hen this is the case,
selection is almost sure to be practised to a certain extent. We shall
hereafter be enabled better to judge how far selection, when only
occasionally carried on, by a few of the inhabitants of a country, will
slowly produce a great effect.

In a well-known passage in the thirtieth chapter of Genesis, rules are
given for influencing, as was then thought possible, the colour of sheep;
and speckled and dark breeds are spoken of as being kept separate. By the
time of David the fleece was likened to snow. Youatt,[472] who has
discussed all the passages in relation to breeding in the Old Testament,
concludes that {202} at this early period "some of the best principles of
breeding must have been steadily and long pursued." It was ordered,
according to Moses, that "Thou shalt not let thy cattle gender with a
diverse kind;" but mules were purchased,[473] so that at this early period
other nations must have crossed the horse and ass. It is said[474] that
Erichthonius, some generations before the Trojan war, had many brood-mares,
"which by his care and judgment in the choice of stallions produced a breed
of horses superior to any in the surrounding countries." Homer (Book v.)
speaks of Aeneas's horses as bred from mares which were put to the steeds
of Laomedon. Plato, in his 'Republic,' says to Glaucus, "I see that you
raise at your house a great many dogs for the chase. Do you take care about
breeding and pairing them? Among animals of good blood, are there not
always some which are superior to the rest?" To which Glaucus answers in
the affirmative.[475] Alexander the Great selected the finest Indian cattle
to send to Macedonia to improve the breed.[476] According to Pliny,[477]
King Pyrrhus had an especially valuable breed of oxen; and he did not
suffer the bulls and cows to come together till four years old, that the
breed might not degenerate. Virgil, in his Georgics (lib. iii.), gives as
strong advice as any modern agriculturist could do, carefully to select the
breeding stock; "to note the tribe, the lineage, and the sire; whom to
reserve for husband of the herd;"--to brand the progeny;--to select sheep
of the purest white, and to examine if their tongues are swarthy. We have
seen that the Romans kept pedigrees of their pigeons, and this would have
been a senseless proceeding had not great care been taken in breeding them.
Columella gives detailed instructions about breeding fowls: "Let the
breeding hens