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. Really, we no more know the reason why the progeny
occasionally deviates from the parent than we do why it usually resembles
it. Though the laws and conditions governing variation are known to a
certain 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.

The common proposition is, that species reproduce their like; this is a
sort of general inference, only a degree closer to fact than the statement
that genera reproduce their like. The true proposition, the fact incapable
of further analysis, is, that individuals reproduce their like--that
characteristics are inheritable. So varieties, or deviations, once
originated, are perpetuable, like species. Not so likely to be perpetuated,
at the outset; for the new form tends to resemble a grandparent and a long
line of similar ancestors, as well as to resemble its immediate progenitors.
Two forces which coincide in the ordinary case, where the offspring
resembles its parent, act in different directions when it does not and it
is uncertain which will prevail. If the remoter but very potent ancestral
influence predominates, the variation disappears with the life of the
individual. If that of the immediate parent--feebler no doubt, but
closer--the variety survives in the offspring; whose progeny now has a
redoubled tendency to produce its own like; whose progeny again is almost
sure to produce its like, since it is much the same whether it takes after