An anlaysis of the phase relationship between the same side legs (homolateral coupling) of Rock Lobster (Crustacea) is performed during sequence of locomtion. On intact animals the phase relationship is similar to the most common insect or mammalian patterns ('alternating model'). After successive autotomy of the walking legs, another coordination pattern occurs progressively; it is an 'in phase model'. From these experiments it can be concluded that there exists a central motor program tightly coordinating each thoracic ganglion and that the alternating pattern could be due to a reorganization of the synchronous system by a peripheral proprioceptive inflow.