The Death- feigning Instinct. 201 
simulating instinct, tliougli it is hardly possible to 
believe that the action springs from the same im- 
mediate cause in vertebrates and in insects. In the 
latter it appears to be a purely physical instinct, the 
direct result of an extraneous cause, and resembling 
the motions of a plant. In mammals and birds it 
is evident that violent emotion, and not the rough 
handling experienced, is the final cause of the 
swoon. 
Passing over venomous snakes, skunks, and a few 
other species in which the presence of danger excites 
only anger, fear has a powerful, and in some cases 
a disabling, effect on animals ; and it is this para- 
lyzing effect of fear on which the death-feigning 
instinct, found only in a few widely-separated species, 
has probably been built up by the slow cumulative 
process of natural selection. 
I have met with some curious instances of the 
paralyzing effect of fear. I was told by some hunters 
in an' outlying district of the pampas of its effect 
on a jaguar they started, and which took refuge in 
a dense clump of dry reeds. Though they could see 
it, it was impossible to throw the lasso over its head, 
and, after vainly trying to dislodge it, they at length 
set fire to the reeds. Still it refused to stir, but lay 
with head erect, fiercely glaring at them through the 
flames. Finally it disappeared from sight in the 
black smoke ; and when the fire had burnt itself out, 
it was found, dead and charred, in the same spot. 
On the pampas the gauchos frequently take the 
black-necked swan by frightening it. When the 
birds are feeding or resting on the grass, two or 
three men or boys on horseback go quietly to lee- 
