The instruments which we have called chromomictors, have been designed for the purpose of mixing lights of different colours for experiments in physiological optics. There are already a considerable number of instruments for this purpose, but none of them are perfectly satisfactory. We shall here describe one or two new forms of apparatus which have been recently experimented with, and though they may not be suitable for many colour experiments, yet they seem to possess some advantages over several of the instruments now in use.