At‐trac″tion sphere. 1. (Zoöl.) (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.
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.