F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

ties, but will have supplanted each other; so that, at each successive stage of modification and improvement, all the individuals of each variety will have descended from a single parent. But in the majority of cases, namely, with all organisms which habitually unite for each birth, or which often intercross, I believe that during the slow process of modification the individuals of the species will have been kept nearly uniform by intercrossing; so that many individuals will have gone on

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

members of the same groups; and this by the concurrent evidence of our best palæontologists seems frequently to be the case. Thus, on the theory of descent with modification, the main facts with respect to the mutual affinities of the extinct forms of life to each other and to living forms, seem to me explained in a satisfactory manner. And they are wholly inexplicable on any other view. On this same theory, it is evident that the fauna of any great period in the earth's history will be

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

the two countries will have received colonists from some third source or from each other, at various periods and in different proportions, the course of modification in the two areas will inevitably have been different. On this view of migration, with subsequent modification, we can see why oceanic islands should be inhabited by few species, but of these, that many should be peculiar. We can clearly see why those animals which cannot cross wide spaces of ocean, as frogs and terrestrial mammals

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

-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

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

course of descent, primordial organs of any kind—vertebræ in the one case and legs in the other—have actually been modified into skulls or jaws. Yet so strong is the appearance of a modification of this nature having occurred, that naturalists can hardly avoid employing language having this plain signification. On my view these terms may be used literally; and the wonderful fact of the jaws, for instance, of a crab retaining numerous characters, which they would probably have retained through

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

related to each other in habits, constitution, and structure. Hence all the intermediate forms between the earlier and later states, that is between the less and more improved states of a species, as well as the original parent-species itself, will generally tend to become extinct. So it probably will be with many whole collateral lines of descent, which will be conquered by [page] 12

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

CHAPTER VI. DIFFICULTIES ON THEORY. Difficulties on the theory of descent with modification — Transitions — Absence or rarity of transitional varieties — Transitions in habits of life — Diversified habits in the same species — Species with habits widely different from those of their allies — Organs of extreme perfection — Means of transition — Cases of difficulty — Natura non facit saltum — Organs of small importance — Organs not in all cases absolutely perfect — The law of Unity of Type and

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

modification of their descendants, causes the forms of life, after long intervals of time, to appear as if they had changed simultaneously throughout the world. The fact of the fossil remains of each formation being in some degree intermediate in character between the fossils in the formations above and below, is simply explained by their intermediate position in the chain of descent. The grand fact that all extinct organic beings belong to the same system with recent beings, falling either into the same

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

remove many difficulties, but it would not explain all the facts in regard to insular productions. In the following remarks I shall not confine myself to the mere question of dispersal; but shall consider some other facts, which bear on the truth of the two theories of independent creation and of descent with modification. The species of all kinds which inhabit oceanic islands are few in number compared with those on equal continental areas: Alph. de Candolle admits this for plants, and

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

are produced by descent with modification, from two or more species of the same genus. And the two or more parent-species are supposed to have descended from some one species of an earlier genus. In our diagram, this is indicated by the broken lines, beneath the capital letters, converging in sub-branches downwards towards a single point; this point representing a single species, the supposed single parent of our several new sub-genera and genera. It is worth while to reflect for a moment on

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

forms — On the succession of the same types within the same areas — Summary of preceding and present chapter. LET us now see whether the several facts and rules relating to the geological succession of organic beings, better accord with the common view of the immutability of species, or with that of their slow and gradual modification, through descent and natural selection. New species have appeared very slowly, one after another, both on the land and in the waters. Lyell has shown that it is hardly

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

of growth, but in order to excrete horny matter, as that the rudimentary nails on the fin of the manatee were formed for this purpose. On my view of descent with modification, the origin of rudimentary organs is simple. We have plenty of cases of rudimentary organs in our domestic productions,—as the stump of a tail in tailless breeds,—the vestige of an ear in earless breeds,—the reappearance of minute dangling horns in hornless breeds of cattle, more especially, according to Youatt, in young

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree. When it was first said that the sun stood still and the world turned round, the common sense of mankind declared the doctrine false; but the old saying of Vox populi, vox Dei, as

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

Africa than it is at the present time. Analogous facts could be given in relation to the distribution of marine animals. On the theory of descent with modification, the great law of the long enduring, but not immutable, succession of the same types within the same areas, is at once explained; for the inhabitants of each quarter of the world will obviously tend to leave in that quarter, during the next succeeding period of time, closely allied though in some degree modified descendants. If the

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

fertility. Turning to geographical distribution, the difficulties encountered on the theory of descent with modification are serious enough. All the individuals of the same species, and all the species of the same genus, or even higher group, must have descended from common parents; and therefore, in however distant and isolated parts of the world they are now found, they must in the [page] 49

F381    Book:     Darwin, C. R. 1861. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 3d ed. Seventh thousand.   Text   Image   PDF

the horse,—the same number of vertebræ forming the neck of the giraffe and of the elephant,—and innumerable other such facts, at once explain themselves on the theory of descent with slow and slight successive modifications. The similarity of pattern in the wing and leg of a bat, though used for such different purpose,—in the jaws and legs of a crab,—in the petals, stamens, and pistils of a flower, is likewise intelligible on the view of the gradual modification of parts or organs, which were

F3506    Periodical contribution:     Darwin, C. R. 1877. [Letter to T. Davidson, 1861]. In T. Davidson, What is a Brachiopod? Part III. The Geological Magazine or Monthly Journal of Geology n.s., 4, no. 6 (June): 262-273, p. 269.   Text   Image

suspect that on the whole it would be favourable to the notion of descent with modification. I can hardly doubt that many curious points would occur to any one thoroughly instructed in the subject, who could consider a group of beings under the point of view of descent with modification. All those forms which have come down from an ancient period very slightly modified ought, I think, to be omitted; and those forms alone considered which have undergone considerable change at each successive

F4047    Book contribution:     Darwin, C. R. 1921. [Letters to Fritz Müller]. In Alfred Möller ed., Fritz Müller. Werke, Briefe und Leben. 3 vols. in 5. Jena: Gustav Fischer, vol. 2 Briefe.   Text

The Complete Work of Charles Darwin Online [page] 73 An Fritz Müller von Darwin). Down-Bromley. Kent S. E. Sept. 20 (1865) (received Oct. 26) My dear Sir! I am very much obliged for your interesting letter written in such wonderfully good English about climbing plants. The case of Haplolophium) is new to me and I am glad to have seen the tendril of Strychnos. I do not suppose I shall attend any more to climbing plants, but I should like to hear if you ever meet with 2 species of the same genus

F385    Book:     Darwin, C. R. 1866. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 4th ed. 8th thousand.   Text   Image   PDF

, if we admit that there has been during the long course of ages much migration from one part of the world to another, owing to former climatal and geographical changes and to the many occasional and unknown means of dispersal, then we can understand, on the theory of descent with modification, most of the great leading facts in Distribution. We can see why there should be so striking a parallelism in the distribution of organic beings throughout space, and in their geological succession throughout

F385    Book:     Darwin, C. R. 1866. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 4th ed. 8th thousand.   Text   Image   PDF

within each great class have been created with plain, but deceptive, marks of descent from a single parent. It may be asked how far I extend the doctrine of the modification of species. The question is difficult to answer, because the more distinct the forms are which we may consider, by so much the arguments fall away in force. But some arguments of the greatest weight extend very far. All the members of whole classes can be connected together by chains of affinities, and all can be classified

F385    Book:     Darwin, C. R. 1866. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 4th ed. 8th thousand.   Text   Image   PDF

would be strange facts if species have been independently created, and varieties have been produced by secondary laws. If we admit that the geological record is imperfect in an extreme degree, then the facts, which the record does give, strongly support the theory of descent with modification. New species have come on the stage slowly and at successive intervals; and the amount of change, after equal intervals of time, is widely different in different groups. The extinction of species and of

F385    Book:     Darwin, C. R. 1866. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 4th ed. 8th thousand.   Text   Image   PDF

the case. Thus, on the theory of descent with modification, the main facts with respect to the mutual affinities of the extinct forms of life to each other and to living forms, seem to me explained in a satisfactory manner. And they are wholly inexplicable on any other view. On this same theory, it is evident that the fauna of any great period in the earth's history will be intermediate in general character between that which preceded and that which succeeded it. Thus the species which lived at

F385    Book:     Darwin, C. R. 1866. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 4th ed. 8th thousand.   Text   Image   PDF

CHAPTER XIII. MUTUAL AFFINITIES OF ORGANIC BEINGS: MORPHOLOGY: EMBRYOLOGY: RUDIMENTARY ORGANS. CLASSIFICATION, groups subordinate to groups Natural system Rules and difficulties in classification, explained on the theory of descent with modification Classification of varieties Descent always used in classification Analogical or adaptive characters Affinities, general, complex, and radiating Extinction separates and defines groups MORPHOLOGY, between members of the same class, between parts of

F385    Book:     Darwin, C. R. 1866. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 4th ed. 8th thousand.   Text   Image   PDF

extinct. So it probably will be with many whole collateral lines of descent, which will be conquered by later and improved lines of descent. If, however, the modified offspring of a species get into some distinct country, or become quickly adapted to some quite new station, in which child and parent do not come into competition, both may continue to exist. [page] 13

F385    Book:     Darwin, C. R. 1866. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 4th ed. 8th thousand.   Text   Image   PDF

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