In an earlier paper the first named authors investigated rings whose k
ernel functors are linearly ordered. The main tool for describing prop
erties of such rings was the filter of ideals associated to a kernel f
unctor. In the present paper more generally closed module categories (
i.e. closed under kernels, cokernels and direct sum) with linearly ord
ered closed sub-categories are studied. Properties of these categories
are given and they are characterized by conditions on special objects
, i.e. cogenerators or generators.