I 



' CHAPTER XIV 



Mutual Affinities of Organic Beings: Morphology — Embryology 

 — Rudimentary Organs 



I 



Classification, Groups Subordinate to Groups — ^Natural System — Rules and 

 Difficulties in Classification, explained on the Theory of Descent with 

 Modification — Classification of Varieties — Descent always used in Classi- 

 fication — ^Analogical or Adaptive Characters — ^Affinities, General, Com- 

 plex, and Radiating — Extinction separates and defines Groups — ^Mor- 

 phology, between Members of the Same Class, between Parts of the 

 Same Individual — Embryology, Laws of, explained by Variations not 

 supervening at an Early Age, and being inherited at a Corresponding 

 Age — Rudimentary Organs, their Origin explained — Summary. 



CLASSIFICATION 



From the most remote period in the history of the world, organic 

 beings have been found to resemble each other in descending de- 

 grees, so that they can be classed in groups under groups. This 

 classification is not arbitrary Hke the grouping of the stars in 

 constellations. The existence of groups would have been of sim- 

 ple significance, if one group had been exclusively fitted to in- 

 habit the land, and another the water; one to feed on flesh, an- 

 other on vegetable matter, and so on; but the case is widely 

 different, for it is notorious how commonly members of even the 

 same sub-group have different habits. In the second and fourth 

 chapters, on Variation and on Natural Selection, I have attempted 

 to show that within each country it is the widely ranging, the 

 much diffused and common, that is the dominant species, belong- 

 ing to the larger genera in each class, which vary most. The 

 varieties, or incipient species, thus produced, ultimately become 

 converted into new and distinct species; and these, on the prin- 

 ciple of inheritance, tend to produce other new and dominant 

 species. Consequently the groups which are now large, and which 

 generally include many dominant species, tend to go on increas- 

 ing 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 con- 

 stantly tend to diverge in character. This latter conclusion is sup- 



371 



