  It is shown that even for large spins $J$ the fundamental difference between
integer and half-integer spins persists. In a quasi-classical description this
difference enters via Berry's connection. This general phenomenon is derived
and illustrated for large spins confined to a plane by crystalline electric
fields. Physical realizations are rare-earth Nickel Borocarbides. Magnetic
moments for half-integer spin
  (Dy$^{3+}$, $J=15/2$) and magnetic susceptibilities for integer spin
(Ho$^{3+}$, $J=8$) are calculated. Experiments are proposed to furnish evidence
for the predicted fundamental difference.
