  Far-infrared flux densities are newly extracted from the IRAS database for
the RSA and CfA complete samples of Seyfert galaxies. These data are used to
classify the Seyfert galaxies into those where the far-infrared continuum
emission is dominated by the active galactic nucleus (AGN), circumnuclear
starburst, or host galaxy.
  While AGN-dominant objects consist of comparable numbers of Seyfert 1 and 2
galaxies, starburst- and host-dominant objects consist preferentially of
Seyfert 2 galaxies. Thus, in addition to the dusty torus, the circumnuclear
starburst region and host galaxy are important in hiding the broad-line region.
  Morphologically, starburst-dominant Seyfert galaxies are of later types and
more strongly interacting than AGN-dominant Seyfert galaxies. In a later-type
galaxy, the AGN central engine has a lower Eddington luminosity, and the
gaseous content is higher. The gas is efficiently supplied to the starburst via
a galaxy-galaxy interaction. Morphologies of host-dominant Seyfert galaxies are
of various types.
  Since starbursts in Seyfert galaxies are older than those in classical
starburst galaxies, we propose an evolution from starburst to
starburst-dominant Seyfert to host-dominant Seyfert for a late-type galaxy. An
evolution from AGN-dominant Seyfert to host-dominant Seyfert is proposed for an
early-type galaxy. These sequences have durations of a few x 10^8 yr and occur
repeatedly within a galaxy during its evolution from a late type to an early
type.
