  The Hopf algebra of Feynman diagrams, analyzed by A.Connes and D.Kreimer, is
considered from the perspective of the theory of effective actions and
generalized $\tau$-functions, which describes the action of diffeomorphism and
shift groups in the moduli space of coupling constants. These considerations
provide additional evidence of the hidden group (integrable) structure behind
the standard formalism of quantum field theory.
