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. 



From the first dawn of life, all organic beings are round 

 to resemble each other in descending degrees, so that 

 they can be classed in groups under groups. This 

 classification is evidently not arbitrary like tne group- 

 ing 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 Variatioi 

 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 



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