  Using the Wick-Cutkosky model and an extended version (massive exchange) of
it, we have calculated the bound states in a quantum field theoretical
approach. In the light-front formalism we have calculated the bound-state mass
spectrum and wave functions. Using the Terent'ev transformation we can write
down an approximation for the angular dependence of the wave function. After
calculating the bound-state spectra we characterized all states found.
Similarly, we have calculated the bound-state spectrum and wave functions in
the instant-form formalism. We compare the spectra found in both forms of
dynamics in the ladder approximation and show that in both forms of dynamics
the O(4) symmetry is broken.
