40 The Direction of Evohttio7i 



nor to make a series of experiments, to find out that water is 

 to be drunk. The bird deprived of the presence of others 

 of its kind does not learn to perfection its proper song. 

 All the remarkable accommodations of an imitative sort, 

 so conspicuous in the higher animals, enable them to 

 acquire the habits and behaviour of their kind without run- 

 ning the risks of trial and error. Calling this store of 

 habits of whatever kind ' tradition,' and caUing the individ- 

 ual's absorption of them and his consequent education in 

 tradition his 'social heredity,' we have a more or less 

 independent determining factor in evolution. For these 

 accommodations are the cream of the needs of life, they 

 represent the essentials of education, the sine qua non 

 in an animal's equipment ; so the accommodations which 

 must be reproduced in race evolution, as adaptations 

 which the species must effect, are in these lines. The 

 influence of organic selection is, therefore, exerted to 

 determine, by the selection and accumulation of varia- 

 tions, the congenital equipment which most readily util- 

 izes and supplements these traditional modes of behaviour. 

 The two factors work together and for the same general 

 result. 



There is, therefore, in tradition a further determining 

 factor. Natural selection plays about it to fix a requisite 

 function here, to eradicate what is unnecessary and non- 

 useful there — in short, by its omnipresent operation on 

 this character and on that, to perfect the individual for the 

 most adapted life. 



It is here also that we touch upon the border line be- 

 tween psychophysical evolution and social evolution, a line 

 which we may not now cross. Suffice it to say that once 

 the community of tradition is established and the fitness 



