When we were sailing through the Pacific Ocean, I saw a great many coral reefs and islands; and perhaps there is hardly one of the wonderful things which I have seen in my travels, that I remember with more pleasure, or love more to think about, so I shall be glad to tell you all I know of them. You are acquainted with the appearance of Coral, as you have often seen pieces of it in cabinets, and employed as ornaments; and you therefore know that it always abounds with little holes, but its form, and the shape of these holes, vary considerably. Some of it occurs in branches, like the branches of trees, and in consequence of this, and because it was known to increase in size from time to time, it was taken for a marine plant, before its nature was fully investigated. The openings in this sort are placed in the form of stars, as you will see in this little piece of one of the branches magnified. [Illustration] [Illustration] Sometimes it is in large roundish masses, called brain stones, from its resemblance to the brain of an animal; the openings are then long holes placed in two rows between high ridges, like this. [Illustration] And a third form is found consisting of thin pieces, thinner than writing paper, placed on edge, spreading out from a centre, or from a line down the middle of a long strip, and the openings are then plain deep furrows, running from the middle to the outside. [Illustration] There is also the precious red Coral of which beads and other trinkets are made, found principally in the Mediterranean Sea, and several other sorts, more or less rare. But what I have described to you are the commonest. This curious substance extends over hundreds of miles in various parts of the Tropical Seas, in islands of different forms. But before I describe these to you, I must tell you what is known respecting the little animals by which it is manufactured, for it is proved to be the work of certain kinds of the little creatures called Polypes. THE CORAL-MAKING POLYPES. The Polypes are a kind of animals apparently of very simple structure, without bones, or shells, or heads, or brains. They have very large mouths surrounded by a great number of _tentacula_, or feelers, which are threads of flesh possessing the sense of touch in great perfection; and to these _tentacula_ they owe the name _Polypes_, which comes from two Greek words signifying _many feet_. The ancient naturalists who named them, I suppose did not know but that they were feet. [Illustration: PLATE XIV. ACTINIÆ CORAL BUILDERS]