Chap. XIII.

CLASSIFICATION.

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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 ofdescent with modification — Classification of varieties — Descentalways used in classification—Analogical or adaptive characters— Affinities, general, complex: and radiating — Extinction separates and defines groups — Morphology, between membersof the same class, between parts of the same individual —Embryology, laws of, explained by variations not superveningat an early age, and being inherited at a corresponding age—Rudimentary organs ; their origin explained — Summary.

Erom the first dawn of life, all organic beings are foundto resemble each other in descending degrees, so thatthey can be classed in groups under groups. This classi-fication is evidently not arbitrary like the grouping ofthe stars in constellations. The existence of groupswould have been of simple signification, if one group hadbeen exclusively fitted to inhabit the land, and anotherthe water; one to feed on flesh, another on vegetablematter, and so on; but the case is widely different innature; for it is notorious how commonly members ofeven the same sub-group have different habits. In thesecond and fourth chapters, on Variation and on XaturalSelection, I have attempted to show that within eachcountry it is the widely ranging, the much diffused andcommon, that is the dominant species belonging to thelarger genera in each class, which vary most. Thevarieties, or incipient species, thus produced, ultimatelybecome converted, as I believe, into new and distinctspecies ; and these, on the principle of inheritance, tend