  We investigate the star-formation in cometary tails of galaxies in clusters.
In particular, we focus on the evolution of molecular clouds in the tails that
generate the stars. Assuming that the gas tails had been derived from the
galaxies through ram-pressure stripping, we found that the gas must have been
stripped mostly not in the form of molecular clouds, but in the form of HI gas
or molecular gas that is not in clouds. Moreover, the molecular clouds are
condensed in the tails even away from the host galaxies. We also found that
magnetic fields may be required to suppress Kelvin-Helmholtz (KH) instability
on the surface of molecular clouds, because otherwise KH instability may
destroy the molecular clouds before stars are formed in them.
