164 THE ORIGIN OF SPECIES 



iuhabitants of the same region is, in fact, the same as 

 that of the physiological division of labor in tlie organs 

 of the same individual body — a subject so well elucidated 

 by Milne Edwards. No pliysiologist doubts that a stom- 

 ach adapted to digest vegetable matter alone, or flesh 

 alone, draws most nutriment from these substances. _So 

 in^ the general econorny of any land, the more widely and 

 perfectly the animals and plants are diversified for differ- 

 ent habits of life, so will a greater number of individuals 

 be capable of there supporting themselves. A set of 

 animals, with their organization but little diversified, 

 could hardly compete with a set more perfectly diversi- 

 fied in structure. It may be doubted, for instance, 

 whether the Australian marsupials, which are divided 

 into groups differing but little from each other, and 

 feebly representing, as Mr. Waterhouse and others have 

 remarked, our carnivorous, luminant, and rodent mam- 

 mals, could successfully compete with these well-developed 

 orders. In the Australian mammals, we see the procesp. 

 of diversification in an early and incomplete stage oi 

 development. 



Tfie Probable Effects of the Action of Natural Selection, 



through Divergence of Character and Extinction^ on 



the Descendants of a Cormnon Ancestor 



After the foregoing discussion, which has been much 

 compressed, we may assume that the modified descendants 

 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 



