inary
selection,--and to variations in the same parts having been accumulated by
natural and sexual selection, and having been thus adapted for secondary
sexual, and for ordinary specific purposes. {159}

_Distinct species present analogous variations; and a variety of one
species often assumes some of the characters of an allied species, or
reverts to some of the characters of an early progenitor._--These
propositions will be most readily understood by looking to our domestic
races. The most distinct breeds of pigeons, in countries most widely apart,
present sub-varieties with reversed feathers on the head and feathers on
the feet,--characters not possessed by the aboriginal rock-pigeon; these
then are analogous variations in two or more distinct races. The frequent
presence of fourteen or even sixteen tail-feathers in the pouter, may be
considered as a variation representing the normal structure of another
race, the fantail. I presume that no one will doubt that all such analogous
variations are due to the several races of the pigeon having inherited from
a common parent the same constitution and tendency to variation, when acted
on by similar unknown influences. In the vegetable kingdom we have a case
of analogous variation, in the enlarged stems, or roots as commonly called,
of the Swedish turnip and Ruta baga, plants which several botanists tank as
varieties produced by cultivation from a common parent: if this be not so,
the case will then be one of analogous variation in two so-called distinct
species; and to these a third may be added, namely, the common turnip.
According to the ordinary view of each species having been independently
created, we should have to attribute this similarity in the enlarged stems
of these three plants, not to the _vera causa_ of community of descent, and
a consequent tendency to vary in a like manner, but to three separate yet
closely related acts of creation.

With pigeons, however, we have another case, namely, the occasional
appearance in all the breeds, of slaty-blue birds with two black bars on
the wings, a white {160} rump, a bar at the end of the tail, with the outer
feathers externally edged near their bases with white. As all these marks
are characteristic of the parent rock-pigeon, I presume that no one will
doubt that this is a case of reversion, and not of a new yet analogous
variation appearing in the several breeds. We may I think confidently come
to this conclusion,