  A whole class of non-perturbative QCD studies, e.g. the instanton models,
chiral quark models, etc. indicates that the effective degrees of freedom for
the physics in the low Q^(2) < 1 GeV^(2) region could be the constituent quarks
(CQs) and internal Goldstone bosons (IGBs). This leads to a nucleon structure
with the spin being carried by three constituent quark systems, each composed
of a massive compact CQ surrounded by a q\bar{q} sea perturbatively generated
by the valence quark's IGB emissions. Such a CQ-system has a total angular
momentum of 1/2 and a small anomalous magnetic moment, built up from a
quark-spin polarization and a significant orbital motion in the quark sea. The
distinctive phenomenological signal for such a non-perturbative structure is
that the sea-quarks are polarized negatively, while the antiquarks are not
polarized. This picture also suggests a negligibly small gluon polarization.
All such features can be tested by experiments in the near future.
