offer no greater difficulty than
does does 1859 1860 1861 1866 1869 | do 1872 |
corporeal
structure structure 1859 1860 1861 1866 1869 | structures 1872 |
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
gradation gradation 1859 1860 1861 1869 1872 | graduation 1866 |
throws on the admirable architectural powers of the hive-bee. Habit no doubt
sometimes sometimes 1859 1860 1861 1866 1869 | often 1872 |
comes into play in modifying instincts; but it certainly is not indispensable, as we
see see 1869 1872 | see, 1859 1860 1861 1866 |
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
widely widely 1866 1869 1872 | considerably 1859 1860 1861 |
different conditions of life, yet
....... 1869 1872 | should 1859 1860 1861 1866 |
follow nearly the same instincts; why the
thrushes thrushes 1866 1869 1872 | thrush 1859 1860 1861 |
of
tropical and temperate South tropical and temperate South 1866 1869 1872 |
South 1859 1860 1861 |
America, for instance,
line line 1866 1869 1872 | lines 1859 1860 1861 |
their their 1866 1869 1872 | her 1859 1860 1861 |
nests nests 1866 1869 1872 | nest 1859 1860 1861 |
with mud like our British species. On the view of instincts having been slowly acquired through natural
selection, selection, 1869 1872 | selection 1859 1860 1861 1866 |
we need not marvel at some instincts being
apparently apparently 1859 1860 1861 1866 1869 | apparently 1872 |
not perfect and liable to mistakes, and at many instincts causing other animals to suffer. |
|
If species be only well-marked and permanent varieties, we can at once see why their crossed offspring should follow the same complex laws in their degrees and kinds of resemblance to their parents,— in being absorbed into each other by successive crosses, and in other such points,— as do the crossed offspring of acknowledged varieties.
This similarity This similarity 1869 1872 |
On the other hand, these 1859 1860 1861 1866 |
would be
a strange a strange 1869 1872 | strange 1859 1860 1861 1866 |
fact, fact, 1869 1872 | facts 1859 1860 1861 1866 |
if species
have have 1859 1860 1861 1866 1869 | had 1872 |
been independently
created created 1869 1872 | created, 1859 1860 1861 1866 |
and varieties
have have 1859 1860 1861 1866 1869 | had 1872 |
been produced
through through 1869 1872 | by 1859 1860 1861 1866 |
secondary laws. |
|
If we admit that the geological record is imperfect
|