source of the umbilical cord, and translocate to the gonads, differentiating there into sperm
and eggs. In light of emerging data on the posterior embryonic–extraembryonic interface,
and the poorly studied but vital fetal–umbilical connection, we have reviewed the past
century of experiments on mammalian PGCs and their relation to the allantois. We
demonstrate that, despite best efforts and valuable data on the pluripotent state, what is and …