Fig. 1. Tethering and fusion of yolk granules isolated in IM buffer. Tethered yolk granules (A) before (0 second) and (B-D) at various time points after perfusion of Ca²⁺ (300 µM) into a slide coverslip chamber. Prior to Ca²⁺ buffer addition the vesicles are tethered to one another, forming large aggregates. These tend to fuse with one another as soon as Ca²⁺ reaches them, forming a large `patch' vesicle product whose size reflects that of the tethered aggregate. Bar, 10 µm.