The eyes begin to develop as a pair of diverticula from the lateral aspects of the forebrain. These diverticula make their appearance before the closure of the anterior end of the neural tube; after the closure of the tube they are known as the optic vesicles.
They project toward the sides of the head, and the peripheral part of each expands to form a hollow bulb, while the proximal part remains narrow and constitutes the optic stalk.
Additional images 
Head of chick embryo of about thirty-eight hours’ incubation, viewed from the ventral surface. X 26
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This article incorporates text from a public domain edition of Gray's Anatomy.