BIOLOGY AND SOCIOLOGY 85 



large and warlike pair: — once a worker, always a 

 worker; once a soldier, always a soldier — that is the 

 rule for ants, but not for men. 



The efficiency and biological success of communi- 

 ties depends on the degree and accuracy of the 

 division of labour and co-ordination between the 

 units of which they are built up. This is true of 

 cell-communities and the second-grade individuals 

 or metazoa or multicellular animals and plants to 

 which they give rise,*^ and also of the communities 

 of metazoa and the third-grade individuals to which 

 they give rise, whether the members of such com- 

 munities of higher grade are physically bound to- 

 gether, as in a Hydroid or a Portuguese Man-o'- 

 War, or united only by mental bonds, as are the 

 communities of ants and bees and termites. As we 

 have seen, the individuals are differentiated struc- 

 turally for the different functions which they have to 

 perform. 



This is not so in human species: a man is not 

 born cross-legged to be a tailor, or broad-thumbed 

 to be a miller, or big-armed to be a blacksmith. 

 Even in the hereditary castes of India, the trade or 

 profession is determined by tradition, and not by 

 inborn structural adaptations. 



Still another consequence flows from this educa- 

 bility, this flexible and elastic mental organization. 

 A man can pass from one occupation to another. 



5 See J. S. Huxley, '12, for a discussion of the grades of bio- 

 logical individuality. 



