CLASSIFICATION. 409 



qiiently the groups -which are now large, and which gen- 

 erally include many dominant species, tend to go on in- 

 creasing in size. I further attempted to show that from 

 the varying descendants of each species trying to occupy 

 as many and as different places as possible in the economy 

 of nature, they constantly tend to diverge in character. 

 This latter conclusion is supported 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 character, 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 descend- 

 ants proceeding from one progenitor become broken up into 

 groups subordinate to grouj)s. 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 subfamily, distinct from that containing the next 

 two genera on the right hand, which diverged from a com- 

 mon parent at the fifth stage of descent. These five genera 

 have also much in common, though less than when grouped 

 in subfamilies; and they form a family distinct from that 

 containing the three genera still further 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 subfamilies, families and orders, all 

 under one great class. The grand fact of the natural sub- 

 ordination of organic beings in groups under groups, 

 which, from its familiarity, does not always 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 natu- 

 rally by a number of characters. We know, for instance. 



