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shaped fish, and we have seen specimens nearly 3 feet in length, whose whitish enamelled plates reminded us strongly of what many of the ancient primary fishes must have been. The habits of this suggestive fresh-water fish very much resemble those of its English namesake, hence, no doubt, the reason why it was called "gar-pike" by the colonists. We hardly need point out the advantages which large aquaria possess in making us acquainted with the lifehistory of desirable fishes, before we attempt their acclimatisation for ulterior purposes. Hitherto we

have done this quite at a venture.

AERATING LARGE AQUARIA.

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CHAPTER VI.

THE AQUATIC GARDEN AND ITS PLANTS.

UNTIL within a year or two ago the circulatory system of aerating large aquaria was confined to salt water. After Mr. Lloyd applied it thus, at Hamburg, in 1868, Mr. Saville-Kent applied it to the fresh-water tanks in the Manchester Aquarium with some success. The chief means of aerating the water was either by means of fountains, or through the agency of aquatic plants. Of course it will be impossible to amateur keepers of aquaria to aerate their small reservoirs by mechanically circulating the water. Such a process would be troublesome, and would hardly repay the large expense and outlay of labour by the small returns that would be afforded. Moreover, one reason for keeping aquaria in rooms is on account of their pretty and attractive appearance, and this would not be so effective without the greenery of aquatic or semi-aquatic vegetation which they usually possess. It is true Mr. Kent found that fishes suffering from the attacks of a white fungoid growth quickly recovered when placed in tanks aerated by circulation. Mr. Kent is of opinion that the fungoid growth is due to the lime in the water.

In this opinion we cannot agree. First, we are not aware that lime is at all an adjunct to the growth of microscopic fungi, and the Manchester water is singularly free from it as compared with that of most towns. We believe the fungoid growth to be due to a surplus of nitrogenous matter in solution, caused, perhaps, by the decay of animal substances to which tanks are liable if not properly attended to. Nitrogen is a necessity and stimulant to the growth of fungi of all kinds, and it is evident that the removal of affected fishes to clear running water where nitrogen is absent would counteract the disease. It has long been known to keepers of fresh-water aquaria that the best way to cure fish affected by the white fungus was to remove them to a tub where the water was constantly dripping from the tap. We have referred to this matter at length because it is one that cannot fail to interest aquarium owners.

A judicious selection and grouping of aquatic vegetation adds greatly to the beauty of a fresh-water aquarium; and we have hinted how plants requiring deep soil, as well as those requiring little or none, may be accommodated in the same tank, by planting the former in ordinary flower-pots. These may be so arranged along one or other of the sides as to be only just covered with water, and then it will be possible to grow such semi-aquatic plants as the lovely buck-bean (Menyanthes trifoliata), sun-dew (Drosera rotundifolia and anglica), Polygonum amphibium, the

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flowering rush (Butomus umbellatus), the water mint (Mentha aquatica), mare's tail (Hippuris vulgaris),

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and others. Our native vegetation offers considerable choice, and for the beauty of the foliage and

flowers of some even of the commonest species, it would be difficult to find an equal number of foreign plants that would excel them in this respect. It should be remembered, however, that the main thing in the selection of aquatic plants is to have such species as will most effectively oxygenate the water. And it is always best to have the vegetable element slightly in excess of the animal, inasmuch as it can be more effectually managed, either by elimination, or by moderating the light which stimulates its growth. The common American weed (Anacharis alsinastum) has never yet been known to flower or seed in this country. It is propagated solely by budding, and we have already said that fish, and especially goldfish and carp, are very fond of nibbling the young and tender shoots. A little of this plant may therefore always be advantageously introduced into a tank of moderate capacity. It must be seen, however, that its tendency to rank growth does not interfere with other and more ornamental plants.

Another species which has long been utilised in this country by druggists, to oxygenate the water in which medical leeches are kept, is the Vallisneria spiralis. It is a native of the south of Europe, but has been pretty extensively distributed in England. This plant is undoubtedly one of the best and most copious yielders of oxygen of all common fresh-water species, and therefore is of great service in small tanks. Its grass-like leaves show the circulation of

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