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Show 1~8 DROCClii ON TilE LOSS OF SPECIES. (Ch. vnr. place since species identical with those now in being were created. . T h ese, an d many km. dt·ed topics ' cannot be fully discuss.e d unt1. 1 we h ave cons1' d ere d , not merely the general laws wh1. ch may regulate the first introduction of species, bu~ those whiCh may 11. m1. t t 11 e1. r d U?'a tw' n on the earth • Brocch1, whose un- ti.m e1 y d eat h m. E~ gyp t 1· s deplored by all who have the. progress of geo 1o gy a t heart ' has remarked, when hazardm· g , sohm e interestinO' conjectures respecting " the loss of species, t at a modern onaturalist bad no small assurance, who declared" t~at individuals alone were capable of destruction, and that spectes were so perpe t ua ted t.h at nature could not annihilate them, so 1o nO' as t h e p 1a ne t 1a s ted ~ or at least that nothing less than the sho~k of a comet, or some similar disaster, could put an end to t l1 e1· r ex1· s t ence * ." 'I'he Italian oO 'eologist, on the contrary, had satisfied himself, that many species of testacea, which formerly inhabited the Mediterranean, bad become extinct, altho~gh a great numb er o f others , which bad been the contemp. o.r aries of t h ose 1o st races, st I' ll surv1'ved · He came to the opmwn, that about half the species which peopled the waters w~en the Sub-apennine strata were deposited, had gone out of existence; and in this inference he does not appear to have been far wrong. But instead of seeking a solution of this problem, like some other geologists of his time, in a violent and general catastrophe, Brocchi endeavoured to imagine some regular and constant law by which species might be made to disappear from the earth gradually and in succession. The death, he suggest~d, of a species might L.epend, like that of individuals, on c~rta:n peculiarities of constitution conferred upon them at their birt.h, ~nd as the longevity of the one depends on a certain force of vitah~y, which after a period, grows weaker and weaker, so the duratiOn of the ' other may be governed by the quanti· ty of prol '1f i c power bestowed upon the species, which,' after a_ s.ea~on,. rna~ decline in energy, so that the fecundity and muluphcatwn o * N ecker 21 Brocchi, Conch. Foss. Subap., tome 1 Phytozool. Philosoph., P· • i., p. 229. Ch. VIII.] BROCCIII ON Tim LOSS OF SPECIES, individuals may be graduaJJy lessened from century to century, "until that fatal term arrives, when the embryo, incapable of extending and developing itself, abandons, almost at the instant of its formation, the slender principle of life by which it wa~ scarcely animated,-and so all dies with it." Now we might coincide in opinion with the Italian naturalist, as to the gradual extinction of species one after another, by the operation of regular and constant causes, without admitting an inhet·ent principle of deterioration in their physiological attributes. We might concede " that many species are on the decline, and that the day is not far distant when they will cease to exist;" yet deem it consistent with what we know of the nature of organic beings, to believe that the last individuals of each species retain their prolific powers in their fuJl intensity. Brocchi has himself speculated on the share which a change of climate may have had in rendering the Mediterranean unfit for the habitation of certain testacea, which still continued to thrive in the Indian ocean, and of others which were now only represented by analogous forms within the tropics. l-Ie must also have been aware that other extrinsic causes, such as the progress of human population, or the increase of some one of the inferior animals, might gradualJy lead to the extirpation of a particular species, although its fecundity might remain to the last unimpaired. If, therefore, amid the vicissitudes of the animate and inanimate world, there are known causes capable of bringing about the decline and extirpation of species, it became him thoroughly to investigate the full extent to which these might operate, before he speculated on any cause of so purely hypothetical a kind, as "the diminution of the proline virtue." . If ~t could have been shown that some wild plant had msens1bly dwindled away and died out, as sometimes happens to cultivated ~arieties propagated by cuttinO's even thouO'h 1' 0 ' b c tmate, soil, and every other circumstance should continue ident.ically the same-if any animal had perished while the physical condition of the earth, and the numbe1.· and force of VoL. II, K |