  We propose a resolution of the puzzle posed by the discrepancy between the
pion-nucleon sigma term inferred from pion-nucleon scattering, and that deduced
from baryon mass splittings using the Zweig rule. We show that there is a
significant hypercharge-dependent dynamical contribution to baryon masses, not
hitherto included in the analysis, which may be estimated using the scale Ward
identity, and computed by solution of the Schwinger-Dyson equation for the
quark self-energy. We find that the discrepancy is completely resolved without
the need for any Zweig rule violation.
