  I review recent observational progress concerning the evolution of the
morphological distribution of galaxies in the rich cluster environment and in
the faint field population. By coupling HST imagery with ground-based
spectroscopic diagnostics, evidence accumulates that galaxy morphology can be a
transient phenomenon reflecting various changes in the star formation rate.
Possible physical processes responsible for these changes are discussed. Future
progress in understanding them will depend on securing 2-D spectroscopic data
for representative systems.
