n. [ OE. yolke, yelke, &yogh_;olke, &yogh_;elke, AS. geoloca, geoleca, fr. geolu yellow. See Yellow. ] [ Written also yelk. ] [ 1913 Webster ]
1. The yellow part of an egg; the vitellus. [ 1913 Webster ]
2. (Zool.) An oily secretion which naturally covers the wool of sheep. [ 1913 Webster ]
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 Unbilical. [ 1913 Webster ]