The Foraminifera are an enormously successful group of predominantly marine protists. They first appeared in the rock record >500 million years ago and currently are found in most planktonic and benthic marine and marginal marine environments. Though complete life cycles are known for only ˜30 of the >10,000 described extant species, these taxa illustrate reproductive patterns that are among the most diverse of all protists. The foraminiferal life cycle typically is characterized by an alternation of sexual and asexual generations during which meiosis occurs in the early phases of schizogony in the agamont. Sexual reproduction involves the production of biflagellated, triflagellated, or amoeboid gametes, and fertilization may be gametogamous, gamontogamous, or autogamous. Of these options, most Foraminifera for which sexual reproduction has been documented (44 species) produce many thousands of small biflagellated gametes that are shed directly into the surrounding seawater where gametogamous fertilization occurs.