Yolk [OE. yolke, yelke, [yogh]olke, [yogh]elke, AS. geoloca, geoleca, fr. geolu yellow. See Yellow.] [Written also yelk.]
The yellow part of an egg; the vitellus.
An oily secretion which naturally covers the wool of sheep.
Yolk cord Zool., a slender cord or duct which connects the yolk glands with the egg chambers in certain insects, as in the aphids.
-- Yolk gland Zool., a special organ which secretes the yolk of the eggs in many turbellarians, and in some other invertebrates. See Illust. of Hermaphrodite in Appendix.
-- Yolk sack Anat., the umbilical vesicle. See under Umbilical.
© Webster 1913.