. 225. THEORY OF THE SYSTEM. 331 



Iron-pyrites, than to rhombohedral Lime-haloide. The 

 latter species again is more similar to the rest of the Lime- 

 haloides, than to prismatic Feld-spar, or to rhombohedral 

 Corundum, &c. 



This relation of similarity is not unavoidably necessary. 

 One of the species, for instance, might present the same de- 

 gree of resemblance to every one of the others, and vice 

 versa , so that among these species there could not be per- 

 ceived even the consecutive order of series. As there really 

 exist several species, among which this is the case, the same 

 might occur among all. This would not limit the variety 

 of nature, although that variety would then appear under 

 a different form. 



On the other hand, the relation of similarity might be 

 found different in every particular case; so that if we 

 would suppose a certain species to bear a certain degree of 

 resemblance to another, a second one could not be found, 

 among which and the first, the same degree of resem- 

 blance would prevail. The consequence of this would be 

 the impossibility of producing any other arrangement among 

 the species than that of a series, in which they would fol- 

 low each other according to their different degrees of re- 

 semblance. 



A single glance at the species of the Mineral Kingdom, 

 and at the above examples, will suffice to shew, that nei- 

 ther of these two suppositions takes place in nature. There 

 exist different degrees of resemblance, by which a series 

 may be produced, but not a series of the single species. 



The different degrees of resemblance'lay the foundation 

 for the higher ideas of the Theory of the System ; that 

 is to say, for the ideas of classification. 



. 225. GENUS. 



An assemblage of species, connected by the high- 

 est degree of natural-historical resemblance, is 

 termed a Genus. 



