The Aquarium

THE sumptuous abode of Licinius Crassus echoes with his sighs and groans. His children and slaves respect his profound sorrow, and leave him with intelligent affection to solitude, — that friend of great grief, so grateful to the afflicted soul, because tears can flow unwitnessed. Alas ! the favorite sea-eel of Crassus is dead, and it is uncertain whether Crassus can survive it !

This sensitive Roman caused his beloved fish to be buried with great magnificence : he raised a monument to its memory, and never ceased to mourn for it. So say Macrobius and Ælian.

This man, we are told, who displayed so little tenderness towards his servants, had an extraordinary weakness concerning his fine sea-eels. He passed his life beside the superb fish-pond, where he lovingly fattened them from his own hand. Nor was his fondness for pisciculture exceptional in his times. The fishpond, to raise and breed the finest varieties offish, was as necessary an adjunct to a complete establishment as a barn-yard or hen-coop to a modern farmer or rural gentleman. Wherever there was a wellappointed Roman villa, it contained a piscina ; while many gardens near the sea could boast also a vivarium, which, in this connection, means an oyster-bed.

Fish-ponds, of course, varied with the wealth, the ingenuity, and the taste of their owners. Many were of vast size and of heterogeneous contents. The costly Murœna, the carp, the turbot, and many other varieties, sported at will in the great inclosures prepared for them. The greater part of the Roman emperors were very fond of sea-eels. The greedy Vitellius, growing tired of this dish, would at last, as Suetonius assures us, eat only the soft roe ; and numerous vessels ploughed the seas in order to obtain it for him. The family of Licinius took their surname of Muræna from these fish, in order thus to perpetuate their silly affection for them. The love of fish became a real mania, and the Murœna Helena was worshipped.

Hortensius, who possessed three splendid country-seats, constructed in the grounds of his villa at Bauli a fish-tank so massive that it has endured to the present day, and so vast as to gain for it even then the name of Piscina Mirabilis. It is a subterraneous edifice, vaulted, and divided by four rows of arcades and numerous columns, — some ten feet deep, and of very great extent. Here the largest fishes could be fattened at will; and even the mighty sturgeon, prince of good-cheer, might find ample accommodations.

Lucullus, that most ostentatious of patricians, and autocrat of bons-vivants, had a mountain cut through in the neighborhood of Naples, so as to open a canal, and bring up the sea and its fishes to the centre of the gardens of his sumptuous villa. So Cicero well names him one of the Tritons of fish-pools. His countryseat of Pausilypum resembled a village rather than a villa, and, if of less extent, was more magnificent in luxury than the gigantic villa of Hadrian, near Tivoli. Great masses of stone-work are still visible, glimmering under the blue water, where the marble walls repelled the waves, and ran out in long arcades and corridors far into the sea. Inlets and creeks, which wear even now an artificial air, mark the site of piscinœ and refreshing lakes. Here were courts, baths, porticoes, and terraces, in the villa urbana, or residence of the lord, — the villa rustica for the steward and slaves, — the gallinarium for hens, — the apiarium for bees, — the suile for swine, — the villa fructuaria, including the buildings for storing corn, wine, oil, and fruits, — the hortus, or garden, — and the park, containing the fish-pond and the vivarium. Statues, groves, and fountains, pleasureboats, baths, jesters, and even a small theatre, served to vary the amusements of the lovely grounds and of the tempting sea.

But it was not to be supposed that men satiated with the brutal shows of the amphitheatre, even if enervated by their frequentation of the Suburra, could, on leaving the city, be always content with simple pleasures, rural occupations, or pleasure-sails. Habit demanded something more exciting; and the ready tragedy of a fish-pond filled with ravenous eels fed upon human flesh furnished the needed excitement. For men blasé with the spectacles of lions and tigers lacerating the bestiarii, it was much more exciting to witness a swarm of sea-eels tearing to pieces an awkward or rebellious slave. Vedius Pollio, a Roman knight of the highest distinction, could find nothing better to do tor his dear Murœnœ than to throw them slaves alive; and he never failed to have sea-eels served to him after their odious repast, says Tertullian. It is true, these wretched creatures generally deserved this terrible punishment; for instance, Seneca speaks of one who had the awkwardness to break a crystal vase while waiting at supper on the irascible Pollio.

Pisciculture was carried so far that fishponds were constructed on the roofs of houses. More practical persons conducted a stream of river-water through their dining-rooms, so that the fish swain under the table, and it was only necessary to stoop and pick them out the moment before eating them; and as they were often cooked on the table, their perfect freshness was thus insured. Martial (Lib. X,, Epigram. XXX., vv. 16-25) alludes to this custom, as well as to the culture and taming of fish in the piscina.

“ Nec seta longo quærit in mari prædam,
Sed e cubiclo lectuleque jactatam
Spectatus alte lineam trahit piscis.
Si quando Nereus sent it Æoli regnutn,
Ridet procellas tuta de suo mensa.
Piscina rhombum pascit et lupos vernns,
Natat ad magistrum delicata muræna;
Nomenculator mugilem citat notum
Et adesse jussi prodeunt senes mulli."

It having been remarked that the red mullet passed through many changes of color in dying, like the dolphin, fashion decreed that it should die upon the table. Served alive, inclosed in a glass vessel, it was cooked in the presence of the attentive guests, by a slow fire, in order that they might gloat upon its sufferings and expiring hues, before satisfying their appetites with its flesh.

It will not surprise us to learn that the eminent gourmand Apieius offered a prize to the inventor of a new sauce made of mullets’ livers.

But we may remark, that fish, like all other natural objects, were studied by the ancients only to pet or to eat. All their views of Nature were essentially selfish; none were disinterested, reverential, deductive, or scientific. Nature ministered only to their appetites, in her various kinds of food, — to their service, in her beasts of burden, — or to their childish or ferocious amusement, with talking birds, as the starling, with pet fish, or with pugnacious wild beasts. There was no higher thought. The Greeks, though fond of flowers, and employing them for a multitude of adornments and festive occasions entirely unequalled now, yet did not advance to their botanical study or classification. The Roman, if enamored of the fine arts, could see no Art in Nature. There was no experiment, no discovery, and but little observation. The whole science of Natural History, which has assumed such magnitude and influence in our times, was then almost entirely neglected.

And yet what an opportunity there was for the naturalist, had a single enthusiast arisen ? All lands, all climes, and all their natural productions were subservient to the will of the Emperor. The orb of the earth was searched for the roe of eels or the fins of mullets to gratify Cæsar. And the whole world might have been explored, and specimens deposited in one gigantic museum in the Eternal City, at the nod of a single individual. But the observer, the lover of Nature, was wanting; and the whole world was ransacked merely to consign its living tenants to the vivaria, and thence to the fatal arena of the amphitheatre. Yet even here the naturalist might have pursued his studies on individuals, and even whole species, both living and dead, without quitting Rome. The animal kingdom lay tributary at his feet, but served only to satiate his appetite or his passions, and not to enrich his mind.

So, again, Rome’s armies traversed the globe, and her legions were often explorers of hitherto unknown regions. But no men of science, no corps of savans was attached to her cohorts, to march in the footsteps of conquest and gather the fruits of victory to enrich the schools. Provinces were devastated, great cities plundered, nations made captive, and all the masterpieces of Art borne off to adorn Rome. But Nature was never rifled of her secrets; nor was discovery carried beyond the most material things. The military spirit stifled natural science.

There were then, to be sure, no tendencies of thought to anything but war, pleasure, literature, or art. There was comparatively no knowledge of the physical sciences, whose culture Mr. Buckle has shown to have exerted so powerful an influence on civilization. The convex lens — as since developed into the microscope, the giver of a new world to man — was known to Archimedes only as an instrument to burn the enemy’s fleet.

Modern pisciculture in some measure imitates, although it does not rival the ancient. Many methods have been devised in France and England of breeding and nurturing the salmon, the trout, and other valuable fish, which are annually becoming more scarce in all civilized countries. But all this is on a far different principle from that pursued at Rome. We follow pisciculture from necessity or economy, because fish of certain kinds are yearly dying out, and to produce a cheap food; but the Romans followed it as a luxury, or a childish amusement, alone. And although our aldermen may sigh over a missing Chelonian, as Crassus for his deceased eel, or the first salmon of the season bring a fabulous price in the market, yet the time has long passed when the gratification of appetite is alone thought of in connection with Nature. We know that living creatures are to be studied, as well as eaten; and that the faithful and reverent observation of their idiosyncrasies, lives, and habits is as healthful and pleasing to the mind as the consumption of their flesh is wholesome and grateful to the body. The whole science of Zoology has arisen, with its simple classifications and its vast details. The vivaria of the Jardin des Plantes rival those of the Colosseum in magnitude, and excel them in object. Nature is ransacked, explored, and hunted down in every field, only that she may add to the general knowledge. Museums collect and arrange all the types of creative wisdom, from the simple cell to man. Science searches out their extinct species and fossil remains, and tells their age by Geology. The microscope pursues organic matter down into an infinity of smallness, proportionately as far as the telescope traces it upwards in the infinity of illimitable space. Last of all, though not till long after the earth and the air had been seemingly exhausted, the desire of knowledge began to push its way into the arcana of the sea,—that hidden half of Nature, where are to be found those wonders described by Milton at the Creation, — where, in obedience to the Divine command,

“ Be fruitful, multiply, and in the seas
And lakes and running streams the waters fill,.....
Forthwith the sounds and seas, each creek and bay,
With fry innumerable swarm, and shoals
Of fish, that with their fins and shining scales
Glide under the green wave in sculls that oft
Bank the mid sea: part single or with mate
Graze the sea-weed, their pasture, and through groves
Of coral stray, or sporting with quick glance
Show to the sun their waved coats dropt with gold,
Or in their pearly shells at ease attend
Moist nutriment, or under rocks their food
In jointed armor watch.”

But no means were at hand to pursue these unknown creatures to their unknown residences, and to observe their manners when at home. Single, withered, and often mutilated specimens of minute fish, mollusks, or radiata, in the museum, alone illustrated the mysteries of the deep sea. Fish, to be sure, could be kept for longer or shorter periods in globes of glass filled with water; but the more delicate creatures inevitably perished soon after their removal from their mysterious abodes. Such a passionate desire to “search Nature and know her secrets” finally originated the idea of the Aquarium.

The term vivarium was used amor g the ancients to signify many things, — from the dens of the wild animals which opened under the Colosseum, to an oyster-bed ; and so now it may mean any collection of living creatures. Hence it could convey no distinct idea of a marine collection such as we propose to describe. The term aqua was added to express the watery element; but the compound aqua - vivarium was too clumsy for frequent employment, and the abbreviated word aquarium has come into general


Thus the real Aquarium is a watergarden and a menagerie combined,— and aims to show life beneath the waters, both animal and vegetable, in all the domestic security of its native home, and in all the beauty, harmony, arid nice adaptation of Nature herself. It is no sudden discovery, but the growth of a long and patient research by naturalists.

“ What happens, when we put half a dozen gold-fish into a globe ? The fishes gulp in water and expel it, at the gills. As it passes through the gills, whatever free oxygen the water contains is absorbed, and carbonic acid given off in its place; and in course of time, the free oxygen of the water is exhausted, the water becomes stale, and at last poisonous, from excess of carbonic acid. If the water is not changed, the fishes come to the surface and gulp atmospheric air. But though they naturally breathe air (oxygen) as we do, yet they are formed to extract it from the water; and when compelled to take air from the surface, the gills, or lungs, soon get inflamed, and death at last puts an end to their sufferings.

“ Now, if a fish-globe be not overcrowded with fishes, we have only to throw in a goodly handful of some water-weed,— such as the Callitriche, for instance,—and a new set of chemical operations commences at once, and it becomes unnecessary to change the water. The reason of this is easily explained. Plants absorb oxygen as animals do ; but they also absorb carbonic acid, and from the carbonic acid thus absorbed they remove the pure carbon, and convert it into vegetable tissue, giving out the free oxygen either to the water or the air, as the case may be. Hence, in a vessel containing water-plants in a state of healthy growth, the plants exhale more oxygen than they absorb, and thus replace that which the fishes require for maintaining healthy respiration. Any one who will observe the plants in an aquarium, when the sun shines through the tank, will see the leaves studded with bright beads, some of them sending up continuous streams of minute bubbles. These beads and bubbles are pure oxygen, which the plants distil from the water itself, in order to obtain its hydrogen, and from carbonic acid, in order to obtain its carbon.”1

Thus the water, if the due proportiou of its animal and vegetable tenants be observed, need never be changed. This is the true Aquarium, which aims to imitate the balance of Nature. By this balance the whole organic world is kept living and healthy. For animals are dependent upon vlie vegetable kingdom not only for all their food, but also for the purification of the air, which they all breathe, either in the atmosphere or in the water. The divine simplicity of this stupendous scheme may well challenge our admiration. Each living thing, animal or plant, uses what the other rejects, and gives back to the air what the other needs. The balance must be perfect, or all life would expire, and vanish from the earth.

This is the balance which we imitate in the Aquarium. It is the whole law of life, the whole scheme of Nature, the whole equilibrium of our organic world, inclosed in a bottle.

For the rapid evolution of oxygen by plants the action of sun-light is required. That evolution becomes very feeble, or ceases entirely, in the darkness of the night. Some authorities assert even that carbonic acid is given off during the latter period. So, too, they claim that there are two distinct processes carried on by the leaves of plants,—namely, respiration and digestion: that the first is analogous to the same process in animals; and that by it oxygen is absorbed from, and carbonic acid returned to the atmosphere, though to a limited degree : and that digestion consists in the decomposition of carbonic acid by the green tissues of the leaves under the stimulus of the light, the fixation of solid carbon, and. the evolution

Why carbonic acid is, to a limited degree, given off by the plant in the night, is merely because the vital process, or the fixation of carbon and evolution of oxygen, ceases when the light is withdrawn. The plant is only in a passive state. Ordinary chemical forces resume their sway, and the oxygen of the air combines with the newly deposited carbon to reproduce a little carbonic acid. But this must be placed to the account of decomposing, not of growing vegetation ; for by so much as plants grow, they decompose carbonic acid and give its oxygen to the air, or, in other words, purify the air.

It has been found by experiment, that every six pounds of carbon in existing plants has withdrawn twenty-two pounds of carbonic acid gas from the atmosphere, and replaced it with sixteen pounds of oxygen gas, occupying the same bulk. And when we consider the amount of carbon that is contained in the tissues of living, and of extinct vegetation also, in the form of peat and coal, we may have some idea of the vast body of oxygen which the vegetable kingdom has added to the atmosphere.

And it is also to be considered, that this is the only means we know of whereby free oxygen is given to supply the quantity constantly consumed in respiration, combustion, and other vast and endless oxygen-using processes. It follows, therefore, that animals are dependent upon plants for their pure oxygen, as well as for their food. But the vegetable kingdom might exist independently of the animal; since plants may derive enough carbon from the soil, enriched by the decaying members of their own race.

There is, however, one exception to the law that plants increase the amount of oxygen in the air. During flowering and fruiting, the stores of carbon laid up in the plant are used to support the process, and, combining with the oxygen of the air, both carbonic acid and heat are given off. This has been frequently proved. In large tropical plants, where an immense number of blossoms are crowded together, the temperature has risen twenty to fifty degrees above that of the surrounding air.

As most of the aquatic plants are cryptogamous, or producing by spores, and not by flowers, it seems probable that the evolution of carbonic acid and heat is much less in degree in them, and therefore less in the water than in the air. We may, therefore, venture to lay it down as a general principle, that plants evolve free oxygen in water, when in the sunlight, and remove the carbonic acid added to the water by the respiration of the animals.

But since this is a digestive or nutritive process, it follows that aquatic plants may derive much or all of their food from the water itself, or the carbon in it, in the same manner as the so-called airplant, which grows without soil, does from the air. It is true, at any rate, that, in the fresh-water aquarium, the river and brook plants need no soil but. pebbles ; and that the marine plants have no proper root, but are attached by a sort of sucker or foot-stalk to stones and masses of rock. It is very easy to see, then, how the aquarium may be made entirely selfsupporting ; and that, excepting for the larger carnivorous fish, who exhaust in a longer or shorter period the minute creatures on which they live, no external food is required.

A very simple experiment will prove the theory and practicability of the aquarium. In a glass jar of moderate size was placed a piece of Ulva latissima, or Sea-Lettuce, a broad-leaved, green, aquatic plant, and a small fish. The mouth was closed by a ground glass stopper. The jar was exposed to the light daily; the water was never changed ; nor was the glass stopper removed, excepting to feed the fish, once or twice a week, with small fragments of meat. At the end of eight months both remained flourishing : the fish was lively and active ; and the plant had more than half filled the bottle with fresh green leaves.

Any vessel that will hold water can, of course, be readily converted into an aquarium. But as we desire a clear view of the contents at all times, glass is the best material. And since glass globes refract the light irregularly and magnify and distort whatever is within them, we shall find an advantage in having the sides of the aquarium parallel and the form rectangular. As the weight of the aquarium, when filled with water, is enormous, — far more than we should at first imagine, — it follows that it must be capable of resisting pressure both from above and from within. The floor and stand, the frame and joints must be strong and compact, and the walls of plate or thick crown glass. The bottom should be of slate ; and if it is designed to attach arches of rock-work inside to the ends, they, too, must be of slate, as cement will not stick to glass. The frame should be iron, zinc, or well-turned wood ; the joints closed with white-lead putty; the front and back of glass. There is one objection to having the side which faces the light of transparent glass, and that is that it transmits too much glare of sunlight for the health of the animals. In Nature’s aquarium the light enters only from above ; and the fish and delicate creatures have always, even then, the shady fronds of aquatic plants or the shelter of the rocks,— as well as the power of seeking greater depths of water, where the light is less, — to protect themselves from too intense a sunshine. It is, therefore, sometimes advisable to have the window side of the aquarium made of glass stained of a green color. It is desirable that all aquarial tanks should have a movable glass cover to protect them from dust, impure gases, and smoke.

When we speak of an aquarium, we mean a vessel holding from eight to thirty gallons of water. Mr. Gosse describes his larger tank as being two feet long by eighteen inches wide and eighteen inches deep, and holding some twenty gallons. Smaller and very pretty tanks may be made fifteen inches long by twelve inches wide and twelve deep. Great varieties in form and elegance may be adapted to various situations.

There are two kinds of aquaria, the fresh-and the salt-water: the one fitted for the plants and animals of ponds and rivers; the other for the less known tenants of the sea. They are best described as the River and the Marine Aquarium, and they differ somewhat from each other. We shall speak first of the freshwater aquarium.

The tank being prepared, and wellseasoned, by being kept several weeks alternately full and empty, and exposed to the sun and air, so that all paint, oil, varnish, tannin, etc., may be wholly removed, the next thing is to arrange the bottom and to plant it. Some rough fragments of rock, free from iron or other metals that stain the water, may be built into an arch with cement, or piled up in any shape to suit the fancy. The bottom should be composed entirely of shingle or small pebbles, well washed. Common silver sand, washed until the water can be poured through it quite clear, is also suitable.

Mould, or soil adapted to ordinary vegetation, is not necessary to the aquatic plants, and is, moreover, worse than useless; since it necessitates the frequent changing of the water tor some time, in order to get rid of the soluble vegetable matter, and promotes the growth of Confervas, and other low forms of vegetation, which are obnoxious.

Aquatic plants of all kinds have been found to root freely and flourish in pebbles alone, if their roots be covered. The plants should be carefully cleared of all dead parts; the roots attached to a small stone, or laid on the bottom and covered with a layer of pebbles and sand.

The bottom being planted, the water may be introduced through a wateringpot, or poured against the side of the tank, so as to avoid any violent agitation of the bottom. The water should be pure and bright. River-water is best; spring-water will do, but must be softened by the plants for some days before the fishes are put in.

Sunshine is good for the tank at all seasons of the year. The freshrequires more than the salt-water aquarium. The amount of oxygen given off by the plants, and hence their growth and the sprightliness of the fishes, are very much increased while the sun is shining on them.

In selecting plants for the aquarium some regard is to be paid to the amount of oxygen they will evolve, and to their hardiness, as well as to their beauty. When it is desired to introduce the fishes without waiting long for the plants to get settled and to have given off a good supply of oxygen, there is no plant more useful than the Callitriche, or Brook Starwort. It is necessary to get a good supply, and pick off the green heads, with four or six inches only of stem; wash them clean, and throw them into the tank, without planting. They spread over the surface, forming a rich green ceiling, grow freely, and last for months. They are continually throwing out new roots and shoots, and create abundance of oxygen. Whenever desired, they can be got rid of by simply lifting them out.

The Vallisneria, or Tape-Grass, common in all our ponds, is essential to every fresh-water tank. It must be grown as a bottom-plant, and flourishes only when rooted. The Nitella is another pleasing variety. The Ranunculus aquatilis, or Water-Crowfoot, is to be found in almost every pond in bloom by the middle of May, and continues so into the autumn. It is of the buttercup family, and may be known as a white buttercup with a yellow centre. The floating leaves are fleshy; the lower ones finely cut. It must be very carefully washed, and planted from a good joint, allowing length enough of stem to reach the surface. Some of the blossom-heads may also be sprinkled over the surface, where they will live and bloom all through the summer. The Hydrocharis, or Frog's-Bit, and the Alisma, or WaterPlantain, are also easily obtained, hardy and useful, as well as pleasing. Many rarer and more showy varieties may be cultivated ; we have given only the most common and essential. All the varieties of Chara are interesting to the microscopist, as showing the phenomenon of the circulation of the sap, or Cyclosis.

Of the living tenants of the aquarium, those most interesting, as well as of the highest organization, are the fishes. And among fishes, the family of the Cyprinidœ are the best adapted to our purpose; for we must select those which are both hardy and tamable. Cyprinus gibelio, the Prussian Carp, is one of the best. It will survive, even if the water should accidentally become almost exhausted of oxygen. It may be taught, also, to feed from the hand. None of the carp are very carnivorous. Cyprinus auratus, or the Gold-fish, is one of the most ornamental objects in an aquarium. But the Minnow, C. phoxinus, is the jolliest little fish in the tank. He is the life of the collection, and will survive the severest trials of heat and cold. The Chub, a common tenant of our ponds, is also a good subject for domestication. The Tench and Loach are very interesting, but also very delicate. Among the spinyfinned fishes, the Sticklebacks are the prettiest, but so savage that they often occasion much mischief. For a vessel containing twelve gallons the following selection of livestock is among those recommended : Three Gold Carp, three Prussian Carp, two Perch, four large Loach, a dozen Minnows, six Bleak, and two dozen Planorbis. Some varieties of the Water-Beetles, or Water-Spiders, which the fishes do not eat, may also well be added. The Newt, too, is attractive and harmless.

All may go on well, and the water remain clear; but after the tank has been established several weeks, the inner sides of the glass will show a green tinge, which soon increases and interferes with the view. This is owing to the growth of a minute confervoid vegetation, which must be kept down. For this purpose the Snail is the natural remedy, being the ready scavenger of all such nuisances Snails cling to the sides, and clean away and consume all this vegetable growth. The Lymnea is among the most efficient, but unfortunately is destructive, by eating holes in the young fronds of the larger plants, and thus injuring their appearance. To this objection some other varieties of snail are not open. The Paludina and Planorbis are the only kinds which are trustworthy. The former is a handsome snail, with a bronze-tinted, globular shell; the latter has a spiral form. These will readily reduce the vegetation. And to preserve the crystal clearness of the water, some Mussels may be allowed to burrow in the sand, where they will perform the office of animated filters. They strain off matters held in suspension in the water, by means of their siphons and ciliated gills. With these precautions, a well-balanced tank will long retain all the pristine purity of Nature.

Specimens for the river aquarium may be readily obtained in almost any brook or pool, by means of the hand-net or dredge. It will be astonishing to see the variety of objects brought up by a successful haul. Small fish, newts, tadpoles, mollusks, water-beetles, worms, spiders, and spawn of all kinds will be visible to the naked eye; while the microscope will bring out thousands more of the most beautiful objects.

A very different style of appearance and of objects distinguishes the Salt-water or Marine Aquarium.

As the greater part of the most curious live stock of the salt-water aquarium live upon or near the bottom, so the marine tank should be more shallow, and allow an uninterrupted view from above. Marine creatures are more delicately constituted than fresh-water ones; and they demand more care, patience, and oversight to render the marine aquarium successful.

Sea-saml and pebbles, washed clean, form the best bottom for the salt-water aquarium. It must be recollected that many of the marine tenants are burrowers, and require a bottom adapted to their habits. Some rock-work is considered essential to afford a grateful shelter and concealment to such creatures as are timid by nature, and require a spot in which to hide: this is true of many fishes. Branches of coral, bedded in cement, may be introduced, and form beautiful and natural objects, on which plants will climb and droop gracefully.

Sea-water dipped from the open sea, away from the mouths of rivers, is, of course, the best for the marine aquarium. If pure, it will bear transportation and loss of time before being put into the tank. It may, however, not always be possible to get sea-water, particularly for the aquarium remote from the seaboard, and it is therefore fortunate that artificial sea-water will answer every purpose.

The composition of natural sea-water is, in a thousand parts, approximately, as follows: Water, 964 parts ; Common Salt, 27 ; Chloride of Magnesium, 3.6 ; Chloride of Potassium, 0.7 ; Sulphate of Magnesia, (Epsom Sails,) 2; Sulphate of Lime, 1.4; Bromide of Magnesium, Carbonate of Lime, etc., .02 to .03 parts. Now the Bromide of Magnesium, and Sulphate and Carbonate of Lime, occur in such small quantities, that they can be safely omitted in making artificial seawater; and besides, river and spring water always contain a considerable proportion of lime. Therefore, according to Mr. Gosse, we may use the following formula: In every hundred parts of the solid ingredients, Common Salt, 81 parts; Epsom Salts, 7 parts ; Chloride of Magnesium, 10 parts; Chloride of Potassium, 2 parts ; and of Water about 2900 parts, although this must be accurately determined by the specific gravity. The mixture had better be allowed to stand several days before filling the tank ; for thus the impurities of the chemicals will settle, and the clear liquor can be decanted off. The specific gravity should then be tested with the hydrometer, and may safely range from 1026 to 1028,—fresh water being 1000. If a quart or two of real sea-water can be obtained, it is a very useful addition to the mixture. It may now be introduced into the tank through a filter. But no living creatures must be introduced until the artificial water has been softened and prepared by the growth of the marine plants in it for several weeks. Thus, too, it will be oxygenated, and ready for the oxvgen-using tenants.

It is a singular fact, that water which has been thus prepared, with only four ingredients, will, after being a month or more in the aquarium, acquire the other constituents which are normally present in minute quantities in the natural sea-water. It must derive them from the action of the plants or animals, or both. Bromine may come from sponges, or sea-wrack, perhaps. Thus artificial water eventually rights itself.

The tank, having been prepared and seasoned with the same precaution used for the river aquarium, and having a clear bottom anti a supply of good water, is now ready for planting. Many beautifully colored and delicately fringed Algæ and Sea-Wracks will be found on the rocks at low tide, and will sadly tempt the enthusiast to consign their delicate hues to the aquarium. All such temptations must be resisted. Green is the only color well adapted for healthy and oxygenating growth in the new tank. A small selection of the purple or red varieties may perhaps be introduced and successfully cultivated at a later day, but. they are very delicate ; while the olives and browns are pretty sure to die and corrupt the water. It must be remembered, too, that the Algas are cryptogamous, and bear no visible flowers to delight the eye or fancy. Of all marine plants, the Ulva latissima, or Sea-Lettuce, is first and best. It has broad, light-green fronds, and is hardy and a rapid grower, and hence a good giver of oxygen. Next to this in looks and usefulness comes the Enteromorpha compressa, a delicate, grass-like Alga. After a while the Chondrus crispus, or common Carrageen Moss, may be chosen and added. These ought to be enough for some months, as it is not safe to add too many at once. Then the green weeds Codium tomentosum and Cladophora may be tried ; and, still later, the beautiful Bryopsis plumosa. But it is much better to be content with a few Ulvæ, and others of that class, to begin with; for a half dozen of these will support quite a variety of animal life.

After a few hardy plants are well set, and thriving for a week or two, and the water is clear and bubbly with oxygen, it will be time to look about for the live stock of the marine aquarium. Fishes, though most attractive, must be put in last; for as they are of the highest vitality, so they require the most oxygen and food, and hence should not be trusted until everything in the tank is well a-going.

The first tenants should be the hardy varieties of the Sea-Anemones, or Actiniœ, — which are Polyps, of the class Radiata. The Actinia mesembryanthemum is the common smooth anemone, abounding on the coast, and often to be found attached to stones on the beach. “ When closed,” says Mr. Hibbert, “it has much resemblance to a ripe strawberry, being of a deep chocolate color, dotted with small yellow spots. When expanded, a circle of bright blue beads or tubercles is seen within the central opening ; and a number of coral-like fingers or tentacles untold from the centre, and spread out on all sides.” It remains expanded for many days together, if the water be kept pure ; and, having little desire for locomotion, stays, generally, about where it is placed. It is a carnivorous creature, and seeks its food with its ever-searching tentacles, thus drawing in fishes and mollusks, but, most frequently, the minute Infusoria. Like other polyps, it may be cut in two, and each part becomes a new creature. It is a very pretty and hardy object in the aquarium. There are many varieties, some of which are very delicate, as the Actinia anguicoma, or Snaky-locked Anemone, and the pink and brown Actinia bellis, which so resembles a daisy. Others, as the Actinia parasitica, are obtainable only by deep-sea dredging; “ and, as its name implies, it usually inhabits the shell of some defunct mollusk. And more curious still, in the same shell we usually find a pretty crab, who acts as porter to the anemone. He drags the shell about with him like a palanquin, on which sits enthroned a very bloated, but gayly-dressed potentate, destitute of power to move it for himself.” 2

The Actinia gemmacea, or Gemmed Anemone, the Actinia crassicornis, and the Plumose Anemone are all beautiful, but tender varieties.

The Anemones require but little care ; they do not generally need feeding, though the Daisy and Plumose Anemone greedily take minced mutton, or oyster. But, as a rule, there are enough Infusoria for their subsistence ; and it is safer not to feed them, as any fragments not consumed will decay, and contaminate the water.

Next in order of usefulness, hardiness, and adaptability to the new aquarium, come the Mollusks. And of these, Snails and Periwinkles claim our respectful attention, as the most faithful, patient, and necessai’y scavengers of the confervoid growths, which soon obscure the marine aquarium.

“ It is interesting,” says Mr. Gosse, “ to watch the business-like way in which the Periwinkle feeds. At very regular intervals, the proboscis, a tube with thick fleshy walls, is rapidly turned inside out to a certain extent, until a surface is brought into contact with the glass having a silky lustre; this is the tongue; it is moved with a short sweep, and then the tubular proboscis infolds its walls again, the tongue disappearing, and every filament of Conferva being carried up into the interior, from the little area which had been swept. The next instant, the foot meanwhile having made a small advance, the proboscis unfolds again, the tongue makes another sweep, and again the whole is withdrawn ; and this proceeds with great regularity. I can compare the action to nothing so well as to the manner in which the tongue of an ox licks up the grass of the field, or to the action of the mower cutting swath after swath.”

Of Crustacea, the Prawns and the smaller kinds of Crabs may be admitted to the aquarium, though but sparingly. They are rude, noisy, quarrelsome, and somewhat destructive,—but, for the same reason, amusing tenants of the tank.

All are familiar with the mode in which the Soldier or Hermit Crab takes possession of and lives in the shells of Whelks and Snails. Poorly protected behind by Nature, the homeless crab wanders about seeking a lodging. Presently he meets with an empty shell, and, after probing it carefully with his claw to be sure it is not tenanted, he pops into it back foremost in a twinkling, and settles himself in his new house. Often, too, he may be seen balancing the conveniences of the one he is in and of another vacant lodging he has found in his travels; and he even ventures out of his own, and into the other, and back again, before being satisfied as to their respective merits. In all these manœuvres, as well as in his daily battles with his brethren, he is one of the drollest of creatures.

As we advance in our practice with the aquarium we may venture to introduce more delicate lodgers. Such are the beautiful family of the Annelidœ: the Serpula, in his dirty house; and the Terebella, most ancient of masons, who lays the walls of his home in water-proof cement.

The great class of Zoöphytes can be introduced, but many varieties of them will be found already within the aquarium, in the company of their more bulky neighbors. These peculiar creatures, or things, form the boundary where the last gleam of animal life is so feeble and flickering as to render it doubtful whether they belong to the animal or vegetable kingdom. Agassiz calls them Protozoa, — Primary Existences. Some divide them into two great classes, namely : the Anthozoa, or Flower-Life ; and the Polyzoa, or Many-Life, in which the individuals are associated in numbers. They are mostly inhabitants of the water ; all are destitute of joints, nerves, lungs, and proper blood-vessels; but they all possess an irritable system, in obedience to which they expand or contract at will. Among the Anthozoa are the Anemones; among the Polyzoa are the Madrepores, or CoralBuilders, and many others. Many are microscopic, and belong to the class of animalcules called Infusoria.

A very remarkable quality which the Infusoria possess — one very useful for the aquarium, and one which would seem to settle their place in the vegetable kingdom— is that they exhale oxygen like plants. This has been proved by Liebig, who collected several jars of oxvgen from tanks containing Infusoria onlv.

A piece of honeycomb coral (Eschara foliacea) is easily found, and, when well selected and placed in the aquarium, may continue to grow there by the labors of its living infusorial tenants: they are not unworthy rivals of the Madrepores, or deep-sea coral-builders of warmer latitudes. The walls of its cells are not more than one-thirtieth of an ineh in thickness, and each cell has its occupant. So closely are they packed, that in an area of one-eighth of an inch square the orifices of forty-five cells can be counted. As these are all double, this would give five thousand seven hundred and sixty cells to the square inch. Now a moderate-sized specimen will afford, with all its convolutions, at least one hundred square inches of wall, which would contain a population of five hundred and seventysix thousand inhabitants, — a very large city. So says Mr. Gosse. We cannot forbear, with him, from quoting Montgomery’s lines on the labors of the coralworms, which modern science has enabled us to study in our parlors.

“Millions on millions thus, from age to age,
With simplest skill, and toil unweariable,
No moment and no movement unimproved,
Laid line on line, on terrace terrace spread,
To swell the heightening, brightening, gradual mound,
By marvellous structure climbing towards the day.
Each wrought alone, yet all together wrought,
Unconscious, not unworthy instruments,
By which a hand invisible was rearing
A new creation in the secret deep,
.....I saw the living pile ascend,
The mausoleum of its architects,
Still dying upwards as their labors closed;
Slime the material, but the slime was turned
To adamant by their petrific touch:
Frail were their frames, ephemeral their lives,
Their masonry imperishable.”

The deep-sea soundings taken recently for the Atlantic telegraph have demonstrated the existence of organic life even at the bottom of the ocean. Numerous living Infusoria have been brought to the light of day, from their hidden recesses, by the lead. “Deeper than ever plummet sounded ” before these latter days, there exist myriads of minute creatures, and of Algæ to furnish their food. It is an unanswered problem, How they can resist the enormous pressure to which they must be there subjected, amounting, not infrequently, to several tons to the square inch. And still another point of interest for us springs from this. It is an inquiry of practical importance to the aquarian naturalist, How far the diminished pressure which they meet with in the tank, on being transferred from their lower homes to the aquarium, may influence their viability. May not some of the numerous deaths in the marine tank be reasonably attributed to this lack of pressure ? What a difference, too, has Nature established, in the natural power to resist pressure, between those creatures which float near the surface and those which haunt the deeper sea! The Jelly-fish can live only near the top of the water, and, floating softly through a gentle medium, is yet crushed by a touch; while the Coralbuilder bears the superincumbent weight of worlds on his vaulted cell with perfect impunity.

Another important question is, How far alteration in the amount of light may affect the more delicate creatures. What fishes do without light has been solved by the darkness of the Mammoth Cave, the tenants of whose black pools are eyeless, evidently because there is nothing to see. The more deeply located Infusoria and Mollusks must dwell in an endless twilight; for Humboldt lias found, by experiment, that at a depth one hundred and ninety-two feet from the surface the amount of sunlight which can penetrate is equal only to one-half of the light of an ordinary candle one foot distant.

Thus ever in gloom, yet in a state of constant safety from storms and the agitations of the upper air, the thousand forms of low organic life and cryptogamic vegetation live and thrive in peace and quietness.

“ The floor is of sand like the mountain drift,
And the pearl-shells spangle the flinty snow;
From the coral rocks the sea-plants lift
Their boughs, where the tides and billows flow.
" And life in rare and beautiful forms
Is sporting amid those bowers of stone,
And is safe, when the wrathful spirit of storms
Has made the top of the waves his own.” 3

Upon the bottom, at various depths, lies that brilliant Radiate — type of his class—the Star-fish. These are quiet and harmless creatures, and favorites in the aquarium, from the pretty contrast they make with marine plants and other objects.

The perfect transparency, elegant form, and graceful navigation of the Medusœ, or Jelly-fishes, render them much admired in their native haunts, and prized for the aquarium. But they are very delicate. How beautiful and remarkable are these headless Discophori, as they float, and propel themselves with involutions of their disks and gently trailing tentacles, and the central peduncle hanging far below, like the clapper of a transparent bell! And yet these wonders are but so much sea-water, inclosed in so slight a tissue that it withers in the sun, and leaves only a minute spot of dried-up gelatinous substance behind.

Finally come the Fishes, many of which are of similar genera to those recommended for the fresh-water tank. The Black Goby is familiar, tamable, but voracious; the Gray Mullet is very hardy, but also rather savage; the Wrasses are sotne of the most showy fish, — called in some parts of the country Cunners, — and of these, the Ancient weasse,(Labrus maculatus,) covered with a network of vermilion meshes on a brown and white ground, is the most elegant.

Some points of general management are so important, and some dangers so imminent, that we cannot pass them by unnoticed. The aquarian enthusiast is very apt to be in too great haste to see everything going on, and commits the common error of trying too many things at once. The aquarium must be built up slowly and tentatively, object by object: plants first, and of the simplest kinds; and not until they are well settled, and the water beaded with oxygen bubbles, should we think of introducing living creatures, — and even then only the hardier kinds of actinias, mollusks, and crabs. All delicate animals must be intrusted one by one to their new home, and carefully watched for deaths and decay, which, whether arising from dead plants or animals, ruin everything very quickly, unless they be promptly removed. For sulphuretted hydrogen, even in very minute quantities, is sure death tc all these little creatures. The emanations from paint and putty are often fatal in new tanks. Several weeks’ exposure to water, air, and sunlight is necessary to season the new-made aquarium. Of equal consequence is it that the water bo absolutely pure; and if brought from the sea, care must be exercised about the vessel containing it. Salt acts upon the glazing of earthen ware of some kinds. Stone or glass jars are safest. New oak casks are fatal from the tannin which soaks out; fir casks are safe and good. So delicate and sensitive are the minute creatures which people the sea, that they have been found dead on opening a cask in which a new oak bung was the only source of poison. And no wonder; for a very slight proportion of tannic acid in the water corrugates and stiffens the thin, smooth skin of the anemone, like the tanning of leather.

A certain natural density of the seawater must also be preserved, ranging between no wider limits than 1026 and 1028. And in the open tank evaporation is constantly deranging this, and must be met by a supply from without. As the pure water alone evaporates, and the salts and earthy or mineral constituents are left behind, two things result: the water remaining becomes constantly more dense ; and this can be remedied only by pure fresh water poured in to restore the equilibrium. Hence the marine aquarium must be replenished with fresh water, until the proper specific gravity, as indicated by the hydrometer, is restored.

The aquarium may be found some morning with a deep and permanent green stain discoloring the water. This unsightly appearance is owing to the simultaneous development of the spores of multitudes of minute Alga: and Confervæ, and can be obviated by passing the water through a charcoal filter. When any of the fishes give signs of sickness or suffocation, by coming to the surface and gulping air, they may be revived by having the water aërated by pouring it out repeatedly from a little elevation, or by a syringe. The fishes are sometimes distressed, also, when the room gets too warm for them. A temperature of 60° is about what they require. And they will stand cold, many of them, even to being frozen with the water into ice, and afterwards revive.

The degree of light should be carefully regulated by a stained glass side, or a shade. Yet it must be borne in mind that sunlight is indispensable to the free evolution of oxygen by the plants. And when the sun is shining on the water, all its occupants appear more lively, and the fishes seem intoxicated — as they doubtless are — with oxygen.

A novice is apt to overstock his aquarium. Not more than two moderate-sized fishes to a gallon of water is a safe rule. Care, too, must be taken to group together those kinds of creatures which are not natural enemies, or natural food for each other, or a sad scene of devastation and murder will ensue.

Cleansing cannot be always intrusted to Snails. But the sides may be scrubbed with a soft swab, made of cotton or wick-yarn. Deaths will occasionally take place ; and even suicide is said to be resorted to by the wicked family of the Echinoderms.

To procure specimens for the aquarium requires some knack and knowledge. The sea-shore must be haunted, and even the deep sea explored. At the extreme low-water of new or full moon tides, the rocks and tide-pools are to be zealously hunted over by the aquarian naturalist. Several wide-mouthed vials and stone jars are necessary; and we would repeat, that no plant should be taken, unless its attachment is preserved. It is often a long and difficult job to get some of the Algæ with their tender connections unsevered from the hard rock, which must he chipped away with the chisel, and often with the blows of the hammer deadened by being struck under water.

It is by lifting up the overhanging masses of slimy fuci, tangles, and sea-grass, that we find the delicate varieties, as the Chondrus with its metallic lustre, and the red Algœ, or the stony Corallina, which delights in the obscurity of shaded pools.

The sea-weeds will be found studded with mollusks,—as Snails and Periwinkles of many queer varieties. Anemones, of the more common kinds, are found clinging to smooth stones. Crabs on the sand. Prawns, Shrimps, Medusæ, and fishes of many species, in the little pools which the tide leaves behind, and which it will require a sharp eye and a quick hand to explore with success. Put the rarer forms of Actinias, Star-fishes, Sepioles, Madrepores, Annelidæ, and Zoöphytes, of a thousand shapes, live on the bottom, in deep water, and must be captured there.

For this purpose we must dredge from a boat, under sail. The naturalist’s dredge is an improved oyster-dredge, with each of the two long sides of the mouth made into a scraping lip of iron. The body is made of spun-yarn, or fishing-line, netted into a small mesh. Two long triangles are attached by a hinge to the two short side3 of the frame, and meeting in front, at some distance from the mouth, are connected by a swivel-joint. To this the dragging rope is bent, which must be three times as long, in dredging, as the depth of the water. This is fastened to the stern of a boat under sail, and thus the bottom is raked of all sorts of objects; among which, on emptying the net, many living creatures for the aquarium are found. These may be placed temporarily in jars ; though plants, mollusks, Crustacea and Actiniæ may be kept and transmitted long distances packed in layers of moist sea-weed.

For all this detail, labor, and patient care, we may reasonably find two great objects : first, the cultivation and advancement of natural science ; second, the purest delight and healthiest amusement.

In the aquarium we have a most convenient field for the study of Natural History: to learn the varieties, nature, names, habits, and peculiarities of those endless forms of animated existence which dwell in the hidden depths of the sea, and at the same time to improve our minds by cultivating our powers of observation.

The pleasure derived from the aquarium comes from the excitement of finding and collecting specimens, as well as from watching the tank itself. There can be no more pleasant accompaniment to the sea-side walk of the casual visitor or summer resident of a wateringplace, than to search for marine plants and animals among the fissures, rocks, and tide-pools of the sea-washed beach or cape.

Nature is always as varied as beautiful. Thousands of strange forms sport under the shadow of the brown, waving sea-weeds, or among the delicate scarlet fronds of the dulse, which is found growing in the little ponds that the inequalities of the beach have retained. It is down among the great boulders which the Atlantic piles upon our coast, that we may find endless varieties of life to fill the aquarium, though not those more gorgeous hues which distinguish the tenants of the coral reefs on tropical shores. Yet even here Nature is absolutely infinite; and we shall find ourselves, day after day, imitating that botanist who, walking through the same path for a month, found always a new plant which had escaped his notice before. So, too, in exploring the open sea, besides the pleasure of sailing along a variegated coast, with sun and blue water, we have the constant excitement of unexpected discovery: for, as often as we pull up the dredge, some new wonder is revealed.

Words fail to describe the wonders of the sea. And all that we drag from the bottom, all that we admire in the aquarium, are but a few disconnected specimens of that infinite whole which makes up their home.

So, too, in watching the aquarium itself, we shall see endless repetitions of those “ sea-changes ” which Shakspeare sang. Ancient mythology typified the changing wonders of aquatic Nature, as well as "the fickleness of the treacherous sea, in those shifting deities, Glaucus and Proteus, who tenanted the shore. The one the fancy of Ovid metamorphosed from a restless man to a fickle sea-god ; the other assumed so many deceptive shapes to those who visited his cave, that his memory has been preserved in the word Protean. Such fancies well apply to a part of Nature which shifts like the sands, aud ranges from the hideous Cuttle-fish and ravenous Shark to the delicate Medusa, whose graceful form and trailing tentacles float among the waving fronds of colored Algse, like

“ Sabrina fair,
Under the glassy, cool, translucent wave,
In twisted braids of lilies knitting
The loose train of her amber-dropping hair."
  1. The Book of the Aquarium, by Sidney Hibbort. of pure oxygen. The theory of distinct respiration has been somewhat doubted by the lushest botanical authority of this country ; but the theory of digestion is indisputable. And it is no less certain that all forms of vegetation give to the air much more free oxygen than they take from it, and much less carbonic acid, as their carbonaceous composition shows. If fresh leaves are placed in a bell-glass containing air charged with seven or eight per cent, of carbonic acid, and exposed to the light of the sun, it will be found that a large proportion of the carbonic acid will have disappeared, and will be replaced by pure oxygen. But this change will not be effected in the dark, nor by any degree of artificial light. Under water the oxygen evolved from healthy vegetation can be readily collected as it rises, as has been repeatedly proved.
  2. Hibbert’s Book of the Aquarium.
  3. Percival.