  A key argument in favor of orientation based unification schemes is the
finding that among the most powerful 3CRR radio sources the (apparent) median
linear size of quasars is smaller than that of radio galaxies, which supports
the idea that quasars are a subset of radio galaxies, distinguished by being
viewed at smaller angles to the line of sight. Recent measurements of radio
sizes for a few other low frequency samples are, however, not in accord with
this trend, leading to the claim that orientation may not be the main
difference between radio galaxies and quasars. We point out that this
``inconsistency'' can be removed by making allowance for the temporal evolution
of sources in both size and luminosity, as inferred from independent
observations. This approach can also readily explain the other claimed ``major
discrepancy'' with the unified scheme, namely, the difference between the radio
luminosity--size correlations for quasars and radio galaxies.
