Cytoplasmic mixing between three cells expressing HAP2 and RFPcyto. Three cells in the middle (boxed) merge their cytoplasms around time 3:15. We then confirmed that the syncytium contained three nuclei using multifocal sectioning by spinning disc confocal microscopy (Fig. S1). Another cell undergoes karyokinesis around time 3:45 (arrow). See still images in Fig. 1 D.