\Pan*gen"e*sis\, n. [Pan- + genesis.] (Biol.)
An hypothesis advanced by Darwin in explanation of heredity.
Note: The theory rests on the assumption, that the whole
      organization, in the sense of every separate atom or
      unit, reproduces itself, the cells throwing off minute
      granules called gemmules, which circulate freely
      throughout the system and multiply by subdivision.
      These gemmules collect in the reproductive organs and
      products, or in buds, so that the egg or bud contains
      gemmules from all parts of the parent or parents, which
      in development give rise to cells in the offspring
      similar to those from which they were given off in the
      parent. The hypothesis also assumes that these gemmules
      need not in all cases develop into cells, but may lie
      dormant, and be transmitted from generation to
      generation without producing a noticeable effect until
      a case of atavism occurs.