Fate mapping study of the endoderm of the 1.5-day-old chick embryo.

Various portions of the endoderm between the levels of the first and the 10th somite of 1.5-day-old chick embryos were marked by local application of the vital dye Dil, and the fate of marked cells was analyzed after cultivation of the embryos for 2 days in vitro.The presumptive area of digestive tract ranging from the posterior pharynx to the jejunum was found to extend bilaterally from the midline of the 1.5-day embryo with a width two or three times as great as the distance between the midline and the lateral edge of the somite. Either side of this area contributed to the same side of the endodermal tube of digestive tract. The anterior and posterior portions generally contributed to the anterior and posterior regions of the digestive tract, respectively, and the cells originating from the portion farther from the midline took the more ventral and posterior position in the digestive tract endoderm. Most of the presumptive areas of the digestive organs in the endoderm of 1.5-day embryo were located in a more anterior position than those in the splanchnic mesoderm.