Studies on the migration of primordial germ cells in early chick embryos: cultivation of hypoblast explants from the germinal crescent area.

The hypoblast from the germinal crescent area of stage 4 to 5 chick embryos, when grown on a glass surface, spreads out as a thin and continuous cellular sheet. Primordial germ cells (PCCs) are found to migrate individually over this hypoblast monolayer (as they do in vivo) and, perhaps even more striking, their morphological features during migration are remarkably similar to those observed in vivo. Inasmuch as this in vitro system permits direct observations of PGCs migrating on their natural, rather than artificial, substratum undoubtedly it will prove to be an effective means of studying the mode of PGC migration in early chick embryos.