ABSTRACT
The histogenetic and neoplastic potentials of defined regions of the 8th day mouse embryonic egg cylinder were examined following ectopic transfer to beneath the testis capsule. No differences in histogenetic potential were detected between anterior and posterior slices of the embryo, either when composed of all three germ layers or of embryonic ectoderm alone. Small anterior and distal fragments of embryonic ectoderm also produced similar histogenetic profiles, although posterior fragments failed to grow in this ectopic site. The histogenetic potential of anterior and distal fragments exceeded the developmental fate ascribed to these two regions in the embryo (Beddington, 1981). There was some evidence for regionalization with respect to neoplastic potential, anterior slices of the embryo giving rise to a higher incidence of embryonal carcinoma cells than posterior slices.
