We analyze the structure of the algebra K < x >(Gn) of symmetric polynomials in non-commuting variables in so far as it relates to K[x](Gn), its commutative counterpart. Using the "place-action" of the symmetric group, we are able to realize the latter as the in variant polynomials inside the former. We discover a tensor product decomposition of K < x >(Gn) analogous to the classical theorems of Chevalley, Shephard-Todd on finite reflection groups.