Comparison with 1860 |
|
importance in classification; why characters derived from rudimentary parts, though of no service to the being,
are often of high classificatory value; and why embryological characters are the
most valuable of all. The real affinities of all organic beings
are
due to inheritance or community of descent. The natural
system
is a genealogical arrangement, in which we have to discover the lines of descent
by the most
permanent characters,
however slight their
vital importance
may be. |
|
The framework
of bones being
the same in the
hand of a man, wing of a bat, fin of the
porpoise, and leg of the horse,— the same number of vertebræ forming the neck of the giraffe and of the elephant,— and innumerable other such facts, at once explain themselves on the theory of descent with slow and slight successive modifications. The similarity of pattern in the wing and leg
of a bat, though used for such different purpose,— in the jaws and legs of a crab,— in the petals, stamens, and pistils of a flower,
is likewise
intelligible
on the view of the gradual modification of parts or organs, which were alike in the
early progenitor of
each class. On the principle of successive variations not always supervening at an early age, and being inherited at a corresponding not early period of life, we can
clearly see why the embryos of mammals, birds, reptiles, and fishes should be
so closely alike,
and should be
so unlike the
adult forms. We may cease marvelling at the embryo of an air-breathing mammal
or bird having branchial slits and arteries running in loops, like those in
a fish which has to breathe the
air dissolved in water,
by the aid of well-developed branchiæ. |
|
Disuse, aided sometimes by natural selection, will
often tend to reduce an
organ,
when it has become useless by
changed habits or under changed
conditions
|
importance in classification; why characters derived from rudimentary parts, though of no service to the
being, being, 1859 1860 1861 1866 | beings, 1869 1872 |
are often of high classificatory value; and why embryological characters are
the the 1859 1860 1861 | often the 1866 1869 1872 |
most valuable of all. The real affinities of all organic
beings beings 1859 1860 1861 1866 | beings, 1869 1872 |
are are 1859 1860 1861 1866 |
in contradistinction to their adaptive resemblances, are 1869 1872 |
due to inheritance or community of descent. The
natural natural 1859 1860 1861 1866 | Natural 1869 1872 |
system system 1859 1860 1861 1866 | System 1869 1872 |
is a genealogical arrangement,
in which we have to discover the lines of descent in which we have to discover the lines of descent 1859 1860 1861 1866 |
with the acquired grades of dif- ference, marked 1869 |
with the acquired grades of difference, marked 1872 |
by the
most most 1859 1860 1861 1866 |
terms, varieties, species, genera, families, &c.; and we have to discover the lines of descent by the most 1869 1872 |
permanent
characters, characters, 1859 1860 1861 1866 | characters 1869 1872 |
however slight their however slight their 1859 1860 1861 1866 |
whatever they may be and of however slight 1869 1872 |
vital
importance importance 1859 1860 1861 1866 | importance. 1869 1872 |
may may 1859 1860 1861 1866 | may 1869 1872 |
be. be. 1859 1860 1861 1866 | be. 1869 1872 |
|
|
The
framework framework 1859 1860 1861 1866 | similar framework 1869 1872 |
of bones
being being 1859 1860 1861 1866 | in 1869 1872 |
the same in the the same in the 1859 1860 |
similar in the 1861 1866 |
the 1869 1872 |
hand of a man, wing of a bat, fin of
the the 1859 1860 1861 1866 1869 | a 1872 |
porpoise, and leg of the horse,— the same number of vertebræ forming the neck of the giraffe and of the elephant,— and innumerable other such facts, at once explain themselves on the theory of descent with slow and slight successive modifications. The similarity of pattern in the wing and
leg leg 1859 1860 1861 1866 |
in the leg 1869 1872 |
of a bat, though used for such different purpose,— in the jaws and legs of a crab,— in the petals, stamens, and pistils of a
flower, flower, 1859 1860 1861 1866 1869 | flower 1872 |
is
likewise likewise 1859 1860 1861 1866 1869 | likewise, 1872 |
intelligible intelligible 1859 1860 1861 1866 1869 |
to a large extent, intelligible 1872 |
on the view of the gradual modification of parts or organs, which were
alike in the alike in the 1859 1860 1861 1866 |
aboriginally alike in an 1869 1872 |
early progenitor
of of 1859 1860 1861 1866 | in 1869 1872 |
each
class. class. 1859 1860 1861 1866 |
of these classes. 1869 1872 |
On the principle of successive variations not always supervening at an early age, and being inherited at a corresponding not early period of life, we
can can 1859 1860 1861 | can 1866 1869 1872 |
clearly see why the embryos of mammals, birds, reptiles, and fishes
should be should be 1859 1860 1861 1872 | are 1866 1869 |
so closely
alike, alike, 1859 1860 1861 | similar, 1866 1869 1872 |
and
should be should be 1859 1860 1861 | are 1866 | should be 1869 1872 |
so unlike
the the 1859 1860 1861 1869 1872 | their 1866 |
adult forms. We may cease marvelling at the embryo of an air-breathing
mammal mammal 1859 1860 1861 1866 1872 | mammals 1869 |
or bird having branchial slits and arteries running in loops, like those
in in 1859 1860 1861 1866 | of 1869 1872 |
a fish which has to breathe
the the 1859 1860 1861 1866 1872 | the 1869 |
air dissolved in
water, water, 1859 1860 | water 1861 1866 1869 1872 |
by the aid of well-developed branchiæ. |
|
Disuse, aided sometimes by natural selection,
will will 1859 1860 1861 1866 1872 | has 1869 |
often
tend to reduce an tend to reduce an 1859 1860 1861 1866 |
reduced 1869 |
have reduced 1872 |
organ, organ, 1859 1860 1861 1866 | organs 1869 1872 |
when
it has become useless by it has become useless by 1859 1860 1861 1866 |
they have become useless under 1869 |
rendered useless under 1872 |
changed habits or
under changed under changed 1859 1860 1861 1866 | under changed 1869 1872 |
conditions
|