PREFACE 



THE conviction has been gradually forced upon the 

 writer that persons who wish to get an insight into 

 zoology as a science have difficulties in finding the 

 necessary helps. The conventional treatise on 

 zoology deals chiefly with facts about animals and 

 certain phenomona of their lives, but omits a con- 

 current account of the results of zoological advances. 

 In educational institutions, also, the method of 

 using animal types as the sole background of knowl- 

 edge, together with drill on the facts observed in the 

 laboratory, has resulted in a one-sided and inad- 

 equate conception of zoology. 



Zoological progress represents a stream of 

 thought not merely accretions of knowledge about 

 animals. In order to comprehend zoology in the 

 light of its progress it is necessary to trace its main 

 currents; merely to accumulate a certain set of facts 

 about animals will cause one ever to remain outside 

 of the subject. It is well to remember also that the 

 interpretations resulting from zoological observa- 

 tions have had great influence in liberating thought 

 and on general intellectual advancement. 



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