In primitive protoctisis, as in animals, the cell membrane ingrows under the control of a ring of actin microfilaments, and a furrow constricts the cell equator until it pinches the cell in two.

• 在动物细胞中，胞质由肌动蛋白控制，在赤道面处向下凹沟，形成环状缢缩，最后缢缩断裂，细胞一分为二。