To remedy this state of things, the evil effects of which soon became apparent, artificial aeration was resorted to, by means of another vessel, which kept up a continuous supply of dripping fresh water. But even this assistance did not enable the crowded colony to exist more than ten days. In the first place, there were many predatory species, which destroyed their associates; these kinds must, therefore, be excluded from an Aquarium, or kept in a separate tank. But, after all, the impossibility of providing a sufficient supply of oxygen was evidently the great and principal cause of failure. The Univalves and smaller Crustacea disappeared first, a disagreeable smell giving intimation that decay was going on, the creatures that had perished having, many of them, died in concealment, under the stones, weeds, &c., at the bottom of the Aquarium. The first signs of unpleasant effluvia rising from the tank must, therefore, be carefully attended to; and, in such cases, the Aquarium ought to be immediately searched for the cause; which, when discovered, should be immediately removed. [Illustration: PLATE XI. A DESIGN FOR A PLAINLY-MOUNTED AQUARIUM.] Mr. Gosse having taken out the whole of the specimens, dead and alive, and carefully cleansed the tank, a much smaller number was put in, which, being well selected, and having sufficient space, throve abundantly well; and the ingenious experimentalist was at last amply rewarded for all his persevering exertions. This result benefited others as well as himself, for a general taste suddenly arose for this kind of pursuit, among all who read the various works which soon appeared on the subject; and, to gratify the new taste, a host of dealers in Aquaria have sprung up, who are driving a brisk and profitable trade. The first experiments of Mr. Gosse sufficiently point out the kind of cautions to be observed in the formation of a marine Aquarium. The vessel itself may be either quite plain in its frame-work, as shown in Plate XI., or made more or less ornamental, to assimilate, if necessary, with surrounding objects or furniture. The rustic style of frame, designed in Plate XII., has been found to accord well with the general character of the Aquarium itself, and it produces an agreeable contrast with the usual forms of the furniture of our ordinary sitting-rooms. [Illustration: PLATE XII. A DESIGN FOR AN AQUARIUM MOUNTED IN HANDSOME RUSTIC-WORK.]