For lobe-dominated FR II sources, a jet velocity field may imply that Doppler "hiding" does more than just make jets in radio galaxies appear less prominent than those in quasars. The key point is this: when imaging relativistically-moving flows at large enough angles to our line of sight, we will preferentially see the emission from their slower-moving parts. This biases us towards visualizing emission from an outer shear layer in such jets, and against visualizing emission from faster-moving inner ``spines''.
Emphasis on emission from a shear layer can explain the preponderance of parallel (i.e., axial) B-fields in FR II jets (Bridle 1984), the polarization "rails" and flat-topped intensity profiles in 3C353's well-resolved jet (Swain, Bridle, & Baum, these Proceedings) and the edge-brightening of the outer jet in Cygnus A (Carilli et al., these Proceedings). Could we distinguish Doppler "hiding" from true emissivity enhancements in the boundary layers or cross-sectional evolution due to surface instabilities (Hardee, these Proceedings)? High-resolution studies of FR II sources might do this statistically by looking for systematic differences in the transverse profiles of intensity and polarization in the jets and counterjets of narrow-line radio galaxies, broad-line radio galaxies, and quasars, and by looking at the evolution of these profiles along individual jets. This would be a good task for the upgraded and extended VLA (Bastian & Bridle 1995).
Bias against emission from the spines may mean that a significant fraction of the energy transport is in Doppler-hidden ``beams'' within the FR II jets. Could this be why the hot spots in extended 3CR quasars ``know'' whether they are on the jetted or counterjetted side-those fed by the brighter jet are more compact, and more prone to recession into their lobes, than those fed by counterjets (Laing 1989; Bridle et al. 1994a)? If the jet asymmetry is due to bulk relativistic motion, the hot spot asymmetry asks that flow with an appreciable Doppler factor persists as far as, even through, the hot spots. (Komissarov & Falle (these Proceedings) showed an axi-symmetric numerical model that contained such effects and suggested that they may be larger than were predicted by Wilson & Scheuer (1983); it will be important so see if their result persists in 3D.) This is easier to reconcile with the modest estimates of Lorentz factors in the observed FR II quasar jets (Bridle et al. 1994a; Wardle & Aaron, these Proceedings) if these are biased low by Doppler-hiding of their spines. If the most compact hot spots mark where jet spines finally decelerate and decollimate, their asymmetries may contain the ``last gasp'' of relativistic beaming in FR II sources.