  We derive the spacetime superalgebras explicitly from ``test'' M-brane
actions in M-brane backgrounds to the lowest order in $\theta$ via canonical
formalism, and discuss various BPS saturated configurations on the basis of
their central charges which depend on the harmonic functions determined by the
backgrounds. All the 1/4 supersymmetric intersections of two M-branes obtained
previously are deduced from the requirement of the test branes to be so ``gauge
fixed'' in the brane backgrounds as to preserve 1/4 supersymmetry. Furthermore,
some of 1/2-supersymmetric bound states of two M-branes are deduced from the
behavior of the harmonic functions in the limits of vanishing distances of the
two branes. The possibilities of some triple intersections preserving 1/4
supersymmetry are also discussed.
