RTB
M Database Inspector (cheetah)
Not logged in. Login


133 rows, page 20 of 34 (4/p)
1 10 14 15 16 17 18 19 20 21 22 23 24 25 26 30 34

Export to Excel select * from OriginOfSpecies where ordinal = '10' order by subject desc limit 76, 4 (Page 20: Row)
subject Desending Order (top row is last)
title
ordinal
description
05 - Laws of Variation 05-06 - False Correlation 10 We may often falsely attribute to correlated variation structures which are common to whole groups of species, and which in truth are simply due to inheritance; for an ancient progenitor may have acquired through natural selection some one modification in structure, and, after thousands of generations, some other and independent modification; and these two modifications, having been transmitted to a whole group of descendants with diverse habits, would naturally be thought to be in some necessary manner correlated.
05 - Laws of Variation 05-10 - Secondary Sexual Characters Variable 10 Secondary Sexual Characters Variable.- I think it will be admitted by naturalists, without my entering on details, that secondary sexual characters are highly variable.

It will also be admitted that species of the same group differ from each other more widely in their secondary sexual characters, than in other parts of their organisation: compare, for instance, the amount of difference between the males of gallinaceous birds, in which secondary sexual characters are strongly displayed, with the amount of difference between the females.

gallinaceous
gallinaceous


The cause of the original variability of these characters is not manifest; but we can see why they should not have been rendered as constant and uniform as others, for they are accumulated by sexual selection, which is less rigid in its action than ordinary selection, as it does not entail death, but only gives fewer off-spring to the less favoured males.

Whatever the cause may be of the variability of secondary sexual characters, as they are highly variable, sexual selection will have had a wide scope for action, and may thus have succeeded in giving to the species of the same group a greater amount of difference in these than in other respects.
05 - Laws of Variation 05-07 - Multiple, Rudimentary, and Lowly-organised Structures are Variable 10 It seems to be a rule, as remarked by the younger Geoffroy, both with varieties and species, that when any part or organ is repeated many times in the same individual (as the vertebrae in snakes, and the stamens in polyandrous flowers) the number is variable; whereas the same part or organ, when it occurs in lesser numbers, is constant.

snake
snake


The same author as well as some botanists have further remarked that multiple parts are extremely liable to vary in structure. As "vegetable repetition," to use Prof. Owen's expression, is a sign of low organisation, the foregoing statements accord with the common opinion of naturalists, that beings which stand low in the scale of nature are more variable than those which are higher.
Richard Owen
Richard Owen
05 - Laws of Variation 05-05 - Compensation and Economy of Growth 10 The elder Geoffroy and Goethe propounded, at about the same time, their law of compensation or balancement of growth; or, as Goethe expressed it, "In order to spend on one side, nature is forced to economise on the other side."

I think this holds true to a certain extent with our domestic productions: if nourishment flows to one part or organ in excess, it rarely flows, at least in excess, to another part; thus it is difficult to get a cow to give much milk and to fatten readily.

cows
cows

milk
milk


The same varieties of the cabbage do not yield abundant and nutritious foliage and a copious supply of oil-bearing seeds.

cabbage
cabbage


When the seeds in our fruits become atrophied, the fruit itself gains largely in size and quality. In our poultry, a large tuft of feathers on the head is generally accompanied by a diminished comb, and a large beard by diminished wattles.

fruit
fruit

poultry
poultry