FmST FOUR DECADES OF THE TWENTIETH CENTURY 



51 



perature or humidity was the variable 

 studied. Headlee's 1917 paper is a represen- 

 tative example. In this he analyzed the 

 eflFect of humidity on duration of metamor- 

 phosis in the bean weevil, Bruchus ohtectus. 

 For a paper published during the decade, 

 but dealing with temperature rather than 

 with humidity, the reader is referred to 

 Krafka (1920). 



Earlier, we called attention to the pubh- 

 cation in 1918 of the second edition of 

 Bayliss' Physiologi/. This magnificient vol- 

 ume immediately became a source book for 

 physiologically minded ecologists (as it did 

 for many other biologists) and did much 

 for the field. It was useful especially in the 

 area of developmental physiology. 



Not many publications were concerned 

 directly with toleration physiology between 

 1911 and 1920, although this phase was 

 touched on incidentally in numerous places. 

 A good example of this approach per se is 

 the paper of Shelford and Allee (1913), 

 "The Reactions of Fishes to Gradients of 

 Dissolved Atmospheric Gases." For exam- 

 ple, they studied the ability of various spe- 

 cies of fish to tolerate low oxygen tensions. 

 One of their suggestive findings was this: 

 Species of fish die (in the presence of re- 

 duced oxygen supply) in the order of their 

 relation to this factor in nature. Thus, just 

 to make the point, Notropis, a swift-water 

 form, starts to die after 376 minutes' expo- 

 sure, while Ameiurus, typically a sluggish- 

 water form, does not start to die until after 

 1080 minutes. 



A number of excellent investigations on 

 hydrobiology were published during this 

 decade. There was perhaps a growing diver- 

 gence between oceanography and limnol- 

 ogy, but the essential viewpoints of these 

 two fields retained much in common. The 

 treatise, alreadv mentioned, by Murrav and 

 Hjort, The Depths of the Ocean, appeared 

 in 1912 and helped to establish modern 

 oceanography on a firmer foundation. A 

 representative research report was that of 

 Petersen and Jensen (1911), who published 

 a comprehensive monograph on the fauna 

 of the ocean floor both from the quantita- 

 tive and nutritional aspects. This paper 

 discussed the techniques of bottom study 

 and also presented manv significant biolog- 

 ical data. Adams in 1913 considered it "a 

 verv important paper." 



In addition to recognizing the importance 

 of Petersen and Jensen's paper, a word 



should be said of Petersen himself. It is not 

 always recognized that this man is among 

 the great in the history of ecology and 

 hydrobiology. We should fail in our survey 

 if we overlooked the point. Professor E. S. 

 Russell, himself a distinguished hydrobiol- 

 ogist, in his The Overfishing Problem 

 (1942, pp. 68-69) pays tribute to Petersen 

 in these words: 



"In introducing a biological and ecological 

 note into this discussion ... I shall follow the 

 lead of a remarkable man, the late C. G. Joh. 

 Petersen, a pioneer in fishery research and 

 marine ecology, whose work is unfortunately 

 not widely known outside fishery circles. I had 

 the privilege of his friendship, and the oppor- 

 tunity of discussing with him fishery questions 

 and problems of general biology— and I take 

 this occasion to pay a tribute to his memory. 



"Petersen was for many years Director of 

 the Danish Biological Station, a State institu- 

 tion devoted to the investigation of fishery 

 problems, and it was his great merit that he 

 regarded these as being essentially problems of 

 ecology. He realised more vividly than anyone 

 else that fish must be studied, not in isolation 

 from their environment, or purely from a sta- 

 tistical point of view, but in close relation to 

 all the factors, including the effect of fishing, 

 that influence their abundance, their rate of 

 gro\\'th, and their reproduction." 



Fresh-water investigations were also con- 

 tributing to the growth of ecology during 

 the decade. Birge and Juday were in the 

 midst of their long personal and scholarly 

 association. A representative illustration of 

 their then current work was the still-quoted 

 1911 paper, "The Dissolved Gases of the 

 Water and Their Biological Significance." 



In 1918 Muttkowski published a sound 

 report covering work conducted at Lake 

 Mendota (Wisconsin). This paper was a 

 thorough treatment, with considerable tabu- 

 lar documentation, of the follo\\dng points: 



(1) qualitative survey of the macrofauna; 



(2) quantitative survey of the commoner 

 macrofauna; (3) ecological distribution of 

 the fauna: (4) breeding habits; and (5) 

 food relations, especially insects as food for 

 the fish population. In 1918 there also ap- 

 peared Fresh-water Biology, edited by 

 Ward and WHiipple. We have already sug- 

 gested that this source book had a firm im- 

 pact on aquatic ecology. 



Forbes and Richardson (1919) published 

 a study of the Illinois River that not only 

 contained much of ecological importance, 

 but also utilized physiography as an ap- 



