22 THE POPULAR SCIENCE MONTHLY 



ever between the overhead light which is their ceiling, and the under- 

 foot earth which is their floor. The higher you mount from the earth, 

 and consequently the nearer you get to the outside of this zone of 

 detached objects, the more do all things that you have to look at come 

 between you and the brown earth — and the more these things resemble 

 the earth in color the less you notice them. Contrariwise (let the 

 world for the first time notice this Contrariwise, which would have saved 

 Eoosevelt and others so much erroneous writing), contrariwise, the 

 nearer you get to the bottom of this layer of inhabitants of the atmos- 

 phere, i. e., close to the earth's surface, the more you have only things 

 above you to look at; and the more these things are bright like the sky 

 the less you see them, and the darker they are the more you see them. 

 This means that the nearer to earth's surface an animal lives, the larger 

 will be the proportion of neighbors he detects by seeing them dark 

 against the sky. Only such neighbors as are no taller than he will 

 escape coming between him and his sky. 



After years of trying to bring home to naturalists this great fact, 

 which wholly suffices to account for white top-patterns in general, I 

 know to my sorrow that nothing short of seizing them all and binding 

 them to the ground, so that their eyes will be as low as a mouse's, will 

 ever cause the truth to spring into vital existence for them ! I have 

 demonstrated to many audiences on both sides of the Atlantic where 

 scarcely one man would consent actually to go down on the turf and let 

 this immense fact rush upon his consciousness. 



Everywhere, in every situation, it is the rule that animals are col- 

 ored like the background that most concerns their feeding and escaping 

 attack. Sea-birds, in general, are either all ocean- and sky-colored, or 

 this with the addition of the color of the rocks they breed and roost on. 

 Animals living between bare snow and sky are white. (I have shown by 

 ocular demonstration the wonderful aid that this white background- 

 matching gets from the small black marks commonly worn by these 

 white species.) Sand-dwellers, on land or in the sea, are sand-colored. 

 One can find pictured on a locust the peculiarities of the special type 

 of ground he lives on, be it rock, or sand, or meadow. Everywhere, in 

 every case where the animal's background is most unvarying, as in the 

 above-cited instances, the animal's colors are at least amply accounted 

 for by their matching of this background. 



Now why is it that even after people intellectually perceive that a 

 terrestrial mouse or lizard sees almost all sizable neighbors against the 

 light, and detects them least when they look lightest — why is it that 

 these people go on failing to undersand that white upper slopes on all 

 species which need to avoid the sight of these mice and lizards are just 

 as necessary to their wearers as is the brownness of the mouse or lizard, 

 whose enemy looks at him from above downward and consequently sees 



