Fig. 6. Control of MS ingression. All panels are ventral views of embryos after ingression by the MS wishbone descendants; the MS central descendants are indicated by asterisks. The central descendants remain on the surface in (A) a normal embryo, (B) an embryo after ablation of the E blastomere (dotted outline) and (C) a temperature-shifted lit-1 mutant embryo. (D) The central descendants ingress (arrow) along with the wishbone descendants in a temperature-shifted lit-1 mutant embryo after ablation of the E blastomere (dotted outline). The lit-1 chromosome was marked with an unc-32 mutation; the embryo shown in B is a temperature-shifted unc-32 control.