Скачать книгу

Summary Of The Preceding And Present Chapters

       Chapter 12 Geographical Distribution

       1.

       2. Single Centres Of Supposed Creation

       3. Means Of Dispersal

       4. Dispersal During The Glacial Period

       5. Alternate Glacial Periods In The North And South

       Chapter 13 Geographical Distribution—continued

       1. Fresh-Water Productions

       2. On The Inhabitants Of Oceanic Islands

       3. Absence Of Batrachians And Terrestrial Mammals On Oceanic Islands

       4. On The Relations Of The Inhabitants Of Islands To Those Of The Nearest Mainland

       5. Summary Of The Last And Present Chapters

       Chapter 14 Mutual Affinities Of Organic Beings: Morphology — Embryology — Rudimentary Organs

       1. Classification

       2. Analogical Resemblances

       3. On The Nature Of The Affinities Connecting Organic Beings

       4. Morphology

       5. Development And Embryology

       6. Rudimentary, Atrophied, And Aborted Organs

       7. Summary

       Chapter 15 Recapitulation And Conclusion

       Glossary Of The Principal Scientific Terms Used In The Present Volume

       On the tendency of species to form varieties

      On the Origin of Species, 6th Edition - Charles Darwin

      “But with regard to the material world, we can at least go so far as this— we can perceive that events are brought about not by insulated interpositions of Divine power, exerted in each particular case, but by the establishment of general laws.”—Whewell: “Bridgewater Treatise”.

      “The only distinct meaning of the word ‘natural’ is STATED, FIXED or SETTLED; since what is natural as much requires and presupposes an intelligent agent to render it so, i.e., to effect it continually or at stated times, as what is supernatural or miraculous does to effect it for once.”—Butler: “Analogy of Revealed Religion”.

      “To conclude, therefore, let no man out of a weak conceit of sobriety, or an ill-applied moderation, think or maintain, that a man can search too far or be too well studied in the book of God’s word, or in the book of God’s works; divinity or philosophy; but rather let men endeavour an endless progress or proficience in both.”—Bacon: “Advancement of Learning”.

      I will here give a brief sketch of the progress of opinion on the Origin of Species. Until recently the great majority of naturalists believed that species were immutable productions, and had been separately created. This view has been ably maintained by many authors. Some few naturalists, on the other hand, have believed that species undergo modification, and that the existing forms of life are the descendants by true generation of pre existing forms. Passing over allusions to the subject in the classical writers (Aristotle, in his “Physicae Auscultationes” (lib.2, cap.8, s.2), after remarking that rain does not fall in order to make the corn grow, any more than it falls to spoil the farmer’s corn when threshed out of doors, applies the same argument to organisation; and adds (as translated by Mr. Clair Grece, who first pointed out the passage to me), “So what hinders the different parts (of the body) from having this merely accidental relation in nature? as the teeth, for example, grow by necessity, the front ones sharp, adapted for dividing, and the grinders flat, and serviceable for masticating the food; since they were not made for the sake of this, but it was the result of accident. And in like manner as to other parts in which there appears to exist an adaptation to an end. Wheresoever, therefore, all things together (that is all the parts of one whole) happened like as if they were made for the sake of something, these were preserved, having been appropriately constituted by an internal spontaneity; and whatsoever things were not thus constituted, perished and still perish.” We here see the principle of natural selection shadowed forth, but how little Aristotle fully comprehended the principle, is shown by his remarks on the formation of the teeth.), the first author who in modern times has treated it in a scientific spirit was Buffon. But as his opinions fluctuated greatly at different periods, and as he does not enter on the causes or means of the transformation of species, I need not here enter on details.

      Lamarck was the first man whose conclusions on the subject excited much attention. This justly celebrated naturalist first published his views in 1801; he much enlarged them in 1809 in his “Philosophie Zoologique”, and subsequently, 1815, in the Introduction to his “Hist. Nat. des Animaux sans Vertebres”. In these works he up holds the doctrine that all species, including man, are descended from other species. He first did the eminent service of arousing attention to the probability of all change in the organic, as well as in the inorganic world, being the result of law, and not of miraculous interposition. Lamarck seems to have been chiefly led to his conclusion on the gradual change of species, by the difficulty of distinguishing species and varieties, by the almost perfect gradation of forms in certain groups, and by the analogy of domestic productions. With respect to the means of modification, he attributed something to the direct action of the physical conditions of life, something to the crossing of already existing forms, and much to use and disuse, that is, to the effects of habit. To this latter agency he seems to attribute all the beautiful adaptations in nature; such as the long neck of the giraffe for browsing on the branches of trees. But he likewise believed in a law of progressive development, and as all the forms of life thus tend to progress, in order to account for the existence at the present day of simple productions, he maintains that such forms are now spontaneously generated. (I have taken the date of the first publication of Lamarck from Isidore Geoffroy Saint-Hilaire’s (“Hist. Nat. Generale”, tom. ii. page 405, 1859) excellent

Скачать книгу