2 So The N ahtralist in La Plata. 
and is very simple indeed, and, like that of Dr. 
Wallace^ with regard to colour and ornaments, 
covers the whole of the facts. We see that the 
inferior animals, when the conditions of life are 
favourable, are subject to periodical fits of gladness, 
affecting them powerfully and standing out in vind 
contrast to their ordinary temper. And we know 
what this feeling is — this periodic intense elation 
which even civilized man occasionally 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, beliowings and screamings, and in 1am- 
bering, uncouth motions — throwing up of heels, pre- 
tended panics, and ponderous mock battles. 
In smaller and livelier animals, with greater 
celerity and certitude in their motions, the feeling 
shows itself in more regular and often in more com- 
plex ways. Thus, Felidse 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 interven- 
^ It is curious to find that Dr. Wallace’s idea about colour 
has been independently hit upon by Euskin. Of stones he writes 
in Frondes Agrestis : — “ I have often had occasion to allude to 
the apparent connection of brilliancy of colour with vigour of life 
and purity of substance. This is pre-eminently the case in the 
mineral kingdom. The perfection with which the particles of 
any substance unite in crystallization, coriesponds in that king- 
dom to the vital power in organic nature.” 
