the vertebrate animals form an ascending scale, more and more
approaching man's in their arrangement, the fact here finds its
explanation, that lower animals perform mental processes corresponding
in their nature to our own, though of generally less power and
complexity. The full evidence of this correspondence will be found in
such works as Brehm's _Thierleben_; and some of the salient points are
set forth by Charles Darwin, in the chapter on "Mental Powers," in his
_Descent of Man_. Such are the similar effects of terror on man and the
lower animals, causing the muscled to tremble, the heart to palpitate,
the sphincters to be relaxed, and the hair to stand on end. The
phenomena of memory, as to both persons and places, is strong in
animals, as is manifest by their recognition of their masters, and their
returning at once to habits of which, though disused for many years,
their brain has not lost the stored-up impressions. Such facts as that
dogs "hunt in dreams," make it likely that their minds are not only
sensible to actual events, present and past, but can, like our minds,
combine revived sensations into ideal scenes in which they are
actors,--that is to say, they have the faculty of imagination. As for
the reasoning powers in animals, the accounts of monkeys learning by
experience to break eggs carefully, and pick off bits of shell, so as
not to lose the contents, or of the way in which rats or martens after a
while can no longer be caught by the same kind of trap, with innumerable
similar facts, show in the plainest way that the reason of animals goes
so far as to form by new experience a new hypothesis of cause and effect
which will henceforth guide their actions. The employment of mechanical
instruments, of which instances of monkeys using sticks and stones
furnish the only rudimentary traces among the lower animals, is one of
the often-quoted distinctive powers of man. With this comes the whole
vast and ever-widening range of inventive and adaptive art, where the
uniform hereditary instinct of the cell-forming bee and the
nest-building bird is supplanted by multiform processes and
constructions, often at first rude and clumsy in comparison to those of
the lower instinct, but carried on by the faculty of improvement and new
invention into ever higher stages. "From the moment," writes A.R.
Wallace (_Natural Selection_), "when the first skin was used as a
covering, when the first rude spear was formed to assist in