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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.

2. Zool.

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.