and crossing them with a well-known stock, to produce almost any trait or
quality that he desires. This law makes it possible to estimate the results
of cross breeding with almost mathematical exactness. Improved varieties of
fruits, grains and vegetables have been produced in this manner, and with
animals marvelous results have been achieved.

Luther Burbank, in his little book, "The Training of the Human Plant,"
says: "There is not a single desirable attribute which, lacking in a
plant, may not be bred into it. Choose what improvement you wish in a
flower, a fruit, or a tree, and by crossing, selection, cultivation and
persistence, you can fix this desirable trait irrevocably." And further:
"If then we could have twelve families under ideal conditions where these
principles could be carried out unswervingly, we could accomplish more for
the race in ten generations than can now be accomplished in a hundred
thousand years. Ten generations of human life should be ample to fix any
desired attribute. This is absolutely clear, there is neither theory nor
speculation."

_Acquirements of parents_ during their lifetime, according to the best
authorities, are not transmitted to any noticeable extent to their
children. This appears to be due to the fact that the cells concerned in
reproduction are set aside during embryonic life and from then on are
practically unmodified by the succeeding development and experiences of the
parent. In fact, during the lifetime of the individual, the germ cells are
so completely isolated from the growing organism that nothing but
nourishment in the shape of blood can possibly reach them, hence they can
be affected only by a vitiated or poisonous blood supply. It seems to be
true, therefore, that only the old, deeply-impressed traits, capacities,
or racial characters can be inherited. This is, no doubt, the chief secret
of the power of heredity to breed true.