; of sleep, and
the distinctions of sex. The accurate knowledge which Aristotle exhibits
of the anatomy and habits of marine animals, such as the Cephalopoda and
the larger Crustacea, leaves no doubt that he derived it from actual
observation. Professor Owen says, "Respecting the living habits of the
Cephalopoda, Aristotle is more rich in detail than any other zoological
author." What is now spoken of as the _hectocotylization_ of one or more
of the arms of the male cephalopod did not escape Aristotle's eye. And
while he speaks of the teeth and that which serves these animals for a
tongue, it is plain from the context that he means in the one case the
two halves of the parrot-like beak, and in the other the anterior end of
the odontophore.

Books five to seven deal with the subject of generation.

The eighth book contains a variety of details respecting animals, their
food, migrations, hibernation, and diseases; with the influence of
climate and locality upon them.

The ninth book describes the habits and instincts of animals. The
details are interesting; but there is, as usual, very little attempt at
classification. Disjointed statements and sudden digressions occur, the
subjects being treated in the order in which they presented themselves
to the author. Such curious statements as the following are met with:
"The raven is an enemy to the bull and the ass, for it flies round them
and strikes their eyes." "If a person takes a goat by the beard, all the
rest of the herd stand by, as if infatuated, and look at it." "Female
stags are captured by the sound of the pipe and by singing. When two
persons go out to capture them, one shows himself, and either plays upon
a pipe or sings, and the other strikes behind, when the first gives him
the signal." "Swans have the power of song, especially when near the end
of their life; for they then fly out to sea, and some persons sailing
near the coast of Libya have met many of them in the sea singing a
mournful song, and have afterwards seen some of them die." "Of all wild
animals, the elephant is the most tame and gentle; for many of them are
capable of instruction and intelligence, and they have been taught _to
worship the king_."

In the work "On the Parts of Animals," the author considers not only the
phenomena of life exhibited by each species, but also the cause or
causes to which these phenomena are attributable. After a general
introduction, he proceeds to enumerate the thr