  The supersymmetry algebra for supermembranes, quantized in the light-cone
gauge, exhibits central charges induced by wrapping the membrane around compact
dimensions. These central charges are manifestly consistent with Lorentz
symmetry. While the central charges raise the mass of the membrane states, they
still leave the mass spectrum continuous, at least generically. The lower bound
on the mass spectrum is set by the winding number and corresponds to a BPS
state.
