334 VICTOR E. SHELFORD. 



etc., is one of the commonest errors of recent writers 1 and has 

 been chiefly responsible for such prejudice as may possibly exist. 



The definition of ecology, like that of any growing science is 

 a thing to be modified as the science itself is modified, crystallized 

 and limited. At present, ecology is that branch of general physi- 

 ology which deals with the organism as a whole, with its general 

 life processes, as distinguished from the more special physiology 

 of organs (Semper, '81). With these limitations upon the term 

 physiology, what may be termed physiological life histories 

 (Ganong, '07) covers much of the field. Under this head fall 

 matters of rate of metabolism, latency of eggs, time and condition 

 of reproduction, necessary conditions for existence and especially 

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

 animal maintain it in its normal environment; reactions are de- 

 pendent upon rate of metabolism (Alice, '12, and citations) which 

 may be modified by external conditions. Behavior reactions 

 throughout the life-cycle are a good index of physiological life- 

 history characters. 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. On this account 

 the relative importance of the different aspects of investigation 

 given later in this paper is based upon present expediency. 



Physiological life histories may, with elaborate facilities, be 

 worked out in a laboratory. Ecology however considers physio- 

 logical life histories primarily in nature and for this reason as has 

 already been stated the central problem of ecology is the mores* 

 problem or the problem of physiological life histories in rela- 

 tion to natural environments, the dominant facts in which 



1 See Trans. Am. Micro. Soc., Vol. XXX., p. 217. 



2 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 in the sense proposed. 

 We have used the 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 the 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 is therefore a 

 plural conception. 



