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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 57 of 119 (4/p)
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05 - Laws of Variation 05-02 - Use and Disuse of Parts, combined with Natural Selection, Organs of Flight and Vision 40 The insects in Madeira which are not ground-feeders, and which, as certain flower-feeding coleoptera and lepidoptera, must habitually use their wings to gain their subsistence, have, as Mr. Wollaston suspects, their wings not at all reduced, but even enlarged. This is quite compatible with the action of natural selection.

insect
insect

Madeira
Madeira

coleoptera
coleoptera

lepidoptera
lepidoptera


For when a new insect first arrived on the island, the tendency of natural selection to enlarge or to reduce the wings, would depend on whether a greater number of individuals were saved by successfully battling with the winds, or by giving up the attempt and rarely or never flying.

island
island


As with mariners shipwrecked near a coast, it would have been better for the good swimmers if they had been able to swim still further, whereas it would have been better for the bad swimmers if they had not been able to swim at all and had stuck to the wreck.

shipwreck
shipwreck
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 05-02 - Use and Disuse of Parts, combined with Natural Selection, Organs of Flight and Vision 60 It is well known that several animals, belonging to the most different classes, which inhabit the caves of Carniola and of Kentucky, are blind. in some of the crabs the foot-stalk for the eye remains, though the eye is gone;- the stand for the telescope is there, though the telescope with its glasses has been lost.

cave
cave

Kentucky
Kentucky

crab
crab

telescope
telescope

glasses
glasses


As it is difficult to imagine that eyes, though useless, could be in any way injurious to animals living in darkness, their loss may be attributed to disuse. In one of the blind animals, namely, the cave-rat (Noetoma), two of which were captured by Professor Silliman at above half a mile distance from the mouth of the cave, and therefore not in the profoundest depths, the eyes were lustrous and of large size; and these animals, as I am informed by Professor Silliman, after having been exposed for about a month to a graduated light, acquired a dim perception of objects.
05 - Laws of Variation 05-02 - Use and Disuse of Parts, combined with Natural Selection, Organs of Flight and Vision 10 From the facts alluded to in the first chapter, I think there can be no doubt that use in our domestic animals has strengthened and enlarged certain parts, and disuse diminished them; and that such modifications are inherited.

Under free nature, we have no standard of comparison, by which to judge of the effects of long-continued use or disuse, for we know not the parent-forms; but many animals possess structures which can be best explained by the effects of disuse.

As Professor Owen has remarked, there is no greater anomaly in nature than a bird that cannot fly; yet there are several in this state.

fowl
fowl


The logger-headed duck of South America can only flap along the surface of the water, and has its wings in nearly the same condition as the domestic Aylesbury duck: it is a remarkable fact that the young birds, according to Mr. Cunningham, can fly, while the adults have lost this power.

ducks
ducks

South America
South America


As the larger ground-feeding birds seldom take flight except to escape danger, it is probable that the nearly wingless condition of several birds, now inhabiting or which lately inhabited several oceanic islands, tenanted by no beast of prey, has been caused by disuse.

island
island


The ostrich indeed inhabits continents, and is exposed to danger from which it cannot escape by flight, but it can defend itself by kicking its enemies, as efficiently as many quadrupeds.

ostrich
ostrich


We may believe that the progenitor of the ostrich genus had habits like those of the bustard, and that, as the size and weight of its body were increased during successive generations, its legs were used more, and its wings less, until they became incapable of flight.

bustard
bustard