We study in detail the structure of the Lorentz covariant, spacetime supersymmetric lldimensional supermembrane theory. We show that for a flat spacetime background, the spacetime supersymmetry becomes an N =8 world volume (rigid) supersymmetry in a "physical" gauge; we also present the field equations and transformation rules in a "lightcone" gauge. We semiclassically quantize the closed torodial supermembrane on a spacetime (Minkowki), x (flu/ 'I-torus), and review some mathematical results that are relevant for path integral quantization. 'cl