A crude enzyme preparation from the marine amoeba Trichosphaerium was used to produce protoplasts from Sargassum muticum, Macrocystis pyrifera, Porphyra perforata, and other red and brown marcroalgae . Cortical and medullary protoplasts of Sargassum, which were impossible to obtain using mixtures of previously available enzymes, have now been prepared . Intact inner cortical and medullary protoplasts of Macrocystis, which were not observed in past isolations, were obtained . Improved protoplast yields of as much as 500 fold resulted from feeding the amoebae on specific seaweeds . Cuticles of live Sargassum and Macrocystis were digested easily by the amoebae . However, cuticles of autoclaved Macrocystis and those of Porphyra (fresh or autoclaved) were eaten last . In spite of the absence of identifiable extracellular enzymatic activity in the medium, the amoebae were able to `cut' and consume live fronds and blocks of gelled agars, carrageenans, and alginates .