The polypes of the stony corals, though extremely small, are essentially the same in structure as the Sea Anemone, but they have no sucker at their base. The Sea Anemone is of soft tissue throughout its whole body. In the polypes of the madrepore corals, on the contrary, the whole of the perpendicular lamellæ which divide the interior of the body into chambers become hard, from being consolidated by particles of carbonate of lime; and their upper edges, which appear as rays round the mouth of the animal, give that starry appearance to the surface of dead madrepores after the soft part of the polypes has been destroyed. Most of the coral polypes are unarmed; but in some, as, for example, the Caryophyllia Smithii, there are multitudes of dart-cells in the tentacles, besides numerous pellucid filaments or ribbons, full of thread-cells, lying in coils within the chambers which surround the stomach. We are indebted to Mrs. Thynne’s interesting observations on the Caryophyllia Smithii in her aquarium for the life-history of the animals armed with this formidable artillery. This madrepore, which inhabits many parts of the European seas, at various depths, is a species of the only lamelliform genus of corals which range beyond the tropics. It is a solitary individual polype, with an external calcareous cylindrical coat, wider at the base, when it is fixed to a rock; and the mouth, which has several rows of tentacles, is in the centre of the disk of the cylinder. The tentacles are delicate, transparent, granular tubes, about an inch long, tapering to their extremities, and ending in an opaque white knob full of chambered thread-cells with their darts; but the thread-cells are of a larger size in the ribbons coiled in the chambers round the stomach of the animal. These madrepores are described by Mrs. Thynne as of various tints, from a pure white to a bright apricot colour. At intervals they eject from the mouth a whitish blue fluid, resembling wood smoke, in a stream three or four inches long, sometimes containing a few eggs. But the eggs, though no doubt formed at the base of the lamellæ, become densely packed like fine dust in the hollows of the tentacles, from whence they are expelled by contractions, and escape by the mouth. The eggs lie quiet for a few days in the place where they are deposited: by and by they begin to rotate, slowly at first, then more rapidly, and finally they are developed into most minute madrepores, with the star and colour of the parent. In a few months they become as large as a crown piece, with a very wide mouth and a membranous integument or covering, for they do not get their hard calcareous coat till they are two years old. While in that soft state they propagate by spontaneous division, which always begins at the mouth, and is repeated every few weeks during the second year of their lives. When they split into segments, the broken ends of each segment