| n. | 1. | (Biol.) The contents or substance of the ovum; egg yolk. See Illust. of Ovum. |
| 2. | (Bot.) Perisperm in an early condition. |
| Noun | 1. | vitellus - nutritive material of an ovum stored for the nutrition of an embryo (especially the yellow mass of a bird or reptile egg) Synonyms: yolk |