A general concept of phenotypical structure over a genotypical structure is
developed. The direct decompositions of multilocus phenotypical structures
are considered. Some aspects of phenotypical heredity are described in ter
ms of graph theory. The acyclic phenotypical structures are introduced and
studied on this base. The evolutionary equations are adjusted to the phenot
ypical selection. It is proved that if a phenotypical structure is acyclic
then the set of fixed points of the corresponding evolutionary operator is
finite except for a proper algebraic subset of the operator space. Some app
lications of this theorem are given. (C) 2001 Academic Press.