We have analysed the complex movements of vitally stained mitochondria in living eggs of the ascidian (prochordate) embryo soon after fertilization by time lapse confocal (Laser scanning) Microscopy. Our studies clearly show that it is possible to understand how the subcortical mitochondria rich layer contracts, tears and folds to reach its final location in the future posterior pole of the embryo that gives rise to the muscle cell lineage.