THE KEGENERATION OF LOST PAETS IN ANIMALS. obliged to have recourse, as is too often the case, to the report of the patient. Visual hallucination is only developed hi the acute states. I invite specialists who may have occasion to observe cases of hallucination of sight either in hospital or in private practice to seize the opportunity of repeating these experiments. After having carefully determined the nature of the malady, of which the hallucination is a symptom, the nature of the imaginary object and its position, the doubling by ocular pressure might be tried. If the attempt succeeds, it is more than probable that the other experiments (prism, spy-glass, mirror, &c.), would also succeed, for they are all connected like a series of theorems. But it does not seem that every hallucination can be doubled by ocular pressure. Negative results should therefore be recorded as carefully as positive results, because equally interesting. More especially, I am inclined to think that unilateral hallucinations and those which move with the movement of the eye do not admit of being doubled, approximated, reflected, &c. I shall be happy to receive communications on this subject (addressed to 44, Eue St. Placide, Paris). THE REGENERATION OF LOST PARTS IN ANIMALS. By D'AECY W. THOMPSON, B.A., Trinity College, Cambridge. The question of the Eeproduction of Lost Parts is interesting from several points of view in biology ; and many new facts have lately been added to our knowledge of it, which bear closely on the philosophical side of the question. They seem to me to have an important bearing on such speculations as Mr. J. S. Haldane's, who makes use of the phenomena of regeneration of lost parts in his recent article on " Life and Mechanism," in MIND XXXIII., as he has done elsewhere before. 1 And if they do not remove the difficulties that Mr. Haldane brings prominently forward, they at least seem to push them back to another stage. Before dealing with Mr. Haldane's position, it will be well to review briefly the facts of the case. In last century, when Trembley showed that the piece of a divided and subdivided Hydra grew again into perfect hydrae, such a proceeding seemed wholly new and extraordinary, and excited the intensest curiosity. It was said to upset all previous notions of the ' individuality ' of the organism. Crowned heads grew interested, ambassadors sought for the animal, and state- couriers carried it through Europe. 1 Essays in Philosophical Criticism, -p. 54: "Relation of Philosophy to Science ".
