viii PREFACE 



the Marine Biological Association for the unfailing interest 

 they have shown in this work, and for the many helpful 

 criticisms and suggestions that they have made ; and 

 especially to Mr. H. W. Harvey for his great assistance with 

 Chapter X, concerning which the opinions of a modern 

 hydrographer are invaluable. 



We are also especially indebted to the Council of the 

 Marine Biological Association of the United Kingdom for 

 their kindness in allowing the publishers to have photo- 

 graphs specially taken at the Plymouth laboratory, and 

 for putting the laboratory and library at the disposal of 

 Mr. W. J. Stokoe. 



We are grateful to our wives for the great assistance they 

 rendered in the preparation of the manuscript, and to the 

 father of one of us, Mr. W. Russell, for his care in reading 

 through the MS. 



It has been our aim to illustrate this book with as many 

 original drawings and photographs as we could obtain, 

 supplemented by many beautiful illustrations buried away 

 in the mass of scientific literature and so unfortunately 

 hidden from the eyes of most people. This end could not 

 have been achieved without the cordial co-operation and 

 assistance received from all sides — personal friends, 

 societies, and publishers — and to all and sundry we wish to 

 express our gratitude. We are especially indebted to 

 Mr. Douglas P. Wilson for so lavishly placing at our 

 disposal his many beautiful photographs of shore life from 

 which we chose the illustrations for the following plates : 

 8, 9, 10, ii, 12, 14, 15, 16 bottom, 18, 20, 22, 45 top, 46 

 bottom, 87, 109 top, 127 bottom ; to Dr. Marie V. Lebour 

 for the original paintings for Plates 40, 43, 44, 88 ; to 

 Mr. W. Russell for the original paintings for Plates 31, 50 ; 

 to Dr. T. A. Stephenson for Plate 16 top, and to Mr. H. O. 

 Bull for Plate 29 ; and to Mr. Harry Vandervell for per- 



