20 PREFACE. 



pretension than that of being actuated by a sin- 

 cere desire of rendering them accurate and faith- 

 ful, in every particular, and, so far, worthy of 

 acceptance. 



In bringing together and reviewing the labors 

 of others in the same department of science, he 

 has endeavored to do strict justice to all, to ac- 

 knowledge his obligation for information received 

 from each, and to indicate the source from which 

 it is derived. If there are any omissions, in this 

 respect, they have arisen from inadvertence and 

 not from design. It will be noticed that in sev- 

 eral instances he differs in opinion from those 

 who have preceded him, and that he considers 

 several species, described by them, to be merely 

 varieties of, or even identical with, animals before 

 known. In thus exercising his own judgment 

 in opposition to that of persons for whose opinions 

 he entertains the highest respect, he trusts that 

 he has done it in a manner which cannot give 

 just ground of offence. He has no regard for 

 his own views, except so far as they shall be 

 found consistent with truth, and he expects 

 that they will be controverted by others with the 

 same freedom, whenever they are supposed to be 

 erroneous. 



