  The Mesoscopic Mechanics (MeM), which has been introduced in a previous
paper, is relevant to the electron gas confined to two spatial dimensions. It
predicts a special way of collective response of correlated electrons to the
external magnetic field. The dynamic variable of this theory is a
finite-dimensional operator, which is required to satisfy the mesoscopic
Schr\"{o}dinger equation (cf. text).
  In this article, we describe general solutions of the mesoscopic
Schr\"{o}dinger equation. Our approach is specific to the problem at hand. It
relies on the unique structure of the equation and makes no reference to any
other techniques, with the exception of the geometry of unitary groups. In
conclusion, a surprising fact comes to light. Namely, the mesoscopic dynamics
"filters" through the (microscopic) Schr\"odinger dynamics as the latter turns
out to be a clearly separable part, in fact an autonomous factor, of the
evolution. This is a desirable result also from the physical standpoint.
