The 7-day white Peking duck embryo contains two hemoglobins (Hb's III and IV) which are electrophoretically distinct from the two adult hemoglobins (Hb's I and II). Hemoglobin IV had disappeared in the 14-day embryo, at which time Hb's I and II are evident. The synthesis of Hb III is not restricted to embryonic life but continues in the duckling and ceases before the 10th week of development after hatching.