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Export to Excel select * from OriginOfSpecies where subject = '02 - Variations Under Nature' order by subject, title, ordinal limit 20, 4 (Page 6: Row)
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02 - Variations Under Nature 02-06 - Many of the Species included within the Larger Genera resemble Varieties in being very closely, but unequally, related to each other, and in having restricted ranges 20 And what are varieties but groups of forms, unequally related to each other, and clustered round certain forms- that is, round their parent-species. Undoubtedly there is one most important point of difference between varieties and species; namely, that the amount of difference between varieties, when compared with each other or with their parent-species, is much less than that between the species of the same genus.

But when we come to discuss the principle, as I call it, of Divergence of Character, we shall see how this may be explained, and how the lesser differences between varieties tend to increase into the greater differences between species.

There is one other point which is worth notice.

Varieties generally have much restricted ranges: this statement is indeed scarcely more than a truism, for, if a variety were found to have a wider range than that of its supposed parent-species, their denominations would be reversed.

But there is reason to believe that the species which are very closely allied to other species, and in so far resemble varieties, often have much restricted ranges.

For instance, Mr. H. C. Watson has marked for me in the well-sifted London Catalogue of Plants (4th edition) 63 plants which are therein ranked as species, but which he considers as so closely allied to other species as to be of doubtful value: these 63 reputed species range on an average over 6.9 of the provinces into which Mr. Watson has divided Great Britain. Now, in this same Catalogue, 53 acknowledged varieties are recorded, and these range over 7.7 provinces; whereas, the species to which these varieties belong range over 14.3 provinces.

Hewett Cottrell Watson
Hewett Cottrell Watson


So that the acknowledged varieties have nearly the same
restricted average range, as have the closely allied forms, marked for me by Mr. Watson as doubtful species, but which are almost universally ranked by British botanists as good and true species.
02 - Variations Under Nature 02-07 - Summary 10 Finally, varieties cannot be distinguished from species,- except, first, by the discovery of intermediate linking forms; and, secondly, by a certain indefinite amount of difference between them; for two forms, if differing very little, are generally ranked as varieties, notwithstanding that they cannot be closely connected; but the amount of difference considered necessary to give to any two forms the rank of species cannot be defined.

In genera having more than the average number of species in any country, the species of these genera have more than the average number of varieties.

In large genera the species are apt to be closely, but unequally, allied together, forming little clusters round other species. Species very closely allied to other species apparently have restricted ranges.
02 - Variations Under Nature 02-07 - Summary 20 In all these respects the species of large genera present a strong analogy with varieties. And we can clearly understand these analogies, if species once existed as varieties, and thus originated; whereas, these analogies are utterly inexplicable if species are independent creations.

We have, also, seen that it is the most flourishing or dominant species of the larger genera within each class which on an average yield the greatest number of varieties; and varieties, as we shall hereafter see, tend to become converted into new and distinct species.

Thus the larger genera tend to become larger; and throughout nature the forms of life which are now dominant tend to become still more dominant by leaving many modified and dominant descendants.

But by steps hereafter to be explained, the larger genera also tend to break u into smaller genera. And thus, the forms of life throughout the universe become divided into groups subordinate to groups.