Cell that arises from the endodermal germ plasm and can be detected by NF stage 28 in the endodermal mass. At NF stages 42-47, PGCs migrate to the two genital ridges, which are the first rudiments of the gonads. By NF stage 50, the PGCs begin to loose their yolky material. In males, starting at NF stage 52, PGCs migrate from the genital ridge cortical region into the medullary tissue, where they will form primary spermatogonia at sexual maturity. In females, the medullary tissue remains free of PGCs; they instead embed in the cortical region and multiply to form primary oogonia, which will mature into ova at sexual maturity.