SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS 247 



added relation that requires explanation, an regards its 

 exact biological value and its historic develoj^mont a.swcll. 

 In undertaking this diflicult task, it seems best to 

 begin with the very simplest organisms that biology 

 knows, working upwards through the scale to man. Hy 

 this course the most basic elements ot organization 

 can be discovered without having to look for thom 

 among the intricate details of our own vital situation, 

 where secondary and adventitious elements stand out 

 in undue prominence, and where the impersonal vi(nv 

 is well-nigh impossible. Step by step we will then work 

 up the scale of social morphology, approaching in the 

 natural evolutionary order that part of the subject 

 which interests us most deeply. 



Just as the construction of an edifice must begin with 

 the fashioning of the individual brick and bolt and girder, 

 so the evolution of a biological association begins with 

 the unitary organisms consisting of single cells, like 

 Amoeba. We have had occasion to discuss this animal 

 many times in our previous studies of one or another 

 aspect of evolution, and once again we must return to 

 it in order to reestablish certain points that are of 

 fundamental importance for our present purposes. 

 Within the limits of its simple body, Ainoeba performs 

 the several tasks which nature demands a living thing 

 shall do; it feeds and respires and moves, continually 

 utihzing matter and energy obtained from the environ- 

 ment for the reconstruction of its substance and replen- 

 ishment of its vital powers ; it coordinates the activities 

 of its simple body, and by its reflex responses to en- 



