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Show DISPERSION OF ANIMALS BY MAN. [Ch. VII. The great viper, fer de lance, a species no ~e~s venomous than the rattle-snake, which now ravages Martlmq~e an.d St. Lucia, was accidentally introduced by man, and exists m no other part of the West Indies. Many parasitic insects, which attack our pers?ns, and some of which are supposed to be peculiar to our species, have been carried into all parts of the earth, and have as high a claim as man to an universal geographical distribution. A great variety of insects have ~een .transported i~ ships from one country to another, especially m warmer latitudes. Notwithstanding the coldness of our climate, we have been unable to prevent the cockroach (Blatta orientalis ), from entering and diffusing itself in our ovens and kneading troughs, and availing itself of the artificial warmth which we afford. It is well known also that beetles, and many other kinds of ligniperdous insects, have been introduced into Great Britain in timber; especially several North American species. " The commercial relations," says Malte·Brun *, " between France and India, have transported from the latter country the aphis, which destroys the apple-tree, and two sorts of Neuroptera, the lucifuga and jlavicola, mostly confined to Provence and the neighbourhood of Bordeaux, where they devour the timber in the houses and naval arsenals." Among molluscs we may mention the teredo navalis, which is a native of equatorial seas, but which, by adhering to the bottom of ships, was transported to Holland, where it has been most destructive to vessels and piles. The same species has also become naturalized in England, and other countries en· joying an extensive commerce. In all these and innumerable other instances, we may regard the involuntary agency of man as strictly an~logous to t~at of the inferior animals. Like them we unconsciously contnbute to extend or limit the geographical range and numbers of certain species, in obedience to general rules in the economy of nature, which are for the most part beyond our control. "' Syst. of Geog., vol. viii., p. 169. CHAPTER VIII. Theori.es resp~cting. the original introduction of species-Proposal of an hypothesis on th1s subJect-Supposed centres or foci of creation-Why the distinct provinces of animals and plants have not become more blended togetherBrocchi's speculations on the loss of speciell-Stations of plants and animals -Complication of causes on which they depend-Stations of plants how affect~d by animals-Equilibrium in the number of species, how prese~edPecuhar efficacy of insects in this task-Rallidity with which certain insects multiply~ ~r .decrease in numbers-Effect of omnivorous animals in preserving the eqmhbrmm of species-Reciprocal influence of aquatic and terrestrial ' species on each other. IT. would be superfluous to examine the various attempts whiCh were made to explain the phenomena of the distribu~ ion of species alluded to in the preceding chapters, in the Infancy of the sciences of botany, zoology, and physical geography. The theories or rather conjectures then indulged, now stand refuted by a simple statement of facts; and if Linnreus were living, he would be the first to renounce the notions which he promulgated. For he imagined the habitable world to have been for a certain time limited to one small tract the only por.tion of the earth's surface that was as yet laid ba;e by the subsidence ~f. the primreval ocean. In this fertile spot he supposed the or1gtnals of all the species of plants which exist on this globe to have been congregated, together with the first ance~tors ~fall. anim~ls and of the human race. " In qua. com. ~od: habitavermt ammalia omnia, et vegetabilia lrete germinave. rmt. In order to accommodate the various habitudes of so ma?y creatures, and to provide a diversity of climate suited to their several natures, the tract in which the creation took place was supposed to have been situated in some warm region of the .earth, but to have contained a lofty mountain range, on the heights and in the declivities of which were to be found * |
