MADREPORES.
The Sea-anemones (Actinidæ) will be now, thanks to the popularity of the aquarium, tolerably familiar to most readers. Although undoubtedly animal, they much more resemble flowers. They are to be found of the most brilliant colours and graceful forms.
The body of the Sea-anemone is “cylindrical in form, terminating beneath in a muscular disc, which is generally large and distinct, enabling them to cling vigorously to foreign bodies. It terminates above in an upper disc, bearing many rows of tentacles, which differ from each other only in their size. These tentacles are sometimes decorated with brilliant colours, forming a species of collar, consisting of contractile and sometimes retractile tubes, pierced at their points with an orifice, whence issue jets of water, which are ejected at the will of the animal. Arranged in circles, they are distributed with perfect regularity round a central mouth. These are their arms.” The stomach of the sea-anemone is both the seat of digestion and of reproduction. The young are actually ejected from the mouth with the rejecta of their food. “The daisy-like anemones in the Zoological Gardens of Paris,” Frédol tells us, “frequently throw up young ones, which are dispersed, and attach themselves to various parts of the aquarium, and finally become miniature anemones exactly like the parent. An actinia, which had taken a very copious repast, ejected a portion of it about twenty-four hours later, and in the middle of the ejected food were found thirty-eight young individuals.” According to one author, an accouchement is here a fit of indigestion! Sea-anemones may be mutilated, cut limb from limb, or torn to pieces, and each piece will become a new anemone in the end. “They adhere,” says Dr. Johnson, “to rocks, shells, and other extraneous bodies by means of a glutinous secretion from their enlarged base, but they can leave their hold and remove to another station whensoever it pleases them, either by gliding along with a slow and almost imperceptible movement (half an inch in five minutes), as is their usual method, or by reversing the body and using the tentacula for the purpose of feet, as Reaumur asserts, and as I have once witnessed; or, lastly, inflating the body with water, so as to render it more buoyant, they detach themselves, and are driven to a distance by the random motion of the waves. They feed on shrimps, small crabs, whelks, and on very many species of shelled mollusca, and probably on all animals brought within their reach whose strength or agility is insufficient to extricate them from the grasp of their numerous tentacula.... The size of the prey is frequently in unseemly disproportion to the preyer, being often equal in bulk to itself. I had once brought me a specimen of Actinia crassicornis that might have been originally two inches in diameter, [pg 124]which had somehow contrived to swallow a valve of Pecten maximus of the size of an ordinary saucer. The shell, fixed within the stomach, was so placed as to divide it completely into two halves, so that the body, stretched tensely over, had become thin and flattened like a pancake. All communication between the inferior portion of the stomach and the mouth was, of course, prevented; yet, instead of emaciating and dying of atrophy, the animal had availed itself of what undoubtedly had been a very untoward accident to increase its enjoyment and its chance of double fare. A new mouth, furnished with two rows of numerous tentacula, was opened up on what had been the base, and led to the under stomach; the individual had, indeed, become a sort of Siamese Twin, but with greater intimacy and extent in its unions.” The Actinia are at once gluttonous and voracious. They seize even mussels and crabs, and when they want to eject the hardest parts of the latter can turn their stomachs inside out, as one might turn out one’s pocket! Their tentacles can act on the offensive; the hand of the man who has touched them becomes inflamed, and small fish are literally killed by contact with them.
In Provence, Italy, and Greece, some varieties are used for food, the Green Actinia being in special repute.
SEA-ANEMONES.
1. Actinoloba dianthus. 2. Cereus gemmaceus. 3. Actinia bicolor. 4. Sagartia viduata. 5. Cereus papillossus. 6. Actinia picta. 7. Actinia equina. 8. Sagartia rosea. 9. Sagartia coccinea.
The Gorgons are interesting curiosities of the coral type; some are scarcely the twelfth of an inch in height, while others attain a height of several feet. The beautiful Fan Gorgon, which is often eighteen or more inches high, is so called on account of its form, and there are other very beautiful examples of arborescent gorgons. Their organism is double; the one external, sometimes gelatinous; sometimes, on the contrary, fleshy and cretaceous. It is animated with life.
A vast natural group is that of the Echinodermata, which includes five orders, or [pg 125]families, embracing among them the star-fish, the sea-eggs, or sea-urchins, and the sea-cucumbers, or “sea-slugs” (Holothurias), the latter of which are important items in the food of many Asiatics. The generic term Echinodermata signifies an animal bristling with spines, but the group includes many to whom it could not be applied.
The Star-fish (Asterias) is met in almost every sea, and in all latitudes, although more richly varied in tropical seas. They vary in colour from a yellowish-grey to orange, red, or violet. The body of the asterias is a most curious organisation, having sometimes as many as 11,000 juxta-imposed pieces, while it possesses spines and tubercles. Observe one stranded on the shore, and it may appear destitute of locomotive powers. But this is not so, for they can slowly creep over small spaces, and even up the vertical sides of rocks. Frédol says:—“If an asterias is turned upon its back, it will at first remain immovable, with its feet shut up. Soon, however, out come the feet like so many little feelers; it moves them backward and forward, as if feeling for the ground; it soon inclines them towards the bottom of the vase, and fixes them one after the other. When it has a sufficient number attached, the animal turns itself round. It is not impossible, whilst walking [pg 126]on the sea-shore, to have the pleasure of seeing one of these star-fishes walking upon the sand,” although they are very commonly left dead there.