CHAPTER THIRTEEN 



A society 

 defined 



Cooperation 

 of parts in 

 single-celled 

 organisms 



Cooperation 

 of cells in 

 many-celled 

 organisms 



SOCIAL LIFE 



I. SOCIETIES, whether among men or animals, are 

 groups of individuals associated together for common 

 ends. 'Plant societies," sometimes referred to by 

 botanists, are groups of plants growing together, but 

 without the features of a true society ; they are better 

 called "plant associations." It is true that in forests 

 the trees protect one another from the violence of the 

 winds, and that in rather numerous cases different forms 

 of plants cooperate for mutual benefit. For example, 

 plants of the pea family have bacteria growing in their 

 root tubercles; and these bacteria, being able to "fix" 



- or make part of an available chemical compound - 

 the nitrogen of the air, are in turn highly beneficial to 

 their hosts. Such intimate relationships between differ- 

 ent species are defined by the term symbiosis (Greek, 

 "living together") and are not properly called societies. 



2. Nevertheless, even in the lowest plants and ani- 

 mals the parts of the cell may be said to be joined to- 

 gether for common ends, the cell being a complex 

 machine. Thus no life can exist without a sort of rudi- 

 mentary socialization of the parts of the individual, and 

 it is the interplay between these which makes life. The 

 principle of cooperation may in this sense be said to 

 have begun with life itself. 



3. In a still more obvious sense, socialization was 

 manifested when the first two cells remained together, 

 to make the beginnings of a many-celled animal or 

 plant. Very soon the cells thus associated began to 

 develop along different lines, and the several types of 

 tissues were formed. A human being is an extreme and 

 very complex example of this sort of differentiation and 



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