  Variations in the number of globular clusters per unit galaxy luminosity,
which is the specific frequency, and the mass of globular clusters per unit
total available mass, are reviewed. Correlations with galaxy luminosity and
morphology, and with the properties of the associated galactic clusters are
discussed, as are the color distributions of globular cluster populations.
Several models for the origin of these variations are summarized, including the
tidal stripping and interaction/starburst models. Most of the variations in the
specific frequency for elliptical galaxies result from variations in the ratio
of total mass to light with a nearly constant efficiency for conversion of gas
into globular cluster mass. Smaller additional variations may come from tidal
stripping, particularly in cD galaxies.
