[Axonal projections of the cells of the dorsal ganglia in the lumbar segments of the spinal cord in tadpoles of the toad Xenopus laevis].

Using anterograde labeling by horseradish peroxidase, studies have been made on the formation of axonal projections of cells of the dorsal ganglia in lumbar segments of Xenopus tadpoles at different stages of development of their hindlimbs. It was shown that at the early stages of premetamorphosis, primary afferents grow into the spinal cord and form collaterals directed into the grey matter. During prometamorphosis, the axons reach lateral motor nucleus. At final stages of prometamorphosis, when the hind limbs are used for locomotion, as well as at further stages of development, axons of the 9th and 10th dorsal roots reach motoneurons mainly in the Xth, not the IXth segment. During final stages of metamorphosis, contralateral projections of primary afferents were found in the lumbar segments. In two experiments, labeled interneurons were revealed in the intermediate grey matter. Organization and development of the primary afferent projections in the anuran spinal cord are discussed.