  We study de Wit-Hoppe-Nicolai supermembrane with emphasis on the winding in
M-direction. We propose a SUSY algebra of the supermembrane in the Lorentz
invariant form. We analyze the BPS conditions and argue that the area
preserving diffeomorphism constraints associated with the harmonic vector
fields play an essential role. We derive the first order partial differential
equation that describes the BPS state with one quarter SUSY.
