Fig. 6. The patterns of spindle formation and subsequent cytokinesis in polyspermic zygotes of S. lomentaria after fertilization. (A-D) Fertilization and germination. (A) Two male gametes fuse to one female. (B) Just after fertilization, there are three chloroplasts and three pairs of centrioles. (C) Female centrioles disappear and two pairs of centrioles from male gametes remain. (D) Before mitosis, the two pairs of centrioles duplicate into four. (E-G) Spindle formation in polyspermic zygotes. (E) Tetra-polar spindle. (F) Tri-polar spindle. One of the three poles contains two pairs of centrioles. (G) Tri-polar spindle. One of the four pairs of centrioles locates away from spindle. (H-I) Cytokinesis in polyspermic zygotes. (H) Four daughter cells are produced. Each cell contains a nucleus, a centrosome and a chloroplast. (I) Three daughter cells are produced. Each cell contains a nucleus and a chloroplast. All cells have a centrosome, and one cell contains two centrosomes. At that time, two centrosomes adjoin and function as one MTOC. (J) Four daughter cells are produced. Each cell contains a centrosome and a chloroplast. Sometimes, a cell is produced without a nucleus. FC, centrioles derived from female gamete; FCh, chloroplast from female gamete; MC, centrioles derived from male gamete; MCh, chloroplast from male gamete.