Current and constituent quarks in the light-cone quantization

Using the light-cone quantization of the free-quark model, a wide class of unitary transformations which relate the "current" to the "constituent" quark models is constructed. The Melosh transformation is obtained as a special case. The construction clearly exhibits the kinematical aspects of the transformation. Phenomenological applications are discussed. A method for determining acceptable transformations in potential models is formulated.