Chap. XIII. CLASSIFICATION. 411 



CHAPTER XIII. 



Mutual Affinities of Organic Beings : Morphology : 

 Embryology : Rudimentary 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. 



Feom the first dawn of life, all organic beings are found 

 to resemble each other in descending degrees, so that 

 they can be classed in groups under groups. Tins classi- 

 fication is evidently not arbitrary like the grouping of 

 the stars in constellations. The existence of groups 

 would have been of simple signification, if one group had 

 been exclusively fitted to inhabit the land, and another 

 the water ; one to feed on flesh, another on vegetable 

 matter, and so on ; but the case is widely different in 

 nature ; for it is notorious how commonly members of 

 even the same sub-group have different habits. In 

 our second and fourth chapters, on Variation and on 

 Natural Selection, I have attempted to show that it is 

 the widely ranging, the much diffused and common, that 

 is the dominant species belonging to the larger genera, 

 which vary most. The varieties, or incipient species, 

 thus produced ultimately become converted, as I believe, 

 into new and distinct species ; and these, on the principle 

 of inheritance, tend to produce other new and dominant 



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