[1] Cf. Loeb, Jacques, “Comparative Physiology of the Brain and
Comparative Psychology,” New York, 1900.
[2] For an excellent discussion of this problem see Holmes, Prof. S.
J., “The Evolution of Animal Intelligence,” Pages 63-89, New York,
1911; and Jennings, Prof. H. S., “Behavior of Lower Organisms,”
New York, 1906. See also, Day and Bentley, “A Note on Learning in
Paramœcium,” _Journal of Animal Behavior_, 1, 67, 1911; and Watkins, G.
P., “Psychical Life in Protozoa,” _American Journal of Psychology_, 11,
166, 1900.
[3] Italics mine.