The Medusæ have been divided into groups, and distinguished according to their different organs of locomotion. The common idea is that all jelly-fishes are like mushrooms or miniature umbrellas. Such, it is true, is their general form, but others abound both in our own and in foreign seas, that possess a totally different appearance. For instance, some move by means of numerous cilia, or minute hairs that are attached to various parts of their bodies. By the exercise of these organs the creatures glide through the water, and hence they are called _ciliograde Acalephæ_. One of the most remarkable examples of this class is seen in the Girdle of Venus (_Cestum veneris_). 'This creature is a large, flat, gelatinous riband, the margins of which are fringed with innumerable cilia, tinted with most lively irridescent colours during the day, and emitting in the dark a phosphorescent light of great brilliancy. In this animal, too, which sometimes attains the length of five or six feet, canals may be traced running beneath each of the ciliated margins.' This animal, as it glides rapidly along, has the appearance of an undulating riband of flame. Most likely it is the species to which Coleridge alludes in the following passage:-- 'Beyond the shadow of the ship I watched the water snakes They moved in tracks of shining white, And when they reared, the elfish light Fell off in heavy flakes. * * * * * Within the shadow of the ship I watched their rich attire-- Blue, glossy green, and velvet black, They curled and swam; and every track Was a flash of golden fire.' Another of this class is the common Beroë (_Cydippe pileus_); its body is melon-shaped, and covered over by rows or bands of cilia, placed similarly to the treads on a water wheel, one above another. These are entirely under the will of the little gelatine. It can use each or all of them, and thus row itself along at pleasure. But perhaps the most singular portion of this creature is what has been termed its fishing apparatus, though by some writers it is considered merely to be the means by which the Beroë anchors its body to any desired spot. It consists of two exceedingly slender filaments or streamers, which measure many times the length of the Beroë itself. Some writers, again, fancy that these organs are used to propel the animal. This must be an erroneous notion, for if they were cut off, the creature would still continue to move with the same power as before. Nay more, if the little Cydippe be cut into pieces, and the ciliated bands be attached to each fragment, the latter will swim about with the same power as when connected with the entire animal.