  We present new results of a program to study the detailed morphologies of
galaxies in intermediate redshift clusters and hence understand the physical
origin of the enhanced star formation in these environments at earlier epochs.
Deep, high resolution imagery has been obtained of 3 rich clusters, AC103,AC118
& AC114 at z=0.31, using the WFPC2 on HST. For AC103 & AC118, single pointings
covering a central 0.5x0.5Mpc have been obtained; for AC114, 4 pointings
covering a 1.2x0.7Mpc area have been obtained, allowing the more outer regions
of a distant cluster to be studied. Hubble types plus evidence for dynamical
interactions and/or structural abnormalities have been determined visually for
all galaxies down to R=22.25 in AC103 & AC118 and R=23.0 in AC114.We find the
numbers of spirals (Sa-Sdm) in our clusters to be up to 4x higher than that
seen in present-day clusters; only in the virialised core of our most massive
regular cluster, AC114, do we see morphological fractions approaching those of
the present epoch. Dynamical interactions are also widespread throughout the
clusters with ~20% of members showing morphological evidence of this
phenomenon. The highest incidence is amongst those blue members either
undergoing a starburst or seen <0.5Gyr thereafter with the majority being
involved in major mergers. These galaxies, however, are of modest luminosity
(L~L*+1mag), destined to become dwarfs once they fade. Cluster members with
ongoing star formation typical of nearby spirals are largely late Sb-Sdm Hubble
types. Galaxies whose star formation ended 1-2Gyr prior to the epoch of
observation are all normal early-type (S0-Sb) disk systems. The red H-delta
strong galaxies are a mixture of E & S0 galaxies, consistent with them being
old dormant systems which have undergone a secondary star formation episode.
