Are diffractive events at HERA due to a gluemoron or a quarkball?

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 single system can be interpreted as gluonic.