Oscar Hertwig

Oscar Hertwig (21 April 1849 to 25 October 1922) was a German embryologist and zoologist known for his research in developmental biology and evolution, and is credited as the first person to observe sexual reproduction at the cellular level, by watching the cells of sea urchins under the microscope. He and his younger brother Richard Hertwig were the most eminent scholars of Ernst Haeckel and Carl Gegenbaur from the University of Jena, and between 1879 and 1883 they carried out embryological studies, especially on the theory of the coelom. In 1888 Oscar became a professor of anatomy in Berlin. He proved that fertilization occurs through the fusion of a sperm and an egg cell, recognized the role of the cell nucleus in inheritance and of chromosome reduction in meiosis, and in 1876 published that fertilization includes the penetration of a spermatozoon into an egg cell. His experiments with frog eggs revealed the long axis rule, or Hertwig rule, and in 1885 he wrote that nuclein, later called nucleic acid, is responsible for fertilization and for the transmission of hereditary characteristics, an early suggestion shown to be correct in 1944. He wrote a leading textbook and opposed the role of chance assumed in Darwin's theory.