

PREFACE 



the north and northwest Pacific in 1906, on which 

 cruise the author served as acting naturalist in charge 

 of the scientific work of the vessel. 



No proper appreciation of the conditions under 

 which life in the sea exists is possible without some 

 acquaintance with the subject of oceanography, and 

 this subject has therefore somewhat extensively en- 

 gaged the attention of the author. 



Of itself the personal history of any individual 

 means nothing. It merely indicates that the indi- 

 vidual has had a certain range of opportunities for 

 becoming interested in, and later following out, cer- 

 tain lines of investigation. Whether the individual 

 has shown himself alive to those opportunities and 

 has profited by them can be judged only by his work. 



The subject of the interrelationships of animals in- 

 volves an extensive acquaintance with all types of 

 animals in their adult, young and embryonic stages. 

 It also involves an acquaintance with the fossil re- 

 mains of the animals which have existed in past ages. 

 So any presentation of this subject in a volume of 

 reasonable size means a very rigid selection of essen- 

 tial facts from an enormous mass of pertinent material. 



Fifty years ago it was possible to include in a vol- 

 ume of this kind a series of footnotes or a bibliography 

 giving an adequate list of references to original records 

 and sources of information. But such a procedure is 

 no longer possible. An adequate list of references to 

 the thousands of books and articles consulted in the 

 preparation of this work would occupy more pages 

 than the book itself. 



[viii] 



