  We consider the transformation properties of fermions under the discrete
symmetries CPT, CP, and C in the presence of B-L violation. We thus generalize
the analysis of the known properties of Majorana neutrinos, probed via
neutrinoless double beta decay, to include the case of Dirac fermions with B-L
violation, which can be probed via neutron-antineutron oscillations. We show
that the resulting CPT phase has implications for the interplay of
neutron-antineutron oscillations with external fields and sources and consider
the differences in the Majorana dynamics of neutrinos and neutrons in the
context of theories with self-conjugate isospin I=0 and I=1/2 fields.
