AUTHOR'S NOTE 



This book is based in part on studies in the comparative 

 physiology of the kidney carried out by the writer dur- 

 ing the past thirty years at the New York Aquarium, the 

 Mount Desert Island Biological Laboratory at Sahsbury 

 Cove, Maine, the Bermuda Biological Station for Re- 

 search, the University of Virginia School of Medicine, 

 and, since 1928, at New York University College of 

 Medicine, in later years supported by the Common- 

 wealth Fund and the National Heart Institute of the Na- 

 tional Institutes of Health. 



Field studies on the lungfish in Central Africa in 1928 

 and on fresh-water elasmobranchs in Siam and Malaya 

 in 1930 were conducted while he was a FeUow of the 

 John Simon Guggenheim Memorial Foundation. The 

 evolutionary history of the kidney as developed here was 

 first presented in a short essay on that subject delivered 

 in 1939 as a J. L. Porter Lecture at the University of 

 Kansas School of Medicine. 



