07 April 2000
Vol 288, Issue 5463

About The Cover

Cover image expansion

COVER The stalk structure (bottom) of the unicellular organism Vorticella (120 magnification). This structure, shown in its contracted state, houses one of the most powerful biological mechanochemical springs known, extending and contracting the stalk up to 2 millimeters in milliseconds. A special section on the principles of movement, from molecular and cellular to organismal and robotic, begins on page 79 [Image: E. R. Degginger/Animals, Animals]