This note investigates the image of the transfer homomorphism for permutation representations of finite groups over finite fields. One obtains a number of results showing that the image of the transfer $\Im (\Tr)$ together with certain Chern classes generate the ring of invariants as an algebra. By a careful analysis of orbit sums one finds the surprising fact that the ideal $\Im (\Tr)$ is a prime ideal for cyclic $p$-groups and determines an upper bound on its height.