ABSTRACT
Tiedemann and his collaborators (Tiedemann, Becker & Tiedemann, 1961) have demonstrated both neural- and mesodermal-inducing activity in extracts from whole gastrulae and neurulae and from ventral gastrula ectoderm of Triturus alpestris. They have also obtained a wide range of inductions from subcellular fractions of 9-day chick embryos (Tiedemann, Kesslring, Becker & Tiedemann, 1962). Microsomal and ribosomal fractions were particularly active. A further finding was that the inducing activity of gastrula ectoderm could be enhanced by phenol treatment (see Tiedemann, 1963, for review). Latterly most of the work has been pursued with chick extracts, and no systematic study of the inducing ability of extracts from different embryonic stages of an amphibian has so far been reported.
