Fig. 4. Effects of the bilateral ablation of the Q lineage on the cleavage patterns of o/p blast cell clones in stage 8 embryos. (A,B) Cleavage pattern of the presumptive o bandlet (A) and the presumptive p bandlet (B) of H. robusta (Austin) shown by Hoechst 33258 nuclear staining. Presumptive o blast cell clones express the normal O-type cleavage pattern. The o.p nuclei are marked with red arrows. Most presumptive p blast cell clones express a normal P-type cleavage pattern, and white lines mark the p.a and p.p daughter cell pairs. A few presumptive p blast cell clones express an O-type cleavage pattern (yellow arrows). (C,D) Ablation of bilateral Q lineages causes both o/p bandlets to express the O-type cleavage pattern in H. robusta (Sacramento) (C) and Helobdella sp. (Galt) (D). The small nuclei of o.p cells in the presumptive o bandlet are labeled with red arrows, and the nuclei of ectopic o.p cells in the presumptive p bandlet are labeled with yellow arrows. See Fig. 2 for orientation. Scale bar: 20 µm.