. If proper tags are put on the blacks so as to distinguish
between the pure-blooded and the half-blooded--say a blue tag on the
hybrids and a black on the thoroughbreds--we shall get exactly the same
results as described in the case of the Andalusian fowl, in the six
cases mentioned. The same principles apply to qualities of the guinea
pigs other than color. Thus, if a long-haired guinea pig mates with a
short-haired guinea pig, all the offspring will be short-haired, because
short hair is dominant over long hair. Again, if a smooth-coated guinea
pig mates with a rough-coated one, the result will be rough coated,
because a rough coat is dominant over a smooth coat.

[Sidenote: "Thoroughbred" Humans]

The same principles undoubtedly apply to the human race, although as yet
only a few traits have been carefully studied. Eye color is one of
these. Imagine a marriage of a thoroughbred, black-eyed Italian with a
thoroughbred, blue-eyed Irish. What will be the result? All the children
will be black-eyed, black being dominant over blue; but these black eyes
are not the genuine article that the Italian parent possessed. They are
a blend, and it is only because the black element dominates over or
conceals the blue element that we can not see on the surface that there
is any blue there. But it may come out in the next generation; for, if
these half-blooded individuals marry among themselves one-quarter of
their children on the average will be blue-eyed. The other
three-quarters will be black-eyed, but only one-quarter will be "really
and truly" black-eyed, i.e., black-eyed like the Italian. The remaining
half are hybrid black, like the parents. It is only a sort of imitation
black so to speak.

The appearance of blue eyes in the second generation is the long
observed but formerly mysterious "atavism," or reversion to the
grandparent.

Suppose the children of an Italian and an Irish parent intermarry with
pure bred Italians. We immediately know what will be the result. All the
children will be black-eyed, but among a large number only half will be
thoroughbred black-eyed. The other half will be "imitation" black-eyed.
The case is just like the mating of hybrid black guinea pigs with
thoroughbred black guinea pigs, or of the blue fowl with the black.
Similarly, if the Irish-Italian hybrids marry with pure Irish, half the
offspring will be blue-eyed and half will be hybrid black-eyed.

[Sidenote: Dominants and Recessives]

B