  We prove a generalisation to any characteristic of a result of Macdonald that
describes strict polynomial functors in characteristic zero in terms of
representations of the groupoid of finite sets and bijections. Our result will
give an analogous description in terms of finite multisets and an extension of
the notion of bijection appropriate for multisets. A projected application is
to the description of strict polynomial monads that will give a notion
generalising (linear algebra) operads.
