ONE FIGUREDuring the past two decades a considerable literature has accumulated concerning the vestigial locus of Drosophila melaanogaster (Goldschmidt ; Harnly ; Hersh and Ward; Li and Tsui; Mohr; Stanley; etc.). I n the early papers marked differences in the temperature response curves of the different genotypes precluded the advancing of any general theory on the nature of gene action at the vestigial locus. With the accumulation of temperature and sex dimorphic response data on more genotypes of this locus it has become apparent that there are two distinct mechanisms involved affecting: (1) the size of any wing part present and ( 2 ) the shape or form of the wing, i.e., parts present or absent. This paper demonstrates that the gene complexes of size of wing parts and the number of parts present are independent in their operation during development. The proof of this fact makes possible a forthcoming general theory of the action of the vestigial a1,leles (Harnly, '51).
MATERIALS AND METHODSThe genes used in this report and their symbols are: Wildtype or normal allele (vg+), vestigial (vg), vestigial-pennant (vgp), vestigial-Depilate ( vgD), and dimorphos (di) . The changes in phenotype through the viable temperature range 0 ,