if not useful to the possessor, will be saved as far as is possible,
may often have may often have 1869 |
will probably often 1859 1860 1861 1866 |
come into
play, play, 1869 | play; 1859 1860 1861 1866 |
and
aided in aided in 1869 |
this will tend to cause 1859 1860 1861 1866 |
the entire obliteration of a rudimentary organ. ↑7 blocks not present in 1859 1860 1861 1866 1869; present in 1872 | There remains, however, this difficulty.
After an organ has ceased being used, and has become in consequence much reduced, how can it be still further reduced in size until the merest vestige is left; and how can it be finally quite obliterated?
It is scarcely possible that disuse can go on producing any further effect after the organ has once been rendered functionless.
Some additional explanation is here requisite which I cannot give.
If, for instance, it could be proved that every part of the organisation tends to vary in a greater degree towards diminution than towards augmentation of size, then we should be able to understand how an organ which has become useless would be rendered, independently of the effects of disuse, rudimentary and would at last be wholly suppressed; for the variations towards diminished size would no longer be checked by natural selection.
The principle of the economy of growth, explained in a former chapter, by which the materials forming any part, if not useful to the possessor, are saved as far as is possible, will perhaps come into play in rendering a useless part rudimentary.
But this principle will almost necessarily be confined to the earlier stages of the process of reduction; for we cannot suppose that a minute papilla, for instance, representing in a male flower the pistil of the female flower, and formed merely of cellular tissue, could be further reduced or absorbed for the sake of economising nutriment.
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As the presence of As the presence of 1859 1860 1861 1866 1869 |
Finally, as 1872 |
rudimentary
organs organs 1859 1860 1861 1866 1869 | organs, 1872 |
is thus due to the tendency in every part of the organisation, which has long existed, to be is thus due to the tendency in every part of the organisation, which has long existed, to be 1859 1860 1861 1866 1869 |
by whatever steps they may have been degraded into their present useless condition, are the record of a former state of things, and have been retained solely through the power of 1872 |
inherited— inherited— 1859 1860 1861 1866 1869 | inheritance,— 1872 |
we can understand, on the genealogical view of classification, how it is that
systematists systematists 1859 1860 1861 1866 1869 | systematists, 1872 |
have have 1859 1860 1861 1866 1869 |
in placing organisms in their proper places in the natural system, have often 1872 |
found rudimentary parts as useful as, or even sometimes more useful than, parts of high physiological importance. Rudimentary organs may be compared with the letters in a word, still retained in the spelling, but become useless in the pronunciation, but which serve as a clue
....... 1869 1872 | in seeking 1859 1860 1861 1866 |
for its derivation. On the view of descent
with, with, 1869 | with 1859 1860 1861 1866 1872 |
modification, we may conclude that the existence of organs in a rudimentary, imperfect, and useless condition, or quite aborted, far from presenting a strange difficulty, as they assuredly do on the
ordinary ordinary 1859 1860 1861 1866 1869 | old 1872 |
doctrine of creation, might even have been
anticipated anticipated 1869 1872 | anticipated, 1859 1860 1861 1866 |
in accordance with the views here explained. in accordance with the views here explained. 1869 1872 |
and can be accounted for by the laws of inheritance. 1859 1860 1861 1866 |
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Summary
.
Summary
. 1869 1872 |
Summary
.—
1859 1860 1861 |
Summary
.
1866 |
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In this chapter I have attempted to show, that the
arrangement arrangement 1869 1872 | subordination 1859 1860 1861 1866 |
of
all organic beings all organic beings 1869 1872 |
group to group in all organisms 1859 1860 1861 |
group to group in all organic beings 1866 |
throughout all
time time 1869 1872 | time; 1859 1860 1861 1866 |
in group under group— that in group under group— that 1869 |
that 1859 1860 1861 1866 |
in groups under groups— that 1872 |
the nature of the
relationship, relationship, 1859 1860 1861 1866 1869 | relationships 1872 |
by which all living and extinct
organisms organisms 1866 1869 1872 | beings 1859 1860 1861 |
are united by complex, radiating, and circuitous lines of affinities
in a few grand classes,— in a few grand classes,— 1869 |
into one grand system; 1859 1860 1861 1866 |
into a few grand classes,— 1872 |
the rules followed and the difficulties encountered by naturalists in their
classifications,— classifications,— 1869 1872 | classifications; 1859 1860 1861 1866 |
the value set upon characters, if constant and prevalent, whether of high
or or 1869 |
vital importance, or of 1859 1860 1861 1866 |
or of 1872 |
the most trifling importance, or, as
with with 1869 1872 | in 1859 1860 1861 1866 |
rudimentary organs, of no
importance,— importance,— 1869 1872 | importance; 1859 1860 1861 1866 |
the wide opposition in value between analogical or adaptive characters, and characters of true affinity; and other
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