  We describe the worldvolume for the bosonic sector of the lower-dimensional
F-theory that embeds 5D, N=1 M-theory and the 4D type II superstring. This
theory is a complexification of the fundamental 5-brane theory that embeds the
4D, N=1 M-theory of the 3D type II string in a sense that we make explicit at
the level of the Lagrangian and Hamiltonian formulations. We find three types
of section condition: in spacetime, on the worldvolume, and one tying them
together. The 5-brane theory is recovered from the new theory by a double
dimensional reduction.
