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Notices of Books.

The Variation of Animals and Plants under Domestication. By Charles Darwin, M.A., F.R.S., &c. London: J. Murray. 2 vols., 8vo, pp. 897. Woodcuts.

Mr. Darwin's work on domesticated animals and plants, whose appearance we announced a fortnight ago, is one of such importance to both the practical and theoretical gardener, as well as to all those persons with whom the gardener is most closely associated, professionally and socially, that it must claim a large share of our attention, no less on this account than for its special merits, and the stores of information it contains. Written in admirable English, using no scientific terms but such as are comprehensible to men of fair education, lucidly arranged, and indexed with scrupulous care, there is not a gardener in the country who has any taste for the history or theory of his art but will peruse it with pleasure and profit, and find it difficult to say whether he values it more as a storehouse of facts or as an incitement to observe and to think. Is his employer a sportsman? he will find in Mr. Darwin's pages such information regarding dogs and horses, their breeds and individualities, as never entered the brain of the gamekeeper, equerry, or master of the hounds. Is he a farmer? here are anecdotes and observations regarding cattle, pigs, sheep, and goats, which no professional breeder can match for number or truth, and which too few of these will believe or care about, not because they are not true, but because most so-called practical men take no interest in animals beyond what immediately concerns themselves. Is my lady a fowl fancier, or has she an aviary? her gardener will here find a wealth of information on domesticated birds of all sizes, voices, and uses, from the canary bird and peacock to the turkey and goose. Lastly, do his master's children seek his advice about their rabbits, pigeons, honey bees, goldfish, or silkworms? if they do, here are curiosities of natural history about each and all, treated with masterly skill and originality. With regard to these zoological subjects, we must confine ourselves to recommending the study of them in Mr. Darwin's pages to those who have time to do so, and proceed briefly to expound the purpose and method of this remarkable book in so far as it is devoted to the vegetable kingdom.

When Mr. Darwin brought out his well-known work "On the Origin of Species," he made it clear to all who would take the trouble to read those passages that the said work was but a resumé of the principal facts on which his theory was based; and he added that if life and health were granted him, he would not fail to bring before the public the data upon which he had reasoned. This was eight years ago, and the interval has (despite continuous ill-health) been spent partly in arranging the said materials, and partly in largely adding to them. These additions have appeared before the main body of the work, chiefly in the shape of two independent works—"On the Fertilisation of Orchids," and on "The Movements of Climbing Plants," and partly in a series of papers on the dimorphic and trimorphic conditions of such plants as Primroses, Linums and Lythrums, which are published in the Linnæan Society's Journal. Of the subjects treated of in the present volumes, several are as important as the above, or more so, and are certainly as laborious and exhaustive as the chapters on the variations of rabbits, domestic pigeons, fowls, and on the crossing of plants &c.; but as these did not contain any equally novel or striking discoveries, or develop any new principles, Mr. Darwin has here thrown them in with the general store.

The object of the work then is to demonstrate, by facts and observations, the amount and nature of the changes which animals and plants have undergone during or since domestication; its object, moreover, is to prove that these changes are so much greater and so much more easily brought about than is commonly supposed, and are so similar in kind and results to what nature more leisurely effects, and are so certainly amenable to known conditions of life, that they may be taken, in whole or in part, as exponents of those fixed laws, to the operation of which we may trace, more or less clearly, the development of all past and present organisms, however complicated, out of one or a few primordial organisms of the simplest conceivable structure.

Mr. Darwin's Introduction, a short affair of some dozen pages, is exceedingly well drawn up, and will put what were somewhat obscure subjects as they stood in the "Origin," in very clear lights. Thus, in the last lines of the Introduction to the "Origin" (4th edition, p. 6) he says—"Furthermore, I am convinced, that Natural Selection has been the main but not exclusive means of modification." Now, though this is a logically true expression of Mr. Darwin's theory, and perfectly intelligible to a naturalist who has closely followed his reasoning, it is almost misleading to those who have not had this advantage. And if to this it be added that an author's last lines, when they formulate his convictions, are those which the ordinary reader carries away most surely and readily, it is not surprising that a very large number of persons have entirely misunderstood both his doctrine and its drift. Everyone knew that Mr. Darwin worked upon variation; and the term variation being often used synonymously with modification, he has been accused of deifying Natural Selection, and of regarding it as a force in obedience to which all plants and animals must vary, and not as a modifier of the results of variation. The apparent issues between Mr. Darwin and many other naturalists hence appeared to the majority of his readers to reside in this: that he attributed those variations from the parentand from one another, which are observable in every family or brood of plants or animals, to Natural Selection,—they to external conditions, as climate, food, &c.; and whilst the latter (whether right or wrong) is intelligible, the former is neither true nor intelligible.

In the present work Mr. Darwin at the outset puts in a proper light the doctrine of the inherent and inextinguishable tendency to vary, in every living being. People may differ as to the extent to which variation will go, but no one disputes that every species varies, and every variety too.

Furthermore, he regards man as himself inoperative as an originator of this inherent tendency, for he says, "It is an error to speak of man as tampering with Nature, and causing variability. If organic beings had not possessed an inherent tendency to vary, man could have done nothing; he unintentionally exposes his animals and plants to various conditions of life, and variability supervenes, which he cannot prevent or check." Beyond this no philosopher can go without entering the region of metaphysics; the next point to ascertain being, whether conditions enforce variation, or whether variation goes on independently of conditions: and as no two conditions ever were or ever will be identical, the question can never be tried on its only issue, and discussion is idle. All we can say is, that, as Mr. Darwin cautiously expresses it, variability "supervenes" on changed conditions. We can often correlate the variation and the condition and we can accelerate the rate of variation and augment its amount, by exaggerating external conditions, but these facts prove nothing; the conditions may have only guided the tendency—directed it, so to speak. True enough, further on in the same paragraph (p. 3), Mr. Darwin says, "The initial variation on which man works, and without which he can do nothing, is caused by slight changes— i. e., the conditions of life." But we question whether he would here wish to be taken "au pied de la lettre," and rather suppose he uses the word "cause" in that conventional sense in which, for all practical purposes, it must be used; for in the next paragraph, and on the same page, he goes on to say, "Although man does not cause variability, and does not prevent it, he can select, preserve, and accumulate the variations given to him by the hand of Nature in any way which he chooses; and thus he can certainly produce great results." In a third passage (p. 6) he says, "Variability… depends in some manner on the action of surrounding circumstances on the organism; and again (p. 9), "Variations… will be governed by the direct action of the surrounding physical conditions, &c." It is difficult to follow this reasoning: if altered conditions cause variability, and man alters a plant's condition, he may fairly be charged with causing variability—just as fairly as a man who so places a sovereign before a thievish boy, as that the boy will certainly steal it. We have alluded to these apparent obscurities not by way of hypercriticism, but to show how difficult a matter it is, to treat of such a subtle subject as the genesis of variation without ambiguity.

From this Mr. Darwin briefly alludes to the conversion of varieties (or incipient species) into species (strongly-marked varieties) by the accumulation and augmentation of slight differences; and then brings Natural Selection on the stage, as the real and ever active agent in determining the degree and direction to which this accumulation and augmentation of slight differences shall proceed, and in eliminating the connecting links, thus leaving the extreme forms as apparently unconnected inter se, as substantive creatures in fact having no family tie or resemblance.

In relation to this subject, the following passage is most important, inasmuch as it explains and fully justifies his speaking conventionally of Natural Selection, as if it were a conscious agent, and for doing which he has been unscrupulously misrepresented, and even audaciously maligned. He says, "The preservation during the battle for life of varieties which possess any advantage in structure, constitution, or instinct, I have called Natural Selection, and Mr. Herbert Spencer has well expressed the same idea as the Survival of the Fittest. The term Natural Selection is in some respects a bad one, as it seems to imply a conscious choice, but this will be disregarded after a little familiarity. No one objects to chemists speaking of 'elective affinity,' and certainly an acid has no more choice in combining with a base, than the conditions of life have in determining whether a new form shall be selected or preserved. The term is in so far a good one as it brings into connection the production of domestic races by man's power of selection, and the natural preservation of varieties and species in a state of nature. For brevity's sake, I sometimes speak of Natural Selection as an intelligent power, in the same way as astronomers speak of the action of gravity as ruling the motions of the planets, or as agriculturists speak of man making races by his power of selection. In one case, as in the other, selection does nothing without variability; and this depends in some manner on the action of the surrounding circumstances on the organism. I have also often personified the word Nature, for I have found it difficult to avoid the ambiguity; but I mean by Nature only the aggregate action and product of many natural laws, and by laws only the ascertained sequence of events."

The subjects of Natural Selection, and the adaptation of new forms to changed conditions will, it is stated in the Introduction, be treated of by Mr. Darwin in another work, already far advanced towards completion, in which also he prepares to show "from experiments and from a multitude of facts, that the greatest amount of life can be supported on each spot by great diversification or divergence in the structure and constitution of its inhabitants," and that the production of new forms, and the conservation of such of them as are best suited to the conditions that environ them, almost inevitably leads to the extermination of the old forms. On this head Mr. Darwin exposes another error into which his opponents have fallen, who, confounding his doctrine with that of Lamarck, suppose him to assert that all variations or modifications are useful and progressive; and that, in fact, progression consists in each separate brood being in its totality an advance on its progenitors. On the contrary, he says that, according to his principles, "there is no innate tendency in each being to its own advancement in the scale of organisation," the fact being that as many or more develop qualities that are disadvantageous as the contrary; but whereas the former perish in consequence, the latter live and transmit their profitable qualities in various degrees to their successors—a process that eventuates in material progress, and in complexity of organisation. And conversely, where the conditions of life are themselves simple, and the simpler forms of life that meet these are simple too, all deviations from the normal or standard will profit their progeny nothing, but, the contrary, and such simple forms would hence remain unchanged for indefinite periods.

Mr. Darwin purposes, after treating of the varieties of organisms in a state of Nature, to discuss the difficulties opposed to his theory of Natural Selection (also we infer in this same second work, though from its triple announcement (pp. 4, 5, and 8), this point is not quite clear), together with the subjects of hybridity, instinct, and the teachings of the geological record.

Lastly, in a third work he proposes to try the principle of Natural Selection, by seeing how far it will explain the facts of hybridity, instinct, geographical and geological distribution, progressive development, &c.; and he gives us a brief but graphic picture of the phases of his own faith, and how these were progressively manifested during his travels, as he successively made those startling geological discoveries, aud sagacious observations, that have lent so great a charm to his Journal, and made him as famous as a traveller, discoverer, and collector, as he now is as an experimenter and thinker. Nor can we conclude this preliminary sketch of his labours better than by the following quotation:—"It is the consideration and explanation of such facts as these, which has convinced me that the theory of descent with modification by means of Natural Selection is in the main true. These facts have as yet received no explanation on the theory of independent creations; they cannot be grouped together under one point of view, but each has to be considered as an ultimate fact. As the first origin of life on this earth, as well as the continued life of each individual, is at present quite beyond the scope of science, I do not wish to lay particular stress on the greater simplicity of the view of a few forms, or of only one form, having been originally created, instead of innumerable miraculous creations having been necessary at innumerable periods; though this more simple view accords well with Maupertius' philosophical axiom of 'least action.' * * * The present action of Natural Selection may seem more or less probable, but I believe in the truth of the theory, because it collects under one point of view, and gives a rational explanation of, many apparently independent classes of facts."