58 



THE HISTORY OF ECOLOGY 



(1881, "Animal Life as Affected by the 

 Natural Conditions of Existence" [italics 

 ours J) (see p. 22), that Shelf ord had used 

 ia 1918 to describe such environmental fac- 

 tors which, he said, "are of importance 

 only in so far as they affect the Hfe and 

 death processes of organisms." The phys- 

 ico-chemical conditions of existence most 

 studied through this decade were water, 

 temperature, humidity, hydrogen ion con- 

 centration,' oxygen and carbon dioxide 

 tensions, saUnity, specific gravity, molar 

 agents such as wind, current, and waves, 

 tide, substratum, and altitude. If space per- 

 mitted, and if it were essential for our his- 

 torical survey, we could discuss papers that 

 dealt with any or all of these factors. This 

 we cannot do. The major point is that ecol- 

 ogists had recognized the abiotic environ- 

 ment both as a total unit and in terms of 

 its components and were analyzing it from 

 those vantage points. The organism's re- 

 sponse, its growth and development, and 

 its toleration of these conditions of exist- 

 ence remained the essential subjects of 

 analysis. 



The organization centering around the 

 biotic environment is more difficult to sum- 

 marize. In part, this means merely that 

 biotic relations tend to be more complex 

 than do the abiotic. In part, it means that 

 ecologists themselves had not crystalUzed 



** The biologists of the twenties were amus- 

 ingly "pH-minded." Here was a technique, 

 both physiological and ecological, easily ap- 

 plied, far-reaching in its implications, and so 

 respectable! The point is well made in anec- 

 dotal (and true) fashion. 



A well-known ecologist was setting out from 

 the wharf at the Marine Biological Laboratory 

 ( Massachusetts ) to collect data about the local 

 distribution of certain marine organisms, partic- 

 ularly those factors correlated with distribution. 

 In true ecologist-fashion his dory was loaded 

 with apparatus and impedimenta of all sorts. 

 On the rear seat there lay a pH kit. At the 

 wharf to see him off was a friend, one 

 of America's most distinguished zoological 

 scholars, who asked, 



"Where are you going?" 



He got his answer. 



"What is your problem?" 



Again, an answer. 



"Why do you take so much equipment?" 



The ecologist tried to justify his boat load. 



"Well," said the savant, pointing to the pH 

 kit, "that is all you'll need. Leave the rest at 

 home!" 



Thus pH in the twenties! 



this phase of their science at that time. It 

 is possible, however, to recognize certain 

 general categories into wlrich the biotic 

 aspects fall. These are: 



1. The animal community: 



( a ) Distribution 



(b) Food and feeding relationships 

 within the community 



(c) Successional and other develop- 

 mental aspects 



2. The problem of aggregation 



3. rhe population: 



(a) The natural population 



(b) The laboratory population 



4. Parasitic-symbiotic-social relationships (in 

 a specific sense and distinct from the 

 animal community) 



5. Miscellaneous: 



(a) Rhythmic phenomena 



(b) Dispersal phenomena 



(c) Human ecology 



(d) Aspects of economic zoology 



We cannot take time to document this 

 outline in any detail, but it does seem wise 

 to extend our remarks by discussing briefly 

 the community, the aggregation, and the 

 population. These aspects of ecology were 

 developing rapidly between 1921 and 1930, 

 and are much studied by ecologists today. 



Since Elton's treatment of communities 

 seems without question the best of the dec- 

 ade, we can do no better than examine the 

 state of this phase of ecology as seen 

 through his eyes. As mentioned earher, 

 Elton viewed ecology as essentially the 

 study of populations and communities. 



Judging from Elton and the published 

 papers of the decade 1921 to 1930, ecol- 

 ogists were interested in the animal com- 

 munity from these aspects: its distribution 

 in both a geographical and a local sense; 

 its structure and organization; and its tem- 

 poral development and change. There was 

 not much emphasis on the community as a 

 "social organism," although Elton, among 

 others, recognized the point, nor on the 

 problem of biotic equiUbrium. These phases 

 were to come later. 



Under the influence of Hesse, Shelford, 

 and others, ecologists were examining com- 

 munities on a geographical scale and were 

 working on the pattern of their distribu- 

 tion. This did not stop with mere descrip- 

 tion, for certain of the studies insisted that 

 there were basic analogies between the 

 communities of one area and those of an- 

 other. These analogies seem to have con- 

 vinced students that the community was a 



