Fig. 1. Early cleavages and POP-1 asymmetry. Schematic diagram of normal and devitellinized embryos from first cleavage to the AB⁸ stage; anterior is left in all drawings. Descendants of AB are shown in blue and descendants of EMS are shown in yellow. Sister cells are connected by short black lines. For some cells, the axis of the subsequent division is shown with either a double-headed arrow (division within the plane) or an asterisk (divisions into the plane). At the AB⁸ stage, levels of POP-1 are indicated as high (white nuclei) or low (black nuclei). Note that POP-1 polarity is reversed in the P₂ daughters of devitellinized embryos. Red, blue and yellow arrows on devitellinized embryos indicate positions of graft cells described in the text.