PREFACE 



DURING the past ten years the writer has been try- 

 ing to find some consistent and satisfactory working 

 plan for handling the almost bewildering number of 

 facts, of ecological significance, which have been ac- 

 cumulating in the literature of zoology, biology, and 

 the allied sciences. This book is the outgrowth of 

 the effort as it has developed in the study and teach- 

 ing of animal ecology. I have not attempted to 

 make this an exhaustive treatment of the subject, 

 but rather to indicate briefly some of its general 

 bearings and a method of approach. I have tried 

 to keep in mind the needs of the beginner in ecology. 



An ecological point of view is described more fully 

 than the other subjects discussed, so that the stu- 

 dent may see the need of familiarity with those tests 

 or criteria by means of which he may be able to 

 determine for himself ecological relations and the 

 validity of ecological studies. The other phases are 

 treated less fully in the discussions and with more 

 detail bibliographically so that this may be a useful 

 source book. The geographical (in the ordinary 

 sense of the word) aspect has been deliberately 

 omitted. The references should be looked upon 

 from the standpoint presented in the general por- 

 tions of this book, and if the facts and inferences 

 aid in the interpretation of the relations which exist 



