The Collaborative International Dictionary of English v.0.48:

Attraction sphere \At*trac"tion sphere\
   1. (Zool.)
      (a) The central mass of the aster in mitotic cell
          division; centrosphere.
      (b) Less often, the mass of archoplasm left by the aster
          in the resting cell.
          [Webster 1913 Suppl.]

   2. (Bot.) A small body situated on or near the nucleus in the
      cells of some of the lower plants, consisting of two
      centrospheres containing centrosomes. It exercises an
      important function in mitosis.
      [Webster 1913 Suppl.]