Stages 3 & 4 of fertilization:
Fusion of plasma membranes of oocyte and sperm
- Head and tail of a sperm enter the cytoplasm of the oocyte, but the sperm plasma membrane remains behind.
2nd meiotic division of oocyte is completed
- The secondary oocyte was previously arrested in metaphase of the 2nd meiotic division, and now forms the mature ovum and another polar body.