150 EESULTS OF THE ACTION OP [Chap. IV. 



struggle for existence, it will chiefly act on those which 

 already have some advantage ; and the largeness of any 

 group shows that its species have inherited from a 

 common ancestor some advantage in common. Hence, 

 the struggle for the production of new and modified 

 descendants will mainly lie between the larger groups 

 which are all trying to increase in number. One large 

 group will slowly conquer another large group, reduce 

 its numbers, and thus lessen its chance of further varia- 

 tion and improvement. Within the same large group, 

 the later and more highly perfected sub-groups, from 

 branching out and seizing on many new places in the 

 polity of Nature, will constantly tend to supplant and 

 destroy the earlier and less improved sub-groups. Small 

 and broken groups and sub-groups will finally disappear. 

 Looking to the future, we can predict that the groups 

 of organic beings which are now large and triumphant, 

 and which are least broken up, that is, which have as 

 yet suffered least extinction, will, for a long period, 

 continue to increase. But which groups will ultimately 

 prevail, no man can predict ; for we know that many 

 groups, formerly most extensively developed, have now 

 become extinct. Looking still more remotely to the 

 future, we may predict that, owing to the continued and 

 steady increase of the larger groups, a multitude of smaller 

 groups will become utterly extinct, and leave no modified 

 descendants ; and consequently that, of the species living 

 at any one period, extremely few will transmit descen- 

 dants to a remote futurity. I shall have to return to this 

 subject in the chapter on Classification, but I may add 

 that as, according to this view, extremely few of the 

 more ancient species have transmitted descendants 

 to the present day, and, as all the descendants of the 



