hey could with reasonable certainty be regarded as
pure dominants. But to ensure that no horned calves should come, it is
enough to use a bull which is pure for that character. This can easily be
tested by crossing him with a dozen or so horned cows. If he gets no horned
calves out of these he may be regarded as a pure dominant and thenceforward
put to his own cows, whether horned or polled, with the certainty that all
his calves will be polled. {167}

Or, again, suppose that a breeder has a chestnut mare and wishes to make
certain of a bay foal from her. We know that bay is dominant to chestnut,
and that if a homozygous bay stallion is used a bay foal must result. In
his choice of a sire, therefore, the breeder must be guided by the previous
record of the animal, and select one that has never given anything but bays
when put to either bay or chestnut mares. In this way he will assure
himself of a bay foal from his chestnut mare, whereas if the record of the
sire shows that he has given chestnuts he will be heterozygous, and the
chances of his getting a bay or a chestnut out of a chestnut mare are
equal.

It is not impossible that the breeder may be unwilling to test his animals
by crossing them with a different breed through fear that their purity may
be thereby impaired, and that the influence of the previous cross may show
itself in succeeding generations. He might hesitate, for instance, to test
his polled cows by crossing them with a horned bull for fear of getting
horned calves when the cows were afterwards put to a polled bull of their
own breed. The belief in the power of a sire to influence subsequent
generations, or telegony as it is sometimes called, is not uncommon even
to-day. Nevertheless, carefully conducted experiments by more than one
competent observer have failed to elicit a single shred of unequivocal
evidence in favour of the view. Until we have evidence based upon
experiments which are capable of {168} repetition, we may safely ignore
telegony as a factor in heredity.

Heterozygous forms play a greater part in the breeding of animals than of
plants, for many of the qualities sought after by the breeder are of this
nature. Such is the blue of the Andalusian fowl, and, according to
Professor Wilson, the roan of the Shorthorn is similar, being the
heterozygous form produced by mating red with white. The characters of
certain breeds of canaries and pigeons again appear to depend upon their
heterozygo