[163] “Animal Intelligence,” p. 413.
[164] Atalanta, Jan., 1889. Reprinted in “Animal Sketches,” p. 17.
[165] “The Play of Animals,” p. 122.
[166] Appendix to “Animal Intelligence,” p. 486.
[167] “Manual of Ethics,” p. 1.
[168] “Animal Life and Intelligence,” p. 404.
[169] “Animal Life and Intelligence,” p. 400. “Introduction to Comparative Psychology,” p. 369.
[170] “Animal Intelligence,” p. 444.
[171] “The Play of Animals,” p. 299.
[172] Op. cit., p. 145.