  We study the bialgebra structures on quiver coalgebras and the monoidal
structures on the categories of locally nilpotent and locally finite quiver
representations. It is shown that the path coalgebra of an arbitrary quiver
admits natural bialgebra structures. This endows the category of locally
nilpotent and locally finite representations of an arbitrary quiver with
natural monoidal structures from bialgebras. We also obtain theorems of Gabriel
type for pointed bialgebras and hereditary finite pointed monoidal categories.
