  Section I contains introductory remarks about surface motions. Section II
gives a detailed derivation of $H=-\Delta-Tr\sum_{i<j}[X_i,X_j]^2$ as
describing a quantized discrete analogue of relativistically invariant membrane
dynamics. Section III concerns the question of zero-energy bound-states in
SU(N)-invariant supersymmetric matrix models. Section IV discusses the space of
solutions of some differential matrix equations on $(-\infty,+\infty)$,
interpolating between different representations of $su(2)$. Some exercises are
added, and one remark/conjecture concerning 5-commutators.
