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PREFACE. 



THE design of this work is to furnish an epitome of the leading 

 principles of the science of Zoology, as deduced from the present 

 state of knowledge, so illustrated as to be intelligible to the begin- 

 'ner. No similar treatise now exists in this country, and, indeed, 

 some of the topics have not been touched upon in the English lan- 

 guage, unless in a strictly technical form, and in scattered articles. 

 On this account, some of the chapters, like those on Embryology 

 and Metamorphosis, may, at first, seem too abstruse for scholars in 

 our common schools. This may be the case, until teachers shall have 

 made themselves somewhat familiar with subjects comparatively new 

 to them. But so essential have these subjects now become to a correct 

 interpretation of philosophical zoology, that the study of them will 

 hereafter be indispensable. They furnish a key to many phenomena 

 which have been heretofore locked in mystery. 



Being intended for American students, the illustrations have been 

 drawn, as far as possible, from American objects : some of them are 

 presented merely as ideal outlines, which convey a more definite 

 idea than accurate sketches from nature ; others have been left im- 

 perfect, except as to the parts especially in question ; a large propor- 

 tion of them, however, are accurate portraits from original drawings. 

 Popular names have been employed as far as possible, and to the 

 scientific names an English termination has generally been given ; 

 but the technical terms have been added, in brackets, whenever mis- 

 understanding was apprehended. Definitions of those least likely 

 to be understood, may be found in the Index. 



The principles of Zoology developed by Professor Agassiz in his 

 published works have been generally adopted in this, and the results 

 of many new researches have been added. 



The authors gratefully acknowledge the aid they have received, 

 in preparing the illustrations and working out the details, from Mr. 



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