light caused by the disturbance they made in passing through the immense shoal of coral polyps. The sight was curious and interesting; it had the appearance of an immense meteor coming directly down on our boat, as they were all heading for the entrance of the harbor where we lay. The bows of the fishing-boats made a great disturbance as they struck them, and the luminosity was most intense; but, as the waves were thrown off from the bows at a wide angle, the disturbance continued, and the colored light from the little creatures formed a long streak from behind the boat, representing the head of a comet with a long tail. Imagine twenty or thirty of these boats all heading in one direction, and you may form a faint idea of the scene. The polyps were not alone, but larger animals were darting and gyrating about, sending out vivid streaks of light. The phosphorescent light of these polyps is probably the effect of a vital action; it appears as a single spark, like that of various insects, and is repeated at short intervals. In 1867 I passed through a belt of dark-colored water in a large stream. It had been observed from the masthead for some time before we reached it: it proved to be a belt, of miles in extent, composed of animalcules. When taken up in a bucket, they gave out the strongest phosphorescent light I have ever witnessed. It required the highest power of my microscope to define them, and they were of many species new to me. Our steamer, a side-wheel vessel, made a great commotion as we passed for hours through this belt of living matter. These belts or patches, covering vast tracts of the ocean, are not uncommon. They are often seen in the Indian Ocean after severe storms and hurricanes. They vary in color. I have seen them of olive green, of a yellowish tint, and often a dark blue. Once, after a spent hurricane at Mauritius, I passed through a belt three miles wide, of a deep purple, so much so it could be seen a long way from shore. Giglioli, the Italian naturalist, refers to the phosphorescence of madreporic polyps as being quite different from that of other forms. He observed on the coast of Sumatra and Batavia, that, when the bottom of his launch grounded upon the polyps, a brilliant display of phosphorescence followed. Doubtless nearly all the Alcyonarian[13] corals are light-givers, and of great importance in the illuminating economy of the ocean. The Alcyonarians include the sea-pens (_Pennatulidæ_), and the sea-fans and the red coral of commerce (_Gorgonias_), and may be briefly described as animals which, as a rule, secrete a horny or calcareous stock, without the true dividing septa that we see in the corals proper.