possessed of a remarkable appetite. The anemones are among the great purifiers of the ocean, devouring a vast amount of dead matter which might pollute the water, and continually pumping the water through their systems, sifting out the animal life, dead or alive. Aside from this, the anemones are chiefly useful as beautifiers of the ocean. In the Mediterranean Sea they are sometimes eaten by the Italians and French. Certain fishes and crustaceans prey upon them.
