  We show that every gammoid has special digraph representations, such that a
representation of the dual of the gammoid may be easily obtained by reversing
all arcs. In an informal sense, the duality notion of a poset applied to the
digraph of a special representation of a gammoid commutes with the operation of
forming the dual of that gammoid. We use these special representations in order
to define a complexity measure for gammoids, such that the classes of gammoids
with bounded complexity are closed under duality, minors, and direct sums.
