Research goal for the coming year. We hope to: 1. Obtain detailed information about the operation of the voltage-and light-sensitive channels in rods by making simultaneous recordings from individual isolated rods. 2. Control the composition of the fluid contacting the inner surface of the outer segment's envelope, in order to test possible candidates for the internal transmitter and to see whether the transmitter acts to open or to close ion channels. 3. Obtain further information about spatial aspects of the transduction mechanism, particularly how the single photon response amplitude behaves as a function of the longitudinal position in the outer segment at which the photon is absorbed.