has the feeblest power of
transmitting its two chief characteristic qualities.

I will give one other instance with fowls and pigeons of weakness and
strength in the transmission of the same character to their crossed
offspring. The Silk-fowl breeds true, and there is reason to believe is
a very ancient race; but when I reared a large number of mongrels from
a Silk-hen by a Spanish cock, not one exhibited even a trace of the
so-called silkiness. Mr. Hewitt also asserts that in no instance are
the silky feathers transmitted by this breed when crossed with any
other variety. But three birds out of many raised by Mr. Orton from a
cross between a silk-cock and a bantam-hen, had silky feathers.[148] So
that it is certain that this breed very seldom has the power of
transmitting its peculiar plumage to its crossed progeny. On the other
hand, there is a silk sub-variety of the fantail pigeon, which has its
feathers in nearly the same state as in the Silk-fowl: now we have
already seen that fantails, when crossed, possess singularly weak power
in transmitting their general qualities; but the silk sub-variety when
crossed with any other small-sized race invariably transmits its silky
feathers![149]

The law of prepotency comes into action when species are crossed, as
with races and individuals. Gaertner has unequivocally shown[150] that
this is the case with plants. To give one instance: when _Nicotiana
paniculata_ and _vincaeflora_ are crossed, the character of _N.
paniculata_ is almost completely lost in the hybrid; but if _N.
quadrivalvis_ be crossed with _N. vincaeflora_, this later species,
which was before so prepotent, now in its turn almost disappears under
the power of _N. quadrivalvis_. It is remarkable that the prepotency of
one species over another in transmission is quite independent, as shown
by Gaertner, of the greater or less facility with which the one
fertilises the other.

With animals, the jackal is prepotent over the dog, as is stated by
Flourens who made many crosses between these animals; and this was
likewise the case with a hybrid which I once saw between a jackal and
terrier. I cannot doubt, from the observations of Colin and others,
that the ass is prepotent over the horse; the prepotency in this
instance running more strongly through the male than through the fem