Fig. 10. A diagram showing the deduced regulatory interactions within the labial disc. The peripodial stalk is to the left and the anatomically distal portion of the disc to the right. The portion of the disc expressing both Pb and Scr is shaded in gray. The broken vertical line separates the most proximal region from the distal region in which most of the mutant effects of pb and Scr were observed. The lines with bars at the end indicate a negative or suppressive interaction, while arrows indicate a positive or inductive interaction. The broken lines indicate uncertainty about the indicated interaction. The width of the arrows indicates the strength of the interaction.