of his views would be superfluous on my part. 4 Mr. Herbert Spencer, in an Essay (originally published in the "Leader", March, 1852, and republished in his "Essays", in 1858), has contrasted the theories of the Creation and the Development of organic beings with remarkable skill and force. He argues from the analogy of domestic productions, from the changes which the embryos of many species undergo, from the difficulty of distinguishing species and varieties, and from the principle of general gradation, that species have been modified; and he attributes the modification to the change of circumstances. The author (1855) has also treated Psychology on the principle of the necessary acquirement of each mental power and capacity by gradation. In 1852 M. Naudin, a distinguished botanist, expressly stated, in an admirable paper on the Origin of Species ("Revue Horticole", page 102; since partly republished in the "Nouvelles Archives du Museum", tom. i, page 171), his belief that species are formed in an analogous manner as varieties are under cultivation; and the latter process he attributes to man's power of selection. But he does not show how selection acts under nature. He believes, like Dean Herbert, that species, when nascent, were more plastic than at present. He lays weight on what he calls the principle of finality, "puissance mysterieuse, indeterminee; fatalite pour les uns; pour les autres volonte providentielle, dont l'action incessante sur les etres vivantes determine, a toutes les epoques de l'existence du monde, la forme, le volume, et la duree de chacun d'eux, en raison de sa destinee dans l'ordre de choses dont il fait partie. C'est cette puissance qui harmonise chaque membre a l'ensemble, en l'appropriant a la fonction qu'il doit remplir dans l'organisme general de la nature, fonction qui est pour lui sa raison d'etre." (From references in Bronn's "Untersuchungen uber die Entwickelungs-Gesetze", it appears that the celebrated botanist and palaeontologist Unger published, in 1852, his belief that species undergo development and modification. Dalton, likewise, in Pander and Dalton's work on Fossil Sloths, expressed, in 1821, a similar belief. Similar views have, as is well known, been maintained by Oken in his mystical "Natur-Philosophie". From other references in Godron's work "Sur l'Espece", it seems that Bory St. Vincent, Burdach, Poiret and Fries, have all admitted that new species are continually being produced. I may add, that of the thirty-four authors named in this Historical Sketch, who believe in the modification of species, or at least disbelieve in separate acts of creation, twenty-seven have written on special branches of natural history or geology.) In 1853 a celebrated geologist, Count Keyserling ("Bulletin de la Soc. Geolog.", 2nd Ser., tom. x, page 357), suggested that as new diseases, supposed to have been caused by some miasma have arisen and spread over the world, so at certain periods the germs of existing species may have been chemically affected by circumambient molecules of a particular nature, and thus have given rise to new forms. In this same year, 1853, Dr. Schaaffhausen published an excellent pamphlet ("Verhand. des Naturhist. Vereins der Preuss. Rhein-lands", etc.), in which he maintains the development of organic forms on the earth. He infers that many species have kept true for long periods, whereas a few have become modified. The distinction of species he explains by the destruction of intermediate graduated forms. "Thus living plants and animals are not separated from the extinct by new creations, but are to be regarded as their descendants through continued reproduction." A well-known French botanist, M. Lecoq, writes in 1854 ("Etudes sur Geograph." Bot. tom. i, page 250), "On voit que nos re-cherches sur la fixite ou la variation de l'espece, nous conduisent directement aux idees emises par deux hommes justement celebres, Geoffroy Saint-Hilaire et Goethe." Some other passages scattered through M. Lecoq's large work make it a little doubtful how far he extends his views on the modification of species. The "Philosophy of Creation" has been treated in a masterly manner by the Rev. Baden Powell, in his "Essays on the Unity of Worlds", 1855. Nothing can be more striking than the manner in which he shows that the introduction of new species is "a regular, not a casual phenomenon," or, as Sir John Herschel expresses it, "a natural in contradistinction to a miraculous process." The third volume of the "Journal of the Linnean Society" contains papers, read July 1, 1858, by Mr. Wallace and myself, in which, as stated in the introductory remarks to this volume, the theory of Natural Selection is promulgated by Mr. Wallace with admirable force and clearness. Von Baer, toward whom all zoologists feel so profound a respect, expressed about the year 1859 (see Prof. Rudolph Wagner, "Zool-ogisch-Anthropologische Untersuchungen", 1861, s. 51) his conviction, chiefly grounded on the laws of geographical distribution, that forms now perfectly distinct have descended from a single parent-form. In June, 1859, Professor Huxley gave a lecture before the Royal Institution on the "Persistent Types of Animal Life". Referring to such cases, he remarks, "It is difficult to comprehend the meaning of such facts as these, if we suppose that each species of animal and plant, or each great type of organisation, was formed and placed upon the surface of the globe at long intervals by a distinct act of creative power; and it is well to recollect that such an assumption is as unsupported by tradition or revelation as it is opposed to the general analogy of nature. If, on the other hand, we view "Persistent Types" in relation to that hypothesis which supposes the species living at any time to be the result of the gradual modification of pre-existing species, a hypothesis which, though unproven, and sadly damaged by some of its supporters, is yet the only one to which physiology lends any countenance; their existence would 5 seem to show that the amount of modification which living beings have undergone during geological time is but very small in relation to the whole series of changes which they have suffered." In December, 1859, Dr. Hooker published his "Introduction to the Australian Flora". In the first part of this great work he admits the truth of the descent and modification of species, and supports this doctrine by many original observations. The first edition of this work was published on November 24, 1859, and the second edition on January 7, 1860. Contents AN HISTORICAL SKETCH OF THE PROGRESS OF OPINION ON THE ORIGIN OF SPECIES DETAILED CONTENTS. ORIGIN OF SPECIES. INTRODUCTION. CHAPTER I. VARIATION UNDER DOMESTICATION CHAPTER II. VARIATION UNDER NATURE CHAPTER III. STRUGGLE FOR EXISTENCE CHAPTER IV. NATURAL SELECTION; OR THE SURVIVAL OF THE FITTEST CHAPTER V. LAWS OF VARIATION CHAPTER VI. DIFFICULTIES OF THE THEORY CHAPTER VII. MISCELLANEOUS OBJECTIONS TO THE THEORY OF NATURAL SELECTION CHAPTER VIII. INSTINCT CHAPTER IX. HYBRIDISM CHAPTER X. ON THE IMPERFECTION OF THE GEOLOGICAL RECORD CHAPTER XI. ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS CHAPTER XII. GEOGRAPHICAL DISTRIBUTION CHAPTER XIII. GEOGRAPHICAL DISTRIBUTION--continued CHAPTER XIV. MUTUAL AFFINITIES OF ORGANIC BEINGS CHAPTER XV. RECAPITULATION AND CONCLUSION GLOSSARY OF THE PRINCIPAL SCIENTIFIC TERMS USED IN THE PRESENT VOLUME. INDEX. DETAILED CONTENTS. INTRODUCTION CHAPTER I. VARIATION UNDER DOMESTICATION. Causes of Variability--Effects of Habit and the use or disuse of Parts--Correlated Variation--Inheritance--Character of Domestic Varieties--Difficulty of distinguishing between Varieties and Species--Origin of Domestic Varieties from one or more Species--Domestic Pigeons, their Differences and Origin--Principles of Selection, anciently followed, their Effects--Methodical and Unconscious 6 Selection--Unknown Origin of our Domestic Productions--Circumstances favourable to Man's power of Selection. CHAPTER II. VARIATION UNDER NATURE. Variability--Individual Differences--Doubtful species--Wide ranging, much diffused, and common species, vary most--Species of the larger genera in each country vary more frequently than the species of the smaller genera--Many of the species of the larger genera resemble varieties in being very closely, but unequally, related to each other, and in having restricted ranges. CHAPTER III. STRUGGLE FOR EXISTENCE. Its bearing on natural selection--The term used in a wide sense--Geometrical ratio of increase--Rapid increase of naturalised animals and plants--Nature of the checks to increase--Competition universal--Effects of climate--Protection from the number of individuals--Complex relations of all animals and plants throughout nature--Struggle for life most severe between individuals and varieties of the same species; often severe between species of the same genus--The relation of organism to organism the most important of all relations. CHAPTER IV. NATURAL SELECTION; OR THE SURVIVAL OF THE FITTEST. Natural Selection--its power compared with man's selection--its power on characters of trifling importance--its power at all ages and on both sexes--Sexual Selection--On the generality of intercrosses between individuals of the same species--Circumstances favourable and unfavourable to the results of Natural Selection, namely, intercrossing, isolation, number of individuals--Slow action--Extinction caused by Natural Selection--Divergence of Character, related to the diversity of inhabitants of any small area and to naturalisation--Action of Natural Selection, through Divergence of Character and Extinction, on the descendants from a common parent--Explains the Grouping of all organic beings--Advance in organisation--Low forms preserved--Convergence of character--Indefinite multiplication of species--Summary. CHAPTER V. LAWS OF VARIATION. Effects of changed
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