Walther Flemming

Walther Flemming (born April 211843 in Sachsenberg, Germany; died August 41905 in Kiel) was a founder of the study of cytogenetics.

He was born as the fifth child and only son of the psychiatrist Carl Friedrich Flemming (1799-1880) and his second wife, Auguste Winter. He did his basic studies at the Gymnasium der Residenzstadt, where one of his colleagues and lifelong friends was writer Heinrich Seidel. Flemming trained in medicine at the University of Rostock, graduating in 1868. Afterwards. he served in 1870-1871 as a military physician at the Franco-Prussian War. From 1873 to 1876 he worked as a teacher at the University of Prague. In 1876 he accepted a post as a professor of anatomy at the University of Kiel, where he stayed until 1901, shortly before his death, and where he became the director of the Anatomical Institute.

Making use of aniline dyes he was able to find a structure which strongly absorbed basophilic dyes, which he named chromatin. He identified that chromatin was correlated to Edouard Van Beneden (1846-1910) had independently observed them, too.

Flemming investigated the process of cell division and the distribution of chromosomes to the daughter nuclei, a process he called mitosis from the Greek word for thread. However, he did not yet realize the splitting into identical halves, the daughter chromatids. He studied mitosis both in vivo and in stained preparations, using as the source of biological material the fins and gills of salamanders. These results were published in 1882 in the seminal book Zellsubstanz, Kern und Zelltheilung (1882; Cell Substance, Nucleus and Cell Division). On the basis of his discoveries, Flemming surmised for the first time that all cell nuclei came from another predecessor nucleus (he coined the phrase omnis nucleus e nucleo, after Virchow's omnis cellula e cellula).

Flemming was unaware of Gregor Mendel's (1822-1884) work on heredity, so he did not make the connection between his observations and genetic inheritance. Two decades would pass before the significance of Flemming's work was truly realized with the rediscovery of Mendel's rules. His discovery of mitosis and chromosomes is considered one of the 100 most important scientific discoveries of all times, and one of the 10 most important discoveries in cell biology (together with August Weismann's (1834-1914) discovery of meiosis, Theodor Schwann (1810-1882) and Matthias Schleiden's (1804-1881) cell theory and  Thomas Hunt Morgan's (1866-1945) first genetic maps).

Flemming's name is honoured by a medal awarded by the German Society for Cell Biology (Deutschen Gesellschaft für Zellbiologie).