PREFACE 
THE authors present this book as an elementary ac- 
count of animal ecology—that is, of the relations of ani- 
mals to their surroundings and their responsive adaptation 
to these surroundings. The book takes the observer’s point 
of view, who is especially concerned with the reasons for 
the varied structure and habits of animals. To understand 
how naturally and inevitably all animal form, habit, and 
life are adapted to the varied circumstances and conditions 
of animal existence should be the motive of the beginner in 
this fascinating study. The greatest facts of life, except 
that of life itself, are seen in the marvelously perfect meth- 
ods which Nature has adopted in the structure and habits 
of animals. The keen observation of a fact should lead 
the student to inquire into the significance of that fact. 
The veriest beginner can be, and ought to be, an independ- 
ent observer and thinker. In the study of zodlogy that 
phase which treats of the why and how of animal form and 
habit not only absorbs the attention of the most advanced 
modern scholars of biology, but should also appeal most 
strongly to the beginner. The beginner and the most 
enlightened thinker in zodlogy should each have the same 
point of view. With this belief in mind the authors have 
tried to put into simple form the principal facts and 
approved hypotheses upon which the modern conceptions 
of animal life are based. 
It is unnecessary to say that this book depends for its 
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