distinct, it is a fact well deserving attention, that Chinese and common
pigs have been repeatedly crossed in various manners, with unimpaired
fertility. One great breeder who had used pure Chinese pigs assured me that
the fertility of the half-breeds inter se and of their recrossed progeny
was actually increased; and this is the general belief of agriculturists.
Again, the Japan pig or S. pliciceps of Gray is so distinct in appearance
from all common pigs, that it stretches one's belief to the utmost to admit
that it is simply a domestic variety; yet this breed has been found
perfectly fertile with the Berkshire breed; and Mr. Eyton informs me that
he paired a half-bred brother and sister and found them quite fertile
together.

(FIGURE 3. HEAD OF WILD BOAR, AND OF "GOLDEN DAYS," a pig of the Yorkshire
Large Breed; the latter from a photograph. (Copied from Sidney's edition of
'The Pig' by Youatt.))

The modification of the skull in the most highly cultivated races is
wonderful. To appreciate the amount of change, Nathusius' work, with its
excellent figures, should be studied. The whole of the exterior in all its
parts has been altered: the hinder surface, instead of sloping backwards,
is directed forwards, entailing many changes in other parts; the front of
the head is deeply concave; the orbits have a different shape; the auditory
meatus has a different direction and shape; the incisors of the upper and
lower jaws do not touch each other, and they stand in both jaws beyond the
plane of the molars; the canines of the upper jaw stand in front of those
of the lower jaw, and this is a remarkable anomaly: the articular surfaces
of the occipital condyles are so greatly changed in shape, that, as
Nathusius remarks (s. 133), no naturalist, seeing this important part of
the skull by itself, would suppose that it belonged to the genus Sus. These
and various other modifications, as Nathusius observes, can hardly be