  We review both the counting rule and the influence of the evolution in $Q^2$
for the large $x_{Bj}$ behaviour of the valance quark distribution functions.
Based on a factorization procedure we present a more general perturbative
treatment to compute this behaviour. A complete analysis is performed in the
scalar $\phi^3_{[6]}$-theory for the parton distribution function of the
``meson'', which shows that logarithmical corrections arise from the
distribution amplitude and that the reference momentum square $Q_0^2$ is fixed
by $x_{Bj}$.
