V jii PREFACE 



have been placed in an appendix under the heading of Suggested Readings. 



My wife and several of my friends have generously helped in the con- 

 struction of this book. Dr. Lucena Jaeger initiated the writing by recording 

 my lectures to a class in embryology. Without this help the book would never 

 have been written. Mr. Stanley Burnshaw of the Dryden Press encouraged 

 the further development of the first draft into the present form. His skill in 

 the art of book construction made me decide to go on with the writing. 

 Professors L. V. Heilbrunn and S. M. Rose read the manuscript and sug- 

 gested extensive revisions which are now incorporated into the final form. 

 Mr. David Klein, of the Dryden Press, taught me some valuable principles 

 of writing. 



Professor A. W. Pollister, of Columbia University, generously turned 

 over to me all his drawings of the embryos of Kana sylvatica. Professor J. A. 

 Moore, of Columbia University, furnished me with some unusually clear pic- 

 tures of the developing egg of the salamander. The drawings were made by 

 Mr. Jack Godrich, who showed remarkable patience and care in transposing 

 my crude classroom sketches into finished illustrations. 



Finally, the book owes much to the growing number of embryologists 

 who have painstakingly investigated the problems of development. The text 

 draws heavily upon the results of their experiments. Special mention should 

 be made of one of the sources for the chapter on human embryology. I have 

 derived much pleasure from reading W. F. Windle's Physiology of the Fetus 

 and recommend it to others who are interested in the development of func- 

 tion. This subject is at least as important as the development of structure, 

 and it deserves attention in elementary textbooks. 



The writing of this book is in the nature of an experiment in combining 

 experimental and descriptive studies. Like any experiment, it is open to 

 criticism, and I shall welcome suggestions and corrections. 



L. G. B. 

 Columbia University 

 March 10, 1949 



