  We report on the properties of nuclear regions in the Toomre Sequence of
merging galaxies, based on imaging data gathered with the Hubble Space
Telescope WFPC2 camera. We have imaged the 11 systems in the proposed
evolutionary merger sequence in the F555W and F814W broad-band filters, and in
H-alpha+[NII] narrow-band filters. The broad-band morphology of the nuclear
regions varies from non-nucleated starburst clumps through dust-covered nuclei
to a nucleated morphology. There is no unambiguous trend in the morphology with
merger stage. The emission-line morphology is extended beyond the nucleus in
most cases, but centrally concentrated (within 1 kpc) emission-line gas can be
seen in the four latest-stage merger systems. We have quantified the intrinsic
luminosity densities and colors within the inner 100 pc and 1 kpc of each
identified nucleus. We find little evidence for a clear trend in nuclear
properties along the merger sequence, other than a suggestive rise in the
nuclear luminosity density in the most evolved members of the sequence. The
lack of clear trends in nuclear properties is likely due both to the effects of
obscuration and geometry, as well as the physical variety of galaxies included
in the Toomre Sequence.
