is not alleviated by upward reflection ; while the highly illuminated back has 

 to be of a very dark tone to coalesce with the dark earth, rock, or whatever 

 it may be that forms the animal's normal background. 



These examples serve to illustrate the law, almost or quite infallible, that 

 the range and scale of an obliteratively colored animal's counter shading de- 

 pend on the ratio of the average brightness above it to the average darkness 

 beneath it, in its normal haunts. Thus, to recapitulate, we find on sandy 

 deserts birds, mammals, and reptiles counter-shaded from sand-color to 

 white, while on dark-colored open ground we find them shaded from very 

 dark to white. (Of this last class the smaller Wood Sandpipers (Totanus), 

 which live on muddy stream and pond banks, are excellent examples. So 

 also, in a cruder form, are some of the Oyster-catchers (Hcsmatopus) and 

 Stilts (Himantopus), whose counter shading consists of two tones only, black 

 and white. Among mammals, examples are the darker-backed hares, deer, 

 kangaroos, etc., which live more or less fully exposed to the sky-light on rather 

 dark ground.) Where the sky-light is intercepted and diffused by foliage or 

 other natural obstructions, as on the ground under grasses, bushes, etc., on 

 marsh-land under reeds and rushes, and, most of all, in the forest, we find 

 many rich or dark-colored animals with a weak obliterative shading (one, 

 namely, whose bright climax comes more or less short of white, being even in 

 some cases but slightly lighter than the tone of the back). Many of the for- 

 est-inhabiting passerine birds of Europe and America wear this form of coun- 

 ter shading, as do also certain forest grouse, as well as squirrels and other 

 mammals; while among tropical birds it is well represented by many green 

 parrots and parrakeets, etc., and also by many brown species that inhabit the 

 gloomy interiors of the great forests. Some of the ground sparrows, and the 

 rails, are good examples of the grass and swamp forms, while the female of 

 the European Blackbird (Merula), and the North American Catbird (Galeo- 

 scoptes) may be cited as examples of the thicket-haunting form among fa- 

 miliar birds. This indisputable fact, that animals tend to be dark in thickets 

 and dusky forests, and pale on the glaring desert, and on ocean beaches, is a 



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