What part of the corpora quadrigemina is clearly observed in a midsagittal section?

The superior colliculus

Explanation:

Superior colliculus is an organ in the midbrain and a multilayered sensory structure. It transform sensory signals into eye movement.

Superior colliculus is the part of the corporal quadrigemina that is clearly observed in a mid sagittal section ... it is clearly observed in transfered fissure backward of the mid brain and it is responsible for eye movement direction.