  This paper is a continuation and elaboration of our work quant-ph/0206057
(Nucl. Phys. B, 1968, 7, 79) where some approach to the variable-mass problem
were proposed. Here we have found a concret realization of irreducible
representations of the inhomogeneous group P(1,n) - the group of translations
and rotations in (1+n)-dimensional Minkowski space in two classes (when
P_0^2-P_k^2>0 and P_0^2-P_k^2<0). All the P(1,n)-invariant equations of the
Schrodinger-Foldy type are written down. Some questions of a physical
interpretation of the quantum, mechanical scheme based on the inhomogeneous de
Sitter group P(1,n) are discussed.
