Fig. 6. Confocal image of live embryo at the beginning of the second cleavage, continuously bathed in FM1-43 and cytochalasin B. Figure shown is a flat projection of a stack of images captured through 300 µm of specimen depth. Fluorescing FM1-43 accumulates in the new membrane domain of the first cleavage plane (broad vertical stripe), but not in the original membrane domains (asterisk). Localized bright-staining puncta along the new/old membrane boundaries correspond to collections of long microvilli, and do not represent sites of endocytosis (data not shown). Membrane newly inserted along the second cleavage furrow (surrounding arrow) is momentarily less well-labeled than that previously inserted along the first furrow.