Mosaic and Regulation Phenomena during the Early Formation of the Chick Blastoderm
Figure 10
(a): Schematic representation of the surgical removal of the right half of the endophyll-Rauber’s sickle (RS) complex of an unincubated chicken blastoderm. The top of the sickle horns (SH) is fragmentary (in green) and cannot always be distinguished. AS, anti-sickle region; CMZ, caudal marginal zone; CGW, caudal germ wall; L, left of the blastoderm; the red arrow indicates where the symmetrically formed primitive streak will appear after incubation. (b): Removal of the endophyll-Rauber’s sickle complex at the right side as represented in Figure 10(a), at the start of the culture period. A graphite particle, indicated by white arrowhead, is placed in the middle region where Rauber’s sickle is sectioned. E: half left endophyll sheet; Bar = 2 mm. (c): The same blastoderm as seen in Figure 10(b) after 5 hours of culture; a darker linear area has appeared at the operated side. Bar = 2 mm. (d): The same blastoderm as seen in Figure 10(c) after 9 hours of culture. A primitive streak (indicated by arrowhead) starting from the graphite particle is localized in a clearer area (a realization) and is directed to the unoperated side. Bar = 2 mm.
