  The relevance of the pseudospin symmetry in nuclei is considered. New insight
is obtained from looking at the continuous transition from a model satisfying
the spin symmetry to another one satisfying the pseudospin symmetry. This study
suggests that there are models allowing no missing single-particle states in
this transition, contrary to what is usually advocated. It rather points out to
an association of pseudospin partners different from the one usually assumed,
together with a strong violation of the corresponding symmetry. A comparison
with results obtained from some relativistic approaches is made.
