14 



gametes. Examples are drawn from an extensive range of animal and plant 

 forms, including bacteria and unicellular organisms. 



The book opens with a chapter devoted to general cytology (14 pages). 

 This is followed by a chapter entitled "Significance of fertilization", in which 

 the respective roles of mitosis, meiosis, and syngamy in the economy of the 

 organism (propagation, development, and evolution of the race) are explained 

 (15 pages). 



The remaining five chapters discuss form and differentiation of gametes, ap- 

 proximation of gametes, contact and fusion of gametes, immediate consequences 

 of fertilization, and finally unusual and abnormal forms of fertilization. These 

 chapters range in size from 14 to 30 pages, the longest being that on contact 

 and fusion of gametes. 



The book is profusely illustrated with good drawings and photographs. 

 There is a selected and partly annotated bibliography of 10 pages, conveniently 

 arranged by sub-headings. More than half of the titles cited date from the 

 years elapsed since the publication of Rothschild's monograph. The book is 

 concluded by a good subject index. 



8. THE MOLECULAR BIOLOGY OF DEVELOPMENT 



1965 



by J. Bonner Clarendon Press 



161 pp., 34 figs., 21 tbs. Oxford 



Price: 25s. 



It is common knowledge to-day that one of the fundamental keys to the 

 problem of development is the selective activation of genes. To outline our 

 present knowledge of this process in molecular terms is one of the purposes 

 of this book. 



Better than by an enumeration of the twelve short chapters which it contains, 

 is the book characterized by a free quotation from the "flap" of the dust cover: 

 "The problem of development is first formulated within the framework of 

 molecular biology, and it is shown that the developmental process may be 

 considered as the programmed and orderly repression and derepression of in- 

 dividual genes. This control and programming of genetic activity is then 

 considered on three levels, namely, 1 ) the material nature of the repressor of 

 gene activity, 2) the nature of the genetic switching unit (the nature of the 

 act by which genetic activity is turned on and off), and 3) the nature of the 

 switching network by means of which the individual switching units are 

 integrated into developmental systems. The book provides throughout not 

 only underlying theory, but also description in depth and detail of the 

 experimental procedures of molecular biology as they may be used by the 

 developmental biologist." 



The author draws his examples from both the animal and plant kingdom, 

 but since he himself has worked with plant material, the latter predominates. 

 For instance, much attention is devoted to the action of plant hormones as 

 effector substances. In the last chapter a theoretical model is proposed for a 

 relatively simple developmental "switching network", which is based on plant 

 morphogenesis. However, it is basically valid for animal developing systems 

 as well. In the unifying discipline of molecular biology the distinction between 

 plants and animals loses its significance. 



