seriously affected, and their
descendants are highly variable.

But to return to our comparison of mongrels and hybrids: Gartner states
that mongrels are more liable than hybrids to revert to either parent
form; but this, if it be true, is certainly only a difference in degree.
Moreover, Gartner expressly states that the hybrids from long cultivated
plants are more subject to reversion than hybrids from species in their
natural state; and this probably explains the singular difference in
the results arrived at by different observers. Thus Max Wichura doubts
whether hybrids ever revert to their parent forms, and he experimented
on uncultivated species of willows, while Naudin, on the other hand,
insists in the strongest terms on the almost universal tendency to
reversion in hybrids, and he experimented chiefly on cultivated plants.
Gartner further states that when any two species, although most closely
allied to each other, are crossed with a third species, the hybrids are
widely different from each other; whereas if two very distinct varieties
of one species are crossed with another species, the hybrids do not
differ much. But this conclusion, as far as I can make out, is founded
on a single experiment; and seems directly opposed to the results of
several experiments made by Kolreuter.

Such alone are the unimportant differences which Gartner is able to
point out between hybrid and mongrel plants. On the other hand, the
degrees and kinds of resemblance in mongrels and in hybrids to their
respective parents, more especially in hybrids produced from nearly
related species, follow, according to Gartner the same laws. When two
species are crossed, one has sometimes a prepotent power of impressing
its likeness on the hybrid. So I believe it to be with varieties of
plants; and 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 mongrel
plants 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 much 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 wh