I. Fission.

(_a_) As seen in the division of the homogeneous speck of Protoplasm, known as Moneron or Amœba, into two. (_b_) As seen in the division of the nucleated cell, in which the cell‐ nucleus splits into two sub‐nuclei, which either develop within the original cell‐wall or burst it, and multiply outside as independent entities. (_Cf._ the First Root‐Race.)