THE EVOLUTION OF ANIMAL 
INTELLIGENCE 
CHAPTER I 
INTRODUCTION 
“Tf the doctrine of Evolution is true, the inevitable implication 
is that Mind can be understood only by observing how Mind is 
evolved.’”’—HERBERT SPENCER, Principles of Psychology. 
“ Alle instinktiven Triebe und zweckbewussten Willensiusserungen 
dienen entweder der Erhaltung des eigen Lebens oder der Erzeugung 
und Pflege der Nachkommenschaft.””—ScuneipEr, Der Thierische 
Wille. 
“Si la psychologie humaine est légitime, la psychologie comparée 
Test aussi, pour les mémes raisons.’’—CLAPAREDE. 
In the last two decades the science of animal psychology 
has had an unprecedented development. Previous to this 
time and subsequent to the appearance of the Origin of 
Species students of the animal mind were concerned in 
bringing forward proofs of the similarity of the mental 
processes of men and animals and in tracing the gradual 
unfolding of the mental powers in passing from lower to 
higher forms. The followers of Darwin in their efforts to 
show that evolution is applicable in the mental as well as the 
physical world were naturally prone to minimize the gulf 
separating the human and the animal mind which the tradi- 
tional psychology had formerly taught was a wide and im- 
passible one. 
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