First Schaudinn and Hoffmann named the causative organism of syphilis Spirochaeta pallida. Short time later Schaudinn proposed the name Treponema. He mentioned it in a letter of October 14, 1905 to Hoffmann. He supposed that this germ may be a flagellate. This was not correct. The electron-microscopic investigations revealed that this idea did not concur. Therefore it is better to call them Spirochaeta pallida and not Treponema pallidum any more.