Si vero fuerit in aestate vitellus avi semper superponatur.    From Wordnik.com.  [Gilbertus Anglicus Medicine of the Thirteenth Century] Reference

"The ovarian eggs of all animals are identical, small cells with vitellus, germinal vesicle and germinal spot.".    From Wordnik.com.  [Facts and Arguments for Darwin] Reference

This constitutes the vitelline circulation (Fig. 459), and by means of it nutriment is absorbed from the yolk (vitellus.) 5.    From Wordnik.com.  [V. Angiology. 3. Development of the Vascular System] Reference

"The ovarian eggs of all animals are perfectly identical, small cells with a vitellus, germinal vesicle and germinal spot" (paragraph 278).    From Wordnik.com.  [Facts and Arguments for Darwin] Reference

Until recently it was regarded as a general rule that, by the partial segmentation of the vitellus a germinal disc was formed, and in this, corresponding to the ventral surface of the embryo, a primitive band.    From Wordnik.com.  [Facts and Arguments for Darwin] Reference

Insects are identical, small animals with head, thorax, and abdomen; that is to say if, only noticing what is common to them, we leave out of consideration the difference of their development, the presence or absence and the multifarious structure of the vitelline membrane, the varying composition of the vitellus, the different number and formation of the germinal spots, etc.    From Wordnik.com.  [Facts and Arguments for Darwin] Reference

"Thus, in Fishes, the first changes consist in the segmentation of the vitellus and the formation of a germ, processes which are common to all classes of animals.    From Wordnik.com.  [Facts and Arguments for Darwin] Reference