372 THE ORIGIN OF SPECIES 



ported by observing the great diversity of forms, which, in any 

 small area, come into the closest competition, and by certain 

 facts in naturalization. 



I attempted also to show that there is a steady tendency in 

 the forms which are increasing in number and diverging in char- 

 acter, to supplant and exterminate the preceding, less divergent, 

 and less improved forms. I request the reader to turn to the 

 diagram illustrating the action, as formerly explained, of these 

 several principles; and he will see that the inevitable result is, 

 that the modified descendants proceeding from one progenitor 

 become broken up into groups subordinate to groups. In the 

 diagram each letter on the uppermost line may represent a genus 

 including several species; and the whole of the genera along this 

 upper line form together one class, for all are descended from 

 one ancient parent, and, consequently, have inherited something 

 in common. But the three genera on the left hand have, on this 

 same principle, much in common, and form a sub-family distinct 

 from that containing the next two genera on the right hand, which 

 diverged from a common parent at the fifth stage of descent. 

 These five genera have also much in common, though less than 

 when grouped in sub-families; and they form a family distinct 

 from that containing the three genera still farther to the right 

 hand, which diverged at an earlier period. And all these genera, 

 descended from (A), form an order distinct from the genera 

 descended from (I). So that we here have many species descended 

 from a single progenitor, grouped into genera; and the genera 

 into sub-families, families, and orders, all under one great class. 

 The grand fact of the natural subordination of organic beings 

 in groups under groups, which, from its familiarity, does not al- 

 ways sufficiently strike us, is in my judgment thus explained. No 

 doubt organic beings, like all other objects, can be classed in many 

 ways, either artificially by single characters, or more naturally 

 by a number of characters. We know, for instance, that minerals 

 and the elemental substances can be thus arranged. In this case 

 there is of course no relation to genealogical succession, and no 

 cause can at present be assigned for their falling into groups. 

 But with organic beings the case is different, and the view above 

 given accords with their natural arrangement in group under 

 group; and no other explanation has ever been attempted. 



Naturalists, as we have seen, try to arrange the species, genera, 

 and families in each class, on what is called the Natural System. 

 But what is meant by this system? Some authors look at it merely 

 as a scheme for arranging together those living objects which are 



