Fig. 7. Mesoderm is required in the Q lineage-independent O/P specification pathway in H. robusta (Austin). (A) Ipsilateral o/p bandlets in stage 8 embryo in which both the M and Q lineages were ablated. Both bandlets exhibit the O-type cleavage pattern, with the small o.p nuclei marked by arrows. The presumptive p bandlet has transfated to the O-type cleavage pattern, and is labeled o'. (B) Ipsilateral o/p bandlets in stage 8 embryo in which only the M lineage was ablated. The presumptive o bandlet expresses the O-type cleavage pattern, while the presumptive p bandlet expresses the P-type cleavage pattern. See Fig. 2 for orientation. Scale bar: 30 µm.