140 RESULTS Off THE ACTION OF [Chap. IV. 



So in the general economy of any land, the more widely 

 and perfectly the animals and plants are diversified for 

 different habits of life, so will a greater number of indi- 

 viduals be capable of there supporting themselves. A set 

 of animals, with their organisation but little diversified, 

 could hardly compete with a set more perfectly diversified 

 in structure. It may he doubted, for instance, whether the 

 Australian marsupials, which are divided into groups dif- 

 fering but little from each other, and feebly represent- 

 ing, as Mr. Waterhouse and others have remarked, our 

 carnivorous, ruminant, and rodent mammals, could suc- 

 cessfully compete with these well-developed orders. In 

 the Australian mammals, we see the process of diversifi- 

 cation in an early and incomplete stage of development. 



The Probable Effects of the Action of Natural Selection 

 through Divergence of Character and Extinction, on 

 the Descendants of a Common Ancestor. 



After the foregoing discussion, which has been much 

 compressed, we may assume that the modified descend- 

 ants of any one species will succeed so much the better 

 as they become more diversified in structure, and are 

 thus enabled to encroach on places occupied by other 

 beings. Now let us see how this principle of benefit 

 being derived from divergence of character, combined 

 with the principles of natural selection and of extinc- 

 tion, tends to act. 



The accompanying diagram will aid us in understand- 

 ing this rather perplexing subject. Let A to L represent 

 the species of a genus large in its own country; these 

 species are supposed to resemble each other in unequal 

 degrees, as is so generally the case in nature, and as is 



