FATE MAPPING STUDY OF THE SPLANCHNOPLEURAL MESODERM OF THE 1.5-DAY-OLD CHICK-EMBRYO

Various portions of the splanchnopleural mesoderm lateral to the somites of 1.5-day chick embryos were marked in ovo by local injection of DiI, and the distribution of the labelled cells in the digestive-tract mesoderm formed after 3 days' reincubation was analysed. The presumptive area of the digestive organs was confined to bands of splanchnic mesoderm lying lateral to the somites, on both sides, with a width two or three times that between the midline of the embryo and the lateral edge of the somite. Each band generally contributed cells to its own side of the digestive-tract mesoderm, except for the region around the bile duct. The anterior and posterior portion of the pre-gut area contributed cells to the anterior and posterior region of the digestive tract, respectively, but label originating from the portion furthest from the somite took the more ventral and posterior position. Thus, the presumptive areas of the respective digestive organs were located anteroposteriorly in the same order as in the digestive tract with their boundaries lying oblique to the embryonic axis.