OCR Text |
Show SPECULATIONS tiN TilE [Ch. XI. 180 . umerous1 y represe nted in a oO 'iven distric. t, has species) once n h ther which did not pre-exist has d b than t at some o cease to e, . g always for reasons before d . pearance-assumm ' rna e Its ap. k 1 of each animal and plant are t t d tl at smgle stoc s on Y . Sa e ' 1 ' · 1' 'd ls of new specieS do not oriO'inally created, and that me IVI ua 0 • many different places at once. ddenly start up m · su So im erfect has the sc.i ence of N a t ura1 History remamed d to Po ur own tu. nes, that within the memory of persons own b f known animals and plants have living the num ers o d now 1, d . quadrupled in many classes. New an been doub e ' OI even ' . . f . _ . are annually dtscovered m parts o ften conspicuous ::.pecies . . . . 0 . 1 · h bited by the most civ1hzed natwns. the old contment, ong 111 a . · • • J! f the limited extent of our mformatwn, Conscious, thetewre, o . . 1 h always m. fer' wh en suel l discoveries are made, t 1at t e we. . . 1 d previously eluded our research ; or had bemgs m question 1a . d . d 1 h . and only miO'rated at a recent per1o at least existe e sew ere, o I . d'ffi lt into the tern.t on.e s wh ere we n ow find t.h em. t 1s 1 cu even m. contemp la tI' on to anticipate the ttme when we shall bhe . 1 d t mal{e any other hypothesis in regard to all t e enut e o f h · marm. e tr1' be s, an d t o by far the greater numb.e r .o t e tenes-f tr.i al·-suc l1 as b'u · ds , which possess such unhmtted powers o mi r~tion . insects which, besides their numbers, are a1 s o so ca gable o/ being diffused to vast distances; and cryptoga~ous lp t to which as to many other classes, both of the ammal P an s' ' . 1' ble d etable kingdom similar observatiOns are app tea . an veg ' bl expect What kind of proof¥, therefore, could we reasona y . . . . 1 . iod of a new species? t find of the ongm at a particu ar per o Perhaps it may be said in reply' that within the l~sthtwlo or druped mw t 1ave three centuries some forest tree or new qua o, 1 d been observed to appear suddenly in those parts. of E.ng ;~. or France which had been most thoroughly mvestlga e h' bl h w that no sue that naturalists might have been a e to s e - . 1 1 b d that t1 1 ere being inhabited any other regwn of t le g o e, an b b-no tradition of anything similar having before een o was . d · ranee. served in the district where It had ma e Its appea 'bl t its Now although this objection may seem plausl e, ye Ch. XI.] APPEARANCE OF NEW SPECIES. 181 force will be found to depend entire] y on the rate of fluctuation which we suppose to prevail in the animate world, and on the proportion which such conspicuous subjects of the animal and vegetable kingdoms bear to those which are less known, and escape our observation. 1'herc are probably more than a million, perhaps two millions of species of plants and animals, exclusive of the microscopic and infusory animalcules, now inhabiting the terraqueous globe. The terrestrial plants, it is supposed, may amount, if fully known, to about one hundred thousand, and the insects to four times that number. 1'o these we have still to add for the remainder of the terrestrial classes, many of the invertebrated and all the vertebrated animals. As to the aquatic tribes, it remains at present in a great degree mere matter of conjecture what proportion they bear to the denizens of the land; but the habitable surface beneath the waters can hardly be estimated at less than double that of the continents and islands, even admitting that a very consider-· able area is destitute of life, in consequence of great depth, cold, darkness, and other circumstances. In the late polar expedition it was found that in some regions, as in Baffin's Bay, there were marine animals inhabiting the bottom at great depths, where the temperature of the water was below the freezing point. That there is life at much greater profundities in warmer regions may be confidently inferred. We have before stated that marine plants not only exist but acquire vivid colours at depths where, to our senses, there would be darkness deep as night. The ocean teems with life-the class of polyps alone are conjectured by Lamarck to be as strong in individuals as insects. Every tropical reef is described as bristling with corals, budding with sponges, and swarming with , crustacea, echini, and testacea; while almost every tide-washed rock is carpeted with fuci and studded with corallines, actinire, and mollusca. There are innumerable forms in the seas of the warmer zones, which have scarcely begun to attract the attention of the naturalist; and there are parasitic animals without |