e peculiarity forms nought but ugliness, seeing it
violates the existing laws of symmetry." So Mr. Brent, in discussing the
merits of the sub-varieties of the Belgian canary-bird, remarks, "Fanciers
always go to extremes; they do not admire indefinite properties."[589]

This principle, which necessarily leads to divergence of character,
explains the present state of various domestic races. We can thus see how
it is that race-horses and dray-horses, greyhounds and mastiffs, which are
opposed to each other in every character,--how varieties so distinct as
Cochin-China fowls and bantams, or carrier-pigeons with very long beaks,
and tumblers with excessively short beaks, have been derived from the same
stock. As each breed is slowly improved, the inferior varieties are first
neglected and finally lost. In a few cases, by the aid of old records, or
from intermediate varieties still existing in countries where other
fashions have prevailed, we are enabled partially to trace the graduated
changes through which certain breeds have passed. Selection, whether
methodical or unconscious, always tending towards an extreme point,
together with the neglect and slow extinction of the intermediate and
less-valued forms, is the key which unlocks the mystery how man has
produced such wonderful results.

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In a few instances selection, guided by utility for a single purpose, has
led to convergence of character. All the improved and different races of
the pig, as Nathusius has well shown,[590] closely approach each other in
character, in their shortened legs and muzzles, their almost hairless,
large, rounded bodies, and small tusks. We see some degree of convergence
in the similar outline of the body in well-bred cattle belonging to
distinct races.[591] I know of no other such cases.

Continued divergence of character depends on, and is indeed a clear proof,
as previously remarked, of the same parts continuing to vary in the same
direction. The tendency to mere general variability or plasticity of
organisation can certainly be inherited, even from one parent, as has been
shown by Gaertner and Koelreuter, in the production of varying hybrids from
two species, of which one alone was variable. It is in itself probable
that, when an organ has varied in any manner, it will again vary in the
same manner, if the conditions which first caused the being to vary remain,
as far as can be judged, the same. This is either tacitly or expressly
ad