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Show 1~6 SUPPOSED CENTRES, OR FOCI, [Cb. VIII. the Amazon and the Orinoco, ever arrive at the shores of the Pacific. . In the ocean an analogous state of things would p~ev~Il ;. :or there, also, climate would exert a great influence m .hm1~mg the range of species, and the land would stop the m~gratt~ns of aquatic tribes as effectually as the sea arrests the dispersiOn of the terrestrial. As certain birds, insects, and the seeds of plants, can never cross the direction o~ pre:ail~ng winds, so currents form natural barriers to the d1ssemmat10n of many oceanic races. A line of shoals may be as impassable to pelagian species, as are the Alps and the Andes to plants a~d animals peculiar to plains, while deep ab!sses .may prove msuperable obstacles to the migrations of the mhab1tants of shallow waters. It is worthy of observation, that one effect of the introduction of single pairs of each species must be the confined r~nge of certain groups in spots which, like small islands, or sohtary inland lakes, have few means of interchanging their inhabitants with adjoining regions. Now this congregating, in a small space, of many peculiar species, would give an appear~nce of centres or foci of creation, as they have. been termed, as 1fthe~e were favourite points where the creative energy has been .m greater action than in others, and where the numbers of pecuhar organic beings have consequently become more considerable. We do not mean to call in question the soundness of the inferences of some botanists, as to the former existence of certain limited spots whence species of plants have been propagated, radiating, as it were, in all directions from a common centre. On the contrary, we conceive these phenomena to be the necessary consequences of the plan of nature before suggested, operating during the successive mutations of the surface, some of which the geologist can prove to have taken .pl~ce subsequently to the period when many species now extstmg were created. In order to exemplify how this arrangement of plants may have been produced, let us imagine that: about three centuries before the discovery of St. Helena (Itself of submarine volcanic origin), a multitude of new isles had been Ch. VIII.] OF CREATION. 1~7 thrown up in the surrounding sea, and that these had each become clothed with plants emigrating from St. Helena, in the same manner as the wild plants of Campania l1ave diffused themselves over Monte Nuovo. Whenever the £rst bot:~ist investiga~ed the new archipelago, he would_, in all probability, find a d1fferent assemblage of plants in each of the isles of recent formation; but in St. Helena itself, he would meet with individuals of every species belonging to all parts of the archipelago, and some, in addition, peculiar to itself, viz., those which had not been able to obtain a passage into any one of the surrounding new-formed lands. In this case, it micrht be truly said that the original isle was the primitive focus; or centre, of a certain type of vegetation, whereas, in the surrounding ~sles, there would be a smaller number of species, yet all belongmg to the same group. But this peculiar distribution of plants would not warrant the conclusion that, in the space occupied by St. Helena, there had been a greater exertion of creative power than in the spaces of equal area occupied by the new adjacent lands, because within ~he period in which St. Helena had acquired its peculia; vegetat~on, each of the spots supposed to be subsequently converted mto land, may have been the birth-places of a great ~umber of marine animals and plants_, which may have had tlme to scatter themselves far and wide over the southern Atlantic. ~erhaps it may be objected to some part of the foregoing trat~ of reasoning, that during the lapse of past ages, especially durmg many ~artial revoluti~ns of the globe of comparatively modern date, different zoologiCal and botanical provinces oucrht to ha;e ~eco~e m.ore confounded and blended together-that the distnbutwn of species approaches too nearly to what miaht ~ave been expected, if animals and plants had been introdu~ed mto the globe when its physical geography had already assumed the features which it now wears ; whereas we know that in certain districts, considerable geographical changes have taken |