BOUNDARIES DETERMINED BY HABIT 9 



headquarters, especially as regards the direction, 

 frequency, and extent of the journeys ; and 

 we discover not only that these journeys pro- 

 ceed from and terminate in the special tree, 

 but that there is a sameness about the actual 

 path that is followed. The bird takes a short 

 flight, searches a bush here and some rushes 

 there, returns, and after a while repeats the 

 performance ; we on our part mark the extreme 

 limits reached in each direction, and by con- 

 tinued observation discover that these limits 

 are seldom exceeded, that definition grows more 

 and more pronounced, and that by degrees 

 the movements of the bird are confined within 

 a restricted area. In outline, this is what 

 happens in a host of cases. By repetition 

 certain performances become stereotyped, cer- 

 tain paths fixed, and a routine is thus estab- 

 lished which becomes increasingly definite as 

 the season advances. 



But while it would be quite untrue to say 

 that this routine is never departed from, and 

 equally profitless to attempt to find a point 

 beyond which the bird will under no circum- 

 stances wander, yet there is enough definition 

 and more than enough to answer the purpose 

 for which the territory has, I believe, been 

 evolved, that is to say the biological end of 

 reproduction. Again, however, the process of 

 adjustment is a complex one. Habit plays its 

 part in determining the boundaries in a rough 

 and ready manner, but the congenital basis, 

 which is to be found in the behaviour adapted 



