ing immunity, is one of the greatest of the
many evidences of intelligent action on their part.[108] Letisimulation
(from _letum_, death, and _simulare_, to feign) is not confined to any
particular family, order, or species of animals, but exists in many,
from the very lowest to the highest. The habit of feigning death has
introduced a figure of speech in the English language, and has done much
to magnify and perpetuate the fame of the only marsupial found outside
of Australasia and the Malayan Archipelago. "Playing 'possum" is now a
synonym for certain kinds of deception. Man himself has known this to be
an efficacious stratagem on many occasions. I have only to recall the
numerous instances related by hunters who have feigned death, and have
then been abandoned by the animals attacking them. I have seen this
habit in some of the lowest animals known to science. Some time ago,
while examining the inhabitants of a drop of pond water under a
high-power lens, I noticed several rhizopods busily feeding on the
minute buds of an alga. These rhizopods suddenly drew in their hair-like
cilia and sank to the bottom, to all appearances dead. I soon discovered
the cause in the presence of a water-louse, an animal which feeds on
these animalcules. It likewise sank to the bottom, and, after examining
the rhizopods, swam away, evidently regarding them as dead and unfit for
food. The rhizopods remained quiet for several seconds, and then swam to
the alga and resumed feeding. This was not an accidental occurrence, for
several times since I have been fortunate enough to witness the same
wonderful performance. There were other minute animals swimming in the
drop of water, but the rhizopods fed on unconcernedly until the shark of
this microscopic sea appeared. They then recognized their danger at
once, and used the only means in their power to escape. Through the
agency of what sense did these little creatures discover the approach of
their enemies? Is it possible that they and other like microscopic
animals have eyes and ears so exceedingly small that lenses of the very
highest power cannot make them visible? Or are they possessors of
senses utterly unknown to and incapable of being appreciated by man?
Science can neither affirm nor deny either of these suppositions. The
fact alone remains that, through some sense, they discovered the
presence of the enemy, and feigned death in order to escape.

[108] Instinct does not preclude intellig