59 THE STORY OF THE BIRDS. 
which have permitted her also to acquire or inherit 
color with safety. 
Birds not only change their habits, as we shall see 
(Chapters XXIII and X XIX), but they actually have 
exhibited some eesthetic or moral progress, a question 
the special discussion of which we shall again have to 
pass over. 
A great deal of the story of the birds is involved 
in why they put on “ paint and frills.” 
