[The ultrastructure of embryonic capillaries in the neuroepithelium of the brain vesicles].

The electronmicroscopic control of the capillaries of the brain vesicles in 5--6-day-old chick embryos revealed an intimate contact between capillary walls and neuroblasts, and on the other hand the presence of a functional endoplasmic reticulum in the endothelial cells. These are only very few vacuoles for protein transport in the cytoplasm of endothelial cells.