PKEFACE. 



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

 principles of the science of Zoology, according to the present 

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

 young student. No similar treatise exists in this country, and 

 indeed some of the topics have not been touched upon in the 

 language, except in a strictly technical form, and in scattered 

 articles. On this account, some of the chapters, such as those 

 on Embryology and Metamorphosis, may at first seem too 

 abstruse for the beginner. But so essential have these sub- 

 jects now become to a correct interpretation of philosophical 

 zoology, that the study of them will hereafter be indis- 

 pensable. They furnish a key to many phenomena which 

 have heretofore been locked in mystery. 



The illustrations have been drawn from the best authorities ; 

 some of them are merely hypothetical outlines, which convey 

 a more definite idea than if drawn from nature ; others have 

 been left imperfect, except as to the parts especially in ques- 

 tion ; a large proportion of them, however, are complete and 

 original. Popular names have been employed as far as pos- 

 sible, and Definitions of those least likely to be understood, 

 will be found in the Glossary. 



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. 



