Popular Science Monthly/Volume 1/August 1872/The Balance of Life in the Aquarium
WHEN man looks upon Nature, he sees everywhere the records of death's work among the representatives of creative energy. The stratified rocks are but the tombstones in the great graveyard of the world; they cover the bones of a million generations, and their inscription is, "The dust we tread upon was once alive." If the infusion of life into countless forms, each in itself perfect, needed nothing less than Almighty power, it needed Almighty power too to complete the scheme in the institution of dissolution; and the grim king of terrors, before whom the bee and the sparrow tremble, perhaps, not less than man, became co-worker with God by a wise and beneficent appointment; and so the orders of being began, and have to this hour continued, as a series of dissolving views, in which there is no hiatus, but only change; no shifting of the focus or the screen, no aberration or intermission of the source of light, but an unending variety in the pictures. We know not how other worlds may fare, but this we know, that here death supplies from every extinguished picture the colors with which the next are painted, and we live—man and brute—on the débris of the past.
I see all this and more in the aquarium; it teaches me lessons in physics, and, I trust, also teaches me that the moral and spiritual truths of the universe may be illustrated, sometimes explained, by a patient study of the commonest things. The aquarium is a world in little; it sustains itself. For the moment, I put aside the law of gravity as a universal law, and the presence of the atmosphere as a universal thing, and I call it a world, needing no aid, for its continuance and the perfect adjustment of its balance of power, from external things. I take a vessel of glass, a few pebbles, a few pieces of sandstone-rock, and a sufficiency of water, and to that I commit my fishes and insects, and say, "There is your world; the order of Nature is such that you may henceforth live and die without human interference." I say nothing here of the details of management; I am looking for instruction in the laws of life and death.
The two requisites of animal life, food and air, must be generated in this world, or it ceases to instruct me; yet the water contains but little of each, and whence is its supply to come? God has ordained such a wealth of organic forms that, wherever the conditions of life are found, life takes possession of the spot, whether it be the bottom of the ocean, the dripping roof of a cave, the expanse of the viewless air, or the mimic lake I call an aquarium. Forthwith the dead stones become alive with greenness, the glass walls assume the semblance of a meadow, the milky hue of the water disappears as the earthy particles it held in solution subside, and the light that streams through it takes a tint of greenness. There is an order of vegetation appointed to occupy such sites, and almost every non-metallic, and some metallic substances too, become speedily coated with conferva?, when their surfaces are kept moist a sufficient length of time. Were it not so, the inhabitants of my world must perish; and to prove the fact I try an experiment. I place some fishes in a clean vessel of water, without pebbles and without rock; the moment the first dim bronzy speck appears, I rub it off the glass, and so thwart the course of Nature. The fishes soon exhaust the water of its oxygen, and though the water attempts to renew its supplies by absorption from the atmosphere, the compensation is too slow, the fishes come gasping to the surface, and in a short while perish.
Even then I learn something from their death if I leave the vessel in the hands of Nature. Death has no sooner spread his black banner over my household gods than life of another kind arises to confound him, and the microscope reveals to me myriads of animals and plants, and organisms that seemingly occupy an intermediate place between the two great kingdoms, rioting upon the wreck that death has made. My half-dozen dead fishes have given birth to existences numerous as the stars in heaven, or as the sand upon the sea-shore, innumerable. While these devour the banquet death has spread for them, while forests of confervoid threads rise in silken tufts like microscopic savannas, Nature is passing portions of the ichthyic débris through her laboratory, and the very source of life for which they pined and perished—oxygen—is poured in in large measure, and the corruption is quickly changed to sweetness. Of the once sportive fishes some portions have become air, other portions have become water, but the chief of their bulk lives already in the vegetation which hides their grave, and the moving throng with which that vegetation is peopled. God's purpose, in the working of the laws in obedience to which these changes have taken place, is manifestly to keep ever true that balance of life and death of which He holds the beam in His own hands.
But my aquarium which has not thus been interfered with presents already a similar scene of life and bustle. When first supplied, the milky-looking water was abundantly full of gaseous matters, and every part of the rough rockwork was, for a time studded with silvery globules. The fishes consumed all that in the process of breathing. As the water passed through their gills, the oxygen was absorbed; that oxygen, by a process of refined chemistry, and perhaps by the help of iron also, gave their gills a bright-red color, gave their blood its red color too, and, by other processes not less refined, sustained he balance of life's functions within them, for without it they must perish. We believe that not the airiest particle of earth, atmosphere, or water, nor the most minute globule of condensed moisture, nor the most infinitesimal point of meteoric dust, can ever be lost, at least during Time, from the fabric of the universe. My fishes tell me that the oxygen they absorb from the water they again return to it, but in another form. They inspire oxygen and expire carbonic acid, just as a man does, and every other living creature that moveth upon the face of all the earth. Is it within the reach of human power, even when reason, imagination, and fancy combine together as a bold triad to look direct upon a fact, to appreciate that principle of terrestrial life by which animal and vegetable organisms reciprocally labor to maintain the balance of atmospheric purity? The carbonic acid given off by the animal is poison to it, if it accumulate while the supply of oxygen is cut short. It was carbonic acid as much as absence of oxygen that killed our fishes just now, for, though inhabitants of water, they were not the less suffocated. Therefore I see why, in the tank that has been left alone, plants have cast anchor on the glass walls, the brown pebbles, and the gray blocks of sandstone-rock. My fishes breathe and breathe. If their numbers are properly proportioned to the area they occupy, they will never exhaust the water of oxygen, never render it fetid with carbonic acid, so long as one necessity of vegetable life—light—is allowed to use its active influence to paint the plants green, even as oxygen gives a sanguine hue to the gills or lungs of the fishes. To those plants, the carbonic acid, which the fishes expire day and night, is as essential as oxygen is to the animal economy, and thus, without introducing a single scrap of any living plant, the balance is sustained, and death seems to be kept at a distance. If at first I threw in a tuft of callitriche or anacharis, or any other true aquatic vegetable, oxygen would be supplied abundantly; and in practice it might be well to begin so, because some little time elapses ere the seeds of the microscopic forest, the tops of whose trees present to the eye but a felt-like coating of superficial greenness, are developed into true plants; though with a fair amount of indirect daylight, and at certain seasons of the year, a few hours suffice to set the vegetative process, with all its proper consequences, in full action. Many of the readers of this paper will call to mind the aquarium that stands in my entrance-hall. It contains twenty fishes, large and small, and not a single scrap of vegetation except what has been developed in situ by spontaneous generation. It is three years since that was fitted and stocked, and committed to the management of Nature, with the sole exception of the external aid afforded by regular supplies of food for its inmates, which need not be taken account of, now that we are considering it as a world in which the balance of life and death is sustained by the operation of principles ordained by the Creator.
It is when we leave the principles and attempt to classify the details of the scheme that we become bewildered. The smooth revolution of the fly-wheel and the noiseless oscillation of the piston convince the unprofessional observer of a great engine that mechanical motions are possessed of poetry; but, if he would analyze the relations of the cog-wheels, the indications of the "governor," the "gauge," and the pressure-valve, he must descend to hard facts, and forget for a while the sublime suggestions of a system of mechanism that throbs like a living creature. Admit a full glare of summer sun to the aquarium, and forth-with the water loses its pellucid fluidity, and becomes deeply tinged throughout of a dull green, as if some pigment had been dissolved in it. Instead of plants attached to stones and glass only, and animals that float unseen, the whole of the water is occupied by visible masses of animal and vegetable life; and, if the fishes suffer, it will be from undue heat, not from the addition to the element in which they live of this new mass of being. Shut out the sunshine, let the fresh air play over the surface of the water, let moderate daylight stream through it as before, and speedily the green fog clears away, the water again becomes transparent, and the balance is restored. Monas, euglena, uvella, cryptomonas, gonium, and other wondrous infusoria, may be detected as constituents of the cloudy mass while it lasts, called into being because the conditions of the tank were such as they required, as if life in embryo were everywhere locked up until the moment came for its liberation, and some particular circumstance was the talisman to set it free or, if we consider created forms to be marshalled in grand procession, may we not expect that every tribe will hurry to its appointed place the instant that a door is opened?
Microscopists have long been at war, but without bloodshed, as to the place to be assigned to certain organic forms which are hidden from our common eyesight. While the war goes on as to whether desmidiaeæ and diatomaceæ be animal or vegetable, or both, let facts suffice us here in the study of the aquarium. Does an animal exhale carbonic acid? Yes. Well, here are plants or animals, concerned in keeping up the balance, which exhale oxygen, and their name is legion. Volvox globator and the bacillariæ labor as hard to supply the fishes with the life-sustaining gas as do the silken threads of verdure that line the glass like a carpet. Is the possession of starch a distinctive feature of the vegetable? Perhaps so. Truly here are desmidiaeæ that contain starch, and, if I make the possession of cilia the test for assigning certain forms to the animal kingdom, I find in the aquarium spores of algae furnished with them. Motion I know to be no test, because algæ-spores dance through the water gayly till they find a resting-place, and, when the aquarium was first filled, it was by dancing they at last found where to pitch their tents, and cease their nomad wanderings. But they all work together to sustain the balance, and the law of "give and take" prevails among them—the stentor devours the oscillatorise, rotatoria, and monads, and the hydras swallow all; every darting speck is a tomb wherein some smaller speck of life is to be buried, and life thus prospers on the decay it is itself undergoing.
But all this while a fine deposit slowly settles among the pebbles, which form the lower stratum of this watery world. Between the stones a fine alluvial silt collects and thickens. The first frost, sufficiently severe to touch the tank, causes the whole green coating to peel off from the glass and rock, and, while this subsides, to add to the thickness of the alluvium—how slightly, and yet how sufficiently for an example of Nature's working!—a new growth commences, and that balance is restored. Do you not see that the chief teaching of geology—the piling of stratum upon stratum, the conversion of disrupted rock and decayed plant and animal into rock again—is here exemplified in the history of a domestic toy, which contains already one example of stratification in the silence of watery submergence? A tank which has been fitted with loam, pebbles, and plants of the brook and river, will, if left undisturbed for three years, be in this state. Those plants will all have decayed, but there will be an abundant spontaneous vegetation. The accumulations of that short period will have settled into a close mass, almost as hard as stone; and if fishes have died in the mean time, and have not been removed, their bones will be found overlaid with hardened mud, just as we find them in the old red sandstone, or the chalk, or the carboniferous rocks, and shall we not call them our own fossils? See again in this case in which death has been very busy (for plants of large growth soon perish in the absence of sunshine, and occasional attendant accidents will carry off some of the finny pets), how life has been ^dually active on the other side, for such an aquarium will be a hundred times richer in those spontaneous growths we have already spoken of, and visible forms of infusoria and true zoophytes will abound, and every class will be more fully represented, down even to the twilight monad.
Though this paper must have an end, there is no end to the teaching of the aquarium. It is a watery microcosm of living and dead wonders, and we need not marvel that the balance of life and death may be observed in its succession of changes, because all the physical forces of the universe are locked up within a single bead of dew, and all the functions of organic creation are comprised in the economy of a monas termo. If God so ordains that life shall be constantly soaring from the tomb, if the story of the Phoenix ceases to be a fable, need man, the victim of doubts and fears, ever fail in his trust of that blessed promise, that "this mortal shall put on immortality, and this corruptible shall put on incorruption?" Science may fix his mind on the appreciation of God's wisdom and power as he reads the handwriting of the Almighty in Nature, but through faith in another revelation must we hope to exclaim, triumphantly, "O death, where is thy sting? O grave, where is thy victory?" Or, to pass from divine to human consolations, we may take up the apostrophe of the great Raleigh, and say: "O eloquent, just, and mighty Death! what none have dared, thou hast done; what none have attempted, thou hast accomplished; thou hast gathered all the might, majesty, and meanness of mankind, and hast covered them with these two words, hic jacet" Nature's children have a dread of death, but Nature herself is in friendly compact with the master of silence. If the types which are the ideas of God have survived from the oldest rocks to this present hour, will not the spirit which lives on ideas, and evolves them as the aquarium evolves its throng of animalcules, live forever? It is not hard to believe with Tennyson—
"That nothing walks with aimless feet,
That not one life shall be destroyed,
"The pile" will be complete when God's purpose is fulfilled in man, to whom it is given to hope after eternal life, and with eyes of faith to pierce through the veil, and behold the wondrous things of eternity.—Recreative Science.