THEORIES OF MIMICRY 563 



or arboreal beast, and lost it in the trees, the eye searches every mass of 

 foliage silhouetted against the sky, scarcely counting on discerning the 

 creature's outline, so much as on noting some mass of unbroken dark — 

 dark without any sky-hole through it — sufficiently extensive to contain 

 the animal itself. Into this mass, if one wish to kill the animal, one 

 shoots, at a venture, and very often with success. In such cases, a single 

 white mark on the concealed animal has a great chance of showing 

 through the foliage, and saving the creature's life by passing for sky, 

 making the hunter think he can see through the clump as if there were 

 no opaque animal in it. 



This wonderful universal function of top-white will only begin to 

 have vitality in the minds of students of natural history, when they 

 begin to take the trouble to spend hours, lying flat on the ground, 

 studying terrestrial life from the true point of view. They will at last 

 realize that the terms " cryptic " and " conspicuous " can refer only to 

 the relation of objects to their background, and that a hare is as con- 

 spicuous, dark outlined against the sky, to the little mouse at his side, 

 as the white heron looked at on the ground by man ; while to the mouse, 

 this same heron, now seen against the sky, is the perfection of pro- 

 cryptic coloration, just as is the hare seen from the level of a man's or 

 hawk's eyes. 



There is one more point that particularly bears on the skunk matter. 

 There is not, through all his range, any mammal, unless one counts the 

 porcupine (an animal to resemble which would be a protection) with 

 which any other creature could possibly confuse him, except when he is 

 very dimly seen, either by virtue of darkness or of interposed forms, 

 and in either of these situations, as this article has shown, the light 

 pattern only diminishes his recognizability. Do we not, in fact, forget 

 the evidence that the wild animals know each other by far more subtile 

 means than we might suppose ? The dog, even after all these centuries 

 of domestication, still keeps the power to recognize his master, not 

 merely by his scent, but by his foot-fall, when he can hot see him. And 

 the kind of faculty implied by this is even strong in the wild races of 

 man. 



Many naturalists think that such circumstances in the life of a race 

 as are of only occasional occurrence have no part in its evolution. His- 

 tory seems to demonstrate the opposite. It is the stresses that are 

 formative, and are the weeders-out of weak elements. The men of a vil- 

 lage, regardless, for instance, of whether all of them could swim, might 

 go yearly all summer to their meadows, and all come home at night, till 

 once when some sudden deluge swept their valley, only the strong swim- 

 mers would escape, and thenceforth that village would comprise only 

 strong swimmers. How often do we hear some one tell of a small and 

 half forgotten faculty having saved his life. This seems equally to 



