  The structure of the electromagnetic vertex of spin-1 particles are studied
in a general way, for the diagonal as well as the off-diagonal couplings. In
each case, we consider in detail the consequences of gauge invariance and the
space-time discrete symmetries, paying particular attention to the implications
for the couplings of the photon to neutral gauge bosons, which arise in higher
orders. Several general results concerning the static electromagnetic
properties of neutral bosons are derived, analogous to the results that are
well known in the case of neutral spin-1/2 particles.
