INTRODUCTION 



or principles that synthesize and correlate 

 the material at hand. Thus the "principles" 

 we shall attempt to formulate and interre- 

 late are simply those generalizations in- 

 ductively derived from the data of ecol- 

 ogy. We regard the so-called "laws of 

 nature" as empirical, derived from the facts, 

 and not the facts from the laws. In this 

 view, a principle is a means of description 

 of nature in succinct and compressed form. 

 This is true in the relatively well-organized 

 physical sciences, in which the principles 

 frequently can be reduced by mathemati- 

 cal statement to the extreme of simplifica- 

 tion. In the vastly more complex biological 

 sciences, mathematical formulation of gen- 

 eralizations is more diflBcult, and possible 

 only in limited segments of the complex. 

 The process of inductive generalization is 

 useful at every stage. The principles de- 

 rived from the compression of a mass of 

 data into a science form the main basis for 

 deductive thinking and for hypotheses 

 which ask new questions and make possible 

 new advances, on the one hand by opening 

 up new fields of inquiry and on the other 

 hand by progressive correction of the older 

 generalizations in the light of additional 

 data. 



We subscribe to the general principle of 

 scientific parsimony ("William of Occam's 

 razor"), which may be stated as follows: 

 "Neither more, nor more onerous, causes 

 are to be assumed than are necessary to ac- 

 count for the phenomena" (Pearson, 1937, 

 p. 340). For ecology in particular, the 

 number of entities should not be unneces- 

 sarily increased. Furthermore, Morgan's 

 canon (1894) concerning animal behavior 

 is essentially a quantitative development of 

 "Occam's razor" and an application of the 

 law of parsimony: "In no case may we in- 

 terpret an action as the outcome of the 

 exercise of a higher psychical faculty, if it 

 can be interpreted as the outcome of one 

 which stands lower in the psychological 

 scale." 



There is an understandable tendency in 

 any synthesizing discussion to review chiefly 

 the progress made in recent years or dec- 

 ades. This is sound practice in many ways, 

 but one result is that work, often excellent 

 work, of previous decades or even centu- 

 ries may be neglected. A false idea of 

 rapidity of progress is thereby encouraged, 

 and the concept of the relatively complete 

 modernity of subject matter tends to be 



built up in the thinking of younger readers, 

 although the minds of authors and editors 

 may have been entirely free from such a 

 misconception. We have accordingly made 

 a serious eflfort throughout this book to sup- 

 ply historical perspective and regard the 

 history of ecology and of its antecedent 

 sciences as an integral and significant part 

 of our treatment. 



Ecological history, like that of zoology in 

 general, can be summed up briefly as fol- 

 lows: In the Greek period— either because 

 such was the case, or because Aristotle did 

 not cite sources— it was the apparent rule 

 to study nature directly and to think over 

 the implications of observations made at 

 first hand. During the long scholastic period 

 in the Middle Ages, the influence of which 

 unhappily lingers on here and there, the 

 fashion changed to a study of books, or at 

 least a part of those available. The spirit of 

 the scientific awakening was at length sum- 

 marized by the dictum of Louis Agassiz: 

 "Study nature, not books."* Too often this 

 became perverted, by practice rather than 

 by precept, to the study of preserved speci- 

 mens, and some books. A gradual change 

 occurred until in the early decades of the 

 present century the tacit advice became: 

 Study living and preserved organisms in 

 the laboratory together with the pertinent 

 books. 



One constant effort of the modern ecolog- 

 ical movement has been to take the study 

 of nature again out under the sky. This 

 could not entirely succeed, in part because 

 of the difficulties in doing accurate analyti- 

 cal work in the field. A partial compromise 

 is attained by our turning to the greenhouse 

 and breeding cage, where experimentally- 

 minded ecologists have been met by 

 workers moving out of orthodox labora- 

 tories into these substitutes for field condi- 

 tions. Some ecoloeists have remained stub- 

 bomlv in the field, where they are being 

 ioined by a trickle of the more orthodox 

 indoor students. Laboratory and field ecol- 

 ogy are interdependent, and both are 

 essential. At the same time, the check of 

 knowledge gained directly against printed 

 accoimts, both as to empirical content and 



• An amusing and even paradoxical com- 

 mentary on this famous aphorism may he 

 derived from the fact that Agassiz prepared the 

 first comprehensive bibliography of zoology— 

 the four volume Bihliosraphia Zooloziae, pub- 

 lished by the Ray Society (1848-1854). 



