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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 19 of 119 (4/p)
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02 - Variations Under Nature 02-04 - Wide-ranging, much diffused, and common Species vary most 20 Alphonse de Candolle and others have shown that plants which have very wide ranges generally present varieties; and this might have been expected, as they are exposed to diverse physical conditions, and as they come into competition (which, as we shall hereafter see, is an equally or more important circumstance) with different sets of organic beings.

Alphonse de Candolle
Alphonse de Candolle


But my tables further show that, in any limited country, the species which are the most common, that is abound most in individuals, and the species which are most widely diffused within their own country (and this is a different consideration from wide range, and to a certain extent from commonness), oftenest give rise to varieties sufficiently well marked to have been recorded in botanical works.

Hence it is the most flourishing, or, as they may be called, the dominant species,- those which range widely, are the most diffused in their own country, and are the most numerous in individuals,- which oftenest produce well-marked varieties, or, as I consider them, incipient species.

And this, perhaps, might have been anticipated; for as varieties, in order to become in any degree permanent, necessarily have to struggle with the other inhabitants of the country, the species which are already dominant will be the most likely to yield offspring, which, though in some slight degree modified, still inherit those advantages that enabled their parents to become dominant over their compatriots.

In these remarks on predominance, it should be understood that reference is made only to the forms which come into competition with each other, and more especially to the members of the same genus or class having nearly similar habits of life.
02 - Variations Under Nature 02-03 - Doubtful Species 90 It need not be supposed that all varieties or incipient species attain the rank of species. They may become extinct, or they may endure as varieties for very long periods, as has been shown to be the case by Mr. Wollaston with the varieties of certain fossil land-shell in Madeira, and with plants by Gaston de Saporta. If a variety were to flourish so as to exceed in numbers the parent species, it would then rank as the species, and the species as the variety; or it might come to supplant and exterminate the parent species; or both might co-exist, and both rank as independent species.

Land Shell
Land Shell

Madeira
Madeira


But we shall hereafter return to this subject.
02 - Variations Under Nature 02-05 - Species of the Larger Genera in each Country vary more frequently than the Species of the Smaller Genera 20 On the other hand, if we look at each species as a special act of creation, there is no apparent reason why more varieties should occur in a group having many species, than in one having few.

To test the truth of this anticipation I have arranged the plants of twelve countries, and the coleopterous insects of two districts, into two nearly equal masses, the species of the larger genera on one side, and those of the smaller genera on the other side, and it has invariably proved to be the case that a larger proportion of the species on the side of the larger genera presented varieties, than on the side of the smaller genera.

Moreover, the species of the large genera which present any varieties, invariably present a larger average number of varieties than do the species of the small genera.

Both these results follow when another division is made, and when all the least genera, with from only one to four species, are altogether excluded from the tables.

These facts are of plain signification on the view that species are only strongly-marked and permanent varieties; for wherever many species of the same genus have been formed, or where, if we may use the expression, the manufactory of species has been active, we ought generally to find the manufactory still in action, more especially as we have every reason to believe the process of manufacturing new species to be a slow one.

And this certainly holds true, if varieties be looked at as incipient species; for my tables clearly show as a general rule that, wherever many species of a genus have been formed, the species of that genus present a number of varieties, that is of incipient species, beyond the average.

It is not that all large genera are now varying much, and are thus increasing in the number of their species, or that no small genera are now varying and increasing; for if this had been so, it would have been fatal to my theory; inasmuch as geology plainly tells us that small genera have in the lapse of time often increased greatly in size; and that large genera have often come to their maxima, declined, and disappeared.

All that we want to show is, that when many species of a genus have been formed, on an average many are still forming; and this certainly holds good.
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