6 PREFACE. 



E. Desor for many years an associate of Professor Agassiz, from Count 

 Pourtales and E. C. Cabot, Esq., and also from Professor Asa Gray, 

 by valuable suggestions in the revision of the lettei--press. 



The first part is devoted to Comparative Anatomy, Physiology, 

 and Embryology, as the basis of Classification, and also to the illus- 

 tration of the geographical distribution and the geological succession 

 of Animals ; the second to Systematic Zoology, in which the prin- 

 ciples 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. 



BosTOX, Jwie 1, 1S48. 



PREFACE TO THE REVISED EDITION. 



In revising the present work, the authors have endeavored to 

 render more precise those passages which admitted of too broad a 

 signification or of a double interpretation; and to correct such errors 

 as had arisen from inadvertence, or such as the rapid progress of Sci- 

 ence has disclosed. They are indebted for many suggestions on 

 these points to several distinguished teachers who have used the work 

 as a text book, and more especially to Professor Wyman, of Harvard 

 University. Several entirely new paragraphs have also been added. 



A list of some of the principal authors who have made original 

 researches, or of treatises which enter more into detail than was ad- 

 missible in an elementary work, has been given at the close of the 

 volume, for the use of those who would pursue the subject of 

 Zoology in a more extended manner. 



The work having thus been revised and enlarged, the authors sub- 

 mit it to the pubhc with increased confidence in its accuracy and 

 usefulness. 



Boston, February 1, 1851. 



