antimere

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A part or division in the body of a bilaterally or radially symmetric animal that corresponds to an opposite or similar part.

Century Dictionary and Cyclopedia

1. n. In biology, a segment or division of the body in the direction of one of the secondary or transverse axes, all of which are at right angles to the primary or longitudinal axis. When these axes are not differentiated in any way, all antimeres are alike, and are parts arranged around the long prime axis like the spokes and fellies of a wheel around the axis of the hub: a disposition preserved with much accuracy in many of the Radiata, among which, for example, the arms of a starfish, the tentacles of a sea-anemone or coral-animalcule, or the rows of ambulacra of a sea-urchin are antimeres. Oftener, however, the transverse axes are differentiated, some being shorter, others longer, giving rise to sides, as right and left, in the direction of the longer transverse axes, in which case right and left parts are antimeres. This constitutes bilateral symmetry. Parts which may be perceived to correspond at opposite poles of the other (shorter) transverse axes, constituting dorsabdominal symmetry, are also antimeres; but this condition is obscure. Likewise, again, parts along the primary longitudinal axis, or at its poles, which may be observed or be conceived to constitute anteroposterior symmetry, are essentially antimeric; but this condition, like dorsabdominal symmetry, is obscure, while the serial succession of like parts along the prime axis, as the rings of a worm, crustacean, or insect, and the double rings of a vertebrate, is so marked that antimeres of this kind are not called antimeres, but metameres; such are the ordinary segments, somites, arthromeres, or diarthromeres of any articulate or vertebrate animal. Antimere is therefore practically restricted to such radiating and bilateral parts as are more or less symmetrical with one another. See eudipleural.

Wiktionary

1. n. biology One of the two halves of bilaterally symmetrical animals; one of any opposite symmetrical or homotypic parts in animals and plants.

GNU Webster's 1913

1. n. (Biol.) One of the two halves of bilaterally symmetrical animals; one of any opposite symmetrical or homotypic parts in animals and plants.