Fig. 12. Effect of D₂O and nocodazole on microtubule density near the embryo surface. Wholemount confocal microscopy of embryos stained for ß-tubulin. (A) Furrow region of untreated cleaving embryo. (B) The same embryo, non-furrowing surface of animal hemisphere. Inset is vertical resection at the site indicated by the white horizontal line. (C) Animal surface of D₂O-treated embryo, showing through-surface view of a microtubule monaster. The inset is a vertical resection that indicates monastral microtubules are within 1 or 2 µm of the surface. (D) Nocodazole treatment completely eliminates surface microtubules. (E) Nocodazole treatment eliminates surface microtubules in a D₂O-incubated embryo. Bar, 10 µm.