9HMKJM - The Complete Work of Charles Darwin Online

THE ORIGIN OF SPECIES. 29
great philosopher of horticulture, that variability under
domestication is somehow connected with excess of
food. He regards the unknown cause as acting chiefly
upon the reproductive system of the parents, which
system, judging from the effect of confinement or cultivation
upon its functions, he concludes to be more
susceptible than any other to the action of changed conditions
of life. The tendency to vary certainly appears
to be much stronger under domestication than in free
Nature. But we are not sure that the greater variable-
ness of cultivated races is not mainly owing to the
far greater opportunities for manifestation and accumulation—
a view seemingly all the more favorable to
Mr. Darwin's theory. The actual amount of certain
changes, such as size or abundance of fruit, size of
udder, stands of course in obvious relation to supply
of food.
Heally, we no more know the reason why the progeny
occasionally deviates from the parent than we do
the laws and
why it usually resembles it. Though
conditions governing variation are known to a cer-
tain extent, those governing inheritance are apparently
inscrutable.
"
Perhaps," Darwin "
remarks, the
correct way of viewing the whole subject would be, to
look at the inheritance of every character whatever as
the rule, and non-inheritance as the anomaly." This,
from general and obvious considerations, we have long
been accustomed to do. Now, as exceptional instances
are expected to be capable of explanation, while ultimate
laws are not, it is quite possible that variation
may be accounted for, while the great primary law of
inheritance remains a mysterious fact.