PREFACE. 



rately drawn from nature ; others have been left imper- 

 fect, except as to the parts especially in question ; a large 

 proportion of them however, are accurate and original. 

 Popular names have been employed as far as possible, 

 and to the scientific names an English termination has 

 generally been given. 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. E. Desor, for many years an asso- 

 ciate of Professor Agassiz, from Count Pourtales and 

 E. C. Cabot, Esq., and also from Prof. Asa Gray, by 

 valuable suggestions in the revision of the letter-press. 



The first part is devoted to Comparative Physiology 

 as the basis of Classification ; the second to Systematic 

 Zoology, in which the principles of Classification will 

 be applied, and the principal groups of animals will be 

 briefly characterized. 



Should our aim be attained, this work will produce 

 more enlarged ideas of man's relations to Nature, and 

 more exalted conceptions of the plan of Creation and 

 its Great Author. 



BOSTON, JUNE 1, 1848. 



