Contraction-Band Formation in Barnacle Myofibrils

Abstract
Contractions induced by adenosine triphosphate, in myofibrils isolated from the barnacle, Balanus aquilia, were observed with a phase microscope. The formation of contraction bands was well under way before the A-band came into contact with the Z-membrane. This is in disagreement with the hypothesis that contraction bands are formed when the A-band pushes against the Z-membrane.