The Collaborative International Dictionary of English v.0.48:

Idioplasma \Id`i*o*plas"ma\, n. [NL., fr. Gr. 'i`dios proper,
   peculiar + ? a form, mold.] (Biol.)
   That portion of the cell protoplasm which is the seat of all
   active changes, and which carries on the function of
   hereditary transmission; -- distinguished from the other
   portion, which is termed nutritive plasma. See Hygroplasm.
   [1913 Webster]