  A description is given of all primitive differential series mod p of order 1
which are eigenvectors of all the Hecke operators and which are differential
Fourier expansions of differential modular forms of arbitrary order and given
weight; this set of differential series is shown to be in a natural one-to-one
correspondence with the set of series mod p (of order 0) which are eigenvectors
of all the Hecke operators and which are Fourier expansions of (classical)
modular forms of appropriate weight.
