CLASSIFICATION 451 



tend to go on increasing 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 char- 

 acter. 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 natural- 

 isation. 



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 ex- 

 plained, 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 subordi- 

 nate 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 always suffi- 

 ciently 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, 



