Contents

05 May 1972
Vol 176, Issue 4034

About The Cover

Sequential exposure of swimming mod-els of Paramecium made with five successive xenon flashes, 1 second apart, in a thin layer of a solution of adenosine triphosphate-magnesium ions. Since the first flash was brighter than the others, the first image of each model is the brightest. Swimming direction as well as swimming velocity can be determined (about X 22). See page 523. [Y. Naitoh, University of California, Los Angeles]