The application of our knowledge of hypnotism to the explanation of alleged supernormal and unusual sensibilities is particularly interesting to the "psychical researcher"; the general enlargement of our knowledge of these conditions, irrespective of such an application, represents the aim of the psychologist. The latter may indeed cite Mr. Lang's dictum that "science is only concerned with truth, not with the mischievous inferences which people may draw from truth," as an excuse for his own declination to coöperate in the correction of such mischievous inferences. But the civic conscience of the psychologist may convince him that the removal of error is often an indispensable requisite to the dissemination of truth. The study of the subconscious or the subliminal consciousness, of multiple personality, of mental automatisms, of involuntary actions, of induced visualizations, of sporadic hallucinations, may be cited as further illustrations of topics interesting to the "psychical researcher" for their bearings upon the apparent transcendence of the normal, and to the psychologist for illustrations of important groups of mental processes and relations. I must refer to the general literature for descriptions of these several phenomena; the subtle connection between one hypnotic condition and the next, bridging over a period of normal consciousness with complete forgetfulness of the hypnotic consciousness; the still more subtle evidence for the latency of impressions thus revivable by an appeal to the subconscious; the elaboration, in trance experiences, of these nether world phenomena into organized personalities, which in the remarkable case reported by Professor Flournoy expanded from a personification of Marie Antoinette to that of a Martian revisiting Mars, describing Martian scenery and customs, and writing in Martian language, and again to the reincarnation of a Hindu princess of four centuries ago; the affiliation of these cases to those of spontaneous loss of personality in actual life, like that of the Rev. Ansel Bourne, related by Professor James; the automatic writings performed by hypnotic subjects and by persons in normal conditions; the power to induce visions by "crystal gazing," and auditory hallucinations by "shell-hearing"; the census of hallucinations, together with the very important series of observations relative to the psychology of deception,--these represent the more truly psychological contributions of psychologists and "psychical researchers" to their common domain.