the yolk), and with regulatory mechanisms involved in calcium metabolism. Part 

 two discusses reproductive adaptions. It starts with three chapters on calcium 

 in mammalian reproduction, respectively dealing with pregnancy, lactation, and 

 calcium metabolism of the foetus and newborn. Then follow two pairs of chapters 

 dealing with calcium metabolism in the mother animal and the embryo in birds 

 and reptiles respectively. The penultimate chapter is devoted to calcium meta- 

 bolism in adult and larval amphibians (mainly anurans). The book is concluded 

 by a brief chapter presenting conclusions and speculations. 



The book contains many illustrations, most of them graphs, and numerous 

 tables in the text, summarizing the factual evidence for generalized statements in 

 the text. In addition, there are nine excellent photographic plates. Each chapter 

 has its own bibliography, citing both the most recent and the important older 

 literature of all language areas. The book is concluded by a subject index, but an 

 author index is lacking. 



10 VOM EI ZUM EMBRYO 



1968 

 By E. Blechschmidt Deutsche Verlags-Anstalt 



136 pp., 54 illustr. Stuttgart 



This book is difficult to evaluate. It is not even clear for which category of 

 readers it is written, although it seems to be meant primarily for the cultivated 

 layman. It is based solely on the author's own ideas, which were already partially 

 incorporated into many of his earlier, more specialized publications. The present 

 outline claims to present a completely new theory of human development. The 

 author's viewpoint is certainly novel; in how far it really adds much to our under- 

 standing of human development must be left to the individual reader to decide. 



What this new viewpoint is, is difficult to assess briefly, partly on account of 

 the style, which is often nebulous and more typical of German philosophy than 

 of natural science. The author characterizes the method he uses as "kinetic 

 anatomy" or "developmental dynamics". His explanation of both morphogenesis 

 and differentiation invokes, among other things, "formative movements" (Ge- 

 staltungsbewegungen) asserted to take place in so-called "metabolic fields" 

 (Stoffwechself elder), which are morphologically definable (sic!). The form- 

 ative movements are described in terms of "growth tension" (Wachstumszug), 

 "growth pressure" (Wachstumsdruck), "material fluxes" (Materialbewegun- 

 gen, Fluxionen) and other analogues of mechanical terminology. Amazingly, 

 all these forces and movements are inferred exclusively from the gross and 

 microscopic morphology of the embryo. There is no attempt to relate them to 

 experimental evidence, and the author apparently does not even consider them 

 as needing experimental verification. In fact, his interpretations are frequently 

 in conflict with current concepts of both experimental and comparative em- 

 bryology. 



These are only a few salient points in the author's train of thought. He pre- 

 sents other ideas, e.g. on the role of the genes and of exogeneous so-called 

 "developmental stimuli" (Entwicklungsreize), which are even vaguer than the 

 ones mentioned above. 



The book is beautifully produced and superbly illustrated with black-and- 

 white and coloured drawings and photographs. The photographs of human 

 embryos are based on specimens partly from the Carnegie collection, and partly 

 from the author's own extensive collection at Gottingen University. 



17 



