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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 2 of 119 (4/p)
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01 - Variations Under Domestication 01-01 - Causes of Variability 25 With respect to what I have called the indirect action of changed conditions, namely, through the reproductive system of being affected, we may infer that variability is thus induced, partly from the fact of this system being extremely sensitive to any change in the conditions, and partly from the similarity, as Kreuter and others have remarked, between the variability which follows from the crossing of distinct species, and that which may be observed with plants and animals when reared under new or unnatural conditions.

Many facts clearly show how eminently susceptible the reproductive system is to very slight changes in the surrounding conditions.

Nothing is more easy than to tame an animal, and few things more difficult than to get it to breed freely under confinement, even when the male and female unite.

How many animals there are which will not breed, though kept in an almost free state in their native country!

This is generally, but erroneously, attributed to vitiated instincts.

Many cultivated plants display the utmost vigour, and yet rarely or never seed! In some few cases it has been discovered that a very trifling change, such as a little more or less water at some particular period of growth, will determine whether or not a plant will produce seeds.
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I cannot here give the details which I have collected and elsewhere published on this curious subject; but to show how singular the laws are which determine the reproduction of animals under confinement, I may mention that carnivorous animals, even from the tropics, breed in this country pretty freely under confinement, with the exception of the plantigrades or bear family, which seldom produce young; whereas carnivorous birds, with the rarest exceptions, hardly ever lay fertile eggs.
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Many exotic plants have pollen utterly worthless, in the same condition as in the most sterile hybrids.

When, on the one hand, we see domesticated animals and plants, though often weak and sickly, breeding freely under confinement; and when, on the other hand, we see individuals, though taken young from a state of nature perfectly tamed, long-lived and healthy (of which I could give numerous instances), yet having their reproductive system so seriously affected by unperceived causes as to fail to act, we need not be surprised at this system, when it does act under confinement, acting irregularly, and producing offspring somewhat unlike their parents.

pollen
pollen
02 - Variations Under Nature 02-04 - Wide-ranging, much diffused, and common Species vary most 30 With respect to the number of individuals or commonness of species, the comparison of course relates only to the members of the same group.

One of the higher plants may be said to be dominant if it be more numerous in individuals and more widely diffused than the other plants of the same country, which live under nearly the same conditions.

A plant of this kind is not the less dominant because some conferva inhabiting the water or some parasitic fungus is infinitely more numerous in individuals and more widely diffused.

But if the conferva or parasitic fungus exceeds its allies in the above respects, it will then be dominant within its own class.

conferva
conferva

fungus
fungus
05 - Laws of Variation 05-12 - Reversion to Long Lost Characters 50 With respect to the horse, I have collected cases in England of the spinal stripe in horses of the most distinct breeds, and of all colours: transverse bars on the legs are not rare in duns, mouse-duns, and in one instance in a chestnut a faint shoulder-stripe may sometimes be seen in duns, and I have seen a trace in a bay horse.

horse
horse

England
England


My son made a careful examination and sketch for me of a dun Belgian cart-horse with a double stripe on each shoulder and with leg-stripes; I have myself seen a dun Devonshire pony, and a small dun Welsh pony has been carefully described to me, both with three parallel stripes on each shoulder.

Belgian Cart Horse
Belgian Cart Horse

Welsh Pony
Welsh Pony
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.