  We analyse the population of bright star clusters in the interacting galaxy
pair NGC 4038/39 detected with HST WFPC1 by Whitmore & Schweizer (1995) using
our spectrophotometric evolutionary synthesis models for various initial
metallicities. We derive individual ages for all clusters with V-I colour and
follow the time evolution of their luminosity function (LF). The age
distribution clearly reveals the presence of a number of old Globular Clusters
(GCs) from the parent galaxies. Their effective radii do not significantly
differ from those of the young star cluster population. We confirm Meurer's
(1995) conjecture that the shape of the LF changes in the course of evolution
if age spread effects are accounted for. We find that over a Hubble time the
observed exponential LF of the young star clusters will evolve into a typical
Gaussian GCLF with parameters M$_{V_0} = -7.1$ mag and $\sigma (M_{V_0}) = 1.3$
mag. We discuss the influence of metallicity, the effects of an inhomogeneous
internal dust distribution, as well as the possible influence of internal --
through stellar mass loss -- and external dynamical effects on the secular
evolution of the LF. Referring YSC luminosities to a uniform age and combining
with model M/L, we recover the intrinsic mass distribution of the YSC system.
It is Gaussian in shape to good approximation thus representing a
quasi-equilibrium distribution that $-$ according to Vesperini's (1997)
dynamical modelling for the Milky Way GC system $-$ will not be altered in
shape over a Hubble time of dynamical evolution, allthough a substantial number
of clusters will be destroyed. Comparing young star cluster populations in an
age sequence of interacting/merged and merger remnant galaxies will directly
reveal the role of external dynamical effects.
