In seq^SH1898 mutant homozygous clones, a large proportion of R7 cells terminate their axon projections in the outer M1-M3 layers, rather than in the M6 layer. seq^SH1898 mutant R8 axons frequently stop above their prospective M3 target layer. When homozygous seq^SH1898 mutant clones are induced specifically in the R7 cells, almost all of the R7 axons stop prematurely in M3, even when surrounded by heterozygous R8 and R7 axons.