Fig. 4. The simultaneous loss of Dpp and N signalling does not prevent the initiation of Atonal expression. All clones are marked by the absence of ß-galactosidase (green), Atonal is stained in red. (A-C,G-I) medea mutant clones. (D-F,J-L) med Dl double mutant clones. (A,G) In med clones Atonal expression is reduced (white arrow) or occasionally absent (arrowhead). (B,H) Some med clones posterior to the morphogenetic furrow ectopically express Atonal (white arrowhead). (C,I) med clones along the posterior eye margin prevent the initialisation of morphogenetic furrow. (D,J) Double mutant clones of med⁸ Dl^rev10 express Atonal at low levels. (E,K) Occasionally posterior med⁸ Dl^rev10 double clones ectopically express Atonal in a cluster of cells (arrowhead in K); note the difference between this and clones of med alone, where the ectopic expression is in isolated cells (compare K with H). (F,L) In some med⁸ Dl^rev10 double clones there are regions where Atonal expression is totally lost (white arrow in L), a phenotype also observed in med clones (white arrowheads in A and G).