n., pl., al·lan·to·i·des (ăl'ən-tō'ĭ-dēz').
A membranous sac that develops from the posterior part of the alimentary canal in the embryos of mammals, birds, and reptiles. It is important in the formation of the umbilical cord and placenta in mammals. Also called allantoid.
[New Latin, from allantoīdes, from Greek allantoeidēs, sausage-shaped : allas, allant-, sausage + -oeidēs, -oid.]
allantoic al'lan·to'ic (ăl'ən-tō'ĭk) adj.
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.
