  Analytical estimates of the mass and radial dependence of the rates of galaxy
mergers and of tidal interactions are derived for clusters and groups of
galaxies, taking into account the tides from the system potential that limit
the sizes of galaxies. Only high mass galaxies undergo significant major
merging before being themselves cannibalized by more massive galaxies. Strong
tides from the group/cluster potential severely limit the merger/tide
cross-sections in the central regions, and while tides are most efficient at
the periphery, one should see merging encounters further inside rich clusters.
