THE PSYCHOLOGICAL ASPECT 317 
individual would not be impelled to the continuance of per- 
formances which occupy a wide space in the field of animal 
behaviour in which the biological end has reference, not to 
present requirements, but to future needs. 
No one has given better expression to the sway of this 
psychological end than Mr. W. H. Hudson. “We see,” he 
says,* “that the inferior animals, when the conditions of life 
are favourable, are subject to periodical fits of gladness, affect- 
ing them powerfully and standing out in vivid contrast to 
their ordinary temper. And we know what this feeling is— 
this periodic intense elation which even civilized man occa- 
sionally experiences when in perfect health, more especially when 
young. There are moments when he is mad with joy, when 
he cannot keep still, when his impulse is to sing and shout 
aloud and laugh at nothing, to run and leap and exert himself 
in some extravagant way. Among the heavier mammalians 
the feeling is manifested in loud noises, bellowings, and 
screamings, and in lumbering, uncouth motions—throwing up 
the heels, pretended panics, and ponderous mock battles. 
“Tn smaller and livelier animals, with greater celerity and 
certitude in their motions, the feeling shows itself in more 
regular and often in more complex ways. Thus Felidz, when 
young, and in very agile sprightly species, like the puma, 
throughout life, simulate all the actions of an animal hunting 
its prey—sudden, intense excitement of discovery, concealment, 
gradual advance, masked by intervening objects, with intervals 
of watching, when they crouch motionless, the eyes flashing 
and tail waved from side to side; finally, the rush and spring, 
when the playfellow is captured, rolled over on his back, and 
worried to imaginary death. Other species of the most 
diverse kinds, in which voice is greatly developed, join in 
noisy concerts and choruses; many of the cats may be 
mentioned, also dogs and foxes, capybaras and other loquacious 
rodents; and in the howling monkeys this kind of perform- 
ance rises to the sublime uproar of the tropical forest at 
eventide. 
* “Naturalist in La Plata,” pp. 280, 281. 
