30 ANIMAL ECOLOGY 



understand whether it is in a condition of stress, a 

 process of adjustment, or one of relative equilibrium 

 or balance. Under present conditions in what 

 direction does it tend to move ? At what rate ? 

 The non-ecological surveys have not put these ques- 

 tions or worked deliberately toward a goal which 

 will answer them. For any comprehensive study of 

 this character we need to have determined what may 

 be considered as a biotic base, optimum, or balance, 

 toward which relations under given conditions tend, 

 and at which an equilibrium will become established 

 (The Auk, 1908, Vol. XXV, p. 125). Such facts 

 underlie all of the problems involved in the interpre- 

 tation of climax biotic associations, and their applica- 

 tion by man. Cook (1909, Bull. 145, Bur. Plant 

 Industry, U. S. Dept. Agriculture, pp. 7, 8) has 

 expressed similar relations as follows: " Unless we 

 can form a definite idea of the original conditions 

 we cannot expect to judge of their influence on 

 primitive man, nor can we determine what effects 

 man has had upon the vegetation and other natural 

 conditions. We need what might be called a 

 bionomic base line, an idea of the conditions which 

 existed before man came upon the scene, the con- 

 ditions which would again supervene if the human 

 inhabitants were withdrawn." 



It is perhaps significant that the genetic or succes- 

 sional relations of habitats and associations, as con- 

 trasted with their descriptive classification, both in 

 plants and animals, have in the past been developed, 

 not by the ecological students who live and work among 



