Nuclear fusion in mh embryos during the syncytial blastoderm stage does not depend on crowding or haploidy. White circles mark the centroids of diploid (2n) nuclei that fuse during anaphase of the final nuclear division cycle to give rise to tetraploid (4n) nuclei. Nuclear migration is visualized by lines connecting previous (blue circle) and current centroids (white circle). The final syncytial division cycle prior to MBT occurred at a nuclear density consistent with the penultimate nuclear cycle in wildtype embryos, suggesting that fusion does not depend on the crowding or haploidy. After completion of cellularization (100 minutes) tetraploid cells divide normally. A haploid cell (1n) is marked for reference in bottom right region of the frame.