Page:Popular Science Monthly Volume 75.djvu/570

564 apply to the evolution of all animals. Their races are, in the long run, subject to great fluctuation of prosperity, many of them coming, occasionally, near to extermination in some part of their range. This, according to universal belief, is oftenest through famine, and in that case, plainly, those individuals best able to accommodate themselves to new food, and to new methods of procuring it, would be most apt to survive. For this reason it does not signify whether badgers, etc., eat a larger or a smaller proportion of seeing food, since those individuals best fitted to catch it will ultimately constitute the race, because, while a white-topped animal would be no worse than a plain one at eating turnips, he would excel him at catching mice and crickets when turnips chanced to fail; and, as this article shows, his white does not in any way increase his conspicuousness.

Patterns of animals are like scars of ordeals, recording what their wearers have been through. Those hares and antelopes and deer which, by virtue of a white sky-imitation on their rears, were not too fatally good a target against the night sky for the stalking feline that flushed them, have survived to propagate their race. The same record of how they escaped the eyes of prey or enemy is found on the costumes of most of the animal kingdom.

Let us try to get a vivid view of the whole field of the world's animals; over the whole earth, all species, of all orders (that ever prey or are preyed on), wear, regardless of all possible needs of badge or mimicry, such colors, and nothing but such colors, as are to be found in certain of their backgrounds. Nothing but failure to perceive this broad fact has made it possible for all these rootless theories to gain a foothold. The two most recent theories, Professor Gadow's, and that of several experimenters, that humidity is the cause of patterns, both these are invalidated by the same general arguments. Dr. Gadow, who believes that it is shadows flickering over a lizard's back that cause his patterns, ignores the unmistakable fact that lizards, like all other terrestrial species, are colored and patterned to match the ground on which they live, no matter whether there be vegetation over head to cast shadows, or, as on sea-beaches and bare rocks, nothing but air and sunlight. The humidity theory has the same defect. It believes that the increased richness in the colors of a species as one traces it from the arid part of its habitat to such a region as the moist-aired gulf-state forests, arises from the increased humidity, not noticing that with the increase of