  Despite their apparent fragile appearance, dwarf spheroidals are the most
common galaxy type in clusters. In this paper we consider some of the issues
associated with two major models for the origin of these dwarfs: primeval
galaxies which formed with the cluster and the modification of accreted
systems. We argue that the present observational evidence, derived from the
Virgo and Perseus clusters, points to infall as the origin of many of these
objects.
