  We have compared the morphological characteristics of the 891 galaxies in the
Extended 12-micron Sample (E12GS), and assessed the effect of the 12-micron
selection criterion on galaxy properties. The normal spirals in the E12GS have
the same axial ratios, morphological types, and bar and ring fractions as other
normal spirals. The HII/starburst galaxies have a higher incidence of bars, and
more than twice the normal rate of "peculiar" morphologies, both of which are
attributable to relatively recent disturbances. The galaxies with active nuclei
(AGNs: Seyferts and LINERs) have the same incidence of bars as normal spirals,
but show rings significantly more often than normal galaxies or starbursts. The
LINERs have elevated rates of inner rings, while the Seyferts have outer ring
fractions several times those in normal galaxies. The different formation times
of bars and rings suggest an interpretation of these differences. Bars form
relatively quickly, and indicate that material is recently being transported
(by redistribution of angular momentum) to the center of the galaxy, where it
is likely to trigger a short (e.g., $\lesssim 10^8$ yrs) burst of star
formation. Outer rings may result from similar disturbances, but require much
more time to form, while inner rings form in a shorter time, more comparable to
bars. Thus it may be that after an interaction or instability triggers an
infall of gas, the galaxy in the earliest stage is likely to show enhanced star
formation in its center, while later it is more likely to show LINER activity,
and still later likely to be a Seyfert.
