FIXEDNESS OF CHARACTER APPARENTLY NOT DUE TO ANTIQUITY OF
INHERITANCE--PREPOTENCY OF TRANSMISSION IN INDIVIDUALS OF THE SAME
FAMILY, IN CROSSED BREEDS AND SPECIES; OFTEN STRONGER IN ONE SEX THAN
THE OTHER; SOMETIMES DUE TO THE SAME CHARACTER BEING PRESENT AND
VISIBLE IN ONE BREED AND LATENT IN THE OTHER--INHERITANCE AS LIMITED BY
SEX--NEWLY-ACQUIRED CHARACTERS IN OUR DOMESTICATED ANIMALS OFTEN
TRANSMITTED BY ONE SEX ALONE, SOMETIMES LOST BY ONE SEX
ALONE--INHERITANCE AT CORRESPONDING PERIODS OF LIFE--THE IMPORTANCE OF
THE PRINCIPLE WITH RESPECT TO EMBRYOLOGY; AS EXHIBITED IN DOMESTICATED
ANIMALS; AS EXHIBITED IN THE APPEARANCE AND DISAPPEARANCE OF INHERITED
DISEASES; SOMETIMES SUPERVENING EARLIER IN THE CHILD THAN IN THE
PARENT--SUMMARY OF THE THREE PRECEDING CHAPTERS.

In the two last chapters the nature and force of Inheritance, the
circumstances which interfere with its power, and the tendency to
Reversion, with its many remarkable contingencies, were discussed. In the
present chapter some other related phenomena will be treated of, as fully
as my materials permit.

_Fixedness of Character._

It is a general belief amongst breeders that the longer any character has
been transmitted by a breed, the more firmly it will continue to be
transmitted. I do not wish to dispute the truth of the proposition, that
inheritance gains strength simply through long continuance, but I doubt
whether it can be proved. In one sense the proposition is little better
than a truism; if any character has remained constant during many
generations, it will obviously be little likely, the conditions of life
remaining the same, to vary during the next generation. So, again, in
improving a breed, if care be taken for a length of time to exclude all
inferior individuals, the breed will obviously tend to become truer, as it
will not have been crossed during many generations by an inferior animal.
We have previously seen, {63} but without being able to assign any cause,
that, when a new character appears, it is occasionally from the first well
fixed, or fluctuates much, or wholly fails to be transmitted. So it is with
the aggregate of slight differences which characterise a new variety, for
some propagate their kind from the first much truer than others. Even with
plants multiplied by bulbs, layers, &c., which may in one sense be said to
form parts of the same individual, it is well known that cer