  In ten space-time dimensions the number of Majorana-Weyl fermions is not
conserved, not only during the time evolution, but also by rotations. As a
consequence the empty Fock state is not rotationally symmetric. We construct
explicitly the simplest singlet state which provides the starting point for
building up invariant SO(9) subspaces. The state has non-zero fermion number
and is a complicated combination of the 1360 elementary, gauge invariant,
gluinoless Fock states with twelve fermions. Fermionic structure of higher
irreps of SO(9) is also briefly outlined.
