1. It is enclosed by the delicate hyaloid membrane.

2. The hyaloid membrane attaches to the retina all around its front edge.

3. Gamma-irradiation (600 rads) of newly born rabbits and cats decreases the number of migrating amebocytes in their vitreous; 24 h later, however, they are replaced by monocytes from the hyaloid vessels.

4. From the very beginning of fetal development, another ameboid-type cell of mesenchymal origin makes its entrance into the vitreous through the hyaloid vessels; these monocyte-like cells differentiate into hyalocytes and populate a well-defined area of the cortical vitreous close to the retina and to the ora serrata.