[Footnote 15: _Cellular Psychology_. See on this my paper on "Cell-souls and Soul-cells," in the _Deutsche Rundschau_ (July 1878), reprinted in Part 1, of _Collected Popular Lectures_; also "The Cell-soul and Cellular Psychology" in my discourse on _Freedom in Science and Teaching_ (Stuttgart, 1878; Eng. tr., 1892, p. 46); _Natural History of Creation_ (8th ed., pp. 444, 777); and _Descent of Man_ (4th ed., pp. 128, 147). See also, Max Verworn, _Psycho-physiologische Protisten-Studien_ (Jena, 1889), and Paul Carus, _The Soul of Man: An Investigation of the Facts of Physiological and Experimental Psychology_ (Chicago, 1891). Among recent attempts to reform psychology on the basis of evolutionary doctrine in a monistic sense, special mention must be made of Georg Heinrich Schneider's _Der thierische Wille: Systematische Darstellung und Erklärung der thierischen Triebe und deren Entstehung, Entwickelung und Verbreitung im Thierreiche als Grundlage zu einer vergleichenden Willenslehre_[X] (Leipsic, 1880). Compare also his supplementary work, entitled _Der menschliche Wille vom Standpunkte der neuen Entwickelungstheorie_[XI] (1882); also the _Psychology of Herbert Spencer_ and the new edition of Wilhelm Wundt's _Menschen-und Thierseele[XII]_ (Leipsic, 1892). Note X "Will in the Lower Animals: a Systematic Exposition and Explanation of Animal Instincts, and their Origin, Development, and Difference in the Animal Kingdom, as Basis of a Comparative Doctrine of Volition." Note XI "The Human Will from the Standpoint of the Modern Theory of Evolution." Note XII "Soul in Man and Brute."