BIOLOGY AND SOCIOLOGY 83 



become a soldier by picking up a 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 communities 

 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 multi- 

 cellular 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 communities of higher grade 

 are physically bound together, 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 structurally 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. 



1 See J. S. Huxley, 'ii, for a discussion of the grades of 

 biological individuality. 



