Oken, [130], [132], [133]Old Testament, [90]Omar, [272]Optimism, [270]Orangs, [149]Order of nature, [255], [258]Organic versus Inorganic, [229]Organon, [242]Origin of species, [89], [95], [101], [102], [110]Origin of Species, reviews of, [113], [114], [115], [146]