ABSTRACT
Reproduction by means of gametes is gamogony. It thus includes all the amphimicitic processes and the parthenogenetic ones (heterogamy and isogamy, amphigony, exogamy, allogamy, dissogeny, endogamy, and automixis) as well as pseudogamy, plasmogony, and gonomery. The production of gametes in any individual is gametogenesis, including spermatogenesis and oogenesis. The term fertilization is variously used for fusion of gametes, for such fusion followed by fusion of the nuclei, or merely for insemination or even copulation. There are three activities to be specified in fertilization: penetration or fusion of the gametes, fusion of the nuclei, and activation of the ovum. Syngamy is thus fusion of two gametes without specification of what happens to the gamete nuclei. It occurs in most species of most groups of animals, but it is absent in those species using hologamy, conjugation, nuclear reorganization, activation, some cases of parthenogenesis, and exclusively asexual reproduction.
