Fig. 5. R-cell determination in Delta and lqf-null eye disc clones. Confocal images of eye discs are shown. Anterior is upwards in all panels and the arrows indicate the position of the furrow. The discs contain Delta^rev10 clones (A,A',B,B') or lqf ^ARI clones (C,C',D,D') marked by the absence of GFP. The discs are labeled with anti-Elav in (A,A',C,C') and with anti-Boss in (B,B',D,D'). In A-D, the clone borders are outlined. The Elav and Boss-expressing cells can be seen several cell distances in from the edge of the clone. This is probably due to long-range Delta signaling, a phenomenon that is not well understood (De Joussineau et al., 2003). Scale bar: 10 µm.