Degeneration

Collier's New Encyclopedia (1921)

2026 Editor's Note: This page uses language about other peoples, religions, or nationalities that was commonplace when the book was published and is offensive by today's standards. The text has been left exactly as it was printed, rather than cut or softened, so that the historical record — including how ordinary such language once was — is preserved. (Ed: ET 2026-07-22) a biological term used to describe those not unfrequent cases where an entire organism falls below the structural level of its young stages, or where an organ in the same way loses its fullness of function, and becomes more or less atrophied, abortive, altitude of the same star is seen to and simplified. Thus many parasitic parasitic worms, crustaceans, etc., are emphatically simpler than their free - swimming larvæ, and the sensile adult Ascidian shows only traces of the vertebrate characters which are plain enough in the active young. Thus, too, a crustacean which starts with a well-developed eye, may exhibit the gradual loss of this on assuming a dark habitat. The term is best confined to cases where a level of structure exhibited during early life is more or less lost in the adult. Degeneration must be distinguished (a) from occasional abortion, (b) from reversion to an ancestral type, and (c) from the occurrence of rudimentary and undeveloped organs where a character possessed by ancestral types remains more or less undeveloped, or shows itself only in embryonic life. Degeneration may be due to the environment, or to cessation of function, or to some more subtle constitutional cause. The theory of the degeneration of man from a high state has been superseded by the belief in a development from low savagery.