-}-2 WAKBI.HR SONC.S. 



have departed from the song - type of the species ; whether 

 there is a recognizable longitudinal variation in keeping with 

 color variation, as the process of differentiation grows toward 

 the formation of sub-species from merely geographical races ; 

 what the difference is between young and old, bright plumaged 

 and dull plumaged birds within the species ; what is the effect 

 of environment upon the same individual to determine its 

 effect upon the species ; how far imitation determines the qual- 

 it}^ of the song of the individual. And so we might go on 

 suggesting topics for study to the end of the page. We need 

 only to perceive that the subject is inexhaustable, and a fruit- 

 ful one for investigation. 



