Mosaic and Regulation Phenomena during the Early Formation of the Chick Blastoderm

Figure 12

Section through a similar blastoderm as described in Figure 10(a), after 34 hours of culture. In the operated side (at the right of the figure), a mesoblast mantle is present in the intraembryonic cavity (G), which is closed as the result of the absence of junctional endoblast at that side. No blood islands and no coelomic cavity are formed. At the unoperated side, the intraembryonic cavity (G) is not interrupted laterally and contains blood islands close to the deep layer. Part of the coelomic cavity is visible (hemi-pericardial cavity: P) with unilateral primary heart anlage (H) in the neighbourhood of the infolding gut endoderm, laterally from the closing anterior intestinal portal (AIP). S, somites; arrowhead indicates intermediary mesoderm (nephrotome). Bar = 100 𝜇m.