  We derive ages, metallicities and [alpha/Fe] ratios from the integrated
spectra of 23 globular clusters in M31, by employing multivariate fits to two
stellar population models. In parallel we analyze spectra of 21 Galactic
globular clusters in order to facilitate a differential analysis. We find that
the M31 globular clusters separate into three distinct components in age and
metallicity. We identify an old, metal-poor group (7 clusters), an old,
metal-rich group (10 clusters) and an intermediate age (3-6 Gyr),
intermediate-metallicity ([Z/H]~-1) group (6 clusters). This third group is not
identified in the Galactic globular cluster sample. The majority of globular
clusters in both samples appear to be enhanced in alpha-elements, the degree of
enhancement being model-dependent. The intermediate age GCs appear to be the
most enhanced, with [alpha/Fe]~0.4. These clusters are clearly depressed in CN
with respect to the models and the bulk of the M31 and Milky Way sample.
Compared to the bulge of M31, M32 and NGC 205, these clusters most resemble the
stellar populations in NGC 205 in terms of age, metallicity and CN abundance.
We infer horizontal branch morphologies for the M31 clusters using the Rose
(1984) Ca II index, and demonstrate that blue horizontal branches are not
leading to erroneous age estimates in our analysis. The intermediate age
clusters have generally higher velocities than the bulk of the M31 cluster
population. Spatially, three of these clusters are projected onto the bulge
region, the remaining three are distributed at large radii. We discuss these
objects within the context of the build-up of the M31 halo, and suggest that
these clusters possibly originated in a gas-rich dwarf galaxy, which may or may
not be presently observable in M31.
