PHYSIOLOGY AND ECOLOGY 33 



distinguished from the more special physiology of organs (13, 51). With 

 these limitations upon the term physiology, what may be termed 

 physiological life histories (52) covers much of the field. Under this 

 head fall matters of rate of metabolism, latency of eggs, time and condi- 

 tion of reproduction, necessary conditions for existence, and especially 

 behavior in relation to the conditions of existence. Reactions of the 

 animal maintain it in its normal environment; reactions are dependent 

 upon rate of metabolism (53 and citations), which may be modified by 

 external conditions. Behavior reactions throughout the life cycle are a 

 good index of a physiological life history. 



If we knew the physiological life histories of a majority of animals, 

 most other ecological problems would be easy of solution. The chief 

 difficulty in ecological work is our lack of knowledge of physiological life 

 histories. With elaborate facilities these may be worked out in a 

 laboratory. Ecology, however, considers physiological life histories 

 primarily in nature, and for this reason the central problem of ecology 

 is the mores (13) problem. This may be defined as the problem of 

 physiological life histories in relation to natural environments together 

 with that of the relations of organisms in communities. The latter is 

 not a part of physiological life histories, the mores conception being the 

 broader. An ecological classification is a classification upon a physio- 

 logical basis, but since structure and physiology are inseparable, we 

 must not forget the relations of structure to ecology and to ecological 

 classification. 1 



V. Communities and Biota 



1. BASIS 

 Animals select their habitats probably by trial and error. The simple 

 fact of selection is, we believe, familiar to all naturalists. A given 



of natural history. There has never been any attempt to organize natural history 

 and physiological data into a science under the head of ethology, biology, or bio- 

 nomics, and the use of these terms will not seem justified until the materials to which 

 they have been applied are organized into a science. 



1 Mores (Latin singular mos), "behavior," "habits," "customs"; admissible here 

 because behavior is a good index of physiological conditions and constitutes the 

 dominant phenomenon of a physiological life history and of community relations. 

 We have used this term just as form and forms are used in biology, in one sense to 

 apply to the general ecological attributes of motile organisms; in another sense to 

 animals or groups of animals possessing particular ecological attributes. When applied 

 in this latter sense to single animals or a single group of animals the plural is used in 

 a singular construction. This seems preferable to using the singular form mos which 

 has a different meaning and introduces a second word. The organism is viewed as a 

 complex of activities and processes and mores is therefore a plural conception. 



