In a celebrated geologist, Count Keyserling (Bulletin de la Soc. Géolog., 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, , Dr. Schaaffhausen published an excellent pamphlet (Verhand. des Naturhist. Vereins der Preuss. Rheinlands, 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 (Etudes sur Geograph Bot. tom. i, page 250), “On voit que nos recherches sur la fixité ou la variation de l’espèce, nous conduisent directement aux idées émises par deux hommes justement célèbres, 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, . 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 , 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 (see Prof. Rudolph Wagner, Zoologisch-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 , 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 preexisting 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 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 , 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 , and the second edition on .
Introduction
When on board H.M.S. Beagle, as naturalist, I was much struck with certain facts in the distribution of the organic beings inhabiting South America, and in the geological relations of the present to the past inhabitants of that continent. These facts, as will be seen in the latter chapters of this volume, seemed to throw some light on the origin of species—that mystery of mysteries, as it has been called by one of our greatest philosophers. On my return home, it occurred to me, in , that something might perhaps be made out on this question by patiently accumulating and reflecting on all sorts of facts which could possibly have any bearing on it. After five years’ work I allowed myself to speculate on the subject, and drew up some short notes; these I enlarged in into a sketch of the conclusions, which then seemed to me probable: from that period to the present day I have steadily pursued the same object. I hope that I may be excused for entering on these personal details, as I give them to show that I have not been hasty in coming to a decision.
My work is now () nearly finished; but as it will take me many more years to complete it, and as my health is far from strong, I have been urged to publish this abstract. I have more especially been induced to do this, as Mr. Wallace, who is now studying the natural history of the Malay Archipelago, has arrived at almost exactly the same general conclusions that I have on the origin of species. In he sent me a memoir on this subject, with a request that I would forward it to Sir Charles Lyell, who sent it to the Linnean Society, and it is published in the third volume of the journal of that society. Sir C. Lyell and Dr. Hooker, who both knew
