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Animal Plants - from Harper's

 

The aquarium presents a field for delightful and ever-varying study, as its inhabitants belong to the most curious and interesting of ocean and fresh-water creatures. Fishes alone are well worthy of close observation; and when to these are added odd little reptiles, queer shell-fish, and different classes of the wonderful zoophytes, an aquarium presents a constantly changing picture of the marvels of ocean life.

CARNIVOROUS OCEAN PLANTS.

CARNIVOROUS OCEAN PLANTS.

The zoophytes are the most remarkable of all marine creatures. The name zoophyte comes from two Greek words—zoön, an animal, and phyton, a plant—and therefore has the literal signification of animal-plant.

An important member of the zoophyte family, and one often introduced into aquaria, is the actinia, or sea-anemone, sometimes called sea-rose. Sea-anemones were for a long time considered as vegetables, beautiful and gayly colored flowers of the ocean, and only comparatively recent investigation has discovered them to be animals, and blood-thirsty, voracious little robbers and murderers of the worst character.

One of the most common among the many varieties of sea-anemones is the Actinia mesembryanthemum. The polypus-hunter who finds this living flower clinging to sea-coast rocks, and bears it home as an addition to his aquarium, unless he is already acquainted with the nature of his prize, will behold with astonishment and delight the wondrous variations in the appearance of this little creature. Clinging to the rocks, the anemone probably appeared like a round leathery bag drawn in at the centre; but when placed on the miniature cliffs of the aquarium, a wondrous transformation takes place. The bag gradually expands, a mouth appears in the centre, and from it unfold a multitude of petals of a variety of colors—pale scarlet, blood-red, orange, and white—which wave gently back and forth like a graceful nodding flower. Now drop a small earth-worm or tiny fish in the water. The instant it touches the least of these petal-like tentacles the whole flower is in commotion, all the arms reaching toward the struggling victim, and holding it in a grasp so firm that escape is impossible, and it is soon drawn into the capacious and hungry stomach. Every animated thing that comes within reach of the tentacles of the anemone is mercilessly seized and devoured. Even small mollusks and Crustacea are unable to resist the power of the grasping threads, and crabs are often conquered and swallowed by this voracious living flower. For this reason sea-anemones are dangerous inhabitants of an aquarium stocked with creatures having the power of locomotion, and are best placed in a tank with other zoophytes like themselves. How often they eat when free in their natural element is unknown, but weekly feeding is said to be sufficient to sustain them in an aquarium. Small bits of meat are acceptable food, which can be dropped into the water. The instant a descending morsel touches the petals, or tentacles, of a hungry anemone, it is eagerly seized and drawn into the open, greedy mouth. The Actinia mesembryanthemum is a very long-lived creature, and certain specimens are reported to have lived over twenty years in aquaria in England.

There are many varieties of sea-anemones, and although all possess the same distinguishing characteristics, they vary in the form and color of the open flower. The Actinia gemmacia, which is like a gorgeous sunflower, is said to be the most voracious of its kind. An English naturalist describes a specimen which swallowed a shell as large as a saucer, its own diameter not being over two inches. Its elastic stomach extended sufficiently to receive this enormous prey; but as the shell completely separated the upper half of the animal from the lower, a new mouth began immediately to form, through which to convey nourishment to the lower portion, thus presenting the curious spectacle of a double-headed monster in miniature. So remarkable are the anemones in their reproductive power, that if the tentacles are injured or broken off, new ones immediately form, and if the animal be cut in two, new mouths form, and soon two perfect animals are waving their graceful tentacles to and fro in the water.

The locomotive power of the anemone, or actinia, is very sluggish. It will remain days and weeks in the same spot, and it moves only by sliding one edge of its base very slowly along the object to which it is fastened, and drawing the other after it. It can therefore never pursue its food, and appears to have no sense except that of touch, as a worm or shiner may float in the water all about the anemone without causing it the slightest agitation; but if the tiniest tip of one of its tentacles be touched, or brushed even, the whole creature is alive in an instant, and grasping for its prey. In the centre of the illustration are two specimens of this animal-plant, the wondrous flesh-eating flower of the ocean. To the left may be seen a specimen of the Eledone moschata—a small and very common member of the octopus family. The eledone is a hideous-looking beast. Its small eyes, which it can open and shut at will, are glistening, and of changing iris. Its long arms are strong enough to grasp a mussel shell, and hold it firmly until its contents are devoured. At the least touch a dark color instantly appears spread over the whole body of this curious creature, and dark prickly spines arise, which impart a stinging sensation when handled, like the anemone and sea-nettle.

The two odd-looking things in the background of the engraving are specimens of the limulus, or arrow-tailed crab. The upper side of the limulus is covered with two smooth overlapping shields, in which are two tiny eyes. Armed with six pairs of nippers, the limulus often fights its companions in the aquarium, and boldly engages in battle with the eledone, which, with its long arms, is more than a match for the pugilistic crab, whose retreat and utter discomfiture generally end the battle, for, thrown on its back, it can with difficulty right itself. If a limulus and eledone be confined in the same tank, almost daily must the former be rescued from the arms of the latter.

The palm-like creature to the right of the picture is a Spirographis, or tube-worm. This savage little beast lives in a tube formed of particles of lime or grains of sand, and stretches its gill-like threads upward, in search of food, in the form of a spiral wreath. It is very sensitive, and at the least touch on the surface of the water, or on the walls of the tank, the threads are instantly withdrawn into the tube.

In the background may be seen the waving, bell-like Medusa aurita, armed with prickly threads. It belongs to the jelly-fish family, and loves to lie near the surface of the water, but it is with great difficulty kept alive in an aquarium. When it dies, it dissolves itself into the watery element of which it is so largely composed, and its fairy-like skin can scarcely be discovered in the tank.