X PREFACE 



and endless pains he has taken to produce the coloured 

 illustrations from original black and white photographs 

 supplied either by Mr. D. P. Wilson or taken specially in 

 the Plymouth laboratory ; for his care in producing the 

 wash and line drawings under our directions ; and for his 

 generous assistance and advice in all matters pertaining to 

 the arrangement of the illustrations. 



F. S. RUSSELL. 

 C. M. YONGE. 



PREFACE TO SECOND EDITION 



This second edition has been essentially a reprint rather 

 than a revised edition. In consequence it has not been 

 possible to make any substantial alterations. Any errors 

 found in the first edition have, however, been corrected, 

 and in any instance where fresh knowledge has shown 

 previous ideas to be incorrect, new information has been 

 substituted. During the eight years which have elapsed 

 since the first edition was published, considerable additions 

 have been made in our knowledge of the details of life in the 

 sea. These have not, however, involved any change in 

 the essential principles given in the book, and, except for a 

 few minor alterations, the book has needed little revision. 

 New photographs have been used for Plates 58 and 65. 

 Our thanks are due to Mr. G. W. Otter for kind permission 

 to pubUsh those on Plate 58 and to Mrs. C. M. Yonge for 

 Plate 65. The titles of a few recently published books 

 dealing with the sea have been added to the bibliography 

 at the end. 



F.S.R. 



C.M.Y. 



