The results of Professor Groos's original and acute investigations are of peculiar value to those who are interested in psychology and sociology, and they are of great importance to educators. He presents the anthropological aspects of the subject treated in his psychological study of the Play of Animals, which has already become a classic. Professor Groos, who agrees with the followers of Weismann, develops the great importance of the child's play as tending to strengthen his inheritance in the acquisition of adaptations to his environment. The influence of play on character, and its relation to education, are suggestively indicated. The playful manifestations affecting the child himself and those affecting his relations to others have been carefully classified, and the reader is led from the simpler exercises of the sensory apparatus through a variety of divisions to inner imitations and social play. The biological, aesthetic, ethical, and pedagogical standpoints receive much attention from the investigator. While this book is an illuminating contribution to scientific literature, it is of eminently practical value. Its illustrations and lessons will be studied and applied by educators, and the importance of this original presentation of a most fertile subject will be appreciated by parents as well as by those who are interested as general students of sociological and psychological themes. D. APPLETON AND COMPANY, NEW YORK. D. APPLETON AND COMPANY'S PUBLICATIONS. RICHARD A. PROCTOR'S WORKS. _OTHER WORLDS THAN OURS: The Plurality of Worlds, Studied under the Light of Recent Scientific Researches._ With Illustrations, some colored. 12mo. Cloth, $1.75. CONTENTS.--Introduction.--What the Earth teaches us.--What we learn from the Sun.--The Inferior Planets.--Mars, the Miniature of our Earth.--Jupiter, the Giant of the Solar System.--Saturn, the Ringed World.--Uranus and Neptune, the Arctic Planets.--The Moon and other Satellites.--Meteors and Comets: their Office in the Solar System.--Other Suns than Ours.--Of Minor Stars, and of the Distribution of Stars in Space.--The Nebulae: are they External Galaxies?--Supervision and Control. _OUR PLACE AMONG INFINITIES._ A Series of Essays contrasting our Little Abode in Space and Time with the Infinities around us. To which are added Essays on the Jewish Sabbath and Astrology. 12mo. Cloth, $1.75. CONTENTS.--Past and Future of the Earth.--Seeming Wastes in Nature.--New Theory of Life in other Worlds.--A Missing Comet.--The Lost Comet and its Meteor Train.--Jupiter.--Saturn and its System.--A Giant Sun.--The Star Depths.--Star Gauging.--Saturn and the Sabbath of the Jews.--Thoughts on Astrology. _THE EXPANSE OF HEAVEN._ A Series of Essays on the Wonders of the Firmament. 12mo. Cloth, $2.00.