  The smallness and hierarchy of the fermion parameters could be explained in
theories with extra dimensions where doublets and singlets are localized at
slightly separated points. Scattering cross sections for collisions of such
fermions vanish exponentially at energies high enough to probe the separation
distance. This is because the separation puts a lower bound on the attainable
impact parameter in the collision. The NLC, and in particular the combination
of the e^+e^- and e^-e^- modes, can probe this scenario, even if the inverse
fermion separation is of order tens of TeVs.
