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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 7 of 119 (4/p)
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Export to Excel select * from OriginOfSpecies order by description desc limit 24, 4 (Page 7: Row)
subject
title
ordinal
description Desending Order (top row is last)
02 - Variations Under Nature 02-03 - Doubtful Species 60 When a young naturalist commences the study of a group of organisms quite unknown to him, he is at first much perplexed in determining what differences to consider as specific, and what as varietal; for he knows nothing of the amount and kind of variation to which the group is subject; and this shows, at least, how very generally there is some variation.

But if he confine his attention to one class within one country, he will soon make up his mind how to rank most of the doubtful forms.

His general tendency will be to make many species, for he will become impressed, just like the pigeon or poultry fancier before alluded to, with the amount of difference in the forms which he is continually studying; and he has little general knowledge of analogical variation in other groups and in other countries, by which to correct his first impressions.

Pigeon
Pigeon

poultry
poultry


As he extends the range of his observations, he will meet with more cases of difficulty; for he will encounter a greater number of closely-allied forms.

But if his observations be widely extended, he will in the end generally be able to make up his own mind: but he will succeed in this at the expense of admitting much variation,- and the truth of this admission will often be disputed by other naturalists.

When he comes to study allied forms brought from countries not now continuous, in which case he cannot hope to find intermediate links, he will be compelled to trust almost entirely to analogy, and his difficulties will rise to a climax.
03 - Struggle for Existence 03-08 - Protection from the Number of Individuals 10 When a species, owing to highly favourable circumstances, increases inordinately in numbers in a small tract, epidemics- at least, this seems generally to occur with our game animals- often ensue; and here we have a limiting check independent of the struggle for life.

But even some of these so-called epidemics appear to be due to parasitic worms, which have from some cause, possibly in part through facility of diffusion amongst the crowded animals, been disproportionally favoured: and here comes in a sort of struggle between the parasite and its prey.

worm
worm

parasite
parasite
prey
prey
04 - Natural Selection 04-13 - Convergence of Character 60 What then checks an indefinite increase in the number of species?

The amount of life (I do not mean the number of specific forms) supported on an area must have a limit, depending so largely as it does on physical conditions; therefore, if an area be inhabited by very many species, each or nearly each species will be represented by few individuals; and such species will be liable to extermination from accidental fluctuations in the nature of the seasons or in the number of their enemies.
05 - Laws of Variation 05-12 - Reversion to Long Lost Characters 90 What now are we to say to these several facts?

We see several distinct species of the horse-genus becoming, by simple variation, striped on the legs like a zebra, or striped on the shoulders like an ass. In the horse we see this tendency strong whenever a dun tint appears- a tint which approaches to that of the general colouring of the other species of the genus.

horse
horse

ass
ass

Dun Horse
Dun Horse


The appearance of the stripes is not accompanied by any change of form or by any other new character.

We see this tendency to become striped most strongly displayed in hybrids from between several of the most distinct species.

Now observe the case of the several breeds of pigeons: they are descended from a pigeon (including two or three sub-species or geographical races) of bluish colour, with certain bars and other marks; and when any breed assumes by simple variation a bluish tint, these bars and other marks invariably reappear; but without any other change of form or character.

pigeon
pigeon


When the oldest and truest breeds of various colours are crossed, we see a strong tendency for the blue tint and bars and marks to reappear in the mongrels.

I have stated that the most probable hypothesis to account for the reappearance of very ancient characters, is- that there is a tendency in the young of each successive generation to produce the long-lost character, and that this tendency, from unknown causes, sometimes prevails.

And we have just seen that in several species of the horse-genus the stripes are either plainer or appear more commonly in the young than in the old.

Call the breeds of pigeons, some of which have bred true for centuries, species; and how exactly parallel is the case with that of the species of the horse-genus!

horse
horse

pigeon
pigeon


For myself, I venture confidently to look back thousands on thousands of generations, and I see an animal striped like a zebra, but perhaps otherwise very differently constructed, the common parent of our domestic horse (whether or not it be descended from one or more wild stocks), of the ass, the hemionus, quagga, and zebra.

horse
horse

ass
ass

hemionus
hemionus

quagga
quagga

zebra
zebra