The Casimir energy or stress due to modes in a D-dimensional volume su
bject to TM (mixed) boundary conditions on a bounding spherical surfac
e is calculated. Both interior and exterior modes are included. Togeth
er with earlier results found for scalar modes (TE modes), this gives
the Casimir effect for fluctuating ''electromagnetic'' (vector) fields
inside and outside a spherical shell. Known results for three dimensi
ons, first found by Boyer, are reproduced. Qualitatively, the results
for TM modes are similar to those for scalar modes: Poles occur in the
stress at positive even dimensions, and cusps (logarithmic singularit
ies) occur for integer dimensions D less than or equal to 1. Particula
r attention is given the interesting case of D = 2.