  We propose a means of distinguishing between gluon- and quark-seeded systems
that may in principle be measured in deep inelastic lepton scattering. As a
particular application, we discuss those HERA data on deep inelastic $ep$
scattering which contain a large rapidity gap in the final state. It is
standard to interpret these events as being due to ``pomeron" exchange,
although precisely what is meant by this remains unclear. Guided by data, we
make some rather general statements about these events and in particular we
discuss the potential for discerning whether the exchanged colour singlet
system can be interpreted as gluonic.
