PREFACE. 



This book offers a series of practical studies of biological 

 phenomena for the guidance of the general student. It is 

 not a formal text, and not at all a treatise, but only a guide 

 intended to assist the student in acquiring for himself some 

 real knowledge of living nature. It differs chiefly from 

 other books intended for the use of college classes in the 

 wider range of studies it offers, some important phases of 

 biology having hitherto been dismissed with mere didactic 

 instruction. Morphology has dominated often monopo- 

 lized college work in biology in the past; doubtless, be- 

 cause it was first reduced to pedagogic form, and made 

 available for laboratory instruction. A more equable 

 treatment is here attempted, in the hope of leading the 

 student to a practical acquaintance with elementary 

 phenomena in the whole broad field. 



The generation of biologists which began its studies with 

 Huxley and Martin's pioneer laboratory manual has wit- 

 nessed a marvelous expansion of biological knowledge. 

 Departments have sprung up, and teachers as well as prac- 

 titioners have specialized, and courses have multiplied 

 amazingly. Yet I am persuaded that the reasons given by 

 Huxley and Martin for offering a general course are as valid 

 today as they were in 1868. Indeed I am inclined to think 

 that some added reasons have grown out of the increasing 

 applications of biological knowledge to the practical affairs 

 of life. The conditions of our living make ever increasing 

 demands for knowledge of life phenomena, and some com- 

 prehension of biological principles is fast becoming a part of 

 the common intelligence. 



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