The volume collects essays that frame an empirical program for studying human behavior under urban conditions, treating the city as a cultural, ecological, and economic habitat rather than merely a set of buildings. Contributors outline an ecological approach to population distribution and urban growth, propose methods for studying neighborhood organization and mobility, and examine institutions and mentalities shaped by city life, including the press, juvenile delinquency, romantic and magical attitudes, and itinerant lifestyles. A classified bibliography accompanies the essays to guide further research.