  The momentum distributions of partons in bound nucleons are known to depend
significantly on the size of the nucleus. The Fourier transform of the momentum
($\xbj$) distribution measures the overlap between Fock components of the
nucleon wave function which differ by a displacement of one parton along the
light cone. The magnitude of the overlap thus determines the average range of
mobility of the parton in the nucleon. By comparing the Fourier transforms of
structure functions for several nuclei we study the dependence of quark
mobility on nuclear size. We find a surprisingly small nuclear dependence
($<2\%$ for He, C and Ca) for displacements $t=z \lsim 2.5$ fm, after which a
nuclear suppression due to shadowing sets in. The nuclear effects observed in
momentum space for \mbox{$\xbj \lsim 0.4$} can be understood as a reflection of
only the large distance shadowing in coordinate space.
