Popular Science Monthly/Volume 7/May 1875/Sea-Anemones
By Rev. S. LOCKWOOD, Ph.D.
EVEN in minds the most illiterate you will find a sort of philosophy, if you but look for it. Among the dwellers by the shore is a class known as Watermen. These men, with great irregularities of toil and idleness, obtain the support of their families wholly from the bounteous, though sometimes precarious, harvest of the sea. Often one finds among them men of the roughest mould, yet with generous natural gifts, but without either education or culture. Of natural phenomena, in a practical way, they are shrewd observers. They know a good deal, too, about many queer forms and strange habits belonging to the denizens of the deep. In their way, they are positive men, and real empiricists too—for, from their limited lookout, and their small stock of facts, they will generalize as broadly as do some scientists upon a few experiments. An old waterman, who could not read a word, said to us: "Sir, Nature works the same in every place. There's nothing on the land what isn't in the sea; and I've even seen ships in the sky!" Here, then, although not a little empirical, in our fisherman's philosophy was a splendid generalization. And how broad it was! It covered every province possible for human experience, in his conception—the earth, the sea, and the air.
And empiricism begotten of a spirit in no wise nobler, abounded in the elder science. Thence have come down to us those heated controversies on the supposed vegetable nature of the polyps that build the corals, and other similar structures in the great deep. And there was that temporary calm which set in upon that stunning clincher of that empiricist, who declared that the coral polyps were, and must be, plants, for—"I have seen the flowers!" And Sir Wiseman was true. And so was the fisherman true, when he said, "he had seen ships in the sky." Each in his own way had seen a mirage.
But that clincher would not stay clinched. As concerned their external forms, all admitted them to be sea-flowers. Still, these flowers of the ocean would insist on behaving themselves in divers ways, looking strangely in the direction of sentient things, albeit their plantlike aspect looked contrariwise. Could Nature, just here, Janus-like, look two ways at once? Might it not be that these mysterious things were the habitants of a certain border-land of life? Another empiricism a generalization as splendid as that of the fisherman. So in complacent wisdom they called them zoophytes, namely—
Animal-Plants.—Time, and a love of truth, will set a good deal right that seems inveterately wrong. Even this brilliant compromise must yield to the verdict that accrues from the patient study of facts generously collected and carefully collated. So this Janus myth, the zoophyte, which had become a cant word in science, turns out to be of no value as representing a fact in Nature. Though flower-forms they were, yet they were really animate things, and capable of acts indicative of will.
Our object now is to say something of one of these flower-like types of marine life, namely, the Sea-Anemone. It is significant, as showing the suggestiveness of these creatures, that, however diverse the nomenclature of science may be in regard to them, it is often almost poetical, and the words used are always expressive, and even possess pictorial significance. De Blainville named them Zoantharia, from which comes Animal Flower. Dr. Johnson's term took a wider latitude, and, although quite formidable-looking, and not in the best taste, was very significant. He gave the name, Zoophyte helianthoidea, which is to say, the Sunflower-like animal-plant. In these terms the animal nature and the flower-like form are intended. The creature is really a polyp, a soft, almost pulpy, sac-like structure, with a fringe of tentacles, like a halo of rays, around the upper end; in the centre of the circular fringe, the mouth, or oral aperture, being situated. Hence it is often spoken of as an actinia, which really means possessing rays. The word is now worked into another word, Actinozoa, meaning rayed-animals, that is to say, animals with rays around an oral disk. But the term is used to designate a class; hence it includes all the polyps, those that construct coral, and the others. This class is again divided into several orders, one of which is named Zoontharia, or, as it is sometimes called, the Helianthoid polyps. It is in this order that the actinia proper is found; and, therefore, it is there that we must find our sea-anemone.
Having found for this pretty object, in a system of science, "a local habitation and a name," let us see if we can make out the structure of a sea-anemone, or, as it is often called, an Actinia.
Taken in the hand, the sea-anemone imparts a slippery feeling, and it seems to have the consistency of leather. To get at its precise form, look at the cut given of Actinia rosea, a British species. Now, please follow closely our description a little while. As the actinia erects itself, attached to a rock or stone, it looks like one of the purses formerly fashionable, if one such could be made to stand of itself erect, and have the frill around the upper end to project in a circle. But we must be more particular than this. The upright part, that which is called by naturalists the column, is hollow, like a sack. Its base is really a sucking-surface, enabling it to adhere to any hard object. By this sucking base it can glide, or travel along, much like a snail.
Fig. 1.—a, Arachnactis Albida; b. Actinia Rosea.
And as it thus moves, it can keep its flower spread out, and its many tentacles in constant play—in fact, fishing on the way. Their movement is, however, very slow. Indeed, a "snail-pace" would be alarmingly fast for an actinia. We have watched them attentively, and have found that an inch in an hour was a very satisfactory performance. At the top is an opening, called the oral cavity, which, in the rosea, is surrounded just inside with a beading of little dots. This opening may be called the mouth, because the food is passed at this aperture into the stomach, which is a cylindrical sac, suspended below, and reaching about half-way down the great cavity of the column. Around the oral cavity, and external to it, is a plain surface, which is technically known as the "disk." Around the disk, on its outer edge, is the fringe of tentacles. Each one of these is a little hollow cylinder, opening into the great cavity of the column immediately Tinder the edge of the disk. In fact, these tentacles, or feelers, connect with the interior of the stem of the Anemone, just as the fingers of a glove do with the interior of the same. We should also mention that, at the bottom of the sac, which is here called the stomach, is an opening into the general cavity. Now, around this suspended stomach, that is, between its outer wall and the inner wall of the column, is a system of compartments in series. These vary as to number in the different species. By looking at the cut showing a cross-section of an actinia's stem, we observe that six of these compartments are complete, and reach from the stomach to the walls of the column. These six compartments are made by as many radiating vertical plains, whose edges on the one side are in contact with the inner walls of the column, and the edges on the other side touch upon the outer walls of the stomach. Between these compartments are others of less capacity. It is noticeable that these are, in like manner, formed of vertical plains, of different widths; and, further, that they are only attached on one edge, and that to the inner walls of the
Fig. 2.—Cross-Section of an Actinia-Stem.
great column, that is to say, they do not connect with the stomach. To understand the relation of these different walls of the compartments to the entire structure, a glance at the diagram will suffice, when it is borne in mind that the transverse section, thus represented gives also a section of the inner cylindrical sac, or stomach.
The upright walls of these compartments which we have described are known in science by the name mesenteries. Of what use are they? The most obvious service they perform for the animal when erect is, as we think, the stiffening of the structure. And this is done at will, as if it were a sort of erectile tissue. Now, as the cardinal plains connect both the inner and the outer cylinder, that is, the stomach and the column, it will be seen that the efficiency in the direction of imparting strength is considerable. The column is by so much the more strengthened, as it has the more of these upright planes or septæ attached to it by one of their respective edges.
But it is in these compartments, and on the mesenteries themselves, that the origin of life for the actinia's progeny begins—for there the ova and the spermatozoa are found. On the mesentery-walls are borne in series certain reddish bands. These are the reproductive organs, and contain the ova and the spermatozoa. Generally actiniæ are what the botanists call diœcious; that is, the ova are found in an individual—that we may call the female; and the spermatozoa in one that we may in like manner call the male. As to the time, and even the method of propagation, mother actinia is very capricious, there being, so far as our observations may determine, no regularity, but at the right time doubtless, for her convenience, the actinia evicts her young. Usually these are discharged at the mouth. They are tiny little things, clad with cilia, with which they move freely in the water for a little while, then settle on some stone, and give themselves up to a sedateness worthy the parent that gave them birth. It often happens that mother Anemone sends out her little ones in a very rough way into the world. In fact, they are introduced into actinian society sadly sans ceremonie. From the mesentery chambers are certain little ducts which open into the neck of the orifice, which we have called the mouth; and this orifice, it will be remembered is directly over the open stomach. So it sometimes happens that when one actinia is sending out a litter of her babies from the mouth, she, just at that very moment, takes a notion to empty her stomach of the indigested leavings of her last meal, so that these indigesta and two score innocents are evicted in a dreadfully execrable and unmeally-mouthed manner.
Fig. 3.—Vertical Section of Actinia.—a. Stomach-sac; b. Mesentery; c, Craspedum; d. Tentacle.
We must now notice a remarkable apparatus known as the lasso-cells. It has been repeatedly observed that an actinia has a stinging, or, as it is called, an urticating power over the tissue of other animals. Now, there are in different parts of the body of an actinia innumerable cells, from which, especially the cells on the tentacles, it can dart an invisible thread. The microscope can see it, and has made known its structure. In some species this delicate thread thus shot out is a marvelously-complex affair. It is coiled up, and when necessity urges, at the will of the animal, it is darted like a cord from a spring-trap. Now, this is just the simplest part of it; for, strange to say, when this thread is shot forth, just at the striking instant, out of the sides of this invisible thread other threads or snares spring, and these last are barbed. What a wonderful mechanism is this!
Let me invite you to a sight I have many times beheld. I have in captivity a hungry sea-flower. Knowing well what suits its palate, I take a delicate morsel like a pilule, and let it fall into the water. It descends upon the waving petals, or tentacula, on the point of one of which the pretty creature has caught it in an instant. How delicate the adjustment upon its more than fairy fingers! For a few moments it is balanced with the nicest poise on that dactylic petal. Ah! a voracious and unmannerly little bummer of a minnow sees the delicious morsel, and makes a rapid dash to snatch it from my pet. "Good! good! Well done, my bonnie!" I did not see the slightest motion of that indignant flower-creature; yet assuredly there was a movement, and an effective one, too: for the zoophyte had shot one of its invisible shafts; and the ichthyic thief dashes off like one frantic with pain. Is he hurt? Likely. His is an urticated experience. He is stung in the snout! See how he seems to shake his nose! He fairly seems to sneeze again, and actually conducts himself much like a puppy that, uninvited, has put his nose into a bowl of hot soup. Ah, ha! He is rubbing his fishy proboscis against a frond of sea-lettuce. Perhaps the salad may cool his burning pain.
Mr. Fish soon recovers his equanimity of mind; and it is observable that his deference to Mrs. Actinia since that affair has been of a decidedly distant character.
But we return to mention certain organs attached to the free edges of the mesentery-walls, those perpendicular septæ, or membranous partitions, which we have taken some pains to describe. Says Nicholson: "Along the free margins of the mesenteries there also occur certain singular convoluted cords, charged with thread-cells, and termed 'craspeda,' the function of which is not yet understood. It
Fig. 4.—Metridium Marginatum.—Fringed Actinia (expanded.)
is believed, however, that the apertures, termed 'cinclides,' in the column-walls of some of the Actinidæ, are for the emission of the craspeda." Now, some observers say that they have seen these urticating phenomena take place from the side of the column of an actinia. Is it not, then, very likely that herein is the function of the craspeda? These "cinclides," or openings in the walls of the living column, are the portholes of the little tower, whence the "craspida"-like archers launch their invisible shafts.
That is an enviable experience when one is favored with the discovery of one of Nature's secrets. We recall one such made in 1858 or 1859. Though we at that time prepared an account for publication, yet it never saw the light. In order to refresh our memory, we to-day have taken from our desk this old manuscript, and given it a perusal. We had among our aquarian pets a fine fringed actinia, Metridium marginatum from Newport. To our glad surprise, we noticed one day that, as it adhered to the glass side of the tank, it was surrounded by a number of tiny young ones. The question was, where did they come from? That they came from the ova I had weighty reasons for doubting. So we set ourselves to find out, if possible. One day we were watching this anemone as it was gliding on the glass. Of course, the entire base was moving. But—no that is just where we at first were in error, for there was a little speck of its base that would not go along with the rest. There that little bit of the sucking-base stuck and held its place stubbornly. The great base kept at it—pulling, as it seemed, until a mere thread-like shred of matter connected the main mass and this little stubborn, speck-like remnant. And that connecting shred stretched like a thread of India-rubber. For nearly an entire day did this sort of thing continue, when at last the shred snapped, and the one part was drawn up into the base and the other part into the adhering speck or fragment. With our pocket-lens, we watched that tiny bit which had seceded from the body politic, or rather, from which the body politic had itself withdrawn. It soon gathered itself up into a plano-convex speck. The next day we observed a depression setting in at the convex point. In a day more we detected movement. It was dividing, and there was a pulling in two directions. This did not last over a day, and there were now two specks instead of one. In about three days, at top of each, five little tentacles appeared, and a tiny mouth. Wonderful to say, each was a young actinia. And
Fig. 5.—Fringed Actinia (closed).
how strangely begotten, too! Sloughed off—actually exscinded from the base—a veritable bit of that dear old mother; not bone of her bone, since bones she had none; but verily flesh of her flesh. This was, indeed, to us a new sort of fission. How we did watch that pair of self-made twins! Very diminutive they were, truly; but very great pets for all that.
These young actinia very rapidly increased in size, and soon had doubled the number of their feelers. Supposing that this argued an increase of feeling on their part, we found ourselves feeling an increase of interest in their ways and welfare. Just as this mutual understanding had been established, an incident occurred which filled us with anxiety. The mother-actinia began gliding back toward our little ones. That firmly-adhering base, sticking fast as the boy's sucker with which he lifts a brick, came slowly but surely, advancing toward her children. On, and on, now she is right upon them! Good-by, my twin babies, it is all-day with you now! That sucker of a mother has taken you in beyond all hope of redemption. How we did wish that that cruel parent would move on and let us see our pets again, even if dead! But no, now she would not move at all; and for nearly a day she retained that position. At length we detected movement—the gliding had begun. But, oh, how provokingly slow it was! Ah! we begin to see them at the peripheral edge of that mother's base. How flat the poor things look! No wonder, such a squeezing maternal embrace as that was. They are fairly out now—dead! dead! See, their little tentacles are protruding. It looks as if they were in a hurry to shake out their crumpled frills. Well, well, they have come out of this singular occultation as brilliantly as ever emerged a binary star.
The question whether these beautiful creatures have a nervous system seems not settled. That they manifest phenomena indicating a will, cannot be doubted. On one occasion my pets were all sulky, like "Jack in the doldrums." Every one was closed, which means it had shriveled up into a mere gelatinous lump. Each one in this condition had a disgusting look, resembling nothing so truthfully as a
Fig. 6.—Anthea Cereus (Opelet).
ripened boil when the fetid core is ready for extraction. And we have often seen even this repulsiveness intensified, by evolving in threads a white, stringy slime, that peculiar mucous lining of which, in parts at least, the creature often takes occasion to divest itself when in repose. (See cut of Fringed Actinia closed.)
As above, when in repose, these sea-anemones look like clots of gelatine, and, as many of the actinia are very small, we have known fishermen who have handled them, when adhering to oysters, for years, and never knew that they were aught else than spots of slime. Once, when out on the shore at a very low tide, and busy overturning stones, in search of creatures thus concealed, a fisherman, wondering what we were about, came and accosted us:
Fisherman—"What have you got, mister?"
Self—"Some little sea-flowers;" and we pointed to certain little hemispheres of pellucid but limpid pearl, on a stone held in our hand.
Fisherman—"What! them grease-spots?"
Self—"Yes. And you should see them when the tide's up. Then every one opens into a little flower. They're only shut up now."
With an expression that indicated doubt of our veracity, or sanity, Piscator turned away, muttering as he left, "Guess you'd better shut up, my blossom!"
However, we took our "grease-spots" home, proud enough of them. After time given for rest they came out finely. Pretty things they were. There was one especially, over which we had both joy and sorrow—the one to have found it, and the other when it died. It was a wee but winsome thing, about a third of an inch when unfolded, and all parts of it, column, and disk, and petals, were each and all of a soft, limpid emerald. Oh, we thought, if that could be transformed into a hard substance, what a gem it would be! That was the only time we ever saw an entirely green anemone. The green opelet of Great Britain is only so as to its tentacles, and even these are tipped with red. We have often obtained from the rocks in the East River very pretty small anemones, of an orange hue.
Generally the sea-anemone will not spread her beautiful form in a bright light. Often, when all seemed sulky and there was a general collapse, we have restored the whole coterie to good-humor, simply by covering up the aquaria for an hour or two, and then uncovering, when the flowers will fully open. It was a great transformation to see, when this change took place with our favorite—a fine, large, fawn-colored Metridium marginatum, obtained from Newport. When in healthful expansion it was larger than a good-sized dahlia; and although of a subdued neutral tint, yet in form and color we thought our marine-flower the superior of its terrestrial rival.
Somewhere we read the lucubration of a philosopher that there was no humor in Nature, but all was serious. The observation struck us as very learned, but very silly. No humor in Nature? Nonsense! Come out from your candle-light cogitations unto some real observations in the sunny light of Nature's beaming face, and I can show you humor. Ay, fun, if you will—yes, even practical jokes. A large actinia took a notion to swallow a large scallop, which it had captured. After considerable stretching it got the bivalve down into its stomach, and in due time the contained mollusk was digested. But what about the shell? Why, this—it could not get it up again! It was a double disaster—literally as to the scallop, and metaphorically as to the polyp: both were sadly taken in. Actinia now looked very serious—comically so—like one in an evil strait. Perhaps it felt as bad as a hen-pecked subject, for it had got itself around a pecten, and a, pecten maximus at that. If a guest at tea should swallow the tea-saucer, matters would look alarming. And this bolted scallop was as big as a saucer. The effect upon the actinia's looks was ludicrous, since there was a narrow, bulging, equatorial belt, strongly significant of an undue centrifugal force in activity at that place. Get rid of the saucer it could not; so it seemed, with a saucy air, to have made up its mind to resort to an expediency that should fairly checkmate the strange exigency. And this expediency was a change of base. In fact, it transformed its old base entirely. Tentacles grew out around it, an oval aperture appeared, and, in a word, it became a double actinia, and the large scallop shell was made a double base, and was accepted ever after as the demarcation of the two individualities. No fun in Nature? If this, despite a smack of sauciness, was not a practical joke of the first water, then bring out your specimen-brick, old Sober-sides!
But the time is up, and so much must be left unsaid. In the cuts is the white Arachnactis, a baseless actinia, which, stuck in the mud, waves its few snaky tentacles about. And there is the waxy Anthea, or opelet, with its snaky or gorgon hair. But we must stop, without telling of the singular varieties of forms, and the rich diversities of tint and color, and the sometimes queer, yet normal functions performed by these marine animal mimics of the floral structures of the land.