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may project above the surface of the water, to allow such animals as desire it the means of gratifying' themselves. The author of "Ocean Gardens" suggests a kind of double Aquarium, and a contrivance by means of which a large portion of water should flow gradually from one tank to the other at fixed periods, in imitation of the ebb and flow of the tide. Many interesting phenomena he anticipates would thus be exhibited, such as the closing of the Sea Anemones (Actiniæ) as the water receded, and their expansion on its return;—this change too might be found highly advantageous to the health and development of those animals whose natural habitat lies between high and low water mark, and whose constitution is therefore framed to require entire or partial exposure to the air at certain intervals of time. A pretty idea, which we trust some of our readers may carry out.
Well now, these preliminaries being settled, we may add more water to the tank,—obtained wherever it is possible fresh from the sea, and if at all dirty, filtered through charcoal before being used. Densely populated as seawater is with minute animal life, it must necessarily be more conducive to the success of an Aquarium than that artificially made. Mr. Hibberd argues the question in this way, that in the latter, the very absence of organic matter is advantageous, since the water is less likely to get out of condition than the seawater, where the germs may decay and putrefy, spreading destruction in all directions,—nevertheless, give us seawater with life in as many of its infinitesimal germs as possible. We can by care guard against
