The Corallium Johnstoni, a native of the Atlantic, has a white axis, with branches spreading flatly and horizontally like a fan from the rock to which it is attached; it is entirely covered with a yellowish flesh, but the polypes only inhabit the upper surface, as if they could not live in shade. The Corallium secundum, a similar zoophyte, was discovered by Professor Dana near the Sandwich Islands, with a white or rose-coloured fan-shaped stem and branches, covered by a scarlet coat, having the polypes also only on the upper surface. The Pennatulidæ, or sea-pens, which are the third family of the Alcyon zoophytes, bear a great resemblance to a goose’s feather. The genus Pennatula has a flatly-feathered, upright, calcareous axis, the bare part of which is analogous to the quill; but, instead of being fixed like the stem of a Gorgon, it is merely stuck into sand or mud at the bottom of the seas, while the upper feathered part, containing the polypes, remains in the water. The axis decreases in thickness upwards, and the pinnules, which diverge from it transversely like wings, are angular, thin, membranaceous, and strengthened by spicules. The whole animal is covered with a soft fleshy tissue; the polypes, which have eight pinnated tentacles, are arranged in a single row along the edges of the pinnules, with their visceral extremities prolonged into the soft tissue, so as to give it a tubular structure, through which the nourishing juice prepared by the polypes is carried for the maintenance of the general envelope, the refuse being thrown out at their mouths. When the sea-pens leave the mud or sand, they do not swim actively with their pinnules, but move languidly at the bottom. The Pennatulæ are phosphorescent; they are of a dull reddish brown during the day, but at night they shine with the most brilliant iridescence. In the tropical seas they occasionally exceed a foot in length; in the cool latitudes they are not more than five or six inches. The Pennatula phosphorea, found on the British coasts, has a hollow axis, occupied by a well-developed stylet; long pinnulæ symmetrically disposed on each side of the middle and upper part of the axis; the polypes, which are very contractile, are arranged transversely on their upper and anterior edges; the pinnæ of the wings are scythe-shaped, and furnished with a vast number of sharp spicules, and these combine in bundles at the base of the cells, in which the polypes live. The back of the pen, lying between the feathery wings, is sometimes smooth, sometimes crowded with scales, arising from the development of the spicules with which it is filled. The eggs of this animal are yellow, and have the size and form of poppy seeds. They are developed into ciliated larvæ within the polypes, which come out at their mouths, and swim away; but their activity is much diminished when they have acquired their mature form. These Pennatulæ increase also by a kind of budding. There are species of