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OriginOfSpecies - 475 Rows
Column Type #Values Column Stats
id int(11) 475 Column Stats
subject varchar(80) 14 Column Stats
title varchar(250) 139 Column Stats
ordinal int(11) 30 Column Stats
description text 474 Column Stats

475 rows, page 35 of 119 (4/p)
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Export to Excel select * from OriginOfSpecies order by ordinal desc limit 136, 4 (Page 35: Row)
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05 - Laws of Variation 05-02 - Use and Disuse of Parts, combined with Natural Selection, Organs of Flight and Vision 50 The eyes of moles and of some burrowing rodents are rudimentary in size, and in some cases are quite covered by skin and fur.

mole
mole


This state of the eyes is probably due to gradual reduction from disuse, but aided perhaps by natural selection.

In South America, a burrowing rodent, the tucotuco, or Ctenomys, is even more subterranean in its habits than the mole; and I was assured by a Spaniard, who had often caught them, that they were frequently blind.
tucotuco
tucotuco

South America
South America


One which I kept alive was certainly in this condition, the cause, as appeared on dissection, having been inflammation of the nictitating membrane.

As frequent inflammation of the eyes must be injurious to any animal, and as eyes are certainly not necessary to animals having subterranean habits, a reduction in their size, with the adhesion of the eyelids and growth of fur over them, might in such case be an advantage; and if so, natural selection would aid the effects of disuse.
05 - Laws of Variation 05-04 - Correlation of Growth 50 With respect to the development of the corolla, Sprengel's idea that the ray-florets serve to attract insects, whose agency is highly advantageous or necessary for the fertilisation of these plants, is highly probable; and if so, natural selection may have come into play.

But with respect to the seeds, it seems impossible that their differences in shape, which are not always correlated with any difference in the corolla, can be in any way beneficial: yet in the Umbelliferae these differences are of such apparent importance- the seeds being sometimes orthospermous in the exterior flowers and coelospermous in the central flowers,- that the elder De Candolle founded his main divisions in the order on such characters.

umbelliferae
umbelliferae

Alphonse de Candolle
Alphonse de Candolle


Hence modifications of structure, viewed by systematists as of high value, may be wholly due to the laws of variation and correlation, without being, as far as we can judge, of the slightest service to the species.
06 - Difficutiles in Theory 06-04 - Transitions in Habits of Life 50 If about a dozen genera of birds were to become extinct, who would have ventured to surmise that birds might have existed which used their wings solely as flappers, like the logger-headed duck (Micropterus of Eyton); as fins in the water and as front-legs on the land, like the penguin; as sails, like the ostrich; and functionally for no purpose, like the Apteryx?

duck
duck

penguin
penguin

ostrich
ostrich

apteryx
apteryx


Yet the structure of each of these birds is good for it, under the conditions of life to which it is exposed, for each has to live by a struggle; but it is not necessarily the best possible under all possible conditions.

It must not be inferred from these remarks that any of the grades of wing-structure here alluded to, which perhaps may all be the result of disuse, indicate the steps by which birds actually acquired their perfect power of flight; but they serve to show what diversified means of transition are at least possible.
06 - Difficutiles in Theory 06-07 - Organs of extreme Perfection 50 It is scarcely possible to avoid comparing the eye with a telescope.
telescope
telescope


We know that this instrument has been perfected by the long-continued efforts of the highest human intellects; and we naturally infer that the eye has been formed by a somewhat analogous process.

But may not this inference be presumptuous? Have we any right to assume that the Creator works by intellectual powers like those of man?
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If we must compare the eye to an optical instrument, we ought in imagination to take a thick layer of transparent tissue, with spaces filled with fluid, and with a nerve sensitive to light beneath, and then suppose every part of this layer to be continually changing slowly in density, so as to separate into layers of different densities and thicknesses, placed a different distances from each other, and with the surfaces of each layer slowly changing in form.

Further we must suppose that there is a power, represented by natural selection or the survival of the fittest, always intently watching each slight alteration in the transparent layers; and carefully preserving each which, under varied circumstances, in any way or in any degree, tends to produce a distincter image.

We must suppose each new state of the instrument to be multiplied by the million; each to be preserved until a better one is produced, and then the old ones to be all destroyed.

In living bodies, variation will cause the slight alterations, generation will multiply them almost infinitely, and natural selection will pick out with unerring skill each improvement.

Let this process go on for millions of years; and during each year on millions of individuals of many kinds; and may we not believe that a living optical instrument might thus be formed as superior to one of glass, as the works of the Creator are to those of man?