CHAPTER V.. Laws of Variation.

LAWS OF VARIATION. Effects of changed conditions—Use and disuse, combined with natural selection; organs of flight and of vision—Acclimatisation—Correlated variation—Compensation and economy of growth—False correlations—Multiple, rudimentary, and lowly organised structures variable—Parts developed in an unusual manner are highly variable; specific characters more variable than generic; secondary sexual characters variable—Species of the same genus vary in an analogous manner—Reversions to long-lost characters—Summary.