Hans Spemann ( 27 June 1869 -- 9 September 1941 ) was an German doctor . He won the 1935 Nobel Prize in Physiology or Medicine , for his discovery of the ` organizer effect ' in embryonic development Hans Spemann ( June 27 , 1869 -- September 9 , 1941 ) was a German embryologist who was awarded a Nobel Prize in Physiology or Medicine in 1935 for his discovery of the effect now known as embryonic induction , an influence , exercised by various parts of the embryo , that directs the development of groups of cells into particular tissues and organs .