Mosaic and Regulation Phenomena during the Early Formation of the Chick Blastoderm
(a): In toto Unna stained (after fixation) blastoderm, operated as represented in Figure 10(a), after 29 hours of culture. An apparently normal embryo proper has developed symmetrically. At the operated side (O), only a few blood islands in a narrow area vasculosa are seen, and in the area vitellina an empty region (*) is visible. In the unoperated side, a larger normal area vasculosa (AV) is seen with numerous blood islands (black arrows). Bar = 2 mm. (b): Section through the embryo of Figure 11(a) (plane of section is indicated in Figure 11(a) as a blue line). G, intraembryonic cavity closed at the operated side (indicated by the arrowhead directed upwards) contains no mesoblast. In the unoperated side, the intraembryonic cavity (G) extends far peripherally. It contains a mesoblast mantle which laterally forms blood islands close to the endoderm (E) which are domed by coelomic vesicles (indicated by 2 arrowheads directed downwards). Bar = 100 m.
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