Seeing that all corals are derivable from the sea-anemone (some form of which must have been the original ancestor of the whole family), and that the sea-anemone has been proved to be very distinctly an animal, I trust that the animal nature of the corals is now too firmly fixed in the reader’s mind to be shaken by their vegetable fixity, vegetative growth and form, or even by the fact that I am about to explain, viz. that the majority of corals do _not_ obtain their nourishment by the capture of prey, but by the decomposition of the carbonic acid gas contained in the sea-water, a method of feeding which is the most distinctive feature of plant-life as opposed to animal. To recapitulate the well-known and fundamental fact of the life of this world, the plants are characterised by their taking up carbonic acid gas which, by the power of sunlight upon their green matter, they split up in some way so as to form starch from the carbon with water, while the oxygen is liberated back into the air. The animals, on the other hand, eat the food ready prepared for them by the plants, which is consumed in their bodies, and burned, as it were, back to carbonic acid, which land-animals get rid of in breathing. So there is a balance, the oxygen necessary to animal life being freed by the plants from the carbonic acid given by the animals, which carbonic acid is the necessary food-stuff of the plants. The process in the sea is exactly similar, only that the gases concerned are dissolved in the water and rarely separate and become visible as bubbles. Fishes give off carbonic acid gas, dissolved in the sea-water, from their gills, and this is broken up by the seaweeds which liberate the oxygen from which the fishes and all animals re-form carbonic acid gas. Now the amazing thing about the corals is that the polyps have entered into an alliance with certain microscopic plants which come to live in their bodies, and they feed upon the starchy products these plants form in sunlight, and even upon the plants themselves. So intimate is the union of these strange partners that neither can live without the other, the coral has lost its independence, and in fact as well as in appearance leads the life of a plant. At the first sight of a coral sea one wonders what takes the place of the great beds of brown and green weed which fringe British shores, and are a source of the oxygen essential to animal life. The discovery of these plant partners of the corals gives the answer. This easy life, this evasion of the necessity of capturing prey, is doubtless the reason for the degeneration of the polyp structure noticed above.