rom nearly related species, follows according to Gaertner
the same laws. When two species are crossed, one has sometimes a prepotent
power of impressing its likeness on the hybrid; and so I believe it to be
with varieties of plants. With animals one variety certainly often has this
prepotent power over another variety. Hybrid plants produced from a
reciprocal cross, generally resemble each other closely; and so it is with
mongrels from a reciprocal cross. Both hybrids and mongrels can be reduced
to either pure parent-form, by repeated crosses in successive generations
with either parent.

These several remarks are apparently applicable to animals; but the subject
is here excessively complicated, partly owing to the existence of secondary
sexual characters; but more especially owing to prepotency in transmitting
likeness running more strongly in one sex than in the other, both when one
species is crossed with another, and when, one variety is crossed with
{275} another variety. For instance, I think those authors are right, who
maintain that the ass has a prepotent power over the horse, so that both
the mule and the hinny more resemble the ass than the horse; but that the
prepotency runs more strongly in the male-ass than in the female, so that
the mule, which is the offspring of the male-ass and mare, is more like an
ass, than is the hinny, which is the offspring of the female-ass and
stallion.

Much stress has been laid by some authors on the supposed fact, that
mongrel animals alone are born closely like one of their parents; but it
can be shown that this does sometimes occur with hybrids; yet I grant much
less frequently with hybrids than with mongrels. Looking to the cases which
I have collected of cross-bred animals closely resembling one parent, the
resemblances seem chiefly confined to characters almost monstrous in their
nature, and which have suddenly appeared--such as albinism, melanism,
deficiency of tail or horns, or additional fingers and toes; and do not
relate to characters which have been slowly acquired by selection.
Consequently, sudden reversions to the perfect character of either parent
would be more likely to occur with mongrels, which are descended from
varieties often suddenly produced and semi-monstrous in character, than
with hybrids, which are descended from species slowly and naturally
produced. On the whole I entirely agree with Dr. Prosper Lucas, who, after
arranging an enormous body of fact