446 OPERATIONS SUBSIDIARY TO INDUCTION. 



than one ; and because those may be correctly termed properties of a 

 class, which a thing- exhibits exactly in proportion as it belongs to the 

 class, that is, in proportion as it possesses the main attributes con- 

 stitutive of the class. 



§ 4. It remains to consider how the internal distribution of the series 

 may most properly take place : in what manner it should be divided 

 into Orders, Families, and Genera. 



The main principle of division must of course be natural affinity ; 

 the classes formed must be natural groups : and the formation of these 

 has already been sufficiently treated of. But the principles of natural 

 gi-ouping must be applied, in subordination to the principle of a natural 

 series. The groups must not be so constituted as to place in the same 

 gi-oup things which ought to occupy different points of the general 

 scale. The precaution necessary to be observed for this purpose is, 

 that the frimary divisions must be grounded not upon all distinctions 

 indiscriminately, but upon those which correspond to variations in the 

 degree of the main phenomenon. The series of Anirriated Nature 

 should be broken into parts at the exact points where the variation in 

 the degree of intensity of the main phenomenon (as marked by its 

 principal characters. Sensation, Thought, Voluntary Motion, &c.) be- 

 gins to be attended by conspicuous changes in the miscellaneous prop- 

 erties of the animal. Such well marked changes take place, for 

 example, where the class Mammalia ends ; at the points where Fishes 

 are separated from Insects, Insects from Mollusca, &c. Wlien so 

 formed, the primary natural groups vnll compose the series by mere 

 juxtaposition, without redistribution ; each of them corresponding to 

 a definite division of the scale. In like manner each family should, if 

 possible, be so subdivided, that one portion of it shall stand higher and 

 the other lower, though of course contiguous, in the general scale ; 

 and only when this is impossible is it allowable to ground the remain- 

 ing subdivisions upon characters having no determinable connexion 

 with the main phenomenon. 



Where the principal phenomenon so far transcends in importance all 

 other properties on which a classification could be grounded, as it does 

 in the case of animated existence, any considerable deviation from the 

 rule last laid down is in general sufliciently guarded against by the first 

 principle of a natural arrangement, that of foi-ming the groups ac- 

 cording to the most important characters. All attempts at a scientific 

 classification of animals, since first their anatomy and physiology were 

 successfully studied, have been fi-amcd with a certain degree of in- 

 stinctive reference to a natural series, and have accorded, in many 

 more points than they have differed, with the classification which 

 would most naturally have been grounded upon such a series. But 

 the accordance has not always been complete, and it still is often a 

 matter of discussion which of several classifications best accords with 

 the true scale of intensity of the main phenomenon. M. Comte, for 

 example, blames Cuvier for having formed his natural groups with an 

 undue degree of reference to the mode of alimentation, a circumstance 

 directly connected only with organic life, and leading to an ari^mge- 

 ment most inappropriate for the pui-poses of an investiga:tion of the 

 laws of animal life, since both carnivorous and herbivorous or frugivo- 

 rous animals are found ' at almost every degree in the scale of animal 



