  We consider a generalization of the quiver varieties of Lusztig and Nakajima
to the case of all symmetrizable Kac-Moody Lie algebras. To deal with the
non-simply laced case one considers admissible automorphisms of a quiver and
the irreducible components of the quiver varieties fixed by this automorphism.
We define a crystal structure on these irreducible components and show that the
crystals obtained are isomorphic to those associated to the crystal bases of
the lower half of the universal enveloping algebra and the irreducible highest
weight representations of the non-simply laced Kac-Moody Lie algebra. As an
application, we realize the crystal of the spin representation of so_{2n+1} on
the set of self-conjugate Young diagrams that fit inside an n by n box.
