  We argue that individual images in multiple-image QSOs could easily have
substructure at the level of $0.1''$ (i.e., unresolvable even with HST);
microlensing within such substructure would cause centroid shifts, observable
even from the ground as pseudo proper motions. We present a model of the
four-image system 2237+0305 in which Image B shows such ``improper motions" of
order of $0.01''$ over a few years.
