Vlll 



PREFACE 



the book. This emphasis has not necessarily 

 aflFected the selection of supporting ex- 

 amples, since neither the older, more widely 

 known illustrations nor the most recently 

 discovered ones have been regularly used. 



We discuss ecological principles dealing 

 with the nonliving physical environment 

 more or less as a unit, whether they are 

 concerned primarily with the individual 

 (autecology) or with the population or the 

 community (synecology). The consideration 

 of the biotic environment of the individual 

 organism is less unified and perhaps less 

 comprehensive. It is hard to avoid some 

 duplication in dealing with the environmen- 

 tal relations of these different biological 

 units, and the inherent difficulties have not 

 been resolved formally and logically. In dis- 

 cussing principles dealing with the organism 

 in its nonliving physical environment, we 

 have anticipated many somewhat similar in- 

 terrelations with the higher ecological cate- 

 gories. In contrast, much of the discussion 

 of the biotic environment is given in direct 

 connection with populations, communities, 

 and evolution, rather than in a single part 

 of the book. 



In our treatment of the ecological prin- 

 ciples that emerge with the population as 

 the unit of study, our attention centers first 

 on the population in both laboratorv and 

 field and, later, on aggregations and on 

 certain aspects of societies. The analysis of 

 functional contemporary principles leads 

 naturally to the examination of interspecies 

 groups. Here our primary concern is with 

 the underlying structure, organization, suc- 

 cessional development, and distribution of 

 the ecological community. In this section 

 our emphasis is on terminology only in 

 those instances in which the term itself is 

 a well-authenticated index of the principle. 

 The multiplication of terms represents a 

 juvem'le stage of the science as a whole, 

 and it is hoped that a critical definition and 

 sifting of the concepts that support the 

 terminology may lead to a reduction of 

 their complexity and to an advance toward 

 maturitv. 



Finally, in examining the problems of 

 evolution we attempt to bring out those 

 ecological aspects that are particularly sig- 

 nificant, such as isolation, selection, adapta- 

 tion, distribution, regressive evolution, and 

 others insofar as they contribute to ecologi- 

 cal principles or as the ecological approach 

 aids in their solution. 



The book was planned jointly. Each 

 author undertook primary responsibility for 

 preparing the first draft of sections or chap- 

 ters for the handling of which he showed 

 particular competence so far as our group 

 membership was concerned. Early working 

 outlines and successive copies of each chap- 

 ter or section were distributed to the other 

 authors and received criticism concerning 

 both manner and matter, particularly with 

 regard to possible omissions. Eventually all 

 parts of the manuscript were read aloud to 

 the other authors, and there was much dis- 

 cussion of questioned points. We feel that 

 in the main we have reached a truly re- 

 markable degree of agreement both on the 

 major and minor principles of ecology, 

 though some generalizations, emphases, and 

 conclusions are not shared with equal en- 

 thusiasm by every author. Fortunately, 

 these are usually matters of relatively minor 

 significance. 



Many parts of the manuscript were read 

 critically by persons outside our circle, and 

 the revised version was again distributed to 

 the other authors. Finally there was a 

 period of collation between pairs of authors. 

 Near the end of the writing each author 

 was instructed to use his own judgment in 

 the final polishing of the chapters for which 

 he prepared the first draft.** Chapters from 

 various sections were also read to the 



* We had originally hoped that many traces 

 of personal origin of chapters would disappear 

 during this extended and detailed critical treat- 

 ment and that final responsibility would rest 

 entirely with the group. This hope has been 

 realized in large part, but, as was to be ex- 

 pected, each author feels decidedly more re- 

 sponsibility for the selection, organization, 

 presentation and interpretation of the material 

 he has himself written than he does for other 

 chapters, or even for the book as a whole. 

 Particular responsibility for the different chap- 

 ters was distributed as follows: 



Preface and Introduction ( Chapter 1 ) : 

 K.P.S. (based on drafts by W.C.A. and T.P.). 



Chapters 2, 4 to 16, inclusive, and 23: 

 W.C.A. 



Chapters 3 and 18 to 22, inclusive: T.P. 



Chapter 17: W.C.A. and K.P.S. 



Chapters 24 and 31 to 35, inclusive: A.E.E. 



Chapters 25 to 29, inclusive: O.P. 



Chapter 30: K.P.S. and O.P. 



General editing of the manuscript: K.P.S. 



The four junior authors here acknowledge 

 the leadership of Dr. Warder Clyde Allee and 

 their indebtedness to him throughout the 

 preparation of the present work. 



