Now the coral builders are all of the same general character as the Actiniæ, in the construction of their bodies, their various colours, great mouths surrounded by feelers, and habits of taking their meals. But besides their being such wonderful architects, they differ from the English creature in being very sociable, and living together in immense companies. When you read of the Pyramids of Egypt, or of any other great structures, you may justly think them wonderful proofs of what the labours of many men may do when directed to a single object; but here you have not houses, pyramids, cities, nor even mere islands, but whole continents constructed by the combined labours of little insects. I cannot tell you, neither can any one else, in what manner these little workmen perform their work. It is only certain that they have some faculty by which they appropriate the particles of carbonate of lime contained in the sea water, and dispose them in the various forms I have mentioned to you. When the coral is in progress, it is coated with a soft gluey sort of substance, and over the star-like clusters of openings, there may be seen, when the creatures are hungry, little rosettes of tentacula, more beautiful than you can conceive. In fig. 2 of the plate, you may see some of these animals showing their rich rosettes on a piece of branch coral, such as is represented in the first wood cut, page 204. There is another sort of branch coral, where the animal always lives at the end of the branch, the whole of which it has to itself, and will then spread out its tentacula in a star on the extremity, as you may see in figs. 3 and 4. In fig. 5, you may see one of the animals which construct the sort of coral represented in the cut, page 205. Since these little creatures can lay down their tentacula in the openings of their stony houses, when they are not hungry, or when they are alarmed by the approach of anything that would hurt them, they do not want the tough skin with which the Actinia is covered, but have bodies of a very soft and yielding texture. FORMS OF THE CORAL REEFS.