CHANGE OF TRADITION IN THE CASE OF CHIMNEY SWIFT. 59 



their offspring and by the experienced leaders to the multitude, and 

 responded to by the instinct for imitation possessed by the young and 

 inexperienced, will establish and perpetuate a more or less constant 

 social, or habitudinal, type. And it should be especially noted that 

 the habits thus transmitted from generation to generation determine 

 the relations of the group to the environment, and, therefore, the form 

 of selection that continues with cumulative results in successive gene 

 rations. The influence of habitudinal generalization is illustrated by 

 the following case: 



4. Change of Tradition in the Case oj tin ( 'himney Swift. 



The chimney swift of eastern North America, often called the chim 

 ney swallow, has made an important change in its habits since the 

 settling in this region of Europeans who build houses with chimneys. 

 We know that before the coming of the European the traditions of this 

 bird determined that hollow trees should be occupied as the appro- 

 priate places for their nest-building. How the present tradition, giv- 

 ing the preference to chimneys, was started, we are not informed ; but 

 we mav believe that a pair of birds of an investigating spirit, finding 

 that the hollow trees in which they and their ancestors had been in the 

 habit of building had been cut down, ventured to make the new experi- 

 ment. Being rewarded with success, election is on their side, and 

 their descendants survive to perpetuate the habit. Other birds of 

 the same species see their success and follow their example; and as 

 chimneys are multiplied, while hollow trees are diminished in number, 

 the followers of the new habit in time outnumber the adherents to 

 the old tradition, and from that time on the old conservative habits 

 crumble rapidly away. The vast majority of the species have now 

 abandoned the old tradition, and the newer tradition now prevails 

 everywhere, except in the Dismal Swamp (a region about ,^o miles in 

 length and 10 miles in width, in the States of Virginia and North Caro- 

 ina), where their unconscious helper has failed to erect his chimneys. 



5. 1'he Two Methods oj Adjustment. 



Aptitudes are inherited forms of adaptation resulting from tentative 

 variations accumulated by the survival of the fittest. Habitudes are 

 traditional accommodations (that is, traditional forms of adjustment), 

 resulting from tentative innovations accumulated by repetition and 

 imitation of successful experiments. 



Adaptation in plants and in the lower types of animals is gained 

 chiefly by variation in the degrees of innate qualities and in the inten- 

 sity of innate activities, molded in successive generations by the sur- 

 vival of individuals having the fittest endowments in each isolated 



