Figure 6.

Lineage tracing experiments in cleavage-arrested embryos show that e1 micromeres give rise to the comb-cells. DIC images of cleavage-arrested embryos with DiI-labeling shown in red. White arrows point to labeled comb plates and black arrows point to unlabeled comb plates. The diagrams in the lower left corners show the stage when the embryo was inhibited with cytochalasin B and the appropriate DiI-labeled cells. (A, B, C) All four E macromeres were labeled at the 8-cell stage and the embryos were arrested at the 16-cell stage. Only labeled cells have combs. (D) All four M macromeres were labeled at the 8-cell stage and the embryos were arrested at the 16-cell stage. Only unlabeled cells form combs. (E) All four e₁ micromeres were labeled and the embryos were arrested at the 16-cell stage. All comb cells are labeled. (F, F'') Part of an embryo that was arrested at the 16-cell stage. All E macromeres are labeled. (F) is a DIC image. (F') is the red channel and (F'') shows both images merged. The comb cell is clearly labeled. (G, G', G'') The embryo was arrested at the 16-cell stage. All four M macromeres are labeled. (G) is the DIC image and (G') the red channel. (G'') shows both images merged. All comb cells are unlabeled.