[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.]

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