170 THE ZOOLOGIST. 
inherited or instinctive knowledge comes into play, and may 
explain the actions of the birds when human enemies happen to 
be absent. I may add that, when the evolutions become com- 
plex, they surpass the stage which may be regarded as imitative 
of the spray. While the simple spray-forms are retained, and 
are incorporated with the more complex evolutions, these move- 
ments evidently cannot be reduced to a common term. 
In other words, one may say the simpler evolutions are 
imitative in character and protective in purpose; in the com- 
plex evolutions the simpler imitative movements are partially 
hidden by the development of a wealth of movement which is 
still protective in purpose, but which, as regards character, is 
incapable, at present, of a simple and comprehensive explana- 
tion. 
