DR. JOHN W. SAUNDERS. JR. 



DEPARTMENT OF BIOLOGY 

 MARQUETTE UNIVERSITY 

 MILWAUKEE 3. WISCONSIN 



PREFACE 



A symposium on "Formation and Early Development of the 

 Embryo," held December 27, 1955, at the Second Atlanta Meet- 

 ing of the AAAS, served as the basis for the present volume. The 

 symposium emphasized problems of early development and of 

 the initiation of development. However, in selecting this general 

 area for discussion the organizing committee did not intend to 

 imply that the problems are considered to be fundamentally 

 different from those encountered in later development. In fact, 

 many of the contributions presented here indicate the generality 

 of the problems of developmental change at any stage along with 

 the special nature of the particular events studied. It may also be 

 said that an understanding of early, as well as later, development 

 depends largely on knowledge of the manner of formation of the 

 egg, that is, of the processes that endow the oocyte, in contrast to 

 other tissue cells, with the capacity to form a new individual. 

 The first paper deals with one aspect of this subject which is also 

 partly considered in some of the others. The next five papers treat 

 principally with the initiation of development, and the remain- 

 ing seven center primarily about subsequent events as related to 

 nuclear and cytoplasmic factors. 



As with most symposia the general purpose of this one was to 

 bring together a group of individuals working in related fields 

 so that there would be opportunity for participants and audience 

 to profit directly from exchange of knowledge and ideas. It was 

 also decided that the presentations be made available to others 

 in published form. 



Since the symposium was planned for a one day session, the 

 number of speakers was correspondingly restricted. However, for 

 the purpose of the present volume it was considered desirable 

 that the coverage of the general field be expanded somewhat. 

 This has been done by the inclusion of articles requested from 

 some additional investigators, in this country and abroad, whose 

 work pertains to the subjects under consideration. 



