  We discuss the near-infrared properties of the nuclei in the 11 merging
galaxies of the Toomre sequence, based on high spatial resolution J, H, and K
imaging data using NICMOS onboard the Hubble Space Telescope (HST). The
observations are less affected by dust extinction than our previous HST/WFPC2
observations and offer higher spatial resolution than existing ground-based
near-IR data. We see a marginal trend for the nuclei to become bluer with
advancing merger stage, which we attribute to a dispersal of dust at late times
in the merging process. Our data also indicate a statistically significant
trend for the nuclei in the sequence to become more luminous, within an
aperture of fixed physical size and after correcting for dust extinction, with
advancing merger stage. We derive K-band surface brightness profiles for those
nuclei for which the morphology allows a meaningful isophotal analysis, and fit
the profiles with a ``Nuker law'' for comparison with other samples of galaxies
observed with HST. The majority of the nuclei have steep profiles that can be
characterized as power-law type. In general, the Toomre sequence galaxies tend
to have steeper profiles and higher central luminosity surface densities than
E/S0's. We derive V-K color profiles for the nuclei to further address this
possibility, but find that the large amounts of dust extinction complicate
their interpretation. Overall, our results are consistent with the generic
predictions of N-body simulations of spiral galaxy mergers. If left to evolve
and fade for several Gyrs, it is possible that the properties of the Toomre
sequence nuclei would resemble theproperties of the nuclei of normal E/S0
galaxies. Our results therefore support the view that mergers of spiral
galaxies can lead to the formation of early-type galaxies (Abridged).
