186 THE CONDOR Vol. XXIII 
call in the assistance of natural telepathy or ‘any other peculiar psychic force 
to explain the facts. Such explanations merely reduce the known to terms of 
the unknown, and claim to have solved the problem when they have only 
avoided it. 
That organized groups are possessed of a more or less definite ‘‘aggre- 
gate mind’’ there seems to be ample evidence. That this collective mind ex- 
hibits certain peculiar properties distinct from those of the individual minds 
composing it, few will deny. But that these properties are of a hypnotie (Le 
Bon, p. 10) or telepathic (Long, loc. cit.) nature, satisfactory evidence is lack- 
ing. It is the belief of the writer that the spread of impulse—exceedingly 
rapid in well organized groups, slowly enough to be readily observed in icss 
unified aggregations, but always through the normal channels of sense—is 
entirely adequate to explain the mind of the flock. 
‘ 
LITERATURE CITED 
Groos, K. 
1898. The play of animals. Baldwin translation. (New York, D. Appleton and 
Co.), xxvi+341 pp. 
Huxley, J. S. 
1912. The individual in the animal kingdom. (Cambridge, University Press), 
167 pp. 
Kessel, J. F. 
1921. Flocking habits of the California Valley Quail. Condor, vol. 23, pp. 167-168. 
Le Bon, G. 
1897. The crowd. Second ed. (London, T. Fisher Unwin), xxii+219 pp. 
Long, W. J. 
1919. How animals talk. (New York, Harper and Brothers), 302 pp., 8 pls. 
Miller, R. C. 
1921. The flock behavior of the Coast Bush-tit. Condor, vol. 23, pp. 121-127. 
Newland, C. B. 
1917. What is instinct? (New York, Frederick A. Stokes and Co.), xvi+217 pp., 
18 pls. 
Trotter, W. 
1916. Instincts of the herd in peace and war. (London, T. Fisher Unwin, Ltd.), 
218 pp. 
Uexkull, J von 
1909. Umwelt und Innenwelt der Tiere. (Berlin, Julius Springer), 259 pp. 
Woodward, C. H. 
1921. The California Brown Pelican as a navigator. Condor, vol. 23, pp. 137-138. 
Department of Zoology, University of California, October 4, 1921. 
’ 
