The various aberrant sex chromosome constitutions in man are extensively 

 reviewed. 



Chapter 10 then deals with sex chromatin in man and other mammals (with a 

 discussion of the Lyon hypothesis concerning the differential inactivation of one 

 X-chromosome in female cells), and Chapter 11 discusses the concept and 

 characteristics of heterochromatin. The final chapter, which deals with the 

 function of the sex chromosomes in development, is significantly brief, showing 

 the paucity of knowledge in an area that is of immediate concern to embryologists. 

 The author makes clear that this area is still largely one of speculation. 



The book is well-illustrated. It has a bibliography of 41 pages, which is up-to- 

 date until 1966, and author and subject indexes. 



6 ESSAYS IN THE HISTORY OF EMBRYOLOGY AND BIOLOGY 



1967 



By J. M. Oppenheimer M.I.T. Press 



374 pp. Cambridge, Mass. - London 



Price: 117 s. 



Contents: Embryological concepts in the twentieth century; Questions posed by classical 

 descriptive and experimental embryology; Ross Harrison's contributions to experimental embryo- 

 logy; Analysis of development: problems, concepts and their history; Analysis of development: 

 methods and techniques; Embryology and evolution: nineteenth century hopes and twentieth 

 century realities; An embryological enigma in the origin of species; The non-specificity of the 

 germ-layers; K. E. von Baer's beginning insights into causal-analytical relationships during 

 development; John and William Hunter and some eighteenth century scientific moods; John 

 Hunter, Sir Thomas Browne and the experimental method; William Harvey and historical change; 

 William Gilbert: plant grafting and the grand analogy; Postscript: additional references. 



The author of this book, who has been an active embryologist as well as a 

 noted writer on the history of this subject for many years, has brought together 

 in this book thirteen of her most important essays, originally published elsewhere 

 in the course of more than two decades (the oldest essay dates from 1940, the 

 most recent one from 1966). The author writes in her preface that "... a number 

 of us who are working embryologists feel that our life in our laboratories is made 

 more meaningful to us when we know something about our intellectual fore- 

 bears . . . [The essays] are presented more or less in reverse chronological order 

 with respect to their content . . . The design of the volume is thus intended to 

 conduct us from what we know best toward what we see only more dimly." 



None of the essays except the last is illustrated. There is a short postscript 

 giving references to books and articles on the history of science not yet in print 

 when the essays were first published. The book is beautifully printed; it is 

 concluded by an author index. 



7 PHILOSOPHISCHE PROBLEME 



DER ONTOGENETISCHEN ENTWICKLUNG 



1967 



By W. Plesse VEB Gustav Fischer Verlag 



128 pp., 7 figs., 1 table Jena 



(paper-bound) Price: MDN 15. — 



This monograph contains a philosophical analysis of the phenomena of onto- 



15 



