  By combining new long-slit spectral data obtained with the Southern African
Large Telescope (SALT) for 9 galaxies with previously published our
observations for additional 12 galaxies we study the stellar and gaseous
kinematics as well as radially resolved stellar population properties and
ionized gas metallicity and excitation for a sample of isolated lenticular
galaxies. We have found that there is no particular time frame of formation for
the isolated lenticular galaxies: the mean stellar ages of the bulges and disks
are distributed between 1 and > 13 Gyr, and the bulge and the disk in every
galaxy formed synchronously demonstrating similar stellar ages and
magnesium-to-iron ratios. Extended ionized-gas disks are found in the majority
of the isolated lenticular galaxies, in 72%$\pm$11%. The half of all extended
gaseous disks demonstrate visible counterrotation with respect to their stellar
counterparts. We argue that just such fraction of projected counterrotation is
expected if all the gas in isolated lenticular galaxies is accreted from
outside, under the assumption of isotropically distributed external sources. A
very narrow range of the gas oxygen abundances found by us for the outer
ionized gas disks excited by young stars, [O/H] from 0.0 to +0.2 dex, gives
evidence for the satellite merging as the most probable source of this
accretion. At last we formulate a hypothesis that morphological type of a field
disk galaxy is completely determined by the outer cold-gas accretion regime.
