Many consider the Javan bird as much handsomer than the common peacock, and it would be easy to suggest a score of improvements as regards either species.
The guinea-fowl is excused, as being "no general favourite, and scarcely more common than the peacock;" but Mr.Darwin himself shows and admits that it is a noteworthy instance of constancy under very varied conditions.
These instances alone (and there are yet others) seem sufficient to establish the assertion, that degree of change is different in different domestic animals.

It is, then, somewhat unwarrantable in any Darwinian to assume that _all_ wild animals have a capacity for change similar to that existing in _some_ of the domestic ones.

It seems more reasonable to assert the opposite, namely, that if, as Mr.Darwin says, the capacity for change is different in different domestic animals, it must surely be limited in those which have it least, and _a fortiori_ limited in wild animals.
Indeed, it cannot be reasonably maintained that wild species certainly vary as much as do domestic races; it is possible that they may do so, but at least this has not been yet shown.

Indeed, the much greater degree of variation amongst domestic animals than amongst wild ones is asserted over and over again by Mr.Darwin, and his assertions are supported by an overwhelming mass of facts and instances.
Of course, it may be asserted that a tendency to indefinite change exists in all cases, and that it is only the circumstances and conditions of {121} life which modify the effects of this tendency to change so as to produce such different results in different cases.

But assertion is not proof, and this assertion has not been proved.