0THE BREEDING PROBLEM.



qualities or characteristics, either mental or corporeal, psychological or
physical, in one generation, and the transmission of the same to
succeeding generations, and the increase, diminution or other modifica-
tion thereof in the offspring or descendants.
  The process here referred to embraces the operation of two forces,
which appear to be exactly opposite or antagonistic to each other-the
one a conservative force, and the other an aggressive or disturbing
force; or, as it has been well expressed, Heredity, which makes of
every individual the sum or essence or aggregation of that which
has lived before him-which opposes all change, all progress and all
improvement-the other, Evolution, which compels heredity to give
way to internal and external causes, and modifies both the physical
and mental organism, and places in the breeder's hands the means of
effecting desirable and valuable changes.
  Of these, heredity is unquestionably the stronger force, because, as we shall
see, when uniformity has once been established, the general principle that like
produces like finds very rarely an exception. In fact, the influence of heredity
is always present, and in the reproduction of animal life, never fails lo a.,sert
itself, in a greater or saJ degree. Every living thing brings forth young after
its own kind-in some cases the exact counterpart of the parent, and in others
slightly modified; but always showing more or less of the parent type. Men
do not gather grapes of thorns, nor figs of thistles, neither do Short-horn cows
bring forth buffalo calves, nor draft mares produce thoroughbred race-horses
Hence, although we may frequently meet with very apparent differences be-
tween the parents and the progeny, yet a moment's reflection will show its
that the points of resemblance are always very much greater than those of
difference.
  We are so accustomed to look at the operation of this law in its details, that
we overlook the aggregate of results. We mate a purely-bred Essex sow and
boar, and look upon it as a matter of course that the pigs produiced will all be
black, and possess the general characteristics of the Essex breed; but if,
having selected our breeding pair with a view to the transmission of a
peculiar form of the head or shape of the car, we find in the produce that few,
and possibly none possess the peculiarity which we have sought to perpetu-
ate, we are apt to lose faith in the power of heredity. And yet it would be an
argument against the uniform operation of this law were the product all to
possess the peculiarity which distinguished the sire and danll, for this was an
exceptional feature; and the fact that the pigs possessed, in lieu of this
peculiar mark, the character that belonged to their anc estors. in geneicral, is
rather a testimony to the inherent power of heredity than otherwise. Were
our pair of pure Essex swine to produce Poland-China or Berkshire or York-
shire pigs, there would be room for suspicion, and for complaint that the laws
of heredity had been violated; but such a transgression of Nature's law so
rarely occurs, that when it does tak" place, we may properly call the result a



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