BOOKS.
MR. DARWIN'S LAST WORK.*
WHATEVER view we may take of what is now commonly called Darwinism, there is one aspect of it under which the thanks of all persons are especially due to its author. Mr. Darwin has brought to the knowledge and adapted to the comprehension of a large portion of his fellow-men and women, formerly quite oblivious of the commonest facts of natural history, a countless number of ideas which had been hitherto regarded as the peculiar property of naturalists, and as being matters of no moment to any one else. When the Origin of Species was first published, we remember meeting in the train a friend, a lawyer, even then of some reputa- tion in his profession, and a man of more than common intelligence. "What a strange title for a book ! " he remarked, as he read it on the back of the volume we held on the opposite seat ; "what does it mean ? " We found that the only " species " of which he had a notion was the human species, and that not the slightest conception that the words "race," " genus," "class," and so forth, were definite terms, to which certain ab- stract ideas were attached, had ever entered his mind. A few months afterwards the phrases "struggle for existence" and "natural selection" were in the mouths even of young ladies at the dinner-table—and, thanks to the lucidity of Mr. Darwin's style, they were very generally and thoroughly " understanded of the people," with the exception of a certain number of those persons who, from their very tastes or studies, should have especially comprehended them. Since then we are certainly not exceeding the mark when we assert that a large majority both of the general public and, in this country, of scientific naturalists have given in their adhesion, more or less, to Darwinian principles.
We say more or less—because, as years have passed on, there has sprung up a not inconsiderable number of scientific men who declare that they have been Darwinians all their lives—that they were Darwinians, to a certain degree, before Darwinism was in- vented, and that there is nothing new in the principles its founder promulgated. It is very remarkable that of such men there is scarcely one who has thoroughly bottomed the theory—scarcely one who has effectually comprehended its nature. They may write about the "ordained continuous becoming of organic forms," or admit that species are not the results of separate and particular miracles in their origin ; but by what means this "continuous becoming" takes place, or whether it follows any rule at all, they cannot divine. If their hesitation arose from the cautious reluct- ance which every scientific man ought to feel before committing himself to the acceptance of a new theory, nothing could be said against it. It would be most proper and most commendable. Unfortunately there is reason to suspect that it springs from no such sentiment. It would rather seem due to the consideration, "The doctrine of natural selection was not invented by me. I must admit the facts on which it is grounded, but the undeniably logical results I will not recognize." This, we fear, has been the motive of one class of hostile critics. There is another class—free, indeed, from any such degrading motive of jealousy ; but from a scientific point of view hardly to be more highly esteemed. This class consists of the objectors who have never clearly understood (though of course they thought they did) what Mr. Darwin's great theory was, and are naturally unable to perceive its peculiar merits. They cannot see that it differs from the guesses of Lamarck or the dreams of the author of the Vestiges of Creation. The more intel- lectual of the first class possibly pass themselves off as belonging * The Variation of Animals and Plants under Domestication. By Charles Darwin, M.A., FAB., Sc. In 2 vols. London: 1868. Murray. to tie second. Anyhow, it appears to us that though there may be many followers of Mr. Darwin who fail to comprehend the theory he has rendered so celebrated, none of those who have publicly denounced it have succeeded in showing that they have thoroughly mastered its details.
When the Origin of Species appeared, its author undertook to publish, with all convenient speed, the collected facts on which he based his reasoning. Accordingly, we were shortly presented with a little work on the Fertilization of Orchids, and another on the Movements and Habits of Climbing Plants, each of which covered a small portion of the whole subject. Now we have before us the Variation of Animals and Plants under Domestication, the first of a promised trilogy, in the two successors of which we are to be led to consider the variability of organic beings in a state of nature,
and the validity of the principle of Natural Selection to account for the difficulties in the way of adopting it, of the presence of which difficulties no one seems more conscious than Mr. Darwin himself.
The bearing on the general question of the work now under review may be illustrated by comparing it to the common proof of a well known mathematical theorem. Certain properties may be proved for certain limited numbers in succession. If any indefi- nite number be taken, the same property may be proved to exist for the number next to it. Hence mathematicians conclude that the theorem is universally true. Mr. Darwin conceives that he is able to prove (and to us it appears that he is right) his theory to be true in the case of the small variations of certain species. He then takes a species as much at random as he can, and finds that his theory will hold good to account for the slight variations of that particular species. He consequently infers that it is true for all species. But there is this difference between our illustration and his present examples. The latter are somewhat restricted in number, and are under conditions not natural to them. Of course his opponents make the best use they can of this fact. Conse- quently, Mr. Darwin is led to consider at some length what may be the real causes of variability, the direct and definite action of the external conditions of life upon plants and animals, and to attempt the discovery of the laws by which variation may be governed. That variability is owing to certain causes no one, we think, can doubt. Whether any of those causes are already known to us, or will become so, is another matter. Whatever they may be, it is to us extremely unlikely that there is one set of them acting on species in their natural state, and another set acting on the same species when domesticated. And this, it appears to us, is the key to the whole position Mr. Darwin is trying to occupy, the importance of which, in his treatment of it, is not made sufficiently manifest. Once prove that the causes of variability in domesticated and wild species are of the same nature, and the class of objectors of whom we are now speaking is answered. But the difficulty of proving this point, though its probability be of the highest, seems to remain. Notwithstanding the enormous array of facts amassed by Mr. Darwin, we cannot look on the point as established. Its likelihood is only increased, though increased immeasurably.
Mr. Darwin brings to his aid a new ally. He has thought out a "provisional hypothesis of Pangenesis " :—
"It is almost universally admitted that cells, or the units of the body, propagate themselves by self-division or proliferation, retaining the same nature, and ultimately becoming converted into the various tissues and substances of the body. But besides this means of increase I assume that cells, before their conversion into completely passive or formed material,' throw off minute gemmules or atoms, which circulate freely throughout the system, and when supplied with proper nutriment multiply by self-division, subsequently becoming developed into cells like those from which they were derived. These gemmules for the sake of distinctness may be called cell-gemmules, or, as the cellular theory is not fully established, simply gemmules. They are supposed to be transmitted from the parents to the offspring, and are generally developed in the generation which immediately succeeds, but are often transmitted in a dormant state during many generations and are then developed. Their development is supposed to depend on their union with other partially developed cells or gemmules which precede them in the regular course of growth. Why I use the term union, will be seen when we discuss the direct action of pollen on the tissues of the mother-plant. Gemmules are supposed to be thrown off by every cell or unit, not enly during the adult state, but during all the stages of development. Lastly, I assume that the gemmules in their dormant state have a mutual affinity for each other, leading to their aggregation either into buds or into the sexual elements. Hence, speaking strictly, it is not the reproductive elements nor the buds, which generate new organisms, but the cells themselves throughout the body. These assumptions constitute the provisional hypothesis which I have called Pangenesis." (Vol. ii., p. 374.) This hypothesis, as Mr. Darwin shows, is not exactly new. Buffon, Bonnet, Professor Owen, and especially Mr. Herbert Spencer, have uttered opinions in a manner approaching it. But Mr. Darwin goes beyond them all. He has pat forth an hypothesis which it will take physiologists some time to digest, and when they have digested it, some time must elapse before they can declare it to be wholesome or the contrary. At present we cannot but re- gard it with suspicion. It seems like an unwieldy weapon of very doubtful utility under the circumstances, just as likely to bring defeat on its employer as victory, like a huge cannon dragged in the train of a barbarous potentate, clogging his movements, and hindering him from a rapid advance whereby he might gain his end. The historian of the Crimean War tells us that our foes lost the battle of the Alma, which they had all but won, through fear of risking a single piece of artillery. It seems to us that- in em- ploying his energies to preserve this new, or quasi-new, hypothesis with which he has unnecessarily encumbered himself, Mr. Darwin places his beautiful and all but proved theory of Natural Selection in great jeopardy. If the new hypothesis be overturned, what becomes of the older theory to support which it was brought into the field ?
Leaving, then, this part of the work to the criticism of the future, we will return to the earlier portions, in which the author arrays, as bearing on his subject, facts and opinions innumerable, with a patience truly German in its application, and with a practical consequence that would drive an average German to despair. There may be inquirers who have laboured more abundantly and have therefore attained greater knowledge of the matters treated ; but we doubt if there is another man in the world who could exhibit in so small a space and in a manner so orderly the results of researches, at once experimental and literary, carried on to an extent so truly marvellous. The old familiar illustrations of the elephant's trunk or the Nasmyth hammer occur immediately to one's mind. Mr. Darwin descends on a poultry book, and out rolls a ripe kernel of fact, hitherto hidden in a shell, where it had been of no other use than to feed a maggot. Again, he comes down on a rough mass of metal, like Pallas's doctrine of the origin of domestic races, and after a squeeze or two there lies before us a goodly forging, ready wrought and fit to serve as a pillar or beam in the edifice he is constructing. He will pick up a pin from the Racing Calendar, or brandish a battle-axe in the face of a transcendental anatomist. It is, above all, curious to mark the way in which he has identified himself with the fanciers of plants and animals. He falls into their slang phrases, and seems almost unwilling or unable to escape from their pre- judices. Such and such a strain "breeds true," is one of his con- stant expressions, though his language is in general a model of correctness, and the fact of different strains breeding so " true " appears to hamper him, to make him hesitate, and almost to hinder him from trusting his own theory. Time and again he has to gird himself to the effort of overthrowing the common superstition of breeders that our pigeons or our poultry have descended from no one knows how many distinct species, and it is only by continually refreshing himself, as with a cordial, by reflecting on the recent establishment of certain new races (such as the " Himalaya " rabbit, the Ancon sheep, or the Niata cattle), the history of whose production is perfectly well known, that he finds himself equal to his task.
The variability of species under domestication is abundantly proved ;—after one of the woodcuts (vol. i., p. 328) we shall never againbe able to use the proverb " as like as two peas." It remains for Mr. Darwin to show the variability of species in a state of nature. This, we apprehend, will not be a very difficult task ; but, as we have above indicated, he seems to us not to have proved that the cause of variability is the same in both cases, for the "provisional hypothesis of Pangenesis " rests on far too many assumptions to be accepted at present, and until the cause in each case is shown to be identical, one class of Mr. Darwin's objectors will not be refuted. The class of his opponents which consists of bigots, or persons jealous of his discovery of the theory of Natural Selection, may be safely left to become extinct, as it will assuredly cease with the lives of those who come under the category.
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