ferred to specifically in the chapter as well as others selected by the 

 authors as useful sources of information concerning the various topics 

 discussed in the chapter. At the end of the book, in place of the usual 

 long list of papers, we have provided an annotated list of books, reviews, 

 symposia, and some classical papers as a guide to the teacher and 

 student. 



The authors are indebted to Drs. N. G. Anderson, Wolfgang Beer- 

 mann, H. G. Callan, C. deDuve, R. E. Duncan, A. Ficq, Helen Gay, 

 Frangoise Haguenau, Daniel Mazia, Barbara McClintock, R. G. E. 

 Murray, B. R. Nebel, C. Pavan, C. M. Pomerat, Keith R. Porter, Fred 

 Rapp, O. W. Richards, George G. Rose, Syoito Sato, Arnold H. Sparrow, 

 T. N. Tahmisian, P. O. T'so, D. von Wettstein, W. Gordon Whaley, 

 M. H. F. Wilkins, Phihp S. Woods, and Ralph W. G. Wyckoff, and to 

 Mr. P. G. Coleman, Mr. L. V. Leak, and Mrs. Lillie Wang who have so 

 generously contributed photomicrographs from their own personal 

 studies. The acknowledgement in figure captions is only a small expres- 

 sion of the authors' appreciation to writers and publishers from whom 

 illustrations have been borrowed. 



Special thanks are due Mrs. A. Engle, Librarian, Western Reserve 

 University, for assistance in obtaining reference materials and Mr. 

 Edward Pfister for preparation of many of the drawings in Chapter IL 



The authors express their appreciation to Miss Gabriele Miihling, Miss 

 Carolyn Roth, Mrs. Sarah Au, Mrs. Jill Oakley, and Mrs. John H. Mor- 

 rison for help in preparing the manuscript; to Dr. Jack Van't Hof and 

 Mr. Paul Van Dreal for providing and checking information; and to 

 Mr. P. G. Coleman for assistance with the illustrations. 



The authors acknowledge the interest and helpful cooperation shown 

 by members of the editorial staff of the Reinhold Publishing Corporation, 

 especially Mr. James Ross, Managing Editor, and Mrs. Dorothy Donath, 

 Copy Editor. 



G. B. Wilson 

 John H. Morrison 

 East Lansing, Michigan 

 Kent, Ohio 

 September, 1961 



X / PREFACE 



