seven puppies; four
were marked with blue and white, which is so unusual a colour with pointers
that she was thought to have played false with one of the greyhounds, and
the whole litter was condemned; but the gamekeeper was permitted to save
one as a curiosity. Two years afterwards a friend of the owner saw the
young dog, and declared that he was the image of his old pointer-bitch
Sappho, the only blue and white pointer of pure descent which he had ever
seen. This led to close inquiry, and it was proved that he was the
great-great-grandson of Sappho; so that, according to the common
expression, he had only 1-16th of her blood in his veins. Here it can
hardly be doubted that a character derived from a cross with an individual
of the same variety reappeared after passing over three generations.

{35}

When two distinct races are crossed, it is notorious that the tendency in
the offspring to revert to one or both parent-forms is strong, and endures
for many generations. I have myself seen the clearest evidence of this in
crossed pigeons and with various plants. Mr. Sidney[81] states that, in a
litter of Essex pigs, two young ones appeared which were the image of the
Berkshire boar that had been used twenty-eight years before in giving size
and constitution to the breed. I observed in the farmyard at Betley Hall
some fowls showing a strong likeness to the Malay breed, and was told by
Mr. Tollet that he had forty years before crossed his birds with Malays;
and that, though he had at first attempted to get rid of this strain, he
had subsequently given up the attempt in despair, as the Malay character
would reappear.

This strong tendency in crossed breeds to revert has given rise to endless
discussions in how many generations after a single cross, either with a
distinct breed or merely with an inferior animal, the breed may be
considered as pure, and free from all danger of reversion. No one supposes
that less than three generations suffices, and most breeders think that
six, seven, or eight are necessary, and some go to still greater
lengths.[82] But neither in the case of a breed which has been contaminated
by a single cross, nor when, in the attempt to form an intermediate breed,
half-bred animals have been matched together during many generations, can
any rule be laid down how soon the tendency to reversion will be
obliterated. It depends on the difference in the strength or prepotency of
transmission in the two parent