Yang effect in multiparticle hadron production at the HERA collider

It is argued that the mean multiplicities in a deep-inelastic process that are measured at the HERA collider grow with increasing photon virtuality at a fixed invariant mass of final hadron states. This is yet another piece of experimental evidence in favor of the qualitative hypothesis put forth by C.N. Yang and his colleagues and of the quantitative predictions obtained by the present authors on the basis of QCD.