'That a perception initiated from corresponding retinal points is commonly referred without ambiguity to a single locus in visual space has often been regarded (Newton [note: 'Opticks, Quer. 112.'] Wollaston [note: Philosoph. Trans. London, 1824.'], Rohault [note: 'Physique, I. 31.'], Joh. Müller [note: 'Elements of Physiol. Vol. II. p. 1199, Baly's edit. 1843.'] as evidence of community of the nerve apparatus belonging to the paired retinal points. Their visual image appears single. Wollaston supposed the twin points attached to one and the same nerve-fibre, which bifurcated at the chiasma.' (53)