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The excerpt represents the core issue or deciding factor on which you must meditate, and is drawn from On the Origin of Species by Charles Darwin: branched off from their common progenitor, and subsequently have not varied
or come to differ in any degree, or only in a slight degree, it is not
probable that they should vary at the present day. On the other hand, the
points in which species differ from other species of the same genus, are
called specific characters; and as these specific characters have varied
and come to differ within the period of the branching off of the species
from a common progenitor, it is probable that they should still often be in
some degree variable,--at least more variable than those parts of the
organisation which have for a very long period remained constant.
In connexion with the present subject, I will make only two other remarks.
I think it will be admitted, without my entering on details, that secondary
On the Origin of Species |
