 Late in the nineteenth century cytologists also succeeded in identifying membrane-enclosed structures in the cytoplasm that came to be known as organelles. Altmann (1890), using new stains he developed, observed filaments within cells that he took to be elementary organisms (a view he explicitly set in opposition to the protoplasm theory). Although many researchers challenged Altmann’s observations, Benda (1899) confirmed the existence of filaments using a different stain and gave them the name mitochondria (Greek for “thread” and “granule”). Because of their reactivity with oxidative stains, Michaelis (1899) proposed that they figured in oxidative reactions in cells. Yet other researchers identified other organelles such as the Golgi apparatus (Golgi 1898) and ergastoplasm (Garnier 1897), which was ultimately identified as the endoplasmic reticulum.