The Book of the Aquarium/Part 2/Chapter 6
WHAT IS AN ANEMONE?
It is very strange that where the animal and vegetable kingdoms meet, the forms should assume such close resemblances to each other, as to make it frequently a matter of difficulty to determine to which of the two great departments some special specimen shall be assigned. Here are the lovely sea-flowers—flowers only in name and appearance—representing the lowest links of animal life and pointing to that last link where the animal and the vegetable blend into one, bearing all the outward resemblances to flowers from which they take their appropriate names, yet all of them strictly animals, endowed with volition, and in their general organization assimilating to the extensive series of zoological orders which stand above and beneath them. The sea anemones are animals of the lowest class—zoophytes of the great Cuverian division of Radiata. It is in this division that animation is seen to tremble and flicker in the socket, and to become gradually extinguished as we descend the scale and approach the confines of the kingdom of verdure. Here, then, life has its lowest if not least lovely forms; the individuals have less individuality, many of them live in groups and clusters, and increase in a semi-vegetative manner by gemmation, or the formation of bud-like germs, while others generate by spontaneous fissure, and break up into numerous forms, each of which rapidly acquires the form of the parent, and proceeds in the same way to increase its kind.
The Radiata are so named on account of the ray-like form generally observable in the structure of the creatures; in some the ray-like divisions give such a speciality to the structure as to distinguish them at once as members of this division; as in the star-fishes, for instance, in which the intestinal canal branches out from the body into the several rays which form the star, and in the anemones, in which the relation to the tribe is at first sight perceptible in the tentacles which surround the mouth, and which render it so exquisitely beautiful as a marine representative of a true flower.
But though the term Radiata is applied to an extensive division, in which the members have many characteristics in common with each other, the ray-like form is not equally distinguishable in all. In some tribes there is a tendency to associate into groups, in which each individual has a certain degree of connection with the rest, as in the infusoria common in our brooks, and indeed most of the polypes which thus live in community. The resemblance to vegetable forms is, however, common to a great portion of the Radiata, and those in which this resemblance is the strongest are grouped together under the general designation of Zoophytes. In Zoophytes, the leading feature of a radiate animal is very distinctly observable, and that leading feature is the arrangement of the vital organs around a centre, the organs composing
EDWARDSIA VESTITA, ESOP PRAWN, ENTEROMORPHA
COMPRESSA, ULVA LATISSIMA.
the rays of the imaginary star, or the petals of the imaginary flower, to which the mouth or stomach is the centre.
Among the Zoophytes we meet with many of the creatures which have the greatest attraction for the student of the Aquarium. The brooks supply him with the curious hydra, the seven-headed monster that perpetuates one of the triumphs of Hercules—withal a beautiful and wondrous creature, that may be cut in pieces, turned inside out, or even thrust one animal within the other, and still remain the same. The sea supplies the madrepores, the builders of ocean-reefs, and the founders of islands and continents; as it also supplies the sea anemones of more than a hundred species, from the curious Edwardsia vestita, here figured, from the first seen in this country, at present in the collection of Mr. Alford Lloyd, to the familiar members of the genus Actinia, obtainable everywhere on our coasts.
The true Zoophytes have all, more or less, the plant-like form, and they readily separate into two great classes, namely, the Anthozoa, or flower-life, and the Polyzoa, or many-life, in which the individuals are associated together in numbers. They are all inhabitants of water, are all destitute of joints, lungs, nerves, and proper blood-vessels; but in the place of nerves possess what naturalists call an irritable system, in obedience to which they expand or contract at will. At the upper part of the body is situated the mouth, which is usually surrounded with tentacles, which are mostly used in securing prey. There is no alimentary duct, for the stomach has the form of a simple sac, the aliment being injected and ejected by the same orifice.
The Anthozoa comprise animals which are perfect in themselves, and these are mostly soft bodied, having no shelly covering, and are protected only by the leathery integument which surrounds them, and the thousand weapons of offence and defence which they expand in the form of tentacles. Among the Polyzoa we meet with creatures that encase themselves in horny shells, or calcareous coatings, such as the Madrepores, which, like submarine masons, elaborate the carbonate of lime which the sea supplies them with, into shelly retreats; and the tubed Hydrioda, which construct winding galleries and convoluted tubes, from the mouths of which they protrude their fans and tentacles in search of prey.
Among the higher orders of the Radiata we meet with the strange Sea Cucumbers and the Sea Urchins, and the Star fishes; and among the lower orders the Sea Anemones, many forms of which are described and figured in these pages.
A Sea Anemone, then, is a Zoophyte belonging to the class Anthozoa, or flower-life, and the order Helanthoida, or sunflower-like creatures. The central disk of the sea flower is composed of the lips, which open into a mouth which communicates with the simple sac which constitutes the stomach, and the petals and fringes which surround it—now like the anemone, now like the sunflower or the mesembryanthemum, or the richest carnation that ever won for a florist a golden prize. The further subdivision is dependent on the details of individual structure; and a large section—that of Actinia—comprehends most of those on which the aquarian bestows his patience in the work of domestication.
The Actiniadæ—so named from the Greek—signifying a ray of the sun—are an extensive family, of which more than a hundred species are to be found on our coasts, or in the deep bays adjacent. But few of these are suited for confinement in aquaria, and of these the chief are the Actinia proper, the Sagartia, most of which are usually grouped with the Actinia; the Anthea Cereus; the splendid Adamsia Palliata, which is the only known species of the genus to which it belongs; and a few of the Bunodes, Edwardsia, and Corynactis.
In all the varieties of sea anemones the mode of life is similar; they are carnivorous, and obtain their prey by means of the ever-seeking tentacles that search the lymph around them, and secure sometimes fishes, at others mollusks, but more frequently the minute forms of infusorial life that abound in the sea, or in the artificial water of the tank. The mode of reproduction is by ova, which are sometimes vivified in the body of the parent, and not only do they give birth by ejection from the mouth of a numerous progeny, but actual divisions of the body may be made, and each division will acquire completeness. Dr. Johnson relates several instances in proof of this, one of which is particularly interesting. A specimen of Actinia crassicornis had swallowed a large, sharp-edged shell, which so completely stretched the body of the creature as if on a ring of wire, as virtually to cut it into two equal parts. Thereupon it put out from the base a new disk, with mouth and tentacles, and became at once a double anemone, to which the gorged shell served as an intermediate base of attachment. Dr. Cocks has seen specimens of Bunodes alba acquire complete forms in duplicate when the original specimen has been severed into two or more parts; and there are many other instances on record of this plant-like division of sea anemones having been observed.
Though apparently immobile, there are few species but possess some power of locomotion. We frequently meet with anemones attached to stones, sand, or shells, by a wide sucking base, and if some species be moved from their chosen site, certain death is the result. Yet in by far the greater number there is a distinct faculty of progression—the anemone, by a slow, gliding motion, gradually removes itself, and climbs up the sides of the vessel, or takes possession of a tuft of weed, or shifts from one stone to another, or fairly leaves go of its anchorage, and floats like a balloon upon the surface. Thus low in the scale as they are, they possess will, and a power of obeying it; they have their organs of locomotion, of attack, and defence; though naked, they are armed for combat on an equality with their enemies, and succomb at last to man—the universal destroyer and appropriator—who turns them to account as food, or treasures them as gems of beauty that gratify his eye, and even win over the affections of his heart, while they lead him to contemplate the variety and profuseness of that life to which the Almighty has given so many wondrous forms, and instincts, and economies, every one of which proclaims—
“ The hand that made us is divine.”