THE GENERAL BACKGROUND 9 



composing a "web of life," they are frequently called "biocoenoses." 

 Food and shelter relationships, climatic and edaphic factors, are im- 

 portant determining conditions for a given biocoenosis. 



With the growing complexity of ecological terminology and the 

 growing precision with which different terms are applied to various 

 recognizable groupings of animals, a need has developed for some 

 term which could be used in a general sense to cover any one of the 

 named units from the largest to the smallest. The word ''communi- 

 ty" has been reserved for this general purpose, and one may speak 

 with equal propriety of the animal communities of the Amazon 

 rain-forest or of a decaying tree within that forest. 



In the border-hne field where general sociology meets and over- 

 laps general physiology and ecology, the field which is being con- 

 sidered in the present discussion, it seems desirable to have a term 

 which may be applied loosely, but not incorrectly, to any of the 

 recognized units lying below the groups accepted as definitely social, 

 just as the term "community" is applied by the animal ecologists 

 with equal propriety to strata, super-society, society, association, 

 and what not. It is in this general sense, for this level of social or 

 subsocial hfe, that I propose to use the term "aggregation." I am 

 not concerned with defining it closely in terms of the association or 

 society of Deegener or Alverdes. It may be used with equal pro- 

 priety in speaking of a group of frogs collected as a result of sexual 

 attraction during the breeding season ; or of a concentration of May 

 flies about a fight, where they have been collected by forced move- 

 ment as a result of their strongly positive phototropism. There is in 

 the term itself a strong suggestion that the groupings involved are 

 not closely integrated, which is in keeping with the facts in the field 

 to be covered. 



INSTINCTS 



In the course of this discussion we shall have reason to refer to 

 "instinct," a term deservedly in disrepute among careful thinkers be- 

 cause of the slipshod way in which it has been used. Early students 

 of human sociology and recent zoological commentators on socio- 

 logical phenomena have sadly overworked the word by referring any 

 unanalyzed social behavior to the working-out of a social instinct. 



