But when men became still more highly civilized they thought more deeply about things, and began to ask each other what caused day, and night; and heat, and cold; why the Moon grew from a little bright streak into the brilliant full orb, and a multitude of other questions. There was no one to answer these questions, and so the wisest men set to work to study it all out. They found out a great deal, but, of course they made a great many mistakes that had to be set right afterwards by other learned men. Very early they made investigations into the nature of coral. For a long time they were sorely puzzled. In the first place they decided it was a mineral because it was so very hard, and took such a beautiful polish. But, after further examination the wise men all came to the conclusion that it was a plant. It looked like a plant. There could be no doubt about that. The large specimens examined had trunks composed of layers or rings, very much like many trees. From this trunk were branches, covered with a rose-colored bark in which were some curious depressions. [Illustration: FISHING FOR CORAL IN THE MEDITERRANEAN SEA.] Others made a still closer examination, and discovered that these depressions were really little star-shaped flowers, with several colored rays. This settled the question. Of course, if coral produced flowers it must be a plant; and, as a plant, it was spoken of, and written about for two thousand years. “But,” it was asked, “how can a plant grow into a substance as hard as a stone? There is nothing else of such growth known in nature. It is impossible.” The sailors and coral fishers answered this question by asserting that the coral was in a soft state under the water, like any other plant; but when it was exposed to the air it became petrified—that is, turned into stone. It would not have been a very difficult thing for the learned men to have investigated this matter, and tried for themselves whether it was soft and flexible under the water. But they never did, and so _that_ question was settled. It was settled for twenty centuries. At the close of that long period of time a French physician, named Peyssonnel, while traveling along the Mediterranean coast, became much interested in the coral fisheries carried on there. He examined the coral flowers with great care, and found that they were not flowers at all, but animals! The ancients had been deceived by their flower-like form, for they were unlike flowers in every other respect, having no stamens, or pistils, or pollen, and producing no seed.