The Atlantic Monthly, Volume 10, No. 57, July, 1862

Cuvier, who held the key to so many of the secrets of Nature, detected at last its true structure; he pronounced it to be a Star-Fish with a stem, and at once the three series of facts respecting the Trochites, the fossil lilies, and Guettard's marine palm assumed their true relation to each other. The Troehites were recognized as simply the broken portions of the stem of some of these old fossil Crinoids, and the Crinoids themselves were seen to be the ancient representatives of the present Comatulae and Star-Fishes with stems. So is it often with the study of Nature; many scattered links are collected before the man comes who sees the connection between them and speaks the word that reconstructs the broken chain.

I will begin my comparison of all Echinoderms with an analysis of the Star-Fishes and Sea-Urchins, because I think I can best show the identity of parts between them, notwithstanding the difference in their external form; the Sea-Urchins having always a spherical body, while the Star-Fishes are always star-shaped, though in some the star is only hinted at, sketched out, as it were, in a simply pentagonal outline, while in others the indentations between the rays are very deep, and the rays themselves so intricate in their ramifications as to be broken up into a complete net-work of branches. But under all this variety of outline, our problem remains always the same: to build with the same number of pieces a star and a sphere, having the liberty, however, of cutting the pieces differently and changing their relative proportions. Let us take first the Sea-Urchin and examine in detail all parts of its external structure. I shall say nothing of the internal structure of any of these animals, because it does not affect the comparison of their different forms and the external arrangement of parts, which is the subject of the present article.

On the lower side is the mouth, and we may call that side and all the parts that radiate from it the oral region. On the upper side is a small area to which the parts converge, and which, from its position just opposite the so-called mouth or oral opening, we may call the ab-oral region. I prefer these more general terms, because, if we speak of the mouth, we are at once reminded of the mouth in the higher animals, and in this sense the word, as applied to the aperture through which the Sea-Urchins receive their food, is a misnomer. Very naturally the habit has become prevalent of naming the different parts of animals from their function, and not from their structure; and in all animals the aperture through which food enters the body is called the mouth, though there is not the least structural relation between the organs so designated, except within the limits of each different branch or division. To speak of these opposite regions in the Sea-Urchin as the upper and lower sides would equally mislead us, since, as we have seen, there is, properly speaking, no above and below, no right and left sides, no front and hind extremities in these animals, all parts being evenly distributed around a vertical axis. I will, therefore, although it has been my wish to avoid technicalities as much as possible in these papers, make use of the unfamiliar terms oral and ab-oral regions, to indicate the mouth with the parts diverging from it and the opposite area towards which all these parts converge.[28 - When reference is made to the whole structure, including the internal organs as well as the solid parts of the surface, the terms actinal and ab-actinal are preferable to oral and ab-oral.]

[Illustration: Sea-Urchin seen from the oral side, showing the zones with the spines and suckers; for the ab-oral side, on the summit of which the zones unite, see February Number, p. 216.]

The whole surface of the animal is divided by zones,—ten in number, five broader ones alternating with five narrower ones. The five broad zones are composed of large plates on which are the most prominent spines, attached to tubercles that remain on the surface even when the spines drop off after death, and mark the places where the spines have been. The five small zones are perforated with regular rows of holes, and through these perforations pass the suckers or water-tubes which are their locomotive appendages. For this reason these narrower zones are called the ambulacra, while the broader zones intervening between them and supporting the spines are called the interambulacra. Motion, however, is not the only function of these suckers; they are subservient also to respiration and circulation, taking in water, which is conveyed through them into various parts of the body.

[Illustration: Portion of Sea-Urchin representing one narrow zone with a part of the broad zones on either side and the ab-oral area on the summit.]

The oral aperture is occupied by five plates, which may be called jaws, remembering always that here again this word signifies the function, and not the structure usually associated with the presence of jaws in the higher animals; and each of these jaws or plates terminates in a tooth. Even the mode of eating in these animals is controlled by their radiate structure; for these jaws, evenly distributed about the circular oral aperture, open to receive the prey and then are brought together to crush it, the points meeting in the centre, thus working concentrically, instead of moving up and down or from right to left, as in other animals. From the oral opening the ten zones diverge, spreading over the whole surface, like the ribs on a melon, and converging in the opposite direction till they meet in the small space which we have called the ab-oral region opposite the starting-point.

Here the broad zones terminate in five large plates differing somewhat from those that form the zones in other parts of the body, and called ovarian plates, because the eggs pass out through certain openings in them; while the five narrow zones terminate in five small plates on each of which is an eye, making thus five eyes alternating with five ovarian plates. The centre of this area containing the ovarian plates and the visual plates is filled up with small movable plates closing the space between them. I should add that one of the five ovarian plates is larger than the other four, and has a peculiar structure, long a puzzle to naturalists. It is perforated with minute holes, forming an exceedingly delicate sieve, and this is actually the purpose it serves. It is, as it were, a filter, and opens into a canal which conducts water through the interior of the body; closed by this sieve on the outside, all the water that passes into it is purified from all foreign substances that might be injurious to the animal, and is thus fitted to pass into the water-system, from which arise the main branches leading to the minute suckers which project through the holes in the narrow zones of plates.

[Illustration: Star-Fish from the ab-oral side.]

Now in order to transform theoretically our Sea-Urchin into a Star-Fish, what have we to do? Let the reader imagine for a moment that the small ab-oral area closing the space between the ovarian plates and the eye-plates is elastic and may be stretched out indefinitely; then split the five broad zones along the centre and draw them down to the same level with the mouth, carrying the ovarian plates between them. We have then a star, just as, dividing, for instance, the peel of an orange into five compartments, leaving them, of course, united at the base, then stripping it off and spreading it out flat, we should have a five-rayed star.

[Illustration: One arm of Star-Fish from the oral side.]

But in thus dividing the broad zones of the Sea-Urchins, we leave the narrow zones in their original relation to them, except that every narrow zone, instead of being placed between two broad zones, has now one-half of each of the zones with which it alternated in the Sea-Urchin on either side of it and lies between them. The adjoining wood-cut represents a single ray of a Star-Fish, drawn from what we call its lower side or the oral side. Along the centre of every such ray, diverging from the central opening or the mouth, we have a furrow, corresponding exactly to the narrower zones of the Sea-Urchin. It is composed of comparatively small perforated plates through which pass the suckers or locomotive appendages. On either side of the furrows are other plates corresponding to the plates of the broad zones in the Sea-Urchin. Where shall we look for the five eyes? Of course, at the tip of every ray; exactly where they were when the rays were drawn up to form the summit of a sphere, so that the eyes, which are now at their extremities, were clustered together at their point of meeting. Where shall we look for the ovarian plates? At each angle of the five rays, because, when the broad zones of which they formed the summit were divided, they followed the split, and now occupy the place which, though it seems so different on the surface of the Star-Fish, is nevertheless, relatively to the rest of the body, the same as they occupied in the Sea-Urchin. Assuming, as we premised, that the central area of the ab-oral region, forming the space between the plates at the summit of the zones in the Sea-Urchin, is elastic, it has stretched with the spreading out of the zones, following the indentation between the rays, and now forms the whole upper surface of the body. All the internal organs of the animal lie between the oral and ab-oral regions, just as they did in the Sea-Urchin, only that in the Star- Fish these regions are coequal in extent, while in the Sea-Urchin the ab-oral region is very contracted, and the oral region with the parts belonging to it occupies the greater part of its surface.

Such being the identity of parts between a Star-Fish and a Sea-Urchin, let us see now how the Star-Fish may be transformed into the Pedunculated Crinoid, the earliest representative of its Class, or into a Comatula, one of the free animals that represent the Crinoids in our day.

[Illustration: Crinoid with branching crown; oral side turned upward.]

We have seen that in the Sea-Urchins the ab-oral region is very contracted, the oral region and the parts radiating from it and forming the sides being the predominant features in the structure; and we shall find, as we proceed in our comparison, that the different proportion of these three parts, the oral and ab-oral regions and the sides, determines the different outlines of the various Orders in this Class. In the Sea-Urchin the oral region and the sides are predominant, while the ab-oral region is very small. In the Star-Fish, the oral and ab-oral regions are brought into equal relations, neither preponderating over the other, and the sides are compressed, so that, seen in profile, the outline of the Star-Fish is that of a slightly convex disk, instead of a sphere, as in the Sea-Urchin. But when we come to the Crinoids, we find that the great preponderance of the ab-oral region determines all that peculiarity of form that distinguishes them from the other Echinoderms, while the oral region is comparatively insignificant. The ab-oral region in the Crinoid rises to form a sort of cup-like or calyx-like projection. The plates forming it, which in the Star-Fish or the Sea-Urchin are movable, are soldered together so as to be perfectly immovable in the Crinoid. Let this seeming calyx be now prolonged into a stem, and we see at once how striking is the resemblance to a flower; turn it downwards, an attitude which is natural to these Crinoids, and the likeness to a drooping lily is still more remarkable The oral region, with the radiating ambulacra, is now limited to the small flat area opposite the juncture of the stem with the calyx; and whether it stretches out to form long arms, or is more compact, so as to close the calyx like a cup, it seems in either case to form a flower-like crown. In these groups of Echinoderms the interambulacral plates are absent; there are no rows of plates of a different kind alternating with the ambulacral ones, as in the Sea-Urchins and the Star-Fishes, but the ab-oral region closes immediately upon the ambulacra.

It seems a contradiction to say, that, though these Crinoids were the only representatives of their Class in the early geological ages, while it includes five Orders at the present time, Echinoderms were as numerous and various then as now. But, paradoxical as it may seem, this is nevertheless true, not only for this Class, but for many others in the Animal Kingdom. The same numerical proportions, the same richness and vividness of conception were manifested in the early creation as now; and though many of the groups were wanting that are most prominent in modern geological periods, those that existed were expressed in such endless variety that the Animal Kingdom seems to have been as full then as it is to-day. The Class of the Echinoderms is one of the most remarkable instances of this. In the Silurian period, the Crinoids stood alone; there were neither Ophiurans, Asteroids, Echinoids, nor Holothurians; and yet in one single locality, Lockport, in the State of New York, over an area of not more than a few square miles, where the Silurian deposits have been carefully examined, there have been found more different Species of Echinoderms than are living now along our whole Atlantic coast from Maine to Florida.

There is nothing more striking in these early populations of the earth than the richness of the types. It would seem as if, before the world was prepared for the manifold existences that find their home here now, when organic life was limited by the absence of many of the present physical conditions, the whole wealth of the Creative Thought lavished itself upon the forms already introduced upon the globe. After thirty years' study of the fossil Crinoids, I am every day astonished by some new evidence of the ingenuity, the invention, the skill, if I may so speak, shown in varying this single pattern of animal life. When one has become, by long study of Nature, in some sense intimate with the animal creation, it is impossible not to recognize in it the immediate action of thought, and even to specialize the intellectual faculties it reveals. It speaks of an infinite power of combination and analysis, of reminiscence and prophecy, of that which has been in eternal harmony with that which is to be; and while we stand in reverence before the grandeur of the Creative Conception as a whole, there breaks from it such lightness of fancy, such richness of invention, such variety and vividness of color, nay, even the ripple of mirthfulness,—for Nature has its humorous side also,—that we lose our grasp of its completeness in wonder at its details, and our sense of its unity is clouded by its marvellous fertility. There may seem to be an irreverence in thus characterizing the Creative Thought by epithets which we derive from the exercise of our own mental faculties; but it is nevertheless true, that, the nearer we come to Nature, the more does it seem to us that all our intellectual endowments are merely the echo of the Almighty Mind, and that the eternal archetypes of all manifestations of thought in man are found in the Creation of which he is the crowning work.

In no group of the Animal Kingdom is the fertility of invention more striking than in the Crinoids. They seem like the productions of one who handles his work with an infinite ease and delight, taking pleasure in presenting the same thought under a thousand different aspects. Some new cut of the plates, some slight change in their relative position is constantly varying their outlines, from a close cup to an open crown, from the long pear-shaped oval of the calyx in some to its circular or square or pentagonal form in others. An angle that is simple in one projects by a fold of the surface and becomes a fluted column in another; a plate that was smooth but now has here a symmetrical figure upon it drawn in beaded lines; the stem which is perfectly unbroken in one, except by the transverse divisions common to them all, in the next puts out feathery plumes at every such transverse break. In some the plates of the stem are all rigid and firmly soldered together; in others they are articulated upon each other in such a manner as to give it the greatest flexibility, and allow the seeming flower to wave and bend upon its stalk. It would require an endless number of illustrations to give even a faint idea of the variety of these fossil Crinoids. There is no change that the fancy can suggest within the limits of the same structure that does not find expression among them. Since I have become intimate with their wonderful complications, I have sometimes amused myself with anticipating some new variation of the theme, by the introduction of some undescribed structural complication, and then seeking for it among the specimens at my command, and I have never failed to find it in one or other of these ever-changing forms.

The modern Crinoid without stem, or the Comatula, though agreeing with the ancient in all the essential elements of structure, differs from it in some specific features. It drops its stem when full-grown, though the ab-oral region still remains the predominant part of the body and retains its cup-like or calyx-like form. The Comatulae are not abundant, and though represented by a number of Species, yet the type as it exists at present is meagre in comparison to its richness in former times. Indeed, this group of Echinoderms, which in the earliest periods was the exponent of all its kind, has dwindled gradually, in proportion as other representatives of the Class have come in, and there exists only one species now, the Pentacrinus of the West Indies, which retains its stem in its adult condition. It is a singular fact, to which I have before alluded, and which would seem to have especial reference to the maintenance of the same numeric proportions in all times, that, while a Class is represented by few types, those types are wonderfully rich and varied, but in proportion as other expressions of the same structure are introduced, the first dwindle, and, if they do not entirely disappear, become at least much less prominent than before.

[Illustration: Ophiuran; showing one ray from the oral side.]

There remain only two other Orders to be considered, the Ophiurans and the Holothurians. The Ophiurans approach the Crinoids more nearly than any other group of Echinoderms, and in our classifications are placed next above them. In them the ab-oral region, which has such a remarkable predominance in the Crinoid, has become depressed; it no longer extends into a stem, nor does it even rise into the calyx-like or cup-like projection so characteristic of the Crinoids,—though, when the animal is living, the ab-oral side of the disk is still quite convex. The disk in the Ophiurans is small in comparison to the length of the arms, and perfectly circular; it does not merge gradually in the arms as in the Star-Fish, but the arms start abruptly from its periphery. In these, as in the Crinoids, the interambulacral plates are absent, and the interambulacral spaces are filled by an encroachment of the ab-oral region upon them. There is an infinite variety and beauty both of form and color in these Sea-Stars. The arms frequently measure many times the diameter of the whole disk, and are so different in size and ornamentation in the different Species that at first sight one might take them for animals entirely distinct from each other. In some the arms are comparatively short and quite simple,—in others they are very long, and may be either stretched to their full length or partly contracted to form a variety of graceful curves; in some they are fringed all along the edges,—in others they are so ramified that every arm seems like a little bush, as it were, and, intertwining with each other, they make a thick network all around the animal. In the geological succession, these Ophiurans follow the Crinoids, being introduced at about the Carboniferous period, and perhaps earlier. They have had their representatives in all succeeding times, and are still very numerous in the present epoch.

To show the correspondence of the Holothurians with the typical formula of the whole class of Echinoderms, I will return to the Sea-Urchins, since they are more nearly allied with that Order than with any of the other groups. We have seen that the Sea-Urchins approach most nearly to the sphere, and that in them the oral region and the sides predominate so greatly over the ab-oral region that the latter is reduced to a small area on the summit of the sphere. In order to transform the Sea-Urchin into a Holothurian, we have only to stretch it out from end to end till it becomes a cylinder, with the oral region or mouth at one extremity, and the ab-oral region, which in the Holothurian is reduced to its minimum, at the other. The zones of the Sea-Urchin now extend as parallel rows on the Holothurian, running from one end to the other of the long cylindrical body. On account of their form, some of them have been taken for Worms, and so classified by naturalists; but as soon as their true structure was understood, which agrees in every respect with that of the other Echinoderms, and has no affinity whatever with the articulated structure of the Worms, they found their true place in our classifications.

[Illustration: Holothurian.]

The natural attitude of these animals is different from that of the other Echinoderms: they lie on one side, and move with the oral opening forward, and this has been one cause of the mistakes as to their true nature. But when we would compare animals, we should place them, not in the attitude which is natural to them in their native element, but in what I would call their normal position,—that is, such a position as brings the corresponding parts in all into the same relation. For instance, the natural attitude of the Crinoid is with the ab-oral region downward, attached to a stem, and the oral region or mouth upward; the Ophiuran turns its oral region, along which all the suckers or ambulacra are arranged, toward the surface along which it moves; the Star-Fish does the same; the Sea-Urchin also has its oral opening downward; but the Holothurian moves on one side, mouth foremost, as represented in the adjoining wood-cut, dragging itself onward, like all the rest, by means of its rows of suckers. If, now, we compare these animals in the various attitudes natural to them, we may fail to recognize the identity of parts, or, at least, it will not strike us at once. But if we place them all—Holothurian, Sea-Urchin, Star-Fish, Ophiuran, and Crinoid—with the oral or mouth side downward, for instance, we shall see immediately that the small area at the opposite end of the Holothurian corresponds to the area on the top of the Sea-Urchin; that the upper side of the Star-Fish is the same region enlarged; that, in the Ophiuran, that region makes one side of the small circular disk; while in the Crinoid it is enlarged and extended to make the calyx-like projection and stem. In the same way, if we place them in the same attitude, we shall see that the long, straight rows of suckers along the length of the Holothurian, and the arching zones of suckers on the spherical body of the Sea-Urchin, and the furrows with the suckers protruding from them along the arms of the Star-Fish and Ophiuran, and the radiating series of pores from the oral opening in the Crinoid are one and the same thing in all, only altered somewhat in their relative proportion and extent. Around the oral opening of the Holothurian there are appendages capable of the most extraordinary changes, which seem at first to be peculiar to these animals, and to have no affinity with any corresponding feature in the same Class. But a closer investigation has shown them to be only modifications of the locomotive suckers of the Star-Fish and Sea-Urchin, but ramifying to such an extent as to assume the form of branching feelers. The little tufts projecting from the oral side in the Sea-Urchins, described as gills, are another form of the same kind of appendage.

The Holothurians have not the hard, brittle surface of the other Echinoderms; on the contrary, their envelope is tough and leathery, capable of great contraction and dilatation. No idea can be formed of the beauty of these animals either from dried specimens or from those preserved in alcohol. Of course, in either case, they lose their color, become shrunken, and the movable appendages about the mouth shrivel up. One who had seen the Holothurian only as preserved in museums would be amazed at the spectacle of the living animal, especially if his first introduction should be to one of the deep, rich crimson-colored species, such as are found in quantities in the Bay of Fundy. I have seen such an animal, when first thrown into a tank of sea-water, remain for a while closely contracted, looking like a soft crimson ball. Slowly, almost imperceptibly, as it becomes accustomed to its new position, it begins to elongate; the fringes creep softly out, spreading gradually all their ramifications, till one end of the animal seems crowned with feathery, crimson sea-weeds of the most delicate tracery. It is much to be regretted that these lower marine animals are not better known. The plumage of the tropical birds, the down on the most brilliant butterfly's wing, are not more beautiful in coloring than the hues of many Radiates, and there is no grace of motion surpassing the movements of some of them in their native element. The habit of keeping marine animals in tanks is happily growing constantly more popular, and before long the beauty of these inhabitants of the ocean will be as familiar to us as that of Birds and Insects. Many of the most beautiful among them are, however, difficult to obtain, and not easily kept alive in confinement, so that they are not often seen in aquariums.

Having thus endeavored to sketch each different kind of Echinoderm, let us try to forget them all in their individuality, and think only of the structural formula that applies equally to each. In all, the body has three distinct regions, the oral, the ab-oral, and the sides; but by giving a predominance to one or other of these regions, a variety of outlines characteristic of the different groups is produced. In all, the parts radiate from the oral opening, and join in the ab-oral region. In all, this radiation is accompanied by rows of suckers following the line of the diverging rays. It is always the same structure, but, endowed with the freedom of life, it is never monotonous, notwithstanding its absolute permanence. In short, drop off the stem of the Crinoid, and depress its calyx to form a flat disk, and we have an Ophiuran; expand that disk, and let it merge gradually in the arms, and we have a Star-Fish; draw up the rays of the Star-Fish, and unite them at the tips so as to form a spherical outline, and we have a Sea-Urchin; stretch out the Sea-Urchin to form a cylinder, and we have a Holothurian.

And now let me ask,—Is it my ingenuity that has imposed upon these structures the conclusion I have drawn from them?—have I so combined them in my thought that they have become to me a plastic form, out of which I draw a Crinoid, an Ophiuran, a Star-Fish, a Sea-Urchin, or a Holothurian at will? or is this structural idea inherent in them all, so that every observer who has a true insight into their organization must find it written there? Had our scientific results anything to do with our invention, every naturalist's conclusions would be colored by his individual opinions; but when we find all naturalists converging more and more towards each other, arriving, as their knowledge increases, at exactly the same views, then we must believe that these structures are the Creative Ideas in living reality. In other words, so far as there is truth in them, our systems are what they are, not because Aristotle, Linnaeus, Cuvier, or all the men who ever studied Nature, have so thought and so expressed their thought, but because God so thought and so expressed His thought in material forms when He laid the plan of Creation, and when man himself existed only in the intellectual conception of his Maker.

LYRICS OF THE STREET

II

THE WEDDING

In her satin gown so fine
Trips the bride within the shrine.
Waits the street to see her pass,
Like a vision in a glass.
Roses crown her peerless head:
Keep your lilies for the dead!

Something of the light without
Enters with her, veiled about;
Sunbeams, hiding in her hair,
Please themselves with silken wear;
Shadows point to what shall be
In the dim futurity.

Wreathe with flowers the weighty yoke
Might of mortal never broke!
From the altar of her vows
To the grave's unsightly house
Measured is the path, and made;
All the work is planned and paid.

As a girl, with ready smile,
Where shall rise some ponderous pile,
On the chosen, festal day,
Turns the initial sod away,
So the bride with fingers frail
Founds a temple or a jail,—

Or a palace, it may be,
Flooded full with luxury,
Open yet to deadliest things,
And the Midnight Angel's wings.
Keep its chambers purged with prayer:
Faith can guard it, Love is rare.

Organ, sound thy wedding-tunes!
Priest, recite the sacred runes!
Hast no ghostly help nor art
Can enrich a selfish heart,
Blessing bind 'twixt greed and gold,