(a) Schematic of the cross-correlation image analysis algorithm used to measure the movement of the cell cytoplasm (detailed description in Methods). (b) A schematic representation of the analysed stages: MII: unfertilized eggs in metaphase of the second meiotic division. Stage 1: 2PB is formed and FC first appears. Stage 2: FC is fully formed. Stage 3: FC regresses and pronuclei are formed. (c) Mean cytoplasmic speed in a representative unfertilized egg. (d) Mean cytoplasmic speed in a representative in vivo fertilized zygote during Stages 1–3. (e) DIC images with vector patterns representative for unfertilized eggs (MII) and for zygotes in Stage 1–3. For clarity, only every second vector is shown. Length of the vectors and colour of the background indicate speed of the local cytoplasmic movement. Scale bar, 10 μm.