. 221. THEORY OF THE SYSTEM. 325 



derations. It would be contrary to the principles of Na- 

 tural History, to determine the idea of the species ac- 

 cording to single properties, of whatever kind these may 

 be. An idea thus determined is not scientific, and cannot 

 be but incomplete. It will never be found sufficient in its 

 application, and thus open the way to the introduction of 

 other considerations, foreign to Natural History, in pro- 

 ducing the idea of the species. This has been the source 

 of the contamination which the science has suffered through 

 the introduction of heterogeneous principles, the disagree- 

 able consequences of which have long ago been sufficiently 

 conspicuous. Moreover, the determination, according to 

 single characters, will unavoidably introduce a distinction 

 among essential and accidental properties, which cannot be 

 allowed to take place, either in developing the idea of 

 the species, or in considering the identity of individuals 

 (.215.). 



The species itself is the proper object of classification, or 

 the thing which is to be classified. The idea of the spe- 

 cies, therefore, cannot be produced by the classification, 

 as some naturalists seem to believe, who begin and termi- 

 nate their classification, without previously having pro- 

 duced the idea of the species. This idea is constant every- 

 where, in all sciences, concerning the productions of the 

 Mineral Kingdom ; and it must be the foundation of every 

 system, whatever may be the principles followed in its 

 construction. The correct determination of the natural- 

 historical species thus appears to be of the greatest mo- 

 ment in the Mineral Kingdom. 



. 221. TRANSITIONS. 



The progress of the gradations in the properties 

 of homogeneous individuals is termed a Transition 

 or Passage ; and we say of individuals, in which 

 such a progress may be demonstrated, that they pass 

 into each other. 



