INTRODUCTION TO THE AMERICAN REVISED EDITION 



The appearance of Professor Richard Hesse's Tiergeographie auf 

 oekologischer Grundlage in 1924 marked the beginning of a new phase 

 in the development both of ecology and of animal geography. In the 

 latter field it made the first serious attempt to apply ecological 

 methods, principles, and facts to the study of animal distribution on 

 a world-wide scale. Some of the geographic implications of modern 

 ecology had been set forth in shorter essays, notably by Adams, in 

 phases of his report on Isle Roy ale as a Biotic Environment (1909, 

 Mich. Geol. Survey) ; by Shelford, Physiological Animal Geography 

 (Jour. Morph. 1911) ; and by Professor Hesse himself in his contribu- 

 tion to Hettner's Geographische Zeitschrift in 1913. 



The failure to apply the results of studies in animal ecology to 

 geographic distribution is not surprising, for aside from Shelford's 

 pioneering work, Animal Communities in Temperate America (1913), 

 there had been no attempt to collect the mass of ecological facts 

 which were rapidly accumulating since the brilliant summary of early 

 work by Semper in his Animal Life as Affected by the Natural Con- 

 ditions of Existence, published in 1881. 



The need of such a summary was becoming increasingly pressing 

 with the rapid appearance of observational and research reports. The 

 possible application of the results of these studies to animal geography 

 had been suggested by the clarifying effect of Schimper's Pflanzen- 

 geographie auf physiologischer Grundlage upon both plant ecology 

 and plant geography. 



The general hesitation before attempting the task of summarizing 

 the ecological progress in animal studies rested upon two obstacles. 

 In the first place, there was and is the scattered and hidden state of 

 pertinent literature, and in the second place, the rapid growth of our 

 knowledge, particularly in the first decades of the present century, 

 which as yet shows no sign of slackening. Interest in ecological rela- 

 tionships has been so widespread that the publication of results cannot 

 even now be compressed into journals devoted primarily to such 

 matters, and in the period when Hesse was at work on his manuscript, 

 before the founding of modern ecological journals, there was still 

 more confusion. Not only is the material scattered, but also important 

 observations are so hidden in reports dealing with such varied subjects 



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