  The nuclear-polarization (NP) energies with the collective model commonly
employed in the NP calculations for hydrogenlike heavy ions are found to have
serious gauge violations when the ladder and cross diagrams only are taken into
account. Using the equivalence of charge-current density with a schematic
microscopic model, the NP energy shifts with the collective model are gauge
invariantly evaluated for the $1s_{1/2}$ states in $^{208}_{~82}$Pb$^{81+}$ and
$^{238}_{~92}$U$^{91+}$.
