with its parent form, the wolf
or jackal." But when we examine the interval of mental power between one
of the lowest fishes, as a lamprey or a lancelet, and one of the higher
apes, and recognize the fact that this interval is filled up by
numberless gradations, it does not become so difficult to understand the
interval between an ape and man, which is not by far so great. As in
finding out what is peculiar to a living body in distinction to a body
not living, we found it absurd to take man as the perfection of the
animal scale--the microscopic monad possessing life as well as him--so
in the case of man's mental attributes, which have always been
increasing, always perfecting, since the first genuine man came into
existence, it would be equally absurd to compare the intellectual man of
to-day with an ape to see what attributes he possesses which the ape
does not possess; but if we go down in the scale and compare the savage
with the ape, the difficulty is not by far so great. It will be found
on close examination, though, that man and the higher animals,
especially the primates, have many instincts in common. "All," says
Darwin, "have the same senses, intuitions and sensations; similar
passions, affections, and emotions; even the more complex ones, such as
jealousy, suspicion, emulation, gratitude and magnanimity; they practice
deceit and are revengeful; they are sometimes susceptible to ridicule
and even have a sense of humor; they feel wonder and curiosity; they
possess the same faculties of imitation, attention, deliberation,
choice, memory, imagination, the association of ideas, and reason,
though in very different degrees. The individuals of the same species
graduate in intellect from absolute imbecility to high excellence; they
are also liable to insanity, though far less often than in the case of
man."[53] Nevertheless, in the face of these facts, many authors have
insisted that man is divided by an inseparable barrier from all the
lower animals in his mental faculties. It only shows the improper or
imperfect consideration of the subject they have under discussion.

It may be thought at first that some of the mental attributes mentioned
above are not possessed by animals. I therefore will briefly consider a
few of the more complex ones. We can dismiss the consideration of such
attributes as happiness, terror, suspicion, courage, timidity, jealousy,
shame, and wonder, as well-known attributes. _Curiosity_ in animal