34 ENVIRONMENTAL RELATIONS 



environmental complex is selected by a number of species. All of the 

 animals of a given habitat constitute what is known as an animal 

 community; all the life (plant and animal) is a biota. It follows that 

 there is often a certain physiological or ecological similarity in the species 

 which select the same or similar habitats. When not ecologically 

 similar, animals living in the same or similar habitats are usually 

 ecologically equivalent, i.e., they meet the same conditions in different ways. 

 For example, in a swift stream, the small fishes known as darters maintain 

 themselves against the swift current by their strong swimming powers 

 and by orienting against the current (positive rheotaxis). The snails 

 (Goniobasis) are able to maintain themselves because of the strength of 

 their foot and positive rheotaxis. The darters and snails are ecologically 

 equivalent with respect to current. 



There is a marked agreement of all the animals of this community in 

 their reactions to the factors encountered in the stream. This agreement 

 is due (a) to the selection of the habitat through innate (instinctive) 

 behavior (40, 49, 54, 55), and (b) to the adjustment of behavior to the 

 conditions through the effects of physical factors and through formation of 

 habits and associations (44, 53). 



Animals of the same species show behavior differences in different 

 habitats (44, chap, xxi; 55, p. 584; 53). Bohn found that the sea 

 anemones living near the surface of the sea, where the wave and tide 

 action are strongest, showed more marked rhythms of behavior in relation 

 to tide than those living lower down where the action of the tide and 

 waves is less marked (53a, p. 156; 53 b, p. 155). These rhythms dis- 

 appeared slowly when the animals were removed from the tide to the 

 aquarium. Many such cases are probably to be found in the natural- 

 history literature. For example, the chipmunk differs in behavior under 

 different conditions (21, p. 523). Abbot (53c, p. 104) makes a similar 

 statement about fish. It is apparent then that one species may have 

 several mores. Different species may sometimes have identical mores; 

 these cases are usually separated geographically (55, p. 604). In 

 addition to these relations, the relation of ecology to species is largely a 

 matter of language, names being necessary as a means of referring to 

 animals. 



The physiological and behavior relations of animals in the same 

 community are of much importance and are included under (a) inter- 

 physiology or psychology and (b) inter-mores physiology or psychology, 

 (a) Inter-physiology. — Tarde (55, citations) is the author of the idea of 

 inter-psychology — the psychology of the relations of individuals of the 



