one another on the approach of a bird of prey. Horses and cattle
that come from countries where there are no lions become unquiet and
display alarm as soon as they are aware that a lion is approaching
them in the night. Horses going along a bridle-path that used to
leave the town at the back of the old dens of the carnivora in the
Berlin Zoological Gardens were often terrified by the propinquity of
enemies who were entirely unknown to them. Sticklebacks will swim
composedly among a number of voracious pike, knowing, as they do,
that the pike will not touch them. For if a pike once by mistake
swallows a stickleback, the stickleback will stick in its throat by
reason of the spine it carries upon its back, and the pike must
starve to death without being able to transmit his painful experience
to his descendants. In some countries there are people who by choice
eat dog's flesh; dogs are invariably savage in the presence of these
persons, as recognising in them enemies at whose hands they may one
day come to harm. This is the more wonderful inasmuch as dog's fat
applied externally (as when rubbed upon boots) attracts dogs by its
smell. Grant saw a young chimpanzee throw itself into convulsions of
terror at the sight of a large snake; and even among ourselves a
Gretchen can often detect a Mephistopheles. An insect of the genius
bombyx will seize another of the genus parnopaea, and kill it
wherever it finds it, without making any subsequent use of the body;
but we know that the last-named insect lies in wait for the eggs of
the first, and is therefore the natural enemy of its race. The
phenomenon known to stockdrivers and shepherds as "das Biesen des
Viehes" affords another example. For when a "dassel" or "bies" fly
draws near the herd, the cattle become unmanageable and run about
among one another as though they were mad, knowing, as they do, that
the larvae from the eggs which the fly will lay upon them will
presently pierce their hides and occasion them painful sores. These