ABSTRACT
Organizer and other tissues of urodele gastrulae were labelled by cultivation in glycine-Cu, methionine-Sss, or adenine-8-Ci4. They were then either inserted into the blastocoel of unlabelled hosts or made into ‘sandwiches’ between two flaps of gastrula presumptive ectoderm. Two or three days later the location of the tracer was investigated by stripping film autoradiography. The sandwich experiments gave the clearer results.
The tracer passed into the tissues surrounding the graft and was accumulated mainly in the nuclei, though some was also present in the cytoplasm. A higher concentration was reached in the induced neural tissue and outermost layer of the epidermis than in other tissues.
A greater fraction of adenine was mobile than of the amino-acids.
The evidence suggests that there is no massive transfer of cytoplasmic particles and that there is considerable diffusion of tracer in the form of small molecules. It does not rule out the possibility of a relatively slight transfer of cytoplasmic particles, and, indeed, suggests that there is some specific migration of tracer into induced tissues, though it remains uncertain in what form this occurs.