PREFACE 



The quotation at the head of Chapter I is from Two Lives, 

 by William EUery Leonard, copyright 1922, 1925, by per- 

 mission of the Viking Press, Inc., New York. The quotation 

 from C. Day Lewis's translation of Virgil's Georgics, in a 

 footnote to Chapter III, is used by permission of Jonathan 

 Cape, Limited, London and Toronto. 



The author's wife, Betsy Copping Corner, and his son, 

 Dr. George W. Corner, Jr., have given unfailing encourage- 

 ment and have been patient and thoughtful critics. Mr. 

 Arthur G. Rever has been good enough to read the manu- 

 script and has made useful suggestions. 



The author's researches upon the menstrual cycle of mon- 

 keys, cited in this book, were aided by grants to the Univer- 

 sity of Rochester by the Rockefeller Foundation and the 

 John and Mary R. Markle Foundation. 



GEORGE W. CORNER 



Carnegie Institution of Washington 

 Department of Embryology, Baltimore 



