The yolk of an egg or ovum.→ vitelli
- ‘In no case, when comparing embryos from the same uterus, was the presence of vitellus found in only part of the embryos observed; neither was it found in small quantities.’
- ‘If eggs of Echinarachnius be inseminated with thin sperm suspension they throw off membranes that are fully formed and equidistant from the surface of the vitellus in from two to three minutes.’
- ‘With a center core, the darker core areas appear like fish egg vitellus and crustacean inner organs.’
- ‘Fish eggs can be round with the hook passed through or half round with the egg vitellus in the form of colored yarn waving out the flat side along the shaft of the hook.’
Early 18th century: from Latin, literally yolk.