310 University of California Publications in Zoology. [Vol. 6 



flocking, as well as with that of open ranging. It has shown 

 that sexual selection can only have operated in producing a more 

 sharply defined pattern in the male, but cannot account for the 

 existence of the pattern itself. Recent views as exemplified in 

 Thayer (1909) as to the concealing effect of white markings 

 have been regarded as greatly simplifying the problem and 

 aiding our understanding of the possible meaning of the patterns. 

 This newer view, however, is found to be in perfect accord with 

 the older one known as the Theory of Directive Markings. It 

 restricts the application of the latter, however, to patterns that 

 can be shown to be conspicuous. 



These considerations cannot be regarded as affording evidence 

 in an ultimate sense. They lead at best to the provisional 

 modification of an interpretation that was open to criticism, and 

 tend to check over-emphasis upon the concealing principle in 

 animal coloration. Doubtless they fall short of reaching the full 

 meaning of the white or bright patterns of passeriform birds. 

 Possibly the interpretation of diverse coloration as having de- 

 veloped under conditions of comparative immunity, from such 

 sources of attack as those to which terrestrial animals are subject 

 needs greater emphasis than has been given it. 



