ACKNOWLEDGEMENTS 



In the preparation of this book I have incurred a considerable amount of 

 indebtedness which is a pleasure to record. 



Many of the illustrations are borrowed, and in each the source is acknowledged. 

 There are, however, five sovirces from which I have liberally drawn, and these merit 

 special thanks : Dr. Gordon Walls, for a number of his original drawings ; Masson et 

 Cie of Paris, who have allowed me to use some illustrations from Rochon-Duvigneaud's 

 classical work, Les Yeux et la Vision des Vertebris ; Dr. Maurice Burton and his 

 publishers, the Elsevier Publishing Co. of Holland, for some illustrations from The 

 Story of Animal Life ; the Royal Society for permission to iise a large number of 

 Lindsay Johnson's illustrations published in their Proceedings ; and Macmillan & Co. 

 for giving free permission to copy a large number of the illustrations of animals in the 

 Cambridge Natural History in the form of inarginal sketches. 



In preparing the illustrations I have had the willing co-operation of Dr. Peter 

 Hansen and the Department of Medical Illustration of the Institute of Ophthalmology, 

 the assistance of which, particularly that of Mr. T. R. Tarrant, the Medical Artist, has 

 been invaluable. The Zoological Society of London has lent me a number of photo- 

 graphs, as also has the Natural History Museum of London, together with specimens 

 of various invertebrates. Professor Ida Mann has allowed me to use a large number 

 of her illustrations of the eyes of animals, and Dr. Kevin O'Day of Melbourne has 

 allowed me to use photographs and slides of the eyes of Monotremes and Marsupials 

 which are unobtainable outside Australia ; while in this Institute Professor Norman 

 Ashton and Dr. Katharine Tansley have provided me with sections and photographs 

 of the eyes of a number of animals. 



In several instances my knowledge of zoology has been brought up to date 

 by the great kindness of Dr. Mary Whitear of the Zoology Department of University 

 College, London, who has read the proofs of those sections dealing with zoological 

 classification ; while Dr. Katharine Tansley and Dr. Robert Weale of this Institute 

 have given me most helpful criticism in some aspects of the visual problems discussed. 

 Miss M. H. T. Yuille, Mr. A. J. B. Goldsmith and my wife have shared with me the 

 onerous task of proof-reading. 



It is difficult for me to express my indebtedness to my secretary. Miss Rosamund 

 Soley, who has borne much of the burden of the technical aspects of the production of 

 this Volume. She has typed and iDrejDared the manuscript, corrected the proofs, and 

 undertaken the immense and somewhat thankless task of verifying the bibliographies, 

 prepared the Zoological Glossary and the Index, and drawn the 350 marginal sketches. 



Finally, my indebtedness to my publishei's, Henry Kimpton, continues to be 

 immense. They have assisted me in every possible way. Why Mr. G. E. Deed con- 

 tinues to put up with my inoods and vagaries after thirty years is to me quite 

 incomprehensible. 



Stewart Duke -Elder. 



