F1577    Periodical contribution:     Barlow, Nora ed. 1963. Darwin's ornithological notes. Bulletin of the British Museum (Natural History). Historical Series 2 (7): 201-278. With introduction, notes and appendix by the editor.   Text   Image   PDF

should have been created. We can see this in the light of later knowledge as a very transparent curtain to evolutionary views far advanced. But I believe that already by 1834-35 there were questions being asked in the O.N.s that could only have been based on a groping belief in some form of descent with modification. I have looked up the equivalent passage in the early draft in Vol. 31 i, C.U.L. Handlist p. 277, reverse, Wilmot paper, 1828. Darwin writes from Valparaiso, dated Aug.-Sep. 1834: It

F1574a    Pamphlet:     de Beer, Gavin ed. 1960. Darwin's notebooks on transmutation of species. Part I. First notebook [B] (July 1837-February 1838). Bulletin of the British Museum (Natural History). Historical Series 2 (2) (January): 23-73.   Text   Image   PDF

arises how this is to be reconciled with Darwin's statement2 written in 1876 referring to the Essay of 1844: But at that time I overlooked one problem of great importance. This problem is the tendency in organic beings descended from the same stock to diverge in character as they become modified . In trying to explain this discrepancy, Sir Francis Darwin3 was mistaken in thinking that descent with modification necessarily implies divergence; evolution might take place along single lines without

F1574a    Pamphlet:     de Beer, Gavin ed. 1960. Darwin's notebooks on transmutation of species. Part I. First notebook [B] (July 1837-February 1838). Bulletin of the British Museum (Natural History). Historical Series 2 (2) (January): 23-73.   Text   Image   PDF

evolution could not occur. Unknown to Darwin, two other men2 had, before him, grasped the solution of the problem and stated that natural selection could cause modification of species; but they were very far from being able to appreciate the significance of what they had done, provide evidence to support it, or work out its consequences. The second consideration to bear in mind is that while Darwin was always on the look-out for facts, what he most hoped for in the works of his predecessors and

F1555    Book:     Darwin, Francis ed. 1909. The foundations of The origin of species, a sketch written in 1842. Cambridge: University Press.   Text   Image   PDF

original creations. But if the descendants of A have peopled the earth by beating out other forms, they must have diverged in occupying the innumerable diverse modes of life from which they expelled their predecessors. What I wrote2 on this subject in 1887 is I think true: Descent with modification implies divergence, and we become so habituated to a belief in descent, and therefore in divergence, that we do not notice the absence of proof that divergence is in itself an advantage. I have called

F1583    Book:     Stauffer, R. C. ed. 1975. Charles Darwin's Natural Selection; being the second part of his big species book written from 1856 to 1858. Cambridge: Cambridge University Press.   Text   Image   PDF

as the one just given, or the more simple one but requiring much greater geographical changes given by Dr. Hooker, to account on the theory of descent for the same, with subsequent modification, for the representative species in these two distant areas. On the other hand those who believe in simple creation can, in my opinion, give no explanation in the least degree satisfactory of the shades of affinity degree of identity in the cases which we have been discussing: they in fact simply state so

F1583    Book:     Stauffer, R. C. ed. 1975. Charles Darwin's Natural Selection; being the second part of his big species book written from 1856 to 1858. Cambridge: Cambridge University Press.   Text   Image   PDF

, to descent from common parents; their slight differences/68/to subsequent modification through natural selection. So when we hear that the thrush (Turdus Falklandicus) of South America, like our European species, lines her nest in the same peculiar way with mud, though from being surrounded by wholly different plants animals, she must be placed under somewhat different conditions; or when we hear that in N. America, the males of two Kitty wrens,1 like the male of our species, have the strange

PC-Virginia-Francis-F373    Printed:    1859   On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. [Francis Darwin's copy]  London   Text   Image   PDF

But it may be asked, what ought we to do, if it could be proved that one species of kangaroo had been produced, by a long course of modification, from a bear? Ought we to rank this one species with bears, and what should we do with the other species? The supposition is of course preposterous; and I might answer by the argumentum ad hominem, and ask what should be done if a perfect kangaroo were seen to come out of the womb of a bear? According to all analogy, it would be ranked with bears; but

F373    Book:     Darwin, C. R. 1859. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 1st ed., 1st issue.   Text   Image   PDF

, together with their modification through natural selection, with its contingencies of extinction and divergence of character. In considering this view of classification, it should be borne in mind that the element of descent has been universally used in ranking together the sexes, ages, and acknowledged varieties of the same species, however different they may be in structure. If we extend the use of this element of descent,—the only certainly known cause of similarity in organic beings,—we shall

PC-Virginia-Francis-F373    Printed:    1859   On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. [Francis Darwin's copy]  London   Text   Image   PDF

, together with their modification through natural selection, with its contingencies of extinction and divergence of character. In considering this view of classification, it should be borne in mind that the element of descent has been universally used in ranking together the sexes, ages, and acknowledged varieties of the same species, however different they may be in structure. If we extend the use of this element of descent,—the only certainly known cause of similarity in organic beings,—we shall

PC-Virginia-Francis-F373    Printed:    1859   On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. [Francis Darwin's copy]  London   Text   Image   PDF

All the foregoing rules and aids and difficulties in classification are explained, if I do not greatly deceive myself, on the view that the natural system is founded on descent with modification; that the characters which naturalists consider as showing true affinity between any two or more species, are those which have been inherited from a common parent, and, in so far, all true classification is genealogical; that community of descent is the hidden bond which naturalists have been

F373    Book:     Darwin, C. R. 1859. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 1st ed., 1st issue.   Text   Image   PDF

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 simultaneously changing, and the whole amount of modification will not have been due, at each stage, to descent from a single parent. To illustrate what I mean: our English

F373    Book:     Darwin, C. R. 1859. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 1st ed., 1st issue.   Text   Image   PDF

during a long 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 [page] 439 CHAP. XIII. EMBRYOLOGY

F373    Book:     Darwin, C. R. 1859. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 1st ed., 1st issue.   Text   Image   PDF

seem to me simply to follow on the theory of descent with modification through natural selection. We can thus understand how it is that new species come in slowly and successively; how species of different classes do not necessarily change together, or at the same rate, or in the same degree; yet in the long run that all undergo modification to some extent. The extinction of old forms is the almost inevitable consequence of the production of new forms. We can understand why when a species has

F373    Book:     Darwin, C. R. 1859. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 1st ed., 1st issue.   Text   Image   PDF

state; and this in some instances necessarily implies an enormous amount of modification in the descendants. Throughout whole classes various structures are formed on the same pattern, and at an embryonic age the species closely resemble each other. Therefore I cannot doubt that the theory of descent with modification Y 2 [page] 484 CONCLUSION. CHAP. XIV

PC-Virginia-Francis-F373    Printed:    1859   On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. [Francis Darwin's copy]  London   Text   Image   PDF

, 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 time; for in both cases the beings have been connected by the bond of ordinary generation, and the means of [page] 477 CHAP. XIV. RECAPITULATION

F373    Book:     Darwin, C. R. 1859. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 1st ed., 1st issue.   Text   Image   PDF

of bones being the same in the hand of a man, wing of a bat, fin of the porpoise, and leg of 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

PC-Virginia-Francis-F373    Printed:    1859   On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. [Francis Darwin's copy]  London   Text   Image   PDF

seem to me simply to follow on the theory of descent with modification through natural selection. We can thus understand how it is that new species come in slowly and successively; how species of different classes do not necessarily change together, or at the same rate, or in the same degree; yet in the long run that all undergo modification to some extent. The extinction of old forms is the almost inevitable consequence of the production of new forms. We can understand why when a species has

PC-Virginia-Francis-F373    Printed:    1859   On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. [Francis Darwin's copy]  London   Text   Image   PDF

state; and this in some instances necessarily implies an enormous amount of modification in the descendants. Throughout whole classes various structures are formed on the same pattern, and at an embryonic age the species closely resemble each other. Therefore I cannot doubt that the theory of descent with modification Y 2 [page] 484 CONCLUSION. CHAP. XIV

PC-Virginia-Francis-F373    Printed:    1859   On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. [Francis Darwin's copy]  London   Text   Image   PDF

of bones being the same in the hand of a man, wing of a bat, fin of the porpoise, and leg of 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

PC-Virginia-Francis-F373    Printed:    1859   On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. [Francis Darwin's copy]  London   Text   Image   PDF

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

F373    Book:     Darwin, C. R. 1859. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 1st ed., 1st issue.   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

F373    Book:     Darwin, C. R. 1859. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 1st ed., 1st issue.   Text   Image   PDF

complex laws in their degrees and kinds of resemblance to their parents,—in being absorbed into each other by successive crosses, and in other such points,—as do the crossed offspring of acknowledged varieties. On the other hand, these 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 such facts as the record gives, support the theory of descent with

PC-Virginia-Francis-F373    Printed:    1859   On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. [Francis Darwin's copy]  London   Text   Image   PDF

Batrachians, the older Fish, the older Cephalopods, and the eocene Mammals, with the more recent members of the same classes, we must admit that there is some truth in the remark. Let us see how far these several facts and inferences accord with the theory of descent with modification. As the subject is somewhat complex, I must request the reader to turn to the diagram in the fourth chapter. We may suppose that the numbered letters represent genera, and the dotted lines diverging from them the

PC-Virginia-Francis-F373    Printed:    1859   On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. [Francis Darwin's copy]  London   Text   Image   PDF

and other distant points of the southern hemisphere, is, on my theory of descent with modification, a far more remarkable case of difficulty. For some of these species are so distinct, that we cannot suppose that there has been time since the commencement of the Glacial period for their migration, and for their subsequent modification to the necessary degree. The facts seem to me to indicate that peculiar and very distinct species have migrated in radiating lines from some common centre; and I am

F373    Book:     Darwin, C. R. 1859. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 1st ed., 1st issue.   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