As the application of the present day interpretation of Radium (that it is an element undergoing spontaneous disintegration) is not confined to the physical sciences, but has a wide and general bearing upon our whole outlook on Nature, Mr. Soddy has presented the subject in non-technical language, so that the ideas involved are within reach of the lay reader. No effort has been spared to get to the root of the matter and to secure accuracy, so that the book should prove serviceable to other fields of science and investigation, as well as to the general public. +27.—Criminal Man.+ According to the Classification of CESARE LOMBROSO. Briefly Summarized by his Daughter, Gina Lombroso Ferrero. With 36 Illustrations and a Bibliography of Lombroso's Publications on the Subject. Crown 8vo. Net, $2.00. Signora Guglielmo Ferrero's résumé of her father's work on criminal anthropology is specially dedicated to all those whose office it is to correct, reform, and punish the criminal, with a view to diminishing the injury caused to society by his anti-social acts; also to superintendents, teachers, and those engaged in rescuing orphans and children of vicious habits, as a guide in checking the development of evil germs and eliminating incorrigible subjects whose example is a source of corruption to others. * * * * * The most valuable production since Darwin's "Origin of Species." The Nature of Man _Studies in Optimistic Philosophy_ By Élie Metchnikoff Sub-Director of the Pasteur Institute, Paris Translated with an Introduction by P. Chambers Mitchell Secretary of the Zoölogical Society Octavo. Illustrated. Popular Edition. $1.50 net. By mail, $1.65 It is not often that a scientific book may be read with ease, profit, and pleasure by the general reader, so that M. Metchnikoff's book comes in the nature of an agreeable surprise. It is marked by a refreshing _naïveté_ and a large simplicity which are characteristically Russian. The scientific importance of this work is so great that it is spoken of in England as the most valuable production since Darwin's _Origin of Species_. Opinions of the Press "An extremely interesting and typical book.... With a distinguished frankness, M. Metchnikoff defines his attitude to our universal prepossessions. It is his theory that the infirmities of age are to be overcome. If there be ground for this conception, humanity is to be profoundly changed and what we call life now, will be the childhood and youth of that longer and larger life."—H. G. WELLS, in _London Speaker_. "Undoubtedly a great book (in some quarters it has been hailed as the greatest since Darwin's famous message to the world) and should be read by all intelligent men and women."—_The Nation._