Fig. 8.

CaP and the muscle pioneers may regulate retraction of the MiP ventral process. Side view of an MiP labeled intracellularly after muscle pioneer and CaP ablation and viewed in the living embryo at two time points. A, At 24 h MiP had a ventral process (arrow) that extended beyond the distal limit of the common pathway (broken line) and did not have a dorsal collateral (see control MiP) (Fig. 7A). Ectopic branches were present in 17 of 41 experimental segments at 24 h. B, At 48 hr most of the ventral process was still present, and ectopic branches (arrows) had sprouted from it, although a normal dorsal process had formed. The extent of the dorsal projection was normal, although the entire extent is not shown here. Ectopic branches were present in 6 of 16 experimental segments at 48 h. Scale bar, 10 μm.