  A well pronounced spin--grouping of baryon resonances to O(4) partial waves
is found in baryon spectra and shown to be well interpreted in terms of Lorentz
group representations of the type (1/2 +l', 1/2 +l')* [(1/2, 0)+(0,1/2)] with
l' integer. In this way the relativistic description of finite dimensional
resonance towers containing higher-spin states becomes possible. It is further
argued that the nucleon excitations into the l'=1 and l'=2 multiplets are
chiral phase transitions.
