and noncommital conspicuousness, they tend to draw and hold the eye's 

 attention,— in a sense, to dazzle it, so that it less readily discerns the faintly 

 shown snow-white body of their wearer. The working of this principle is 

 illustrated by Figs. 104-106. Most ptarmigans have black tails, which, folded 

 and largely hidden by white ' coverts ' when the bird is skulking, show as nar- 

 row, sharp black marks, drawing the eye to a point away from the bird's 

 rotund body, 'dazzling' it slightly, and presenting it with a view of what 

 might be a little twig or stone or other dusky landscape-detail. Some ptar- 

 migans in white winter plumage have also a black face-mark, which serves 

 the same purpose, and also masks the bird's round and lustrous eye, in the 

 manner explained in Chapter XIV. The Snowy Owl and the White Ger- 

 falcon are more profusely flecked with 'distractive' black marks. Notwith- 

 standing the special inherent 'dazzling' function of such markings, they all 

 belong essentially to the ' picture '-pattern class. For, if they did not also 

 look like dark landscape-details, they would in the long run tend to reveal 

 rather than conceal their wearers. The northern weasels in their white winter 

 dress have 'distractively' jet-black-tipped tails. Polar Bears and Arctic 

 Foxes have no such markings, unless we count their black snouts and dark 

 eyes. Very likely such beasts when they are skulking partly close their eyes, 

 masking their too characteristic circular or oval form. The little Thibetan 

 Snow Bear (Ailuropus), on the other hand, has more than a mere 'distrac- 

 tive' display of black in its white costume. Its legs, its ears, and a narrow 

 shoulder-mantle are solidly black, and it has black spots around its eyes. 

 Thus it is well fitted for obliteration or great inconspicuousness against 

 either snowy ground or sky, in a country full of dark boulders or bushes, 

 or both.* In much the same manner, and presumably for life amidst back- 

 grounds of the same general aspect, is the Kamchatkan white-shouldered Sea 

 Eagle disguised. But in his costume the dark preponderates over the white. 



One more principal phase and function of mammalian sky-matching 

 costume remains to be described. That is the 'obliteration' of fleeing deer, 



* The white breast-marks of several of the black bears belong in this same class of obliterative patterns. 



152 



