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

Figure 4

Section (plane indicated in Figure 2) through a chicken hemi-embryo cultured during 1 day. The arrowhead indicates a hemi-primitive groove in which upper layer cells ingress into the hemi-primitive streak, giving rise to a mesoblast mantle (M) which slides peripherally between the junctional endoblast (JE) and the epiblast (E); sickle endoblast (S); double-arrowed line indicates the surface of the thickened hemi-PS-forming upper layer. Hematoxylin eosin, bar = 50 𝜇m.