se characters
vary most which are now most valued and attended to by fanciers, and which
consequently are now being improved by continued selection. This is
indirectly admitted by fanciers when they complain that it is much more
difficult to breed high fancy pigeons up to the proper standard of
excellence than the so-called toy pigeons, which differ from {179} each
other merely in colour; for particular colours when once acquired are not
liable to continued improvement or augmentation. Some characters become
attached, from quite unknown causes, more strongly to the male than to the
female sex; so that we have, in certain races, a tendency towards the
appearance of secondary sexual characters,[315] of which the aboriginal
rock-pigeon displays not a trace.

* * * * *

{180}

CHAPTER VI.

PIGEONS--_continued_.

ON THE ABORIGINAL PARENT-STOCK OF THE SEVERAL DOMESTIC RACES--HABITS OF
LIFE--WILD RACES OF THE ROCK-PIGEON--DOVECOT-PIGEONS--PROOFS OF THE
DESCENT OF THE SEVERAL RACES FROM COLUMBA LIVIA--FERTILITY OF THE RACES
WHEN CROSSED--REVERSION TO THE PLUMAGE OF THE WILD
ROCK-PIGEON--CIRCUMSTANCES FAVOURABLE TO THE FORMATION OF THE
RACES--ANTIQUITY AND HISTORY OF THE PRINCIPAL RACES--MANNER OF THEIR
FORMATION--SELECTION--UNCONSCIOUS SELECTION--CARE TAKEN BY FANCIERS IN
SELECTING THEIR BIRDS--SLIGHTLY DIFFERENT STRAINS GRADUALLY CHANGE INTO
WELL-MARKED BREEDS--EXTINCTION OF INTERMEDIATE FORMS--CERTAIN BREEDS
REMAIN PERMANENT, WHILST OTHERS CHANGE--SUMMARY.

The differences described in the last chapter between the eleven chief
domestic races and between individual birds of the same race, would be of
little significance, if they had not all descended from a single wild
stock. The question of their origin is therefore of fundamental importance,
and must be discussed at considerable length. No one will think this
superfluous who considers the great amount of difference between the races,
who knows how ancient many of them are, and how truly they breed at the
present day. Fanciers almost unanimously believe that the different races
are descended from several wild stocks, whereas most naturalists believe
that all are descended from the _Columba livia_ or rock-pigeon.

Temminck[316] has well observed, and Mr. Gould has made the same remark to
me, that the aboriginal parent must have been a species which roosted and
built its nest on rocks; and I may ad