Chap. XIV.] CLASSIFICATION. 



CHAPTER XIV. 



Mutual Affinities of Organic Beings : Morphology : 

 Embryology : Eudimentary Organs. 



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 

 classification — Analogical or adaptive characters — Affinities, general, 

 complex, and radiating — Extinction separates and defines groups — 

 Morphology, 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 like the grouping of the stars in 

 constellations. The existence of groups would have been of simple 

 significance, if one group had been exclusively fitted to inhabit the 

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

 table 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, belonging 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 principle 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 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 character. This latter conclusion 



