When first these cases of imitation, or mimicry as they are called, began to be noticed,[11] nobody could tell what to make of them. It seemed plain that one animal could not purposely make itself like another one—or like a twig or a flower—in the way that an actor dresses up to represent some character on the stage. But how, then, had such marvellous resemblances been brought about? Chance seemed quite out of the question, but nobody had any better explanation to give. The whole thing was a mystery. Gradually, however, the subject came to be better understood. One thing was clear: that the animal—or one of the animals—presenting this extraordinary likeness was always benefited by it. At last came Darwin, who explained everything by natural selection, the principle of which is this, that as no two individuals of any species are born quite alike, some must be born with some sort of an advantage over others, and as these would live longer, and leave a greater number of descendants to inherit this advantage—whatever it might be—all living creatures must, gradually, be getting better and better adapted for the kind of life they have to lead. Supposing, therefore, that two different creatures, living in the same country, had some slight resemblance to one another—and this would not be wonderful—then if this resemblance was an advantage to one of them, it would gradually get more and more like the other, because those individuals that were less like it would get killed off sooner, whilst the others would live longer and leave a greater number of offspring, to carry on the likeness. Those orioles, for instance—to take our last example—which least resembled the friar-birds, would get soonest killed by hawks and kites, whilst those that most resembled them would be most let alone, and so they would lay more eggs, and rear more young birds, and of these young orioles, some would be even more like the friar-birds than their parents, and so it would go on. The gradually increasing resemblance would be like a portrait that was always being painted and painted, and having finishing touches put to it, without ever being quite finished—an eternal sitter with an eternal artist in front of him; for the sitter, too, would change as time went on, and as he did, so would his portrait have to. This is how Nature, the great artist, paints her portraits, so that when, in speaking of these cases, we say that one creature mimics another we really mean something quite different. Still, mimic, we are told, though it conveys a wrong meaning, is the best word to use, because with it we can express this wrong meaning in so many different ways, having at our disposal “the convenient series of words—mimic, mimicry, mimetic, mimicker, mimicked, mimicking.” So we should not call something that is white, white, if, with more flexibility, we could describe it as black—and this, indeed, with the converse, is a principle very much in vogue. The curious thing