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)