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a naturalist, in his researches, happening to find only a hoof, directly and certainly infers that it was associated with grinding teeth, having flat surfaces, a long alimentary canal, a large stomach, or several; and many other similar characteristics. Yet such conclusions are of a nature strictly inductive. Again, the system of the organs of motion is universally found to be so adjusted, that a variation in the form of one bone is invariably accompanied by variations more or less in all the others. Thus in any new case which may present itself, from a single bone the skilful naturalist will often be able to infer the form of the whole skeleton. On what does the legitimacy of such inferences depend: on what ground of confidence can such reasoning be pursued, but on the assurance of those unfailing principles of analogy which unquestionably pervade the entire range of organized nature, and thus supply the main ground of stability to these inductive conclusions.

That whenever a new plant or animal is discovered, we should never come to any thing anomalous or at variance with systematic order; but that, even in those instances which are apparently the most unlike any previously known, the skilful naturalist should always succeed in assigning to the production in question its precise place in the scale and order of organized beings, and that all fresh discoveries should but fill up blanks in the scheme, is the strongest proof of the existence of some prin

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ciple of the most recondite uniformity throughout all the modifications of organized structures. fact, to elucidate and develope such principles of uniformity and analogy, has been the very object of the labours of the most eminent naturalists; and the best proof of the actual prevalence and admirable unity of those principles is found in the increasing simplicity to which the arrangement of natural classes has been reduced.

Thus the researches of Cuvier reduce the laws of animated existence to only four principal "types," or general schemes of organization, founded on the presence or absence of vertebræ, after which (as he observes,) all animals appear to have been modelled; and of which the subordinate divisions are only comparatively slight modifications, founded on the developement or addition of certain parts, which produce no essential change in the original plan: viz., 1. The Vertebrata, with bony skeletons; 2. The Mollusca, soft, with shells; 3. The Articulata, jointed or ringed; 4. The Radiata, or zoophytes.

Within the limits of each of these four classes, Cuvier traced a precise set of analogies among all their various subdivisions; so that for every member or organ in one species, there was to be found invariably some member or organ in all the others, holding exactly the same place in relation to the general structure and nature of the animal; and thus between the two extreme instances which fall under any one class, though there. might exist the

utmost possible dissimilarity in every respect, yet there was found the closest analogy; in every creature of that class could be pointed out by the skilful comparative anatomist, an exact correspondence in the nature and office of every part relative to the nature of the animal, though bearing not the slightest resemblance. When, however, these great classes themselves were compared together, such analogy seemed to be no further traceable. Each class seemed to include a distinct plan of organization, possessing an unity within itself, but not apparently related to that of the other classes. But these views have been pushed further; another school of physiologists, among whom Geoffrey St Hilaire stands most conspicuous, have contended that even these breaks between the four classes may be filled up, and new principles of analogy developed and traced out, by which these apparently distinct plans of organization may be shown to have a common system of relation; and thus throughout all classes, a principle of still more recondite connexion be perceived.

This principle carried out to its full extent, has been named the "unity of plan or of composition," or the " theory of analogues," and the particular views of structure by which it is upheld, have been designated as the "equilibrization of organs," or other similar names. While, however, the main principle of the reality of some such system of primitive types is universally recognised by naturalists,

yet considerable difference of opinion prevails as to the details of its application, and as to the extent to which it may be followed out. And the question which has thus arisen has occasioned considerable controversy between the partisans of the two rival schools; principally, perhaps, in consequence of its being mixed up with other topics, with which it has at least no necessary connexion; and to which we shall recur in another place. With reference to our present purpose, it will be sufficient to remark simply, that the question between these theories, or rather the question whether the extension given to the great principle of uniformity by the second of them, is true, must be decided merely by physiological evidence: it is purely a question of fact, and must be investigated by careful examination and enlightened comparison of facts and analogies, without any reference to the speculative topics with which it has been mixed up; a distinction which, however plain, seems to have been too much overlooked.

But however this question may be determined, our chief consideration should be to observe, either way, how beautiful an extension of the great principles of natural order and harmonious arrangement is opened to our view. And it is the increasing assurance of this which is continually strengthening the foundation of all our inductive reasonings; of all consistent and profitable search into the laws of the material creation.

Induction in Geology.

WE meet with perhaps the most remarkable instances of the application of the inductive conclusions of comparative anatomy in deciphering the history of fossil remains. The whole subject is, in in fact, only a continued series of such inferences. The entire structure, nature, and habits of animals once inhabiting the earth, are deduced from the occurrence of a few bones, or perhaps a single tooth, or scale, embedded and mineralized in some now solid rock; and yet with the full force of inductive evidence.

It is upon the study of fossil organic remains that the conclusions of geology mainly depend. And in a more general point of view, the researches of this science afford some of the best examples of the vast range of inference to which strict induction may be extended; of conclusions apparently the most remote, the most inconceivable, the most startling; yet all evinced by the same rigidly inductive process by which the most palpable laws of mechanical action are established. The observer finds at various elevations above the sea, beds of shells, and remains of marine animals, buried beneath the soil, or imbedded in the solid rock; he comes most legitimately to the conclusion that these relics were buried when the beds of soil or rock were in the process of formation, in a soft state; when they formed, in fact, the bottom of the waters in which,

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