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Fig. 8 Relationship of sna-1 and ntl expression in wild-type (C-H) and ntl mutant (A,B) embryos investigated by sna-1 in situ (blue) and anti-Ntl antibody (brown) double stainings. All embryos were spread. (A,D) Germ ring stage, dorsal view: (A) ntl, (D) wild-type. (C) Section through germ ring of germ ring-stage embryo, lateral position. The border of the embryo and the separation of epiblast and hypoblast are outlined by dots. (B,E) 60% epiboly, dorsal view: (B) ntl, (E) wild type. (F) 80% epiboly, dorsal view.(G) 95% epiboly, dorsal view. (H) 4-somite stage, dorsal view. For details see text. Arrows in E and F indicate the ‘forerunning’ cells, a group of sna-1- negative and ntl-positive cells located on the yolk posterior to the germ ring at the dorsal midline of the embryo.