ogy are moreover in several respects not up to date. We therefore advise the 

 author to prepare the following edition of the book in collaboration with an 

 experimental embryologist, so that both fields of research receive the same 

 attention and reach the same high standard. 



The synthesis of experimental and comparative embryology, although of very 

 great interest, meets many difficulties. Such a synthesis can only be made in 

 general outlines, and only as far as comparable processes are concerned. The 

 most recent experimental analysis demonstrates that very pronounced quantita- 

 tive and partially even qualitative differences exist between ., comparable" pro- 

 cesses in related species, so that great caution is required as to how far proces- 

 ses can be considered as actually comparable in the various groups of Verte- 

 brates. 



P. D. NIEUWKOOP 



"EMBRYOLOGISCHER ATLAS FuR STUDENTEN" 

 1954 



by H. Voss Gustaf Fischer Verlag. Jena 



181 pp. with 270 figs Price: 17.— D.M. 



This embryological atlas shows the development of an amphibian, Bufo 

 vulgaris, a bird, Gallus domesticus, and a mammal, Sus scrofa, in the form of 

 a large number of photographs of microscopical sections through embryos of 

 different age, reproducing each twentieth section. The development of Bufo is 

 reproduced at the stages morula, blastula, gastrula, neurula and five further 

 steps up to the tadpole stage. The development of the chick is given in seven 

 steps, while only two embryos have been chosen for the representation of the 

 development of the pig. 



Although the idea of showing the students the development of an animal in 

 a series of successive stages is very valuable, the way in which this has been 

 tried in this atlas meets many serious objections. The very restricted number 

 of stages does not allow any comparison, and does not give the student any 

 idea of the morphogenetic processes leading from one stage to the other. The 

 idea of reproducing a complete set of serial sections is, in our opinion, not 

 tenable, when it leads to a drastic reduction of the number of stages presented. 

 A great number of photographs is entirely superfluous for the understanding of 

 the spatial structure of the embryo at a certain stage. It would therefore have 

 been much better to have selected the most instructive sections at each stage 

 and to have considerably increased the number of stages, so that the successive 

 steps would have been much more comparable. This holds for the development 

 of all three animals, but particularly for that of the chick and the pig. 



Great objections are felt against the way the individual sections have been 

 reproduced. The photographic procedure has not been adapted to the staining 

 method used (or vice versa), so that the photographs hardly show any contrast 

 among the various structures. Many pictures have moreover been reproduced 

 on too small a scale. In the pig, where the sections were rather large, this might 

 have been partially unavoidable, but in the chick there is no argument for 

 reproducing in every section the extra-embryonic tissue which does not show 

 any changes. It would have been adequate to have given the most important 

 details at the proper magnification. 



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