MANY persons have volitional control of convergence; at the command, "Cross your eyes," they are able to do so with ease. Others cannot, but after a period of tutelage they acquire the faculty. A simple exercise to bring this about consists in having the subject regard a pencil at the punctum optimum and then hold his eyes in their assumed position by "imagining" the pencil after its withdrawal, demonstrating an obviously conscious influence. This control probably can be conditioned to occupy a subconscious level, since the position can be held in the face of distracting influences and the diversion of conscious thought. A patient described by Walsh1 had apparently developed great skill in the voluntary control of her convergence and in voluntary alternate suppression. A third group of persons is made up of those who seem quite unable to acquire volitional control of convergence. It has been demonstrated that