  We study when a cosmological constant is a natural issue if it is mimicked by
the potential of a massive Hyperextended Scalar Tensor theory with a perfect
fluid for Bianchi type I and V models. We then deduce a reciprocal Wald theorem
giving the conditions such that the potential tends to a non vanishing constant
when the gravitational function varies. We also get the conditions allowing the
potentiel to vanish or diverge.
