alternation

[In Sp. altern a cion; Port. altern ação; Ital. altern azione, from Lat. alternatio.] A. Ordinary Language: L. Gen. The succe ion of things to one another in a reciprocal order; interchange of things oftener than once with others, in time or in space. (a) In time : the alternation of day and night... -Lewis: Astron. of the Ancients, ch. 1., §3 "Slow alternations of land and sea."- Orcon: Cla i. of the Mammal i a, p. 55. (b) In space : "Each succe ive tide brings its charge of mixed powder, deposits its duplex layer day after day, and finally ma es of immense thickne are piled up, which, by preserving the alternations of sand and mica, tell the tale of their formation"-Tyndall: Frag. of Science, 3rd ed., p. 408. IL Specially : 1. Responses by the congregation in liturgical worship. "For such alternations as are there used must be by several persons; but the minister and the people cannot so sever their interests as to sustain several persons, he being the only mouth of the whole body which he presents."- Milton : Apology for Smectymnuus . 2. Alternate performances between the two divisions of a choir. B. Technically : 1. Biol. or Zool. Alternation of Generations: The rendering of a scientific term used by Prof. Steen str up to expre an abnormal kind of generation, called by Prof. Owen Meta genesis. It implies that one kind of birth takes place in one generation, and another in the next; the third is again like the first, and the fourth resembles the second. In the first generation there is the ordinary propagation of the race by impregnation; in the second, immature animals, which appear as if they had not pa ed beyond the larval state, give birth to young. This feature in the case Prof. Owen calls Parthenogenesis (q.v.). By the curious arrangement now mentioned, the young do not resemble their immediate parents, but their grand-parents; as in due time what may be termed their grandchildren will resemble them. The best known instance of alternation 172 of generations is in the Aphides. [APHIS.] (Steen str up: Alternation of Generations, Ray Society . Owen : Invert. Anim ., 2nd ed., pp. 667, 668.) 2. Alg .: Alternations are the same as what are more generally called permutations.