Appearance of Primordial Germ Cells in Young Chick Blastoderms Cultured in vitro. (primordial germ cells/blastoderms/chick)

Appearance of primordial germ cells (PGCs) in young chick blastoderms was investigated by the cultivation of only the epiblast or hypoblast. Presumptive PGCs exist in the epiblast before primitive-streak formation. They translocate gradually to the lower layer during early stages of primitive-streak formation, though substantial number of presumptive PGCs remain in the upper layer. The existing primary hypoblast under the epiblast is dispensable for the further differentiation of the PGCs.