564 THE POPULAR SCIENCE MONTHLY 



apply to the evolution of all animals. Their races are, in the long run, 

 subject to great fluctuation of prosperity, many of them coming, oc- 

 casionally, 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 them- 

 selves 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 individ- 

 uals 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 eat- 

 ing 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. 4 



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 ani- 

 mals; 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 nickering 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 



4 This applies to all such cases as the objection that seated butterflies are 

 apt to have their wings closed, and therefore need no concealment-colors on their 

 upper sides, and that flamingoes seldom prey on animal food that can see, and 

 therefore have little need to match the sky against which they loom. The 

 butterfly's fitness for opening his wings in safety, when he needs to do so, and 

 the flamingo's, for eating seeing-iood when he must, are distinct advantages. 



