embryology can no longer be limited to amphibian forms but will take in all embryos from 

 the lowest to the highest phyla. 



It would be impossible for the author to properly acknowledge all of the help that he has 

 received in organizing this book. He has enjoyed universal and wholehearted coopera- 

 tion, often entailing considerable time and effort on the part of contemporary investiga- 

 tors. Where figures, graphs, or photographs have been reproduced, and where specific 

 investigators have constructively helped to organize certain sections, specific acknow- 

 ledgements are made. It is with pleasure that the author acknowledges here the permis- 

 sion granted by The Wistar Institute of Anatomy to reproduce items from papers appear- 

 ing in their various journals. It must be emphasized again that this book is made possible 

 by the efforts of many experimental embryologists, many deceased, many active, and an 

 increasing number "presumptive". If biology students who attempt these various proce- 

 dures are thereby stimulated to make further contributions to the field of experimental 

 embryology, all the effort expended in its compilation will have been justified. 



Roberts Rugh 



New York 

 September 1948 



INTRODUCTION TO THIRD EDITION 



This third edition of the Experimental Embryology appears simply as a direct response 

 to the persistent demands on the part of a small but select group of advanced experimen- 

 talists who found the previous edition so useful that they began to make photostatic copies 

 when the supply was exhausted. 



Many of the old references have been deleted, and new ones added. New sections include 

 the disassociation and reaggregation of cells; basic tissue culture techniques; and use of 

 the mouse embryo. For the last decade the author has been studying the effects of ioniz- 

 ing radiations on the rodent (mouse and rat) embryos and he is convinced that the mam- 

 malian embryo can now be made available to all advanced biology students for important, 

 rewarding, and exciting research. This chapter on the mouse embryo is merely an in- 

 troduction to the possibilities ahead. 



Most publishing houses are conducted on a cold and closely calculating business basis. 

 For Burgess of Minneapolis to republish a book such as this, which can never have wide 

 adoption because of its very specialized subject, is a generous gesture which, the author 

 hopes, will stimulate many biologists to research in embryology. 



Roberts Rugh 



New York 

 February 1962 



