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We do not know whether Mr. Darwin is related to the well-known author of the "Zoonomia," whose physiological speculations, long since consigned to oblivion, attracted so much attention in the days of our grandfathers. If it be so, he has some hereditary claim to construct theories on the subject of zoological development. But as he has a far larger body of observed phenomena to work upon than were accessible to his predecessor in name and pursuit, so he has also brought to their consideration a less amount of proneness to conjectural and plausible theorizing, a better turn for patient investigation, and a more profound acquisition of scientific knowledge.

Mr. Darwin has to a great extent taken up the same ground which was trodden before by the author of th well-known "Vestiges of Creation." That ingenious though recklessly unphilosophical book has, we strongly suspect, operated not a little to keep back inquiry from the mysterious subject of the propagation of the several forms of life. Our naturalists subdivide tribes into genera, genera into species, species into varieties. But it is impossible to lay down any precise rule whereby to distinguish in all cases the difference between two varieties of the same species from the difference between two species of the same genus. And that being so, how are we entitled to assume, as is commonly done, that the several varieties of the same species are all descended from one common type, while the several species are each descended from a separate type? On this point Mr. Darwin remarks-

In considering the origin of species, it is quite conceivable that a naturalist, reflecting on the mutual affinities of organic beings, on their embryological relations, their geographical distribution, geological succession, and other such facts, might come to the conclusion that each species had not been independently created, but had descended, like varieties, from other species. Nevertheless, such a conclusion, even if well founded, would be unsatisfactory, until it could be shown how the innumerable species inhabiting this world have been modified, so as to acquire that perfection of structure and coadaptation which most justly excites our admiration. Naturalists continually refer to external conditions, such as climate, food, &c, as the only possible cause of variation. In one very limited sense, as we shall hereafter see, this may be true; but it is preposterous to attribute to mere external conditions, the structure, for instance, of the woodpecker, with its feet, tail, beak, and tongue, so admirably adapted to catch insects under the bark of trees. In the case of the misseltoe, which draws its nourishment from certain trees, which has seeds that must be transported by certain birds, and which has flowers with separate sexes absolutely requiring the agency of certain insects to bring pollen from one flower to the other, it is equally preposterous to account for the structure of this parasite, with its relations to several distinct organic beings, by the effects of external conditions, or of habit, or of the volition of the plant itself.

The author of the "Vestiges of Creation" would, I presume, say that, after a certain unknown number of generations, some bird had given birth to a woodpecker, and some plant to the misseltoe, and that these had been produced perfect as we now see them; but this assumption seems to me to be no explanation, for it leaves the case of the coadaptations of organic beings to each other and to their physical conditions of life, untouched and unexplained. It is, therefore, of the highest importance to gain a clear insight into the means of modification and coadaptation.

[Origin, p. 3 Introduction]

In endeavouring to trace out a law on this subject Mr. Darwin has wisely given his especial attention to the phenomena more immediately within out ken, those which are supplied by the domesticated animals. He observes that breeders of any stock produce important variations of type by selecting the animals from which to propagate, and that any peculiarities which they exhibit are, as a general rule, perpetuated and developed by inheritance. Then he argues that if there be any natural forces in operation analogous to the artificial selection made by breeders and fanciers, we may easily conjecture how the several lines of heritable blood would divaricate more and more from each other and from the common ancestor, would develop in an increasing degree the organisation which fits them for any special circumstances, and seek more and more the circumstances for which they are fitted. Thus in a long succession the generations the descendants of a common stock would assume the distinct characteristics of different species, even to that recognised test of difference in species, the infertility of their mutual hybrids. This suggestion has often been thrown out before, but it has never been put forward, we think, in so definite a shape or so philosophical a spirit; nor has it ever received such illustration and support as is supplied to it by Mr. Darwin's ingenuity and scientific knowledge.

The required natural force, analogous to the breeders' selection, Mr. Darwin terms Natural Selection. There is, as he remarks, a constant struggle for existence going on, and that being so, he asks-

Can we doubt (remembering that many more individuals are born than can possibly survive) that individuals having any advantage, however slight, over others, would have the best chance of surviving and of procreating their kind? On the other hand, we may feel sure that any variation in the least degree injurious would be rigidly destroyed.

[Origin, pages 80-81 Chap. IV. Natural selection]

Elsewhere he illustrates the above process in the following fashion:

When we see leaf-eating insects green, and bark-feeders mottled-grey; the alpine ptarmigan white in winter, the red-grouse the colour of heather, and the black-grouse that of peaty earth, we must believe that these tints are of service to these birds and insects in preserving them from danger. Grouse, if not destroyed at some period of their lives, would increase in countless numbers; they are known to suffer largely from birds of prey; and hawks are guided by eyesight to their prey,—so much so, that on parts of the Continent persons are warned not to keep white pigeons, as being the most liable to destruction. Hence I can see no reason to doubt that natural selection might be most effective in giving the proper colour to each kind of grouse, and in keeping that colour, when once acquired, true and constant. Nor ought we to think that the occasional destruction of an animal of any particular colour would produce little effect: we should remember how essential it is in a flock of white sheep to destroy every lamb with the faintest trace of black.

[Origin, pages 84-85 Chap. IV. Natural selection]

Thus Mr. Darwin would suggest that all existing species have spread out from a few common types, and that there may still be a continuity of descent between our modern race of animals and the extinct forms of fossil life; so that the existing elephant mat be "served heir" (as the Scotch lawyers say) to the mammoth of forgotten ages.

Our author frankly states the objections that may be urged against his theory, and he admits that the strongest is to be found in the want of any geological testimony in his favour; for having here the facts of a vast series of ages before us, we might reasonably expects to trace the gradual divergence of a species from its primordial type by the remains of those intermediate forms through which is has passed. He can only meet this objection by urging the imperfect state of the geological record so far as it is yet known to us:- The several difficulties here discussed, namely our not finding in the successive formations infinitely numerous transitional links between the many species which now exist or have existed; the sudden manner in which whole groups of species appear in our European formations; the almost entire absence, as at present known, of fossiliferous formations beneath the Silurian strata, are all undoubtedly of the gravest nature. We see this in the plainest manner by the fact that all the most eminent palæontologists, namely Cuvier, Owen, Agassiz, Barrande, Falconer, E. Forbes, &c., and all our greatest geologists, as Lyell, Murchison, Sedgwick, &c., have unanimously, often vehemently, maintained the immutability of species. But I have reason to believe that one great authority, Sir Charles Lyell, from further reflexion entertains grave doubts on this subject. I feel how rash it is to differ from these great authorities, to whom, with others, we owe all our knowledge. Those who think the natural geological record in any degree perfect, and who do not attach much weight to the facts and arguments of other kinds given in this volume, will undoubtedly at once reject my theory. For my part, following out Lyell's metaphor, I look at the natural geological record, as a history of the world imperfectly kept, and written in a changing dialect; of this history we possess the last volume alone, relating only to two or three countries. Of this volume, only here and there a short chapter has been preserved; and of each page, only here and there a few lines. Each word of the slowly-changing language, in which the history is supposed to be written, being more or less different in the interrupted succession of chapters, may represent the apparently abruptly changed forms of life, entombed in our consecutive, but widely separated formations. On this view, the difficulties above discussed are greatly diminished, or even disappear.

[Origin, pages 310-11 Chap. IX. Geological record]

In connexion with the palaeontological aspect of the question there is another consideration which Mr. Darwin has not noticed, and which may in some sort be taken to militate against his theory. We allude to the fact that the grandest and strongest types of animal life have become extinct, while dwindled specimens of the same group survive among us. If in the days when

A monstrous eft was of old the lord and master of earth, he could not maintain his supremacy and existence, what could have been the more favourable conditions which enabled his scurvy relations of the newt and lizard sort to prosper, in their crawling way, at this present epoch?

One of the most curious chapters in Mr. Darwin's book is that in which he illustrates his theory from the indications of what we might term a yearning on the part of nature for a common pattern on which to construct the several forms of life. Suc are the phenomena of what is termed Morphology:-

What can be more curious than that the hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bat, should all be constructed on the same pattern, and should include the same bones, in the same relative positions?

[Origin, page 434 Chap. XIII. Morphology]

Such indications he also gathers from Embryology, as pointing out the similarity which exists between the embryos of animals which at maturity are widely distinct. Perhaps the most striking illustration of this sort is that drawn from the existence of rudimentary organs, such as the mammæ of males and the undeveloped upper jaw of ruminants.

It is obvious that Mr. Darwin's speculations must jar on the pre-conceived opinions of those who are pleased with such arguments as those advanced in Paley's "Natural Theology." In fact the whole of that ingenious and interesting treatise is superseded if we admit Mr. Darwin's theory. Let it not be supposed, however, that the establishment of this theory (and it can by no means be said to be established yet) is to be regarded as any gain to a Lucretian view of cosmogony. It is surely not less a Divine act of creation, to impress a law upon nature by which she develops herself, than to create the developed forms themselves. All the progress of science leads us from the latter aspect of the Creator to the former. Happily we are not dependent on scientific knowledge for the lesson which tells us of a God. From

The poor Indian, whose untutored mind

Sees God in clouds and hears him in the wind.

to a Humboldt with all the arena of Science before him, Nature teaches all one and the same truth, though she varies the language in which she expressed it.