jackal; and that the mule, in each
case, would breed again with the dog. In these cases, however, it may be
observed, that there was always one parent at least of pure breed, and
no proof was obtained that a true hybrid race could be perpetuated; a
fact of which I believe no examples are yet recorded, either in regard
to mixtures of the horse and ass, or any other of the mammalia.

Should the fact be hereafter ascertained, that two mules can propagate
their kind, we must still inquire whether the offspring may not be
regarded in the light of a monstrous birth, proceeding from some
accidental cause, or, rather, to speak more philosophically, from some
general law not yet understood, but which may not be permitted
permanently to interfere with those laws of generation by which species
may, in general, be prevented from becoming blended. If, for example, we
discovered that the progeny of a mule race degenerated greatly, in the
first generation, in force, sagacity, or any attribute necessary for its
preservation in a state of nature, we might infer that, like a monster,
it is a mere temporary and fortuitous variety. Nor does it seem probable
that the greater number of such monsters could ever occur unless
obtained by art; for, in Hunter's experiments, stratagem or force was,
in most instances, employed to bring about the irregular connexion.[827]

_Mules not strictly intermediate between the parent species._--It seems
rarely to happen that the mule offspring is truly intermediate in
character between the two parents. Thus Hunter mentions that, in his
experiments, one of the hybrid pups resembled the wolf much more than
the rest of the litter; and we are informed by Wiegmann, that, in a
litter lately obtained in the Royal Menagerie at Berlin, from a white
pointer and a she-wolf, two of the cubs resembled the common wolf-dog,
but the third was like a pointer with hanging ears.

There is undoubtedly a very close analogy between these phenomena and
those presented by the intermixture of distinct races of the same
species, both in the inferior animals and in man. Dr. Prichard, in his
"Physical History of Mankind," cites examples where the peculiarities of
the parents have been transmitted very unequally to the offspring; as
where children, entirely white, or perfectly black, have sprung from the
union of the European and the negro. Sometimes the colour or other
peculiarities of one parent, after having failed to show themselves