FIRST FOUR DECADES OF THE TWENTIETH CENTURY 



55 



was well stated by Raymond Pearl in a 

 1914 (pp. 47-48) address before the 

 American Statistical Association. He said: 



"Statistical science has brought to biology 

 three fundamentally important things which it 

 had previously lacked. These are: first, a 

 method of describing a group of individuals in 

 terms, not of its component individuals, but in 

 terms of its (the group's) own attributes and 

 qualities; second, the concept of 'probable 

 error,' which makes possible an estimate of 

 the probable accuracy of a series of obserx^a- 

 tions; and third, a method of measuring the 

 degree of association or correlation between the 

 variations in a series of characters or events. 

 . . . By turning to statistical science for aid the 

 biologist has greatly augmented his powers of 

 analysis in the domain of his own particular 

 problems. While this branch of science, which 

 has been called into being by this coalition, is 

 vet too young to have shown its full capabili- 

 ties, yet I think its achievements have been 

 sufficient in qualitv and amount to justify the 

 belief that its position is secure and its prom- 

 ise bright. Biometrv seems destined to be- 

 come a permanent and important branch, at 

 once of biological investigation and of statisti- 

 cal inquiry." 



These were prophetic and true words, 

 both for biology and for ecology. 



1921-1930 



During the decade 1921 to 1930 ecology 

 was expanding and maturing; expanding in 

 the sense that more ecological studies were 

 published; maturing in the sense that the 

 Geld was attaining greater focus. Whereas 

 the second decade of the twentieth century 

 was considerably like the first, the third dec- 

 ade was somewhat different, even though 

 much of the specific research was similar. 

 Ecologists were still conducting research on, 

 say, response physiology, or food relations 

 or succession, but now their work seemed to 

 have more of a common denominator that 

 took form as a "self-conscious" science. 

 Thus, in studies on animal responses or 

 succession there was greater interest in in- 

 terpreting these phenomena in broad eco- 

 logical terms. We do not imply that ecology 

 became a closely unified science during the 

 third decade. It is not that today. We sug- 

 gest only that it was collecting certain 

 varying ends, rearranging its emphases and 

 starting thereby on a newlv oriented course. 

 It is our task to examine further these 

 trends. 



Certain books published between 1921 



and 1930 reflect the temper of the times. 

 At the outset, two textbooks appeared de- 

 signed for the use of ecologists in university 

 classes: Animal Ecology (1926) by A. S. 

 Pearse, and Animal Ecology (1927) by 

 Charles Elton. We shall return to these 

 directly. There were other books basically 

 ecological in character. Borradaile's The 

 Animal and Its Environment (1923) gave 

 "an elementary treatment of animal ecology 

 including general descriptive matter from 

 natural history, and relatively little quan- 

 titative analysis of the environment" 

 (Chapman, 1931, p. 2). In 1922 the third 

 edition of Folsom's Entomology was pub- 

 Hshed. It is significant to note that the 

 author added to this edition the subtitle 

 "with special reference to its ecological as- 

 pects" and included a new chapter on 

 "Insect Ecology" prepared under the guid- 

 ance of V. E. Shelf ord. While this book 

 made no great impact on ecological science, 

 its revised publication suggests that the 

 ecological developments of the first and 

 second decades had been sufficient to cause 

 an entomologist to present his subject 

 basically from that point of view. 



In 1929 Shelford published Laboratory 

 and Field Ecology, which was largely a 

 "methods" book. Although it was to serve 

 ecologists, it did not have anything like the 

 influence on ecological histor)'^ enjoved by 

 the author's earlier Animal Communities in 

 Temperate America. Elton (1930) brougrht 

 forth a small book entitled Animal Ecology 

 and Evohition. which centered around three 

 chief topics: "The Regulation of Numbers," 

 "The Significance of Migration." and "The 

 Real Life of Animals." In 1927 Social Life 

 in the Animal World by Alverdes appeared. 



From the dignified viewpoint of scholar- 

 ship, probably the really significant book of 

 the decade was R. Hesse's Tieraeos^raphie 

 auf oekologischer Grundlase, which ap- 

 peared in 1924. This treatise recognized 

 that there was an approach to zoogeog;raphv 

 other than the classical, faiinal one. Hesse's 

 conception of the subject is well stated in 

 this translated excerpt from his preface: 



"Ecological animal geography is a young 

 science ... In this new field the fundamen- 

 tal questions are yet to be formulated in order 

 that a rich phase of biology may be opened 

 for further work. I hope this book may be 

 thought of as such an attempt; it deals largely 

 with problems which are taken up separately 

 and arranged in order, and but relatively little 



