Fig. 1. Expression of ß-galactosidase in embryos injected at the one-cell stage. Two representative embryos, 1-5 (A-D) and 1-4 (E-H) are shown. (A,E) Whole mounts and (B-D,F-H) Hematoxylin and Eosin-stained sections. Almost all parts of the embryos were positive for X-gal staining (A,B,E-F). (C,D,G,H) Higher magnifications of B and F respectively. (H) Derivatives of primitive endoderm (arrows) did not show X-gal staining. Scale bars: 300 µm (A,E), 150 µm (B,F), 30 µm (C,G).