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originate usually in the great gardens of the florist or of the market-gardener, who cultivates, it may be, many acres of one species. It is easy to understand, with this explanation in view, how sometimes the present fauna or flora of an island should resemble that of large portions of the earth during some one of the earlier geological ages. This is actually the case with the flora of Madeira 1 and (as will be seen in a succeeding chapter) with the fauna of Madagascar. What, then, should we expect to find occurring when the animals and plants of an oceanic island like St. Helena are suddenly brought into competition with those of a continent? In this case of St. Helena, the question has been experimentally answered; and the result of the introduction of European animals and plants, whether by accident or design, has been almost to supplant the native species. So, too, the animals and plants of Europe drive out the native productions of New Zealand, and, in some degree, those of Australia : for, although Australia is properly to be ranked as a continent, the long period that has elapsed since it has been connected with any mainland has left its fauna and flora in a very backward or antiquated condition. In both Australia and New Zealand the English rabbit has multiplied in such a way as seriously to threaten the success of the farmers. The native carnivorous animals seem unable to keep down the intruders. Of the seriousness of the situation in New South Wales the “ Illustrated Sydney News "says,

1 Darwin, Origin of Species, p. 83.

“ The keeping of rabbits of any kind is now prohibited by law, there being a penalty of a hundred pounds for every offence proved. This may seem severe; but it is stated that the rabbit-pest can be traced in a large measure to a few rodents which were thoughtlessly let loose. It is marvellous how rapidly their numbers become multiplied in the pastoral districts, in several of which they have completely eaten out the sheep. In reference to the ravages of these unwelcome animals, Mr. Maxwell of Cobar says, “Once rabbits get on a run, it is a constant outlay. In a small paddock of forty acres I have seen three men constantly killing four and five dozen per day for months together, and still they kept coming. That was twelve years ago. They tried killing for several years. Before rabbits came, we used to have seventy to eighty per cent of lambs, and ran three sheep to four acres. In less than three years we could not rear a lamb; and it took four acres to keep one sheep alive; and all our cattle died.

Then we fenced with paling, and kept them out of the run, and kept killing; that is, trapping, shooting, hunting with dogs and ferrets, and poisoning. The brutes kept coming most of the time into the little paddock, as it was the sweetest feed. There are still rabbits on the place, and men have to be kept to keep them down.' At first Victoria was the principal sufferer; but somehow or other the rabbits have crossed the Murray, spreading devastation and panic throughout the southwestern portions of the colony, and ruining the prospects of numbers of hardy settlers. How far the Rabbit Nuisance Act will aid in abating the evil remains to be seen; but, if it fails, the situation will be one of the gravest character."

Of the remedies suggested for the difficulty, the ones that seem most likely to do away

with the evil are the importation of polecats from Europe, or of mongooses (little carnivorous animals, often called ichneumons) from Asia, to kill off the rabbits. Of New Zealand, “ Dr. Hooker states that the cow-grass has taken possession of the roadsides; dock and water-cress choke the rivers; the sow-thistle is spread all over the country, growing luxuriantly up to six thousand feet; white clover in the mountain districts displaces the native grasses; and the native (Maori) saying is, “As the white man's rat has driven away the native rat, as the European fly drives away our own, and the clover kills our fern, so will the Maories disappear before the white man himself.'” 1 And what

1 Professor E. L. Youmans, article “Darwinism,” in Johnson's Cyclopædia.

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is so forcibly here stated in regard to New Zealand is more or less true of every island far from any mainland.

On the other hand, what would be the result of exposing a great continent like EuropeAsia (the largest land-mass in the world) to invasions by animals or plants from islands or small continents? Here, again, experiment has answered the question; and it is found, that, as Darwin says, “ hardly a single inhabitant of the southern hemisphere has become wild in any part of Europe.

I have spoken in a preceding chapter of the great differences in the varieties of domestic dogs and cats, and of the differences between these and wild species. Now, when dogs or cats are allowed to run wild, they do not become identical with any existing wild species; and this same fact is noticed in regard to most domesticated animals when turned loose to shift for themselves. From this it seems most reasonable to conclude that our domestic animals are substantially new species, produced by the long-continued action of human selection and of changed conditions of life on the descendants of the original wild stock. The same failure to return to a state resembling any known wild species is noticed in the case of some cultivated plants which have run wild. But if we find that changes so great as to create new species have occurred among domesticated animals and cultivated plants as the result of man's selection, acting only through some thousands of years; and if these new species are at times so permanent as to seem indestructible by natural agencies, — what may not the selective action of Nature through unknown ages have accomplished ? May not Nature, acting in the manner already described for perhaps more than fifty millions of years, have been able to produce from a few forms of life, or even from one form, all the long series of living and extinct species? But it is not alone to the agency of natural selection, powerful as that certainly has been in perpetuating new forms, and taking advantage of every beneficial variation, that the whole work of establishing and protecting new species is to be ascribed.

1 It must be remembered that the southern liemisphere consists of relatively small and narrow portions of land, and that these have at times been quite cut off from the northern hemisphere.

Among the higher animals, a process to which Mr. Darwin has given the name of “sexual se

1 Dana's Manual of Geology, p 591.

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