Two-Way Fish

To Zoology Professor H. W. Lissmann of Cambridge, England, a friend in West Africa sent a small, odd fish with the impressive name Gymnarchus niloticus. It swam forward and backward with equal facility, and it carried a mysterious object m its fingerlike tail. Professor Lissmann put the fish in an aquarium, and admired its skill in avoiding obstacles even when swimming backward. The fish's strange tail, he thought, seemed to be acting like a natural radar.

To test his hunch, Lissmann touched the water with two electrodes connected with an oscillograph. When the two-way fish swam near, a series of regular electrial pulses showed on the oscillograph een. Then Lissmann dipped ends of a copper wire into .the aquarium. The little fish fled in terror, its radar apparently mistaking the wire for a bigger and hostile fash. It also fled from a wire carrying artificial electric pulses. But when Professor Lissmann fed its own pulses back into the water, the fish attacked the electrodes presumably taking them for a rival of its own species.

At this point the Gymnarchus niloticus worn out by excitement, died. Professor Lissmann sadly reported his incomplete findings to Nature, and begged well-wishers in Africa to send him another radar-guided fish.

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