298 RELATION OF TERRITORY TO MIGRATION 



life of the individual, for biological interpretation 

 there is only one end, the prospective value of 

 which is the continuance of the race. We may 

 say that the latter phase is the more important 

 of the two because it is directly concerned with 

 reproduction. But we shall make a great mis- 

 take if we attach peculiar importance to one 

 phase, or to one mode of behaviour within that 

 phase, or to one action within that mode of 

 behaviour ; for if there is one thing certain it is 

 that the whole is an inter-related whole in which 

 each part depends for its success upon that 

 which precedes it. 



In that phase in which the territory is the 

 central feature of the situation, the struggle 

 for existence is in operation in its acutest form ; 

 all the congenital and acquired capacities of the 

 bird pugnacity, song, capacity to utilise in 

 later phases the experience gained in prior 

 phases, all these are organised to subserve an 

 end a proximate end which in its simplest 

 terms may be described as " isolation." Isolation 

 is then the first step in the process of reproduc- 

 tion, and any individual that fails to make it 

 good, fails to procreate its kind. But isolation 

 implies separation, and the degree of separation 

 varies in different species, from the few square 

 feet of cliff required by the Guillemot to the 

 few square miles of barren moor over which the 

 Peregrine exercises dominion. One species must 

 occupy sufficient ground to enable it to secure 

 food for its young ; another requires sufficient, 

 but no more, upon which to deposit its egg ; and 



