vi ANIMAL COMMUNITIES 



the particular species and localities covered than upon work done from 

 different points of view in remote localities. This bulletin is not intended 

 as a textbook. Several years of work would be necessary to give it the 

 completeness and form which a textbook should have, and the physiology 

 which should be included in such a textbook is almost entirely omitted. 



The organization here presented has in the main grown out of three 

 lines of thought: (a) the physiology of organisms as opposed to the 

 physiology of organs (51) 1 ; (b) the phenomena of behavior and physi- 

 ology, as illustrated by the studies of Loeb (72), much of the data of 

 which can be related to natural environments; and (c) the organized 

 comparable data of plant ecology, as set forth by Cowles (58) and 

 Warming (12). The results of these five years of labor will not be 

 pleasing to many zoologists because the principles of evolution, heredity, 

 etc., have not been correlated. Their omission, however, has not been 

 due to any prejudice against their introduction, but rather to the fact 

 that they can only occasionally be related to this line of organization. 

 It was thought also that the complexity of the problems and concepts 

 here treated made separation a necessity to clearness. 



The number of problems thrown open by the investigation is infinite. 

 Naturalistic observation and survey work could be carried much farther 

 along the lines here blocked out. The chief lesson which the author has 

 drawn from his labors is that experimental study, conducted with due 

 reference to the relations of the animals to natural environments, with 

 conditions carefully controlled, and a single factor varied at a time, is 

 one of the stepping-stones to future progress. We are confronted with 

 centuries of animal and human geography, with only inference or specu- 

 lation as to controlling factors for a background, and the experimental 

 study of factors in the case of man and other land animals only at its 

 beginnings. Though man is a land inhabitant, all the best work along 

 these and many other lines has been done upon aquatic animals. The 

 writer's course in the future will probably be determined by the needs 

 of the science, and will be turned from the purely naturalistic method 

 of study to a method made up of naturalistic observations and con- 

 trolled experiments. 



In undertaking a new line of work, one must have first, inspiration, 

 next, method and motive, and finally, in the case of ecological work, the 

 assistance of a large number of persons in various departments of 

 knowledge. For such assistance I wish to express my indebtedness to 



1 Numbers in parentheses, scattered through this work, refer to references in the 

 Bibliography at the end (pp. 325-36). 



