RELATIONSHIPS IN THE ENVIRONMENT 135 



previously evoked response, is there unresponsive; 

 or again, it goes in search of food and collects 

 with other males bent on a similar errand, and 

 in presence of what we know would be an 

 exciting influence under other circumstances, 

 it nevertheless remains silent. Hence the 

 relationship between the song and a male rival 

 seems, as in the case of the headquarters, to 

 depend in the first instance upon the occupation 

 of a territory. 



So that the relationship between the song 

 and the territory as a whole is clearly of a 

 different order from that which obtains between 

 the song and the headquarters, or the song and a 

 male rival ; for the first, as far as can be judged 

 by observation, is exclusive of, whilst the second 

 and the third involve, cross-correlation. How 

 are these facts to be explained ? We have 

 already seen that it belongs to the nature of the 

 male during the season of reproduction to 

 establish itself in a definite place, and this action 

 is just as much a part of its hereditary nature as 

 the building of the nest is of that of the female, 

 and it is just as necessary for the successful 

 attainment of reproduction. What exactly the 

 stimulus is to this mode of behaviour we do 

 not know ; we can go no further back than 

 the internal organic changes which are known 

 to occur and which we assume, not without 

 some reason, are responsible for its initiation. 

 Granting, then, that there is this congenital 

 disposition, what relation does it bear to the 

 song ? Without a doubt the song is likewise 



K 2 



