me that this is a
mistake. Moreover the _C. Guinea_ is characterized by the feathers of
the neck having peculiar notched tips,--a character not observed in any
domestic race. Fifthly, the _Columba oenas_ of Europe, which roosts on
trees, and builds its nest in holes, either in trees or the ground;
this species, as far as external characters go, might be the parent of
several domestic races; but, though it crosses readily with the true
rock-pigeon, the offspring, as we shall presently see, are sterile
hybrids, and of such sterility there is not a trace when the domestic
races are intercrossed. It should also be observed that if we were to
admit, against all probability, that any of the foregoing five or six
species were the parents of some of our domestic pigeons, not the least
light would be thrown on the chief differences between the eleven most
strongly-marked races.

We now come to the best known rock-pigeon, the _Columba livia_, which
is often designated in Europe pre-eminently as the Rock-pigeon, and
which naturalists believe to be the parent of all the domesticated
breeds. This bird agrees in every essential character with the breeds
which have been only slightly modified. It differs from all other
species in being of a slaty-blue colour, with two black bars on the
wings, and with the croup (or loins) white. Occasionally birds are seen
in Faroe and the Hebrides with the black bars replaced by two or three
black spots; this form has been named by Brehm[324] _C. amaliae_, but
this species has not been admitted as distinct by other ornithologists.
Graba[325] even found a difference between the wing-bars of the same
bird in Faroe. Another and rather more distinct form is either truly
wild or has become feral on the cliffs of England, and was doubtfully
named by Mr. Blyth[326] as _C. affinis_, but is now no longer
considered by him as a distinct species. _C. affinis_ is rather smaller
than the rock-pigeon of the Scottish islands, and has a very different
appearance owing to the wing-coverts being chequered with black, with
similar marks often extending over the back. The chequering consists of
a large black spot on the two sides, but chiefly on the outer side, of
each feather. The wing-bars in the true rock-pigeon and in the
chequered variety are, in fact, due to similar though larger s