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Show ~0 PERMANENCE OF TilE SPECIFIC CHARACTJm, [Ch. II. which the fruitful progeny has sprung, were ~ere varieti:s. If he pre1r er t h e 1a tt er., he 1• s compelled to qu. estwn. the .r eahty f 1 d. . t f all other supposed species w luch d1ffer no 0 t 1e 1stmc ness o more t I1 an t l1 e paren t s of Such Prolific hybrids ; for. although he may not be enabled immediately t~ procure, m all sue~ m• s t ances, a f ru1 'tful off:spr'1n0o' ' yet expenme. nts show,. that after repeated failures the union of two recogm~ed ~pec1es may .at last, under very favourable circumstances, g1ve h1rth to~ fertile progeny. Such circumstances, therefo~e, ~he naturahst may conceive to have occurred again and agam, m the course of a great lapse of ages. His first opinions are now fairly unsettled, and every stay at which he has caught has given way one after another; he is in danger of falling into any new and visionary doctrine which may be presented to him; for he now regards every part of the animate creation as void of stability, and in a state of continual flux. In this mood he encounters the Geologist, who relates to him how there have been endless vicissitudes in the shape and structure of organic beings in former ages-how the approach to the present system of things has been gra~ua~that there bas been a progressive development of orgamzatwn subservient to the purposes of life, from the most simple to the most complex state-that the appearance of man is the last phenomenon in a long succession of events-a~d, final~y, that.a series of physical revolutions can be traced m the morgamc world, coeval and coextensive with those of organic nature. These views seem immediately to confirm all his precon· ceived doubts as to the stability of the specific character, and he thinks he can discern an inseparable connexion between a series of changes in the inanimate world, and the capability of species to be indefinitely modified by the i~fluence of external circum· stances. Henceforth his speculations know no definite bounds i he gives the rein to conjecture, and fancies that the outward form, internal structure, instinctive faculties, nay, that reason itself, may have been gradually developed from some of the simplest states of_ existence,-that all animals, that man him· Cb. II.] PERMANENcg OF THE SPECIFIC CHARACrEn, ~1 self, and the irrational beings, may have had one common origin ; that all may be parts of one continuous and progressive scheme of development from the most imperfect to the more complex: ; in fine, he renounces his belief in the high genealogy of his species, and looks forward, as if in compensation, to the future perfectibility of man in his physical, intellectual, and moral attributes. Let us now proceed to consider what is defective in evidence, and what fallacious in reasoning, in the grounds of these strange conclusions. Blumenbach judiciously observes, "that no general rule can be laid down for determining the distinctness of species, as there is no particular class of characters which can serve as a criterion. In 'each case we must be guided by analogy and probability." The multitude, in fact, and complexity of the proofs to be weighed, is so great, that we can only hope to obtain presumptive evidence, and we must, therefore, be the more careful to derive our general views as much as possible from those observations where the chances of deception are least. We must be on our guard not to tread in the footsteps of the naturalists of the middle ages, who believed the doctrine of spontaneous generation to be applicable to all those parts of the animal and vegetable kingdoms which they least understood, in direct contradiction to the analogy of all the parts best known to them ; and who, when at length they found that insects and cryptogamous plants were also propagated from eggs and seeds, still persisted in retaining their old prejudices respecting the infusory animalcules and other minute beings, the generation of which had not then been demonstrated by the microscope to be governed by the same laws. Lamarck has indeed attempted to raise an argument in favour of his system, out of the very confusion which has arisen in the study of some orders of animals an~l plants, in consequence of the slight shades of difference which separate the new species discovered within the last half century. That the embarrassment of those who attempt to classify and distinguish the new |