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therefore these same characters would be more likely
to
than the generic characters which have been inherited without change for an
period. It is inexplicable on the theory of creation why a part developed in a very unusual manner in
one species
a genus, and therefore, as we may naturally infer, of great importance to
species, should be eminently liable to variation; but, on
view, this part has
since the several species branched off from a common progenitor, an unusual amount of variability and modification, and therefore we might expect
part generally to be still variable. But a part may be developed in the most unusual manner, like the wing of a bat, and yet not be more variable than any other structure, if the part be common to many subordinate forms, that is, if it has been inherited for a very long period; for in this case it will have been rendered constant by long-continued natural selection. |
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| Glancing at instincts, marvellous as some are, they offer no greater difficulty than
corporeal
on the theory of the natural selection of successive, slight, but profitable modifications. We can thus understand why nature moves by graduated steps in endowing different animals of the same class with their several instincts. I have attempted to show how much light the principle of
throws on the admirable architectural powers of the hive-bee. Habit no doubt
comes into play in modifying instincts; but it certainly is not indispensable, as we
in the case of neuter insects, which leave no progeny to inherit the effects of long-continued habit. On the view of all the species of the same genus having descended from a common parent, and having inherited much in common, we can understand how it is that allied species, when placed under
different conditions of life,
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