gemmule

gemmule
    n 1: the physically discrete element that Darwin proposed as
         responsible for heredity
    

Gemmule \Gem"mule\, n. [L. gemmula, dim. of gemma: cf. F.
   gemmule. See {Gem}.]
   1. (Bot.)
      (a) A little leaf bud, as the plumule between the
          cotyledons.
      (b) One of the buds of mosses.
      (c) One of the reproductive spores of alg[ae].
      (d) An ovule.
          [1913 Webster]

   2. (Biol.)
      (a) A bud produced in generation by gemmation.
      (b) One of the imaginary granules or atoms which,
          according to Darwin's hypothesis of pangenesis, are
          continually being thrown off from every cell or unit,
          and circulate freely throughout the system, and when
          supplied with proper nutriment multiply by
          self-division and ultimately develop into cells like
          those from which they were derived. They are supposed
          to be transmitted from the parent to the offspring,
          but are often transmitted in a dormant state during
          many generations and are then developed. See
          {Pangenesis}.
          [1913 Webster]