||P.1270 right column bottom paragraph: "Histoblasts. At the compartment border, P compartment histoblasts generated protrusions that reached anteriorly into the A compartment, covering most of the Ptc-promoter–trap::GFP gradient (Fig. 4b,c and Supplementary Videos S1 and S2). [Investigators] observed both a dense array of shorter protrusions (about 17 μm, 4 cell diameters) and individual longer protrusions (about 40 μm, ∼ 9 cell diameters). These protrusions could also be observed by labelling the actin cytoskeleton with Utrophin–GFP (ref. 36 Supplementary Fig. S1c,d). In contrast to P compartment histoblasts, A compartment histoblasts rarely sent shorter cytonemes posteriorly into the P compartment (Fig. 4d and Supplementary Video S3)."