A microcephalic youth of sixteen, a monorchid, developed what appeared at first to be an ordinary chorea subsequently to an orchidopexy. The movements, however, varied from day to day and from hour to hour. Sometimes they disappeared for days at a time, to reappear suddenly just when the neurosis seemed cured. The influence exerted on them by the will was both mild and transient. They constituted, in short, a particular kind of chorea, changing and changeable, and differing from intermittent chorea in that neither remissions nor relapses were ever wholly complete. Further, the condition was implanted on a basis of mental and physical degeneration, and seemed likely to become established as a permanent functional stigma. In another case a peculiar chorea gradually supervened, for no obvious reason, in an adult female of tardy and imperfect physical and intellectual development. It was difficult to decide whether the psychical or the somatic phenomena were preponderant; but to the material, tangible, and visible signs of constitutional inferiority was superadded a choreiform instability of the whole voluntary muscular system, consisting in agitation, gesticulation, and incorrigible motor restlessness, coupled with a conspicuous incapacity for rational action. The steps in the evolution of this functional defect were very slow, and coincided with final confirmation of the intellectual insufficiency. As for the chorea, its localisation and its intensity, its increase and its decrease, its extension and its limitation, seemed to vary, in a way that could not be foreseen, at the call of certain undetermined circumstances. In a third instance we meet with many of the symptoms already noted among those who tic: