BOVERI, THEODOR HEINRICH

(b. Oct. 12, 1862, Bamberg, Bavaria d. Oct. 15, 1915, Wrzburg), German cytologist whose work with roundworm eggs proved that chromosomes are separate, continuous entities within the nucleus of a cell. Boveri received an M.D. degree (1885) from the University of Munich and from 1885 until 1893 was engaged in cytological research at the Zoological Institute in Munich. In 1885 he began a series of studies on chromosomes. His first major report (1887) described the development of an unfertilized egg, including the formation of polar bodies (small cells that result from the division of an unfertilized egg). Later he described finger-shaped lobes that appeared in the nuclei of eggs of the roundworm Ascaris during early cleavage stages. These structures, he decided, were chromosomes, previously believed to be part of the nucleus and present only during nuclear division. Boveri's third report proved the theoryintroduced by Belgian cytologist Edouard van Benedenthat the ovum and sperm cell contribute equal numbers of chromosomes to the new cell created during fertilization. Later, Boveri introduced the term centrosome and demonstrated that this structure is the division centre for a dividing egg cell. He also proved that a single chromosome is responsible for particular hereditary traits and demonstrated the importance of cytoplasm by showing that chromosomes are influenced by the cytoplasm surrounding the nucleus. In 1893 he was appointed professor at the University of Wrzburg.