  Several macrolensed systems exhibit photometric variability consistent with
microlensing due to objects of stellar mass located in the lens. The degree of
microlensing amplification is dependent upon the size of the source, with
smaller sources being more amplified. In general, amplification of sources
larger than an Einstein radius projected onto the source plane is negligible.
For the quasar Q2237+0305, a quadrupole image lens (Huchra et al., 1985), this
radius is 0.05 pc, larger than the predicted size of a continuum emitting
accretion disk, but substantially smaller than the broad line region (Figure
1). This scale difference implies that the continuum will be amplified while
the broad line emission remains essentially unchanged during a microlensing
event (Sanitt, 1971; Kayser et al., 1986).
  The broad line emitting region, as a whole, is too large to be microlensed,
but substructure on small scales may be significantly amplified. Although the
total flux in the line is relatively unchanged, microlensing of substructure
can result in changes in the shape of the emission line profiles, and produce
measurable shifts in the central wavelength of the line (Nemiroff, 1988;
Schneider and Wambsganss, 1990).
