Data are presented which strongly indicate that the locus occupied by the mutant w^z lies to the left of, or on the same locus of apricot (w^a). The fact that w^z shows a non-suppressor effect in combination with zeste as a typical phenomenon in mutants of sites 1, 2, and 3 of the white locus, also supports that w^z is a mutant at or left of apricot (site 3). A "model" for the genetic fine structure of the mutants (w^zm, w^zl, and w^z) is proposed and discussed to account for the mutability among those three mutants. Analysis of w^z leads to the hypothesis that it is the result of an inversion (sites 3 and 4) at the white locus, by two mechanisms which are discussed briefly here.