“ His name is especially known for his work on the cell theory. Uniting F. Dujardin's conception of animal sarcode with H. von Mom's of vegetable protoplasma, he pointed out their identity, and included them under the common name of protoplasm, defining the cell as “a nucleated mass of protoplasm with or without a cell-wall” (Das Protoplasma der Rhizopoden und der Pflanzenzellen; ein Beitrag zur Theorie der Zelle, 1863) . ”