due to association, to a connection between sight and hearing set up in childhood and continued into adult life; but the evidence points to some inborn connection in the nervous system; coloured hearing tends strongly to run in families. Moreover, we know of no natural or normal association of colours with tones, although the attempt has often been made to illustrate music by colours; the recent colour-scoring of the Russian composer Scriabin is, for instance, nothing more than an idiosyncrasy, and will make no general or permanent appeal to the musical public. There are many other kinds of synæsthesia, besides this connection of sight and sound; and we have no reason to think that every instance is to be explained in just the same way; in all cases, however, we have a particular sensation uniformly accompanied by another, which we may call either a secondary sensation or an image of sensory character. Coming back to the normal life, we have next to note the part played in certain minds by =habitual images=. Just as, in Wagner’s operas, the performer comes upon the stage to the accompaniment of some characteristic musical phrase, some ‘motive,’ as it is called, which recurs again and again as he enters and reenters to take his share of the action, so in minds of the imaginal type such general notions as ‘virtue’ and ‘commerce’ and ‘summer’ may regularly call up mental pictures, little groups of images, which illustrate or characterise the notions: thus, virtue may be pictured mentally by the flash of a human figure, standing very upright. These pictures are usually incomplete, mere impressionist sketches; but they may remain unchanged for years. Finally, we come to the images which enter into our ideas of memory and of imagination. We discuss these ideas later; here we need only say that the psychological distinction between sensation and image, if it is to be drawn at all, must be drawn between sensation and the =free images of memory and imagination=, and cannot be drawn earlier. Some psychologists believe that a memory-image can always be distinguished from a sensation, that the two processes differ in their intrinsic nature. It is difficult to put the question to the test of experiment; but what evidence we have seems to look the other way. We shall do best to suspend judgement.