We will
evaluate the evidence for a QGP phase in heavy-ion collisions where
quark and gluon degrees-of-freedom are manifest over a volume much
larger than a typical hadron. We focus on indications for constituent-quark
degrees-of-freedom in identified particle spectra and elliptic flow.
High statistics elliptic flow measurements from RHIC Run IV will
be used to test constituent-quark-number scaling relations. These
relations and the models that predict them suggest that the hadron
formation process encodes information in identified particle spectra
about a QGP phase.