Younger brother of Oscar Hertwig; 1868-1871 studied medicine and zoology at the universities of Jena (under Ernst Haeckel), Zürich and Bonn together with Oscar, where both received their M.D. in 1872; 1872 assistant of Max Schultze (again together with his brother) at the anatomical institute in Bonn; 1875 Ph.D. and Habilitation in Jena, where he became assoc. professor for zoology in 1878; 1881 professor for zoology at the University of Königsberg (Kaliningrad); 1883 professor for zoology at the University of Bonn; 1885 professor for zoology and director of the Institute for Zoology at the University of Munich; 1925 retired.
