rrurosF. or so\<; 151 



sequential order we have the following: (1) 

 internal organic changes which lead to isolation, 

 (2) the appropriate environment which gives rise 

 to an impulse to remain in it, (.'5) the occupation 

 of a territory which is the condition under which 

 the instincts are rendered susceptible to stimula- 

 tion, (4) the various stimuli. Each is dependent 

 upon that which precedes it, and no part can be 

 subtracted without failure of the biological end 

 in view, neither can the different stages be 

 combined in different order. So that, in 

 considering the significance of song to an 

 unestablished male, we are dealing with the 

 situation at a point at which all the latent 

 activities have not been fully felt, for all that so 

 far has occurred is the change from sociability to 

 isolation determined by internal organic changes. 

 The bird has not established a territory because 

 it has not come into contact with the appropriate 

 environment, and it is not pugnacious because 

 the condition which renders its instinct suscept- 

 ible is absent ; and so, as it wanders from place 

 to place and hears the voices of males here or 

 males there, it merely behaves in accordance 

 with that part of its nature which predominates 

 just at that particular moment the impulse to 

 avoid them. 



But given the appropriate environment, 

 given, that is to say, just that combination of 

 circumstances which might bring into functional 

 activity all the latent instincts of the intruder, 

 and no matter how vociferous the occupant of 

 a territory might be, it would not be preserved 



L2 



