acobins, and
still more plainly in runts, some varieties of which have their wings and
tail of great length, whilst others have both very short. With jacobins,
the remarkable length of the tail and {170} wing-feathers is not a
character which is intentionally selected by fanciers; but fanciers have
been trying for centuries, at least since the year 1600, to increase the
length of the reversed feathers on the neck, so that the hood may more
completely enclose the head; and it may be suspected that the increased
length of the wing and tail-feathers stands in correlation with the
increased length of the neck-feathers. Short-faced tumblers have short
wings in nearly due proportion with the reduced size of their bodies; but
it is remarkable, seeing that the number of the primary wing-feathers is a
constant character in most birds, that these tumblers generally have only
nine instead of ten primaries. I have myself observed this in eight birds;
and the Original Columbarian Society[311] reduced the standard for
bald-head tumblers from ten to nine white flight-feathers, thinking it
unfair that a bird which had only nine feathers should be disqualified for
a prize because it had not ten _white_ flight-feathers. On the other hand,
in carriers and runts, which have large bodies and long wings, eleven
primary feathers have occasionally been observed.

Mr. Tegetmeier has informed me of a curious and inexplicable case of
correlation, namely, that young pigeons of all breeds, which when mature
become white, yellow, silver (_i.e._ extremely pale blue), or dun-coloured,
are born almost naked; whereas other coloured pigeons are born well clothed
with down. Mr. Esquilant, however, has observed that young dun carriers are
not so bare as young dun barbs and tumblers. Mr. Tegetmeier has seen two
young birds in the same nest, produced from differently coloured parents,
which differed greatly in the degree to which they were at first clothed
with down.

I have observed another case of correlation which at first sight appears
quite inexplicable, but on which, as we shall see in a future chapter, some
light can be thrown by the law of homologous parts varying in the same
manner. The case is, that, when the feet are much feathered, the roots of
the feathers are connected by a web of skin, and apparently in correlation
with this the two outer toes become connected for a considerable space by
skin. I have observed this in very many {171} specimens