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ment nuancée. Au contraire les espèces sont distinctes entre elles, par la raison décisive, qu'il n'y a entre elles qu'une fécondité bornée. J'ai déja dit cela, mais je ne saurais trop le redire' (34).
These very obvious truths M. Flourens confirms by a quotation from Buffon : "The comparison of the resemblance of individuals is but an accessory idea, and often independ. ent of the first-the constant succession of individuals by generation for the ass is more like the horse than the water. spaniel is to the greyhound, and nevertheless the waterspaniel and the greyhound are but one species, since they produce together individuals which can themselves produce others in the same way, whereas the ass and the horse are certainly of different species, since they produce together only faulty and sterile animals. *
This brief explanation is to be found more at length in other passages of Buffon's Natural History, and one of these will be found in the note.f The whole subject is lucidly stated in Müller's Elements of Physiology. We are compelled, for brevity's sake, to refer the reader to the work itself.
Thus then the matter stands; the mixture of species * Buffon, Histoire de l'âne.
† 'D'ailleurs il y a encore un avantage pour reconnoître les espèces d'animaux, et pour les designer les uns des autres, c'est qu'on doit regarder comme la même espèce celle qui, au moyen de la copulation, se perpetue, et conserve la similitude de cette espèce, et comme des espèces différentes celles qui par les mêmes moyens ne peuvent rien produire ensemble ; de sorte qu'un renard sera une espèce différente d'un chien, si en effet par la copulation d'un mâle et d'une femelle de ces deux espèces il ne resulte rien ; et quand même il en résulterait un animal mi-parti, une espèce de mulet, comme ce mulet ne produirait rien, cela suffiroit pour établir que le renard et le chien ne seroient pas de la même espèce, puisque nous avons supposé que pour constituer une espèce, il falloit une production continue, perpétuelle, invariable, semblable en un mot à cette des autres avimaux' (x. 285).
# Vol. II. p. 1661.
produces a hybrid progeny when there is any product at all, and this hybrid progeny cannot with its hybrid congeners have any descendants. The union of the dog and jackal, like that of the horse and ass, may produce a hybrid or mule, but these mule-animals united with other mules are sterile. The hybrid dog-jackal, with either dog or jackal, that is, with either side of the pure races, may have progeny ; and, supposing the father to be a dog, the progeny of the second experiment will approach much nearer the dog than the progeny of the first experiment. This, repeated in the next generation by a dog-father, will produce an animal all but a dog, and in the fourth generation the result will be a pure dog, all trace of mixture having disappeared. Mules, amongst themselves, are always unproductive; and, as the mule is the attempt at a new animal, that attempt fails, for the artificial breed cannot be continued.
Animals of the same species, but distinguished as a race, however dissimilar in appearance, such as the bloodhound, and water-dog, are prolific in their descendants, the descendants will be fertile mongrels, but not hybrids.
All the races of dogs are fertile with one another, and their fecundity continues in their descendants, whatever the mixture may have been. Yet these mongrels continue to be dogs; no new animal is formed, and the boundaries of this which we call species are not transgressed. We can. not make a race of new animals.
Cuvier has remarked: ‘La nature a soin d'empêcher l'alteration des espèces, qui pourroit résulter de leur mélange, par l'aversion mutuelle qu'elle leur a donnée : il faut toutes les ruses, toute la contrainte de l'homme pour faire contracter ces unions, même aux espèces qui se ressemblent le plus ..... aussi ne voyons nous pas dans nos bois d'individus intermédiaires entre le lièvre et le lapin, entre le cerf et le daim, entre la marte et la fouine?' (Discours preliminaire, p. 76.)
This is confirmed by Lyell, in an interesting passage specially in reference to the vegetable kingdom, in his Principles of Geology, third edition (ii. 390).
The celebrated John Hunter has observed that the true distinction of species must ultimately be gathered from their incapacity of propagating with each other, and producing offspring capable of again continuing itself; and Lyell, in adducing his testimony, observes that no proof has been obtained that a true hybrid race can be perpetuated.
De Candolle, after discussing the subject, concludes with these words : 'I see, then, that there exist in organized beings permanent differences which cannot be referred to any one of the actual causes of variation, and these differences are what constitute species.' (Essai elémentaire.)
The following passage in Lyell’s Geology (at least in the earlier editions) is well worthy of observation ; for though written against Lamarck, the true founder of Mr Darwin's theory, and several years before 'The Origin of Species' was published, it is, in fact, a home-thrust at Mr Darwin.
'I may remark that if it could be shown that a single permanent species had ever been produced by hybridity (of which there is no satisfactory proof), it might certainly have lent some countenance to the notions of the ancients respecting the gradual deterioration of created things, but none whatever to Lamarck's (Darwin's) theory of their progressive perfectibility, for observations have hitherto shown that there is a tendency in mule animals and plants to degenerate in organization' (ii. 336).
The sentiments uttered by other physiologists are repeated by Lawrence,* who quotes in confirmation the words of Cuvier. “I have carefully examined the figures of animals and birds engraven on the numerous obelisks brought from Egypt to ancient Rome. In the general character, which is all that can have been preserved, these representations perfectly resemble the originals, as we now see them. My learned colleague, M. Geoffroy St Hilaire, collected numerous mummies of animals from the sepulchres and temples of Upper and Lower Egypt. He brought away cats, ibises, birds of prey, dogs, monkeys, crocodiles, and an ox's head, embalmed. There is no more difference between these relics and the animals we are now acquainted with, than between the human mummies and the skele. tons of the present day.'t
Lawrence concludes his disquisition on the subject thus : We may conclude, then, from a general review of the preceding facts, that nature has provided, by the insurmountable barrier of instinctive aversion, of sterility in the hybrid offspring, and in the allotment of species to different parts of the earth, against any corruption or change of species in wild animals. We must therefore admit, for all the species which we know at present, as sufficiently distinct and constant, a distinct origin and common date' (200).
With all this evidence we are enabled to see that in the realities of nature the system of constant mutation can have no place, and that it must be restricted to the region of the imagination where it had its origin. We shall see ere long that Mr Darwin virtually accedes to the general
* See Lawrence's Lectures on Physiology (261), first edition. † Cuvier's Recherches sur les ossemens (Discours preliminaire, p. 71).
deductions of other naturalists on this subject, by the concessions which he makes; indeed other writers, who are partially of his way of thinking, and who even more confidently reject the idea of creation, cannot but admit the actual fixedness of the forms of life upon the earth. M. Pouchet, a bold advocate of spontaneous generation for the origin of vertebrated life and a eulogist both of Lamarck and Darwin, acknowledges that it is only by supposing an immense period of time for the process that we can believe in a change of species. “For us,' says he, 'if species be fixed, it is in the manner of the sun—that is to say, we cannot perceive the movement, so little are we in the account of time. It requires thousands of ages perhaps to establish a displacement of the sun or a transformation of a species' (193). In other words, there is no evidence to be had of such a transformation ; we are to imagine there. fore that it may be.
M. Pouchet has established his position* by well-selected and convincing evidence of facts, and concludes his examination of the subject with these words :
'Du moins reste-t-il vrai et prouvé que, quand deux races très-differentes s'unissent, il ne faut esperer rien de bon non plus que rien de durable de leur union' (156).
Nou this we may say is the evidence of an opponent and therefore doubly valuable ; for if an advocate of muta. bility of species can thus go out of the way to show the difficulty of mixing races, with any hope of a durable progeny, much less can he pretend to change species. As long as the learned author keeps within the region of facts and the known history of nature he tells us the real truth; but when he gets into solar cycles and manwantaras of
* 'Un type moyen ne peut exister par lui-même.'