of the body. A name expressive of this peculiarity of movement is applied to the group.

Their movements are ceaseless and ever varying. The action of the paddles on the water produces the most beautiful rainbow tints; and the diversity of aspect which the little creatures present, is increased by two remarkable appendages, which can in a moment be extended and displayed to their full extent, or drawn back into cavities within the body. By means of these the little Beröe can attach itself to the sides or bottom of its glassy prison, and ride, as if at anchor, moored by these singular and delicate cables.

A species of Beröe, of a larger size and different shape, is also found upon our coasts. It is furnished with four curious ear-like appendages, which are ever changing their form. The body is easily broken; and is so very transparent, that on one occasion when I had some of these animals in a jar of sea-water on the chimney-piece, the blossoms of some flowers which were also there, were distinctly seen through them.

The other great division of the Sea-nettles (Acalephæ) is that to which the Jelly-fish, which is so abundantly strewed upon the beach during the summer months, belongs. In the Beröes, we found that the animals moved by means of cilia, or rows of little paddles. The Medusa or Jelly-fish, on the contrary, move by the expansion or contraction of the outer margin of the umbrella-shaped surface (Fig. 16, 19), the animal striking the water in an opposite direction to that in which it is moving. The motion is easy and graceful; and

such is the structure of the body, that every contraction of the margin not only impels the animal in its course, but

assists in the process of respiration. This group is divided into many genera, comprising about three hundred species. Some resemble a mushroom with its stalk; others have arms adapted for seizing; some have one simple central mouth; in others, both its structure and position are different; in some the margin is furnished with long contractile threads, whence

the well-known stinging secretion is supplied; in others, this formidable apparatus is altogether wanting.

The Medusæ differ extremely in size. Some as large as a good-sized umbrella are occasionally thrown upon our coast; others are about the size of peas; and many scarcely exceed in dimensions the head of a large-sized pin.

Some species are adorned with brilliant colours, and equal, in the richness of their hues, the brightest of our garden flowers. When from a small boat they are beheld rising and falling at pleasure, in a glassy and transparent sea, they are objects so very attractive as to excite the astonishment of the child, while they furnish matter for the contemplation of the naturalist.

The quantity of solid material contained in their bodies is much less than would generally be supposed. Professor Owen states that if the fluid parts of a Medusa, which may weigh two pounds, be drained away, there will remain only a thin film of membrane not exceeding thirty grains in weight.

A circumstance illustrative of this singularity of structure may here be mentioned:-A few years ago an eminent Zoologist, now a Professor in one of the English Universities, had been delivering some lectures in a seaport town in Scotland. In the course of these, he noticed some of the most remarkable points in the structure and habits of the Sea-nettles. After the lecture, a farmer who had been present came forward, and inquired if he had understood him correctly, as having stated that the Medusæ contained so little of solid material, that they might be regarded as little else than a mass of animated sea-water? On being answered in the affirmative, he remarked that it would have saved him many a pound had he known that sooner, for he had been in the habit of employing his men and horses in carting away large quantities of jellyfish from the shore, and using them as manure on his farm, and he now believed they could have been of little more real use than an equal weight of sea-water. Assuming that so much as one ton weight of Medusa recently thrown on the beach had been carted away in one load, it would be found that, according to the experiments of Professor Owen already mentioned, the entire quantity of solid material would be

only about four pounds of avoirdupois weight, an amount of solid material which, if compressed, the farmer might, with ease, have carried home in one of his coat pockets.

Perhaps there is no circumstance connected with this class of animals more attractive or more remarkable than the power they possess of emitting a beautiful phosphorescent light; and, in some of the larger Medusa, this is of such intensity, that they have been compared to balls of fire suspended in the water.

Professor Rymer Jones, in speaking of the luminosity of the ocean, which is principally owing to these animals, remarks: “We have more than once witnessed this phenomenon in the Mediterranean, and the contemplation of it is well calculated to impress the mind with a consciousness of the profusion of living beings existing around us. The light is not constant, but only emitted when agitation of any kind disturbs the microscopic Medusa which crowd the surface of the ocean; a passing breeze, as it sweeps over the tranquil bosom of the sea, will call from the waves a flash of brilliancy which may be traced for miles; the wake of a ship is marked by a long track of splendour; the oars of your boat are raised dripping with living diamonds; and if a little of the water be taken up in the palm of the hand, and slightly agitated, luminous points are perceptibly diffused through it, which emanate from innumerable little Acalephæ, scarcely perceptible without the assistance of a microscope."

The phenomenon is not, however, confined to warmer latitudes. Sir Walter Scott, in his "Lord of the Isles," has described it in our own seas:

"Awaked before the rushing prow,

The mimic fires of ocean glow,

Those lightnings of the wave;

Wild sparkles crest the broken tides,
And, flashing round the vessel's sides,
With elfish lustre lave,

While, far behind, their livid light
To the dark billows of the night
A gloomy splendour gave."

STAR-FISHES.-ORDER ECHINODERMATA.

"As there are stars in the sky, so there are stars in the sea."-Link.

THE second great division of the rayed animals comprises all those with a hard or leather-like covering, which, in some species, has prickles like those of the hedgehog. They exhibit, in many respects, an entire contrast to those we have just been considering. The difference of their external covering is obvious to every one; that of the internal structure is not less remarkable.