28 THE SOCIAL LIFE OF ANIMALS 



today. Some, however, evolved the habit of remain- 

 ing attached together after division. This made a 

 beginning from which the many-celled higher ani- 

 mals could develop. With each increase in the ability 

 of cells to co-operate together there came power to 

 increase the complexity of organization of the cell 

 masses. The highly evolved bodies of men and of 

 insects are thus an expression of increasing inter- 

 cellular co-operation which finally reaches a point 

 at which, for many purposes, the individual person 

 becomes the unit rather than the co-operating cells 

 of which he is composed. 



About the same time the German, Deegener, (40) 

 published an extensive treatise on the social life of 

 animals, along the same lines as the book written 

 by Espinas forty years before. Deegener 's distinctive 

 contribution was a classification of the different 

 social levels, from the simplest sorts of artificial col- 

 lections of animals to parasitism and truly social 

 life. His rating of these different aspects of sub-social 

 and social life in one long outline has the great 

 merit of showing that there are no hard and fast 

 lines which can be drawn between social and sub- 

 social organisms, but that social communities are 

 the natural outgrowth of sub-social groupings. Un- 

 fortunately, wdth Teutonic vigor and vocabulary, 

 he designated the different categories in words as 



