Thus ever in gloom, yet in a state of constant safety from storms and the agitations of the upper air, the thousand forms of low organic life and cryptogamic vegetation live and thrive in peace and quietness.

“The floor is of sand like the mountain drift,
And the pearl-shells spangle the flinty snow;
From the coral rocks the sea-plants lift
Their boughs, where the tides and billows flow.

* * * * *

“And life in rare and beautiful forms
Is sporting amid those bowers of stone,
And is safe, when the wrathful spirit of storms
Has made the top of the waves his own."[C]

[Footnote C:  Percival.]

Upon the bottom, at various depths, lies that brilliant Radiate—­type of his class—­the Star-fish.  These are quiet and harmless creatures, and favorites in the aquarium, from the pretty contrast they make with marine plants and other objects.

The perfect transparency, elegant form, and graceful navigation of the Medusae, or Jelly-fishes, render them much admired in their native haunts, and prized for the aquarium.  But they are very delicate.  How beautiful and remarkable are these headless Discophori, as they float, and propel themselves with involutions of their disks and gently trailing tentacles, and the central peduncle hanging far below, like the clapper of a transparent bell!  And yet these wonders are but so much sea-water, inclosed in so slight a tissue that it withers in the sun, and leaves only a minute spot of dried-up gelatinous substance behind.

Finally come the Fishes, many of which are of similar genera to those recommended for the fresh-water tank.  The Black Goby is familiar, tamable, but voracious; the Gray Mullet is very hardy, but also rather savage; the Wrasses are some of the most showy fish,—­called in some parts of the country Cunners,—­and of these, the Ancient Wrasse, (Labrus maculatus,) covered with a network of vermilion meshes on a brown and white ground, is the most elegant.

Some points of general management are so important, and some dangers so imminent, that we cannot pass them by unnoticed.  The aquarian enthusiast is very apt to be in too great haste to see everything going on, and commits the common error of trying too many things at once.  The aquarium must be built up slowly and tentatively, object by object:  plants first, and of the simplest kinds; and not until they are well settled, and the water beaded with oxygen bubbles, should we think of introducing living creatures,—­and even then only the hardier kinds of actinias, mollusks, and crabs.  All delicate animals must be intrusted one by one to their new home, and carefully watched for deaths and decay, which, whether arising from dead plants or animals, ruin everything very quickly, unless they be promptly removed.  For sulphuretted hydrogen, even in very minute quantities, is sure death to all these little creatures.