am·phi·mix·is 
(ăm′fə-mĭksĭs)
(ăm′fə-mĭksĭs)n. pl. am·phi·mix·es (-mĭksēz′)
The union of the sperm and egg in sexual reproduction.
[AMPHI- + Greek mixis, a mingling (from meignunai, mik-, to mingle; see meik- in the Appendix of Indo-European roots).]
am′phi·mictic (-mĭktĭk) adj.