ogether, that when one part varies other parts {224} vary at the same
time. When several breeds have once been formed, their intercrossing aids
the progress of modification, and has even produced new sub-breeds. But as,
in the construction of a building, mere stones or bricks are of little
avail without the builder's art, so, in the production of new races,
selection has been the presiding power. Fanciers can act by selection on
excessively slight individual differences, as well as on those greater
differences which are called sports. Selection is followed methodically
when the fancier tries to improve and modify a breed according to a
prefixed standard of excellence; or he acts unmethodically and
unconsciously, by merely trying to rear as good birds as he can, without
any wish or intention to alter the breed. The progress of selection almost
inevitably leads to the neglect and ultimate extinction of the earlier and
less improved forms, as well as of many intermediate links in each long
line of descent. Thus it has come to pass that most of our present races
are so marvellously distinct from each other, and from the aboriginal
rock-pigeon.

* * * * *

{225}

CHAPTER VII.

FOWLS.

BRIEF DESCRIPTIONS OF THE CHIEF BREEDS--ARGUMENTS IN FAVOUR OF THEIR
DESCENT FROM SEVERAL SPECIES--ARGUMENTS IN FAVOUR OF ALL THE BREEDS
HAVING DESCENDED FROM GALLUS BANKIVA--REVERSION TO THE PARENT-STOCK IN
COLOUR--ANALOGOUS VARIATIONS--ANCIENT HISTORY OF THE FOWL--EXTERNAL
DIFFERENCES BETWEEN THE SEVERAL BREEDS--EGGS--CHICKENS--SECONDARY
SEXUAL CHARACTERS--WING- AND TAIL-FEATHERS, VOICE, DISPOSITION,
ETC.--OSTEOLOGICAL DIFFERENCES IN THE SKULL, VERTEBRAE, ETC.--EFFECTS OF
USE AND DISUSE ON CERTAIN PARTS--CORRELATION OF GROWTH.

As some naturalists may not be familiar with the chief breeds of the fowl,
it will be advisable to give a condensed description of them.[361] From
what I have read and seen of specimens brought from several quarters of the
world, I believe that most of the chief kinds have been imported into
England, but many sub-breeds are probably still here unknown. The following
discussion on the origin of the various breeds and on their characteristic
differences does not pretend to completeness, but may be of some interest
to the naturalist. The classification of the breeds cannot, as far as I can
see, be made natural. They differ from each other in different