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History of Animals   

All animals move alike, four-footed and many-footed; in other
words, they all move cross-corner-wise. And animals in general have
two feet in advance; the crab alone has four.

Very extensive genera of animals, into which other subdivisions
fall, are the following: one, of birds; one, of fishes; and another,
of cetaceans. Now all these creatures are blooded.
There is another genus of the hard-shell kind, which is called
oyster; another of the soft-shell kind, not as yet designated by a
single term, such as the spiny crawfish and the various kinds of crabs
and lobsters; and another of molluscs, as the two kinds of calamary
and the cuttle-fish; that of insects is different. All these latter
creatures are bloodless, and such of them as have feet have a goodly
number of them; and of the insects some have wings as well as feet.
Of the other animals the genera are not extensive. For in them
one species does not comprehend many species; but in one case, as man,
the species is simple, admitting of no differentiation, while other
cases admit of differentiation, but the forms lack particular
So, for instance, creatures that are qudapedal and unprovided
with wings are blooded without exception, but some of them are
viviparous, and some oviparous. Such as are viviparous are
hair-coated, and such as are oviparous are covered with a kind of
tessellated hard substance; and the tessellated bits of this substance
are, as it were, similar in regard to position to a scale.
An animal that is blooded and capable of movement on dry land,
but is naturally unprovided with feet, belongs to the serpent genus;
and animals of this genus are coated with the tessellated horny
substance. Serpents in general are oviparous; the adder, an
exceptional case, is viviparous: for not all viviparous animals are
hair-coated, and some fishes also are viviparous.
All animals, however, that are hair-coated are viviparous. For,
by the way, one must regard as a kind of hair such prickly hairs as
hedgehogs and porcupines carry; for these spines perform the office of
hair, and not of feet as is the case with similar parts of
In the genus that combines all viviparous quadrupeds are many
species, but under no common appellation. They are only named as it
were one by one, as we say man, lion, stag, horse, dog, and so on;
though, by the way, there is a sort of genus that embraces all
creatures that have bushy manes and bushy tails, such as the horse,
the ass, the mule, the jennet, and the animals that are called Hemioni
in Syria,-from their externally resembling mules, though they are
not strictly of the same species. And that they are not so is proved
by the fact that they mate with and breed from one another. For all
these reasons, we must take animals species by species, and discuss
their peculiarities severally'
These preceding statements, then, have been put forward thus in a
general way, as a kind of foretaste of the number of subjects and of
the properties that we have to consider in order that we may first get
a clear notion of distinctive character and common properties. By
and by we shall discuss these matters with greater minuteness.
After this we shall pass on to the discussion of causes. For to do
this when the investigation of the details is complete is the proper
and natural method, and that whereby the subjects and the premisses of
our argument will afterwards be rendered plain.
In the first place we must look to the constituent parts of
animals. For it is in a way relative to these parts, first and
foremost, that animals in their entirety differ from one another:
either in the fact that some have this or that, while they have not
that or this; or by peculiarities of position or of arrangement; or by
the differences that have been previously mentioned, depending upon
diversity of form, or excess or defect in this or that particular,

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