\ˌmez-ə-ˈnef-rəs, ˌmēz-, ˌmēs-, ˌmes-, -ˌräs\
: either member of the second and midmost of the three paired vertebrate renal organs that functions in adult fishes and amphibians but functions only in the embryo of reptiles, birds, and mammals in which it is replaced by a metanephros in the adult—called also Wolffian body; compare pronephros
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