PREFACE. Vii 



school biology of the future will be primarily concerned 

 about our life interests; but he believes that the great 

 evolutionary conception, which can only be had by some 

 study of the ecology, morphology, and physiology of 

 the animal phyla, is quite as really and profoundly a 

 "human interest" as is stock-breeding, agriculture, or 

 malaria. This conception has changed the whole aspect 

 of human thinking in the last half-century. No course in 

 Zoology which is more than commercial can afford to 

 neglect it. 



The present book retains the evolutionary phase 

 as the skeleton of the course. This has largely deter- 

 mined the arrangement of the chapters and of the matter 

 within the chapters. At every legitimate point, however, 

 the author has introduced and placed upon this skeleton 

 material looking toward the economic and humanistic 

 interests of the pupil. Much of this matter is in the form 

 of topics and supplementary exercises for investigation. 

 This form is used because these subjects are intrinsically 

 interesting; they can the more readily be utilized to 

 cause the student to do original work in field or library. 

 They are, therefore, a tremendous strengthening, peda- 

 gogically, to any course. The author believes this is 

 much better for the course than to have written out this 

 material as a part of the text. 



For any teacher who wishes, and is prepared, 

 FOR AN , ^ . . t%L 



to make this economic aspect of the work 



ECONOMIC ^, f 1 ^1 1 



the prime part of his course, these supple- 

 COURSE/ . , . , 



mentary topics and exercises in each chapter 



may be assigned first. Afterward whatever is desired 

 of the text, in order to organize this in a satisfactory way, 

 may be assigned. In this event the teacher should secure 

 all possible economic biological literature from the U. S. 



