We present a new realization of scalar integrable hierarchies in terms
of the Toda lattice hierarchy. In other words, we show on a large num
ber of examples that an integrable hierarchy, defined by a pseudo-diff
erential Lax operator, can be embedded in the Toda lattice hierarchy.
Such a realization in terms the Toda lattice hierarchy seems to be as
general as the Drinfeld-Sokolov realization.