Mendelism

ar. Except for the relatively rare instances of parthenogenesis a new individual, whether plant or animal, arises as the joint product of two sexual cells derived from individuals of different sexes. Such sexual cells, whether ovules or ova, spermatozoa or pollen grains, are known by the general term of GAMETES, or marrying cells, and the individual formed by the fusion or yoking together of two gametes is spoken of as a ZYGOTE. Since a zygote arises from the yoking together of two separate gametes, the individual so formed must be regarded throughout its life as a double structure in which the components brought in by each of the gametes remain intimately fused in a form of partnership. But when the zygote in its turn comes to form gametes, the partnership is broken and the process is reversed. The component parts of the dual structure are resolved, with the formation of a set of single structures, the gametes.

The life cycle of a species from among the higher plants or animals may be regarded as fall