from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A kidneylike organ, being either part of the most anterior pair of three pairs of organs in a vertebrate embryo, disappearing early in the embryonic development of higher vertebrates, but functioning as a kidney in some simple vertebrates, such as the lamprey.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A primitive kidney in the lamprey and similar animals, and in other vertebrate embryos

from the GNU version of the Collaborative International Dictionary of English

  • n. The head kidney. See under head.

from The Century Dictionary and Cyclopedia

  • n. Same as pronephron.


pro-2 + Greek nephros, kidney.
(American Heritage® Dictionary of the English Language, Fourth Edition)



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