  We show that modular operads are equivalent to modules over a certain simple
properad which we call the Brauer properad. Furthermore, we show that, in this
setting, the Feynman transform corresponds to the cobar construction for
modules of this kind. To make this precise, we extend the machinery of the bar
and cobar constructions relative to a twisting morphism to modules over a
general properad. This generalizes the classical case of algebras over an
operad and might be of independent interest. As an application, we sketch a
Koszul duality theory for modular operads.
