Fig. 4. Specificity of labeling technique. (A) Superimposed bright field and fluorescence image immediately post-injection of a stage 4+ embryo, ventral side upwards, injected with DiO (green). (B-1,B-2) 150 µm section at the level shown in A (x100). Because of the thickness of the section, B-1 shows an image where the ectoderm and mesoderm layer are in focus and B-2 shows the mesoderm and endoderm in focus. (C) 150 µm section at the level shown in A (x200). The arrow denotes the location of the primitive groove. Ec, ectoderm; En, endoderm.