[133] “Manual of Psychology,” p. 266.
[134] Op. cit., p. 314.
[135] “Descent of Man,” vol. ii., p. 60, 2nd edit. 1888.
[136] “The Play of Animals,” Eng. trans., p. 229.
[137] Quoted by Groos, op. cit., p. 259.
[138] “Descent of Man,” vol. ii., p. 77.
[139] Darwin, op. cit., p. 99.
[140] Quoted by Darwin, “Descent of Man,” vol. ii., p. 58.
[141] “Descent of Man,” vol. ii., p. 56.
[142] “Habit and Instinct,” p. 217.