enormous quantities of gelatinous masses of eggs which they have deposited on all parts of the receiver, as well as on the fragments of stone-appear to thrive wonderfully, affording a large quantity of food to the fish in the form of the young snails, which are devoured as soon as they exhibit signs of vitality and locomotion, and before their shell has become hardened.'

In remarking upon the result of his experiments, Mr Warington observes: 'Thus we have that admirable balance sustained between the animal and vegetable kingdoms, and that in a liquid element. The fish, in its respiration, consumes the oxygen held in solution by the water as atmospheric air, furnishes carbonic acid, feeds on the insects and young snails, and excretes material well adapted as a rich food to the plant, and well fitted for its luxuriant growth. The plant, by its respiration, consumes the carbonic acid produced by the fish, appropriating the.carbon to the construction of its tissues and fibres, and liberates the oxygen in its gaseous state to sustain the healthy functions of the animal life; at the same time that it feeds on the rejected matter, which has fulfilled its purposes in the nourishment of the fish and snail, and preserves the water constantly in a clean and healthy condition. While the slimy snail, finding its proper nutriment in the decomposing vegetable matter and minute confervoid growth, prevents their accumulation by removing them; and by its vital powers converts what would otherwise act as a poison into a rich and fruitful nutriment, again to constitute a pabulum for the vegetable growth, while it also acts the important part of a purveyor to its finny neighbours.' This perfect adjustment in the economy of the animal and vegetable kingdoms, whereby the vital functions of each are permanently maintained, is one of the most beautiful phenomena of organic nature. In the marine aquarium, the presence of molluscs is as necessary as in the fresh-water aquarium, to prevent an excessive growth of confervæ, which otherwise soon make the water turbid with their innumerable green seeds or spores, and obscure the glass by establishing themselves upon it in vast colonies. The common periwinkle, topshell, and limpet are very suitable for this purpose.

Though the marine aquarium is more difficult to manage than that of fresh water, it will be to many so much more novel and interesting, that we confine our explanations chiefly to it. But before describing the special qualities of a marine aquarium, let us say a few words of the varieties of zoophytes which are to constitute its principal attraction.

Zoophyte is a term compounded from two Greek words signifying an animal and a plant, and is applied to a most remarkable class of creatures, now known to be truly animal, although many of them were once regarded as plants, or as forming a link between the animal and vegetable kingdoms. Nothing within the range of natural history possesses a more interesting and wonderful character than

these plant-like animals. Their colours, and the expanded tentacles which surround the mouth, give to the simplest of them a remarkable flower-like appearance; whilst others have a stem and branches, bearing a multitude of minute flower-like polypes, the tentacles of which move about in the water in quest of prey, but which on any alarm are instantaneously contracted into mere buds, or disappear altogether into the cells from which they had issued. Nothing can be imagined more beautiful than some of these beings, whether form or colour is considered; but they are still more interesting from their marvellous structure, as compound animals, originating from a single egg or germ, and simple at first, but budding according to certain laws peculiar to each particular kind, and growing like little trees or shrubs, of which each bud has an individuality of its own, its own mouth, and tentacles, and stomach, and power of propagation, whilst yet it partakes in the common individuality of the whole; an organic connection being maintained throughout every part-a separate life and yet also a united life, so that it would be hard for a moralist to determine, if it were of any importance, the bounds of the meum and tuum, and still harder for a metaphysician to settle the relations of the Ego and non-Ego. There are zoophytes which are found in fresh water, while others are found only in the sea. According to science, there are numerous orders and species o zoophytes, but we refer only to those found on the shores of the sea within the action of the tides, and leave out of view the classes which form corals and sponges, or which are of a microscopic character.

Of the sea-side zoophytes, there are many kinds, all less or more curious, as differing from what one is accustomed to in animal life. Some grow tall in a plant-like form, others are soft and simple, adhering to shells or rocks, of which latter kind the Actinias, or seaanemones, called animal-flowers, are the most prized. Others, called Tubularias, rooted on rocks, shells, and stones by a stem above a foot high, have a scarlet head resembling a beautiful pink. Several bunches resembling clusters of grapes, forming the eggs, are borne externally on the head. Each egg, on attaining maturity, drops out of its cluster, and falling below, is hatched into a young zoophyte. At first, this is a head only; it is endowed, for some time, with the faculty of moving from place to place, and, after taking up a position, the stem grows downwards, by which it is then permanently rooted to the same spot. The species of Flustra, or sea-mat, resemble a leaf, one or both sides of which are composed entirely of cells like a slipper, each inhabited by an animal concealed within when at rest, and stretching out when active, but fixed by the lower extremity. The late Sir John Graham Dalyell, a writer on this subject, says of a sea-anemone which he kept for a long time: 'In the course of six years it produced between two and three hundred young, which also bred on attaining maturity. The embryos of this

animal are carried in the tips of its hollow and transparent feelers; they can be withdrawn entirely, or transferred from one to another,

and after this extraordinary kind of gestation, are finally produced by the mouth. A tip containing an embryo having been amputated, the embryo survived five years after extraction, fed, and grew, and bred in its turn. The actinia is a most voracious creature, and after feeding greedily, the food is rejected in the form of a ball. No living creature it can overpower escapes its grasp.'

Notwithstanding the numerous investigations that have been made into the nature of zoophyte life, it is still involved in considerable mystery. They are creatures destitute of many of the chief organs of ordinary animals; they have no eyes to see, feet to walk, fins to swim; they have no breathing or blood-circulating process, such as the higher animals have; no heart for the maintenance of the circulation, no lungs or gills for respiration, and no nervous system has been discovered in them. But they have a stomach, which, in the simple zoophytes, such as sea-anemones, occupies the whole centre of the jelly-like animal, which may be likened to a thick bag, with tentacles surrounding its mouth; and they have a power of discovering, seizing, and bringing to the mouth objects suitable for their nutrition, as well as of discovering the approach of objects which may be dangerous, on which they retract their tentacles, and contract themselves as much as possible. It may here be mentioned that the aquarium affords admirable opportunity for observations with the microscope. Not only will interesting objects, both animal and vegetable, be easily taken from it, to be subjected to a powerful microscope, but observations may continually be made by a good single lens-a Coddington lens is the best for the purpose-through the glass of the aquarium itself, and thus zoophytes and other minute animals may be studied in their life and activity. A little management will bring close to the surface of the glass whatever it is desired to observe, and the lens must be placed close to the glass on the outside. The minute polype may thus be seen, extending its circle of tentacles for prey, or shrinking back into its cell on the slightest agitation of the water. Many a form of wondrous beauty, and many not less wondrous habits, may be easily observed. Those beautiful animalcules called Vorticella, may be seen in a fresh-water aquarium to the greatest advantage-as they often attach themselves to the glass itself-with their flower-like form,

their branching stalks and little bells or cups, as they stretch out the stalks to the utmost or suddenly retract them into a spiral. Or the pond-snail, the periwinkle, or the limpet may be watched, as they travel over the inner surface of the glass, licking up with rasping tongue the minute young confervæ which have established themselves there, every action of the mouth being most perfectly visible. To enjoy a good opportunity of observing some of the most curious forms of life either in a fresh-water or salt-water aquarium, it is necessary that the water be kept for a considerable time unrenewed. A little may be added, as evaporation takes place, but none must be taken away.

Before commencing the marine aquarium, we would recommend a perusal of Tenby, A Sea-side Holiday, by Mr P. H. Gosse, to whose persevering investigations into zoophyte life the world is greatly indebted. We would also recommend a perusal of the Book of the Aquarium, by Shirley Hibberd, a work containing practical instructions and useful hints as to the stocking and management of fresh and sea water aquaria. The following quotation, referring to the marine aquarium, will afford a specimen of this valuable kind of information: The first danger to guard against is overstocking; the next danger is the association of animals that were never intended by nature to agree, as, for instance, Dianthus with Carcinus, or Pholas with Asterina. Where there are several vessels, appropriate one to Actinia, Madrepores, Polyzoa, and Chitons; another to molluscs only; another to such of the fishes as come within the range of our practice; and another to crustaceans, and you will be free of warfare. If you have but one vessel, be content with a few of the most attractive and interesting zoophytes, and do not crowd it with incongruous gatherings. At any time, a glass dish, a picklebottle, or even a common earthenware soup-plate, may be turned to account for a few rare and curious things, of kinds unsuitable for the tank that friends may send you, or that you may collect upon the sea-shore. Crabs sprawl over anemones, and torment them; and anemones entangle fishes with their barbed threads, and destroy them.'

Small fishes are amongst the most pleasing inmates of the aquarium. The little gobies, common in rock-pools on the seacoast, can be kept in the marine aquarium with great ease, and afford much amusement by their liveliness, and the activity with

which they dart out from their corners in quest of prey. They soon become tame enough to feed from the hand. In the fresh-water

aquarium, no fish is more interesting

than the stickleback, which takes possession of a place for itself, and maintains it against all intruders, resenting any approach to its chosen domain, and tumbling over the water beetle in its violent assaults. At the breeding season it becomes doubly interesting by its nest-building, a fact in its natural history not long known, but which the possessor of an aquarium may very probably have opportunity to observe.

Crabs are also very amusing; their voracity, their pugnacity, and their changes of shell, cannot fail to attract and reward attention. The hermit-crab, inhabiting the deserted shell of a whelk or other mollusc, and walking about with it on his back, is particularly interesting. But crabs are too active, and too rude in their activity, to be tolerated in an aquarium stocked with delicate zoophytes.

Sticklebacks and Nest.

Besides the risk of overstocking, and also of badly assorting, there is a danger of too much light and heat, and also of too great a depth