FOR ALMOST a century the superior colliculi have been considered as important structures in oculomotor functions. This concept originated in 1870 when Adamiik observed conjugate eye movements upon electric stimulation of the tectum.1It was then that the hypothesis of a gaze "center" was introduced and remained unchallenged until Bernheimer2and Ferrier and Turner3reported their observations on the effects of ablation of the tectum. They found that lesions of the superior colliculi did not alter eye movements, throwing doubt on the essential nature of these structures for oculomotor functions. Thus, the ablation experiments marked the beginning of numerous controversies on the role of the superior colliculi in ocular deviations. Some of the questions raised by various investigators have been the following: (1) Are the superior colliculi the subcortical "centers" for conjugate eye movements in all directions? (2) Are they the "centers" for vertical eye movements?