As far as is known today, only fish, in the entire animal kingdom, possess special organs which produce an electric field. For several dozens of years now, many scientists have been interested in the biological significance of th is electric field. Particularly important was Lissrnann's discovery of the fact that the socalIed "weakly" electric fish, the discharges of which are not sensitive to man and were therefore unknown until now, use the electric field to locate objects in their environment. Many questions arose which had their origins in this discovery. What are the biological basis for...