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We argue that individual images in multiple-image QSOs could easily havesubstructure at the level of $0.1''$ (i.e., unresolvable even with HST);microlensing within such substructure would cause centroid shifts, observableeven from the ground as pseudo proper motions. We present a model of thefour-image system 2237+0305 in which Image B shows such ``improper motions" oforder of $0.01''$ over a few years.Comment: 16 pages, uuencoded, to appear in the Astronomical Journa

Improper Motions in Lensed QSOs