Stage X is one of the formation stages in birds at which the blastoderm area is distinguished by two areas of area pellucida (AP), which is responsible for formation of embryonic tissues and primordial germ cells (PGCs), and area opaca (AO) which forms the extra-embryonic tissues. PGCs are multipotent stem cells that give rise to spermatogonia or oogonia. The present study was carried out to describe the characteristics of PGCs in stage X of pheasants\\\\\\\\\\\\\\\' embryo using a transmission electron microscope (TEM). The blastoderm was dissected out from embryos which were already incubated for 12 h. Toluidine blue was used for staining semithin sections; also, lead citrate and uranyl acetate were used to stain ultrathin sections. The obtained TEM images of PGCs elucidated that the nucleus was situated eccentrically and had a compact spherical structure. Moreover, the nucleolus appeared elongated and eccentrically located. The cytoplasm was composed of yolk granules and glycogen particles. Mitochondria were observed as round structures in the cytoplasm. The most important finding was that PGCs contained yolk granules, mitochondria and small amount of glycogen at this stage.

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