  We propose a generalisation of a recent work of M. Aguiar and J.-L. Loday on
Quadri-algebras, called Ennea-algebras. In this second version, this paper has
been extended. We show that the augmented free Ennea-algebra is a connected
Hopf algebra and construct explicit formal deformations of dendriform
dialgebras, quari-algebras and ennea-algebras via Baxter operators.
