The Origin of Species by Means of Natural Selection: Or, the Preservation of Favoured Races in the Struggle for Life, 6th EditionDarwin, Charles
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The Origin of Species by Means of Natural Selection: Or, the Preservation of Favoured Races in the Struggle for Life, 6th Edition
Darwin, Charles
Evolution (Biology); Natural selection
The results of the various, unknown, or but dimly understood laws of
variation are infinitely complex and diversified. It is well worth
while carefully to study the several treatises on some of our old
cultivated plants, as on the hyacinth, potato, even the dahlia, &c.;
and it is really surprising to note the endless points of structure and
constitution in which the varieties and sub-varieties differ slightly
from each other. The whole organisation seems to have become plastic,
and departs in a slight degree from that of the parental type.
Any variation which is not inherited is unimportant for us. But the
number and diversity of inheritable deviations of structure, both those
of slight and those of considerable physiological importance, are
endless. Dr. Prosper Lucas’ treatise, in two large volumes, is the
fullest and the best on this subject. No breeder doubts how strong is
the tendency to inheritance; that like produces like is his fundamental
belief: doubts have been thrown on this principle only by theoretical
writers. When any deviation of structure often appears, and we see it
in the father and child, we cannot tell whether it may not be due to
the same cause having acted on both; but when among individuals,
apparently exposed to the same conditions, any very rare deviation, due
to some extraordinary combination of circumstances, appears in the
parent—say, once among several million individuals—and it reappears in
the child, the mere doctrine of chances almost compels us to attribute
its reappearance to inheritance. Every one must have heard of cases of
albinism, prickly skin, hairy bodies, &c., appearing in several members
of the same family. If strange and rare deviations of structure are
truly inherited, less strange and commoner deviations may be freely
admitted to be inheritable. Perhaps 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.
Public-domain text, read in full here on John Shaqi.
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