understood that where real sea water can be easily obtained, as at spots near the coast, it is undoubtedly the best, though, in some respects, the artificial preparation is preferable, because less liable to certain eccentric changes of constitution, which will fall under our attention further on. Sea-water contains the spores of plants, and the germs of many forms of animal life which may have development in the tank, and when these births occur, it is a special gratification to the possessor. But such germs may also decay, and cause putrescence; and if a tank is neglected, the water is liable to get cloudy, the stones black, the sides of the vessel semi-opaque, and the animals diseased. Death soon sets his black seal on the undertaking when such a state of things occurs, and the collection, however costly or well formed at first, may be lost. Now such misfortunes as these are preventible, as it will be my duty to show presently, but I here call attention to the fact, that artificial sea-water is much less liable to get out of condition from the very absence of organic matter, which on first reflections, we should regard as a disadvantage. Thus, the prepared material has certain advantages over the natural; we lose the chance of rearing new additions to the stock through the introduction of minute organic germs; but incur no danger of those same germs perishing and polluting the bright lymph.
But artificial water is quite unsuited for animal life of any kind, until it has been brought into condition by means of growing weeds for eight or ten days, and for crustacea, star fishes, and fishes proper, it is not suitable till it has been in use for many months, and even then
