Every period of a science has its own tendency; at given moments the efforts of all tend involuntarily towards one sole end,—one question absorbs all, and all partial solutions tend to the same general solution. At the present day, the great question in natural history is that of species; inquiries are ardently pursued, and materials are produced from every side,—opinions are mooted, and objections raised. We have only to call attention on this point to the works of Isidore Geoffroy, Morton, Nott, Godron, Broca,[285] Darwin, Fée, etc. The question of spontaneous generation is but a phase of the same discussion, an episode in the work of the birth of time.
Some people have made a sort of bugbear out of this word spontaneous generation, or rather, spontaneous genesis.[286] And yet, here is one of these truths to which, we think, we shall be led by the observation of facts and by reasoning. The great harm of examining into the question is to be strangely mistaken as to its bearing, and inclined to restrict its limits. It has, in fact, been said, that every day genital organs are discovered in beings whom it was thought were reproduced spontaneously. This is a specious argument to which Plutarch has long ago done justice. A person, whom he brings forward in one of his books, asks, “Which had the first existence, the egg or the hen?” and concludes that “it was evidently the hen.” Even in treating lightly on this subject,—in making it a familiar conversation, the Greek physician was, however, not mistaken about the importance of the matter. “So that,” answers one of the guests, “with this little question of the egg and the hen, we raise, as with a lever, the great and dark question of the generation of the world.”[287]
That the animals which we know all reproduce by eggs, is possible, although it has not been proved, but this is not an important point; we want to know if all the animals which we are able to observe do not remount necessarily, in a more or less direct manner, and at a more or less distant period, to a spontaneous beginning.[288] The difficulty is everywhere the same,—everywhere we arrive at that immense obscurity which envelopes the origin of life on the surface of our planet; but it is essential in every case not to give to the phenomenon of spontaneous beginning any other signification than it ought to have. We must not believe, for instance, that matter is formed by the agglomeration of parts which do not yet live in a perfect being, having already all its organs distributed and proportionate, uniting in one living whole. This would be to cast ourselves on the field of an absolutely improbable hypothesis. Histology teaches us that each animal, its instincts and intellect included, is at a given moment merely a mass of amorphous matter, which, at a later period, will form itself, or in the midst of which will be spontaneously developed an anatomical element, that is to say, an organised body. To admit spontaneous genesis, then, is simply to admit the formation of organic amorphous primitive matter apart from an already living body, at the cost of and in the heart of which can be born the initial anatomical element of one of these animals, very properly called protozoa. We can even ask, whether this latent primary life, this atomic life, has not always been the ruling life on our planet.[289] And since, when account is taken of everything, we are almost entirely ignorant of the conditions necessary to the fecundity of any primitive embryo, excepting certain physical conditions of temperature, liquidity, etc.; and as, on the other hand, nothing authorises us to believe that the laws existing at the origin of life on our planet have since been abrogated, we see that, if we must necessarily conclude a spontaneous primitive genesis, there is nothing irrational in admitting, until we know farther on the subject, the persistence of the phenomenon.
Let us return to the subject of species, which, however, we did not quite leave in speaking on the subject of spontaneous generation. Isidore Geoffroy wishes to advance slowly in this matter, and only when facts become patent to all. But he himself has more than once shown, by a noble example, the benefits which science obtains by casting itself beyond the limits of fact, provided that care is taken at first not to give more than a simple hypothetical value to that which we may desire to bring forward. In the question which occupies our attention, we must embrace at one glance the whole animal kingdom since its commencement, in order to deduce the truth of facts which have been observed; only then these relations, for which science so ardently seeks, would appear in their proper light. On account of this impossibility, we must hope for some more enlightenment, chiefly from geology, and perhaps from experiments. “How many facts would be necessary,” said Buffon, “in order to pronounce authoritatively, or even to conjecture? How many experiments are to be tried in order to discover these facts, to acknowledge them, or even to anticipate them by well-founded conjectures?”
Two opinions on the origin of species deserve to be noticed,—those of Cuvier and Lamarck. This last held Buffon’s opinions at the end of his career, and it ought to find in Étienne Geoffroy a defender even more powerful in our eyes than Isidore Geoffroy himself; and especially Darwin, to whom belongs the merit, however, of having propagated, in his popular work, the ideas of Lamarck.
Cuvier’s theory seems to be still the dominant one; it is surrounded by that scholastic prestige which is explained by the word classical; it is only fit for universities. Cuvier proclaimed the immutability of species, and wished that at every revolution of the globe (the word alone then made his fortune), a new fauna might come ready made from the hands of God, to animate the burning or icy lands of the old world. But Cuvier, in proclaiming organic immutability, excepted mankind. We must be allowed to doubt whether it was done with good faith. “Cuvier, full of good taste regarding political propriety,” said a son of the republic, his former master, now his adversary,—“Cuvier, filling his mind with wise mental reservations concerning the future of society, declared that it was not fitting that new discoveries, just dug from the heart of the earth, should attack and oppose with hostile malignity the venerated and ancient revelations of our holy books.”[290] This remark, in which Étienne Geoffroy has concealed his anger and contempt under a guise of perfect urbanity, will remain to the end, we are convinced, as the judgment of posterity upon the naturalist statesman, and upon that which they call in France at the present day official science. Species was, then, a definite entity in Cuvier’s opinion, and if he had been consistent, he would doubtless have become the promoter of the idea which has been taken up by Agassiz,—that there were several centres of creation on the surface of our planet after the last flood; in each of these centres would appear a special fauna, and also one of the species constituting the genus homo.
These different species of men and these different fauna would since have continued to occupy the same geographical areas with merely some alteration. An absolute value is given to species in Cuvier’s theory, as well as in that of Agassiz; it is unchangeable; it may disappear, but cannot be modified, so that “each of them,” as Buffon said at the commencement of his career, when he held the same views, “remains always separated from the others by an interval which nature cannot overstep.”[291]
Such has been, for a long time, the theory of the origin of species which we have held, and which we maintained in the first edition of this book. In fact, the solution which we now offer differs considerably from that which we then gave. But there is evolution rather than contradiction in going from one to the other. The differences which separate mankind are not lessened, and have not diminished in value in our eyes: we merely explain these differences in another way. It cannot be called contradiction, or even inconsistency, to change one’s manner of viewing things with the times; to regard things otherwise which, as we said before, have no absolute basis; or to change in five years one’s opinion concerning the origin of the living beings on the surface of the globe.
In Buffon’s last opinion[292] species was not that definite entity in which Cuvier believed, commencing at a given geological moment, in order to terminate at another. Buffon says, in his latest works, that the idea of species can only be seized upon by man at “this or that instant of his age,”[293] and that it is merely the expression of the ambient medium. Let this remain as before, it will not change; but when the conditions of the medium become modified, species will change. We thus arrive at this definition:—
Definition.—“Species is a collection or group of individuals characterised by a similarity of distinctive points; the transmission of which is accomplished naturally, regularly, and indefinitely, in a given order of things.”[294]