sentences:  He denied naturalist Christian Gottfried Ehrenberg's theory that microscopic organisms were "complete organisms" similar to higher animals, specifically noting that they had specialized structures unique to single-celled organisms, which meant that foraminifera he was studying was not, as his contemporaries believed it to be, a mollusk.In addition to his studies of microscopic life, he did extensive research on invertebrate groups that included echinoderms, hexapods, helminths and cnidarians.In the Foraminifera, he noticed an apparently formless life substance that he named "sarcode", later renamed protoplasm by Hugo von Mohl (1805–1872).