AQUAVIVARIU31, a term proposed to be applied to arrangements which contemplate the exhibition of living aquatic specimens of animals inhabiting either fresh or salt water. Although it has been known from the earliest time, that animals living in water may he kept in small glass vessels for exhibition by the daily supply of fresh-water, the discoveries of modern chemistry have pointed out how animals may be kept living in only limited quantities of water which never demand renewing. The possibility of accomplishing this depends on the absolute balance in nature which exists between the animal and vegetable kingdoms. [Amstar. Kreermost] The ono set of these beings are for ever engaged in giving off what the other requires, and in taking up what the other rejects. It is thus that the carbonic acid which is constantly being thrown off the tissues of animals is taken up by plants, and thus prevented from contaminating the atmosphere ; whilst the plant is constantly engaged in giving Mt oxygen gas, and supplying the atmosphere with this element of its composition which is necessary to the life of animals. The relations which are thus found to exist on the large scale of the whole surface of the earth, are found also to occur in a jar of water. If an animal is placed in pure water it quickly exhausts the oxygen it eontsmins, and gives out into it carbonic acid gas; the consequence is, that it is quickly poisoned unless fresh water with oxygen is supplied. But if wo place with the animal some plant that lives in water, it will be found that the carbonic acid given out by the animal will be taken up by the plant, and that it will give out oxygen in its place. Thus the water becomes cleared of its injurious compound, and the needed element, oxygen, is supplied. This is really what takes place in every pond and pool where the water is fresh, and all that is required to make the inhabitants of the pond visible is to put the whole pond, plant, and animals into a glass-case. Such a plan has been tried with great success, and we propose to call the apparatus in which it is effected an Aquavivarium.
The first experiments were made with fresh-water, and we believe the public is indebted for one of the earliest accounts of such an arrangement to Mr. Warington, chemist to the Apothecaries' Company.
He found out, however, that it was not sufficient to have simply any kind of plants and animals; but that, in order to maintain the balance correctly, it was necessary that certain animals which lived on decom posing vegetable matter should be present. At certain seasons of the year the tendency to decomposition in the water-plants becomes so decided that the water would be rendered impure if this decomposition was not arrested. The cure for this was found in the addition of fresh-water Mollusea to the jars containing such fish as the gold-carp and stickleback and such plants as the Vallisneria &c. The best kind of snails for this purpose arc the various species of Planorbis. Not only is it necessary that this latter precaution be taken to ensure the success of the experiment, but it is of importance to guard against the preponderance of animal life. Although in most cases it appears that there cannot be too many plants for the health of the animal as long as they grow healthily and do not decompose, yet it often happens that the excess of animals over plants in a given space will destroy the balance, and lead to the destruction of life. We are not aware that any precise experiments with regard to the quantity of water and the number of plants and animals have been yet performed. We can however state as a fact, that a gold-fish has lived for nearly twelve mouths in about two gallons of water with several flourishing plants of rullisneria spiralis. It is probable that a smaller quantity of water would have served equally Amongst the fresh-water plants adapted for growing in ouch jars or tanks as we have mentioned, are the rallisneria apiralia, various species of Clara, A nacharis Alsinastrum, Stratiota Abides, Callitriche automatic, C. rernalis, yriophyllum spicatum, and Ranunculus ageuditia. Such jars afford a good opportunity for cultivating the various species of fresh-water Confervte, which all assist in keeping the water pure. One of the most beautiful of these is the ydrodietyon striculatuen, which may be easily propagated in this manner.