PREFACE 



This book is a plain account of the development of the never- 

 failing resource of the embryologist, the chick. It has been neces- 

 sary to fill certain gaps in our knowledge of the development 

 of the chick by descriptions of other birds. But the account 

 does not go beyond the class Aves, and it applies exclusively 

 to the chick except where there is specific statement to the 

 contrary. Projected chapters on the integument, muscular sys- 

 tem, physiology of development, teratology, and history of the 

 subject have been omitted, as the book seemed to be already 

 sufficiently long. The account has been written directly from 

 the material in almost every part, and it has involved some 

 special investigations, particularly on the early development 

 undertaken by Doctor Mary Blount and Doctor J. T. Patterson, 

 to whom acknowledgments are due for permission to incor- 

 porate their results before full publication by the authors. As 

 the book is meant for the use of beginners in embryology, refer- 

 ences to authors are usually omitted except where the account 

 is based directly on the description of a single investigator. A 

 fairly full list of original sources is published as an appendix. 



Figures borrowed from other publications are credited in 

 the legends to the figures. The majority of the illustrations are 

 from original preparations of the author: Figures 46, 48, 50, 51, 

 52, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 71, 72, 73, 74, 75, 99, 

 105 and 106 were drawn by Mr. K. Hayashi; the remainder of 

 the original drawings were executed by Mr. Kenji Toda. The 

 photographs in Figures 118, 119, 120, 168, 181, 182, 189, 194, 197, 

 and 231 are the work of Mr. Willard C. Green. Some of the 

 figures may be studied with advantage for points not described 

 in the text. 



Acknowledgments are also due my colleague, Professor W. L. 

 Tower for much assistance, and to Doctor Roy L. Moodie for 

 special work on the skeleton, and photographs of potash prep- 

 arations reproduced in Figures 242, 246, 249 and 250. 



The best introduction to the problems opened up by the study 



iii 



