VI PREFACE. 



A few words of explanation are necessary with ref- 

 erence to the joint authorship of the book. The draw- 

 ings and the investigations, where they are not referred 

 to other observers, have been made by MR. A. AGASSIZ, 

 the illustrations having been taken, with very few ex- 

 ceptions, from nature, in order to represent the animals, 

 as far as possible, in their natural attitudes ; and the 

 text has been written by MRS. L. AGASSIZ, with the 

 assistance of MR. AGASSIZ'S notes and explanations. 



CAMBRIDGE, May, 1865. 



