avior._ Biological and
Psychological Foundations. New York, 1913. [Bibliography.]

(4) Massart, J., and Vandervelde, E. _Parasitism, Organic and Social._
2d ed. Translated by W. Macdonald. Revised by J. Arthur Thomson. London,
1907.

(5) Warming, Eug. _Oecology of Plants._ An introduction to the study of
plant communities. Oxford, 1909. [Bibliography.]

(6) Adams, Charles C. _Guide to the Study of Animal Ecology._ New York,
1913. [Bibliography.]

(7) Waxweiler, E. "Esquisse d'une sociologie," _Travaux de l'Institut de
Sociologie (Solvay), Notes et memoires_, Fasc. 2. Bruxelles, 1906.

(8) Reinheimer, H. _Symbiosis._ A socio-physiological study of
evolution. London, 1920.

III. THE CLASSIFICATION OF SOCIAL GROUPS

A. _Types of Social Group_

1. Non-territorial Groups:

(1) Le Bon, Gustave. _The Crowd._ A study of the popular mind. London,
1897.

(2) Sighele, S. _Psychologie des sectes._ Paris, 1898.

(3) Tarde, G. _L'opinion et la foule._ Paris, 1901.

(4) Fahlbeck, Pontus. _Klasserna och Samhallet._ Stockholm, 1920. (Book
review in _American Journal of Sociology_, XXVI [1920-21], 633-34.)

(5) Nesfield, John C. _Brief View of the Caste System of the
North-western Provinces and Oudh_. Allahabad, 1885.

2. Territorial Groups:

(1) Simmel, Georg. "Die Grossstaedte und das Geistesleben," _Die
Grossstadt_, Vortraege und Aufsaetze zur Staedteausstellung, von K. Buecher,
F. Ratzel, G. v. Mayr, H. Waentig, G. Simmel, Th. Peterman, und D.
Schaefer. Dresden, 1903.

(2) Galpin, C. J. _The Social Anatomy of an Agricultural Community._
Madison, Wis., 1915. (Agricultural experiment station of the University
of Wisconsin. Research Bulletin 34.) [See also _Rural Life_, New York,
1918.]

(3) Aronovici, Carol. _The Social Survey._ Philadelphia, 1916.

(4) McKenzie, R. D. _The Neighborhood._ A study of local life in
Columbus, Ohio. Chicago, 1921 [in press].

(5) Park, Robert E. "The City. Suggestions for the Investigation of
Human Behavior in the City Environment," _American Journal of
Sociology_, XX (1914-15), 577-612.

(6) Sims, Newell L. _The Rural Community, Ancient and Modern._ New York,
1920.

B. _Studies of Individual Communities:_

(1) Maine, Sir Henry. _Village-Communities in the East and West._
London, 1871.

(2) Baden-Powell, H. _The Indian Village Community._ Examined with
reference to the physical, ethnographic, and historical conditions of
the provinces. London, 1896.

(3) Seebohm, F