'Scientific topics and controversies' presents a sequence of separate groups of papers in chronological order. A number of significant scientific debates are documented, including Bateson's challenge to findings on variation in cineraria (1892-1897); the controversies over Homotyposis and Karl Pearson's theories on heredity (1895-1908); Paul Kammerer's ideas (1907-1926); and the 'Datura' controversy (1920-1921). There is also material relating to research on 'Crab variation' and the physiology of taste and smell in fish. The controversy over the teaching of evolution in the USA, arising from the reporting of Bateson's Address to the American Association for the Advancement of Science, Toronto 1921, is also documented. The section as a whole includes Bateson's correspondence with many prominent scientists, such as W.F.R. Weldon, E. Ray Lankaster, G.P. Mudge, A.F. Blakeslee and Karl Pearson.