  Our 2dF Fornax Cluster Spectroscopic Survey (FCSS) and follow-up work in the
Virgo Cluster have shown that the cores of both galaxy clusters contain a
previously-unknown class of object, ultra-compact dwarf (UCD) galaxies. We
present high resolution spectroscopy and deep multicolour imaging to show that
these enigmatic objects are dynamically distinct from both globular clusters
(GCs) and nucleated dwarf galaxies (dE,Ns). Our hypothesis for their origin may
explain the observed high ``specific frequency'' of GCs in central cluster
galaxies.
