Although this is basically a translation of the second German edition
published in 1970, more recent experimental findings have, in several
instances, been incorporated into the text. Furthermore, we have tried
to explain some of the experiments, and their possible interpretations,
in a more precise way. I am very grateful to Dr. David Turner; in
addition to translating the text, he was able, thanks to his experience
in developmental biology, to suggest a number of improvements in the
course of our collaborative discussions. Zurich, Spring 1974 ERNST
HADORN Preface to the Second German Edition The guiding principle of the
first edition remains in force. That is, the methods and results of
developmental research are intro- duced wherever possible with the aid
of experiments on am- phibians. However, the scope of the material has
been substantially ex- panded in newly introduced chapters on the
migrations and affinities of somatic and germ cells as well as on the
action of genetic factors in early development. These are fields of
study which are at the center of today's research. In addition, numerous
new findings have been incorporated into the text. The author hopes that
this little book will continue to facilitate understanding of exciting
research problems, for the interested layman as well as for the teacher
and student of biology.
