202 CLASSIFICATION. [Chap. XIV. 



CHAPTER XIV. 



Mutual Affinities of Oeganic Beings : Mor- 

 phology : Embryology : Rudimentary Organs. 



Classification, groups subordinate to groups — Natural system — 

 Rules aud 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 degrees, so that they can be classed in 

 groups under groups. This classification is not arbi- 

 trary 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 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 



