Preface ix 



for permission to photograph specimens in the exhibition rooms of the 

 Museum, literally handed over "the keys to the city*'; to Henry B. 

 Bigelow, Curator of Oceanography, Arthur Loveridge, Curator of 

 Reptiles and Amphibians, and James L. Peters, Curator of Birds, all in 

 the Museum of Comparative Zoology, for much helpful information in 

 their several fields of zoology (but they are not to be held responsible for 

 the author's systems of classification nor for his naming of genera and 

 species) ; to Frank White, photographer for the Biological Laboratories 

 of Harvard University, for expert photographic work, especially the 

 photographing of numerous illustrations from very old books; to James 

 K. Ufford, Director of Photography for the Fogg Museum of Art at 

 Harvard University, for his skill and patience in the photographing 

 of museum specimens under extraordinary difficulties due to cramped 

 spaces and unfavorable lighting; to Maxwell L. French. Staff Assistant 

 of the Museum of Comparative Zoology, for his enthusiastic and effi- 

 cient aid in making museum specimens accessible to the camera; to 

 John H. Neal and William L. Nutting for important aid in the making 

 of drawings for new illustrations. 



Appreciation is due in large measure to officials of The Blakiston 

 Company, especially James B. Lackey, Science Editor and William B. 

 McNett, Art Director, for their generous cooperation, unfailing cour- 

 tesy and patience, and to their staff assistants for highly efficient 

 performance on all phases of the task of publication. 



From my wife I have received constant assistance, including the 

 reading of portions of the text with special reference to pertinency of 

 statements and to points of literary form. 



H.W.U. 



Cambridge, Mass. 

 June 1950 



