The Collaborative International Dictionary of English v.0.48:

Cystoplast \Cys"to*plast\ (-pl?st), n. [Gr. ???? bladder + ???
   to form.] (Biol.)
   A nucleated cell having an envelope or cell wall, as a red
   blood corpuscle or an epithelial cell; a cell concerned in
   growth.
   [1913 Webster]