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In the first part on plasmatic maturation of the egg, he comes to the conclusion
that there is a causal sequence in plasmatic and nuclear maturation. The
spatial distribution of the plasmatic inclusions is based upon the structure of the
"groundplasm". The inclusions have no organ-genetic significance, but can be
necessary for the normal development of certain organ-systems.
From the second part on determination the author concludes that the principle
of progressive determination does not hold for the cleavage period up
to the blastula stage. Determination is not based upon a special segregation of
organ-forming substances, but must depend upon the structure of the groundplasm
which is also the seat of the power of regulation. The local properties of
the ground plasm determine the differentiation of the enclosed nucleus. The role
of cleavage is thought to be the provision of totipotent nuclei in the various
plasm areas and the spatial segregation of these groundplasm areas.
The third part deals with the various gradient theories and the phenomena
of induction and organization. The author finds many points of correspondence
with the conclusions made in Child's book "Patterns and problems of
development", 1941. He however denies that gradients are based upon differences
in metabolic activity, but states that the latter are merely an expres-
sion of processes of differentiation.
In the last part the relation between the genes and the plasm gradients is
discussed. The author concludes that gradients actually exist and play a decisive
role in the process of differentiation. Their nature and origin remain however
questionable. He denies the role of substances as well as metabolic gradients,
but concludes that differentiation must be based upon gradients in the
structure of the groundplasm. Direct evidence is however still restricted.
So far the author's considerations are very well argued. His further suggestion
that chromosomes also possess gradients, and that genes of a certain
chromosome gradient traject can only react with a certain plasm gradient
traject is still too speculative, and reduces to some extent the great value of
this important work.
This very interesting theoretical work deals with a large number of fundamental
problems, in which, we hope, all embryologists will be interested, so
that this work will contribute to a sharper theoretical planning of the experimental
analysis and consideration of the results obtained, which is a highly
desirable aspect. The fact that the work has been written in war time, and
had to wait so long before publication could be prepared, has led unfortunately
to the fact that several recent advances in the experimental analysis have not
been incorporated and synthesized in this work.
P. D. NIEUWKOOP
"MITOSE,
die Bewegung der Chromosomen bei der Zellteilung"
1954
by Fr. Schrader Verlag Franz Deuticke, Wien
150 pp. with 19 figs Price: ?
Since 1944 so much progress has been made in the analysis of the process
of mitosis, changing our opinions, that a revision of the first edition has become
highly desirable. Particularly the use of the phase contrast microscope and the
polarisation microscope, and the development of new techniques for the electron
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