• A Candid Examination of Theism
• An Examination of Weismannism
• Animal Intelligence: The International Scientific Series, Vol. XLIV.
• Darwin, and After Darwin, Volume 2 of 3: Post-Darwinian Questions: Heredity and Utility
• Darwin, and After Darwin, Volume 3 of 3: Post-Darwinian Questions: Isolation and Physiological Selection
• Darwin, and After Darwin, Volumes 1 and 3: An Exposition of the Darwinian Theory and a Discussion of Post-Darwinian Questions
• Jelly-Fish, Star-Fish, and Sea-Urchins: Being a Research on Primitive Nervous Systems
• Mental Evolution in Man: Origin of Human Faculty
• Mind and Motion and Monism
• The Life and Letters of George John Romanes, M.A., LL.D., F.R.S.
• The Scientific Evidences of Organic Evolution
• Thoughts on Religion