Geometric scaling in a symmetric saturation model

We illustrate geometric scaling for the photon-proton cross section with a very simple saturation model. We describe the proton structure function (Formula presented) at small x in a wide kinematical range with an elementary functional form and a small number of free parameters. We speculate that the symmetry between low and high (Formula presented) recently discovered in the data could be related to a well-known symmetry of the two-gluon-exchange dipole-dipole cross section.