  We present a study of globular clusters (GCs) in 17 relatively nearby
early-type galaxies, based on deep HST/WFPC2 F555W and F814W images. We compare
color distributions, cluster sizes and luminosity functions with those of GCs
in the Milky Way. In nearly all cases, a KMM test returns a high confidence
level for the hypothesis that a sum of two Gaussians provides a better fit to
the observed color distribution than a single Gaussian, although histograms of
the V-I distribution are not always obviously bimodal. The blue and red peak
colors both correlate with absolute host galaxy B band magnitude and central
velocity dispersion (at about the 2-3 sigma level), but we see no clear
correlation with host galaxy V-I or J-K color. Red GCs are generally smaller
than blue GCs by about 20%. The size difference is seen at all radii and exists
also in the Milky Way and Sombrero (M104) spiral galaxies. Fitting t5 functions
to the luminosity functions of blue and red GC populations separately, we find
that the V-band turn-over of the blue GCs is generally brighter than that of
the red ones by about 0.3 mag, as expected if the two GC populations have
similar ages and mass distributions but different metallicities. Brighter than
M_V ~ -7.5, the luminosity functions (LFs) are well approximated by power-laws
with an exponent of about -1.75. This is similar to the LF for young star
clusters, suggesting that young and old globular clusters form by the same
basic mechanism. We discuss scenarios for GC formation and conclude that our
data appear to favor ``in-situ'' models in which all GCs in a galaxy formed
after the main body of the proto-galaxy had assembled into a single potential
well.
