PEEFACE 



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 zoology 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 zoology 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 



