THE GENERAL BACKGROUND 5 



ford, 1929). In the present studies we shall find ourselves concerned 

 with animal communities which, from their concentrated nature, 

 necessarily make the biotic elements an important aspect in the en~ 

 vironment of any particular individual, while the physical elements 

 of the environment act mainly through their iniluence on the entire 

 aggregation or crowd. Such a situation must frequently obtain in 

 assemblages of sea anemones, of Mytilus, of ascidians, or of crabs. 

 In working at the aggregation level here considered, we find the 

 ratio of importance of the physical and the biotic environment in a 

 transition stage between that present in definitely social groups and 

 that occurring in the more typical animal community, or biocoenose 

 of the ecologist. 



We must emphasize the fact that all studies dealing with the 

 biotic elements of the environment are likely to be less definitely 

 quantitative than those dealing with the non-living environment. 

 This is no reason for their neglect, but it is a reason why we may not 

 expect their treatment to be precise and final. The present summary, 

 gained from pioneering in this relatively new field, must be regarded 

 as tentative in many respects. My own research program dealing 

 with various aspects of the subject is only well under way; the pres- 

 ent statements furnish a point of departure, rather than a gathering- 

 in of conclusions. With the accumulation of evidence now being 

 actively collected, the conclusions tentatively advanced here may 

 be further confirmed, or they may soon be modified or entirely aban- 

 doned. This must always be the case, even in the well-developed 

 fields of physics and chemistry; and does not prevent summaries of 

 knowledge to date having definite value, if they stimulate further 

 research or give point to researches already in progress. 



TERMINOLOGY 



The general terminology causes unexpected difficulty. One usual- 

 ly thinks that such words as "society," ''association," and "com- 

 munity" have a relatively stable meaning and that "biocoenosis," 

 for example, might be expected to be a quite exact term; but this is 

 unfortunately not the case. 



According to writers on human sociology (Park and Burgess, 



