Oscar Hertwig ( 21 April 1849 , Friedberg , Hesse â `` 25 October 1922 , Berlin ) was a German zoologist and professor , who also wrote about the theory of evolution over 55 years after Charles Darwin 's The Origin of Species . Oscar Hertwig ( 21 April 1849 , Friedberg , Hesse â `` 25 October 1922 , Berlin ) was a German zoologist and professor , who also wrote about the theory of evolution circa 1916 , over 55 years after Charles Darwin 's book The Origin of Species .