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the contrary now occupy the place which was once the highest land. He pointed out that some lagoons, as for instance, that of Vanikoro, contain an island in the middle; while other islands, such as Tahiti, are surrounded by a margin of smooth water, separated from the ocean by a coral reef. Now, if we suppose that Tahiti were to sink slowly, it would gradually approximate to the condition of Vanikoro; and if Vanikoro gradually sank, the central island would disappear, while on the contrary the growth of the coral would neutralise the subsidence of the reef, so that we should have simply an atoll, with its lagoon. The same considerations explain the origin of the "barrier reefs," such as that which runs, for nearly one thousand miles, along the north-east coast of Australia. Thus, Mr. Darwin's theory explained the form and the approximate identity of altitude of these coral islands. But it did more than this; because it showed us that there were great areas in process of a subsidence, which, though slow, was of great importance in physical geography.

His monograph of the Cirripedia or barnacles, a curious group of abnormal crustacea, long supposed to belong to the class of molluscs; and even by the older naturalists imagined, probably from their feathery legs, to stand in a mysterious connection with the barnacle-geese, is universally admitted amongst naturalists to be a most masterly work, but is, of course, of a special character. Perhaps the most interesting point is the discovery that certain minute creatures, found adhering to the female barnacles, are really the males. They are, in some species, almost rudimentary, and very short lived, being, indeed, incapable of taking any food. For these little creatures he proposed the term "complemental males."

In the year 1858, Mr. Darwin communicated to the Linnean Society a short, but most important memoir, "On the Variation of Organic Beings in a State of Nature," in which he briefly indicated the views which, under his name, have since become so famous. Mr. Wallace, also, simultaneously and independently arrived at similar results. Mr Darwin's great work "On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life," in which these views were developed with masterly ability, appeared in the following year, and may truly be said to have constituted an epoch in natural history.

The conclusions to which he arrived were as follows: "That the theory of descent with modification embraces all the members of the same class. I believe that animals have descended from at most only four or five progenitors, and plants from an equal or lesser number."

"Therefore, on the principle of natural selection with divergence of character, it does not seem incredible that, from some such low and intermediate form, both animals and plants may have been developed.

And, if we admit this, we must admit that all the organic beings which have ever lived on this earth may have descended from some one primordial form."

"There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed laws of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved."

These views were supported by close reasoning, and an immense array of facts. Mr. Darwin commenced by discussing the variability of animals under domestication and nature, showing the difficulty of distin guishing between varieties and species; and the differences which man had been able to produce in such cases as that, for instance, of our domestic pigeons, all unquestionably descended from a common ancestor. He then referred to the doubtful species, showing that wide ranging, much diffused, and common species vary the most, and that species of the larger genera in each country vary more than those of the smaller. He then called attention to the effect of the struggle for existence, a phrase which has since become an household word, in killing out the individuals less perfectly adapted to their environment, thus exercising in fact a true, though unconscious selection, comparable in its effect to that exercised by man on domesticated animals and plants. He then proceeded to discuss the laws of variation, and to point out, with characteristic candour, the difficulties of his theory. The absence of intermediate varieties between species, he accounted for by the imperfection of the geological record; and he then proceeded to show that the geographical distribution of animals and plants, the fauna and flora, for instance, of oceanic islands, the absence of batrachians and terrestrial mammals, the relation of the inhabitants of islands to those of the nearest mainland, afforded powerful arguments in support of his views. The remarkable facts presented by embryology, and the existence of rudimentary organs, were also shown to point clearly in the same direction.

No one could read this work without admiration, but, although Mr. Darwin's views from the first received the adhesion of some of the most eminent naturalists, they were so much opposed to generally-received opinions, that they naturally aroused much opposition. It is, however, not going too far to say that they have gradually gained ground, not only amongst professed naturalists, but with all those who have taken the trouble carefully to weigh the evidence. Almost all, now, would probably admit that natural selection has greatly influenced the present forms of organised life, though there would still be much difference of opinion as to how far the results have been modified by other causes. Mr. Darwin's views would probably have attracted less opposition had it not been for their obvious bearing on the origin of the human race. Mankind,

indeed, is scarcely mentioned in the "Origin," but Mr. Darwin has dealt with this subject in a subsequent work, the "Descent of Man." In this he has boldly grappled with the question. He points out that man is constructed on the same type or model as other mammals-the bones in his skeleton, as well as his muscles, nerves, blood-vessels, and internal viscera, following the same law. Even his brain, as shown by Huxley and other naturalists, so closely resembles that of the quadrumana, that, as Bischoff, who is a hostile witness, admits, every chief fissure and fold in the brain of man has its analogy in that of the orang, though it is no doubt true that at no period of development do their brains perfectly

agree.

Mr. Darwin points out that, even on minor points, the similarities are very striking; such, for instance, as the arrangement of the hair on the arms. In the case of the orang, this serves to throw off the rain, when, as is the custom of this animal, the arms are bent, with the hands clasped round a branch or over its own head. If the above explanation be correct, the hair on the human forearm assumes an unexpected significance, and offers a curious record of our former state, since, as Mr. Darwin observes, no one supposes that is now of any use in throwing off the rain, nor, in our present erect condition, is it properly directed for this purpose. Again, in every large collection of human skulls some may be found with the canine teeth projecting beyond the others, in the same manner as, though to a less degree than, in the anthropomorphous apes. "He," urges Mr. Darwin, "who regards with scorn the belief that the shape of his own canines, and their occasional great development in other men, are due to our early progenitors having been provided with those formidable weapons, will probably reveal by sneering the line of his descent. For though he no longer intends, nor has the power, to use these teeth as weapons, he will unconsciously retract his snarling muscle' (thus named by Sir C. Bell) so as to expose them ready for action, like a dog prepared to fight."

The main result at which Mr. Darwin arrives is that man is descended from some more lowly form, though he warns his readers not to suppose that our early progenitors were identical with, or even closely resembled, any existing ape or monkey. Such conclusions are, no doubt, highly distasteful to many minds, but, as Mr. Darwin points out, "we are not here concerned with hopes or fears, but only with the truth as far as our reason allows us to discover it. I have given," he adds, "the evidence to the best of my ability:" and, whatever the ultimate verdict may be, no one will deny that he has treated this question with the greatest ability, and most laudable candour.

In the "Origin of Species," Mr. Darwin derived a strong argument from the changes which had been produced by man in domesticated animals and plants. For if considerable modifications had been thus

produced during a comparatively short period, it was the less improbable that still greater alterations might have been produced by natural causes, acting through the far longer periods of geological time. In the year 1868, he published a special work on the "Variation of Animals and Plants under Domestication." In it he gave, under the head of each species, the facts which he had been able to collect, showing the amount and nature of the changes which animals and plants had undergone whilst under the dominion of man.

At the conclusion of the work Mr. Darwin set forth his " provisional hypothesis," as he calls it, of Pan-Genesis, namely, that "the whole organisation, in the sense of every separate atom or unit, reproduces itself. Hence ovules, or pollen grains, the fertilised seed or egg, as well as buds, include and consist of a multitude of gemmules thrown off from each separate atom of the organism." It is universally admitted that cells propagate themselves by self-division, and Mr. Darwin assumes that, besides this means of increase, they throw off minute gemms or atoms, which circulate freely throughout the system, and multiply by selfdivision, subsequently becoming developed into cells like those from which they were derived. He supposes that these gemmules are transmitted from the parents to their offspring, and are generally developed in the succeeding generation; but are sometimes transmitted in a dormant state during many generations.

At the close of the last century, Sprengel, a German naturalist, published a most suggestive work on flowers, in which he pointed out the curious relations existing between these and insects, and showed that the latter carry the pollen from flower to flower. Sprengel's observations, however, attracted little notice, until Mr. Darwin called attention to the subject.

The first of Mr. Darwin's important contributions to Botanical Science was his "Memoir on the Genus Primula," published in the Linnean Journal for 1862. It had long been known, not only to botanists, but even to village children, that the cowslip and primrose exist under two forms, about equally numerous, and differing from one another in the arrangement of their stamens and pistils; the one form having the stamens at the summit of the flower, and the stigma half-way down; while in the other the relative positions are reversed, the stigma being at the summit of the tube, and the stamens half-way down. This difference had, however, been regarded as a case of mere variability; but Mr. Darwin showed it to be a beautiful provision, by means of which insects unconsciously fertilise each flower with pollen brought from a different plant.

These two forms of Primula differ not only in the above points, but in several others, and especially in the form and size of the pollen-grains. By a series of most careful and elaborate observations and experiments,

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