One of the most brilliant of this group of animals is the _Ilyanthus scoticus_, a kind usually found in ooze, the tentacles appearing at the surface, and gleaming brightly, like the rays of some fixed star. Even when brought up on the dredge, these animals emit a brilliant light. Some of these sea-anemones are said to attach themselves to the shells of hermit crabs; and, if luminous, we may imagine the spectacle of the gleaming, living light-house, moving about at the will of the little crustacean, possibly attracting prey to it instead of being the warning beacon that we might suppose. The anemones being, as a rule, fixed, one naturally likens this one to a light-ship which is drifting about away from its moorings. The sea-anemones well repay examination and study, and thrive well in the aquarium, where their habits and development may be watched. As a rule, they are fastened to the rocks by a sucking disk. Some live in the mud; others float upon the surface, or are parasitic upon the great jelly-fishes. Some, as we have seen, ride about upon hermit crabs, or fasten themselves upon the claws of others; thus showing the greatest diversity in their life habits. The corals may be termed anemones which have the faculty of secreting or depositing lime, and among them are several which at times appear phosphorescent. The little cup-like _Caryophyllia_ has been seen to emit a gleam of light, an idea of which is given in Plate III., Fig. 2. The phosphorescence of reef-building corals has rarely been observed. Col. Nicolas Pike, our late consul to Mauritius, and an enthusiastic naturalist, informs me that he has witnessed the luminosity of their young. The account is so interesting an addition to the literature of the subject in general, that I give the colonel’s letter entire:-- BROOKLYN, N.Y., December, 1886.