The study concerns survival, regeneration and axonal growth of isolated neuronal groups during their development using tissue culture technique. The organ of Corti of the mouse at different developmental ages will be the tissue of choice. Morphological observations will be made using light microscopy and time-lapse cinematography for the study of live tissue; light microscopy, SEM and TEM techniques for the study of fixed material. The proposed project includes: 1. Study of the development of neurosensory contacts and the synaptic types formed between the peripheral fibers of the spiral ganglion cells and hair cells, and the relations between synapse formation and the developmental age of the organ, 2, Study of the regnerative capacity of the central and peripheral fibers of the spiral ganglion cells at different stages of nerve cell maturation. 3. Study of the formation or reformation of neurosensory contacts in dissociated cell cultures and in cultures in which the neuronal and sensory elements have been separated by transection. 4. Study of conditions which promote or prevent continuous growth of a peripheral spiral fiber. Such growth is known to occur apparently when the synaptic contacts with the sensory cell are lost, but nothing more is known about this phenomenon at present. 5. Study to determine whether the axonal growth of the spiral ganglion cells can be directed towards their normal targets in cultures combining the organ of Corti and different parts of the cochlear nucleus complex.