Heterotypic differentiation of chick allantoic endoderm under the influence of various mesenchymes of the digestive tract.

Dissociation and reassociation experimentsin vitro were carried out to investigate the differentiation potency of chick allantoic endoderm under the influence of digestive tract mesenchymes. 1. The allantoic endoderm, when cultured alonein vitro, shows no differentiation whatsoever. 2. The allantoic endoderm, when cultivated combined with the mesenchyme of oesophagus, can differentiate into a stratified cuboidal epithelium, similar to that of the embryonic oesophagus. 3. Cultivation of the allantoic endoderm combined with the proventricular mesenchyme causes differentiation of cylindrical epithelium and glands, which are characteristic of the embryonic proventriculus. 4. The combination of the allantoic endoderm and the gizzard mesenchyme results in the differentiation of pseudostratified columnar epithelium, the cells of which possess glycogen granules like those in the normal embryonic gizzard. 5. If the allantoic endoderm is cultured on the mesenchyme of the small intestine, the endodermal cells are converted into simple columnar epithelial cells similar to those of normal embryonic small intestine. 6. The competence for the heterotypic development of the allantoic endoderm appears to be a function of a developmental time sequence: it is highest in the youngest (3-day) allantoic endoderm, and gradually lost in older embryos. 7. In all combinations tested, there appear goblet cells in the epithelium when the explants are cultured more than 10 days. These cells are never observed in intact oesophagus, proventriculus and gizzard, whether in normal development or in culture.