metamerism

1. A type of anatomic structure exhibiting serially homologous metameres; in primitive forms, such as the annelids, the metameres are almost alike in structure; in vertebrates, specialization in the cephalic region masks the underlying m., which is still clearly evident in serially repeated vertebrae, ribs, intercostal muscles, and spinal nerves, and in young vertebrate embryos. 2. In chemistry, rarely used synonym for structural isomerism.

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me·tam·er·ism mə-'tam-ə-.riz-əm n

1) isomerism esp. of chemical compounds of the same type

2) the condition of having or the stage of evolutionary development characterized by a body made up of metamers that is usu. held to be an essential prelude to the differentiation of the more highly organized animals (as arthropods and vertebrates) through the disproportionate development and elaboration of some segments together with the coalescence, reduction, or loss of others

3) the phenomenon exhibited by pairs of color metamers <the problem of \metamerism in matching artificial with natural teeth>

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me·tam·er·ism (mə-tamґər-is″əm) 1. isomerism, particularly a type of structural isomerism in which different radicals of the same chemical type are attached to the same polyvalent element and yet give rise to compounds possessing identical molecular formulas, for example, diethylamine, (C₂H₅)₂NH, and methyl propylamine, CH₃NHC₃H₇. 2. arrangement into metameres by the serial repetition of a structural pattern.