CHAPTER IX 



THE INFLUENCE OF IMITATION IN RELATION 

 TO BIRD-SONG 



IN the voices of animals, hereditary similarity, in- 

 voluntary or passive imitation, and voluntary or 

 active mimicry, blend insensibly from one to the 

 other. The influence of resemblance is to be 

 observed throughout the animate world. Mere 

 physical resemblances to things or to organisms 

 are of vital importance to vast numbers of creatures 

 which they continually protect. Whether the 

 primary causes of these resemblances were fear, and 

 consequent efforts towards concealment, giving rise 

 to ocular impressions, which have found physical 

 expression through the agency of generation ; or 

 whether their origin may be discovered in the in- 

 fluence of the protection afforded by similarities of 

 form and of colour, inducing selection by enemies, 

 who would see first the most noticeable of their 



