  A geometrical model of hadron-proton interactions has been extended to
describe gamma-proton total cross section measured in deep-inelastic scattering
at small x (x<0.04). Experimental data are consistent with this model assuming
that the hadronic fluctuation of the virtual photon has a size of <r^2> ~
1/(4m_q^2 + Q^2), where m_q is the mass of the light constituent quark.
