Das Protistenreich

Die Welträtsel: Gemeinverständliche Studien über Monistische Philosophie

Last Words on Evolution: A Popular Retrospect and Summary

Natur und Mensch

The Wonders of Life: A Popular Study of Biological Philosophy

The Last Link: Our Present Knowledge of the Descent of Man

Report on the Radiolaria Collected by H.M.S. Challenger During the Years 1873-1876, Plates

Report on the Radiolaria Collected by H.M.S. Challenger During the Years 1873-1876, Second Part: Subclass Osculosa; Index

Report on the Radiolaria Collected by H.M.S. Challenger During the Years 1873-1876, First Part: Porulosa (Spumellaria and Acantharia)

The Riddle of the Universe at the close of the nineteenth century

The History of Creation, Vol. 2 (of 2)

The History of Creation, Vol. 1 (of 2)

Les énigmes de l'Univers

Freedom in Science and Teaching.

Monism as Connecting Religion and Science

The Evolution of Man

The Evolution of Man — Volume 2

The Evolution of Man — Volume 1