particularly those of plumage. Thus we discover, even in the study of the 

 disguising-coloration of the birds of to-day, a wonderful intermingling and 

 gradation between the types, which makes it hard to consider them separately. 

 But division and classification are essential to analysis, and by taking a prom- 

 inent type-center as the theme of a chapter, we can better examine both its 

 differences and its affinities. Those we have already glanced at are perhaps 

 the most representative and notable of the many types of picture-pattern worn 

 by obliteratively-shaded land and beach birds. It remains for us to consider 

 the markings of rails and other swamp birds, of obliteratively-shaded ducks, 

 etc., and also the several obliterative uses more or less independent of counter 

 shading which are served by spots and patterns in birds' costumes. 



55 



