  We deal with a degenerate model in divergence form describing the dynamics of
a population depending on time, on age and on space. We assume that the
degeneracy occurs in the interior of the spatial domain and we focus on null
controllability. To this aim, first we prove Carleman estimates for the
associated adjoint problem, then, via cut off functions, we prove the existence
of a null control function localized in the interior of the space domain. We
consider two cases: either the control region contains the degeneracy point
$x_0$, or the control region is the union of two intervals each of them lying
on one side of $x_0$. This paper complement some previous results, concluding
the study of the subject.
