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. A. Agassiz's notes and explanations. 



Cambridge, May, 1865. 



NOTE, 



This second edition is a mere reprint of the first. A few 

 mistakes accidentally overlooked have been corrected; an ex- 

 planation of the abbreviations of the names of writers used after 

 the scientific names has been added, as well as a list of the 

 wood-cuts. The changes which have taken place in the opinions 

 of scientific men with regard to the distribution of animal life 

 in the ocean have been duly noticed in their appropriate place, 

 but no attempt has been made to incorporate more important 

 additions which the progress of our knowledge of Radiates may 

 require hereafter. 



Cambridge, January, 1871. 



