CLASSIFICATION OF ANIMAL AGGREGATIONS 33 



ishment of the parasite comes from the li\ang substance of the host. 

 Many categories of even such restricted parasitism are recognized, 

 and may be found Hsted in reference works on the subject (Hegner, 

 Root, and Augustine, 1929). 



We have given here an outline of Deegener's classification of ani- 

 mal groupings in detail, but it is not our intention to fit the different 

 aggregations to be discussed later into their appropriate niches in 

 this classification. In fact, certain of its more detailed aspects will 

 not be referred to again. But it is upon the idea that there is an es- 

 sential unity within the phenomena to be discussed that the present 

 summarizing account has been prepared; this concept, although 

 foreshadowed by Espinas, was first fully expressed in Deegener's out- 

 line. We shall return to it in the concluding chapters. 



CLASSIFICATION OF ALVERDES 



When we turn to the analysis of social phenomena by Alverdes, we 

 find, as suggested in the introduction, that the relations composing 

 the first part of Deegener's outline are omitted as without social 

 significance, since in them Alverdes cannot recognize the expression 

 of a social instinct and since the entire discussion of these so-called 

 associations is limited to a definition and slightly more than two 

 pages of text. This omits consideration of much of the material to 

 be presented in the present discussion, and Hmits markedly the 

 field of general sociology. Even under these sharper limitations, the 

 criterion of social life suggested by Alverdes, that of the possession 

 of a social instinct, must necessarily be vague and easily capable of 

 misinterpretation. 



The material which Alverdes believes to form the subject matter 

 of general sociology is organized in the main about sexual relations, 

 in which he recognizes such categories as monogamy, polygyny, 

 father-families, mother-families, and other similar divisions which 

 were also found in Deegener's more inclusive outline. In addition, 

 he recognizes that animal societies may be closed or open. In the 

 former, new members are admitted only under special conditions, if 

 at all; insect states are such. Within a closed community there is 

 frequently an established hierarchy, as has been shown for birds 



