N^Ax-E1/+ females at 20.5^oC have gaps in wing veins and a reduction in number of ocellar and postvertical bristles. Semilethal as hemizygote or homozygote. Heterozygotes N^Ax-E1/N^Ax-9 are viable and phenotypically intermediate: N^Ax-E1/N^Ax-E2 and N^Ax-E1/N^Ax-16 are inviable (negative heterosis). N^Ax-E1 is inviable with most N mutants, but heterozygotes with N^264-103 (a temperature-sensitive mutant) survive at 22^oC but not at 29^oC. On the map of Notch to the right of N^nd-3 and probably close to spl based on failure to obtain recombinants between N^Ax-E1 and spl.