pt. 1. The historical background: From Neanderthal man to the philosophers of the eighteenth century. Blumenbach and his scientific contemporaries. From Gobineau to Houston Chamberlain. From Kossinna to Hitler --; pt. 2. The biological background: The meaning of "species" --; Hybridity and the species problem. The meaning of "race" --; Some taxonomic and evolutionary theories. Colour. Odour --; pt. 3. Studies of selected human groups: Introduction to Part 3. Physical differences between the ethnic taxa of man : introductory remarks. The Europids. The Jews. The Celts. The Australids (Australian aborigines). The Sanids (Bushmen). The Negrids (Negroes) I : Introduction. The Negrids II : Foreign influences on culture. The Negrids III : Indigenous culture. The Negrids IV : Miscellaneous observations --; pt. 4. Criteria of superiority and inferiority: Introduction to Part 4. The assessment of cognitive ability. The inheritance of cognitive ability. Racial differences in cognitive ability. Racial differences in achievement I : Introduction. Racial differences in achievement II : Civilization --; Conclusion.