We revisit Nambu's model of quark confinement by a tube of magnetic flux,
with two additional features. The quarks are taken to be magnetic monopoles
external to the tube, which seal the ends, and are also taken to be fermions.
This ensures that the model is inconsistent unless there are at least two
species of fermions being confined.Comment: 7pp; brief additions relating monopole strength to winding number,
and discussion on length of stable flux tube; one reference adde