M Database Inspector (cheetah)
Not logged in. Login


133 rows, page 4 of 34 (4/p)
1 2 3 4 5 6 7 8 9 10 20 30 34

Export to Excel select * from OriginOfSpecies where ordinal = '10' order by title desc limit 12, 4 (Page 4: Row)
subject
title Desending Order (top row is last)
ordinal
description
13 - Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Or 13-06 - Analogical or adaptive characters 10 As members of distinct classes have often been adapted by successive slight modifications to live under nearly similar circumstances, to inhabit for instance the three elements of land, air, and water, we can perhaps understand how it is that a numerical parallelism has sometimes been observed between the sub-groups in distinct classes.

A naturalist, struck by a parallelism of this nature in any one class, by arbitrarily raising or sinking the value of the groups in other classes (and all our experience shows that this valuation has hitherto been arbitrary), could easily extend the parallelism over a wide range; and thus the septenary, quinary, quaternary, and ternary classifications have probably arisen.

As the modified descendants of dominant species, belonging to the larger genera, tend to inherit the advantages, which made the groups to which they belong large and their parents dominant, they are almost sure to spread widely, and to seize on more and more places in the economy of nature.

The larger and more dominant groups thus tend to go on increasing in size; and they consequently supplant many smaller and feebler groups.

Thus we can account for the fact that all organisms, recent and extinct, are included under a few great orders, under still fewer classes, and all in one great natural system.

As showing how few the higher groups are in number, and how widely spread they are throughout the world, the fact is striking, that the discovery of Australia has not added a single insect belonging to a new order; and that in the vegetable kingdom, as I learn from Dr. Hooker, it has added only two or three orders of small size.

Australia
Australia
13 - Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Or 13-05 - Descent always used in classification 10 With species in a state of nature, every naturalist has in fact brought descent into his classification; for he includes in his lowest grade, or that of a species, the two sexes; and how enormously these sometimes differ in the most important characters, is known to every naturalist: scarcely a single fact can be predicated in common of the males and hermaphrodites of certain cirripedes, when adult, and yet no one dreams of separating them.

cirripede
cirripede


The naturalist includes as one species the several larval stages of the same individual, however much they may differ from each other and from the adult; as he likewise includes the so-called alternate generations of Steenstrup, which can only in a technical sense be considered as the same individual.

Japetus Steenstrup
Japetus Steenstrup


He includes monsters; he includes varieties, not solely because they closely resemble the parent-form, but because they are descended from it.

He who believes that the cowslip is descended from the primrose, or conversely, ranks them together as a single species, and gives a single definition.

cowslip
cowslip

primrose
primrose


As soon as three Orchidean forms (Monochanthus, Myanthus, and Catasetum), which had previously been ranked as three distinct genera, were known to be sometimes produced on the same spike, they were immediately included as a single species.

orchid
orchid
13 - Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Or 13-04 - Classification of varieties 10 In confirmation of this view, let us glance at the classification of varieties, which are believed or known to have descended from one species.

These are grouped under species, with sub-varieties under varieties; and with our domestic productions, several other grades of difference are requisite, as we have seen with pigeons.

The origin of the existence of groups subordinate to groups, is the same with varieties as with species, namely, closeness of descent with various degrees of modification.

Nearly the same rules are followed in classifying varieties, as with species.

Authors have insisted on the necessity of classing varieties on a natural instead of an artificial system; we are cautioned, for instance, not to class two varieties of the pine-apple together, merely because their fruit, though the most important part, happens to be nearly identical; no one puts the swedish and common turnips together, though the esculent and thickened stems are so similar.

pineapple
pineapple

turnip
turnip


Whatever part is found to be most constant, is used in classing varieties: thus the great agriculturist Marshall says the horns are very useful for this purpose with cattle, because they are less variable than the shape or colour of the body, &c.; whereas with sheep the horns are much less serviceable, because less constant.

cattle
cattle

sheep
sheep


In classing varieties, I apprehend if we had a real pedigree, a genealogical classification would be universally preferred; and it has been attempted by some authors.

For we might feel sure, whether there had been more or less modification, the principle of inheritance would keep the forms together which were allied in the greatest number of points.

In tumbler pigeons, though some sub-varieties differ from the others in the important character of having a longer beak, yet all are kept together from having the common habit of tumbling; but the short-faced breed has nearly or quite lost this habit; nevertheless, without any reasoning or thinking on the subject, these tumblers are kept in the same group, because allied in blood and alike in some other respects.

Tumbler Pigeon
Tumbler Pigeon

Short Faced Tumbler Pigeon
Short Faced Tumbler Pigeon


If it could be proved that the Hottentot had descended from the Negro, I think he would be classed under the Negro group, however much he might differ in colour and other important characters from negroes.
13 - Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Or 13-03 - Rules and difficulties in classification, explained on the theory of descent with modification 10 Let us now consider the rules followed in classification, and the difficulties which are encountered on the view that classification either gives some unknown plan of creation, or is simply a scheme for enunciating general propositions and of placing together the forms most like each other.

It might have been thought (and was in ancient times thought) that those parts of the structure which determined the habits of life, and the general place of each being in the economy of nature, would be of very high importance in classification.

Nothing can be more false.

No one regards the external similarity of a mouse to a shrew, of a dugong to a whale, of a whale to a fish, as of any importance.

mouse
mouse

shrew
shrew

dugong
dugong

whale
whale

fish
fish