  The main problem of clone theory is to describe the clone lattice for a given
basic set. For a two-element basic set this was resolved by E.L. Post, but for
at least three-element basic set the full structure of the lattice is still
unknown, and the complete description in general is considered to be hopeless.
Therefore, it is studied by its substructures and its approximations. One of
the possible directions is to examine $k$-ary parts of the clones and their
mutual inclusions. In this paper we study $k$-ary parts of maximal clones, for
$k\geq2$, building on the already known results for their unary parts. It turns
out that the poset of $k$-ary parts of maximal clones defined by central
relations contains long chains.
