white herons, egrets and swans, whose whiteness tends to efface them against 

 the sky, in the view of their aquatic prey and enemies, as no other color or sys- 

 tem of colors could. Outside of the several classes above named, which 

 means among ground birds and birds of the interior forest gloom, white mark- 

 ings are practically wanting, with the exception of those that belong purely 

 and simply to obliterative shading, and the occasional white tail-spots, dis- 

 played chiefly in flight, which we shall consider in a later chapter. 



The foregoing nineteen chapters together form an exposition, however 

 fragmentary, of all the main laws of disguising-coloration as applied to birds, 

 in as far as they have yet been discerned by my father. In truth, although 

 we have disclosed much that is new, even in addition to the big general prin- 

 ciples of obliterative shading and picture-pattern, yet the subject is no more 

 than broached. 



For several reasons we have seen fit to treat of birds in more detail than 

 we shall attempt with other classes of animals. In the first place, birds- are 

 ahead of all other classes, with the doubtful exceptions of fishes and lepidop- 

 terous insects, in the elaborate variety and extreme development of their dis- 

 guising-coloration. (The slender, simple hairs of mammals, for instance, are 

 but a paltry medium for the building up of patterns, relative to the broad, flat 

 and subtile feathers with which birds are covered.) In the second place we, 

 personally, know more about birds than about any other animals. In the 

 third and last place, the main principles of disguising-coloration are the same 

 throughout the animal kingdom, and therefore if one describes them some- 

 what minutely in connection with one representative class, the other classes 

 can be dismissed a great deal more briefly. 



The next three chapters will deal with mammals. 



ii8 



