Various lengths of the body includingthe limb-moving spinal cord segments of young newt larvae were grafted into the side of hosts of the same age. Neural connections did not develop between hosts and grafts. Limb movements of the grafts, appearing spontaneously or evoked by mechanical stimuli, were studied. If only the limb-moving (brachial or lumbosacral) spinal cord segments were incorporated in the grafts, the forelimbs (or hindlimbs) moved synchronously in an oar-stroke manner. If the medulla, or a part of the thoracic section of the spinal cord preceded the limb-moving segments in the neuraxis of the grafts, alternating coordination developed in the movement of the limbs. It was concluded that neural structures controlling alternating coordination reside in the medulla and in the spinal cord. The mechanism of control was brought into relation with sinuous trunk movements.