CLASSIFICATION BY SERIES. 445 



mere modifications of the one phenomenon sought; effects (Iclermiiicd 

 by the cooperation ot" some iiicideutal circumstance with the hiws of 

 that phenomenon. Thus in the case of animated beings, the dilferences 

 between one class of animals and another may reasonably be con- 

 sidered as mere modifications of the general phenomenon, animal life; 

 modifications arising cither from the diflercnt degrees in which that 

 phenomenon is manifested in different animals, or fi-om the intermix- 

 ture of the effects of incidental causes peculiar to the nature of each, 

 with the effects produced by the gcnel-al laws of life ; those laws still 

 exercising a predominant inlluence over the result. Such being the 

 case, no other inductive incjuiry respecting animals can bo successfully 

 canied on, except in subordination to the gi'eat inquiry into the uni- 

 versal laws of animal life. And the classification of animals best 

 suited to that one purpose, is the most suitable to all the other pur- 

 poses of zoological science. 



§ 3. To establish a classification of this sort, or even to comprehend 

 it when established, requires the power of recognizing the essential 

 similarity of a phenomenon, in its minuter degrees and obscurer forms, 

 with what is called the sa7nc phenomenon in the greatest perfection ot 

 its development ; that is, of identifying with each other all phenomena 

 which difier only in degree, and in projierties which we suppose to be 

 caused by difference of degree. In order to recognize this identity, 

 or in other words, this exact similarity of quality, the assumption of a 

 type-species is indispensable. We must consider as the type of the 

 class, that among the Kinds included in it, which exhibits the projierties 

 constitutive of the class, in the highest degree ; conceiving the other 

 varieties as instances of degeneracy, as it were, fi-om that type; devia- 

 tions from it by inferior intensity of the characteristic ])roperty or 

 properties. For every phenomenon is best studied [cceteris j^aribus) 

 where it exists in the greatest intensity. It is there that the effects 

 which either depend upon it, or depend upon the same causes with it, 

 will also exist in the greatest degree. It is there, consequently, and 

 only there, that those effects of it, or joint effects with it, can become 

 fully known to us ; so that we may learn to recognize their smaller 

 degrees, or even their mere rudimtnits, iir cases in which the direct 

 study would have been difficult or even impossible. Not to mention 

 that the phenomenon in its higher degrees may be attended by effects 

 or collateral circumstances which in its smaller degrees do not occur at 

 all, requidng for their production in any sensible amoimt a greater 

 degree of intensity of the cause than is there met with. In man, for 

 example (the species in which both the phenomenon of animal and that 

 of organic life exist in the highest degree), many subordinate phe- 

 nomena develop themselves in the course of his animated existence, 

 which the inferior varieties of animals do not show. The knowledge 

 of these properties may nevertheless be of great avail towards the 

 discovery of the conditions and laws of the general phenomenon oi' life, 

 which is common to man with those inferior animals. And they are, 

 even, rightly considered as properties of animated nature itself; 

 because they may evidently be afiiliated to the general laws of ani- 

 mated nature ; because we may fairly presume that some rudiments 

 or feeble degrees of those properties would be recognized in all 

 animals by more perfect organs, or even by more perfect instruments, 



