114 DISPOSITION TO DEFEND THE TERRITORY 



is always the possibility of invasion by an 

 individual whose development is backward or 

 which has been unsuccessful in making good 

 the first step, and, as we saw in the case of the 

 Reed-Bunting, a portion of the ground won 

 may be lost; there is always the danger of 

 gradual encroachment by neighbouring owners ; 

 and there is even a possibility that a pair may be 

 so persistently harassed by more virile neighbours 

 as to forsake the locality permanently. If then 

 a male is to attain a full measure of success it 

 must be capable of keeping its boundaries intact 

 up to the time when the young are able to fend 

 for themselves, and consequently it is important 

 that its intolerant nature should remain suscep- 

 tible to stimulation throughout the greater part 

 of the season. 



Does the presence of a female serve to 

 promote this end ? Now we know very little of 

 the influence exerted by one sex upon the other. 

 Professor Lloyd Morgan has suggested that the 

 male raises the emotional tone of the female, a 

 suggestion which seems to me in accordance 

 with the facts. There is reason to beUeve, how- 

 ever, that the converse is also true— namely that 

 the excitement of the male reaches a higher level 

 of intensity when a female is present. Granting 

 then that his emotional tone is raised, how will 

 this affect the question ? So great is the 

 difference of opinion as to the part that the 

 emotions play in furthering the Ufe of the 

 individual that one hesitates to accept any 

 particular one. But it seems to be generally 



