F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   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 of the Conditions of

F376    Book:     Darwin, C. R. 1860. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 2d ed., second issue.   Text   Image   PDF

), extinct, and have left no descendants. Hence the six new species descended from (I), and the eight descended from (A), will have to be ranked as very distinct genera, or even as distinct sub-families. Thus it is, as I believe, that two or more genera are produced by descent with modification, from two or more species of the same genus. And the two or G 2 [page] 12

F376    Book:     Darwin, C. R. 1860. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 2d ed., second 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

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   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

F376    Book:     Darwin, C. R. 1860. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 2d ed., second issue.   Text   Image   PDF

inferences briefly recapitulated. That many and serious objections may be advanced against the theory of descent with modification through natural selection, I do not deny. I have endeavoured to give to them their full force. Nothing at first can appear more difficult to believe than that the more complex organs and instincts should have been perfected, not by means superior to, though analogous with, human reason, but by the accumulation of innumerable slight variations, each good for the

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

intervals between existing orders. Organs in a rudimentary condition plainly show that an early progenitor had the organ in a fully developed 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 embraces all the members of the same

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

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

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

cousins to the same millionth degree; yet they differ widely and in different degrees from each other. The forms descended from A, now broken up into two or three families, constitute a distinct order from those descended from I, also broken up into two families. Nor can the existing species, descended from A, be ranked in the same genus with the parent A; or those from I, with the parent I. But the existing genus F14 may be supposed to have been but slightly modified; and it will then rank with the

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

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 unconsciously seeking, and not some unknown plan of creation, or the enunciation of general propositions, and the mere putting together and separating objects more or less alike. But I must

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

: they are far from meaning that during a long course of descent, primordial organs of any kind vertebr 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

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

between existing groups; and we can understand this fact, for the extinct species lived at very ancient epochs when the branching lines of descent had diverged less. I see no reason to limit the process of modification, as now explained, to the formation of genera alone. If, in our diagram, we suppose the amount of change represented by each successive group of diverging dotted lines to be very great, the forms marked a14 to p14, those marked b14 and f14, and those marked o14 to m14, will form three

F376    Book:     Darwin, C. R. 1860. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 2d ed., second issue.   Text   Image   PDF

started into life all at once, the fact would be fatal to the theory of descent with slow modification through natural selection. For the development of a group of forms, all of which have descended from some one progenitor, must have been an extremely slow process; and the progenitors must have lived long ages before their modified descendants. But we continually over-rate the perfection of the geological record, and falsely infer, because certain genera or families have not been found

F376    Book:     Darwin, C. R. 1860. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 2d ed., second issue.   Text   Image   PDF

descent with modification, we may conclude that the existence of organs in a rudimentary, imperfect, and useless condition, or quite aborted, far from presenting a strange difficulty, as they assuredly do on the ordinary doctrine of creation, might even have been anticipated, and can be accounted for by the laws of inheritance. Summary.—In this chapter I have attempted to show, that the subordination of group to group in all organisms throughout all time; that the nature of the relationship, by which

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

succession of the same types within the same areas Summary of preceding and present chapters. 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 possible to

F376    Book:     Darwin, C. R. 1860. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 2d ed., second issue.   Text   Image   PDF

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 inhabitants of one continent formerly differed greatly from

F376    Book:     Darwin, C. R. 1860. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 2d ed., second issue.   Text   Image   PDF

, imperfect nails sometimes appear on the stumps: I could as soon believe that these vestiges of nails have appeared, not from unknown laws 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

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

analogous manner Reversions to long lost characters Summary, 120 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

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

should not inhabit oceanic islands; and why, on the other hand, new and peculiar species of bats, which can traverse the ocean, should so often be found on islands far distant from any continent. Such facts as the presence of peculiar species of bats, and the absence of all other mammals, on oceanic islands, are utterly inexplicable on the theory of independent acts of creation. The existence of closely allied or representative species in any two areas, implies, on the theory of descent with

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

nearly a hemisphere of equatorial ocean. These cases of relationship, without identity, of the inhabitants of seas now disjoined, and likewise of the past and present inhabitants of the temperate lands of North America and Europe, are inexplicable on the theory of creation. We cannot say that they have been created alike, in correspondence with the nearly similar physical conditions of the areas; for if we compare, for instance, certain parts of South America with the southern continents of the

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

started into life all at once, the fact would be fatal to the theory of descent with slow modification through natural selection. For the development of a group of forms, all of which have descended from some one progenitor, must have been an extremely slow process; and the progenitors must have lived long ages before their modified descendants. But we continually over-rate the perfection of the geological record, and falsely infer, because certain genera or families have not been found within a

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

genus, but that the genus gives the characters, seem to imply that something more is included in our classification, than mere resemblance. I believe that something more is included; and that propinquity of descent, the only known cause of the similarity of organic beings, is the bond, hidden as it is by various degrees of modification, which is partially revealed to us by our classifications. Let us now consider the rules followed in classification, and the difficulties which are encountered

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

organisation, which has long existed, to be inherited we can understand, on the genealogical view of classification, bow it is that systematists have found rudimentary parts as useful as, or even sometimes more useful than, parts of high physiological importance. Rudimentary organs may be compared with the letters in a word, still retained in the spelling, but become useless in the pronunciation, but which serve as a clue in seeking for its derivation. On the view of descent with modification, we may

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

less completely lost traces of their parentage, in this case, their places in a natural classification will have been more or less completely lost, as sometimes seems to have occurred with existing organisms: All the descendants of the genus F, along its whole line of descent, are supposed to have been but little modified, and they yet form a single genus. But this genus, though much isolated, will still occupy its proper intermediate position; for F originally was intermediate in character

F380    Book:     Darwin, C. R. 1860. The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. New York: D. Appleton. New edition, revised and augmented.   Text   Image   PDF

descent with modification are grave 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 course of successive generations have passed from some one part to the others. We are often wholly unable even to conjecture how this could have been effected. Yet, as we have reason to believe that some species

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

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 the same individual — EMBRYOLOGY, laws of, explained by variations not